Assessment of electrode coupling for tissue ablation

(Cross-reference of related applications) This application claims the benefit of US Provisional Patent Application No. 60 / 748,234 filed on December 6, 2005, which is incorporated herein by reference. This application is also filed at the same time as this application with international application reference numbers 0B-047801WO, 0B-047809US, 0B-047810US, 0B-047812US, 0B-047813US, 0B-047814US and 0B-047815US ( It is also related to "international application"). These international applications are incorporated herein by reference.

(Technical field) The present invention relates to an electrode catheter and a method of using the electrode catheter for tissue resection. In particular, the electrode catheter of the present invention may include a circuit for evaluating electrode-tissue contact and electrical coupling for applying excision energy (eg, RF energy) to the target tissue.

It is well known that benefits can be gained if damage can be formed in the tissue and the depth and location of the damage being formed can be controlled. In particular, it may be desirable to raise the tissue temperature to about 50 ° C (which alters the electrical properties of the tissue) until the damage is formed through coagulative necrosis. For example, unwanted atrial fibrillation can be reduced or eliminated by forming the injury at a specific location in the heart tissue via coagulative necrosis.

However, some existing excision electrodes may face some problems when trying to form damage in a particular location using them. One such issue faced with existing excision electrodes is how to ensure proper tissue contact and electrical coupling. Electrode-tissue contact is not easily determined by using conventional techniques such as perspective. Instead, physicians use electrode catheters to establish electrode-tissue contact based on their own experience. Such experience can only be gained over time and can be rapidly lost if the physician does not use electrode catheters on a regular basis. In addition, when forming damage to the heart, the heartbeat further complicates the situation and establishes sufficient contact pressure between the electrodes and tissue at a time long enough to form the desired damage. And it becomes difficult to maintain. If the contact between the electrode and the tissue cannot be maintained properly, it is likely that high quality damage will not be formed. Similarly, information about the electrical coupling between the electrode and the target tissue is not readily available in advance to determine how much excision energy may be absorbed in the tissue during excision. Instead, physicians use generalized, pre-determined resection parameters, such as power and duration, based on their own experience in performing resection procedures with electrode catheters. Such experience can lead to defects, inefficiencies and complications such as improper damage formation, premature high impedance blockade, tissue carbonization and thrombus formation.

<p> It is desirable to be able to evaluate electrode-tissue contact and electrical coupling for electrode catheters used in tissue resection procedures. Radio frequency (RF) excision energy is primarily resistance heating at a typical operating frequency of about 500 kHz, but at lower frequencies there is capacitance in the patient's blood and tissue. The combined effects of resistance and capacitance at the blood-tissue interface can be measured (eg, as impedance) to automatically assess various contact conditions between the electrode and the target tissue.</p><p> An exemplary electrode catheter system may include electrodes configured to apply electrical energy. A measurement circuit configured to measure impedance may be mounted between the electrode and ground as the electrode approaches the target tissue. Processors or processing units may be implemented to determine contact with the target tissue, at least in part, based on the reactance of the impedance measured by the measurement circuit. In another embodiment, the contact state may be based on the phase angle of the impedance.</p><p> An exemplary electrode catheter system may include electrodes configured to apply electrical energy. A measurement circuit configured to measure impedance may be mounted between the electrode and ground as the electrode approaches the target tissue. At least in part, the processor or processing unit may be implemented to determine the electrical coupling to the target tissue based on the reactance of the impedance measured by the measurement circuit. In another embodiment, the electrical coupling state may be based on the phase angle of the impedance.</p><p> An exemplary method of assessing electrode-tissue contact for tissue resection is to measure the impedance between the electrode and ground as the electrode approaches the target tissue and to separate the reactance component from the measured impedance. And, at least in part, to indicate the state of contact with the target tissue based on the reactance component.</p><p> An exemplary method for assessing electrode-tissue electrical coupling for tissue excision is to measure the impedance between the electrode and ground as the electrode approaches the target tissue and separate the reactance component from the measured impedance. It may include, at least in part, showing the state of electrical binding to the target tissue based on the reactance component.</p><p> Another exemplary method of assessing electrode-tissue contact for tissue resection is to directly measure the phase angle between the electrode and ground as the electrode approaches the target tissue, and at least in part. It may include indicating the state of contact with the target tissue based on.</p><p> Another exemplary method of assessing electrode-tissue electrical coupling for tissue resection is to directly measure the phase angle between the electrode and ground as the electrode approaches the target tissue, and at least in part. It may include indicating the state of electrical coupling to the target tissue based on the phase angle.</p><p> The contact state may be communicated to the user (eg, a doctor or technician), eg, on a display or other interface. The user can then use the contact state as feedback to properly position the electrode catheter on the target tissue at the desired contact level for the excision procedure. For example, the user may increase contact if the contact state indicates inadequate contact. Alternatively, for example, the user may reduce the contact if the contact condition indicates excessive contact.</p><p> The electrical coupling state may be communicated to the user (eg, a doctor or technician), eg, in a display or other interface. The user can then use the electrical binding state as feedback to properly position the electrode catheter on the target tissue at the desired binding level for the excision procedure. For example, the user may increase the bond if the bond state indicates an inadequate bond . Alternatively, for example, the user may reduce the binding if the binding state indicates excessive binding.</p><p> It should also be noted that in exemplary embodiments, a current source (or otherwise a voltage source) may be used to manage electrical energy. This source may be the same source used for the excision procedure and used to "ping" during electrode positioning, or it may be a source provided separately. May be good. In either case, a constant current source (or constant voltage source) may be used. Alternatively, it may be a variable current source (or variable voltage source), such as an excision source that operates in a mode adaptable to tissue temperature. In addition, multiple current sources (or voltage sources) may be used. The plurality of current sources (or voltage sources) may operate in either simultaneous mode, continuous mode, or temporary overlapping mode.</p><p> There are a number of additional aspects of the invention. Each of the first to seventh aspects of the present invention may be utilized to evaluate the bond between the electrode and the tissue (hereinafter, may be referred to as "electrode bond"). This electrode bond may be in the form of a mechanical bond between the electrode and the tissue, or in other words, in a state where there is physical contact between the electrode and the tissue. In another embodiment, this electrode coupling is a form of electrical coupling between the electrode and the tissue. The electrical coupling may be referred to as a state in which a sufficient amount of electrical energy is transferred from the electrodes to the tissue. It should also be understood that there may be one or more "degrees" of electrode coupling and that one or more benchmarks related to a particular degree of electrode coupling may be determined by the tissue. is there.</p><p> The first aspect of the present invention is embodied by a medical system / method of performing a medical procedure on a tissue. The first electrode may be arranged at a fixed position with respect to the tissue, or a first electric signal may be sent to the first electrode. The phase angle associated with the provision of this first electrical signal to the first electrode is used to evaluate the coupling between the first electrode and the tissue (electrode coupling). More specifically, such phase angles may be compared to at least one other phase angle value to assess the coupling between the electrode and the tissue.</p><p> There are various improvements to the features mentioned in connection with the first aspect of the invention. Further features may be incorporated into the first aspect of the present invention as well. These improvements and additional features may be present individually or in any combination. First, the features described below in relation to the fifth aspect may be incorporated into this first aspect.</p><p> At least one phase angle benchmark value may be provided for the phase angle comparison according to the first aspect. In one embodiment, the phase angle benchmark value is stored in a data structure or accessible by a phase angle comparator or the like. In one embodiment, the phase angle benchmark value is associated with an inadequate coupling state. In another embodiment, the phase angle benchmark value is associated with an elevated or excessively coupled state.</p><p> In one embodiment of the first aspect, one or more categories or ranges may be provided for phase angle comparisons to evaluate electrode coupling. Any suitable number of phase angle categories or ranges may be used, and these phase angle categories or ranges may be determined or set in any suitable way (eg, experimentally). For example, 1) the first range may include phase angles associated with inadequate coupling states, such as a phase angle comparator, where the phase angle associated with the first electrical signal is within this first range. It may be used to determine whether or not, and 2) the second range may include phase angles related to a sufficient coupling state, which the phase angle comparator or the like relates to the first electrical signal. It may be used to determine whether the phase angle to be used is within this second range, and 3) the third range may include a phase angle associated with a highly coupled or excessively coupled state. They may be used by a phase angle comparator or the like to determine whether or not the phase angle related to the first electric signal is within this third range. Each of these first, second and third ranges can be used individually to compare the phase angle associated with the first electrical signal, or can be used in appropriate coupling with each other. Good. What is "insufficient," "sufficient," and "high / excessive" can be determined by the tissue attached to the first electrode, along with one or more other factors. Should be understood.</p><p> The phase angle associated with the first electrical signal at a point in time of the medical procedure may be determined according to the first aspect at this point in time in any suitable way and for the purpose of assessing electrode coupling. Of course, it may be desirable to evaluate the electrode coupling based on some predetermined time or according to some predefined function (eg, every "x" seconds during at least part of the medical procedure. 1 Evaluate the phase angle associated with the electrical signal). In one embodiment, the phase angle associated with the first electrical signal is between the current provided to the first electrode and the voltage present between the first electrode and another electrode, such as the return electrode. The phase angle.</p><p> The second aspect of the present invention is embodied by a medical system / method of performing a medical procedure on a tissue. The first electrode may be arranged at a fixed position with respect to the tissue, or a first electric signal may be sent to the first electrode. The reactance associated with the provision of this first electrical signal to the first electrode is used to evaluate the coupling between the first electrode and the tissue (electrode coupling). More specifically, such reactance may be compared to at least one other reactance value to assess the bond between the electrode and the tissue.</p><p> There are various improvements to the features mentioned in connection with the second aspect of the invention. Further features may be incorporated into the second aspect of the present invention as well. These improvements and additional features may be present individually or in any combination. First, the features described below in relation to the fifth aspect may be incorporated into this second aspect.</p><p> At least the reactance benchmark value may be provided for the reactance comparison according to the second aspect. In one embodiment, this reactance benchmark value is stored in a data structure or accessible by a reactance comparator or the like. In one embodiment, the reactance benchmark value is associated with an inadequate coupling state. In another embodiment, the reactance benchmark value is associated with a high or excessively coupled state.</p><p> In one embodiment of the second aspect, one or more categories or ranges may be provided for reactance comparisons that evaluate electrode coupling. Any suitable number of reactance categories or ranges may be used, and these reactance categories or ranges may be determined or set in any suitable method (eg, experimentally). For example, 1) the first range may include reactance values related to insufficient coupling states, and whether or not the reactances related to the first electric signal are within this first range by a reactance comparator or the like. 2) The second range may include reactance values related to a sufficient coupling state, which may be used by a reactance comparator or the like to determine the reactance related to the first electrical signal. It may be used to determine if it is within this second range, 3) the third range may contain reactance values associated with high or excessively coupled states, which are reactance comparators. Etc. may be used to determine whether the reactance associated with the first electrical signal is within this third range. Each of these first, second and third ranges can be used individually to compare the reactance associated with the first electrical signal, or may be used in appropriate coupling with each other. .. What is "insufficient," "sufficient," and "high / excessive" can be determined by the tissue attached to the first electrode, along with one or more other factors. Should be understood.</p><p> The reactance associated with the first electrical signal at a point in time of the medical procedure may be determined by the second aspect at this point in time in any suitable way and for the purpose of assessing electrode coupling. Of course, it may be desirable to evaluate the electrode coupling based on some predetermined time or according to some predefined function (eg, every "x" seconds during at least part of the medical procedure. 1 Evaluate the reactance associated with the electrical signal). In one embodiment, the reactance associated with the first electrical signal is the reactance associated with the electrical path between the first electrode and another electrode such as the return electrode.</p><p> A third aspect of the present invention is embodied by a medical system / method of performing a medical procedure on a tissue. The first electrode may be arranged at a fixed position with respect to the tissue, or a first electric signal may be sent to the first electrode. The coupling between the first electrode and the tissue (electrode coupling) is evaluated using what can be characterized as the impedance component ratio associated with the provision of this first electrical signal to the first electrode. This "impedance component ratio" is the ratio of two component values (eg, resistance, reactance, impedance) that define the impedance associated with the provision of the first electrical signal. More specifically, such impedance component ratios may be compared to at least one other impedance component ratio value to assess the coupling between the electrode and the tissue.</p><p> A fourth aspect of the present invention is embodied by a medical system / method of performing a medical procedure on a tissue. The first electrode may be arranged at a fixed position with respect to the tissue, or a first electric signal may be sent to the first electrode. The development of high-coupling or over-coupling conditions (eg, mechanical, electrical, or both) can be identified through appropriate evaluation.</p><p> There are various improvements to the features mentioned in connection with the fourth aspect of the invention. Further features may be incorporated into the fourth aspect of the present invention as well. These improvements and additional features may be present individually or in any combination. First, the features described below in relation to the fifth aspect may be incorporated into this fourth aspect.</p><p> Impedance, phase angle (eg, according to the first aspect), reactance (eg, the first aspect) without limitation for the purpose of identifying the presence of a high or excessive coupling state between the first electrode and the tissue in the case of the fourth aspect. One or more parameters may be monitored / evaluated, including the target frequency (according to the second aspect) and the target frequency (eg, according to the seventh aspect described below). Whether there is an excessive coupling state by comparing the reactance (for example, part of the electrical circuit that extends from the first electrode through the patient's body to the return electrode) with at least one reactance benchmark value. You may decide. In one embodiment, a high or excessive reactance state corresponds to a state in which the reactance is below a predetermined negative reactance value. Highly coupled or excessive by comparing the phase angle (eg, the phase angle between the current at the first electrode and the voltage between the first electrode and the return electrode) with at least one phase angle benchmark value. It may be determined whether or not there is a binding state. In one embodiment, a highly coupled or excessively coupled state corresponds to a state in which the phase angle is below a predetermined negative phase angle value.</p><p> Targets the frequency with respect to the first electrical signal, where the phase angle is a constant preset value (eg, the phase angle between the current at the first electrode and the voltage between the first and return electrodes). It may be called "frequency", and for the purpose of this fourth aspect, comparing this target frequency with at least one frequency benchmark value determines whether there is a high or excessive coupling state. You may. In one embodiment, a highly coupled or excessively coupled state shall correspond to having a target frequency above a predetermined frequency value. The frequency for the first electrical signal, where the inductance (for example, part of the electrical circuit that extends from the first electrode through the patient's body through the patient's body to the return electrode) is a constant preset value, also determines the target frequency. It may be defined and the presence of high or excessive coupling states may be determined by comparing this target frequency with at least one frequency benchmark value. In one embodiment, a highly coupled or excessively coupled state shall correspond to having a target frequency above a predetermined frequency value. In general, a suitable electrical parameter may be related to the target frequency, and any suitable value may be used for this electrical parameter for the purpose of the target frequency. Frequencies above the target frequency may be associated with a condition, and frequencies below the target frequency may be associated with a condition, or both.</p><p> A fifth aspect of the present invention is embodied by a medical system / method of performing a medical procedure on a tissue. The first electrode may be placed at a fixed position with respect to the tissue, or a first electrical signal that provides a first current may be sent to the first electrode. This first current is used to perform a first medical procedure (eg, excision of heart tissue). This first current is also used to evaluate the bond between the first electrode and the tissue.</p><p> There are various improvements to the features mentioned in connection with the fifth aspect of the invention. Further features may be incorporated into the fifth aspect of the present invention as well. These improvements and additional features may be present individually or in any combination. The bond between the first electrode and the tissue in the fifth aspect may be evaluated with any suitable parameter. This evaluation may be based on impedance comparisons, phase angle comparisons (eg, according to the first aspect), reactance comparisons (eg, according to the second aspect) and target frequency comparisons (eg, according to the seventh aspect below).</p><p> In the case of the fifth aspect, a second electric signal that provides a second current may be sent to the first electrode. The bond between the first electrode and the tissue may be evaluated using this second signal. Various characterizations may be made in relation to the second electrical signal, which may be applied individually or in any combination. 1) The second current can be less than the first current, 2) the first and second electrical signals can be at least generally the same frequency, and 3) the first and second signals are It may be delivered in a manner other than sequential or simultaneous, for example by switching from one power source to another. With respect to the latter, the switch may be placed in one position to interconnect the first electrode with the first power source (eg, the evaluation power source), or the electrode coupling may be evaluated using the first electrode coupling evaluation module. Good. By arranging this switch in a different position, the first electrode may be interconnected with a second power source (eg, cut power supply), or the electrode coupling may be evaluated using a second electrode coupling evaluation module. .. The first electrode coupling evaluation module and the second electrode coupling evaluation module may have a common configuration.</p><p> A sixth aspect of the present invention is embodied by a medical system / method of performing a medical procedure on a tissue. In one embodiment, a first catheter with a first electrode is placed in a first cavity (eg, left atrium) of the patient's heart with a second catheter with a second electrode. In another embodiment, a first electrode tip and a second electrode tip (eg, associated with a common catheter, associated with different catheters) are placed within the first cavity of the heart. In each case, a first electrical signal may be sent to the first electrode to perform the first medical procedure, and the bond between the first electrode and the tissue is evaluated using this first electrical signal. You may.</p><p> There are various improvements to the features mentioned in connection with the sixth aspect of the invention. Further features may be incorporated into the sixth aspect of the present invention as well. These improvements and additional features may be present individually or in any combination. The bond between the first electrode and the tissue in the sixth aspect may be evaluated with any suitable parameter. This evaluation may be based on impedance comparisons, phase angle comparisons (eg, according to the first aspect), reactance comparisons (eg, according to the second aspect) and target frequency comparisons (eg, according to the seventh aspect below). Furthermore, the features described above in relation to the fifth aspect may be incorporated into this sixth aspect.</p><p> A seventh aspect of the present invention is embodied by a medical system / method of performing a medical procedure on a tissue. The first electrode may be arranged at a fixed position with respect to the tissue, or a first electric signal may be sent to the first electrode. By analyzing one or more frequencies, it is possible to identify frequencies for which the electrical parameter has a constant value (where "value" includes a certain range of values).</p><p> There are various improvements to the features mentioned in connection with the seventh aspect of the invention. Further features may be incorporated into the seventh aspect of the present invention as well. These improvements and additional features may be present individually or in any combination. The target frequency is a frequency with a zero phase angle (for example, the phase angle between the current provided to the first electrode and the voltage existing between the first electrode and another electrode such as the return electrode). It may be provided. Zero frequency may also be the case to provide zero frequency inductance (eg, the inductance of a portion of an electrical circuit that extends from the first electrode through the patient's body to the return electrode). Any electrical parameter may be used for the purpose of the target frequency, and this electrical parameter may be any suitable value for the purpose of the target frequency. In one embodiment, the target frequency sequentially provides multiple electrical signals at different frequencies (eg, using frequency sweep) to determine which of these electrical signals produces the required value of electrical parameters. Identified by. In another embodiment, an electrical signal containing a plurality of frequencies is sent to the first electrode. Using a filter, each of the various frequencies from this common electrical signal is analyzed separately to determine whether any of these frequencies will produce the required electrical parameters. It may be possible.</p><p> The target frequency may be used to evaluate the bond between the first electrode and the tissue in the case of the seventh aspect. In this regard, at least one frequency benchmark value may be provided for frequency comparison according to the seventh aspect of assessing electrode coupling. In one embodiment, this frequency benchmark value is stored in a data structure or accessible by a frequency comparator or the like. In one embodiment, the frequency benchmark value is associated with an inadequate coupling state. In another embodiment, the frequency benchmark value is associated with a highly coupled or excessively coupled state.</p><p> In one embodiment of the seventh aspect, one or more categories or ranges may be provided for frequency comparison to evaluate electrode coupling. Any suitable number of frequency categories or ranges may be used, and these frequency categories or ranges may be determined or set in any suitable way (eg, experimentally). For example, 1) the first range may include frequencies associated with inadequate coupling states, which frequency comparators and the like may use to determine if the target frequency is within this first range. 2) The second range may include frequencies related to a sufficient coupling state, so that a frequency comparator or the like can determine whether or not the target frequency is within this second range. 3) The third range may include frequencies related to the highly coupled or excessively coupled state, and a frequency comparator or the like may use them to determine whether the target frequency is within this third range. It may be used to determine the frequency. Each of these first, second and third ranges can be used individually for comparison with the target frequency, or may be used in appropriate combination with each other. What is "insufficient," "sufficient," and "high / excessive" can be determined by the tissue attached to the first electrode, along with one or more other factors. Should be understood.</p><p> There are a number of features and the like applicable to each of the first to seventh aspects, which are summarized here. The first electrode may be of any suitable size, shape, configuration and / or type, and the first electrode may be used to perform any type of medical procedure (eg excision). In one embodiment, the first electrode is in the form of a catheter electrode.</p><p> In the case of the first aspect to the seventh aspect, the first electric signal may have any suitable frequency. In one embodiment, and except in the case of the seventh aspect, a single frequency may be sufficient for the purpose of providing electrode coupling evaluation. The first electrical signal or any other electrical signal may be provided using any suitable power source or signal generator. Each of such power supplies or signal generators may be continuously interconnected to the first electrode or electrically interconnected as required / needed through the operation of a switch or the like.</p><p> In the cases of the first to seventh aspects, the return electrode may be used in combination with the first electrode to perform a medical procedure using the first electrode, which is also used for electrode coupling evaluation. May be good. The following features associated with such return electrodes may be used individually or in any suitable combination. 1) Each of the first electrode and the return electrode may be in the form of a catheter electrode, each of such catheter electrodes may be independently movable, and 2) the return electrode is wider than the first electrode. The surface area may be utilized, and 3) each of the first electrode and the return electrode may be placed in a common cavity of the heart such as the left atrium.</p><p> Any electrode coupling evaluation used by the first to seventh aspects may utilize at least one electrode coupling evaluation module (eg, an electrical circuit). Each of such electrode coupling evaluation modules may be incorporated in any suitable method and in any suitable position. For example, the electrode coupling evaluation module may be incorporated into a catheter, in the form of a stand-alone unit, by a power generator, by an electrophysiological mapping system, or by an electrophysiological signal recording system. ..</p><p> Each of the first to seventh aspects may be used to identify the presence of a highly bound or overbound state. The ability to identify the presence of such high or excessive binding states may be desirable for a number of reasons. For example, it may be desirable to avoid high or excessive binding conditions (eg, to reduce the likelihood of perforating tissue walls or membranes). It may also be desirable to reach a high or excessively bound state (eg, to increase the likelihood of passing the first electrode through the tissue wall or membrane).</p><p> Any phase angle comparison used by the first to seventh aspects may utilize a phase shift circuit to facilitate the measurement / determination of the phase angle. For example, the phase of the current signal provided to the first electrode may be shifted by an appropriate amount (for example, 90 °). It may also be desirable to compensate for the remaining phase shifts for the purpose of any electrode coupling evaluation based on phase angle comparison. That is, if there should be no phase difference in the actual situation, it may be shown that a phase shift exists for the electrode coupling evaluation.</p><p> The results of any electrode coupling evaluation used by the first to seventh aspects may be output to one or more positions by any suitable method. This output may be in one or more forms of visual feedback, audible feedback or physical feedback. For example, a bar graph or other display may be used to visually convey the degree of electrode coupling. It may be desirable to scale / amplify the output of the electrode coupling evaluation.</p><p> The above-mentioned aspects, features, details, usefulness and advantages of the present invention as well as other aspects, features, details, usefulness and advantages shall be discussed in the context of the following description and claims and in the accompanying drawings. It will be clear from.</p>

Illustrative embodiments of tissue excision systems and methods used to evaluate electrode-tissue contact and electrical coupling are shown in the drawings. As described below, the tissue resection system of the present invention offers a number of advantages, including, for example, the ability to apply a reasonable amount of resection energy to the target tissue while alleviating electrode-tissue contact and coupling problems. The present invention also facilitates enhanced tissue contact and electrical coupling in a variety of environments (eg, during damage formation on the surface inside a beating heart).

FIG. 1 is a schematic representation of an exemplary electrode catheter system 10 that can be implemented to assess electrode-tissue contact during a tissue resection procedure for patient 12. The catheter system 10 may include an electrode catheter 14, which can be inserted inside the patient 12, eg, to form a resection injury inside the patient's heart 16. During an exemplary resection procedure, a user (eg, a patient's doctor or technician) inserts an electrode catheter 14 into one of the patient's blood vessels 18, eg, through the foot (as shown in Figure 1) or the patient's neck. You may. The user is guided by a real-time fluoroscopic imaging device (not shown) to move the electrode catheter 14 to the patient's heart 16 (as shown in more detail in FIG. 1a).

When the electrode catheter 14 reaches the patient's heart 16, the electrode 20 at the tip of the electrode catheter 14 is mounted to electrically map the myocardium 22 (ie, the muscular tissue of the heart wall) and locate the target tissue 24. You may. After locating the target tissue 24, the user must move the electrode catheter 14 into contact with the target tissue 24 and electrically connect the catheter electrode 14 to the target tissue 24, followed by excision. Apply energy to form one or more excision injuries. Electrode-tissue contact refers to a condition in which the catheter electrode 14 physically contacts the target tissue 24, thereby resulting in a mechanical bond between the catheter electrode 14 and the target tissue 24. Electrical coupling refers to the condition in which a sufficient portion of electrical energy extends from the catheter electrode 14 to the target tissue 24 so that excision can be efficiently formed during excision. For target tissues with similar electrical and mechanical properties, the electrical coupling involves mechanical contact. That is, mechanical contact is part of the electrical coupling. This allows the catheter electrodes to be substantially electrically attached to the target tissue without mechanical contact, but not vice versa. In other words, the catheter electrodes are also electrically coupled when in mechanical contact. However, the range or sensitivity of electrical coupling varies with different electrical properties of the tissue. For example, the extent of electrical binding to conductive myocardial tissue differs from that of the vessel wall. Similarly, the extent or sensitivity of electrical coupling also changes with different mechanical properties of the tissue, such as tissue compliance. For example, the extent of electrical coupling to the relatively compliant, smooth atrial wall is different from the relatively non-compliant comb-shaped myocardial tissue. The level of contact and electrical coupling is often important for forming sufficiently deep excision damage in the target tissue 24 without damaging the tissue surrounding the heart 16. The catheter system 10 is measured for impedance at the electrode-tissue interface and between the electrode catheter 14 and the target tissue 24, as will be described in more detail later.

FIG. 2a shows an exemplary level of electrical contact or coupling between the electrode catheter 14 and the target tissue 24. FIG. 2b shows an exemplary level of mechanical contact or binding between the electrode catheter 14 and the target tissue 24. Illustrative levels of contact or coupling are indicated by "slight contact or no contact" as indicated by contact state 30a, "light to intermediate contact" as indicated by contact state 30b, and contact state 30c. There can be such a "firm contact". In an exemplary embodiment, the catheter system 10 is implemented to display or otherwise output the contact state to the user, for example as shown in the optical arrays 31a-31c corresponding to the contact states 30a-30c, respectively. You may.

There can be a contact state 30a (slight contact or no contact) before the electrode catheter 14 comes into contact with the target tissue 24. Inadequate contact may not result in proper damage formation when the electrode catheter 14 is operated to apply excision energy. However, contact condition 30c (rigid contact) can form too deep damage (eg, perforate the myocardium 22) and / or destroy the tissue surrounding the target tissue 24. Therefore, the user may desire a contact state of 30b (light contact to intermediate contact).

It should be noted that the exemplary contact or coupling states 30a-30c in FIGS. 2a and 2b are for illustrative purposes only and are not intended to be limiting. Other contact or coupling states (eg, more subdivided between contact states) may also be present and / or may be desired by the user. The definition of such contact state may be determined, at least to some extent, by operating conditions such as the type of target tissue, the desired depth of excision damage, and the operating frequency of RF radiation, to name a few.

FIG. 3 is a high-level functional block diagram showing the catheter system 10 in more detail so that it can be implemented to assess contact or coupling status with respect to the electrode catheter 14. Note that some of the components typical of traditional tissue resection systems are shown in simplified form in Figure 1 for brevity and / or not shown at all. However, such components may be provided as part of or for use with the catheter system 10. For example, the electrode catheter 14 may include a handle, a fluoroscopic imager and / or various other controls, to name a few. Such components are well understood in medical device technology and therefore no further description is needed here for a complete understanding of the present invention.

An exemplary catheter system 10 includes a generator 40, such as a radio frequency (RF) generator, and a measuring circuit 42, which is electrically connected to the electrode catheter 14 (as indicated by a wire 44 to the electrode catheter). It may be. The electrode catheter 14 may be electrically grounded, for example, through a grounding patch 46 (as shown in FIG. 1) attached to the patient's arm or chest.

The generator 40 may be operated to emit electrical energy (eg, RF current) near the tip of the electrode catheter 14. Although the present invention is described herein with respect to RF currents, it should be noted that other types of current energy may be used to evaluate contact conditions.

In an exemplary embodiment, the generator 40 emits a so-called "pinging" (eg, low) frequency as the electrode catheter 14 approaches the target tissue 24. The "pinging" frequency may be emitted by the same electrode catheter used to apply excision energy for injury formation. Alternatively, a separate electrode catheter may be used to apply the "pinging" frequency. In such an embodiment, the separate electrodes may be in close contact (or attached) to the electrode for applying excision energy, thereby bringing the contact or coupling state to the electrode applying excision energy. Can be confirmed.

The resulting impedance at the electrode-tissue interface may be measured using the measurement circuit 42 during contact or coupling evaluation (or pinging). In an exemplary embodiment, the measurement circuit 42 may be a conventionally available resistance, capacitance, inductance (RCL) meter. Another exemplary measurement circuit that can be implemented to determine the phase angle component will also be described in more detail later with reference to FIG. Yet another measurement circuit 42 may be implemented and the invention is not limited to use with measurement circuits of any particular type or configuration.

The reactance and / or phase angle component of the impedance measurement may be used to determine the contact or coupling state. The contact or bond state may then be communicated to the user in real time to achieve the desired level of contact or bond for the excision procedure. For example, the contact or coupling state may be displayed to the user on the optical array (eg, as shown in Figures 2a and 2b).

After the user successfully guides the electrode catheter 14 to the desired contact or coupling state with the target tissue 24, the generator, such as the generator 40 or the second generator, is resected and injured in the target tissue 24. It may be operated to generate excision (eg, high frequency) energy to form. In an exemplary embodiment, the same generator 40 is used to generate electrical energy at a variety of frequencies, including both frequencies for impedance measurements (eg, "pinging" frequencies) and frequencies for forming excision injuries. You may. However, in alternative embodiments, separate generators or generator units may be implemented without departing from the scope of the invention.

In an exemplary embodiment, the measurement circuit 42 may be operationally associated with the processor 50 and the memory 52 to analyze the measured impedance. As an example, the processor 50 may determine the reactance and / or phase angle component of the impedance measurement and, based on the reactance component and / or phase angle, determine the corresponding contact or coupling state to the electrode catheter 14. You may. In an exemplary embodiment, contact or coupling states corresponding to different reactances and / or phase angles may be pre-determined during testing at different frequencies, eg, for any of a wide range of tissue types. The contact or join state may be stored in memory 52, for example as a table or other suitable data structure. The processor 50 may then access the table in memory 42 to determine the contact or coupling state corresponding to the impedance measurement based on the reactance component and / or the phase angle. The contact or coupling state may be output to the user, for example, on the display device 54.

Note that the catheter system 10 is not limited to use with the processor 50 and the memory 52. In other embodiments, analog circuits may be implemented to evaluate the contact state based on impedance measurements and to output the corresponding contact state. Such circuits can be readily provided by those skilled in the art of electronics after familiarity with the disclosure herein, and therefore no further description is needed.

It should also be noted that the display device 54 is not limited to any particular type of device. For example, the display device 54 may be a computer monitor such as a liquid crystal display (LCD). Alternatively, the display device may be implemented as an optical array, in which one or more light emitting diodes (LEDs) are driven to indicate contact (eg, contact) in the optical array. Shines). In practice, any suitable output device may be implemented to indicate contact to the user, not limited to the display device. For example, the contact state may be output to the user as a voice signal or tactile feedback (eg, vibration) on the handle of the electrode catheter.

Furthermore, it should be noted that the components of the catheter system 10 do not have to be provided in the same housing. As an example, the measurement circuit 42 and / or the processor 50 and the memory 52 may be provided on the handle portion of the electrode catheter 14. In another example, at least a portion of the measurement circuit 42 may be provided elsewhere (eg, at the tip) of the electrode catheter 14. Yet another example provides the processor 50, memory 52 and display 54 as separate computing devices, such as a personal desktop or laptop computer that may be operationally associated with other components of the catheter system 10. You may.

Assessing the contact or coupling state between the electrode catheter 14 and the target tissue 24 based on impedance measurements at the electrode-tissue interface can be better understood with reference to FIGS. 4 and 4a. FIG. 4 is a model of an electrode catheter 14 that contacts (or binds to) the target tissue 24. The electrode catheter 14 is electrically connected to a generator 40 (eg, an RF generator). In an exemplary embodiment, the circuit may be completed through the target tissue 24, which is a reference such as a grounding patch 46 (FIG. 1) of the patient's body where the current passes through the blood, myocardium and other organs. Indicates that it flows to the electrode.

As mentioned above, the generator 40 may be operated to generate the electrical energy released by the electrode catheter 14. The release is indicated by arrow 60 in FIG. Also, as mentioned above, the generator 40 may emit a "pinging" frequency as the electrode catheter 14 approaches the target tissue 24 to assess electrode-tissue contact or binding. In an exemplary embodiment, this "pinging" frequency may be chosen so that non-inducible, capacitive and resistance effects other than those at the blood-tissue interface do not have a recognizable effect on impedance measurements. Good.

In exemplary applications, volumetric effects at blood and electrode-blood interfaces (eg, between metal electrode catheters and blood) have been found to be minimal or even absent at frequencies above about 50 kHz. The effects of stray inductance (eg, due to relatively thin catheter wires), capacitance and resistance, and capacitance of other organs (eg lungs) at the electrode interface are also minimal or even absent at frequencies above about 50 kHz. I also understood.

Furthermore, it was found that the resistance effect was remarkably noticeable at the blood-tissue interface at frequencies below 50 kHz. This is because the current flows into the target tissue 24 mainly through the interstitial fluid space 23, and the cell membrane 25 (eg, bi-lipid or "fat") acts as an insulator. However, at frequencies above about 50 kHz, the cell membrane 25 becomes conductive and current penetrates the target tissue 24 through both the interstitial fluid space 23 and the cell membrane 25. Therefore, the cell membrane acts as a "capacitor" and the resistance effect is reduced at frequencies above about 50 kHz.

It may be desirable to use a small amount of current and power to avoid the risk of forming excision damage during contact or bond evaluation. The currently preferred range for currents below 1 mA is an operating frequency in the 50-500 kHz range.

Frequency selection is within the recognition of those skilled in the art, primarily based on biological and engineering aspects. In the biological aspect, lower frequencies can result in measurement errors due to the electrode-electrolyte interface. Parasitic capacitance can be significant as frequencies rise above the MHz range. However, it should be noted that the present invention is not limited to use in any particular frequency or frequency range. Frequency may depend, at least to some extent, on operational considerations such as application, type of target tissue, and type of electrical energy used, to name a few.

Assuming that the desired frequency is selected for a particular application, the model shown in FIG. 4 can be further represented as a simplified electrical circuit 62 as shown in FIG. 4a. In circuit 62, the generator 40 is represented as an AC source 64. As mentioned above, at low frequency operations that may be used to assess electrode-tissue contact, capacitance and resistance at the blood-tissue interface dominate the impedance measurements. Therefore, other capacitance, induction and resistance effects may be ignored and the capacitance / resistance effect at the blood / tissue interface may be represented in circuit 62 by the resistor / capacitor (RC) circuit 66.

The RC circuit 66 may include a resistor 70 representing a resistance effect and a capacitance effect on the impedance of the target tissue 24 and a resistor 68 representing a resistance effect on the impedance of blood in parallel with the capacitor 72. If the electrode catheter 14 makes no or little contact with the target tissue 24, the blood resistance effect affects the RC circuit 66 and therefore also the impedance measurements. However, when the electrode catheter 14 moves and comes into contact with the target tissue 24, the resistance and capacitance effects of the target tissue 24 affect the RC circuit 66, so impedance measurements also affect it.

The effects of resistance and capacitance on impedance measurements can be better understood in relation to the definition of impedance. Impedance (Z) can be expressed as follows. Z = R + jX Where R is the resistance from blood and / or tissue, j is an imaginary number indicating that the term has a phase angle of + 90 °, and X is the reactance from both capacitance and inductance. is there.

From the above equation, it is observed that the magnitude of the reactance component responds to both the resistance effect and the capacitance effect of the circuit 62. This deformation corresponds directly to the level of contact or bond at the electrode-tissue interface and may therefore be used to assess electrode-tissue contact or bond. As an example, when the electrode catheter 14 operates at a frequency of 100 kHz and is primarily in contact with blood, the impedance is purely resistant and the reactance (X) is close to 0 ohms. When the electrode catheter 14 comes into contact with the target tissue, the reactance component becomes negative. As the level of contact or bond increases, the reactance component becomes even more negative.

Alternatively, the contact or coupling state may be determined based on the phase angle. In practice, it may be preferable to determine the contact or coupling state based on the phase angle in some applications, because the phase angle is expressed as a trigonometric ratio between reactance and resistance. The magnitude of the resistance component can vary as conditions change (eg for different patients), but the phase angle is a relative measurement that tends to be less sensitive to external conditions.

In an exemplary embodiment, the phase angle may be determined from impedance measurements (eg, by processor 50 in FIG. 3). That is, the impedance may be expressed as follows. Z = | Z | φ Here, | Z | is the magnitude of impedance, and φ is the phase angle.

The terms | Z | and φ may be further expressed as:

<maths num="1"><img file="JP5162467B2_D0001.tif" /></maths>and tanφ = X / R

The phase angle also corresponds directly to the level of contact or bond at the electrode-tissue interface and may therefore be used to assess electrode-tissue contact or bond. As an example, when the electrode catheter 14 operates at a frequency of 100 kHz and is primarily in contact with blood, the phase angle is close to zero (0). When the electrode catheter 14 comes into contact with the target tissue, the phase angle becomes negative, and as the contact or coupling level increases, the phase angle becomes more negative. An example is shown in Table 1 for the purpose of illustration.

<tables num="1"><img file="JP5162467B2_D0002.tif" /></tables>

Although the impedance measurement value may be used to determine the phase angle, in the alternative embodiment, the measurement circuit 42 may be implemented as a phase detection circuit for directly determining the phase angle. FIG. 5 shows an exemplary phase detection circuit 80. The phase detector circuit 80 is shown and described in relation to its functional components. It should be noted that no specific hardware configuration is required to fully understand the present invention. The implementation of the phase detector circuit 80 in digital and / or analog hardware and / or software will be readily apparent to those skilled in the art of electronics after familiarity with the teachings herein.

The exemplary phase detection circuit 80 may include a current sensor 82 and a voltage sensor 84 that measure current and voltage at the electrode-tissue interface. The current and voltage measurements may be inputs to the phase comparator 86. The phase comparator 86 provides a direct current (DC) output voltage that is proportional to the phase difference between the voltage and current measurements.

In one embodiment, the current sensor 82 may be used to measure the cut current. The sensor may be in series with the cutting wire. For example, a CST1 current sensing transformer from Coilcraft may be placed in series with the cutting wire. Alternatively, the current wire may penetrate the hole in the current sensor with or without a physical connection. In addition, the voltage between the cut electrode and the ground patch may be detected. This voltage may be attenuated so that it can be supplied to the phase detection circuit. The phase detector circuit then measures the current and voltage and determines the phase angle between them, which is later correlated with the coupling level. Thus, the cut current can be used to measure the phase angle rather than applying additional current for coupling detection purposes.

Optionally, the phase shifter 86 may be facilitated by "correcting" the phase shift delay between the measured current and the measured voltage by shifting the current measurement by the phase shift circuit 88. .. Alternatively, the output from the phase comparator 86 may be "corrected" by the phase adjuster circuit 90 to compensate for external factors such as the type of ground patch 46 used. A signal scaling circuit 92 that amplifies the output (eg, millivolts to volt) for use by various devices (eg, processor 50 and display 54 in FIG. 3) may be provided.

During excision, the measured impedance and its component resistance and reactance vary with tissue temperature. In such conditions, changes due to changes in tissue temperature provide a measure of injury formation during excision.

It should be noted that the phase detection circuit 80 shown in FIG. 5 is provided as an example and is not intended to be limiting. Those skilled in the art of electronics can readily provide other embodiments without departing from the scope of the invention after being familiar with the disclosures herein.

An exemplary system for electrode contact evaluation has been described, but here the exemplary operating modes can be better understood with reference to the block diagrams shown in FIGS. 6-8. FIG. 6 is an exemplary block diagram 100 showing a phase angle measurement for detecting contact or coupling. FIG. 7 is an exemplary block 200 diagram showing a phase angle measurement during excision when both excision energy and contact detection signals are applied simultaneously to the excision electrode. FIG. 8 is an exemplary block diagram 300 showing a phase angle measurement during excision that switches between the detection signal and the excision power. Figures 7 and 8 may use reference numbers in the 200s and 300s, respectively, to indicate similar elements, and these elements may not be repeated in relation to Figures 7 and 8, respectively. There is sex.

As mentioned above, the phase angle methods for detecting contact or coupling are: (1) the tissue is more resistant and capacitive than blood, and (2) the measured electrode impedance is largely dependent on the direct surrounding material. Based on the fact. Therefore, when the electrode moves from the blood to the myocardium, the measured impedance increases and the phase angle changes from 0 ° to a negative value (capacitive). Since the phase angle is a relative term for both resistance and reactance, it may be used to represent the contact or coupling level. That is, when the electrode is in contact with blood, it provides a 0 ° baseline and becomes more negative as more contacts or bonds are established. It also minimizes the effects of catheters, instruments and physiologically variable elements.

The phase angle measurement may be performed by sampling both the load voltage (V) 102 and the current (I) 104 and calculating the delay between those signals as the phase angle. As shown in FIG. 6, the detection signal 106 is applied between the excision electrode 108 and the reference electrode 110. The detection signal 106 may be, for example, between 50 kHz and 500 kHz with a small amplitude (&lt;1 mA).

An exemplary instrument may be operated at frequencies of, for example, 100 kHz, 400 kHz and 485 kHz, depending on the reference electrode configuration. Both current 104 and voltage 102 are detected. These two signals are sent to the phase comparator 112, and the phase angle corresponding to the contact or coupling state of the electrode 108 is calculated. The adjustment of the raw phase angle signal at block 114 compensates for external effects on the phase angle caused by, for example, catheters, instruments and biovariable elements. It is also tuned for easy interpretation and interface and then output at block 116 to other equipment for display or other processing.

Phase compensation may be performed at the beginning of the excision procedure. First, the catheter electrode 108 is moved to the center of the heart chamber (eg, right or left atrium) so that it only contacts the blood. The system measures the phase angle and uses this value as the baseline for the zero contact level. This adjustment compensates for the fixed phase angle provided by the catheter and the patient, such as catheter wiring, reference electrode location, and skin or fat if an external patch is used.

After initial zero adjustment, the user may move the catheter electrode to one or more desired sites to remove the arrhythmic myocardium. In an exemplary embodiment, the phase angle begins to change as the electrode 108 approaches, for example, within 3 mm of the myocardium, and becomes more and more negative as contact or coupling is established. The user may determine the quality of electrode contact or coupling based on the phase angle output before applying cutting energy. In an exemplary embodiment, this phase angle value is about -3 ° when the 4 mm excision electrode actually contacts the myocardium. It should be noted that there are at least two methods of measuring the phase angle during excision, as described in more detail here in connection with FIGS. 7 and 8.

In FIG. 7, while the cutting power 218 is applied to the electrode 208, the detection signal 206 is similarly applied. Ablation and contact detection operate at different frequencies. Therefore, filtering allows the phase angle to be measured during resection without interfering with resection of the myocardium.

Another option is to switch the phase measurement between the detection signal 306 and the cut power 318, as shown by switch 320 in FIG. When the cut power 318 is turned off during approach, the low amplitude detection signal 306 is turned on and used to measure the phase angle for detecting contact or coupling. When the excision power 318 is turned on for the excision procedure, the high amplitude excision power 318 voltage and current are detected and used as contact or coupling indicators during excision.

FIG. 9a shows an embodiment of the electrode coupling evaluation protocol 400 (evaluation protocol 400), which can be used to make any suitable electrode (eg, catheter electrode) if the evaluation is based on phase angle. Can be evaluated for binding to various tissues. Therefore, Protocol 400 may be used in connection with the embodiments described above in connection with FIGS. 6-8. In either case, the "bond" may include an electrical bond of the electrode to the target tissue, a mechanical bond between the electrode and the target tissue, or both.

Step 402 of the evaluation protocol 400 of FIG. 9a relates to delivering an electrical signal to the electrodes. This is usually done after the electrodes have been placed at least generally in close proximity to the target tissue (eg, in a heart chamber such as the left atrium). Then, the phase angle is determined in step 404, and then the electrode coupling is evaluated based on this phase angle in step 408. The electrode coupling evaluation from step 408 may be classified by performing step 410. However, the classification of step 410 is not always necessary in all cases. In either case, the evaluation result from step 408 is output according to step 412.

The electrical signal transmitted according to step 402 of Protocol 400 may be of any suitable frequency. However, only a single frequency is required to make an evaluation for the purposes of Protocol 400. The phase angle associated with step 404 may be the phase angle of the impedance. This phase angle may be determined by any suitable method using, for example, a phase detection circuit having any suitable configuration. In one embodiment, and using the electrical signal associated with step 402, the current of one electrode is measured, the voltage between one electrode (eg, a return electrode) is measured, and then these current measurements are taken. The phase angle is determined by determining the phase angle between the voltage measurement value and the voltage measurement value. Another option is to measure / determine the reactance and impedance in a suitable way, and then determine the phase angle from these values (for example, the sine of the phase angle is the ratio of the reactance to the impedance). Is.

The phase angle may be determined using an RCL meter or a phase detector circuit (eg, having an oscillator, multiplexer, filter, phase detector circuit), which may be referred to as a phase module. By incorporating or embedding this physiology module (measurement and / or detection) into or embedding in the catheter handle set, by incorporating or embedding it in the power supply, by forming a stand-alone unit between the excision catheter and the power supply. It may be placed at any suitable location, such as by incorporating it into an electrophysiology or EP mapping system, or by making it part of an electrophysiology recording system.

Evaluation of the bond of the electrode to the tissue (Protocol 400 step 408) may be performed by any suitable method. For example, the phase angle determined through step 404 may be compared to one or more benchmark phase angle values (eg, using a phase angle comparator). These benchmark phase angle values may be determined / set experimentally, for example, by any suitable method. These benchmark phase angle values may be stored in an appropriate data structure, for example, in a computer-readable data storage medium, or may be made available to a phase angle comparator. Generally, and in one embodiment, the phase angle decreases as the electrodes / tissues (eg, myocardium) bind.

For the purpose of classifying step 410 of evaluation protocol 400 in Figure 9a, there is one or more benchmark phase angle values (eg, a single benchmark phase angle value or) for one or more of the following states: There may be a range benchmark phase angle value). That is, 1) insufficient electrode coupling (for example, an electrode coupling in which the related phase angle below "A" corresponds to insufficient electrode coupling), 2) sufficient electrode coupling (for example, the related phase angle is Electrode couplings above "A" and below "B" are considered to correspond to sufficient electrode couplings) and 3) High or excessive electrode couplings (eg, high associated phase angles above "B"). Electrode coupling) which is considered to correspond to electrode coupling or excessive electrode coupling). One embodiment shall correspond to the state indicated by the following phase angle values. Insufficient electrode coupling: Φ&gt; -5 ° Sufficient electrode coupling: -5 °&gt; Φ&gt; -10 ° High / excessive electrode coupling: Φ &lt;-10 °

A "high" electrode bond or an "excessive" electrode bond can be high / excessive in relation to electrical, mechanical or both (bonds between the electrode and the target tissue). In one embodiment, high / excessive or tight electrode coupling means high / excessive mechanical contact between the electrode and the target tissue. For various reasons it may be desirable to know when high mechanical contact or excessive mechanical contact exists between the electrode and the tissue. For example, it may be desirable to avoid high mechanical contact or excessive mechanical contact between the electrode and the target tissue (eg, to reduce the likelihood of the electrode pointing into the tissue wall, membrane, etc.). .. However, it may be desirable to know when the electrode exerts sufficient mechanical force on the target tissue (eg, by increasing the likelihood that the electrode will be directed into the tissue wall, membrane, etc.). To allow access to the desired area on the other side of the membrane).

The evaluation result of step 408 may be output by any suitable method according to step 412 of the electrode coupling evaluation protocol 400 of FIG. 9a. Any suitable output, eg visually (eg, a bar graph, or any other suitable display in any suitable position or combination of positions), audibly (eg, alarm), physically (eg, to an electrode). It may be utilized by vibrating a handle held by a physician performing the based procedure (as described in more detail herein) or by any combination thereof. A single output may be provided. A combination of two or more outputs may be used. You may publish one or more outputs in a single location or in multiple locations.

FIG. 9b shows an embodiment of the Electrode Binding Evaluation Protocol 400', which may be used to evaluate the binding of an electrode (eg, a catheter electrode) to any suitable tissue, in which case this evaluation will be performed. Based on reactance. Since Protocol 400'is a variant of Protocol 400 in FIG. 9a, we use the "single prime" indication in relation to the reference numbers that identify the individual steps in Protocol 400' in Figure 9b.

Step 402'of evaluation protocol 400' in Figure 9b relates to delivering an electrical signal. Only a single frequency is required to provide that rating for protocol 400'. That is, for evaluation protocol 400', a single frequency may be used to provide electrode coupling evaluation. This is usually done after the electrodes have been placed at least generally in the vicinity of the target tissue (eg, in the heart chamber). Then, in step 404', the reactance of the electric circuit including the electrode and the target tissue is determined. This reactance may be determined by any suitable method. For example, the phase angle may be measured (eg, as described above), the impedance may be measured, or the reactance may be calculated from these two values (eg, the sine of the phase angle is relative to the reactance impedance). Equal to the ratio). Another option for determining reactance is to determine the phase or frequency response of the pulse wave.

In step 408'of Protocol 400', the electrode coupling is evaluated based on the reactance described above. This electrode coupling from step 408'may be classified by performing step 410'. However, the classification of step 410'is not always necessary in all cases. In either case, the evaluation result is output according to step 412'. Step 412'may correspond to step 412 of the electrode coupling evaluation protocol 400 of FIG. 9a.

Evaluation of the bond of the electrode to the tissue (Protocol 400'step 408') may be performed by any suitable method. For example, the reactance determined through step 404'may be compared to one or more benchmark reactance values (eg, using a reactance comparator). These benchmark reactance values may be determined / set experimentally, for example, by any suitable method. These benchmark reactance values may be stored in a suitable data structure, such as a computer-readable data storage medium, or may be made available to a reactance comparator. Generally and in one embodiment, the reactance decreases as the electrode / tissue (for example, myocardium) binds.

For the purpose of classification in step 410', there may be one or more benchmark reactance values (eg, a single benchmark reactance value or a range of benchmark reactance values) for one or more of the following states: .. That is, 1) insufficient electrode coupling (for example, an electrode coupling in which a related reactor of less than "A" is considered to correspond to an insufficient electrode coupling), 2) sufficient electrode coupling (for example, an associated reactor of "A". An electrode coupling above "B" and below "B" is considered to correspond to a sufficient electrode coupling) and 3) High electrode coupling or excessive electrode coupling (eg, associated reactors above "B" are high electrode coupling or Electrode coupling, which is considered to correspond to excessive electrode coupling). One embodiment shall correspond to the state indicated by the following reactance values. Inadequate electrode coupling: X&gt; -5 Sufficient electrode coupling: -5&gt; X&gt; -15 High / excessive electrode coupling: X &lt;-15

One benefit of basing electrode coupling assessments on phase angles is that phase angles are less sensitive to changes or behavioral settings between patients than impedances or reactances considered alone or individually. Other methods of reducing sensitivity to changes between tissues or other such conditions may be utilized to provide electrode binding assessment. FIG. 9c shows such an embodiment of the electrode binding evaluation protocol 480, ie a protocol 480 that can be used to assess the binding of an electrode (eg, a catheter electrode) to any suitable tissue. Step 482 of evaluation protocol 480 relates to delivering a constant frequency electrode signal to the electrodes. At least one electrical parameter is measured in step 484. Then, in step 486, from this measured value, what may be characterized as an "impedance component ratio" is determined. The phrase "impedance component ratio" means any term, such as the phase angle, which is the ratio of two individual components of impedance (the tangent of the phase angle is equal to the ratio of the reactance to the resistance). The impedance component ratio may be determined by any suitable method such as simply measuring the phase angle. Other methods of determining the impedance component ratio include, but are not limited to, determining the resistance and reactance at the frequencies included in step 482 and calculating the impedance component ratio from these two parameters. .. By using the ratio of the two components related to impedance, it is possible to reduce the sensitivity to changes between tissues for electrode binding evaluation, that is, evaluation of the binding between the electrode and the target tissue.

The electrode coupling is evaluated in step 488 of protocol 480. This electrode coupling from step 488 may be classified by performing step 490, which may follow step 410 of the electrode coupling evaluation protocol 400 described above in connection with FIG. 9a. Therefore, the classification of step 490 is not always necessary in all cases. In either case, the evaluation result is output according to step 492. Step 492 may follow step 412 of the electrode coupling evaluation protocol 400 described above in connection with FIG. 9a.

In each of the protocols of FIGS. 9a-9c, the electrode bond is a mechanical bond (ie, physical contact) between the electrode and the target tissue, and an electrical bond (eg, a sufficient portion of electrical energy). It includes the state of extending from the electrode to the target tissue). Whenever there is a mechanical bond, there is an electrical bond. However, the opposite is not true. There can be electrical coupling without the electrodes coming into contact with the target tissue. FIG. 10 shows a typical example when there is an electrical bond between the electrode 414 and the target tissue 416 without mechanical contact. Here, the electrode 414 is placed within the void 418 on the surface of the tissue 416, which provides an electrical bond between the electrode 414 and the target tissue 416. Therefore, each of the protocols of FIGS. 9a-9c may exhibit an electrical bond that does not require mechanical contact between the electrode and the target tissue.

FIGS. 11a-11c schematically show the various configurations that can be used in connection with providing an electrode coupling assessment. Each of these systems will be described in relation to the truncated electrode, but electrode coupling evaluation may be used in any suitable application in which the electrode provides any suitable function or combination of functions. Each of the systems of FIGS. 11a-11c may be used to provide the evaluation protocol described above in relation to FIGS. 9a-9c. Also, in order to implement these configurations commercially, there may be currents from a filter (eg, one or more other sources that should be separated from the currents used to perform the coupling evaluation). When it is desirable to utilize a variety of other components, such as one or more components that "electrically protect" the patient and / or electrical circuits used to perform electrode coupling evaluations. It should be understood that there is also.

FIG. 11a shows a resection system 420 including a resection power supply 424, a resection electrode 422 and a return electrode 426. Any suitable frequency may be used by the excision power supply 424. Each of the excised electrode 422 and the return electrode 426 may be of any suitable size, shape and / or configuration. Usually, the excision electrode 422 is in the form of a catheter electrode placed within the patient's body. The return electrode 426 may be located at any suitable location (eg, a ground patch placed on the patient's skin, a catheter electrode placed within the patient's body).

Additional components of the excision system 420 include an electrode coupling evaluation power supply 428 (evaluation power supply 428), an evaluation return electrode 430 and an electrode coupling evaluation module 432 (evaluation module 432). Any suitable frequency may be used by the evaluation power supply 428. Generally, the truncated power supply 424 also uses a significantly higher current than the evaluation power supply 428.

The evaluation return electrode 430 may be of any suitable size, shape and / or configuration, and may be arranged at any suitable position. In one embodiment, the return electrode 426 and the evaluation return electrode 430 are forms of separate structures that are located at different locations. In another embodiment, a single structure (a single unit acting as the return electrode 426 and the evaluation return electrode 430) provides the function of the return electrode 426 and the function of the evaluation return electrode 430.

The excision electrode 422 receives power from either the excision power supply 424 or the evaluation power supply 428, depending on the position of the switch 434 with respect to the excision system 420. That is, in the case of the excision system 420 of FIG. 11a, the excision operation and the electrode coupling evaluation operation may not be performed at the same time. During the electrode coupling evaluation operation, the switch 434 is, of course, arranged to receive power from the evaluation power source 428. This allows the evaluation module 432 to evaluate the bond between the excised electrode 422 and the target tissue. In order to provide the electrode coupling evaluation function by the evaluation module 432, various configurations treated in the present specification (for example, evaluation based on phase angle comparison, evaluation based on reactance comparison, evaluation based on impedance component ratio comparison, etc. Any suitable configuration may be utilized, including (evaluation based on identifying frequencies associated with 0 ° phase frequency or 0 inductance frequency) as described below in connection with FIGS. 12a and 12b. Evaluation module 432 may provide electrode coupling evaluation using any of the protocols of FIGS. 9a-9c from a single frequency.

FIG. 11b shows an excision system 440 including an excision power source 444, an excision electrode 442 and a return electrode 446. Any suitable frequency may be used by the excision power supply 444. Each of the excised electrode 442 and the return electrode 446 may be of any suitable size, shape and / or configuration. Usually, the excision electrode 442 is in the form of a catheter electrode placed within the patient's body. The return electrode 446 may be placed in any suitable location (eg, a ground patch placed on the patient's skin, a catheter electrode placed within the patient's body).

Additional components of the excision system 440 include an electrode coupling evaluation power supply 448 (evaluation power supply 448), an evaluation return electrode 450 and an electrode coupling evaluation module 452 (evaluation module 452). Any suitable frequency may be used by the evaluation power supply 448. However, in the case of the excision system 440, the excision power supply 444 and the evaluation power supply 448 operate at different frequencies in order to adapt to the simultaneous execution of the excision operation and the electrode coupling evaluation operation. In addition, the cut power supply 444 typically also uses a significantly higher current than the evaluation power supply 448.

The evaluation return electrode 450 may be of any suitable size, shape and / or configuration, and may be arranged at any suitable position. In one embodiment, the return electrode 446 and the evaluation return electrode 450 are forms of separate structures arranged at different positions. In another embodiment, a single structure (a single unit acting as the return electrode 446 and the evaluation return electrode 450) provides the function of the return electrode 446 and the function of the evaluation return electrode 450.

The excision electrode 442 receives power from the excision power source 444 or the evaluation power source 448 at the same time. That is, in the case of the excision system 440 of FIG. 11b, the excision operation and the electrode coupling evaluation operation can be performed at the same time. In this regard, the cut power supply 444 and the evaluation power supply 448 also operate at different frequencies. Evaluation module 452 may provide electrode coupling evaluation using any of the protocols of FIGS. 9a-9c from a single frequency. In each case, the evaluation module 452 evaluates the bond between the excised electrode 442 and the target tissue. The above description in relation to the evaluation module 432 for the excision system 420 of FIG. 11a is equally applicable to the evaluation module 452 for the excision system 440 of FIG. 11b.

FIG. 11c shows an excision system 460 including an excision power source 464, an excision electrode 462 and a return electrode 466. Any suitable frequency may be used by the excision power source 464. Each of the excised electrode 462 and the return electrode 466 may be of any suitable size, shape and / or configuration. Usually, the excision electrode 462 is in the form of a catheter electrode placed within the patient's body. The return electrode 466 may be located at any suitable location (eg, a ground patch placed on the patient's skin, a catheter electrode placed within the patient's body).

Additional components of the excision system 460 include an electrode coupling evaluation power supply 468 (evaluation power supply 468). Any suitable frequency may be used by the evaluation power supply 468. Generally, the cut power supply 464 also uses a significantly higher current than the evaluation power supply 468.

The excision system 460 further includes a pair of electrode coupling evaluation modules 472a, 472b (hereinafter, "evaluation module 472a" and "evaluation module 472b"). Evaluation module 472a is associated with evaluation power supply 468 and evaluation module 472b is associated with cut power supply 464. In the illustrated embodiment, the return electrode 466 is used for both the excision operation and the electrode coupling evaluation operation, but it is also possible to use separate return electrodes as in the case of the embodiments of FIGS. 11a and 11b described above. obtain.

The excision electrode 462 receives power from either the excision power source 464 or the evaluation power source 468, depending on the position of the switch 474 with respect to the excision system 460. However, unlike the embodiment of FIG. 11a, the electrode coupling evaluation operation may be performed independently of the position of switch 474. If the excision electrode 462 is electrically interconnected with the evaluation power supply 468 through the switch 474, the evaluation module 472a is used to evaluate the bond between the excision electrode 462 and the target tissue. If the excision electrode 462 is electrically interconnected to the excision power source 464 through the switch 474, the evaluation module 472b is used to evaluate the bond between the excision electrode 462 and the target tissue. The evaluation modules 427a, 472b may each provide an electrode coupling evaluation using any of the protocols of FIGS. 9a-9c from a single frequency.

The evaluation modules 472a, 472b may utilize any suitable configuration, including the various configurations covered herein, without limitation, in order to provide their respective electrode coupling evaluation functions. The above description in relation to the evaluation module 432 for the excision system 420 of FIG. 11a is equally applicable to the evaluation modules 472a, 472b for the excision system 460 of FIG. 11c. Evaluation modules 472a, 472b usually have the same configuration for evaluating electrode coupling, but not in all cases. When the evaluation modules 472a and 472b have the same configuration, the cut power supply 464 and the evaluation power supply 468 usually operate at the same frequency. Therefore, the excision system 460 corresponds to the evaluation of the electrode coupling before initiating the excision operation (eg, using the evaluation current and evaluation module 472a) and further corresponds to the evaluation of the electrode coupling during the excision operation (eg, using the evaluation current and evaluation module 472a). , Using the actual excision current vs. the smaller current, and using the evaluation module 472b). The excision system 440 of FIG. 11b also corresponds to the evaluation of electrode coupling during excision operation, but uses a separate evaluation current vs. the actual excision current.

One of the electrodes used by the evaluation module in each of the embodiments of FIGS. 11a-11c is, of course, a resection or "active" electrode. Both the electrode coupling evaluation module and the excision electrode require separate electrodes that interface with the patient in some way to provide their respective functions. Figure 1a shows the return electrode used by the evaluation module and the return electrode that works with the excision electrode to provide electrical energy to the tissue to provide one or more desired functions. An embodiment incorporated into the structure is shown. More specifically, the excision electrode 20 (eg, catheter electrode) is located in the cavity of the heart 16 (eg, left atrium) and is in the form of catheter electrode 20. The return electrode 20a (eg, a catheter electrode) is also placed in the same cavity of the heart 16 and is used by each of the evaluation modules of FIGS. 11a-11c (to evaluate the binding of the excision electrode 20 to the target tissue 24). It can be used by the excision electrode 20 (to deliver electrical energy to the target tissue 24 to provide the desired medical function). Therefore, the excision electrode 20 and the return electrode 20a may be associated with different catheters and thereby moved individually. In one embodiment, the return electrode 20a has a larger surface area than the excision electrode 20. Each of the excised electrode 20 and the return electrode 20a has electrode tips spaced apart from each other.

The configuration shown in FIG. 1a provides two electrodes 20, 20a in a common heart chamber. Another option is that two or more electrodes are associated with a common catheter, but the catheter has two separate distal parts, each with an electrode at a separate electrode tip at its distal end, which. As a result, the tips of the electrodes are spaced apart from each other.

One or more methods of using the phase angle to evaluate the bond between the active electrode and the target tissue have been presented above. Another method in which the phase angle may be used to evaluate the electrode coupling is shown in FIGS. 12a and 12b. FIG. 12a includes an electrode including a variable frequency source 502, an electrical parameter measurement module 504, an electrode coupling evaluation module 506, and an electrode 508 that is coupled to tissue 510 to provide the desired function or combination of functions (eg excision). A schematic diagram of the coupling evaluation system 500 is presented. Although the return electrode is not shown in FIG. 12a, it may be of any suitable type and may be placed at any suitable location. Generally, the variable frequency source 502 provides an electrical signal to the electrode 508 for the purpose of delivering electrical energy to the tissue 510. The electrical parameter measurement module 504 may be of any suitable type and / or configuration, measures one or more electrical parameters, and provides the information used by the electrode coupling evaluation module 506. The electrode coupling evaluation module 506 evaluates the coupling between the electrode 508 and the tissue 510.

FIG. 12b presents an embodiment of the electrode coupling protocol 520 that can be used by the electrode coupling evaluation module 506 of FIG. 12a. By performing step 524, one or more electrical signals are sent to the electrode 508. The baseline coupling state can be evaluated. For example, baseline coupling states can be defined according to steps 524-528 of Protocol 520. The term "baseline coupled state" includes zeroing phase angle or zeroing reactance at a desired frequency in a medium (eg, blood).

By performing step 525, the time when the electrode is in the desired medium, eg blood, is determined. Next, the baseline connection state is established by executing step 526. For example, a physician can activate an input device to direct the establishment of a baseline coupling state. Then, in step 528, protocol 520 adjusts to the baseline coupling state by correcting the phase angle or reactance to zero.

As an alternative to zeroing the baseline coupling state, the value of the baseline coupling state established in step 526 may be stored and used to determine the electrode coupling state for such a baseline coupling state. In the second alternative embodiment, the baseline coupling state may be determined by comparing the determined phase angle with one or more predetermined benchmark values. These benchmark values may be experimentally confirmed / set in any suitable manner, for example by in vitro, ex vivo or in vivo tests. These benchmark values may be stored in a suitable data structure, for example, in a computer-readable data storage medium, or may be made available to a phase comparator.

Electrode coupling may be evaluated according to step 532 of protocol 520 using the baseline coupling state from step 528. One or more electrical parameters may be determined in any suitable manner and compared to the corresponding values of the baseline coupling state from step 528. For example, the following categories may be provided. That is, 1) insufficient electrode coupling (for example, an electrode coupling in which the value associated with the baseline coupling state below "A" corresponds to insufficient electrode coupling), 2) sufficient electrode coupling (for example, Values associated with a baseline coupling state above "A" and below "B" are considered to correspond to sufficient electrode coupling) and 3) high electrode coupling or excessive electrode coupling (eg, "" A value associated with the baseline coupling state above B is considered to correspond to a high electrode coupling or an excessive electrode coupling).

In another embodiment, the electrical coupling is measured as a function of "target frequency", a frequency corresponding to a preset value (eg, a preset reactance or phase angle value) for an electrical parameter. FIG. 12c presents an embodiment of the electrode coupling protocol 620 that can be used by the electrode coupling evaluation module 506 of FIG. 12a. Sending an electrical signal to electrode 508 by performing step 624. Sends electrical signals at different frequencies. At each frequency delivered, step 626 measures reactance and / or phase. Step 628 compares the measured reactance or phase with the preset value. The frequency at which the reactance or phase matches the preset value is the "target frequency". Any suitable value, including positive, zero or negative values, may be used with respect to the preset value for the purpose of step 628 (eg, the target frequency may be referred to as the 0 ° phase frequency). In addition, the zero phase angle, or target state frequency, may be referred to as the zero inductance frequency).

When protocol 620 determines that a target frequency is present, it proceeds to step 630, where it uses the information provided by step 628 to evaluate the binding of electrode 508 to tissue 510 and follows step 636 of protocol 620. The result of this evaluation is output. Step 636 may follow step 412 of the protocol described above in relation to FIG. 9a.

An assessment of electrode binding to tissue is provided through step 630 of protocol 620 in Figure 12c. The target frequency from step 628 may be compared (eg, using a comparator) with one or more benchmark frequency values. These benchmark frequency values may be determined / set by any suitable method. Values can be experimentally pre-determined, for example by in vitro, ex vivo or in vivo tests. These benchmark frequency values may be stored in a suitable data structure, for example, in a computer-readable data storage medium. Benchmark frequency values may be determined by the physician during the procedure. For example, it may be determined when the electrodes are in the desired medium, eg blood. At that point, the physician can activate the input device to set benchmark values for existing binding-related conditions.

One or more benchmark frequency values for one or more of the following states for the purpose of classifying evaluation protocol 620 in Figure 12c (eg, a single benchmark frequency value or a range of benchmark frequency values): There may be. That is, 1) insufficient electrode coupling (for example, an electrode coupling in which a target frequency below "A" corresponds to insufficient electrode coupling), 2) sufficient electrode coupling (for example, a target frequency of "A" Electrode coupling above "B" and below "B" corresponds to sufficient electrode coupling) and 3) Excessive electrode coupling (eg, target frequency above "B" corresponds to excessive electrode coupling) Electrode coupling). One embodiment shall correspond to the state indicated by the following target frequency values (F)._tIs the target frequency for the indicated state). Insufficient electrode coupling: F_t&lt;120kHz Sufficient electrode coupling: 120kHz &lt;F_t&lt;400kHz High / excessive electrode coupling: F_t&gt; 400kHz

Protocol 620 of Figure 12c may be implemented in any suitable manner. For example, the target phase frequency may be obtained by monitoring the impedance and sweeping the signal frequency (eg according to System 500 in Figure 12a). This frequency sweep is provided between two suitable values (eg 50kHz and 1MHz) using any suitable incremental variation between these values for the sweep (eg 10-20kHz increment). May be good. This technique uses what can be called frequency switching, which involves measuring impedances at one frequency at a time and rotating those frequencies with a frequency synthesizer or the like. Another technique is to combine multiple frequencies and filter the combined signals to determine the impedance at each of the individual frequencies. It should be understood that in some cases interpolation may be required to determine the frequency associated with the target frequency state (eg, the target frequency state between the two frequencies used by protocol 620). If it is determined that there is a frequency associated with).

Although some embodiments of the present invention have been described above to some extent, those skilled in the art can make many modifications to the disclosed embodiments without departing from the spirit or scope of the invention. Reference numerals are used only for identification purposes to aid the reader's understanding of the invention, and they do not impose any limitation on the position, orientation or use of the invention. It is intended that all matters contained in the above description or shown in the accompanying drawings should be construed as merely exemplifying rather than limiting. Details or structural changes may be made without departing from the spirit of the invention as defined in the appended claims.

<figref num="1">FIG. 6 is a schematic representation of an exemplary tissue resection system that can be implemented to assess electrode-tissue contact during a tissue resection procedure for a patient.</figref><figref num="1a">FIG. 1 is a detailed view of the patient's heart, showing an electrode catheter after it has been moved into the patient's heart.</figref><figref num="2a">Shown is an exemplary level of electrical contact or coupling between the electrode catheter and the target tissue.</figref><figref num="2b">Shown is an exemplary level of mechanical contact or binding between the electrode catheter and the target tissue.</figref><figref num="3">It is a high-level functional block diagram which shows the exemplary tissue excision system of FIG. 1 in more detail.</figref><figref num="4">It is a model of an electrode catheter that contacts (or binds to) the target tissue.</figref><figref num="4a">It is a simple electric circuit for the model shown in FIG.</figref><figref num="5">An exemplary phase detection circuit that can be implemented in a tissue excision system that evaluates electrode-tissue contact or coupling.</figref><figref num="6">It is an exemplary block diagram which shows the phase angle measurement for contact detection and tissue detection.</figref><figref num="7">It is an exemplary block diagram showing the phase angle measurement during excision in which both the excision energy and the contact detection signal are applied simultaneously to the excision electrode.</figref><figref num="8">It is an exemplary block diagram which shows the phase angle measurement during excision which switches between a detection signal and an excision output.</figref><figref num="9a">An embodiment of a protocol that can be used to evaluate the bond between an electrode and a tissue based on a phase angle comparison is shown.</figref><figref num="9b">An embodiment of a protocol that can be used to evaluate the bond between an electrode and a tissue based on reactance comparison is shown.</figref><figref num="9c">An embodiment of a protocol that can be used to evaluate the coupling between an electrode and a tissue based on an impedance component ratio comparison is shown.</figref><figref num="10">A typical schematic representation of the electrical coupling between the electrode and the tissue is shown.</figref><figref num="11a">Schematic representation of an embodiment of a resection system using two power supplies operating at different frequencies, only one of these power supplies is interconnected with the resection electrode at any given time and one of these power supplies Is used to evaluate the bond between the electrode and the tissue.</figref><figref num="11b">Schematic representation of an embodiment of an excision system using two power sources operating at different frequencies, both power sources are always interconnected with excision electrodes, one of which is between the electrode and the tissue. Used to evaluate the binding of.</figref><figref num="11c">Schematic representation of an embodiment of a resection system using two power supplies operating at least generally at the same frequency, at any given time only one of these power supplies is interconnected with the resection electrode and each of these power supplies Can be used to assess the bond between the electrode and the tissue.</figref><figref num="12a">An embodiment of a system for evaluating the bond between an electrode and a tissue is shown.</figref><figref num="12b">Demonstrates an embodiment of a protocol that can be used to evaluate the bond between an electrode and a tissue based on identifying the baseline binding state.</figref><figref num="12c">Demonstrates an embodiment of a protocol that can be used to evaluate the bond between an electrode and tissue based on identifying the target frequency.</figref>