Lead including conductors configured for reduced mri-induced currents

Various embodiments of the present invention generally relate to implantable medical devices. More specifically, embodiments of the present invention relate to conductor configurations for compatibility with magnetic resonance imaging (MRI).

When properly functioning, the human heart maintains its own rhythm and is capable of pumping sufficient blood throughout the body's circulatory system. However, some people have irregular cardiac rhythms called cardiac rhythm abnormalities that can result in decreased blood circulation and cardiac output. One method of treating cardiac dysrhythmia involves the use of pulse generators, such as pacemakers, implantable cardioverter-defibrillators (ICDs), or cardiac resynchronization therapy (CRT) devices. Such devices are typically coupled to several conductive leads with one or more electrodes that can be used to deliver at least one of pacing therapy or electric shock to the heart. .. For example, in atrioventricular (AV) pacing, the leads are usually placed in the ventricles and atria of the heart and attached via lead terminal pins to a pacemaker or defibrillator implanted in the pectoralis major or abdomen. Be done.

Magnetic resonance imaging (MRI) is a non-invasive imaging technique that utilizes nuclear magnetic resonance technology to obtain an image of the inside of a patient's body. Typically, the MRI system uses a magnetic coil with a magnetic field strength of about 0.2-3 Tesla. During the procedure, body tissue is temporarily exposed to RF pulses of electromagnetic energy in a plane perpendicular to the magnetic field. The electromagnetic energy generated from these pulses can be used to image body tissue by measuring the relaxation properties of excited nuclei in the tissue. In some cases, imaging the patient's chest area may be clinically beneficial. In chest MRI procedures, the implanted pulse generator and leads can also be exposed to the applied electromagnetic field.

<p num="0004"> Various embodiments of the present invention generally relate to conductor configurations of implantable leads for compatibility with magnetic resonance imaging (MRI). In Example 1, the electrical leads include a flexible body to provide a connector, an inner conductor coil, and a high voltage multiplex filer outer coil. The flexible body has a proximal region with a proximal end and a distal region. The connector is coupled to the proximal end of the flexible body of the lead to electrically and mechanically connect the lead to the implantable pulse generator. A low voltage inner conductor coil is one or more having a filer thickness, pitch and average coil diameter configured such that the inner conductor coil has a first inductance value of 0.0079 μΗ / mm (0.2 μΗ / inch) or greater. It is formed from a filer wound in a substantially cylindrical shape. The high voltage multiplex filer outer coil has a proximal area, an distal zone, and a length, and the high voltage multiplex filer outer coil has a direct current (DC) resistance of less than approximately 10 ohms and each has a filer thickness. The high voltage multiplex filer outer coil is formed from two or more substantially cylindrically wound filers having a high voltage multiplex filer outer coil having a second coil of 0.0039 μΗ / mm (0.1 μΗ / inch) or more. It has a pitch and an average coil diameter configured to have an inductance value of. The low voltage inner conductor coil and the high voltage outer coil are coaxially arranged so as to be separated from each other.</p><p num="0005"> In the second embodiment, in the electric lead wire of the first embodiment, a layer of an insulator is arranged around at least a part of the inner conductor coil. In Example 3, the electric lead wire of at least one of Examples 1 or 2 has an inner conductor coil having a single filer structure.</p><p num="0006"> In Example 4, at least one of Examples 1, 2 or 3 has an inner conductor coil having an average pitch of approximately 0.13 mm (approximately 0.005 inch).</p><p num="0007"> In Example 5, the electrical lead of Example 4 has an inner conductor coil having a single filer structure and an average coil diameter of 0.58 mm (0.023 inches). In Example 6, the electric lead wire of any of Examples 1 to 5 has an inner conductor coil having an inductance larger than about 0.020 μΗ / mm (about 0.5 μΗ / inch).</p><p num="0008"> In the seventh embodiment, in any of the electric lead wires of the first to sixth embodiments, the first inductance value (L) is the number of filers wound in a cylindrical shape (N) and the pitch of the inner conductor coil (N). Depending on b) and the average coil diameter (a), the equation Lμ_０πa^２/ 4b^２N^２(In the formula, μ_０Is the magnetic permeability of free space).</p><p num="0009"> In Example 8, the electrical lead wire of any of Examples 1-7 has an inner conductor coil having a DC resistance of less than 200 ohms. In Example 9, the inner conductor coil of any of the electric lead wires of Examples 1 to 8 is bipolar or unipolar.</p><p num="0010"> In the tenth embodiment, the electric lead wires of the first to ninth embodiments are conductor coils in which the outer coil of the high voltage multiplex filer is a ribbon type. In Example 11, the medical lead comprises a flexible body, a connector, a low voltage inner conductor coil, a multiple filer high voltage outer conductor coil, and a trifilar shock coil. The flexible body has a proximal region with a proximal end and a distal region. The connector is coupled to the proximal end of the body configured to electrically and mechanically connect the leads to the implantable pulse generator. The low voltage inner conductor coil is configured to transmit an electrical signal between the tip end area and the proximal end side area of the lead wire, and the low voltage inner conductor coil has a low voltage inner conductor coil of 0.0079 μΗ / mm ( It is formed from one or more substantially cylindrically wound filers having a pitch and average coil diameter configured to have a first inductance of 0.2 μΗ / inch) or greater. The multiple filer high voltage outer conductor coil has a quad filer spiral shape that radially surrounds at least part of the low voltage inner conductor coil, a DC resistance of less than 10 ohms, and 0.0039 μΗ / mm (0.1 μΗ /). It has an outer diameter and an average pitch configured to provide a multiple filer high voltage outer conductor coil with a second inductance greater than or equal to an inch). The shock coil of the trifilar has a proximal end, and the proximal end of the trifiler shock coil is connected to the distal end of the multiple filer high voltage outer coil via a coupler. The low voltage inner conductor coil and the multiple filer high voltage outer conductor coil are coaxially arranged so as to be separated from each other.</p><p num="0011"> In Example 12, the medical lead of Example 11 is one in which the lead surrounds one or more of a low voltage inner conductor coil, a multiple filer high voltage outer conductor coil, and a trifilar shock coil. The above insulating material layer is further provided.</p><p num="0012"> In Example 13, at least one of the medical leads of Example 11 or 12 has a multiple filer high voltage outer coil having an outer diameter larger than the outer diameter of the trifilar shock coil.</p><p num="0013"> In Example 14, the medical lead wire of any of Examples 11 to 13 has a low voltage inner conductor coil, a multiple filer high voltage outer conductor coil, and a trifilar shock coil having different pitches.</p><p num="0014"> In Example 15, the medical lead wire of any of Examples 11-14 has a low voltage inner conductor coil, a multiple filer high voltage outer conductor coil, and a trifilar shock coil of about 0.005 inch each ( It has a pitch of 0.127 mm) or less.</p><p num="0015"> In Example 16, the implantable medical device comprises a proximal region having a proximal end that is mechanically and electrically coupled to a pulse generator and an distal region that is implanted within the heart of the patient. It comprises a lead with a flexible body, which is configured to carry an electrical signal between the heart and the pulse generator. The lead further comprises a low voltage inner conductor coil configured to carry an electrical signal between the lead region and the proximal region of the lead, the low voltage inner conductor coil being wound one or more. Formed from a filer. The low voltage inner conductor coil has separate individual turns with pitch, average coil diameter, and the number of one or more wound filers is 0.0079 μΗ / mm (0.2 μΗ / inch). It is configured to have the above first inductance value. The leads further include a high voltage outer coil with a quad filer spiral shape with a DC resistance of less than 10 ohms, which radially surrounds at least part of the low voltage inner conductor coil. And has an outer diameter, filer diameter, and average pitch configured to obtain a high voltage outer coil with a second inductance value of 0.0039 μΗ / mm (0.1 μΗ / inch) or greater. .. The lead also further comprises a shock coil for a trifilar with a proximal end, the proximal end being connected to the distal end of the high voltage outer coil via a coupler. The low voltage inner conductor coil and the high voltage outer coil are coaxially arranged so as to be separated from each other.</p><p num="0016"> In Example 17, the implantable medical device of Example 16 has a DC resistance with leads of less than 200 ohms. In Example 18, at least one implantable medical device of Example 16 or 17 comprises a filer in which the low voltage inner conductor coil is made from dft® MP35N .</p><p num="0017"> In Example 19, in any of the implantable medical devices of Examples 16-18, the low voltage inner conductor coil is bipolar or unipolar. In Example 20, in any of the implantable medical devices of Examples 16-19, the pitch of the high voltage conductor coil is about 0.25 mm (about 0.010 inch), and the average coil of the high voltage conductor coil. The diameter is about 2.3 mm (about 0.090 inch), resulting in a coil inductance value of about 0.0051 μΗ / mm (about 0.13 μΗ / inch), and the pitch of the inner conductor coil is about 0.13 mm (about 0.13 mm). The inner conductor coil is formed from one cylindrically wound filer, and the average coil diameter of the inner conductor coil is about 0.58 mm (about 0.023 inches). It has a coil inductance value per unit length of 0.020 μΗ / mm (about 0.5 μΗ / inch).</p><p num="0018"> In Example 21, in any of the implantable medical devices of Examples 16-20, the pulse generator is a pacemaker or defibrillator. In Example 22, the implantable medical lead is a multi-lumen lead body, a connector assembly at the proximal end of the lead body, a plurality of electrodes coupled to the lead body, and inside the lead body. Has multiple conductors that extend. The lead body comprises a tubular member having a plurality of lumens penetrating in the longitudinal direction. Each conductor extends longitudinally inside its lumen and is electrically coupled to one of the electrodes and even to the electrical contacts of the connector assembly. At least one of the conductors is a coil conductor formed from a filer wound in one or more substantially cylindrical shapes, and the coil conductor is 0.0079 μΗ / when the lead wire is exposed to a certain range of high frequencies. It has a filer thickness, pitch and average coil diameter configured to have a first inductance value of mm (0.2 μΗ / inch) or greater.</p><p num="0019"> In Example 23, the implantable medical lead of Example 21 is formed from a single cylindrically wound filer with a coil conductor having a thickness of about 0.10 mm (about 0.004 inch). And the coil conductor has a pitch of about 0.13 mm (about 0.005 inch) and an average coil diameter of about 0.58 mm (about 0.023 inch) and is about 0.020 μΗ / mm (about 0. It has a coil inductance per unit length of 5 μΗ / inch).</p><p num="0020"> In Example 24, in the implantable medical lead wire of Example 21 or 22, the electrode coupled to the coil conductor is a pace / sense electrode.</p>

<figref num="1">Schematic of a medical system with an MRI scanner and an implantable cardiac rhythm management system implanted inside the torso of a human patient according to various embodiments of the present invention.</figref><figref num="2A">Schematic of an exemplary pulse generator and lead implanted in the body of a patient that can be used according to some embodiments of the invention.</figref><figref num="2B">FIG. 2 is a schematic diagram showing a simplified equivalent circuit for the lead wire of FIG. 2A.</figref><figref num="3">The figure which shows the typical lead wire which can be used according to one or more embodiments of this invention.</figref><figref num="4">Sectional drawings of a high voltage shock coil and a low voltage coil according to various embodiments of the present invention.</figref><figref num="5A">FIG. 5 shows various parts of an inner conductor coil, a high voltage conductor coil, and a shock coil according to some embodiments of the present invention.</figref><figref num="5B">FIG. 5 shows various parts of an inner conductor coil, a high voltage conductor coil, and a shock coil according to some embodiments of the present invention.</figref><figref num="5C">FIG. 5 shows various parts of an inner conductor coil, a high voltage conductor coil, and a shock coil according to some embodiments of the present invention.</figref><figref num="6">The figure which shows the example of the temperature rise which occurs when the typical lead wire designed by the standard lead wire design and various embodiments of this invention is exposed to the frequency associated with MRI.</figref><figref num="7">Cross-sectional view of a lead with a multi-lumen structure that can be used in some embodiments of the present invention.</figref>

Drawings are not always drawn in proportion to their actual size. For example, some dimensions of the elements in the figure may be scaled up or down to help enhance understanding of embodiments of the invention. Although there are various variations and alternative forms of the present invention, specific embodiments are shown in the drawings as examples and are described in detail below. However, it is not an object of the present invention to be limited to the particular embodiments described. On the contrary, the invention is intended to include all modifications, equivalents, and alternative forms within the scope of the invention as defined by the appended claims.

Detailed explanation Implantable cardioverter-defibrillators (ICDs) are typically implanted in the patient's pectoral muscles. In some cases, one or two electrodes may extend from the ICD into at least one of the atrium or ventricle of the patient's heart. For epicardial leads, the electrodes are attached to the outer surface of the patient's heart. The ICD system can provide at least one of the pacing function to the patient's heart or the high voltage shock therapy that transforms the patient's heart from fibrillation to normal heart function.

As described in more detail below, various embodiments of the present invention relate to the design of new leads that are conveniently adapted for operation in an magnetic resonance imaging (MRI) environment. In some embodiments, the leads provide adequate electrical performance for tachycardia therapy and even minimize the response of the leads to the electromagnetic energy applied during the MRI procedure. It comprises a combination of at least one of the unique shock coils or coil conductors configured to be.

In the following description, a number of specific details are provided for illustration purposes to provide a complete understanding of embodiments of the present invention. However, it will be apparent to those skilled in the art that embodiments of the present invention are feasible without some of those particular details.

Further, for convenience, some embodiments have been described with respect to the ICD in the presence of an MRI scanner. Embodiments of the invention apply to a variety of other physiological measurements, treatments, implantable medical devices, and other non-invasive testing techniques in which conductive leads are exposed to a time-varying magnetic field. It can be possible. As such, the uses discussed herein are not intended to be limiting and are exemplary. Other systems, devices and networks to which embodiments are applicable include, but are not limited to, other types of perceptual systems, medical devices, medical procedures, and computer devices and systems. In addition, various embodiments are applicable to all levels of perceptual devices, from a single IMD with sensors to a large network of perceptual devices.

FIG. 1 illustrates a medical system 100 with an MRI scanner 110, an implantable customer relationship management (CRM) system 115 implanted in the body of a human patient 120, and one or more external devices 130 according to various embodiments. It is a figure. The external device 130 can communicate with the CRM system 115 implanted in the patient 120. In the embodiment shown in FIG. 1, the CRM system 115 includes a pulse generator (PG) 140 and a lead wire 150. During normal device operation, the PG 140 is therapeutic to the patient's heart 160 for the provision of at least one of tachycardia ventricular fibrillation, anti-bradycardia pacing, anti-bradycardia pacing, or any other type of treatment. It is configured to deliver electrical stimulation.

Thus, in the embodiment of the figure, the PG140 may be a device such as, for example, an ICD, a cardiac resynchronization therapy device with defibrillation function (CRT-D device), or an equivalent device. The PG140 can be implanted in the pectoral muscles inside the body, typically in a position such as the patient's chest. In some embodiments, the PG140 may be implanted in or near the abdomen.

The external device 130 may be a local or remote terminal or other device (eg, at least one of a computing device or a programming device) capable of operating to communicate with the PG 140 from a location outside the patient's body. According to various embodiments, the external device 130 may be any device outside the patient's body that is telemetric and capable of communicating with the PG 140. Examples of external devices include, but are not limited to, programmers (PRMs), home monitoring devices, personal computers with telemetry devices, MRI scanners with telemetry devices, manufacturing inspection equipment, or pen scanners ( wand) can be mentioned. In some embodiments, the PG 140 communicates with the remote terminal 130 via a wireless communication interface. Examples of wireless communication interfaces include, but are not limited to, radio frequency (RF) interfaces, inductive interfaces, and acoustic telemetry interfaces.

FIG. 2A is a more detailed schematic of a CRM system 115 with an exemplary PG140 equipped with a lead 150 implanted in the patient's body. In the embodiment of the figure, the CRM system 115 comprises a PG implanted near the patient's heart 160 and a lead 150 whose distal portion is implanted inside the patient's heart 160. As seen in FIG. 2A, the heart 160 comprises a right atrium 210, a right ventricle 220, a left atrium 230, and a left ventricle 240.

The lead 150 has a flexible body 200 with a proximal region 205 and a distal region 250. As shown, the lead 150 is coupled to the PG 140 and the tip region 250 of the lead body 200 is at least partially implanted in the right ventricle 220 at a desired location. As further shown, the lead 150 comprises at least one electrode 255 along the tip region 250 so that the electrode is located inside the right ventricle 220 when implanted as shown in FIG. 2A. It has become. As described and illustrated in more detail below, the leads 150 are used to transmit an endogenous cardiac signal from the heart 160 to the PG 140, and also to the heart 160 via electrodes 255 with an electric shock or low voltage. One or more conductor coils (not visible in FIG. 2A) inside the lead body 250 that electrically couples the electrodes 255 to the circuit configuration to transmit the pacing stimulus, and other electrical components inside the PG140. I have.

The exemplary embodiment shows only a single lead 150 inserted into the patient's heart 160, whereas in other embodiments multiple leads are used to electrically stimulate other areas of the heart 160. It may be used. In some embodiments, for example, the distal end of a second lead (not shown) may be implanted in the right atrium 210. In addition, or as an alternative, another lead may be implanted on the left side of the heart 160 (eg, coronary vein, left ventricle, etc.) to stimulate the left side of the heart 160. In addition to, or as an alternative to, the leads 150 shown in FIGS. 1-2, other types of leads, such as epicardial leads, may be utilized.

During operation, the lead 150 transmits an electrical signal between the heart 160 and the PG 140. For example, in embodiments where the PG 140 has a pacing function, the lead 150 can be used to transmit an electrical therapeutic stimulus for pacing the heart 160. In embodiments where the PG 140 is an ICD, the lead 150 is available to deliver a high voltage electric shock to the heart 160 via the electrode 255 in response to an event such as ventricular fibrillation. In some embodiments, the PG140 has both a pacing function and a defibrillation function.

FIG. 2B is a schematic diagram showing a simplified equivalent circuit 260 for the lead 150 of FIG. 2A, representing the RF energy captured on the lead 150 from the RF electromagnetic energy generated by the MRI scanner. As shown in FIG. 2B, the voltage (Vi) 265 of circuit 260 represents an equivalent energy source captured by the lead 150 from the MRI scanner. During magnetic resonance imaging, the length of the lead 150 functions like an antenna and receives RF energy transmitted from the MRI scanner into the body. The voltage (Vi) 265 in FIG. 2B may represent, for example, the resulting voltage received from RF energy by the lead 150. The RF energy captured by the leads 150 can be, for example, due to the RF rotating magnetic field generated by the MRI scanner, which creates an electric field on a plane perpendicular to the rotating magnetic field vector in the conductive tissue. The tangential components of these electric fields along the length of the lead 150 are associated with the lead 150. Therefore, the voltage (Vi) 265 is equal to the integral of the tangential electric field along the length of the lead wire 150 (ie, the line integral of the electric field).

The Zl parameter 270 of circuit 260 represents the equivalent impedance indicated by the lead 150 at the RF frequency of the MRI scanner. The impedance value Zl 270 is, for example, the inductance resulting from the parallel inductance and coil turn capacitance indicated by the lead 150 at the 64 MHz RF frequency of a 1.5 Tesla MRI scanner or the 128 MHz RF frequency of a 3 Tesla MRI scanner. It can represent the equivalent impedance. The impedance Zl of the lead wire 150 is a complex quantity having a real part (that is, a resistance) and an imaginary part (that is, reactance).

Zb275 of circuit 260 can represent the impedance of body tissue at the lead contact point. Zc280 can then represent the capacitive coupling of the lead 150 to the surrounding body tissue along the length of the lead 150, where the high frequency current (energy) is the surrounding tissue at the RF frequency of the MRI scanner. May provide a route to leak to. Minimizing the absorbed energy (represented by the energy source Vi265) reduces the energy transferred to the body tissue at the point of contact of the lead with the body tissue.

As further seen in FIG. 2B, the lead 150 has a certain amount of leakage to the surrounding tissue at the RF frequency of the MRI scanner. As further indicated by 275, there is also an impedance at the point of contact of the lead electrode 255 to the surrounding body tissue inside the heart 160. The resulting voltage Vb delivered to the body tissue is: Vb = Vi Zbe / (Zbe + Zl) (Zb in parallel with Zbe = Zc in the formula) Can be related by.

The temperature at the tip of the lead 150, which is typically in contact with the surrounding tissue, is related to the power dissipated in part at 275 (ie, at "Zb"), which power is related to the square of Vb. .. To minimize the temperature rise due to the power dissipated at 275, thus minimize Vi (265) and Zc (280) while maximizing the impedance Zl (270) of the lead 150. Is desirable. In some embodiments, the impedance Zl (270) of the lead 150 may be increased at the RF frequency of the MRI scanner, which helps reduce the energy dissipated into the surrounding body tissue at contact point 275. It becomes.

In various embodiments described in more detail below, the impedance of the lead 150 can be increased by the addition of inductance to the lead 150, or by at least one of the appropriate construction techniques. For example, in various embodiments, the inductance of the lead 150 increases the average diameter of the conductor coil or reduces the pitch of the conductor coil used to supply electrical energy to the electrode 255. Increased by at least one of them. A decrease in coil pitch can result in an increase in capacitance between successive turns of the coil (ie, capacitance per turn of the coil). A parallel combination of inductance (due to the spiral shape of the coil) and per-turn capacitance constitutes a resonant circuit. For a spirally wound lead construction, the spiral coil acts as an inductor if the resonant frequency of the lead exceeds the RF frequency of the MRI. For inductors, at least one of an increase in the cross-sectional area of the coil area or a decrease in the coil pitch increases the inductance, resulting in an increase in the impedance of the lead 150.

FIG. 3 illustrates in more detail an exemplary lead 150 that can be used according to one or more embodiments of the present invention. In FIG. 3, a portion of the lead body 200 is shown in a partially cut-out view to better show the inner profile of the lead 150. As shown in FIG. 3, the lead body 200 comprises a proximal end 302, the lead 150 further comprises a connector assembly 310 coupled to the proximal end 302 of the lead body, for high voltage shock. It includes a conductor coil 320, a shock coil 330, an inner conductor coil 340, a coupler 350, and a pace / sense electrode 360. Depending on the functional requirements of the IMD140 (see FIG. 1) and the therapeutic needs of the patient, the tip region may include at least one of an additional shock coil (not shown) or a pace / sense electrode. .. For example, in some embodiments, a pair of coil electrodes can be used to function as shock electrodes to provide a defibrillation shock to the heart 160.

In the embodiment shown in the figure, the connector assembly 310 includes a connector body 365 and terminal pins 370. The connector assembly 310 may be coupled to the lead body and configured to mechanically and electrically couple the lead to the header of the PG 140 (see FIG. 1). In various embodiments, the terminal pin 370 extends from the connector body 365 towards the proximal end and in some embodiments couples to an inner conductor coil 340 extending longitudinally through the lead body 200 to the pace / sense electrode 360. Will be done. In the embodiment shown, the pace / sense electrode 360 is the tip electrode at the most distal end of the lead 150 and is fixed with respect to the lead body 200 such that the lead 150 is considered a passive fixed lead. .. In other embodiments, the lead 150 may include additional pace / sense electrodes located more proximally along the lead 150. In some embodiments, the terminal pin 370 comprises an opening through the terminal pin communicating with the lumen defined by the inner conductor coil 340 to accommodate the guide wire or insertion stylet. Can be done.

In some embodiments, the pace / sense electrode 360 may be in the form of an electrically active fixed spiral at the distal end of the lead 150. In various such embodiments, the pace / sense electrode 360 is a mechanism that is an expandable / retractable spiral that facilitates longitudinal transition of the spiral to the lead body as the spiral rotates. It may be a supported spiral. In those embodiments, the terminal pin 370 is such that the rotation of the terminal pin 370 with respect to the lead body 200 rotates the inner conductor coil 340 and thus the spiral pace / sense electrode 360 with respect to the lead body 200. It may be rotatable with respect to the connector body 365 and the lead body 200 so as to shift in the longitudinal direction. Various mechanisms and techniques for providing expandable / retractable fixed spiral assemblies (electrically active and passive) are known to those of skill in the art and do not need to be described in more detail herein. ..

The Pace / Sense electrode 360 (whether a solid chip electrode as shown in FIG. 3 or an active fixed spiral as described above) is of any suitable conductive material such as Elgiloy®, MP35N®. , Tungsten, tantalum, iridium, platinum, titanium, palladium, stainless steel, and alloys of any of these materials.

The inner conductor coil 340 may be a relatively low voltage conductor carrying pacing and sensing signals to and from the heart 160. The low voltage inner conductor coil 340 can be formed from one or more substantially cylindrically wound filers, according to various embodiments. As described in more detail below, in some embodiments, the low voltage inner conductor coil 340 reduces the RF current induced in the inner conductor coil 340 by an external MRI magnetic field, and even the desire of the heart. It is configured to have an inductance value of 0.0079 μΗ / mm (0.2 μΗ / inch) or higher to prevent unreasonably high speed irritation. In some embodiments, the inductance value is approximately 0.020 μΗ / mm (approximately 0.5 μΗ / inch). In addition, the inner conductor coil 340 is configured to have a DC resistance of less than 200 ohms in some embodiments.

In some embodiments, the high voltage conductor coil 320 is a high voltage path capable of delivering up to 1000 volts and 40 J of energy to the patient's heart 160 as needed to apply an anti-tachycardia electric shock. Can be provided. The high voltage conductor coil 320 is configured to have high inductance in various embodiments to reduce the current induced by the RF pulse generated by the MRI device or other system. In some embodiments, the inductance is 0.0039 μΗ / mm (0.1 μΗ / inch) or greater. In some embodiments, the outer diameter may be increased to compensate for the loss of inductance. According to one or more embodiments, the high voltage conductor coil 320 may have a multiple filer structure to reduce DC resistance. In some embodiments, the DC resistance is less than approximately 10 ohms (eg, 6 or 7 ohms in some embodiments) to allow maximum energy to be delivered to the heart.

In some embodiments, the high voltage coil 320 can be split into two paths; one path can be connected to the shock coil located proximal to the ICD. Another path may be connected to the shock coil on the tip side of the ICD. The shock coil on the tip side, together with the high voltage coil 320, can serve as a feedback path for the pacing pulse in bipolar pacing. As another example, a second high voltage path may be provided via a high voltage coil (not shown) separated from the high voltage coil 320.

In some embodiments, the high voltage conductor coil 320 is mechanically and electrically coupled to the shock coil 330 via a coupler 350. This path can also serve as a feedback path for the pacing pulse in bipolar pacing. The shock coil 330 can also deliver the appropriate treatment to the patient's heart. Examples of treatments include, but are not limited to, tachycardia ventricular fibrillation, anti-bradycardia pacing, anti-tachycardia pacing, or at least one of other types of treatment.

In some embodiments, the shock coil 330 can have a coating configured to control (ie promote or prevent) the inward growth of tissue. In various embodiments, the lead may include only a single coil electrode, such as the shock coil 330. In other embodiments, the lead 150 may include one or more ring electrodes (not shown) along the lead body in place of or in addition to the shock coil electrode 330. .. If present, the ring electrode can act as a relatively low voltage pace / sense electrode. As a matter of course to those skilled in the art, a wide variety of electrode combinations can be incorporated into the lead 150 within the range of various embodiments of the present invention.

FIG. 4 shows a cross-sectional view 400 of the lead wire 150 obtained along line 4A of FIG. As shown in FIG. 4, in the embodiment shown in the drawing, the high voltage conductor coil 320 and the low voltage inner conductor coil 340 are coaxially arranged inside the lead wire main body 200. As further shown, in the embodiments in the figure, the lead wire 150 is an insulator layer between the high voltage conductor coil 320 and the low voltage inner conductor coil 340 so as to electrically separate these coils from each other. It is equipped with 410. In various embodiments, the individual filer of at least one of the high voltage conductor coil 320 or the low voltage inner conductor coil 340 is in addition to or instead of using the insulator layer 410. They may be individually insulated. Therefore, in the embodiment shown in FIG. 4, the filers of the high voltage conductor coil 320 and the low voltage inner conductor coil 340 each have a thin layer of insulator. In other embodiments, the filers of at least one of the high voltage conductor coil 320 and the low voltage inner conductor coil 340 are not individually insulated and are spaced apart to avoid contact with adjacent filers. Will be done.

Examples of the types of insulating materials that can be used in various embodiments of the present invention include, but are not limited to, silicones, polytetrafluoroethylenes, stretched polytetrafluoroethylenes, ethylene-tetrafluoroethylenes, and the above. Copolymers of. In some embodiments, the insulating layer of the individual filers prevents the turns of the coils from coming into contact with each other when the unwound leads are placed in a spiral form as shown in FIGS. 5A-5C. can do. In addition, some embodiments include a sufficient insulating layer between the low voltage coil and the high voltage coil to prevent electrical coupling.

As described above, according to various embodiments of the invention, at least one of the high voltage conductor coil 320 or the low voltage inner conductor coil 340 is normal (eg, for the provision of anti-tachycardia therapy). It is selectively configured to have high impedance to minimize the effects of applied MRI irradiation without unduely affecting electrical performance under operating conditions. As described in more detail below, in various embodiments, at least one of the filer thickness, pitch, or average coil diameter for at least one of the high voltage conductor coil 320 or the low voltage inner conductor coil 340. One is selectively selected to provide the desired balance of electrical operating performance and MRI compatibility.

5A-5C show different configurations of the inner conductor coil 340, the high voltage conductor coil 320, and the shock coil 330, respectively, according to some embodiments of the present invention. According to various embodiments, the pitch of the helix is the width of one complete helix rotation measured along the axis of the helix. The distances 510a to 510c in FIGS. 5A to 5C indicate the pitch of the coils in the figure, the reference numbers 520a to 520c represent the filer thickness of each coil, and the reference numbers 530a to 530c represent the average coil diameter. According to one or more embodiments, the pitch may be constant along the length of the lead (see, eg, FIG. 5C) or may follow a pattern that repeats along the length of the lead (see, eg, FIG. 5C). See, for example, FIGS. 5A and 5B). In some embodiments, ribbon conductors may be used in the high voltage conductor coil 320 and the shock coil 330. In some embodiments, the coils 320, 330, 340 have the same pitch direction.

FIG. 5A shows a portion of the high voltage conductor coil 320 according to some embodiments of the present invention. In the embodiment shown in the figure, the high voltage conductor coil 320 is a coil of a quad filer. However, in one or more embodiments, the high voltage multiplex filer outer coil 320 can have other types of multiplex filer structures. The multiple filer structure of the high voltage conductor coil 320 can be formed from two or more substantially cylindrically wound filers, for example producing a relatively low DC resistance of less than about 10 ohms. Such a structure may make the high voltage conductor coil 320 suitable for use in high voltage defibrillation lead applications.

In various embodiments, the high voltage multiplex filer outer coil provides the desired coil inductance when the high voltage multiplex filer outer coil 320 is subjected to a high frequency (eg, 40 MHz to 300 MHz) electromagnetic field in the range typical of MRI scans. It can have pitch 510a and filer thickness 520a of various dimensions to produce a value (eg 0.0079 μΗ / mm (0.2 μΗ / inch) or greater). In some embodiments, the desired coil inductance value is approximately 0.020 μΗ / mm (approximately 0.5 μΗ / inch). As discussed above (see, eg, the discussion in FIG. 2B), the impedance and inductance of the lead 150 can be advantageously adjusted by selecting various structural features of the lead. Examples of structural features include, but are not limited to, pitch 510a, filer thickness 520a, coil diameter 530a, and the like.

For a typical cylindrically tightly wound coil, the coil inductance per unit length is: L μ_０πa^２/ 4b^２N^２Can be approximated using, and in the above equation, μ_０Is the magnetic permeability of the free space, a is the average diameter of the coil 530a, b is the pitch 510a of the coil (that is, the distance between adjacent filers), and N is the total number of filers. Based on the above equation, the coil inductance per unit length is proportional to the square of the radius and inversely proportional to the square of the pitch and the total number of filers.

FIG. 5B shows a portion of the high voltage shock coil 330 according to some embodiments of the present invention. In the embodiment shown in the figure, the high voltage shock coil 330 is a trifilar coil. However, in one or more embodiments, the high voltage shock coil 330 can have other types of multiple filer structures. The multiple filer structure of the high voltage shock coil 330 provides a relatively low DC resistance and can be formed from two or more substantially cylindrically wound filers. Such a structure may make the high voltage shock coil 330 suitable for use in high voltage defibrillation lead applications.

In some embodiments, the third coil or shock coil 330 may have a first end connected to the distal region of the high voltage multiplex filer outer coil 320 via a coupler 350. The third coil 330 may be formed from two or more substantially cylindrically wound filers in some embodiments. According to various embodiments, the filer thickness, pitch 510b, and average coil diameter 520b are when the shock coil 350 is subjected to a high frequency (eg, 40 MHz to 300 MHz) electromagnetic field in the range characteristic of MRI scanning. The shock coil 330 can be configured to have a high impedance value. As discussed above (see, eg, discussion in FIG. 2B), the impedance and inductance of the lead 150 can be advantageously adjusted by selecting various structural features of the lead. Examples of structural features include, but are not limited to, pitch, filer thickness, coil diameter and the like.

FIG. 5C shows a portion of the low voltage inner coil 340 according to some embodiments of the present invention. In the embodiment in the figure, the low voltage inner coil 340 is a single filer coil. However, in one or more embodiments, the low voltage inner coil 340 can have other types of multiple filer structures (eg, 2 filers, 3 filers, etc.). The single filer construction of the low voltage inner coil 340 has a higher DC resistance, eg a DC resistance of approximately 200 ohms. Such a structure may make the low voltage inner coil 340 suitable for use in pacing applications.

In some embodiments, the inner conductor coil 340 is divisible into two paths, one for the cathode and one for the anode for the pacing pulse. In one embodiment, the inner conductor coil 340 has a pitch 510c, filer thickness 520c and average having the desired impedance value in the coil when the inner conductor coil 340 is subjected to a range of high frequencies (eg 40MHz to 300MHz). It has a coil diameter of 530c. As discussed above (see, eg, discussion in FIG. 2B), the impedance and inductance of at least one of the lead 150 or the lead coil can be determined by selecting various structural features of the lead. It is adjustable in an advantageous manner. Examples of structural features include, but are not limited to, pitch, filer thickness, coil diameter and the like.

In one embodiment, the high voltage conductor coil 320 has a pitch 510a of about 0.25 mm (about 0.010 inch), a total of four filers, and an average coil diameter of about 1.3 mm (about 0.050 inch) 530a. It has a coil inductance value of about 0.0051 μΗ / mm (about 0.13 μΗ / inch). Therefore, the lower limit for the high voltage coil is set to 0.1 μΗ in one embodiment. The inner conductor coil 340, in certain embodiments, has a pitch 510c of about 0.13 mm (about 0.005 inch), a total of 1 filer, and an average coil diameter of about 0.58 mm (about 0.023 inch). It produces a coil inductance of about 0.020 μΗ / mm (about 0.5 μΗ / inch) per unit length. The lower limit for the low voltage coil can be set to approximately 0.2 μΗ in some embodiments. In some embodiments, the inductance limits of the low voltage coil and the high voltage coil may be different, and in other embodiments the inductance limits may be the same.

As discussed above, the design of various embodiments of the invention can result in significant heat reduction over conventional lead design when exposed to MRI-related frequencies. In one exemplary embodiment, the test sample can have a single filer low voltage coil made from wire with an outer diameter of approximately 0.10 mm (approximately 0.004 inch). The outer diameter of the coil is about 0.69 mm (about 0.027 inch), and the pitch of the coil is about 0.10 mm (0.004 inch). The test sample further has a 4-filer high voltage coil made from wire of approximately 0.25 mm (approximately 0.010 inch). The high voltage coil has an outer diameter of approximately 2.3 mm (approximately 0.090 inch) and the coil pitch is approximately 0.30 mm (approximately 0.012 inch).

FIG. 6 shows the temperature rise that occurs when standard lead designs and example lead designs are applied to frequencies associated with MRI. The total length of the prototype (test mule) is 60 cm. Heating tests for standard lead designs and actual lead designs were performed under the same 64 MHz test conditions. As can be seen in FIG. 6, the actual lead design results in a temperature rise at the tip that is approximately 10 degrees less than the temperature rise of a standard lead. In addition, the actual lead design results in a temperature rise of approximately 4 degrees less than the standard lead temperature rise at the ring electrode.

Although the above embodiments describe and illustrate multi-conductor leads with coil conductors configured coaxially, the high inductance conductor coils 320, 340 are used favorably in other lead configurations within the scope of the present invention. It is also possible to do. For example, FIG. 7 shows a cross section of another embodiment of a lead wire 150 that utilizes a multi-lumen lead wire body as is commonly used in conventional defibrillation lead wires. As shown in FIG. 7, the lead wire body includes an inner tubular member 710 and an outer tubular member 720 disposed on the surface of the inner tubular member 710 and joined to the tubular member. Tubular members 710, 720 can be made from any number of flexible and biocompatible insulating materials, such as, but not limited to, polymers such as silicones and polyurethanes, and copolymers thereof. As further shown, the inner tubular member 710 comprises a plurality of lumens 730, 740, 750, with conductors 760, 770 and 780 arranged in the lumens 730, 740 and 750, respectively. Each conductor 760, 770 and 780 extends longitudinally inside the lumens 730, 740 and 750, respectively, and is electrically coupled to an electrode (eg, electrode 360 in FIG. 3) and to the electrical contacts of the connector assembly 310. Will be done.

In addition, the inner tubular member 710 may include more or fewer lumens depending on the particular configuration of the lead 150. For example, the inner tubular member 710 accommodates at least one of the additional conductor wires or electrode coils inside the lead 150 to supply current to at least one of the other shock coils or pace / sense electrodes. It may have more lumens to do so.

In the embodiment of FIG. 7, the conductor 760 is configured in substantially the same manner as the coil conductor 320 described above, and can operate as the pace / sense circuit for low voltage as described above. Therefore, the conductor 760 advantageously has the same high inductance characteristics as described above for the conductor 320. In the embodiments in the figure, conductors 770, 780 are used in high voltage applications to supply defibrillation stimuli to high voltage shock coils, such as the shock coil 330 in FIG. It is a well-known stranded cable conductor.

Various embodiments of the lead 150 described above advantageously minimize the induced current in the lead conductor due to exposure to an external MRI electromagnetic field. This is in contrast to conventional ICD lead systems that utilize stranded cable conductors to transmit shock current from the PG to the shock electrodes. While such cable conductors provide excellent electrical performance for delivering anti-tachycardia therapy, stranded cable conductors also have lower impedance and are therefore exposed to alternating electromagnetic fields as present during MRI scans. It is easy to generate an induced current when it is done. The high impedance conductor configuration of the lead 150 described above minimizes the effects of MRI irradiation while also providing adequate electrical performance for use in anti-tachycardia therapy applications.

Various modifications and additions can be made to the typical embodiments discussed without departing from the scope of the invention. For example, while the embodiments described above represent specific features, the scope of the invention also includes embodiments with various combinations of features and embodiments that do not necessarily include all of the described features. Accordingly, the scope of the invention is intended to include all such alternative, modified and modified forms within the scope of the claims, along with all of their equivalents.