Configuration of pacing output channels

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DESCRIPTION

Stim Output Channel Configuration

Technical field

This patent document is generally in the field of heart rhythm monitoring devices, including, among other things, atrial, ventricular and dual chamber pacemakers.

Background

A heart rhythm control device can electrostimulate excitable heart tissue cells adjacent to the lead electrode coupled to the rhythm control device. The response to myocardial stimulation or capture is a function of the positive and negative charges found on each myocardial cell in the heart. A heart rhythm monitoring device causes depolarization or evokes a response when the energy of the stimulation or other electrical stimulus applied to the myocardium exceeds a threshold value. This threshold value, called the capture threshold, represents the amount of electrical energy that will alter the permeability of myocardial cells to initiate cell depolarization. If the energy of the pacemaker stimulus does not exceed the capture threshold, then the permeability of the myocardial cells will not be altered and therefore depolarization will not occur. If, on the other hand, the energy of the pacemaker stimulus exceeds the capture threshold, then the permeability of the myocardial cells will be altered in such a way that depolarization will occur.

Document US 5843136 discloses an apparatus according to the preamble of claim 1. The object of the present invention is solved by an apparatus according to the independent claim. Preferred embodiments are shown in the dependent claims.

Brief description of the drawings

In the drawings, which are not necessarily drawn to scale, the same reference numerals may describe similar components in different views. The same reference numbers with different letter suffixes can represent different instances of similar components. The drawings generally illustrate, by way of example, but not by way of limitation, various embodiments discussed herein.

Figure 1 shows an example of portions of an implantable heart rate monitoring device, such as to apply stimuli to, or detect intrinsic spontaneous or intrinsic evoked depolarizations from a desired portion of a heart;

Figure 2 shows an example of a stimulation and recharge pulse, along with an example capacitor and switching configuration;

Figure 3 shows an example of a stimulation channel that can be used in a device with multiple stimulation channels; and Figure 4 shows an example of a system for applying electrostimulation to a desired portion of the heart.

Detailed description

Figure 1 shows an example of a portion of an implantable heart rate monitoring device, such as to apply stimuli to, or detect spontaneous intrinsic or evoked intrinsic depolarizations from, a desired portion of a heart 100. Spontaneous intrinsic depolarizations are generated by the heart itself, whereas the evoked intrinsic depolarizations are the result of an electrostimulation pulse, such as a pacing pulse. Depolarization of a chamber of the heart causes it to contract. After contraction, while the heart chamber expands to fill with blood, repolarization takes place.

Figure 1 illustrates an example of a stimulation voltage generator 102, which generates an adjustable voltage that is stored in a stimulation supply capacitor 104. A switch 106 can be used to selectively couple or uncouple the stimulation voltage generator 102 to or from supply capacitor 104. A pacing pulse may be applied to the heart 100, such as through electrodes 108 and 109 (eg, by a lead 110, in certain examples), such as by closing switches 112 and 114. In this example, during application of the stimulation pulse, a coupling capacitor 116 is included in the return path from electrode 109 to ground. Alternatively, coupling capacitor 116 can be configured in series between stimulation supply capacitor 104 and stimulation electrode 108 (not shown). After a non-zero delay period after application of the pacing pulse, such as during repolarization of the heart, a recharge period may begin. During the recharging period, the switch

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112 opens and switches 114 and 115 can be closed to discharge the voltage accumulated during the stimulus pulse from coupling capacitor 116 back to zero.

Figure 2 shows an example of the voltage waveform between electrodes 108 and 109 during stimulation and recharge periods, P and R respectively, along with another illustration of the switching configuration, further including external bypass switches LS that are commonly on except during internal or external defibrillation shocks. (Note: The LS bypass switch may not be present on a bradycardia pacing device, depending on the input protection scheme employed). During a period of stimulation P, switches 112 and 114 are closed. During the recharge period R, switches 114 and 115 are closed.

In the example of Figures 1 or 2, spontaneous or evoked intrinsic depolarizations can also be detected, such as between electrodes 108 and 109, through a detection amplifier channel 118 (which may include a detection amplifier, as well as other components signal processing). The resulting sensed information can be provided to a processor 120, such as for further processing. In this example, processor 120 may access separate or on-board memory 122, such as to read or store information. Processor 120 may also control the operation of other components, such as stimulation voltage generator 102, switches 106, 112, 114, and 115, sense amplifier channel 118, or memory 122.

In an automatic threshold mode, the implantable device can cycle through various stimulation output energies, such as by varying the voltage stored in the stimulation supply capacitor 104, or by varying the time of the stimulation pulse width, during which the energy stored in the stimulation supply capacitor 104 is coupled to the stimulation electrode 108. By automatically determining the applied threshold energy below which response depolarization is no longer evoked, the stimulation output energy can be automatically or manually adjusted to be above the threshold value, such as by a desired safety margin. Similarly, in an automatic capture mode, the implantable device can automatically detect, such as after an applied stimulus, to determine whether the applied stimulus resulted in response evoked depolarization. The pacing output energy can be adjusted automatically, such as above that threshold value, for an extended period of time, or on a beat-by-beat basis.

Therefore, both automatic capture and atrial automatic thresholding may involve detecting an evoked response from the heart shortly after the application of a pacing pulse. A potential challenge in achieving reliable detection of the evoked response signal is a pacing pulse lead polarization artifact (eg, late potential) as observed by electrodes 108 and 109 directly following a stimulus / recharge event. In certain examples where an electrode configuration of the device includes additional electrodes other than electrodes 108 and 109 (such as an additional right ventricular coil electrode and an additional right atrial coil electrode, in a defibrillator device), any evoked response can be detected using said other electrodes; Since such other electrodes are different from those used to apply the stimulus pulse, they can rapidly detect the evoked response without being affected by the late potential observed at electrodes 108 and 109. Such a scheme results in little or no observed stimulus artifact. on the evoked response detection channel.

However, certain bradycardia devices may not have leads available with such separate electrodes to allow such detection of the evoked response to be independent of the electrodes used to deliver the pacing pulse. In such configurations, the detection of the evoked response could potentially be affected by such stimulation artifacts. The present inventors have recognized, among other things, that one way to reduce this artifact is to reduce the capacity of the coupling capacitor 116, such as during such evoked response detection. Examples of evoked response detection are described in US Patent Nos. 6,226,551, 6,427,085, and 5,941,903, each of which is incorporated by reference herein in its entirety, including its description of detection. of the evoked response. As an illustrative example, the stimulus artifact during evoked response detection can be reduced by using a smaller coupling capacitor (e.g. 2.2 pF) 116 during evoked response detection, and by using a larger coupling capacitor (e.g. , 10 pF) 116 during stimulation of non-evoked responses.

Although improved detection visibility of the evoked response signal is provided, however, the value of the lower coupling capacitor can also alter the shape of the stimulation waveform. For example, a smaller coupling capacitor generally results in a more rapid drop in the stimulation pulse amplitude, since the voltage drop between the limit amplitude and the trailing edge amplitude is a function of the constant RC time formed by the pacing supply capacitor 104, coupling capacitor 116, and the series resistance of the heart load and transistorized switches. Therefore, using a lower coupling capacitor value can decrease the amplitude of the trailing edge of the pacing pulse which, in turn, can effectively limit the duration of the useful pacing pulse width. The present inventors have recognized that one solution is to have both a smaller coupling capacitor

ES 2 531 972 T3 (eg 2.2 pF) 116 as a higher coupling capacitor (eg 10 pF), and automatically use the minor coupling capacitor 116 during evoked response detection (such as during auto -threshold, auto-capture, or both), and otherwise automatically use the larger coupling capacitor 116. The present inventors have also recognized that, in a size-limited implantable device, it is possible to use a switching configuration that borrows a coupling capacitor from another stimulation channel, as further described below.

Figure 3 is a block diagram generally illustrating an example of a switching configuration for a particular pacing channel, where the particular pacing channel may be associated with a particular location in the heart to which the energy of the pacing is to be applied. stimulation. In one example, multiple stimulation channels may be individually associated with different locations in the heart where the stimulation energy is to be applied. As an illustrative example, a single chamber pacing to a right ventricle (RV) can use a single pacing channel, as shown in Figure 3. As another illustrative example, a dual chamber pacing to a RV and a Right atrium (RA) can use two such stimulation channels. As a further illustrative example, tri-chamber pacing to an RA, RV, and left ventricle (LV) can use three channels of pacing. Other configurations or more stimulation channels are also possible.

In the example of FIG. 3, in addition to the stimulation supply capacitor 104 and the return coupling capacitor 116, a backup stimulation supply capacitor 300 is also included in a particular stimulation channel. In this example, each of the normal stimulation supply capacitor 104 and the backup stimulation supply capacitor may include separate respective switches 112A and 112B, such as for coupling respectively to a ring electrode during application of a stimulation pulse. bipolar, and to a can electrode (associated with a housing of the implantable device) during the application of the unipolar stimulation pulse.

In an example where multiple such stimulation channels are used, the backup stimulation capacitor 300 from another stimulation channel may be borrowed from a particular stimulation channel for use as its coupling capacitor 116, such as when the auto-capture is not enabled. In fact, even in a single chamber stimulation device with an autothreshold backup stimulation supply, the backup stimulation supply capacitor can be swapped out for the coupling capacitor (for example, when not operating in auto threshold mode. ) to provide wider stimulus pulses. In an illustrative example, an implantable device is assumed to include separate AR, RV, and LV stimulation channels, each including: a 10 pF stimulation delivery capacitor 104, a 2.2 pF coupling capacitor 116, and a 10 pF 300 backup stimulation supply capacitor. Except when VR auto-capture is enabled, the VR stimulation channel can use the RA channel 300's 10pF backup stimulation supply capacitor as its coupling capacitor 116. When VR auto-capture is enabled , the VR stimulation channel uses its own 2.2 pF coupling capacitor 116, rather than borrowing it from another channel. In this example, borrowing the backup supply capacitor 300 from another channel may involve closing a switch (not shown) between the capacitor 300 and the TIP electrode, rather than the switch 114.

In another example, a particular stimulation channel may borrow its own backup stimulation capacitor 300 for use as coupling capacitor 116, rather than borrowing it from another stimulation channel. However, in such an example, backup pacing for that channel is not available, since that channel's own backup pacing capacitor 300 is being used as coupling capacitor 116.

In yet another example, a particular stimulation channel may borrow a coupling capacitor from another stimulation channel 116 for use as its coupling capacitor 116, rather than borrowing a backup stimulation supply capacitor from another stimulation channel. stimulation.

Table 1 below lists an illustrative example of various capacitor configurations used for coupling capacitor 116 in an embodiment where there are three stimulation channels: a VR stimulation channel, an AR stimulation channel, and an LV stimulation channel. Three control bits are coded to select a particular configuration from the eight available in this example.

Table 1: . Coupling Capacitor Configurations

<td>Control bits</td><td>Cond. Used for cond. coupling ra</td><td>Cond. Used for cond. rv coupling</td><td>Cond. Used for cond. coupling iv</td>

<td> 000</td><td>cond. coupling RA 116</td><td>cond. RV coupling 116</td><td>cond. coupling LV 116</td>

<td> 001</td><td>cond. coupling RA 116</td><td>cond. backup RV 300</td><td>cond. coupling LV 116</td>

<td> 010</td><td>cond. RV coupling 116</td><td>cond. coupling RA 116</td><td>cond. coupling LV 116</td>

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<td> 011</td><td>cond. coupling RA 116</td><td>cond. coupling LV 116</td><td>cond. RV coupling 116</td>

<td> 100</td><td>cond. coupling RA 116</td><td>cond. RV coupling 116</td><td>cond. coupling LV 116</td>

<td> 101</td><td>cond. coupling RA 116</td><td>cond. RV coupling 116</td><td>cond. coupling LV 116</td>

<td> 110</td><td>cond. RV coupling 116</td><td>cond. coupling RA 116</td><td>cond. coupling LV 116</td>

<td> 111</td><td>cond. RV coupling 116</td><td>cond. coupling RA 116</td><td>cond. coupling LV 116</td>

Figure 4 shows an example of an apparatus 400 that can be used to deliver one or more electrostimulations to a target. In one example, apparatus 400 may be coupled to a heart 100, such as using electrodes 108 and 109. In one example, an implantable medical device 401 may include a first pacing delivery channel 410, a second pacing delivery channel 420, a processor 120, and electrodes 108 and 109 that can be attached to the heart 100.

In one example, the first electrostimulation channel 410 may include a voltage generator 402, a capacitor module 404, and a switching circuit 408. In one example, the capacitor module 404 may include a stimulation supply capacitor 405 and It may include a flyback coupling capacitor or other capacitor 406.

In one example, the second electrostimulation channel 420 may include a voltage generator 412, a capacitor module 414, and a switching circuit 418. In one example, the capacitor module 414 may include a stimulation supply capacitor 415 and It may include a flyback coupling capacitor or other capacitor 416.

In one example, voltage generator 402 can be coupled to switch circuit 408. In one example, capacitor module 404 can be coupled to switch circuit 408, which, in turn, can be coupled to electrodes 108 and 109, which can be found together with the heart 100. In one example, voltage generator 402 can be configured to generate an electrostimulation voltage and provide an electrostimulation voltage to capacitor module 404, such as by activating switch circuit 408, or otherwise. In one example, capacitor module 404 stores electrostimulation voltage in stimulation supply capacitor 405. In one example, the switching circuit 408 can be used to selectively couple the capacitor module 404, such as during the application of pacing to a desired portion of the heart 100.

In one example, voltage generator 412 can be coupled to switching circuit 418. In one example, capacitor module 414 can be coupled to switching circuit 418, which, in turn, can be coupled to electrodes 108 and 109. In one example As an example, the voltage generator 412 may be configured to generate an electrostimulation voltage and to provide the electrostimulation voltage to the capacitor module 414, such as by activating the switching circuit 418. In one example, capacitor module 414 may store the electrostimulation voltage across stimulation supply capacitor 415. In one example, switching circuit 418 may be configured to selectively couple capacitor module 414, such as during application of the pacing voltage to a desired portion of the heart 100.

In one example, processor 120 is coupled to voltage generators 402, 412 and switch circuits 408, 418. In one example, processor 120 is configured to control switch circuits 408, 418. In one example, processor 120 may configure one of capacitors 415, 416 in capacitor module 414 to be in series with stimulation supply capacitor 405, such as during application of an electrostimulation voltage from the stimulation capacitor. delivery of stimulation 405 to a target portion of the heart 100.

In one example, at least one of the first pacing channel 410 and the second pacing channel 420 may include a single pacing channel for single chamber pacing to a right ventricle (RV). In another example, at least one of the first pacing channel 410 and the second pacing channel 420 may include two pacing channels for dual chamber pacing to a RV and a right atrium (RA). In yet another example, at least one of the first electrostimulation channel 410 and the second electrostimulation channel 420 may include three stimulation channels for three-chamber pacing to an RA, RV, and left ventricle (LV). Other configurations that use more stimulation channels are also possible.

In the example of Figure 4, the switching circuit 408 can be configured to couple the stimulation supply capacitor to an annular electrode, such as during a bipolar stimulation pulse application and to a can electrode (for example, associated with a housing or the attached head of an electronic unit of an implantable device), such as during the application of a unipolar stimulation pulse.

During operation, apparatus 400 can be configured such that a particular channel can take

ES 2 531 972 T3 borrowed a capacitor (e.g., pacing capacitor 414, backup capacitor, or feedback coupling capacitor 416) from an alternate channel during the application of the particular channel of pacing voltage to the heart 100 . In one example, the capacitor is borrowed from capacitor module 414 during the application of an electrostimulation voltage stored in capacitor module 404 to a desired portion of the heart 100, when an auto-capture or automatic threshold mode is disabled. . In one example, this loan may trigger such disabling of automatic capture mode, automatic threshold mode, or other evoked response detection mode. In one example, borrowing the backup capacitor from the capacitor module 414 of the second electrostimulation channel 420 may involve closing at least one or more of the switching circuits 408 or 418.

In one example, the second electrostimulation channel 420 may be configured as an alternate electrostimulation channel. In one example, a particular stimulation channel 410 (for example, an AR stimulation channel) may borrow its own backup stimulation capacitor 415 for use as or with its coupling capacitor 406, such as to modify the value coupling capacitor 406 during electrostimulation, rather than borrowing a capacitor from another stimulation channel (eg, a VR stimulation channel). However, in such an example, the back-up pacing capacitor of that particular pacing channel 415 is being used as the coupling capacitor 406.

In yet another example, a particular stimulation channel 410 (for example, an AR stimulation channel) may borrow a coupling capacitor 416 from another stimulation channel 420 (for example, RV stimulation) for use as its capacitor. coupling 406, rather than borrowing a backup stimulation supply capacitor 415 from the other stimulation channel 420 (eg, the RV stimulation channel).

Additional notes

The detailed description above includes references to the accompanying drawings, which form part of the detailed description. The drawings show, by way of illustration, specific embodiments in which the invention can be practiced. These embodiments are also referred to herein as examples. Such examples may include items in addition to those shown and described. However, the present inventors also contemplate examples in which only the items shown and described are provided.

In this document, the terms one or one are used in the usual way in patent documents, so as to include one or more than one, regardless of any other case or use of at least one or one or more. . In this document, the term or is used to refer to a non-limiting one, such that A or B includes A but not B, B but not A and A and B, unless otherwise indicated. In the appended claims, the expressions including, including and wherein, are used as plain language equivalents of the respective expressions comprising comprising and in which, in which. Also, in the following claims, the terms it includes, including are open, that is, a system, device, article or process that includes elements other than those presented after said term in a claim are considered to still fall within the scope of that vindication. Furthermore, in the following claims, the terms first, second and third, etc. they are used merely as labels, and are not intended to impose numerical requirements on their objects.

The examples of the method described herein described may be implemented, at least in part, on a machine or on a computer. Some examples may include a computer-readable medium or machine-readable medium encoded with operable instructions for configuring an electronic device to perform the procedures described in the previous examples. An implementation of such procedures may include code, for example microcode, assembly language code, a higher level language code, or the like. Such code can include computer-readable instructions to perform various procedures. The code can form portions of computer program products. In addition, the code can be tangibly stored on one or more volatile or non-volatile computer-readable media during execution or at other times. These computer-readable media may include, but are not limited to, hard drives, removable magnetic discs, removable optical discs (for example, compact discs and digital video discs), magnetic cassettes, memory cards or sticks, random access memory (RAM ), read-only memories (ROM), and the like.

The above description is intended to be illustrative and not restrictive. For example, the examples described above (or one or more aspects thereof) can be used in combination with each other. Other embodiments may be used, such as by one skilled in the art after reviewing the above description. The Summary is provided to enable the reader to quickly discern the nature of the technical disclosure. It has been provided with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. Additionally, in the Detailed Description above, various features have been grouped together to expedite disclosure. This is not to be construed to reflect an intention that an unclaimed disclosed feature is essential to any claim. Instead, the subject matter of the invention may

ES 2 531 972 T3 lie in less than all of the features of a particular disclosed embodiment. Therefore, the following claims are hereby incorporated in the Detailed Description, each claim alone being worth a separate embodiment. The scope of the invention is to be determined with reference to the appended claims, together with the full scope of equivalents to which said claims apply.