THERAPY FOR ELECTRODE FAULTS

Description

[0001] The invention relates to an implantable medical device for defibrillating the heart of a patient and a method for controlling such a medical device.

[0002] These implantable medical devices are also known as implantable cardioverter-defibrillators (ICDs). Such a device is designed to detect ventricular fibrillation in the patient's heart and treat it by delivering an electrical shock or pulse.

[0003] A problem with implantable medical devices with defibrillation functions is that, due to the comparatively high voltage required to generate a current pulse, a failure in the insulation of an electrode can lead to high-voltage arcing, resulting in a very high fault current. Current ICDs have electronic short-circuit protection for this eventuality, so the ICD does not suffer any component damage in the event of a short circuit and can continue to perform its diagnostic and therapeutic functions, although with the limitation that high-voltage therapy remains ineffective.

[0004] In this regard, US2010228307 describes a reduction in shock energy in the ICD when electrode defects are detected, in order to prevent a voltage arc from the electrode defect to the device housing.

[0005] Furthermore, it is known in the prior art to switch the shock electrode configuration or shock path for subsequent treatment attempts in the event of a detected short circuit in the shock electrode path, provided a so-called dual-coil electrode is used. Dual-coil electrodes have a right ventricular shock coil (RV coil) and a second shock coil in the superior vena cava (SVC coil). Various shock paths can be selected between the RV coil, the SVC coil, and the implant housing. See Swerdlow et al., "Implantable Cardiac Defibrillator Lead Failure and Management," JOURNAL OF THE AMERICAN COLLEGE OF CARDIOLOGY, VOL. 67, NO. 11, 2016. A device according to the preamble of claim 1 is known from US 7,031,773 B1.

[0006] The failure of high-voltage therapy due to short-circuit protection is undesirable, as it may prevent the patient from receiving necessary treatment. Ideally, high-voltage therapy / defibrillation should be available to the patient even in the aforementioned fault scenario, and this should not be limited by the use of a specific shock electrode.

[0007] The invention is therefore based on the objective of creating an implantable medical device for defibrillating a patient's heart which, in the event of an insulation defect of a defibrillation electrode with short-circuit detection and triggering of the short-circuit protection in the device, is nevertheless able to carry out further therapeutic attempts which have an increased probability of success in this situation for terminating a life-threatening ventricular tachyarrhythmia.

[0008] Furthermore, the invention is based on the objective of providing a corresponding method for controlling such an implantable medical device.

[0009] These problems are solved by an implantable medical device having the features of claim 1 and by a method having the features of claim 7.

[0010] Preferred embodiments of these aspects of the invention are specified in the corresponding dependent claims and are described below.

[0011] According to claim 1, an implantable medical device is disclosed which is designed for defibrillating the heart of a patient and further comprises: an energy storage device comprising at least two capacitors for providing a voltage, at least one electrode for delivering an electric current pulse by means of the voltage, and a short-circuit protection device configured to trigger in the event of a short circuit of the at least one electrode and to interrupt or prevent the delivery of an electric current pulse, wherein the implantable medical device is configured to cause, in the event of a short circuit, the delivery of a further current pulse, in particular by means of a reduced voltage, from a parallel connection of the at least two capacitors.

[0012] Reduced voltage means that the subsequent current pulse is delivered at a voltage that is lower than the voltage of the aborted or prevented current pulse.

[0013] The invention thus enables the delivery of an adapted high-voltage therapy attempt (defibrillation) in the event of an existing electrode defect in the high-voltage therapy pathway, by preferably reducing the therapy voltage in such a way that a higher probability of therapeutic success results in this situation.

[0014] The solution according to the invention has the advantage that the therapy or shock voltage can be reduced compared to that of a normal defibrillation shock, but the administered shock energy remains essentially the same.

[0015] The invention can, in particular, exploit the mechanism of a typical short circuit in the defibrillation path of the device: As a rule, in the case of an insulation defect in the electrode used for shocking, there is no purely metallic contact between the high-voltage conductors or components, but rather a voltage flashover or arc occurs at the moment of high-voltage delivery. The probability of such a flashover increases with the maximum voltage applied and can therefore be reduced by reducing the maximum voltage in subsequent treatment attempts, but only to the extent that a sufficient therapeutic success is still possible.

[0016] Furthermore, according to a preferred embodiment of the implantable medical device according to the invention, the implantable medical device has a detection device which is configured to detect the triggering of the short-circuit protection and to signal a control unit of the implantable medical device, wherein the control unit is configured to emit the further current pulse with the preferably reduced voltage in the event of a detected triggering of the short-circuit protection.

[0017] Furthermore, according to one embodiment of the invention, the control unit is designed to initiate a switchover of the series connection of capacitors to the parallel connection of at least two capacitors in the event of a detected tripping of the short-circuit protection. In this way, for example, the total voltage applied to the two series-connected capacitors can be reduced to a lower voltage applied to the now parallel-connected capacitors.

[0018] Furthermore, according to a preferred embodiment of the implantable medical device according to the invention, the at least one electrode of the implantable medical device is designed to be inserted into a heart chamber of the patient via a vein (i.e., the medical device is a so-called transvenous cardioverter-defibrillator).

[0019] Furthermore, according to a preferred embodiment of the implantable medical device according to the invention, the at least one electrode of the implantable medical device is designed to be implanted subcutaneously, in particular above the sternum of the patient.

[0020] Furthermore, according to a preferred embodiment of the implantable medical device according to the invention, the at least one electrode of the implantable medical device is designed to be implanted substernally (i.e., under the patient's sternum).

[0021] The implantable medical device preferably has a housing for accommodating the at least two capacitors or the energy storage device, as well as, in particular, the other components (e.g., short-circuit protection and / or control unit and / or detection device). The at least one electrode is connected to the housing.

[0022] In the case of a subcutaneous or transvenous electrode, the housing may be designed, for example, to be implanted in the patient's chest (e.g., on the left side of the rib cage, below the armpit). The housing of a substernal electrode can also be implanted in the patient's chest.

[0023] Another aspect of the invention relates to a method for controlling an implantable medical device (in particular an implantable medical device according to the invention), comprising the steps of: Providing a voltage by means of at least two capacitors of the implantable medical device to deliver a current pulse, and terminating or preventing the delivery of the electrical current pulse in the event of detection of a short circuit of an electrode of the implantable medical device, as well as delivering a further current pulse from a parallel circuit of the at least two capacitors.

[0024] According to a preferred embodiment of the method according to the invention, it is provided that a short-circuit protection of the implantable medical device is triggered in the event of a short circuit of an electrode, thereby interrupting or preventing the emission of an electrical current pulse by means of the implantable medical device, wherein, in particular, in the event of a short circuit, the emission of the further current pulse takes place from the parallel connection of the at least two capacitors.

[0025] Furthermore, according to a preferred embodiment of the method according to the invention, it is provided that the triggering of the short-circuit protection is automatically detected by means of a detection device, wherein the detection device signals the triggering of the short-circuit protection to a control unit of the implantable medical device, and wherein the control unit, in the event of a detected triggering of the short-circuit protection, initiates the emission of the further current pulse.

[0026] According to a preferred embodiment of the method according to the invention, in the event of a short circuit, the implantable medical device automatically initiates a switch from a series connection of capacitors to a parallel connection of at least two capacitors (e.g., by the control unit) and then initiates the delivery of the further current pulse.

[0027] In the following, embodiments of the invention, as well as further features and advantages of the invention, will be explained with reference to the figures. The figures show: Fig. 1 a schematic representation of a typical failure mechanism of the implantable medical device that can lead to a short circuit of an electrode of the device; Fig. 2 a reduction of the voltage of the medical device to generate an electrical current pulse for defibrillation; Fig. 3 a schematic representation of the switching between a series connection of the capacitors of the implantable medical device and a parallel connection of the capacitors to reduce said voltage; and Fig. 4 another possibility for reducing the voltage for defibrillation.

[0028] In the Figure 1Figure 1 illustrates a typical failure mechanism of an insulation defect during defibrillation shock delivery (i.e., delivery of an electrical current pulse) by an implantable medical device 1 according to the invention. The at least one electrode 100 is designed as an electrode lead 100 and, in particular, comprises an electrical conductor 110 and an insulator 120 surrounding it, wherein, in the event of a failure, this insulator 120 exhibits an insulation defect 130. The counter electrode for defibrillation is, in this case, a housing 140 of the implantable medical device 1 or defibrillator 1.

[0029] Since in this arrangement the electrical conductor 110 and the housing 140 typically cannot touch even in the area of ​​the insulation defect 130, this insulation defect cannot be detected by means of a low-voltage measurement, i.e. the so-called painless shock impedance measurement shows no abnormality here.

[0030] However, if high-voltage therapy is delivered via electrode 100 and counter electrode 140, a high-voltage flashover 150 can occur in the area of ​​the insulation defect, resulting in a very high fault current. The implantable medical device 1 therefore has an electronic short-circuit protection device 160 for this fault condition, so that the device 1 does not suffer any component damage in the event of a short circuit and is still able to perform its diagnostic and therapeutic functions, although with the limitation that the high-voltage therapy remains ineffective.

[0031] The short-circuit protection 160 is designed to trigger in the event of a short circuit of the at least one electrode 100 and to interrupt or prevent the emission of an electrical current pulse by the implantable medical device 1. Furthermore, the implantable medical device 1 preferably has a detection device 170 (see Figure 1). Fig. 1), which is configured to detect the tripping of the short-circuit protection 160 and to signal a control unit 180 of the implantable medical device 1, wherein the control unit 180 is configured to initiate a further electrical current pulse from a parallel circuit of at least two capacitors C1, C2 in the event of a detected tripping of the short-circuit protection 160. According to one embodiment of the invention, the control unit 180 or the medical device 1 is configured to switch from a previous series connection of the capacitors C1, C2 to a parallel connection (dashed line between C1 and C2 in ). Fig. 1 ), such that the output of the further current pulse from the parallel circuit occurs with a voltage that is reduced compared to the voltage previously provided for in the series circuit of the capacitors in the case of the aborted or prevented current pulse.

[0032] Figure 2Figure 1 shows a schematic representation of the voltage reduction according to the invention during shock therapy delivery in the event of an insulation defect. The first delivered defibrillation shock or electrical current pulse 200 is delivered with the programmed or maximum voltage U1, which causes a high-voltage flashover 150 in the area of ​​the insulation defect 130, whereupon the shock delivery is terminated by the electronic short-circuit protection 160. The shock energy 240 to be delivered is therefore not effective for defibrillation.

[0033] According to the invention, in this implementation example, after detection of the tripping of the short-circuit protection 160, the maximum voltage is set to a reduced value U2 during the next defibrillation attempt 250 (in particular by switching the capacitors C1 and C2 as described above), so that on the one hand the probability of another high-voltage flashover is reduced, but sufficient shock energy 260 can still be delivered for a likely therapeutic success. If no further high-voltage flashover occurs in this case, the intended defibrillation energy is delivered and the tachyarrhythmia can thus be terminated.

[0034] Figure 3The diagram schematically illustrates the switching of capacitors C1 and C2 described above. First, the defibrillation shock 410, or electrical current pulse, is delivered from a series connection 400 of the two capacitors C1 and C2, which, in the event of a fault, triggers the short-circuit protection 160 (see above). The subsequent shock is then delivered from the parallel connection 420 of both capacitors C1 and C2, which offers the advantage of halving the peak shock voltage, for example, while simultaneously allowing essentially the entire maximum shock energy to be delivered.

[0035] In the Figure 4 Another possibility for reducing the voltage is shown in order to achieve a defibrillation shock delivery with a significantly reduced peak voltage and thus a reduction in the probability of a high-voltage flashover.

[0036] The first shock 310 or electrical current pulse for defibrillation is emitted here from a series circuit 300 of three capacitors C1, C2, C3, whereby this leads to a tripping of the short-circuit protection 160 due to an insulation defect.

[0037] In the subsequent shock or current pulse 330, the tap for shock delivery is now set by means of electronic switching elements (not shown here) only in a series connection 320 of capacitors C2, C3, thus reducing the peak voltage of shock 330 by 1 / 3. In this arrangement, the capacitance resulting from the shock delivery increases and thus the duration of the shock phases is extended, which, with appropriate dimensioning of the capacitances, can lead to higher therapy efficiency with a simultaneously lower shock peak voltage.

[0038] The invention advantageously increases the probability that, in the event of an electrode defect in an implantable medical device / defibrillator, life-saving therapy can still be administered.

Claims

1. An implantable medical device (1) for defibrillating the heart of patient, comprising: - an energy storage device for providing a voltage, - at least one electrode (100), wherein the implantable medical device is configured to deliver an electrical current pulse through said electrode for a defibrillation shock by means of the voltage, characterized by - a short-circuit protection (160) which is configured to be triggered in the event of a short-circuit of the at least one electrode (100) and to interrupt or prevent delivery of an electrical current pulse for a defibrillation shock by said electrode, wherein the energy storage device for providing the voltage comprises at least two capacitors (Cl, C2), wherein, in the event of a short-circuit, the implantable medical device (1) is configured to cause the delivery of a further current pulse for a defibrillation shock with reduced voltage from a parallel circuit of the at least two capacitors (Cl, C2) by said electrode.

2. The implantable medical device according to claim 1, characterized in that the implantable medical device (1) has a detection device (170) which is configured to detect the triggering of the short-circuit protection (160) and to signal it to a control unit (180) of the implantable medical device (1), wherein the control unit (180) is configured to initiate the delivery of the further current pulse in the event of a detected triggering of the short-circuit protection (160).

3. The implantable medical device according to claim 2, characterized in that the control unit (180) is configured, in the event of a detected triggering of the short-circuit protection (160), to switch a series circuit (400) of capacitors (Cl, C2) to the parallel circuit (420) of the at least two capacitors (Cl, C2).

4. The implantable medical device according to any one of the preceding claims, characterized in that the at least one electrode (100) of the implantable medical device (1) is configured to be introduced into a heart chamber of the patient via a vein.

5. The implantable medical device according to any one of the preceding claims, characterized in that the at least one electrode (100) of the implantable medical device (1) is configured to be implanted subcutaneously.

6. The implantable medical device according to any one of the preceding claims, characterized in that the at least one electrode (100) of the implantable medical device (1) is configured to be implanted substemally.