Implantable medical device for the treatment of atrial tachycardia

Abstract

An implantable medical device for the treatment of atrial tachycardia, wherein the implantable medical device is configured to terminate the tachycardia by delivering the therapy before the expiry of a coagulation timer, wherein the implantable medical device is further configured to temporarily refrain from delivering any further therapy after the expiry of the coagulation timer, and wherein the implantable medical device is further configured to delay a reset of the coagulation timer depending on the episode length of a previously terminated atrial tachycardia episode.

Description

[0001] The present invention relates to an implantable medical device for atrial stimulation of the heart of a human or animal patient, in particular in the form of a cardioverter defibrillator.

[0002] The term coagulation timeout refers to the maximum period of time within which an incipient atrial tachycardia (either in the form of atrial fibrillation (AFib for short), atrial flutter (AFlut for short), or (rapid) atrial tachycardia), hereinafter referred to as "AT," is to be resolved through therapeutic attempts, particularly electrical stimulation of the heart. After this period has elapsed, this information is stored in the system or medical device, and the delivery of atrial therapies is prevented. From this point on, there may be a significantly increased risk of thrombi forming in the atrium, as the AT can alter the mechanical process of atrial contraction and thus the pumping behavior, resulting in poorly perfused volumes.

[0003] Accordingly, the consideration of a coagulation timeout, which usually has a standard value of 48 hours (h), limits the risk of occlusion of capillaries by a thrombus originating from the atrium during prolonged AT.

[0004] The coagulation timer can be controlled via the duration of atrial episodes. An atrial episode is a period of time that begins when an atrial detection criterion is met and ends when a subsequent atrial termination criterion is reached. These criteria are typically formed by X out of Y conditions and thus represent a hysteresis behavior – generally, a continuous atrial tachycardic situation is detected, but several atrial signals in quick succession or undersensing passages caused by very fine signals (low amplitudes) can also be "bridged" in this way. Intracardiac signals from this period, as well as diagnostically and technically relevant parameters, are stored. The episode duration is the time difference between the termination of an atrial episode and the time of detection of this atrial episode.In this regard, atrial tachycardia events of the heart are understood as events with an associated interval length that is shorter than a threshold value (e.g. 300 ms) set by a clinically responsible person (e.g., attending physician).

[0005] An atrial episode can also be terminated by external events. Examples of termination include termination due to programmer activity (e.g., entering a command into a programmer associated with the implantable medical device), a magnetic pad, or an MRI scan. This prevents the coagulation timer from being terminated if atrial tachycardia is still present. If, after the end of the interruption of the atrial episode, a new atrial detection occurs within a hysteresis time, the coagulation timer continues. Otherwise, the coagulation timer is terminated because atrial tachycardia is no longer present (new detection after, for example, T >40 seconds. If no detection occurs within 40 seconds of the end of the interruption, the coagulation timer is set to zero / reset).

[0006] The estimation of the AT situation, which has so far been based primarily on the episode duration - a single atrial episode - can lead to an underestimation of the actual continuous AT divided into several episodes.

[0007] Based on this, the present invention is based on the object of providing an implantable medical device for atrial stimulation of the heart or for treating an atrial tachycardic rhythm situation of the heart, which is configured to execute an algorithm that makes the coagulation timer more robust – particularly for situations in which the atrial sensing conditions are not optimal. In particular, the time measurement relevant for the coagulation timeout, in particular the coagulation timer, should ideally be protected from being reset during short phases between two consecutive atrial episodes.

[0008] The object underlying the invention is achieved by an implantable medical device having the features of claim 1. Preferred embodiments of this aspect of the invention are described below.

[0009] According to claim 1, an implantable medical device, in particular in the form of a cardioverter-defibrillator, for treating an atrial tachycardic rhythm situation is disclosed, wherein the implantable medical device is configured to terminate the tachycardia by delivering the therapy before the expiration of a coagulation timer or to resolve an atrial tachycardic rhythm situation in the process of developing during a period referred to as coagulation timeout by delivering the therapy, wherein the implantable medical device is configured to reduce the risk of occlusion of capillaries by an atrial thrombus after the expiration of the coagulation timer, a further delivery of the therapy after a predefined period (e.g.48h) for an indefinite period of time, preferably at least until the next follow-up, wherein the implantable medical device is configured to delay resetting the coagulation timer depending on the length of the episode of the atrial tachycardic rhythm situation that is already running. In particular, the device can allow the coagulation timeout to continue depending on the length of the episode that is already running and can resume it accordingly upon renewed detection of the same episode type (AT / AF). This is configured by the atrial detection criterion. Specifically, X (e.g., 36) intervals out of Y (e.g., 48) intervals with an interval length of less than Z (e.g., 300ms). In particular, the present invention thereby allows, in addition to existing solutions for external aborts of the coagulation timeout, a hysteresis-like behavior for setting the coagulation timeout status for each possible end of the episode.

[0010] According to one embodiment of the invention, the algorithm provides at least one or a combination of the following input parameters: i) an episode length of a currently open or just terminated atrial episode, ii) an interval length (zone boundary) for atrial tachycardia detection, iii) a detection criterion for atrial tachycardia detection iv) at least one measure of the quality of the atrial signal v) the atrial burden, which corresponds to the daily proportion covered by atrial tachycardias. vi) a mode switch counter vii) the number of sensed atrial events and / or the proportion of paced atrial events to all atrial events in the same period

[0011] The mode switch counter counts the mode switches in a past time period (e.g., one day). A mode switch represents the switchover from atrial-controlled ventricular pacing to atrial signal-independent ventricular pacing. A mode switch is triggered by a corresponding detection criterion, which is implemented, for example, as X out of Y (e.g., 5 out of 8) atrial intervals are faster than the mode switch intervention rate (e.g., 160 bpm). The mode switch intervention rate is lower than the AT detection rate. The mode switch "hysteresis" reacts more "flexibly" (in the sense of more dynamic) to a briefly perceived change in atrial activity. This means that information about atrial activity can be obtained even without the previously described atrial episodes.

[0012] The input parameters for iv) to vii) can each be used as a value representative of a current observation period (e.g. daily value) or as a metric on a short-term trend (e.g. in X out of Y of the last days the mode switch counter was above a threshold value).

[0013] The application of the solution according to the invention allows in particular the use in the following scenarios: According to scenario A, the coagulation timeout status is not yet set (coagulation timer has not yet expired) and an atrial tachycardia episode is currently being terminated.

[0014] According to scenario B, the coagulation timeout status is not yet set (coagulation timer has not yet expired) and a phase of atrial undersensing occurs. As a result, atrial events are often briefly undetected, for example, due to noise or far-field blanking of ventricular events, causing the atrial episode to be falsely terminated and another atrial episode to be detected shortly thereafter. According to one embodiment of the invention, a reset of the coagulation timer should therefore be prevented during a brief episode interruption.

[0015] Scenario C also concerns prolonged paroxysmal atrial tachycardia episodes: The risk of coagulation increases with the duration of an atrial tachycardia rhythm. After the resumption of a regular AV rhythm, coagulation foci can be resolved. This phase can be taken into account by the coagulation timeout hysteresis. According to one embodiment of the invention, it is therefore provided that if paroxysmal atrial tachycardia episodes occur before the hysteresis expires, the coagulation timer is not reset and can reach the coagulation timeout.

[0016] According to one embodiment of the invention, the implantable medical device or the algorithm implemented therein is configured to delay a reset of the coagulation timer with increasing duration of the episode, in order to take into account a recovery phase, particularly after the end of the atrial rhythm situation. Furthermore, according to one embodiment, the implantable medical device or the algorithm implemented therein is configured to determine a hysteresis base duration depending on the currently terminating (individual) episode length, wherein according to one embodiment - for an atrial episode duration of less than 10 minutes, a basic hysteresis duration of 40 seconds is selected, - for an atrial episode duration greater than or equal to 10 minutes and less than 1 hour, a basic hysteresis duration of 8 minutes is selected, - for an atrial episode duration greater than or equal to 1h and less than 12h, a basic hysteresis duration of 2 hours is selected, and - for an episode duration greater than or equal to 12 hours and less than 48 hours, a basic hysteresis duration of 12 hours is selected.

[0017] According to one embodiment, depending on a currently terminating (single) episode length, a basic hysteresis duration up to the set coagulation timeout t_KT (e.g. 48h) is to be determined as follows: − Hysteresis−Basic duration=Episode length*[5…95%]

[0018] If a mode switch is possible, a ratio of the mode switch counter (day counter) to an elapsed time of day (evaluation time) of, for example, greater than 60 / h (i.e. statistically once per minute 5 / 8 mode switch condition is fulfilled) can increase the hysteresis time by a predefined percentage of, for example, 50%.

[0019] This results in a total hysteresis period for which it should be assumed that the AT situation has not yet ended: thysteresis=(1+MMSw)*tbase, where t hysterese the total hysteresis period, t base the said hysteresis basic duration and M MSw the increase of the multiplier with a proportionally high mode switch counter.

[0020] In other words, the implantable medical device or the algorithm implemented therein is configured to extend the coagulation timeout by the period t hysterese to extend.

[0021] According to a further embodiment of the invention, it is provided that in addition the mode switch criterion or the mode switch multiplier M MSw is adjusted, in particular depending on the coagulation time already running on the coagulation timer, whereby - for a coagulation time of less than 10 min the mode switch multiplier M MSw is set to 0.5 (50% of the basic hysteresis duration), - for a coagulation time greater than or equal to 10 min and less than 1h the mode switch multiplier M MSw is set to 0.4 (40% of the hysteresis basic duration), - for a coagulation time greater than or equal to 1h and less than 12h the mode switch multiplier M MSw is set to 0.3 (30% of the basic hysteresis duration), and - for a coagulation time greater than or equal to 12h and less than 48h the mode switch multiplier M MSw is set to 0.2 (20% of the basic hysteresis duration).

[0022] The total hysteresis period t hysterese According to one embodiment, the implantable medical device according to the invention can be used to correct the time measurement of a sustained AT scenario necessary for the coagulation timeout status.

[0023] Furthermore, the implantable medical device can correct the atrial burden calculation. The time bridged per day between (closely) consecutive atrial tachycardia episodes due to the hysteresis condition can be recorded and, if necessary, taken into account for the atrial burden determination.

[0024] Furthermore, according to one aspect of the invention, the implantable medical device can be part of a system that further comprises a programming device. This can display the counter information to a clinically responsible person, in particular in binary form (yes / no) and optionally the number of times (quantitatively) that a gap between two atrial signal segments was detected as "continuous" according to the current sensitivity setting of the algorithm.

[0025] Furthermore, the implantable medical device can be connected to a telemonitoring system that allows the display of the counter information on a daily basis as a trend, if necessary including optional alarms.

[0026] In the following, an embodiment of the invention as well as further features and advantages of the invention will be explained with reference to the figure. It shows: Fig. 1 a schematic representation of an embodiment of the invention.

[0027] The Fig. Figure 1 shows a schematic overview of the components of one embodiment of the inventive solution. The above-described embodiments of the algorithm are implemented in the control unit 213.

[0028] The Fig.The implantable medical device 210 shown in Figure 1 has an electrode 220 with at least two electrode poles 221, 222. The electrode 220 can be positioned, for example, in the right atrium. Voltage signals are derived in the active implant 210 by the vector 223 spanned between the two electrode poles (e.g., tip electrode pole 221 and ring electrode pole 222) and passed through an AD converter as part of the sensing unit 211. These electrode poles 221 and 222 can also be designed as two ring electrode poles, which are additionally located proximally on the electrode. The atrial sensing unit is then supplied by the vector spanned between them. Such an electrode, with its tip-ring electrodes, could be positioned either in the right ventricular apex (classic, apical positioning) or in the right ventricular septum (a possible CSP application).The ring electrode poles 221 and 222 would then be freely floating in the right atrium and would essentially only have a sensing function.

[0029] In the digitized signal, sense events are generated by the sensing unit 212, which are used in the control unit 213 to trigger the delivery of stimuli by the generator 214 when required.

[0030] These stimuli are transmitted to the cardiac tissue via electrodes 221, 222. The parameters of the components of the active implant 210 are configured, in particular, by an external programming device 300, which exchanges information with the communication unit 215 of the active implant 210 via a communication unit 301.

[0031] The present invention makes the application of the coagulation timeout significantly more robust. Alerting clinical staff via a telemonitoring system and programmer becomes even more reliable. If atrial therapies are programmed, they are blocked even more reliably in the event of a risk of coagulation, thus providing more reliable patient protection.

Claims

[1] An implantable medical device for treating atrial tachycardia, wherein the implantable medical device is configured to terminate the tachycardia by delivering the therapy before the expiration of a coagulation timer, wherein the implantable medical device is further configured to temporarily refrain from further delivery of the therapy after the coagulation timer has expired, and wherein the implantable medical device is further configured to delay a resetting of the coagulation timer depending on an episode length of a previously terminated atrial tachycardia episode.

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