System and method for ventricular pacing with av interval modulation

The present invention relates comprehensively to implantable medical devices, and more specifically to implantable medical devices for cardiac pacing.

In providing cardiac pacing, it is preferred to promote intrinsic conduction and depolarization of the ventricles and to reduce or minimize ventricular pacing. Various protocols have been provided to promote endogenous conduction and lead to success to varying degrees. For example, in some modes, programmed AV (atrioventricular) delay is extended and subsequent ventricular pacing is suppressed in response to detecting ventricular events when underlying conduction is present. Will. Although useful, such AV extensions are limited in that the maximum interval available must be matched to the capabilities of traditional pacing schemes. That is, such an AV interval can be defined, for example, in DDD mode or DDDR mode. At any given cardiac cycle, ventricular pacing will be delivered at the end of the AV delay in which no ventricular activity is detected. Therefore, there is a maximum AV delay beyond which ventricular pacing may not be safely delivered in a given cardiac cycle.

<p> According to the protocol of the present invention, and as described in more detail in the patent application incorporated above, even if no ventricular event is detected, one entire cardiac cycle can be performed without the use of ventricular pacing. A mode is provided that allows for good progress. This gives the maximum opportunity for endogenous conduction to occur during a given cardiac cycle. Such protocols are collectively referred to as "managed ventricular pacing " (MPV ) or "ventricular pacing protocol" (VPP).</p><p> In fact, a given VPP that does not provide ventricular pacing allows a given patient to work satisfactorily. That is, as long as endogenous conduction is always present or rarely as tolerated by VPP, a given patient is effective as if in AAIR mode, AAI mode, ADI mode or ADIR mode. Can behave to. Other patients, such as those with complete heart block, may rely on pacemakers and require constant ventricular pacing. In such cases, VPP has no opportunity to reduce ventricular pacing, as its pacing is essential to life. Finally, there are patients who constantly change between the two extreme conditions. These patients may require ventricular pacing, but at other times they will exhibit endogenous conduction at normal or extended intervals.</p><p> In constantly changing patients, VPP will operate in atrial pacing mode when acceptable and will operate in biluminal pacing mode when ventricular pacing is required. It should be understood that this description is provided as an overview and is not intended to be limiting. That is, VPP is to include, in some cases, a single mode that may switch modes and achieve both atrial-based and biluminal-based functions. Therefore, for the sake of explanation, atrial mode or bicavity mode (see VPP) indicates a given function, and VPP using a single mode that includes the actual mode state / switching , or both aspects. Includes any of the functional states of. In addition, atrial pacing mode simply means that ventricular pacing is generally not provided (during a given cycle), and biluminal mode means that ventricular pacing is available (during a given cycle). Means. Therefore, as used herein, distinguishing between these modes does not exclude a three-chamber pacing configuration, a four-chamber pacing configuration, or any other multisite pacing configuration.</p><p> As shown above, various patients will constantly change between the need and no need for ventricular pacing. In that case, the change to two-chamber pacing mode is generally not expected to be permanent. That is, the device will periodically perform a conductivity test to determine if intrinsic conduction is present and therefore facilitates return to atrial pacing mode.</p>

FIG. 1 is a diagram of an implantable medical device system that has come to be used in accordance with the present invention. The medical device system shown in FIG. 1 includes an implantable medical device (IMD) 10, such as a pacemaker implanted in patient 12. It should be understood that the IMD10 can be a pacemaker, or that the IMD10 can also include cardioversion and / or defibrillation capabilities such as an implantable cardioverter-defibrillator (ICD). The IMD10 is hermetically sealed and housed in a biologically inert outer casing, which itself is conductive and can serve as an indifferent electrode in the pacing / sensing circuit. One or more pacemaker leads, collectively identified in FIG. 1 by reference number 14, are traditionally electrically connected to the IMD 10 and extend through the vein 18 into the patient's heart 16. .. Near the approximately distal end of the lead 14, one or more exposed conductive electrodes are placed to receive electrical heart signals and / or to deliver electrical pacing stimuli to the heart 16. It will be appreciated by those skilled in the art that the lead 14 can be implanted so that its distal end is located in the atrium and / or ventricle of the heart 16.

IMD10 is shown in FIG. 1 to be implanted in a "pocket" normally defined below the pectoralis major, with lead 14 extending through the vascular structure into the heart. Alternatively, the IMD10 can be embodied as a device that is implanted subcutaneously, the device having electrodes located away from the heart 16 or having leads extending into or outside the heart 16. It is either.

FIG. 1 also shows an external programming unit 20 for non-invasive communication with the embedded device 10 via the uplink and downlink communication channels, which will be described in more detail later. .. According to a conventional medical device programming system, a programming head 22 is associated with the programming unit 20 to facilitate two-way communication between the IMD 10 and the programmer 20. In many known implantable device systems, a programming head, as shown in Figure 1, is located on the implantation site of the device, in close proximity to the patient's body (typically within 2-3 inches of skin contact). ), RF signals to antennas in which one or more antennas in the head are placed in the airtight enclosure of the implantable device or in the connector block of the device, according to common practice in the art. And to be able to receive RF signals from the antenna. Alternatively, or in addition, communication with the programming unit 20 is carried out over an even longer distance through RF transmission by incorporating a suitable transmitter / receiver within the IMD10. FIG. 2 is a perspective view of an embodiment of the programming unit 20 according to the present invention currently disclosed.

FIG. 3 is a block diagram of an embodiment of the electronic circuit mechanism constituting the pulse generator in the IMD 10. The primary stimulus control circuit 25 controls the pacing and detection functions of the IMD. For example, the stimulus control circuit 25 in FIG. 2 includes a detection amplifier circuit 24, a stimulus pulse output circuit 26, a crystal clock 28, a random access memory and read-only memory (RAM / ROM) unit 30, and a central processing unit (CPU). ) 32 and. The IMD10 also has an internal communication circuit 34 to allow the IMD10 to communicate with the external programmer / control unit 20.

Continuing with reference to FIG. 3, the IMD 10 is connected to one or more leads 14 in the connector block assembly 11, which leads, when implanted, intravenously with the implantation site. It extends between the patient's heart 16. Electrically, the connection between the lead conductor and the internal electrical components of the pulse generator 10 can be easily accomplished by the lead interface circuit 19, which, like a multiplexer, Required between the various conductors in the lead 14, including the atrial tip electrode conductor ATIP and ring electrode conductor ARING, and the ventricle tip electrode conductor VTIP and ring electrode conductor VRING, and the individual electrical components of the IMD 10. It plays a role in establishing a flexible connection selectively and dynamically.

FIG. 4 is a Marker Channel® diagram showing a ladder diagram showing IMD operation in ADI / R mode. Those who are familiar with the latest technology with the help of the NBG Code will be able to understand the following: The letter (A) located first means that the pacemaker (or other implantable device) paces the atrium in the absence of an atrial detection event. The second letter (D) means that the pacemaker detects in two chambers, the atrial and ventricular heart chambers. The third letter (I) means that pacing is suppressed in any of the heart chambers when detected in that particular heart chamber. The final letter R means that the device is rate responsive, i.e. it can change the atrial rate in response to artificial sensors such as piezoelectric crystals, accelerometers, ventilation volumes, etc.

The operation in ADI / R mode is shown in the ladder diagram as shown below. Atrial pacing (or detection) event 1 initiates a non-programmable self-adjusting (eg, 100-150 ms) blanking time 4, followed by auto-adjusting atrial sensitivity (not shown). The detection circuit (see Figure 3) determines if ventricular detection event 2 has occurred. If detected, the timing circuit section (see Figure 3) starts VA interval 9. Other timings, blanking times, and refractory periods serve the following purposes: Programmable ventricular blanking time 8 prevents atrial pace 1 from being detected in the ventricular channel, sometimes referred to as crosstalk. Ventricular detection event 2 initiates 120 ms post-ventricular atrial blanking (PVAB) time 6, followed by self-adjusting atrial sensitivity. PVAB6 serves the purpose of preventing the detection of R or T waves in the atrial channel, called "far field R wave detection". Ventricular detection event 2 also initiates ventricular blanking 7 for 100 ms, followed by self-regulating ventricular sensitivity. This time serves the purpose of preventing the detection of the ventricular output pulse or the ventricular depolarization itself. R wave 2 is followed by repolarization, or T wave 3. The ventricular event 2 detected by the detection circuit (see FIG. 3) sends a signal to the timing circuit to start the VA interval 9, resulting in the start of the next atrial pacing cycle.

Considering that this mode is mainly used in sinus node patients with complete or somewhat intact AV conduction, this type of mode, as illustrated in the case of ADI / R mode. The movement is the movement that the clinician or doctor expects to occur. In the presence of full AV conduction, the pacemaker will retain ADI / R operation / mode, even if it is extended. Detected ventricular events will occur during most of the cardiac cycle (ie, PQRST). FIG. 5 teaches what would happen if a patient develops transient AV block over one or several cardiac cycles.

FIG. 5 is a ladder diagram of committed DDI / R behavior when a patient develops transient AV block. The purpose of the commit DDI / R operation is to retain atrioventricular support in the presence of the AV block. Briefly, the embedded device switches modes from the preferred ADI / R to the committed DDI / R for one cycle.

The timing of commit DDI / R is as follows. In DDI / R mode (the third pacing cycle with DDI / R), P is due to the fact that no ventricular events are detected between the second and third atrial pacing events. After the waves are paced, the AV interval 5 is set to a short 80ms. The purpose of this short AV interval 5 is to ensure that the ventricular pacing pulse ending in the paced R wave 13 does not compete with any potential endogenous R wave whose conduction is delayed from the previously paced atrial event. Is to do. Assuming the presence of such an endogenous R wave, the ventricular pacing pulse usually enters the absolute refractory period of the endogenous conducted R wave as a result of the timing of the ventricular output pulse, resulting in As a result, a pseudo-fusion beat (not shown) occurs. This action is intended to prevent the development of ventricular tachycardia when the ventricular pacing pulse enters the relative refractory period of the ventricles, commonly referred to as the "pacing on T" phenomenon.

Continuing at the timing of FIG. 5, the paced R-wave 13 initiates a ventricular blanking time of 120 ms, followed by self-regulating ventricular sensitivity (not shown). The paced R wave 13 also initiates 120 ms PVAB6, followed by self-regulating atrial sensitivity (not shown). Assuming that the transient AV block self-corrects and a paced R wave is detected, the preferred ADI / R resumes at the next pacing P wave or detection P wave, as shown in FIG. ..

FIG. 6 is a ladder diagram showing a pacing motion in one embodiment when a patient develops an AV block that lasts for two or more cycles. According to a preferred embodiment of the invention, once the beat is missed (ie, there is no Vs), the mode is not switched and there is a relatively reliable AV conduction, especially if there is a relatively reliable AV conduction. Note that this is the case. After switching the mode to DDI / R for only one cycle, the VA interval 9 times out, resulting in atrial pacing event 1. Very long intervals (eg, up to 400 ms or 65% of the AV interval indicated by the sensor) 17 are used to attempt to promote AV conduction. However, if the AV interval 17 is not interrupted by the detected endogenous R wave, as shown in the first period (with ADI / R), the pacemaker immediately switches to DDD / R mode. If an endogenous R wave is detected, the device returns to ADI / R operation (not shown). DDD / R operation with programmed AV intervals is sustained until the detected endogenous R wave is detected. Attempts to force ADI / R operation to recover are periodically made (shown in Figure 7). If atrial tachycardia is detected, the mode will be switched to DDI / R mode (see Figure 8).

FIG. 7 is a ladder diagram showing a periodic attempt to restore ADI / R operation during sustained DDD / R operation. As mentioned above, the DDD / R mode may be a sustained motion mode if the patient develops a persistent AV block, such as that that may occur with a heart rate dependent AV block. In such cases, the device may be programmed to return to ADI / R1 after a programmable number of DDD / R cycles. The device then searches for ventricular detection events, for example, at 23 after atrial pace 1. If the detected endogenous R wave is detected, the ADI / R operation is resumed immediately. In the absence of ventricular detection events, the device continues to operate in DDD / R mode, as shown in the third cycle of FIG.

FIG. 8 is a ladder diagram of pacing movement when a patient develops atrial tachycardia. Sinus node patients often have episodes of atrial tachycardia, atrial flutter, or atrial fibrillation. During these episodes, pacing movements must be performed so that the ventricular pacing rate is not synchronized with either the fast atrial rate or the slow enough to cause symptoms.

In Figure 5, it was mentioned that the device can switch to DDI / R mode while operating in ADI / R mode. The presence of atrial tachycardia, according to DDI / R mode, not only prevents the ventricles from synchronizing with the faster atrial rate, but also prevents the ventricular pacing rate from falling below the programmed lower rate. Very suitable for pacing at times. Therefore, as shown in FIG. 8, when atrial tachycardia occurs, even a fast atrial detection event 27, in which the ventricular event is not conducted, does not affect ventricular timing 9. Since there are no ventricular events, the action immediately switches to DDI / R mode. In the presence of atrial tachycardia, the VV interval 9 times out, resulting in a paced R wave 8 at a rate faster than the programmed lower rate or at the rate indicated by the sensor in DDI / R mode. The movement shown in FIG. 8 continues as long as atrial tachycardia persists. At the end of atrial tachycardia, the preferred ADI / R resumes, as shown in FIG. 4 or 7, depending on how the heart recovered from the atrial tachyarrhythmia. In the event of abrupt termination of atrial tachyarrhythmia, rapid recovery of ADI / R mode occurs (see Figure 4). However, if the atrial tachyarrhythmia slowly "calms", there may be a period of DDD / R pacing, and attempts are made to periodically recover to ADI / R pacing, as shown in Figure 7. Be done.

With reference to FIG. 9 comprehensively, the ventricular pacing protocol comprises one or more of the following embodiments: A mode supervisor is built in to control a wide range of behavior related to mode changes. Modules based on hardware, software or firmware can be used as mode supervisors. One aspect of the mode supervisor is to monitor the patient's atrial-ventricular condition and intervene by invoking a continuous mode switch to conventional pacing modes (ie, DDD / R and DDI / R) when needed. It is to be. The mode supervisor, in one embodiment, distinguishes between an acceptable (or "relatively reliable") AV conduction state and an unacceptable (or "relatively unreliable") AV conduction state. Define unreliable AV conduction according to the Wenkebach pattern, which defines the AV conduction tolerance that is important for. For example, a 4: 3 AV conduction tolerance allows favorable ADI / R movements to be sustained as long as there are at least 3 ventricular events for each of the 4 physiological atrial events. If the ratio of A-event to V-event is less than the predefined tolerance ratio, a continuous switch to conventional DDD / R pacing will occur. Atrial events classified as non-physiological (ie, within ARP) are not considered in the calculation of the A: V ratio. This avoids inappropriate mode switching to DDD / R in the presence of frequent non-conducting premature atrial contractions (PACs).

When calling DDD / R pacing in the presence of unreliable AV conduction, the mode supervisor immediately plays a role in attempting to restore ADI / R pacing. Mode supervisors are only of the newly initiated DDD / R pacing, as it is known that AV conduction disease usually progresses slowly and short signs of severe block are expected in the early stages of disease progression. After a short episode, it will try to restore ADI / R activity. Therefore, after a short time (eg, 1 minute) has passed since the DDD / R pacing, there is an initial retry to reveal complete AV conduction and restore the ADI / R pacing. If ADI / R recovery fails, retry at 2 minutes, 4 minutes, 8 minutes, 16 minutes and 32 minutes, then at 1 hour, 2 hours, 4 hours, 8 hours, 12 hours and 16 hours. Is done. Of course, other timing sequences can be used cyclically and aperiodically (and at the beginning of atrial pacing initiated locally and remotely by the clinician or patient).

As shown above, IMD10 will periodically attempt to return to atrial pacing mode. Similarly, as will be explained later, frequent mode switching may result in a persistent switch to bicavity mode, after which attempts are made to return to atrial mode at given intervals. The process of deliberately attempting to return from biluminal mode to atrial mode in this way is collectively referred to herein as "conduction check" or "conduction checking". As mentioned in the above embodiments, the delay between each conductivity test is increasing. In the examples provided, every 2 minutes, every 4 minutes, every 8 minutes, every 16 minutes and every 32 minutes, then every 1 hour, every 2 hours, every 4 hours, every 8 hours, every 12 hours and 16 Attempted at time intervals. The individual values selected and the number of trials made at a given interval before transitioning to longer intervals can be changed. For example, patterns such as 1, 1, 2, 2, 4, 4, 8, 8, 8 can be used.

In one embodiment of the invention, the interval or progression of conduction test timing is selected so that the patient is unpredictable and / or avoids circadian repetition. In general, the occasional absence of ventricular depolarization will go unnoticed by the patient. However, frequent loss of pulsation can be perceptible. In such cases, if the conductivity test is performed every minute or every 3 minutes (eg, at relatively short intervals) and the patient perceives that the pulsation has jumped, then the physiology to the patient. Conductivity tests may fail as a result of either physical or psychological effects. For example, the patient may be expected to be tense or stressed, resulting in a high heart rate, which, when conditions are met, can prevent the development of the underlying intrinsic conduction. is there. Therefore, the pattern is staggered and set at progressively longer intervals to prevent the patient from anticipating a conductivity test. As just an example, the patient probably perceives and strains the conductivity test in 2 minutes. After 4 minutes, the patient may still be tense. After 8 or 16 minutes, the patient is likely to have lost focus on the problem, relieving tension and facilitating a more effective conductivity test.

Assuming that the conductivity test fails when attempted in stages, a maximum is reached. In the above example, this value is 16 hours. That is, the conductivity test is performed once every 16 hours. This value avoids circadian repetition. This simply means that the conductivity test is not done at the same time every day. Consider a hypothetical patient who develops a transient block that lasts long enough to reach the maximum conductivity test interval. After that, endogenous conduction resumes (or pacing will not occur), but blocking occurs during sleep time. If the maximum interval was 24 hours, the conductivity test could be continuously attempted while the patient was asleep and would therefore fail. Such a situation would abandon the benefit of reduced ventricular pacing during the time of waking. For example, by utilizing the 16-hour maximum, conductivity tests are performed at different times of the day, avoiding the above scenario. Of course, to achieve this in the same way, you can choose intervals other than 16 hours. However, if the selected interval is relatively close to 24 hours (eg, 23 hours), the conductivity test will continue for many days and during the same circadian interval (eg, at night or during sleep). May be done.

Therefore, there are several factors in determining when to proceed with the conductivity test. First, the test is performed frequently and with a short duration. Assuming those tests fail, the interval will be long until the maximum is reached. This maximum should be long enough not to waste resources and short enough to benefit the patient relatively quickly when intrinsic conduction returns. , Should be staggered to avoid circadian repeats, and optionally should be selected to avoid prolongation of repeats in the circadian cycle (eg, 23 hours) by providing staggers. Is.

FIG. 10 is a flow chart showing the process for performing the conductivity test. When operating in atrial pacing mode according to the ventricular pacing protocol as described above, the patient has lost intrinsic conduction (200). After some time, when any given protocol can take several cycles to fulfill it, the device generally operates in bicavity pacing mode (eg, DDD / R) (210). IMD10 initiates a conductivity test interval (CCI) (220). This is a timer, a pacing cycle count, or a similar mechanism used to indicate when a device should attempt a conductivity test. At the expiration of the CCI (230), the IMD10 performs a conductivity test (240) to determine if there is intrinsic conduction (250). In the presence of endogenous conduction, IMD10 operates in atrial pacing mode (260).

If no endogenous conduction is found (250), increase CCI by a given amount (270). If the CCI is evaluated (280) and below the maximum, the process returns to the start of the CCI (220). This will either be at the maximum value of CCI or at an increased value of CCI (270). In this way, the CCI is gradually increased until the maximum value is reached. That is, if the CCI is greater than the maximum (280), the CCI is changed to the maximum and the process returns to (220). The programmed pattern determines any given amount of increase. As shown above, in one embodiment, this is 1 minute, 2 minutes, 4 minutes, 8 minutes, 16 minutes and 32 minutes, followed by 1 hour, 2 hours, 4 hours, 8 hours and 16 hours. Can be 16 hours maximum. It should be understood that proceeding in this way is merely an example, and more or less iterations may be utilized and values may be selected accordingly. In addition, step (280) can be modified to incorporate a counter so that trials may be made multiple times at a given value before increasing its value.

FIG. 11 is a schematic timing diagram showing a conductivity test performed periodically. Bars 300 and 320 both indicate time, specifically 12 hour intervals. Arrow 310 indicates the pattern of conductivity tests performed at maximum values. In pattern "a", conductivity tests are performed every 16 hours. With reference to the time bar 320 and the time zone indicator 330, it is easy to see that the first conductivity test is done at 16:00 and it is in the afternoon. The next conductivity test will be done at 8 o'clock, which is in the morning, and the next conductivity test will be done at 24:00 (midnight), representing a nighttime assessment. If the 16-hour interval is maintained, this pattern will be repeated and the circadian distinction will be achieved. It should be understood that the loss of conduction is the starting event and the actual time zone used in the end is obtained from the triggering event.

Although not shown individually, this variant may be slightly modified to further achieve circadian variability. As shown above, at 16-hour intervals, the afternoon, morning, and night progressions will be repeated, and conductivity tests will be performed at approximately the same time (eg, 16:00, 8:00, 24:00). .. This set of conductivity tests can be classified as a complete circadian subset. That is, at least one test is performed during each of the three main hours of daily life. After one circadian subset (or a certain number of subsets), the offset value can be introduced. The value chosen for the offset is not important. 1 hour, 2 hours or 3 hours is common, but any value (positive or negative) can be tolerated. Thus, after the circadian subset (the last subset of a given number of circadian subsets) is finished, an offset value is added to the CCI value to repeat again. Therefore, in this example, the maximum CCI time is 16 hours, after one circadian subset, an offset value of 1 hour is added, and the next conductivity test is done after 17 hours instead of 16 hours. To do so. However, the offset value is not retained and subsequent conductivity tests occur after 16 hours. Therefore, an exemplary pattern would be 16-16-16-17-16-16 etc. In other words, the conductivity test can be performed at 16:00, 8:00, 24:00, 17:00, 9:00, and so on. In this way, the circadian distinction is always maintained between each subsequent conductivity test, and further variation is given in each day's time over a predetermined period of time.

A feedback mechanism can be used, and successful conductivity tests are noted, and offset values can be used to ensure that conductivity tests are performed during times known to have been successful in the past. In other words, IMD10 can learn patient-specific parameters that increase the likelihood of successful conductivity testing and can adjust its progression accordingly.

Returning to FIG. 11, pattern "b" shows the conductivity tests performed at 32 hour intervals. It retains circadian variability, but with longer intervals, longer times elapse between subsequent conductivity tests, and even longer times between repetitive tests at any given time period. .. The pattern "c" uses a 16-hour interval as a predetermined time, but if unsuccessful, the maximum value is increased up to 32 hours. The number is not limited, but conceptually, if the conductivity test continues to fail over a long period of time, the chances of success are reduced and it can be justified to reduce the frequency of the conductivity test. it can. Pattern "d" indicates a conductivity test performed at 20 hour intervals. Therefore, it is clear that various patterns may be used to achieve the desired temporal relationship.

In one embodiment, the algorithm used to search for full AV conduction and restore ADI / R is defined according to one of two options. The first option is simply to refrain from ventricular pace stimulation during DDD / R operation. If ventricular detection follows a physiological atrial event with refrained ventricular pacing, ADI / R pacing is resumed. Otherwise, DDD / R pacing will continue and then be retried as scheduled or by manually invoking (detailed above). The search for the second option of full AV conduction involves extending the AV delay during DDD / R pacing to a pre-specified AV conduction (search) interval (AVCI). For example, if the AVCI is 400 ms, the AV delay is extended to 400 ms after a physiological atrial event (detection or pacing). If the AV interval is interrupted by ventricular detection, thereby avoiding the ventricular pace in the DDD / R operation, the mode supervisor reverts to the ADI / R operation. Otherwise, at the expiration of the AVCI interval, the ventricular pace is delivered, the DDD / R operation resumes, and retries as scheduled (or manually activated) as described above.

The mode supervisor monitors repeatedly failed AV conduction tests for the maximum test duration in one embodiment. So, for example, if the AV conduction test fails seven times in a row, for example, at 16-hour intervals, the mode supervisor can suspend the AV conduction test, in which the device will indefinitely DDD / R. You can stay in mode. Alternatively, the invention can continue to perform conductivity tests at maximum intervals. This simplifies programming options. That is, even if complete heart block occurs, the protocol works well for the patient, and even if it is unlikely, it can confirm the return of endogenous conduction.

As shown above, AVCI may be extended from a nominal value (eg 150ms) to a given value, eg 400ms mentioned above. Nominal values are intended to indicate conventionally programmed parameters used for standard operation in modes such as DDD mode or DDDR mode. Nominal values are usually in the range of about 150ms to 180ms. The extended AV interval provides a longer window, in which intrinsic conduction may return, allowing it to return to atrial pacing mode. When the device remains in bicavity pacing mode, ventricular pacing is provided at the end of that interval, if necessary.

FIG. 12 is a flow chart showing the entire process. To illustrate, the device is assumed to be in atrial mode (500). As described above, the device monitors endogenous conduction. If present (510), the device remains in atrial mode (500). If intrinsic conduction fails (510), the device determines if a change to bicavity pacing mode is required (520). If not required, the device will again remain in atrial pacing mode (500).

Where appropriate, the device will operate in bicavity pacing mode at the appropriately desired AV interval (530b) (530a). Periodic conductivity tests are performed (540) and as a result (550) to determine whether the device operates in bicavity pacing mode or in atrial pacing mode.

FIG. 13 shows various options for determining the AV interval while operating in the two-chamber pacing mode. There are three comprehensive categories covered. The first category is during the initial period or the first few cycles operating in the two-chamber pacing mode (560). The second category (600) is during the time of periodic or gradual conductivity tests performed below the maximum CCI. The third category is the operation in the two-chamber pacing mode when the conductivity test is alternativeally completed while the CCI is at its maximum (680).

In the first category (560), the movement may include one or several cycles immediately after the lack of ventricular depolarization. Thus, in one embodiment, in this first cycle in bicavity mode, the AV interval may be shorter than the nominal value (570). For example, the shortened AV interval may be set to 80ms. Alternatively, the AV interval may be set to the reprogrammed nominal value (580). In other embodiments, this first cycle may include an extended (eg, longer than nominal) AV interval, such as AVCI. The selected VPP will determine the suitable bicavity pacing protocol for the first cycle and / or the first few cycles in this mode, and separating this category is about setting the AV interval. The following options are merely intended to illustrate that they may optionally be applied in this category (560).

The second category (600) refers to the operation in bicavity pacing mode while the conductivity test is being performed. As explained above, the intervals between such conductivity tests, eg, CCI, can vary and are generally longer until the maximum interval is reached if consecutive trials are unsuccessful. In this category, the AV interval may be set to the nominal value (610). Of course, it is possible that an endogenous event may occur during the nominal AV interval. However, according to this option, VPP determines whether endogenous conduction is restored, primarily based on the conductivity test itself.

In another embodiment, the AV interval is set to a maximum safety extension value, or at least one fixed value (eg, AVCI) that is longer than the nominal AV interval (620). Therefore, with each cardiac cycle, there is an increased, if not maximum, opportunity for endogenous conduction to return, while still providing ventricular pacing capability in biluminal pacing mode.

In another embodiment, the AV interval is adjusted as the conductivity test progresses (630). In general, this means that the AV interval is initially long (no changes occur during the first category (560)) and is shortened as the conductivity test progresses and fails in succession. Means. Changes or adjustments in AV intervals may be associated with changes in CCI.

In one embodiment, the AV interval will gradually decrease at a predetermined rate over the conductivity test process in the second category (600) (640). Alternatively, the AV interval may decrease as a step function each time the CCI changes (650). Gradually shortening, or step functions may be based on predetermined time intervals or percentage-based changes. Similarly, AV intervals may be adjusted to be inversely proportional to CCI (660).

In general, the above changes apply directly to conductivity tests that have not been successful in succession. If the conductivity test is successful intermittently, VPP resumes this process with each successful cardiac cycle or series of cardiac cycles. This is perfectly acceptable. However, when these intermittent events occur, the AV interval may be set to a value close to or equal to the nominal value, if desired, and the rate of shortening can be increased step by step. The change can be large and the proportion of proportionality (inverse proportionality) can be increased to lead to the nominal AV interval more quickly.

In one embodiment, the percentage of time spent in atrial pacing mode is compared to the percentage of time spent in biluminal pacing mode. If the percentage of time spent in two-chamber pacing mode exceeds a predetermined threshold, perform one of the above actions to reduce the AV interval more quickly or set it to a nominal value. To do. Alternatively, the mechanism by which the device changes the AV interval may include the number of mode changes over a given number of cardiac cycles, or the number of mode changes within a predetermined time frame.

In one embodiment, the AV interval is gradually reduced as unsuccessful conductivity tests occur. At some point, CCI can reach its maximum (680). As explained above, at this maximum CCI (with or without change) the conductivity test may be completed or may be performed. In any case, the AV interval is set to the nominal value (690). In addition to the conductivity test that may be performed at max CCI, the AV interval may be extended over several cycles prior to this conductivity test to facilitate the return of endogenous conduction. The periodic extension of the AV interval can also serve as an alternative conductivity test function that can be performed as predetermined.

The device is actually in two-chamber operation, and the nominal AV interval is set according to the traditional generally accepted pacing programming parameters, so when the CCI is at maximum, the AV interval is set to the nominal value. Will be done. Alternatively, the AV interval may be adjusted continuously or intermittently, even when the CCI is at its maximum (700). It also serves as a variant of the conductivity test that may be performed on a regular basis while preserving ventricular pacing without placing the patient continuously under the maximum AV interval. Will.

The present invention can be implemented using executable software code and / or operating parameters saved (or downloaded to the medical device) by the medical device. Such devices may be placed in the body and programmed later according to the present invention or before implantation (eg, may be reprogrammed using telemetry techniques or the like). Or use firmware that is subject to change). However, the present invention is not limited to firmware or hardware embodiments. In practice, the invention can be practiced in hybrid forms or in combination as desired, using device programming techniques known and used in the art.

It should be understood that the above description is intended to be exemplary and not intended to be limiting. Reading and understanding the above description will reveal to those skilled in the art a number of other embodiments. Therefore, the scope of the invention should be determined by reference to the appended claims, along with the full scope of the equivalents to which the appended claims are entitled.

<figref num="1">FIG. 5 is a human body implantable device system according to the invention, including an airtight sealing device implanted in a patient and an external programming unit.</figref><figref num="2">It is a perspective view of the external programming unit of FIG.</figref><figref num="3">It is a block diagram of the embedded device of FIG.</figref><figref num="4">It is a ladder diagram of ADI / R operation.</figref><figref num="5">It is a ladder diagram of the commit DDD / R operation when a patient develops a transient AV block.</figref><figref num="6">It is a ladder diagram which shows the pacing movement when a patient develops an AV block that lasts for 2 cycles or more.</figref><figref num="7">It is a ladder diagram which shows that it tries periodically to recover ADI / R operation during a continuous DDD / R operation.</figref><figref num="8">It is a ladder diagram of the pacing movement when a patient develops atrial tachycardia.</figref><figref num="9">It is a flow chart which shows one Embodiment of the mode supervisor by this invention.</figref><figref num="10">It is a flow chart which shows the process for performing a conductivity test.</figref><figref num="11">It is a schematic timing diagram which shows the conductivity inspection performed periodically.</figref><figref num="12">It is a flow chart which shows the process for adjusting the AV interval by the ventricular pacing protocol.</figref><figref num="13">It is the schematic which shows the AV interval adjustment option.</figref>