Vitatron Medical B. V.

Gustaaf A Stoop

Johannes S Van Der Veen

Malcolm J Begemann

Frits M Van Krieken

Geeske Van Oort

Bernhard De Vries

Werner Peter Wohlgemuth

Hendrikus A Westendorp

Marijn Van Gemert

Marcus O Filipovich

Bernhard deVries

Paul V Van Zanten

There is provided a cardiac pacemaker system with a ventricular tachycardia prevention feature, whereby the pacemaker monitors ventricular activity during each patient awakening period to determine when VT is likely. In a preferred embodiment, QRS and T wave templates are generated cyclically during awakening, and compared to normal templates to obtain a measure of variability, indicative of refractory dispersion and thus of probable VT. Ventricular extra-systoles are also monitored and analyzed during the awakening period to see how closely they occur to the ventricular vulnerable period. When the monitored data indicates VT probability during awakening, the pacemaker responds by overdriving the heart with an intervention pacing rate which is continually adjusted as a function of the currently obtained data.

Pacemaker system with diurnal pattern controlled overdrive for

There is provided a pacemaker system having the feature of delivering a ventricular safety pulse (VSP) following an early ventricular sense (VS), wherein the pacemaker automatically determines whether VSPs are to be delivered following early VSs, and if yes, with what timing. The pacemaker gathers data following delivered VSPs, which data contains information indicative of whether each early VS was indeed the result of a spontaneous R wave, or was due to crosstalk from a prior delivered atrial pace pulse. This data is processed and, when it presents a high statistical confidence, is used to make a determination of whether to respond with the assumption of a true R wave, or of crosstalk. If the data is not statistically significant, the pacemaker delivers VSPs in a normal fashion, e.g., at the end of a programmable VSP interval timed out following delivery of an atrial pace pulse.

Pacemaker with automatically controlled ventricular safety pulse

There is provided an implantable cardiac pacing system, having multiple sensing channels for sensing spontaneous cardiac signals which arise between respective different pairs of electrodes. In a preferred embodiment, the system utilizes a single pass VDD-type lead, having at least one atrial ring electrode for sensing atrial signals, and at least a distal tip electrode positioned in the right ventricle for sensing ventricular signals. Sensing channels concurrently process signals between the atrial ring and the pacemaker can (the indifferent electrode); the ventricular tip electrode and the pacemaker can; and the between the atrial ring and the ventricular tip. One or more additional electrode pairs can also be employed. Enable signals selectively enable the channels to be used for concurrent processing of the signals. The signal processing embodies both pattern recognition and timing, for analysis and interpretation of the type of event which gives rise to the different concurrent signals on the respective different channels.

Dual chamber pacemaker with single pass lead and with bipolar and

There is provided a pacing system, preferably a VDD system having a single pass lead with one or two ventricular electrodes and a pair of atrial electrodes. The pacemaker has timing and logic capability for determining when an atrial back-up pulse, such an atrial synchronization pulse, can be delivered, and also whether the pacemaker can provide for continuing atrial pacing. The pacemaker is provided with a plurality of modules for determining the likelihood that a delivered atrial pace pulse resulted in atrial contraction, and for storing data relating to the probable capture or no.sub.-- capture result of each delivered pace pulse. One of the capture-determining modules is a timing module which stores a plurality of rules by which a sequence of events and rates surrounding a delivered atrial pace pulse is analyzed to determine the probability of capture. The pacemaker carries out capture probability determinations following each delivered pace pulse, and on the basis of such continuous determinations evaluates atrial pace pulse capture efficiency, and adjusts the atrial pace pulse output level to optimize atrial pacing.

Single pass lead dual chamber pacing system with means for evaluating

There is provided an implanted pacemaker having a system and method for determining a measure of the circadian rhythm of a patient and adjusting the pacemaker nighttime setting of lower rate limit to correspond to the determined circadian rhythm. In a preferred embodiment, the circadian rhythm is determined by examining daily variations in QT interval. In a first QT embodiment of the invention, when QT interval becomes longer than a parameter QT.sub.-- sleep, which represents a value associated with patient nighttime, the LRL is dropped to a night value and maintained at such value for a predetermined duration. In another embodiment, the start of night LRL is determined as a function of when QT interval becomes longer than a sleep value for a predetermined elapsed time, and LRL is changed back to a day value when QT interval drops back down to a shorter value than the sleep value and stays there for an elapsed period of time. In yet another algorithm in accordance with this invention, the sleep value of QT interval is adapted so that the night period when QT interval is longer than the sleep value more closely corresponds to desired time of sleep, and the start of night LRL and the start of Day LRL are shifted to correspond to the detected night period. Additionally, other pacing parameters such as the escape interval hysteresis value may be varied based on determinations of the circadian rhythm.

Pacemaker with automatic lower rate limit drop

A dual chamber pacemaker and method for ventricular rate smoothing during high rate episodes such as atrial fibrillation are provided. The pacemaker determines when there is a pathologically high atrial rate episode, such as by determining when atrial senses correspond to a spontaneous atrial rate above a predetermined upper rate limit. When such an episode is determined, the pacemaker determines a ventricular pacing escape interval, corresponding to a flywheel rate, the flywheel rate being set at the beginning of the episode to substantially equal the atrial rate just before the high rate episode. As long as the episode continues, the flywheel rate is incremented upward whenever a ventricular sense occurs, thereby following the average ventricular rate; whenever the flywheel escape interval times out and a ventricular pace is delivered, the flywheel rate is decremented. By allowing ventricular senses and pacing only after timeout of an escape interval which substantially equals average ventricular rate, the episode is treated by smoothing out ventricular rate variations while substantially maintaining the ventricular rate that would otherwise occur.

Pacemaker system and method with ventricular rate smoothing during high

There is provided a rate responsive pacemaker system and method employing an activity-type sensor for deriving signals for determining pacing rate, wherein the activity sensor threshold is automatically adjusted as a function of monitored sensor output. In a preferred embodiment, activity counts are categorized on a histogram basis, and the histogram data is stored over a selected period of time. The activity data in histogram form is then analyzed and compared to predetermined criteria to determine whether threshold seems to be proper, or whether threshold adjustment is indicated. The adjustment algorithm provides different degrees of adjustment depending upon the circumstances. Specifically, where the data suggests too many or too few counts within an expected range, the threshold is adjusted as a function of whether the analyzed outputs are only a little bit out of the expected range or quite a bit out of the expected range. The algorithm also determines whether the sensor response accurately reflects patient rest. Another specific feature of the invention is determination of when the sensor is picking up false positives and thus improperly responding to extraneous signals such as patient's cardiac contractions.

System and method for adjusting sensor threshold in a rate responsive

A dual chamber pacemaker system and method are provided for placing the pacemaker in an asynchronous mode when retrograde conduction is present, having the capability of detecting the onset of retrograde conduction and also monitoring on a cycle-by-cycle basis to determine the end of retrograde conduction. The detection of end of retrograde conduction is accomplished by two operative algorithms, i.e., a first algorithm which is executed at the time of any atrial sense and a second algorithm which is executed at the time of each ventricular event. Following an atrial sense, the pacemaker checks to see whether the just concluded VA interval conforms to predetermined RC interval criteria, and if not, immediately switches the pacemaker out of the RC mode and into a synchronous tracking mode. Following each ventricular event while the pacemaker is in the RC mode, the pacemaker monitors a predetermined class of special events and determines end of RC upon detection of a pattern of such special events. In a specific embodiment, if there are n (e.g.,3) consecutive cycles wherein the VA interval differs from the VA interval of the previous cycle by more than a predetermined amount, this is determined to establish a pattern indicative of end of RC; upon detection of this pattern, the pacemaker immediately switches to a synchronous tracking mode of pacing.

Pacemaker system and method with improved detection of end of retrograde

A dual chamber pacemaker is provided with a dynamic PVARP which tracks the occurrence of high rate atrial senses within the normal PVARP range. The dynamic PVARP is a short window of about 50 ms which is moved toward the time of occurrence of any sense signal within the window range of about 50-200 ms following the ventricular event. Senses which occur within the dynamic window are rejected, or blanked, while senses occurring within the window range but outside of the window are recognized and evaluated. The dynamic window technique accordingly enables the pacemaker to recognize tachycardia senses which would otherwise be blanked by a fixed length PVARP, while providing efficient suppression of FFRS events. The pacemaker also provides a technique for determining whether rejected senses are tachy atrial senses or FFRS, by modulating the AV interval and thus shifting the dynamic window which is coupled to the ventricular pulse. As a result of this modulation, FFRS events move with the dynamic window, but tachy senses are covered, or revealed, enabling the pacemaker to make an appropriate response.

Pacemaker with improved far field R wave sensing and suppression

A dual chamber pacemaker is provided with the capability of determining when there is retrograde conduction, and responding by switching into an asynchronous mode of ventricular pacing. The pacemaker's response to RC further includes delivering at least a first asynchronous ventricular pace pulse at a ventricular escape interval calculated to occur at an appropriate AV delay following the next expected spontaneous natural beat. Thus, the ventricular escape interval can be calculated as V.sub.esc =VA+AA.sub.avg +AV.sub.min, where VA is the retrograde time from the prior ventricular pulse to the retrograde atrial sense (or PAC), AA.sub.avg is a measure of the average natural atrial rate before retrograde conduction, and AV.sub.min is a predetermined value of AV delay. This optimum value of V.sub.esc is designed to regain synchronous tracking of the natural sinus after the first extended ventricular pulse. Alternatively, the response can aim to regain tracking in N cycles, where V.sub.esc =AA.sub.avg +.DELTA., where .DELTA.=(AV.sub.min +VA)/N.

Dual chamber pacemaker system with improved response to retrograde

A VDD-type pacing system which may have a floating atrial electrode analyzes P-wave events and absences of P-waves to determine data indicative of the likelihood of P-wave undersensing. The pacemaker logic chooses a reaction algorithm to respond to atrial events in accordance with whether an absence of a P-wave is more likely to have been an undersense or an incidence of bradycardia. Specific algorithms are presented which illustrate pacemaker reactions to probable undersense and brady occurrences. The pacemaker also incorporates a subsystem for detection of undersense events.

VDD (R) pacing system

There is disclosed a pacemaker, a dual chamber VDD(R) or DDD(R) pacemaker, having improved features for avoiding undesired sensor-sinus competition and providing blended sensor and sinus (atrial) control. The pacemaker employs atrial hysteresis which is used during sensing of natural atrial beats in order to enable tracking the sinus signals that occur at rates below the current pacing limit; and sensor hysteresis which prevents early takeover by sensor control and, in a DDDR pacer, controls when the sensor rate controls over a sensed sinus rate and also enables dropping the pacing rate during sensor control so as to enable finding and tracking of underlying lower rate sinus signals. The sensor hysteresis function is automatically adapted by obtaining and processing scattergram data representative of the sensor rate compared to the average of the natural sinus rate, and adjusting the sensor hysteresis function to optimally match the data. The atrial hysteresis function is also automatically adjusted as a function of rate by obtaining and processing scattergram data representative of sinus jitter, i.e., the difference between the current rate of the last atrial interval and the average sinus rate. In addition, blending of sensor and sinus control is achieved by automatic adjustment of the rate response curve based on accumulated data representative of RR signals as a function of running atrial rate.

Rate adaptive dual chamber pacing system and method with automatic

A rate adaptive pacemaker and method of operation, where the sensor-indicated rate is adjusted as a function of sensed sinus rate. The pacemaker is particularly adapted for VDDR operation. The natural sinus rate is compared to the sensor-indicated rate at one or more rates, and the sensor response function is adjusted, or adapted as a function of such comparisons, so as to optimize sensing of the atrial rate and maintenance of synchronous operation. The rate response function may be adjusted specifically at upper pacing limit, and may also be adjusted as a function of comparisons made at other rates.

Rate adaptive pacemaker with adjustment of sensor rate as a function of

A dual chamber pacemaker system is provided having an improved Wenckebach response for optimizing tracking of atrial signals having rates within a rate range above the normal tracking range, i.e., in a designated Wenckebach range. When an atrial sense occurs in the Wenckebach range, the AV delay is extended up to a predetermined maximum extension to enable delivery of a ventricular pulse at the ventricular upper rate limit (dynamic tracking limit). When the AV delay would have to be extended beyond the maximum extension in order to pace the ventricle at the dynamic tracking limit, the next ventricular stimulus is delivered asynchronously at an escape interval greater than the escape interval corresponding to the dynamic tracking limit, e.g., at a predetermined lower pacing limit.

Pacemaker with Wenckebach operation

A dual chamber pacemaker is provided having incorporated therein a VA conduction test for concurrently testing for the conditions of retrograde conduction (RC) and far field R wave sensing (FFRS). The pacemaker changes the AV or VV interval to a predetermined interval over a number of pacemaker cycles, and determines whether the VA interval remains substantially unchanged, i.e., the VA intervals are substantially equal. When VA interval equality is determined, the pacemaker checks the measure of VA interval with stored RC and FFRS criteria to determine whether either can be verified. Respective corrective steps are taken if either RC or FFRS is verified.

Growing community of inventors

Dieren, Netherlands

Gustaaf A Stoop