Repetitive Nonreentrant Ventriculoatrial Synchrony Research Articles

Endless loop tachycardia among patients with devices having advanced preventive algorithms: A case series and brief review.

Endless loop tachycardia (ELT) is the commonest pacemaker mediated tachycardia (PMT) encountered among patients with cardiac implantable electronic devices (CIEDs). Despite being enabled with various preventive algorithms, we encountered several cases having recurrent, long, and symptomatic ELT. We retrospectively analyzed consecutive device checkups at device clinic at a single center of eastern India between January 2019 to March 2023. There were 20 cases of confirmed and sustained ELT among 4520 device checks. Although mostly benign, in two cases ELT led to clinical worsening in patients having left ventricular (LV) systolic dysfunction. Even with good ventricular function, ELT resulted in improper atrioventricular (AV) synchrony leading to disabling symptom in one case. The differentiation of ELT from sinus tachycardia and atrial tachycardia (AT) was not always easy. Magnet application is certainly useful to differentiate. The situations that provoked ELT in this study were-long AV delays, VIP (ventricular intrinsic preferences)/MVP (managed ventricular pacing), atrial non-capture, atrial under/over sensing, premature ventricular contractions (PVCs)/couplets, premature atrial contractions (PAC) and slower ventriculo-atrial (VA) conduction. Rate responsive shortening of post-ventricular atrial refractory period (PVARP) also promoted its occurrence and hindered troubleshooting. When ELT occurred despite post-PVC extension of PVARP, lowering the atrial sensitivity, switching to bipolar sensing and manual setting of longer PVARP after measuring VA conduction time were useful. "Rate responsive PVARP" had to be turned off in a few cases to prevent ELT. On the contrary, an over aggressive prolongation of PVARP led to repetitive non-reentrant ventriculo-atrial synchrony (RNRVAS) in two cases. Checking VA conduction during implantation and noninvasive program stimulation (NIPS) during follow up were useful to check the tendency for ELT. Clinically significant ELT is rare but not uncommon among devices having in-built preventive algorithms. Manual adjustments are often useful to troubleshoot the same.

PO-04-057 ATRIAL FIBRILLATION CURED BY PACEMAKER REPROGRAMMING

Atrial fibrillation (AF) is commonly detected by remote monitoring of implanted devices. A common question is whether to start anticoagulation in patients with detected AF at risk of stroke. However, the cause of AF is rarely able to be diagnosed or corrected. Repetitive non-reentrant ventriculoatrial synchrony (RNRVAS) is a pacemaker mediated arrhythmia that can occur in patients with intact ventriculoatrial (VA) conduction. Ventricular pacing with retrograde atrial activation that falls within the PVARP is followed by atrial pacing, often delivered while the atrium is refractory. Retrograde atrial activation from the next ventricular paced beat facilitates a repetitive (but non-reentrant) process. Atrial arrhythmias may occasionally result. To highlight the importance of recognizing and correcting RNRVAS as a cause of device-mediated arrhythmia. NA A 68-year-old man with hypertension and sinus node dysfunction underwent dual chamber pacemaker implant (Abbott Assurity). Device interrogation 5-years later showed repetitive episodes of AF that might warrant anticoagulation. Device tracings revealed RNRVAS: retrograde atrial activation falling in PVARP, followed by competitive sensor driven atrial pacing with non-capture, until a captured atrial event initiated AF (Figure, red arrow). Anticoagulation was deferred in favor of device reprogramming, including: 1) reduction in the lower rate; 2) reduction in paced AV delay; and 3) disabling of rate-response. The patient had no further AF episodes. RNRVAS is largely benign but may facilitate initiation of AF or other supraventricular arrhythmias that lead to symptoms or inappropriate therapy. Both RNRVAS and device-triggered AF may be underrecognized. Current devices do not have automatic diagnostic or treatment algorithms. Therefore, it is important to be aware of RNRVAS triggered AF in patients with a dual-chamber device and newly diagnosed AF. RNRVAS tends to occur with a long programmed AV delay (such as is often used to avoid ventricular pacing) and a relatively fast lower rate. Reprogramming to shorten the AV delay, decrease the lower rate or decrease the PVARP are the primary methods of correction. Awareness of pacemaker triggered AF may help avoid inappropriate initiation of anticoagulation or other therapies.

Pseudo repetitive non-reentrant ventriculoatrial synchrony: Current challenges.

We recently described a novel pacemaker-mediated arrhythmia in Abbott cardiac implantable electronic devices (CIED), called pseudo-RNRVAS, that mimics repetitive non-reentrant ventriculoatrial synchrony (RNRVAS), but can appear in patients with ventriculoatrial (VA) block. It is caused by sinus-p-waves, trapped in the post-ventricular atrial refractory period (PVARP), which mimic VA conduction. The p-waves are followed by atrial pacing during the myocardial refractory time, which can trigger atrial fibrillation (AF). Pseudo-RNRVAS and RNRVAS are probably more common than appreciated, but the recognition and differentiation of the two can be challenging because most CIEDs do not recognize and store them. We illustrate practical challenges in the assessment of Pseudo-RNRVAS and provide programming options that proved safe and effective for preventing Pseudo-RNRVAS and reducing the risk for typical RNRVAS. We illustrate in 10 patients the characteristics of Pseudo-RNRVAS and their treatment. The outcome regarding the recurrence of pseudo-RNRVAS after 6 months of follow-up was collected. Inappropriate atrial pacing during pseudo-RNRVAS resulted in AF in six patients. After shortening the PVARP in nine, inactivation/reduction of rate response in four, and reduction of the basic pacing rate in one patient, pseudo-RNRVAS was avoided in eight patients and reduced in one. In one patient AF became permanent. Pseudo-RNRVAS is a pacemaker-mediated arrhythmia that can appear in patients without VA conduction and may lead to AF. The suggested adjustments of pacing parameters were safe and effective in preventing the arrhythmia.

Potential triggering of repetitive nonreentrant ventriculoatrial synchrony by loss of atrial capture

Data on the factors that trigger repetitive nonreentrant ventriculoatrial synchrony (RNRVAS) are limited. We hypothesize that loss of atrial capture may trigger RNRVAS. We aimed to use an atrial threshold test to observe the development of RNRVAS upon loss of atrial capture in patients with implantable cardiac electronic devices (CIED). Patients with DDD mode CIEDs [177 patients, 67.5± 14.8 (70) years; 70 women] were included. Atrial threshold test was done in DDD mode at a rate at least 10 beats above the basal heart rate, with an AV delay of 300 ms (range 250-350). A multivariable logistic regression model was used to assess the independent predictors of RNRVAS. RNRVAS was observed in 69 of the 177 patients (39.0%) during atrial threshold test. In patients with VA conduction, incidence of RNRVAS increased to 76.7%. In univariate analysis, younger age (p= .038) and the presence of VA conduction (p< .001) were associated with an increased risk of RNRVAS, whereas complete AV block or any AV node conduction defect (p< .001) and the ventricular pacing ratio (p= .001) were inversely related to the risk of RNRVAS occurrence after loss of atrial capture. In multivariate analysis complete AV block (p= .009) and ventricular pacing ratio (p= .029) appeared as independent factors inversely related to the risk of RNRVAS development. In this study, we demonstrated that loss of atrial capture results in RNRVAS in one-third of patients with a CIED in DDD mode, and in three-fourths of those with VA conduction under certain predisposing CIED settings.

Novel Pacemaker-Mediated Arrhythmia Without Ventriculoatrial Conduction Can Induce Atrial Fibrillation

Cardiovascular implantable electronic devices can initiate and sustain pacemaker-mediated arrhythmias. Endless loop tachycardia and repetitive non-re-entrant ventriculoatrial synchrony (RNRVAS) are well-described examples of pacemaker-mediated arrhythmias. However, such arrhythmias only occur in the presence of ventriculoatrial conduction. We identified a novel pacemaker-mediated arrhythmia that closely mimics RNRVAS but in the absence of ventriculoatrial conduction. We identified these arrhythmias in 9 patients, all with a St. Jude Medical/Abbott device, recorded as inappropriate mode-switch episodes by a device algorithm that includes paced events in the atrial counter. This report describes the mechanism, discusses clinical implications, and outlines programming options to eliminate this pseudo-RNRVAS.

Complete Atrioventricular Block with Intact Retrograde Conduction in Cardiac Rhythm Management Devices: Implications of the Phenomenon.

Intact retrograde ventriculoatrial (VA) conduction in the presence of complete atrioventricular (AV) heart block has been well-documented in the past. We sought to describe the prevalence and clinical significance of intact VA conduction accompanied by complete antegrade AV block in patients with implanted cardiac rhythm management (CRM) devices. During routine follow-up of CRM devices in our device clinic, 42 patients were found to be in a state of complete heart block. All patients presented in sinus rhythm. The patients’ underlying rhythms were tested with the inhibition of pacing and documented AV dissociation. Subsequently, retrograde VA conduction was tested with ventricular pacing. In the 42 patients with complete heart block as the underlying rhythm, five patients demonstrated retrograde VA conduction. In conclusion, the prevalence of intact of VA conduction was 11.9% in our study. The implications of this phenomenon can have noteworthy clinical significance. The occurrence of pacemaker-mediated tachycardia and repetitive nonreentrant VA synchrony are discussed herein. All patients, even those with a device indication of complete heart block, should be tested for retrograde conduction at implantation and during routine follow-up.

A Case of a Cardiac Resynchronization Therapy-Defibrillator Exhibiting a Lower and Alternately Variable Basic Rate

A cardiac resynchronization therapy defibrillator (CRT-D) (Medtronic Inc. Protecta XT) was implanted in a 67-year-old man who had cardiac sarcoidosis with extremely low cardiac function. He had ventricular tachycardia which was controlled by catheter ablation, medication and pacing. The programmed mode was DDI, lower rate was 90 beats/minute, paced AV delay was 150 ms, and the noncompetitive atrial pacing (NCAP) function was programmed as 300 ms.After his admission for pneumonia and heart failure, we changed his DDI mode to a DDD mode because he had atrial tachycardia, which led to inadequate bi-ventricular pacing. After a while, there were cycle lengths which were longer than his device setting and alternately varied. We were able to avoid this phenomenon with AV delay of 120 ms and NCAP of 200 ms.NCAP is an algorithm which creates a gap above a certain period after the detection of an atrial signal during the postventricular atrial refractory period of the pacemaker. This is to prevent atrial tachycardia and repetitive non-reentrant ventriculoatrial (VA) synchrony in the presence of retrograde VA conduction. But in this case, NCAP algorithm induced much lower rate than the programmed basic lower rate. This situation produced some arrhythmias and exacerbated symptoms of heart failure. This had to be paid attention to, especially when the device was programmed at high basic heart rate.

Repetitive nonreentrant ventriculoatrial synchrony: An underrecognized cause of pacemaker-related arrhythmia

Similar to endless loop tachycardia (ELT), repetitive nonreentrant ventriculoatrial synchrony (RNRVAS) is a ventriculoatrial (VA) synchrony pacemaker-mediated arrhythmia. RNRVAS was first described in 1990 and can only occur in the presence of retrograde VA conduction and dual-chamber or cardiac resynchronization devices with tracking (P-synchronous ventricular pacing such as DDD, DDDR) or nontracking pacing modes that allow AV-sequential pacing (DDI, DDIR). RNRVAS is promoted by (1) high lower rate limit or any feature that allows rapid pacing, (2) long AV intervals, or (3) long postventricular atrial refractory period (PVARP). In contrast to ELT, RNRVAS is a less well-recognized form of pacemaker-mediated arrhythmia; thus, unlike ELT, there are no specific device algorithms to prevent, recognize, and terminate RNRVAS. However, RNRVAS has been recently shown to occur frequently. We present a series of cases, some of which were found fortuitously. Owing to its clinical implications, we propose that algorithms should be developed to prevent, identify, and terminate RNRVAS.

Repetitive non-reentrant ventriculoatrial synchrony: a rare cause of overestimating atrial fibrillation burden

Device interrogation of an asymptomatic pacemaker recipient (St Jude Medical Accent DR) following ablation of atrial fibrillation (AF), revealed 29 auto mode switch (AMS) episodes, thus raising the suspicion of asymptomatic AF recurrences. However, all stored AMS episodes were due to repetitive non-reentrant ventriculoatrial synchrony (RNRVAS). In St Jude Medical devices, …

Ventriculoatrial conduction and related pacemaker-mediated arrhythmias in patients implanted for atrioventricular block: An old problem revisited

Ventriculoatrial (VA) conduction and related pacemaker-mediated tachyarrhythmias (PMT) have not been systematically investigated in a large cohort of patients implanted for symptomatic atrioventricular (AV) block. Two hundred fifty consecutive patients (71±14 years, 63% male) implanted for symptomatic second- or third-degree AV block were screened for retrograde VA conduction and related PMTs including endless loop tachycardia (ELT) and repetitive nonreentrant VA synchrony (RNRVAS). After a mean post-implantation period of 38±12 months, AV block was persistent in 137 (55%) and variable in 113 (45%) patients. Retrograde 1:1 conduction was present in 76 patients (30%) with a mean VA conduction time of 258±65 ms. The incidence of VA conduction varied considerably according to the presence and type of anterograde conduction block. Retrograde conduction was present in 24 of 137 patients (18%) with persistent AV block. Fifteen of the 76 patients (20%) with VA conduction had ≥1 documented PMT. The recorded arrhythmias were ELT in 11 and RNRVAS in 4 patients. VA conduction time was significantly longer in patients with than without PMT (297±64 vs. 249±62 ms, resp., P<0.01). None of the patients without VA conduction had documented PMTs. Retrograde VA conduction and related PMTs are not uncommon in patients implanted for symptomatic AV block. Testing for retrograde conduction should therefore be performed in all patients with AV block in order to optimize device programming and prevent PMTs.

A case of repetitive nonreentrant ventriculoatrial synchrony exacerbating heart failure in dilated cardiomyopathy

A 67-year-old man with poor left ventricular function due to a dilated cardiomyopathy was implanted with an implantable cardioverter defibrillator for secondary prevention. Eight years later, he was admitted to our hospital with worsening of heart failure. An electrocardiogram showed a repetitive nonreentrant ventriculoatrial synchrony (RNRVAS). RNRVAS is a device-related arrhythmia that can occur when a dual-chamber pacemaker does not sense a retrograde P wave within the postventricular atrial refractory period, resulting in a repetitive ventricular pacing and noncaptured atrial pacing after the retrograde P wave. We suspected that ventricular pacing caused his heart failure and used the noncompetitive atrial pacing algorithm, which was programmed to prevent RNRVAS. The algorithm was able to prevent the arrhythmia, and the patient successfully recovered from heart failure.

Pacemaker repetitive nonreentrant ventriculoatrial synchrony. Why did automatic mode switching occur?

Repetitive nonreentrant ventriculoatrial synchrony during dual-chamber pacing is characterized by long intervals alternating with short intervals. This arrangement activated automatic mode switching in a St Jude dual-chamber pacemaker in which the algorithm requires an atrial sensed event for automatic mode switching initiation. Automatic mode switching activation by an atrial sensed event (retrograde P wave) was puzzling because the programmed postventricular atrial period was longer than the retrograde ventriculoatrial conduction time. The explanation is presented in the form of questions and answers to facilitate the understanding of pacemaker function and complex timing cycles.

Optimal Setting of “Stored Electrogram” Algorithms in Pacemakers for Detection of Repetitive Non-Reentrant Ventriculoatrial Synchrony (RNRVAS)

Background: RNRVAS is a pacemaker-related adverse phenomenon that causes AV asynchrony and compromises hemodynamics especially in reduced cardiac function. With technical limitations, automatic detection of RNRVAS is still difficult in currently distributed devices. Therefore, the occurrence of RNRVAS is unclear. Purpose: To establish the method for detecting RNRVAS by adjusting the setting of storing electrograms (EGM) in a pacemaker (Method) Three of EGM-storing methods ((A) “High Atrial Rate” , (B) “AMS Entry or Exit”, and (C) “AT/AF Detection”) in a biventricular pacemaker (Fronitier II, SJM) were evaluated in terms of detection of RNRVAS. According to each of algorithms, we calculated and estimated the response in three methods for detecting RNRVAS, and subsequently undergo the simulation to reproduce the response in each of methods by using a pacemaker and a simulator. Result: Method (A) failed to detect any episodes of RNRVAS due to “short-long” alternating sequence of atrial events. With occurrence of atrial premature beats, method (B) could detect some of RNRVAS events even if atrial tachycardia detection rate (ATDR) is high. Method (C) could detect most of RNRVAS events and its durations by optimizing ATDR. The present result corresponded to our computation of the response in three methods. Conclusion: We suggest that the optimal method for detection of RNRVAS be the “AF/AT detection” algorithm.

Overestimation of Atrial Tachyarrhythmia Detection in Pacemaker Patients with High Cumulative% of Atrial Pacing

Background: Although atrial high rate episodes (AHRE) have been commonly used to detect atrial tachyarrhythmias (AT/AF) in pacemaker patients, its reliability and characteristics are unclear. Methods and Results: 39 patients with implanted dual chamber pacemakers (mean age 79.7±6.6 years), who had no history of AT/AF and were programmed in the setting of AHRE at >190 beats/min in DDD mode, were studied. An atrial overdrive pacing (AOP) algorithm was randomly programmed “ON” in 19 and “OFF” in 20 patients. AHRE were detected in 20 patients (51%), consisting of AT/AF in 15 and repetitive non-reentrant ventriculoatrial synchrony (RNRVAS) in 8 patients, all included in the AOP “ON” group. A total of 257 of 1,528 episodes of AHRE were available for analysis, including 181 and 76 episodes in the AOP “ON” and “OFF” groups, respectively. Among 181 episodes in the AOP “ON” group, 72 (40%) were RNRVAS, whereas all episodes in the AOP “OFF” group (100%) were AT/AF. Detection of RNRVAS was closely associated with a high cumulative% atrial pacing. The specificity of AT/AF detection by AHRE was 40% when the AOP algorithm was activated, vs. 100% when not in use. Conclusions: AT/AF was common in pacemaker patients without a history of AT/AF. The increase in cumulative% atrial pacing and the use of an AOP algorithm might be closely associated with RNRVAS, non-AT/AF, detected by AHRE.

Reliability and Characteristics of Atrial Tachyarrhythmias Detection in Dual Chamber Pacemakers

Although atrial high rate episodes (AHRE) have been commonly used to detect atrial tachyarrhythmias (AT/AF) in pacemaker patients, its reliability and characteristics are unclear. 39 patients with implanted dual chamber pacemakers (mean age 79.7 ± 6.6 years), who had no history of AT/AF and were programmed in the setting of AHRE at > 190 beats/min in DDD mode, were studied. An atrial overdrive pacing (AOP) algorithm was randomly programmed "ON" in 19 and "OFF" in 20 patients. AHRE were detected in 20 patients (51%), consisting of AT/AF in 15 and repetitive non-reentrant ventriculoatrial synchrony (RNRVAS) in 8 patients, all included in the AOP "ON" group. A total of 257 of 1,528 episodes of AHRE were available for analysis, including 181 and 76 episodes in the AOP "ON" and "OFF" groups, respectively. Among 181 episodes in the AOP "ON" group, 72 (40%) were RNRVAS, whereas all episodes in the AOP "OFF" group (100%) were AT/AF. Detection of RNRVAS was closely associated with a high cumulative % atrial pacing. The specificity of AT/AF detection by AHRE was 40% when the AOP algorithm was activated, vs. 100% when not in use. AT/AF was common in pacemaker patients without a history of AT/AF. The increase in cumulative % atrial pacing and the use of an AOP algorithm might be closely associated with RNRVAS, non-AT/AF, detected by AHRE.

Pacemaker repetitive nonreentrant ventriculoatrial synchronous rhythm. A review.

Ventriculoatrial (VA) synchrony during dual chamber pacing can occur in any patient who has the ability to sustain repeated retrograde conduction. If the retrograde P wave is sensed, the result will be an endless loop tachycardia or repetitive reentrant VA synchrony. VA synchrony can also occur when a dual chamber pacemaker does not sense a retrograde P wave within the postventricular atrial refractory period. In this situation if the normally suprathreshold atrial stimulus at the end of the atrial escape interval is continually delivered when the atrial myocardium is physiologically refractory, the result will be a repetitive nonreentrant VA synchronous rhythm. Repetitive nonreentrant VA synchrony may produce unfavorable hemodynamic consequences and the pacemaker syndrome. It represents an example of functional atrial undersensing combined with functional loss of atrial capture. Management requires modification of the programmed settings of the pacemaker and utilization of certain algorithms designed for other functions but nevertheless effective in this situation.