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

Pseudo repetitive non-reentrant ventriculoatrial synchrony: Current challenges

BACKGROUND

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.

OBJECTIVE

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.

METHODS AND RESULTS

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.

CONCLUSIONS

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

BACKGROUND

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).

METHODS

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.

RESULTS

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.

CONCLUSION

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.

A sudden change in pacing rate: Normal or malfunction?

A woman with a dual‐chamber pacemaker was examined for recurrent chest discomfort and palpitations at our hospital. The Holter monitor test recorded recurrent episodes of a sudden increase in pacing rate from 60 to 105 bpm, which corresponded to the symptoms. Orthodromic pacemaker‐mediated arrhythmia (OPMA), caused by ventricular lead dislodgement and atrial far‐field sensing, caused the recurrent episodes of a sudden change in pacing rate. The occurrence of OPMA may represent a rare but noteworthy pacemaker problem. To our knowledge, our study reports the first case of PMA that only occurs, and is maintained, in the DDI mode.

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.

Is competitive atrial pacing a possible trigger for atrial fibrillation? Observations from the RATE registry

BACKGROUND

A high incidence of asymptomatic atrial tachycardia and atrial fibrillation (AT/AF) has been recognized in patients with cardiac implantable devices (CIED). The clinical significance of these AT/AF episodes remains unclear. Some "device-detected AT/AF" was previously shown to be triggered by competitive atrial pacing (CAP).

OBJECTIVE

To investigate and characterize a potential association between CAP and AT/AF in the largest series of observations to date.

METHODS

RATE, a multicenter registry, included 5379 patients with CIEDs followed for approximately 2 years. Electrograms (EGMs) from 1352 patients with AT/AF, CAP, or both were analyzed by experienced adjudicators to assess a causal relationship between AT/AF and CAP onset, duration, and morphology.

RESULTS

In 225 patients, 1394 episodes of both AT/AF and CAP were present in the same tracing. CAP and AT/AF were strongly associated (P ≤ .02). AT/AF occurred during the course of the study in 71% of patients with CAP. In 62% of the episodes, expert adjudication concluded that CAP triggered AT/AF. The duration and morphology of triggered and spontaneous AT/AF episodes differed. Spontaneous AT/AF episodes were associated with constant EGM morphology, and were either long or extremely short. CAP-triggered AT/AF more often had variable and shorter cycle length EGMs. The incidence of short AT/AF events was higher among triggered episodes (25% vs 12.8%, P < .002).

CONCLUSION

Device-triggered AT/AF due to CAP is likely more common than previously recognized. This AT/AF entity differs from spontaneous AT/AF in duration and morphology. Clinical implications of spontaneous and device-triggered AT/AF may be different.

Proarrhythmic effects from competitive atrial pacing and potential programming solutions

BACKGROUND

Programmed long AV delays and intrinsic long first degree AV block may increase risk for competitive atrial pacing (CAP) in devices without CAP avoidance algorithms.

METHODS

Patients identified with CAP-induced mode switch episodes were followed clinically from September 2013 to August 2019. Attempts to avoid CAP included shortening of postventricular atrial refractory period (PVARP) or postventricular atrial blanking period (PVAB), or change to AAI or DDI modes. After observing associations with sensor-driven pacing, rate response was inactivated in a subset.

RESULTS

Among 23 patients identified with CAP (22 St Jude Medical [Abbott]; one Boston Scientific Corporation devices), atrial fibrillation (AF) was induced in 12 (52%), lasting 10 seconds to 28 hours and 32 minutes. In one patient with an ICD CAP-induced AF with rapid ventricular rates that triggered a shock, inducing ventricular fibrillation, syncope, and another shock. Changing AV delays and shortening of PVARP failed to resolve CAP. After noting that all had CAP during sensor-driven pacing, rate response was inactivated in seven, resolving further device-induced AF in the three of seven that had prior CAP-induced AF. In two patients with intact AV conduction, AAI(R) pacing resolved further documentation of CAP.

CONCLUSIONS

CAP predominantly occurs during sensor-driven atrial pacing that competes with intrinsic atrial events falling in PVARP. Inactivation of the activity sensor or change to atrial-based pacing modes (AAI/R) appears to effectively prevent induction of device-induced atrial proarrhythmia. Ultimately, a corrective algorithm is needed to avoid CAP-induced proarrhythmia.

Proarrhythmic effect of automatic threshold testing algorithm in dual chamber devices

BACKGROUND

Operation of auto-threshold testing (ATT) algorithm in current dual chamber cardiac devices require temporary shortening of atrio-ventricular (AV) delay to accurately measure evoked potential (capture) after a pacing pulse. Near simultaneous AV pacing causes atrial pressure elevation and may be associated with atrial arrhythmias.

OBJECTIVE

We evaluated the prevalence of atrial arrhythmias induced by ATT in Abbott devices.

METHODS

Device clinic records were reviewed at a single center for patients with dual chamber Abbott pacemaker/ICD. ATT-induced atrial fibrillation (AF) cases were defined as new appropriate mode switch episodes while the ATT was operating. The auto-capture test trends were defined as unstable if there were deviations >1 V in capture threshold trend events that did not correlate with routine in-office testing.

RESULTS

One hundred and seventy patients were programmed in dual chamber pacing mode. The ventricular ATT was active in 118 patients and of these 78 had true mode switch episodes. Six patients developed AF during ventricular ATT. Three patients had most recorded atrial arrhythmias in close association with ATT (63%, 66%, 100% vs 2%,9%, 33% in other patients with known prior AF). An unstable auto-capture trend curve was seen in 33 patients (6 showing ATT-induced AF) versus 85 patients with stable auto-capture curve and no ATT-induced AF (P = .0001, the χ² test).

CONCLUSION

Ventricular auto-capture algorithm use is associated with induction of AF in dual chamber Abbott devices with a prevalence of over 5%. AF occur more frequently (18%) in patients with erratic ventricular ATT trend results.

Pacemaker-mediated arrhythmias

Pacemakers can be directly involved in initiating or sustaining different forms of arrhythmia. These can cause symptoms such as dyspnea, palpitations, and decompensated heart failure. Early detection of these arrhythmias and optimal pacemaker programming is pivotal. The aim of this review article is to summarize the different types of pacemaker-mediated arrhythmias, their predisposing factors, and mechanisms of prevention or termination.

A review of the atrial upper rate algorithms of St. Jude Medical (Abbott) cardiac implantable electronic devices : Incidence of repetitive nonreentrant ventriculoatrial synchrony (RNRVAS)

This review focuses on the manifestations of the three triggered atrial upper rate functions of St Jude Medical cardiac implantable electronic devices. The occurrence of repetitive nonreentrant ventriculoatrial synchrony (RNRVAS) is also evaluated as a basis for the development of automatic mode switching (AMS) and as a trigger for atrial tachycardia/atrial fibrillation (AT/AF) event recordings. RNRVAS is a common trigger for AMS because all the atrial events or intervals are used to calculate the filtered atrial rate interval (FARI). Once AMS is initiated, it will also effectively stop RNRVAS because entry into AMS also shortens the postventricular atrial refractory period (PVARP). Recent design developments to eliminate or minimize unusual upper rare responses include the following: (1) P waves in the PVARP are no longer counted towards the FARI if they are followed by an atrial paced event. (2) In new devices the AT/AF detection algorithm substitutes the Moving Average Interval (a relatively complex calculation) with the new FARI average. (3) Improved design of the rate-responsive PVARP with a far more aggressive response than in the past (enhanced atrial protection interval).