Introducing a Novel Pacemaker-Mediated Arrhythmia: The Pseudo-RNRVAS Arising From Atrial Capture Challenges

Abstract

Background: This study aimed to define and explain a novel form of pacemaker-mediated arrhythmia which is initiated and sustained by atrial capture loss coinciding with ventriculoatrial (VA) conduction within the postventricular atrial refractory period (PVARP). Unlike repetitive nonreentrant VA synchrony (RNRVAS), in the pseudo-RNRVAS, the atrium is not stimulated due to pacing below the threshold level, rather than because of refractory atrial myocardium.

Objective: The objective was to elucidate the mechanisms of this pseudo-RNRVAS, identify predisposing factors, and propose preventive strategies.

Methods: Twenty-one patients with dual-chamber cardiac implantable electronic devices (CIEDs) exhibiting stable VA conduction within the PVARP were included. Pseudo-RNRVAS were induced by altering atrial amplitude and lower rate interval while keeping other CIED parameters constant.

Results: Pseudo-RNRVAS developed after atrial capture loss in 20 out of 21 patients. Notably, 11 patients experienced pseudo-RNRVAS at heart rates ≤ 70 bpm, and 7 patients at AV delay ≤ 150 ms. The condition initiated immediately following the first ventricular pace beat after atrial capture loss in 18 patients. In six cases, pseudo-RNRVAS terminated intermittently and then restarted; in 14 cases, it did not resolve.

Conclusion: Pseudo-RNRVAS can occur even at low heart rates and without specific predisposing factors seen in RNRVAS. Conditions that increase atrial pacing probability and threshold raise the likelihood of pseudo-RNRVAS. Early postimplantation may pose a heightened risk, correlating with pacemaker syndrome and susceptibility to heart failure.

Keywords: RNRVAS; endless loop tachycardia; loss of atrial capture; pacemaker‐mediated arrhythmia; pacemaker‐mediated tachycardias; pseudo‐RNRVAScardiac implantable electronic device; repetitive nonreentrant ventriculoatrial synchrony.

FIGURE 1

Recordings of RNRVAS, pseudo‐RNRVAS, and ELT obtained from the same patient with St Jude Medical device. (A) Record of RNRVAS recorded as AHRE. (B) Record of pseudo‐RNRVAS developed following atrial capture loss. (C) Record of ELT developed following atrial capture loss at atrial threshold test. In RNRVAS, the atrium is not stimulated due to the refractoriness of the atrial myocardium. The interval between retrograde VA conduction and atrial pacing must be short enough to coincide with the atrial myocardial refractory period. In pseudo‐RNRVAS, this requirement is not necessary, so the interval between retrograde VA conduction and atrial pacing can be much longer, allowing pseudo‐RNRVAS to occur at much lower heart rates. The interval between atrial pacing and retrograde VA conduction within the PVARP is measured as 240 ms with a heart rate of 77 bpm in the RNRVAS recording (A) and 500 ms with a heart rate of 60 bpm in the pseudo‐RNRVAS recording (B). Despite this difference, RNRVAS and pseudo‐RNRVAS share similar electrophysiological characteristics and electrogram appearance. AP, atrial pace; AR, atrial activity sensed in PVARP; AS, atrial sense; ELT, Endless loop tachycardia; RNRVAS, repetitive nonreentrant ventriculoatrial synchrony; SIR, sensor‐indicated rate; VP, ventricular pace.

FIGURE 2

This recording demonstrates the onset and termination of an pseudo‐RNRVAS due to atrial capture loss in a patient with atrial pacing rhythm using a St Jude Medical device. (A) When the atrial pace amplitude is programmed to induce atrial capture loss, the initial noncaptured atrial pacing initiates ventricular pacing followed by VA conduction, resulting in the development of an pseudo‐RNRVAS. (B) When the atrial pace amplitude is programmed to appropriate values, the pseudo‐RNRVAS terminates after the first captured atrial pacing beat. AP, atrial pace; AS, atrial sense; RNRVAS, repetitive nonreentrant ventriculoatrial synchrony; VP, ventricular pace; VS, ventricular sense.

FIGURE 3

This recording demonstrates the onset and termination of an pseudo‐RNRVAS due to atrial capture loss in a patient with sinus rhythm using Boston Scientific and Medtronic devices. When the atrial pace amplitude and pacing lower rate interval are programmed to induce atrial pacing and atrial capture loss, the initial noncaptured atrial pacing initiates V pacing followed by VA conduction, resulting in the development of an pseudo‐RNRVAS in Boston Scientific device A and Medtronic device C. When the atrial pace amplitude and pacing lower rate interval are programmed to previous values, the pseudo‐RNRVAS terminates after the first captured atrial pacing beat in Boston Scientific devices B and the first sensed atrial beat in Medtronic device C. (A) Boston Scientific device A. (B) Boston Scientific device B. (C) Medtronic device C. A, atrium; AP, atrial pace; AR, atrial activity sensed in PVARP; AS, atrial sense; LVP, left ventricular pace; RNRVAS, Repetitive nonreentrant ventriculoatrial synchrony; RV, right ventricul; RVP, right ventricular pace; VP, ventricular pace; VS, ventricular sense.

FIGURE 4

This recording illustrates the onset and termination of an pseudo‐RNRVAS due to atrial capture loss in a patient with variable sinus rate using a St Jude Medical device. (A) When the atrial pace amplitude is programmed to induce atrial capture loss, atrial pacing initiates but results in atrial noncapture, and ventricular pacing commences. (B) As sinus activity progressively occurs later after V pacing, VA conduction initiates, leading to the development of an pseudo‐RNRVAS. As the sinus rate increases towards the end of the recording, VA conduction ceases, and sinus activity approaches V pacing. (C) When the sinus rate exceeds the atrial pace rate, the AsVs function of the pacemaker initiates. Toward the end of the recording, when sinus rate slows down, atrial pacing begins but capture fails, resulting in V pacing and VA conduction in the final beat. (D) Rhythm in this recording continues as a continuous pseudo‐RNRVAS. AP, atrial pace; AS, atrial sense; RNRVAS, repetitive nonreentrant ventriculoatrial synchrony; VP, ventricular pace; VS, ventricular sense.