Heterologous Atrial-Only Leadless Rescue of Pacemaker Syndrome With Preserved Atrioventricular Conduction

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  Visual Summary. Physiology-Guided Atrial-Only Leadless Rescue of Pacemaker Syndrome Persistent dyspnea after prior Micra AV implantation prompted physiologic evaluation despite preserved LVEF and normal prosthetic valve function. ECG showed ventricular pacing with retrograde P waves, and exercise testing identified preserved antegrade AV nodal conduction. Because transvenous upgrade remained undesirable and prior Micra extraction was avoided, an atrial-only leadless strategy was selected. Implantation of an Aveir atrial leadless pacemaker restored AV synchrony through the native AV node, reduced ventricular pacing to 0.1%, and resolved symptoms. AV = atrioventricular; ECG = electrocardiogram; LVEF = left ventricular ejection fraction.

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  Figure 1. Electrocardiographic Findings Before and After Atrial-Only Leadless Rescue (A) The baseline electrocardiogram showed ventricular paced rhythm with retrograde P waves, consistent with ventriculoatrial conduction and atrioventricular dyssynchrony. (B) During exercise, intermittent intrinsic junctional atrioventricular nodal conduction emerged and competed with Micra-mediated ventricular pacing. (C) With rate response activation, ventricular pacing again predominated and suppressed the accelerated junctional rhythm. (D) After atrial leadless pacemaker implantation, the electrocardiogram showed atrial pacing with intact antegrade atrioventricular conduction, with the prior Micra programmed in ventricular paced, ventricular sensed, inhibited response mode as low-rate backup ventricular pacing.