MVP safely achieves functional atrial pacing by limiting ventricular pacing to periods of intermittent AVB and AF in ICD patients, significantly reducing Cum%VP compared to DDD/R. MVP is a universal pacing mode that adapts to AVB and AF, providing both atrial pacing and ventricular pacing support when needed.

A 25-year-old runner received a single-lead, VDD pacemaker after ablation of AV nodal reentrant tachycardia complicated by intermittent AV block. The rateadaptive AV delay algorithm (RAAV), which shortens the sensed AV interval (SAV) at faster atrial rates, was programmed to provide a physiologic SAV with exercise.She developed repetitive, atypical, long-RP pacemaker-mediated tachycardia (PMT) because the RAAV shortened the antegrade SAV and retrograde conduction occurred over the slow AV nodal pathway. PMT was refractory to usual programming solutions. Using high-density electroanatomic mapping, we were able to ablate the retrograde limb of PMT without further damaging AV conduction. K E Y W O R D S cardiac mapping -3-dimensional systems, implantable devicespacemaker-bradyarrhythmias, implantable devicesphysiologic pacing

BackgroundPower‐on reset (PoR) is most commonly due to electromagnetic interference. Full PoR results in a switch to an inhibited mode (VVI) pacing and resets pacing outputs to maximal unipolar settings, leading to extracardiac stimulation.MethodsWe present a case of PoR occurrence in the absence of electromagnetic interference, resulting in pectoral stimulation triggered by violation of the atrial rate limit.ConclusionsIt is useful for clinicians to recognizethe occurrence of PoR in the setting of atrial limit violation andthe appropriate management in such circumstances.

This report describes the occurrence of a repetitive nonreentrant ventriculoatrial (VA) synchronous rhythm precipitated by the noncompetitive atrial pacing algorithm of a Medtronic DDDR pacemaker. This algorithm delivers an atrial stimulus 300 ms after the detection of an atrial signal in the postventricular atrial refractory period of the pacemaker. In our patient, the atrial stimulus released by the algorithm was ineffectual because it encountered prolonged refractoriness of the atrial myocardium. This situation produced a repetitive nonreentrant VAl synchronous rhythm in the setting of retrograde VA conduction.