Position-Dependent and Hidden Atrioventricular Dyssynchrony in Micra AV Leadless Pacemaker.

Micra AV leadless pacemakers aim to maintain atrioventricular (AV) synchrony across various body positions. This report describes a case of position-dependent AV dyssynchrony in an 81-year-old man with nocturnal palpitations despite having normal routine evaluations. Rate histogram analysis revealed an unusual distribution pattern, and manual atrial mechanical (MAM) testing demonstrated an increased A3 signal amplitude in the left lateral position, which resulted in oversensing. Adjusting the A3 threshold and window end settings resolved the symptoms and normalized the rate histogram. This case highlights the importance of position-dependent signal variations and rate histogram analyses in patients with a Micra AV.