Methods, Merits, and Complex Considerations in Restoring Atrioventricular Synchrony in Patients with Heart Failure

While ventriculoventricular (VV) synchrony has long been known to be important, especially in patients with heart failure (HF) (e.g. cardiac resynchronization therapy), the importance of atrioventricular (AV) synchrony is a more recent area of interest. Growing literature suggests that markedly prolonged PR intervals (i.e. > 300ms) may affect morbidity, especially in patients with HF. Of course, improving AV synchrony in heart failure patients is a common goal amongst heart failure and electrophysiology teams; but like our mission to improve interventricular synchrony, improving AV synchrony may require more scrutiny. Specifically, we call attention to look beyond the "PR" interval when considering patients with HF for AV pacing. In this article, we aim to highlight an under-appreciated phenomenon, where conduction time across diseased atria requires a prolonged PR interval to avoid a left-sided "pseudo left-sided pacemaker syndrome". In fact, the introduction of a pacemaker in certain patients may introduce a so-called Mousetrap Phenomenon by creating AV dyssynchrony through paced normalization of the PR interval.