Dual Atrioventricular Nodal Physiology in Sinus Rhythm: An Extraordinary Manifestation of a Common Substrate

A 32-year-old woman was evaluated for experiencing episodes of palpitations, which were never documented. Complementary test results were normal. A 12-lead Holter monitor was requested, and a manifestation of dual nodal physiology was observed. This was key to indicate an electrophysiological study, as this increased pretest likelihood of atrioventricular nodal re-entry tachycardia. In the electrophysiological study, we identified 2 families of atrio-hisian intervals of 106 milliseconds and 304 milliseconds, respectively, with an his-ventricular interval of 52 milliseconds. With atrial programmed stimulation, a nodal jump was evidenced, and a regular, narrow QRS tachycardia with atrioventricular relation of 1:1 and a ventriculo-atrial interval of 19 milliseconds was induced, which is compatible with atrioventricular nodal reentry tachycardia, so slow pathway ablation was performed.

Manifestations of dual nodal pathways are uncommon in sinus rhythm, but they should be recognized, as they demonstrate a potential arrhythmic substrate in patients with palpitations.