2:1 electronic AV block due to inappropriate automatic post-ventricular atrial refractory period extension

A 16-year-old female with dual-chamber pacemaker (Medtronic Azure XT DR), due to symptomatic third-degree congenital atrioventricular (AV) block, presented to our ambulatory with dizziness and presyncopal episodes preceded by prodromes, occurring over the last few months. The device was programmed in DDD mode with an upper rate of 150 bpm. A head-up Tilt Test (HUTT) revealed the unexpected emergence of 2:1 electronic AV block at a sinus rate of 130 bpm.