Catheter-induced 3:1 second degree atrioventricular nodal block during atrioventricular nodal reentrant tachycardia.

Second-degree atrioventricular (AV) nodal block with 2:1 AV conduction during atrioventricular nodal reentrant tachycardia (AVNRT) has been previously described. We report a patient who developed AVNRT during which 3:1 intra-infra-Hisian block due to catheter manipulation was observed. This was followed by gradual, incremental recovery of AV conduction. AVNRT accounts for approximately 50% of cases of supraventricular tachycardia. This mechanism of tachycardia uses a reentrant circuit in the region of the AV Node which usually contains distinct slow and fast pathways. Radiofrequency ablation of the slow pathway is an effective and safe treatment for AVNRT . In this report, we present a patient with AVNRT of the common type who developed 3:1 intra-infra-Hisian block during AVNRT as a result of catheter manipulation. Before resumption of normal 1:1 conduction, we observed split His potentials in normal sinus rhythm, followed by atrioventricular (AV) nodal echo beats with intra-infra-Hisian block.