Occurrence of unexpected ventriculoatrial block during parahisian pacing: What is the mechanism?

A 68-year-old man with documented supraventricular tachycardia was admitted to our hospital for electrophysiological study and catheter ablation. He had no structural heart disease. Baseline electrocardiogram did not show any evidence of pre-excitation. The electrode catheters were positioned at the high right atrium, parahisian region, coronary sinus, and right ventricular apex (RVA). Constant ventricular pacing from the RVA at a cycle length (CL) of 600 ms showed intact ventriculoatrial (VA) conduction.
Source: Heart Rhythm - Category: Cardiology Authors: Tags: Unknown of the Month Source Type: research