Periodic conduction and 2:1 block from the left atrium to the pulmonary vein during radiofrequency ablation

Paroxysmal atrial fibrillation is often initiated by foci in the pulmonary veins (PVs); the junction between the PVs and the left atrium (LA) has become the target of radiofrequency (RF) ablation performed to isolate the PVs. Ectopic atrial beats originating from the PVs propagate to the LA with a characteristically long conduction time, often with a conduction delay or block within the PV or at the PV-LA junction. However, details about the conduction properties within the PVs and across the PV-LA junction are still scanty. We report a unique case of LA-PV decremental conduction caused by RF applications. New insights into the electroanatomical characteristics of the PV-LA junction are provided. The present report demonstrates, for the first time in humans, that decremental conduction may be related to the progressive damage of the conducting myocardial bundle due to RF energy applications.