Bidirectional conduction block between left atrium (LA) and pulmonary vein (PV) is the endpoint of PV isolation. A 71-year-old man with drug- resistant atrial fibrillation underwent PV isolation. Although the vast majority of PV activity was dissociated from atrial activity, some conducted to LA which resulted in premature atrial contractions (see the figure). Disappearance of PV potential in sinus rhythm suggests entrance block from LA to PV. The existence of dissociated PV activity usually proves the exit block from PV to LA. This case highlighted the importance of careful observation of isolated PV activity and the confirmation of bidirectional conduction block.
Conflict of interest: none declared.
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