B-PO04-222 ELECTRIC CARDIOVERSION DURING SINUS RHYTHM TO ASSESS PULMONARY VEIN ISOLATION

Abstract

Pulmonary vein (PV) isolation for the treatment of atrial fibrillation (AF) is a safe and effective intervention. Most recurrences post ablation are due to reconnection of a PV, highlighting the importance of a robust assessment of PV isolation. To describe a situation where an electrical cardioversion was performed in a patient in sinus rhythm while one PV was still in AF, revealing residual exit and entrance conduction despite apparent exit block. N/A We present the case of a 58 year old gentleman who was referred for AF ablation. During ablation around the left superior PV (LSPV), the rhythm changed to typical atrial flutter, while the LSPV persisted in AF. Cavo-tricuspid isthmus ablation was performed after completing the wide antral circumferential ablation, leaving the circumferential mapping catheter in the LSPV. When sinus rhythm was restored, the PV remained in AF, with exit block. Electrical cardioversion using 100 Joules was performed, terminating PV fibrillation, and revealing residual entrance and exit conduction. Exit conduction was intermittent while pacing at 600 ms. Subsequently, further ablation was delivered until entrance and exit block were demonstrated. This case highlights the importance of performing electrical cardioversion when a PV is in AF, despite the patient being in sinus rhythm, to truly confirm the existence of PV isolation. We believe that the bombarding impulses of the fibrillating PV can provoke an inhibition of the exit conduction due to concealed conduction that makes the slow conducting tissue refractory, preventing propagation to the left atrium. This may then lead to the misdiagnose of exit block.