Background: This study investigated the electrophysiologic characteristics and outcome of superior vena cava (SVC) segmental ostial isolation (SOI) in patients with SVC-initiated paroxysmal atrial fibrillation (PAF). Methods: Ninety-five patients with PAF underwent pulmonary vein (PV) SOI using a basket catheter whether the PAF originating from PVs was observed or not. Fifteen of those patients also underwent SVC SOI in the same manner due to evidence of SVC origin PAF. Results: The SVC musculature networks and electrical connections with the atrium (multiple separate electrical connections in 10, multiple separate musculature networks with separate electrical connections in 1, and a continuous broad electrical connection in 4 SVCs) were similar to those of the PV musculature. However, the occurrence of an electrical connection recovery after SOI in patients with recurrent atrial fibrillation was lower for SVCs (25%) than PVs (58%). Conclusions: Superior vena cava SOI appears to have a lower recurrent conduction rate than PV SOI. © 2007 Elsevier Inc. All rights reserved.