Background: The identification of the pattern of the muscular connections between pulmonary vein (PV) and the left atrium (LA) is important for efficient PV isolation (PVI), which is central to the catheter ablation (CA) of atrial fibrillation (AF). We investigated the characteristics of the LA-PV muscular connection in patients with AF and whether they are differ between paroxysmal (PAF) and persistent AF (PeAF). Methods: Eighty patients with AF (57 PAF, M;F=46:11, 53.2짹10.1 yrs old and 23 PeAF,M:F=19:4, 55짹8.7 yrs old) who underwent CA were included. PVI was done by guidance of NavX system and confirmed by elimination of PV potentials (PVPs) on Lasso catheter positioned at the each PV ostium. The numbers of LA-PV connecting fascicles are calculated by the number of changing sequences of PVPs during CA (open cool tip) at each PV. The sites of elimination of PVPs at each PV were divided into 5 sectors (anterior, posterior, superior, inferior, and carina). Common PV ostium was excluded. Results: The average number of each PV fascicles was higher in superior than inferior PVs [2.2 in left superior PV (LSPV), 2.0 in right superior PV (RSPV), 1.7 in right inferior PV (RIPV), and 1.4 in left inferior PV (LIPV)]. The number of each PV fascicles in PeAF was higher than those in PAF (2.4 vs. 2.0 in LSPV, 1.7 vs. 1.2 in LIPV, 2.0 vs. 1.6 in RIPV), except in RSPV (2.0 vs. 2.1). Among 5 sectors of PV ostium, the most common site of PVP elimination was carina of each side of PVs (52.9% in LSPV, 46.1% in RSPV, 40.5% in LIPV, and 32.4% in RIPV), and this was similar in PAF as in PeAF. Acute reconnection of PVPs before the end of procedure (<30 minutes) was found in multiple (3.2짹1.4 in LSPV, 3.2짹1.3 in RIPV, 2.3짹1.0 in RSPV, and 2.0짹0.6 in LIPV) fascicular PVs, compared to those without reconnection of PV. Conclusions: Muscular connection of superior PVs with the LA was more complex than those with inferior PVs, which was more obvious in PeAF than PAF and was related to acute reconnection of PVs. The critical fascicles connecting the LA were mostly localized at the carina. Understanding of LA-PV muscular connection pattern helps clarify the implication for efficient PVI and better outcome after CA for AF.