Background: Extensiveness of conduction delay and block at the pulmonary vein area (PVA) was quantified in a previous study. We hypothesized that the combination of lines of conduction block with multiple concomitantly entering sinus rhythm wavefronts at the PVA may result in increased arrhythmogenicity and susceptibility to atrial fibrillation (AF). Methods: Intraoperative high-density epicardial mapping of PVA (N≈450 sites, interelectrode distances: 2 mm) was performed during sinus rhythm in 327 patients (241 male [74%], 67±10 [21–84] years) with and without preoperative AF. For each patient, activation patterns at the PVA were quantified, including the location of entry sites of wavefronts, direction of propagation, and their relative activation times. The association between activation patterns and the presence of AF was examined. Results: Excitation of the PVA occurred via multiple consecutive wavefronts in the vast majority of patient (N=216, 81%). In total, 561 wavefronts were observed, which mostly propagated through the septal or paraseptal regions towards the PVA (N=461, 82%). A substantial dissociation of consecutive wavefronts was observed with Δactivation times of 10.6±8.8 (0–46) ms. No difference was observed in Δactivation times of consecutive wavefronts during sinus rhythm between patients without and with AF. An excitation-based risk factor model, including conduction delay ≥6 mm, conduction block ≥6 mm, and conduction delay and block ≥16 mm, wavefronts via the posteroinferior to posterosuperior regions and multiple opposing wavefronts, demonstrated a 5-fold risk of AF when multiple risk factors were present. Conclusions: In contrast to previous findings, quantification of activation patterns at the PVA on high-resolution scale demonstrated complex patterns with often multiple entry sites and high interindividual variability. Altered patterns of activation, consisting of multiple opposing wavefronts combined with long lines of conduction slowing, were associated with the presence of AF.