Masayuki Takamura

Background An epicardial connection (EC) through the intercaval bundle (EC‐ICB) between the right pulmonary vein (RPV) and right atrium (RA) is one of the reasons for the need for carina ablation for PV isolation and may reduce the acute and chronic success of PV isolation. We evaluated the intra‐atrial activation sequence during RPV pacing after failure of ipsilateral RPV isolation and sought to identify specific conduction patterns in the presence of EC‐ICB. Methods and Results This study included 223 consecutive patients who underwent initial catheter ablation of atrial fibrillation. If the RPV was not isolated using circumferential ablation or reconnected during the waiting period, an exit map was created during mid‐RPV carina pacing. If the earliest site on the exit map was the RA, the patient was classified into the EC‐ICB group. The exit map, intra‐atrial activation sequence, and RPV‐high RA time were evaluated. First‐pass isolation of the RPV was not achieved in 36 patients (16.1%), and 22 patients (9.9%) showed reconnection. Twelve and 28 patients were classified into the EC‐ICB and non‐EC‐ICB groups, respectively, after excluding those with multiple ablation lesion sets or incomplete mapping. The intra‐atrial activation sequence showed different patterns between the 2 groups. The RPV‐high RA time was significantly shorter in the EC‐ICB than in the non‐EC‐ICB group (69.2±15.2 versus 148.6±51.2 ms; P <0.001), and RPV‐high RA time<89.0 ms was highly predictive of the existence of an EC‐ICB (sensitivity, 91.7%; specificity, 89.3%). Conclusions An EC‐ICB can be effectively detected by intra‐atrial sequencing during RPV pacing, and an RPV‐high RA time of <89.0 ms was highly predictive.