The protocol of SVC isolation
Firstly, electroanatomical SVC maps were created using a Pentaray catheter during sinus rhythm. The local SVC potentials were recorded from the ablation catheter. To determine the site of the phrenic nerve, high output pacing (10V) was performed. The sites where phrenic nerve stimulation was observed, were marked as a phrenic nerve position on the SVC map. The AI was blinded to the operator, and the circumferential SVC isolation was performed 1 cm above the earliest activation sites during sinus rhythm. The RF energy was set at 20W-25W and was decreased to 15W-20W in the phrenic nerve area or area close to the sinus node. Ablation was discontinued immediately when a decrease in the diaphragmatic movement was observed on the fluoroscopic image. The endpoint of the SVCI was the disappearance of all SVC potentials, and bidirectional block was confirmed by pacing from the ablation catheter in the SVC. We also confirmed dormant conduction after an intravenous injection of isoproterenol and adenosine triphosphate.