Definitions and grouping
After the procedures, the presence of an EC was verified based on a centrifugal conduction pattern near the right-sided PV, which was differed from the early activation site of Bachman bundle. We confirmed the electrical conduction pattern using Ripple mapping and Coherent mapping. The EC site was determined on the basis of the earliest activation points.
The patients were divided into two groups according to the presence or absence of an EC (EC-positive and EC-negative groups). Patients in the EC-positive group were further subdivided into three groups according to the relative locations of the EC site and the originally designed isolation line: on-the-line group (EC site on the isolation line); inside-line group (EC on the PV side of the isolation line); and outside-line group (EC on the LA side of the isolation line) (Figure 1).