Outcome measures
First, we evaluated the success rate of SVCI, comparing the CIED group with the non-CIED group. Other procedural characteristics such as procedural time, time needed to achieve SVCI, fluoroscopic time, the reconnection rate of SVCI in the second session, and the incidence of phrenic nerve paralysis were also compared between the groups. Second, lead parameters were compared before and after SVCI in the CIED group. Lead parameters obtained within 1 year before and after AF ablation were evaluated. Lead parameters after AF ablation were defined as sensing, pacing threshold, and pacing impedance at the outpatient clinic after discharge, to exclude transient abnormality of CIEDs in the acute phase. In patients who had undergone 2 SVCI sessions, we compared lead parameters before the first session and after the second session. Finally, we studied the lead failure rate after SVCI and the details of the lead failure. Lead failure was defined as a sudden impedance increase (>50% compared with chronic values) in pacing and high voltage impedance, lead dislocation, and electrical noise artifact from rapid, non-physiological make-break potentials recorded on the sensing channel. Oversensing of non-cardiac potentials, not considered as lead integrity failure, was not defined as lead failure in this study.14