Abstract 2476: Loss of Pace-Capture on the Ablation Line: A New Marker for Complete RF Lesions to Achieve Pulmonary Vein Isolation
Introduction This pilot study investigated whether loss of pace-capture (PC) directly along the ablation line might serve as an endpoint for achieving electrical PV isolation (PVI).
Methods Using a three-dimensional anatomic mapping system and irrigated-tip radiofrequency (RF) ablation catheter, lesions were placed in the PV antra to encircle ipsilateral vein pairs until PC no longer occurred along the line (unipolar or bipolar pacing at 10mA/2ms). During ablation, a circular mapping catheter was placed in an ipsilateral PV, but the electrograms (Eg) were not revealed until loss-of-PC. The procedural endpoint was PVI (entrance and exit block).
Results Thirty patients (57±12 years; 15 male [50%]) undergoing PVI in 2 centers (3 primary operators) were included (LA diameter 40±4 mm, left ventricular ejection fraction 60±7 %). All patients reached the endpoints of complete PVI and loss of PC. When the PV Eg were revealed (that is, after the stage of ablation of PC sites), PVI was present in 57/60 (95%) vein pairs. In the remaining 3/60 (5%) PV pairs, conduction persisted after targeting PC sites; further RF applications were required to achieve PVI. The procedure duration was 237±46 minutes with a fluoroscopy time of 23±9 minutes. Retrospective analysis of the blinded PV Eg revealed that even after PVI was achieved, additional sites of PC were present on the ablation line in 39/60 (65)% of the PV pairs; 10±4 additional RF lesions were necessary to fully achieve loss of PC. The Eg amplitude was lower at sites with loss of PC (0.25±0.15 mV vs. 0.42±0.32 mV [p<0.001]), but there was substantial overlap with PC sites, suggesting that Eg amplitude lacks specificity for identifying PC sites.
Conclusion Rendering the ablation line unexcitable to pacing achieves entrance block in 95% of vein pairs without circular mapping catheter guidance. Interestingly, PVI was achieved before complete absence of PC. Further study is warranted to determine if late PV conduction recurrence might be reduced using the combined procedural endpoint of PVI and loss of PC.