Contact Index–Guided Pulsed Field Ablation: A Two‐Phase Validation of the Impedance Change Threshold to Prevent Acute Pulmonary Vein Gaps

ABSTRACT Background Pulsed field ablation (PFA) for atrial fibrillation (AF) requires adequate catheter–tissue contact. The Contact Index visualizes impedance change for the pentaspline catheter, but a validated contact threshold is unknown. Objective The objective of this study is to define an impedance‐change cutoff that predicts sufficient contact to prevent acute pulmonary vein gaps (PVG) during pulmonary vein isolation (PVI), and to validate Contact–Index‐guided PVI. Methods A prospective, single‐center, two‐phase study was performed. Phase 1 ( n = 10) measured impedance change (%) at eight antral segments per vein immediately before PFA in basket and flower configurations; the larger per‐segment value was analyzed. Post‐PVI high‐density voltage mapping (PVG ≥ 0.5 mV) was the reference; a receiver operating characteristic analysis identified the cutoff. Phase 2 ( n = 26) delivered energy only when all target splines met/exceeded the cutoff value obtained from Phase 1. Results In Phase 1, PVG occurred in 13/320 segments across 2/10 patients (4/40 veins). Impedance change was lower at PVG‐positive than PVG‐negative segments (median 2 [0–6.5]% vs. 24 [17–32]%, p < 0.001). The cutoff value obtained from Phase 1 was ≥ 10% (area under the curve 0.99; sensitivity 100%; specificity 92.1%). In Phase 2, enforcing ≥ 10% yielded no patient‐level PVG (0/26 vs. 2/10; p = 0.07) and fewer gaps per vein (0/104 vs. 4/40; p = 0.005) and per segment (0/832 vs. 13/320; p < 0.001) compared with Phase 1. Procedure time, PVI time, fluoroscopy time, and total applications were similar between phases. Conclusions An impedance‐change threshold of ≥ 10% on the Contact Index reliably indicates adequate contact with the pentaspline catheter and, when enforced, reduces acute PVG without prolonging procedures.