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.