Limitations of lesion quality estimated by ablation index: An in vitro study

LIMITATIONS OF THE ABLATION INDEX BACKGROUND: Ablation index (AI) is a novel marker of lesion quality from radiofrequency (RF) catheter ablation. However, AI reliability has not been fully validated by experimental data. The aim of the present study is to validate AI reliability for estimating lesion size using different settings for RF parameters: contact angle, power delivery, and contact force (CF). METHODS AND RESULTS: We evaluated the lesion size in porcine hearts (N = 108) after RF application at three different contact angles to the myocardium: perpendicular (90°), oblique (45°), and parallel (0°). At each angle, RF power at 25, 30, and 35 W was applied at target CF values of 5, 15, and 30 g as measured by the CF sensor to reach target AIs of 300, 400, 500, and 600. AI value was significantly correlated with lesion depth, width, and volume (R = 0.84, 0.82, and 0.87, respectively, all P < 0.001). Lesion depth decreased with smaller contact angles (45° and 0°). Furthermore, high-power RF energy (35 W) resulted in a significantly smaller lesion volume compared with standard-power energy (30 W). There were no significant differences in lesion size among CF settings. CONCLUSIONS: AI was strongly correlated with lesion depth, width, and volume, but only within a small range of contact angles and RF power delivery settings.