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

Abstract

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. K E Y W O R D S ablation index, atrial fibrillation, contact force, pulmonary veins isolation, radiofrequency catheter ablation SUPPORTING INFORMATION Additional supporting information may be found online in the Supporting Information section at the end of the article. How to cite this article: Kawaji T, Hojo S, Kushiyama A, et al. Limitations of lesion quality estimated by ablation index: An in vitro study. J Cardiovasc Electrophysiol. 2019;30:926-933.

Pulmonary vein isolation using a higher power shorter duration CLOSE protocol with a surround flow ablation catheter

“…Bourier et al found larger but shallower lesions with similar lesion volumes, using HPSD in an in vitro model. In another in vitro study, Kawaji et al found an influence of power settings and contact angle on the obtained AI values. Interestingly, they found smaller lesion volumes with HPSD.…”

The force stability of tissue contact and lesion size index during radiofrequency ablation: An ex‐vivo study

“…Only recently, Kawaji et al investigated the lesion quality in relation to different contact angles to the myocardium 18 . Using a Thermocool SmartTouch (Biosense‐Webster) catheter, the group found the ablation index, incorporating contact angle, power delivery, and CF settings to only poorly correlate with lesion size at higher contact angles.…”

“…tion to different contact angles to the myocardium. 18 Moreover, measures of CF can be used to predict gap formation after pulmonary vein isolation directly affecting recurrence rates of atrial fibrillation. 5,15 The maximal difference of lesion size between the surface aspect and the within-tissue aspect of the lesion has previously been shown to be 1-2 mm.…”

How much is enough? An appraisal of high‐power short‐duration radiofrequency ablation for pulmonary vein isolation

“…Values of AI may be the same between HPSD and conventional RF lesions, however, this is with respect only to the lesion volumes, as AI does not differentiate the lesion geometry (width and depth) . AI can vary depending on the catheter angles and the power delivered . The CLOSE protocol, adopted in the study by Berte et al, relies on AI as a guide for ablation (AI ≥ 400 at posterior segments and ≥ 550 at anterior segments, maximum inter‐lesion distance < 6 mm, and ablation line contiguity index >100%) .…”

“…The authors themselves have exercised caution while using the routine values of AI in HPSD settings, especially while delivering lesions ≤ 4 seconds. It is also true that HPSD strategy may result in a lesser lesion depth at a set AI …”