Influence of catheter orientation on lesion formation in bovine myocardium by using an open-irrigated laser ablation catheter

Lesion sizes and quality are crucial for successful catheter ablation procedures. We sought to test the influence of catheter orientation towards the endocardial surface on lesion formation in bovine myocardium by using an open-irrigated laser ablation catheter. Continuous wave 1064-nm laser catheter applications at 15 W (4.5 W/mm²)/30 s, (135 J/mm²), irrigation flow 30 mL/min, were aimed at the left ventricular endocardial surface of bovine myocardium. The catheter was kept in vertical, in slanting (67.5°, 45°, 22.5°), and in flat positions; in flat position, also 60 s of radiation times were applied (n = 10, each). Lesions were evaluated morphometrically. Maximum depth of lesion was achieved with the catheter in a vertical orientation. Catheter inclination of <22.5 showed a highly significant decrease of lesion depth from 5.6 ± 1.1 to 3.7 ± 0.5 mm (p = 0.0001). In a flat catheter position, laser radiation of 30 s achieved the smallest lesions. However, after 60 s of radiation, the flat lesions were similar in depth (p = 087) and were larger in width (p = 0.0004) and in volumes (p = 0.0025) as compared to the lesions achieved with the catheter in vertical position after 30 s of radiation. Steam-pop with intramural cavitation or tissue vaporization with crater formation did not occur. Longer radiation times can achieve larger lesions regardless of catheter orientation. Catheter orientation is not a major determinant for laser ablation lesion size and quality, and a steerable support may not be needed when using the open-irrigated electrode-laser mapping and ablation (ELMA) catheter RytmoLas.