Open-irrigated laser catheter ablation produces flow-dependent sizes of lesions

Growth and sizes of lesions produced during catheter ablation is difficult to control. Laser lesion formation was evaluated during various flow rates and energy settings by using an open-irrigated laser catheter on a thigh-muscle dog model.

Laser radiation at 15 W or 20 W was applied in blood for 10 seconds, 20 seconds, 30 seconds, 40 seconds, and 50 seconds during an irrigation flow of 16 mL/min or 35 mL/min, in direct contact, and in a noncontact mode of laser application. Lesions were evaluated morphometrically.

There was a linear increase of lesions with the increase of the level of energy applied. Maximal depth of lesions achieved during a flow rate of 16 mL/min at 15 W/50 seconds increased significantly from 9.9 ± 0.3 mm to 12.1 ± 0.5 mm, and at 20 W/50 seconds from 11.1 ± 0.55 mm to 12.4 ± 0.26 mm, when irrigation flow was 35 mL/min (P < 0.5). However, difference of lesion increase between 15 W and 20 W was not significant (P = 0.30). Lesions were achieved also in a noncontact mode of radiation at a distance of 1-2 mm, but not at 5 mm away. Radiation at 20 W > 40 seconds and a flow rate of 35 mL/min may cause steam pop with intramural cavitation.

By using an open-irrigated laser catheter augmentation of catheter flow increases lesion sizes. Lesions can be achieved also in a noncontact mode of radiation. In order to avoid unwanted effects the level of energy applied must be limited.