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

Background: 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.

Methods: 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.

Results: 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.

Conclusions: 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.