Laser energy source in surgical atrial fibrillation ablation: Preclinical experience

Purpose. The purpose of this study was to evaluate diffusing tip laser energy in surgical atrial fibrillation ablation using a canine model. This is the first report to describe the pathological and histological findings using a laser energy source. Description. The surgical atrial fibrillation ablation procedure was performed through a left atriotomy; the pulmonary veins were encircled in 16 dogs using a diode laser (980 nm) with a diffusing tip that permits linear ablation perpendicular to the fiber direction. Lesion durations were 45 seconds with a power density of 3.8 or 4.5 W/cm. Six animals were allowed to survive 4 hours after the procedure, with the remainder sacrificed at 1 week (n = 1), 4 weeks (n = 3), and 6 weeks (n = 6). Electrophysiologic effectiveness was judged using unipolar or bipolar pacing from the pulmonary veins after attempting isolation. Hearts were harvested for histologic examination using standard trichrome staining. Evaluation. All animals tolerated the procedure. The animals required an average of 5.6 +/- 0.82 lesions to complete the procedure. All animals had confirmed isolation of the pulmonary veins as judged by unipolar or bipolar pacing, and this isolation persisted in those animals that were allowed to survive. Pathology revealed all lesions to be transmural with an average tissue thickness of 3.62 +/- 1.50 mm (range, 0.95 mm to 7.06 mm). Conclusions. Diffusing tip laser technology reproducibly makes rapid, transmural, and electrophysiologically effective atrial lesions.