Holmium-YAG and carbon dioxide laser ablation of normal and infarcted myocardium in the canine model

Surgical and transcatheter ablative treatment of ventricular tachycardias is based on endocardial mapping and removal of myocardial areas involved in sustaining the arrhythmia. Recently, argon and neodymium-YAG laser energy have been employed for the ablative treatment of ventricular tachycardia. In the present study the effects of holmium-YAG laser irradiation on normal and infarcted myocardium in the canine model were compared with those of the CO₂ laser. Myocardial infarction was created in 11 dogs by a two-stage left anterior descending coronary artery ligation. Laser irradiation of normal and infarcted myocardium was performed at about 1, 4 and 12 weeks following ligation, with energies of 5, 10, 20 and 30 J. A total of 218 irradiation induced craters were sectioned through the central axis and the evaporized, vacuole and denatured crater areas were morphometrically calculated. Total crater areas following holmium-YAG laser irradiation were significantly larger, with shallower penetration but larger lateral extension of evaporized, vacuole and denaturation areas. Perforations occurred only with CO₂ laser irradiation. Effects on normal and infarcted myocardium were similar and independent of infarct age. It is concluded that the holmium-YAG laser is probably more effective and safer than the CO₂ laser for myocardial ablation.