[Laser ablation in the treatment of ventricular tachycardia: problems in the clinical case].

I. Experimental Studies We examined if laser ablation could make the same characteristic lesion as cryolesion to canine myocardium. Nine mongrel dogs were used in this experiment. Right lateral thoracotomy was performed and Nd:YAG laser was delivered onto the epicardial surface of both ventricles. Laser power of between 10 and 50 W was used with the various duration of 3 and 20 s, keeping the lasing distance 5 mm above the cardiac surface. Histologically, the lesion showed a well-demarcated area consisted of coagulation necrosis and contraction band necrosis in the acute phase, which changed to a fibrous scar in the chronic phase. There was a good correlation (r = 0.79; n = 52, p less than 0.01) between the lasing energy and the depth of the denaturation zone. II. A Case Report A 45-year-old male with ventricular tachycardia (VT) after aortic valve replacement was operated upon with Nd; YAG laser delivery. An antero-lateral thoracotomy through 4th and 6th inter-costal space was performed. The intraoperative mapping showed the three origins of VTs to be near the apex of left ventricle. With cardiopulmonary bypass, Nd; YAG laser was delivered onto the endocardial surface adjacent to arrhythmogenic foci. The lasing power was 10-30 W with the duration of 5.0-9.9 s. One hundred twenty seven trials were done with the total lasing energy to be 12490 J. Subsequently cryoablation was added on this area. Though VT remained in acute phase, 2 weeks later, all of tachyarrhythmia was abolished spontaneously.