[Cryosurgery in ventricular tachycardia. Value of myocardial hypothermia in the extension of thr depth of cryogenic lesions].

A desirable goal in surgery for ventricular tachycardia seems to be the development of a direct technique avoiding ventriculotomy, which has well-known harmful effects on the function of the left ventricle. This study is aimed at creating deep cryolesions, reaching to the subendocardial layers, on a closed ventricle. Forty-five cryolesions were performed with extracorporeal circulation in 15 piglets, applying a nitrogen protoxide tube (8 mm, -80 degrees C) on the left ventricle for two minutes. In each animal, 3 cryolesions were created at three different myocardial temperatures: 37 degrees C, 28 degrees C and 10 degrees C. The lesions created at a myocardial temperature of 10 degrees C were significantly (p < 0.01) larger and deeper than those performed at 37 and 28 degrees C. Two cryolesions made at 10 degrees C appeared to extend through the wall. The diameter of the lesions was not as greatly influenced by myocardial temperature. Myocardial temperature very significantly increases the depth of cryolesions, thus allowing them to extend to the subendocardial myocardial layers. Thus the destruction of subendocardial ventricular arrhythmogenic targets by the epicardial application of low temperatures, while preserving the function of the left ventricle as much as possible, may be considered.