THORACOSCOPIC RADIOFREQUENCY ABLATION OF THE MYOCARDIUM

Radiofrequency (RF) catheter ablation has been used for the treatment of Ventricular tachycardia (VT), however, in some patients VT might re sult from subepicardial macroreentry that could be successfully termin ated by epicardial approach. This study examined the feasibility of th oracoscopic RF ablation of myocardium from epicardium using a custom m ade electrode. In five mongrel dogs, the thoracoscope was introduced t hrough the 7th intercostal space. A 500-kHz continuous wave RF energy was connected to a custom made multiple electrode probe. Under thoraco scopic guidance, the heart was exposed and the RF probe was introduced . RF ablation was performed on the nonvascular ventricular wall of the beating heart. The left ventricular free wall and right ventricular o utflow tract were satisfactorily visualized and ablated. The total dos e of RF energy ranged from 50 to 500 J, and the estimated volume of ab lated lesions ranged from 42.0-799 mm(3). There were significant corre lations between the RF discharge output and the irradiated lesion volu me (P < 0.01), and the depth of the lesions (P < 0.01). Grossly, after RF ablation the ventricular myocardium demonstrated a circular, well- demarcated area of thermal injury. Volume and depth of the lesion depe nded upon the total dose of delivered RF energy. Thoracoscopic RF abla tion appears to be a minimally invasive and useful method for creating irradiated myocardial lesions from epicardial surface. This method co uld be technically feasible for the treatment of Vts for which endocar dial RF ablation is ineffective.