Experimental production of complete heart block by electrocoagulation in the closed chest dog

Methods for producing complete heart block in experimental animals have usually required thoracotomy to gain access to the intracardiac conduction system. A closed chest technique has been developed for producing discrete permanent lesions in the atrioventricular node or His bundle of anesthetized dogs. An insulated transseptal needle is passed through a venous catheter to the right atrium. The exposed tip is pressed into the His bundle and a 30 to 40 joule pulse from a DC defibrillator is transmitted through the needle. This produces a 1 to 3 mm diameter coagulative lesion which permanently destroys the tissue at this point. The process can be repeated until complete heart block is achieved. Our procedure has been successful in 45 of 46 attempts to prepare dogs for acute experiments and, using implanted pacemakers, for chronic studies. We conclude that this closed chest method is a safe and reliable alternative for production of complete heart block requiring thoracotomy, thereby providing an important new means for both acute and chronic experimental studies requiring complete heart block for the improved elucidation of mechanisms and management of cardiovascular diseases.