Cardioversion and defibrillation using a catheter electrode: myocardial damage assessed at autopsy

A technique has been described for countershock in an intensive care setting using a catheter electrode in patients with recurrent ventricular tachyarrhythmias. During defibrillation or cardioversion an electrode in the superior vena cava acts as an anode and an electrode in the right ventricular apex is the cathode. This report describes the resultant changes in the hearts of four men who died with recent, large myocardial infarcts and who had received eight to 55 countershocks of 2.5-50 joules through the catheter. Mural thrombus and/or focal endothelial hemorrhage was found in three hearts at the anode site. Thrombus was seen at the cathode site in two hearts. Myocardial necrosis, secondary to the catheter, was present in only one heart which had a 2 mm rim of granulation tissue around the distal electrode. It is unlikely that this focal area of right ventricular damage would be clinically important. We conclude, therefore, that repeated countershocks delivered through the catheter system produce little myocardial damage.