GROSS AND MICROSCOPIC PATHOLOGICAL-CHANGES ASSOCIATED WITH NONTHORACOTOMY IMPLANTABLE DEFIBRILLATOR LEADS

Background - Although the effects of epicardial implantable cardiovert er-defibrillator (ICD) leads on underlying cardiac tissue have been re ported, the gross and microscopic changes associated with endocardial ICD leads are less well described. This study describes the gross and microscopic changes associated with endocardial ICD leads in humans. M ethods and Results - The hearts from 8 patients were examined. At the time of TCD implantation, the patients' mean age was 47 +/- 11 years, and the left ventricular ejection fraction was 0.24 +/- 0.10. Four pat ients had ischemic heart disease, and 4 had dilated cardiomyopathy, Fi ve hearts were examined after transplantation; 3, after death. The ele ctrode-myocardial interfaces were characterized by intense endocardial fibrosis and were remarkably consistent. Each lead was encased by a r ing of fibroelastic tissue, and there was fibrosis of the right ventri cular myocardium adjacent to the leads. Fibrosis involved the tricuspi d valve in 5 patients, and 1 had perforation of the valve by the lead. Microscopically, interstitial fibrosis was adjacent to each lead in t he current path of ICD shocks. Acute cell injury was present only in t he hearts that had received recent shocks. Conclusions - The ICD elect rode-myocardial interface is characterized by intense fibrosis. The fi brosis associated with endocardial ICD leads and the cumulative acute damage produced by defibrillation discharges may explain changes in th e defibrillation and pacing thresholds and the difficulty of lead extr action that can be encountered with transvenous ICD systems.