Pathological Study of an Explanted Heart Due to Intractable Ventricular Fibrillation

Pathology of the Explanted Heart. A 35-year-old male had multiple admissions for polymorphic sustained ventricular tachycardia (VT) associated with cardiac arrest, uncontrolled by beta blockers and antiarrhythmic drugs including amiodarone. Electrophysiologic testing was negative and there was no evidence for conduction system abnormalities. Retrograde atrioventricular (AV) conduction was present. The left ventricular ejection fraction was 68% with normal left ventricular size. Multiple myocardial biopsies were reported normal except for one suggesting myocarditis. Atrial pacing (rates > 90) and high-dose isoproterenol (> 300 grams/min) helped suppress VT. A DDD pacer was implanted but VT still recurred. An internal cardioverter defibrillator was implanted with attempted selective ventricular sympathetic denervation. Six months later, he had a recurrent cardiac arrest that did not respond to internal defibrillator shocks. Multiple external shocks returned him to sinus rhythm. He underwent heart transplantation despite normal left ventricular function and no heart failure. Pathology of the explanted heart without the atria revealed a weight of 442 grams. Both ventricles were hypertrophied and enlarged. Serial section examination of the conduction system revealed chronic myocarditis of the approaches to the AV node, the AV node, and beginning of the right bundle branch. The AV node was in part within the central fibrous body, and the AV bundle showed fibro-fatty change and was left sided. There was marked fibrosis of the left bundle branch, chronic epicarditis, arteriolosclerosis of the summit of the ventricular septum, and fibrosis on both sides of the heart. Conclusions: (1) The above findings suggest that myocarditis of a smoldering type and/or fibrosis of the ventricular septum probably caused the intractable VT and fibrillation; and (2) A new indication for cardiac transplantation may include intractable VT associated with cardiac arrest.