Pathologic findings following sudden death in an infant with hypertrophic cardiomyopathy and supraventricular tachycardia.

The cardiac conduction system from infants suddenly dying with hypertrophic cardiomyopathy has not been described. We studied by serial section examination the conduction system from a 13-month old infant also known to have had supraventricular tachycardia. At autopsy, there was cardiomegaly with asymmetric septal hypertrophy. Microscopic examination revealed myofiber disarray around an abnormally formed central fibrous body, numerous nodoventricular fibers to both sides of the ventricular septum, and fibrosis of the left bundle branch. We postulate that supraventricular tachycardia utilized a concealed pathway or the malformed AV junction. Death may have resulted from deranged hemodynamics secondary to supraventricular tachycardia.