Sudden death due to isolated acute infarction of the His bundle

A 29 year old black man considered to be in good health died suddenly and unexpectedly. At postmortem examination there were no significant gross abnormalities, all drug screens were normal and sicklemia was not present. Special studies of the cardiac conduction system demonstrated isolated acute infarction of the His bundle, with no similar evidence of myocardial infarction anywhere else in the heart. The atrioventricular (AV) node artery was moderately narrowed, but its branch supplying the His bundle was occluded greater than 95% by focal fibromuscular dysplasia. There were no other significant coronary lesions or other abnormalities in the heart.