Myocarditis as cause of impaired myocardial function after aortocoronary bypass.

A 44-year-old man suffered congestive heart failure and worsened ejection fraction 8 months following repeat aortocoronary bypass surgery. Recatheterization showed patent grafts. A constellation of symptoms, together with highly suggestive (but not in themselves diagnostic) endomyocardial biopsy results, led us to an unexpected diagnosis of active lymphocytic myocarditis. After treatment with prednisone and azathioprine, the patient improved clinically and his left ventricular ejection fraction increased from 18% to 24%.