A 46-year-old man with polycystic kidney disease was referred to our institution for ventricular septal defect complicating myocardial infarction. Cardiac catheterization disclosed normal coronary arteries and absence of myocardial bridging. None of the more frequent causes of thrombosis were present, and histopathology proved negative for acute myocarditis. The surgical procedure was successful and the 11-month follow-up uneventful.