Increased thrombin generation and impaired fibrinolysis during Escherichia coli O157:H7-associated hemolytic uremic syndrome (HUS) plausibly diminish myocardial blood flow, but the frequency of cardiac ischemia during HUS is unknown. We identified a 9-year-old boy with HUS in whom myocardial diastolic dysfunction was demonstrated by echocardiography, who also had elevated serum troponin-I and creatine kinase MB mass. However, eight additional patients with HUS did not have elevated markers of cardiac injury. When present, elevated troponin-I should be considered to represent myocardial injury, and not attributed simply to renal insufficiency. It is possible that myocardial ischemia and secondary arrhythmias account for some sudden deaths that occur during acute HUS.