4. Approximately 2/3 of patients who have postoperative myocardial injury are asymptomatic and have no ECG changes. Diagnosis of MI requires biomarker elevation (Troponin > 0.3ng/ml) plus clinical or ECG or imaging evidence of myocardial injury. Of the latter 3 criteria, 2 are often absent. In selected patients, this study will use trans-thoracic echocardiography, CT coronary angiography, and cardiac MRI to improve diagnostic yield and define those diagnostic modalities that are most useful in the postoperative patient.