 A. Patients with a known history of coronary artery bypass surgery. B. Current or previous ST elevation myocardial infarction MI, prior MI confirmed by persistent pathologic Q waves on ECG, clinical reports of CPK-MB or Troponin three times the upper limit of normal or a fixed perfusion defect on nuclear imaging C. Current evidence of acute myocardial ischemia, unstable angina, or cardiovascular instability including troponin than the limit of detection 0.06 ngml, new ST depression 1 mm, hypotension with a systolic pressure 90 mm Hg. 