ST-elevation MI (STEMI): Patients presenting with cardiac-sounding chest pain with persistent ST segment elevation (or new LBBB) on their ECG. ST elevation should be > 1 mm in limb leads and 2 mm in chest leads. Subsequent hs-TnI will frequently be > 100 ng/L (and CK usually > 400). Non-ST elevation MI (NSTEMI): Patients presenting with cardiac-sounding chest pain. ECG may show ST segment depression, T wave inversion or may be normal. Subsequent hs-TnI will frequently be > 100 ng/L. Previously established ECG changes such as old MI, LV hypertrophy or atrial fibrillation may be present. The hallmark of acute coronary syndrome is labile ECG changes. Unstable angina: Patients presenting with cardiac-sounding chest pain. ECG may show ST segment depression, T wave inversion or may be normal. Subsequent hs-TnI will be within the normal reference range.