ECG Changes in Acute Myocardial Infarction Myocardial Ischemia Symmetrical T wave inversion or elevation and ST segment elevation or depression Myocardial Injury ST segment elevation or depression Myocardial Necrosis Abnormal Q waves

Abnormal T Wave Repolarization begins at the epicardium and progresses toward the endocardium producing a + T-wave. Abnormal T waves indicate myocardial ischemia and appear within seconds of the onset of an acute MI. These are caused by a delay or change in direction of repolarization. Abnormal T waves are associated with depression or elevation of the ST segment.

Abnormal ST Segments Abnormal ST segments are present in myocardial infarction, indicating myocardial ischemia and injury, and in noninfarction-related myocardial ischemia from any cause ST Segment Elevation ST Segment Depression

ST Segment Elevation ST elevation is an ECG sign of severe, extensive, usually transmural, myocardial ischemia and injury in the evolution of an acute Q-wave MI. ST elevation is considered > 1 mm above baseline and measure .04 second after the J point. ST elevation usually appears within minutes after the onset of infarction, initially indicating extensive myocardial ischemia and a progression to Myocardial injury within 20 to 40 minutes. Then to Myocardial Necrosis in about 2 hours and the development of abnormal Q waves.