Myocardial infarction
3 cardinal signs:
Elevation of ST segment
Inversion of T wave
Deep & wide Q wave
With reciprocal changes in the leads facing the opposite wall:
Depression of ST segment
Tall, upright T waves
Changes do not appear at the same time. It happens in this order:
Elevation of ST segment stays for 2-3d and gradually goes back to base level in 1-2w
T wave becomes inverted after 2 days, and remains like that for 3w, and gradually becomes flat and then upright over 2-3m
Q wave = muscle death, appears after 1 week, and gradually deepens and remains permanent. Size proportional to size of infarct.
Timeline:
1°d: ST segment elevation + tall T wave
2-3°d: ST segment still elevated + T wave slowly becomes inverted
7°d: ST segment starts returning to base level + T wave inverted + Q wave starts appearing, it deepens. (If ST segment stays elevated >6m, think of development ventricular aneurism)
3°w: Q wave fully developed + T wave starts becoming flat
End of 3m: only Q wave stays the same, ST segm and T wave return to normal. If the size of the infarct was small, Q wave goes back to normal.
Coronary Arteries, branches & supply:
Localization of infarct:
















