ECG changes of myocardial ischemia

ECG changes of myocardial ischemia

ECG changes of myocardial ischemia: Subendocardial ischemia produces ST segment depression while transmural or subepicardial ischemia produces ST segment elevation. It may be noted that subendocardium is more vulnerable to ischemia as collateral flow is more to the subepicardial region and extravascular compressive forces are more in the subendocardium [1].

It should be possible to record an ECG within 10 minutes of reporting to the emergency department in a case of suspected acute myocardial infarction.

Initial peaking and broadening of T wave is one of the earliest change in acute ST elevation myocardial infarction. But this alone is not specific enough to recommend thrombolytic therapy. Nothing is lost by waiting a few minutes to look for ST elevation to be more specific in diagnosing acute myocardial infarction. Specifically because there is a small but definite risk of cerebral hemorrhage for thrombolytic therapy. But waiting too much is also not good. If it is delayed till the appearance of deep Q waves and T waves get inverted, the role of thrombolysis becomes limited. If primary angioplasty is available, waiting for ECG to become typical may not be worth it as the risk of bleeding is not very high with diagnostic coronary angiography. If the clinical presentation is typical and ECG suggests developing ST elevation myocardial infarction, no time should be lost.

Reference

1. S C Krishnan, K Shivkumar, H Garan, J N Ruskin. Increased vulnerability of the subendocardium to ischaemic injury: an electrophysiological explanation. Lancet. 1995 Dec 16;346(8990):1612-4.