Ischemia, injury and necrosis in the electrocardiogram: basic concepts

Abstract

The electrocardiogram is an essential tool in the care of patients with chest pain and suspected ischemic heart disease. The present review aims to address with a pleasant approach for health sciences students the most basic concepts of the electrocardiogram, as well as the classic electrocardiographic findings of ischemic heart disease. Myocardial ischemia results from an inadequate state of oxygen and nutrient perfusion to the cardiac tissue. It is identified on the electrocardiogram by alterations in the T wave. Depending on the area of the myocardium affected, there may be acuminate T waves in subendocardial ischemia or inverted T waves in subepicardial ischemia. Myocardial injury is identified on the electrocardiogram by deviations in the ST-segment; ST-segment elevation in the case of a subepicardial lesion (emblematic of ST-segment elevation acute myocardial infarction) or by negative ST-segment depression in the case of a subendocardial lesion. Finally, necrosis is identified by the presence of pathological Q waves and is usually found after a non-reperfused ST-segment elevation myocardial infarction or as a consequence of a prolonged severe ischemic insult.