What is the typical progression of a myocardial infarction as seen on an ECG?

The typical progression of a myocardial infarction as seen on an ECG begins with the appearance of tall, peaked T waves, followed by ST elevation, and eventually leads to Q wave development.

In the early stages of a myocardial infarction, the myocardial cells become ischemic, which can manifest as tall, peaked T waves on the ECG, indicating localized hyperkalemia and early injury to the myocardial tissue. As the ischemia progresses, the ST segment starts to elevate, signifying ongoing injury and potential tissue death. This ST elevation is a critical marker that leads to the diagnosis of ST-elevation myocardial infarction (STEMI). Over time, as the myocardial cells suffer more significant damage and necrosis, Q waves will develop on the ECG. The presence of Q waves indicates that there has been irreversible damage to the heart muscle, and this typically occurs hours to days following the onset of the myocardial infarction.

This sequence illustrates how changes in the ECG correspond to the underlying pathophysiological events occurring in the heart muscle during a myocardial infarction, reflecting areas of ischemia and injury that evolve as the condition progresses.