Stages of Myocardial Infarction on ECG

Myocardial infarction (heart attack) can be identified and staged through electrocardiogram (ECG) changes. These stages reflect the progression of heart muscle damage over time and help guide diagnosis and treatment decisions.

Stage 1: Hyperacute Phase

The hyperacute phase typically occurs within the first few hours after the onset of a heart attack. During this time, the ECG shows prominent ST-segment elevation, often referred to as the "tombstone" or "flag waving" appearance. This is a critical indicator of acute injury to the heart muscle and requires immediate medical attention.

Stage 2: Acute Phase

A few hours after the hyperacute phase, the ECG transitions into the acute phase. The ST-segment elevation remains above baseline but may begin to decrease slightly. In some patients, abnormal Q waves may start to appear, indicating the beginning of myocardial necrosis. This phase can last for several days to up to one or two weeks.

Stage 3: Subacute Phase

The subacute phase usually lasts for several weeks following the heart attack. By this time, the ST segment has typically returned to the isoelectric line or may even begin to invert. T-wave inversion often becomes evident, and clear Q waves are present, indicating established tissue death in part of the heart muscle.

Stage 4: Old or Chronic Phase

Several weeks after the myocardial infarction, the ECG enters the chronic or old phase. Many patients will continue to show persistent Q waves, which are a hallmark of prior heart damage. Additionally, ST-segment depression and T-wave inversion may remain visible, reflecting long-term changes in heart muscle function and structure.