Understanding T Wave Changes in Myocardial Ischemia on ECG

Electrocardiogram (ECG) is a key diagnostic tool for detecting myocardial ischemia, primarily by observing changes in the ST segment and T waves. Myocardial ischemia can be classified as acute or chronic, and while these conditions differ significantly in pathology, they often share similar and sometimes indeterminate ECG features. In chronic myocardial ischemia, ECG changes tend to be non-specific, predominantly affecting ventricular repolarization, which manifests as ST-T segment alterations. These changes can also influence ventricular depolarization in some cases.

Types of T Wave Alterations

T wave changes are a critical indicator in identifying ischemic heart disease. Common forms of T wave abnormalities include flattened T waves, biphasic T waves, inverted T waves, and peaked T waves. One particularly notable pattern is the so-called "coronary T" or "arrow T," which refers to a symmetric, inverted T wave shaped like an isosceles triangle with an angle of ≤60°, resembling an arrowhead. This specific morphology is often associated with coronary artery insufficiency.

Significance of Coronary T Waves

The presence of coronary T waves on an ECG can suggest either chronic or acute coronary artery insufficiency. When these T wave changes are dynamic—meaning they evolve over time—they typically point to acute myocardial ischemia. Conversely, persistent and unchanged coronary T waves may indicate either primary chronic ischemia or secondary ischemic changes due to other underlying conditions. These alterations mainly affect the ventricular repolarization phase, leading to ST-T segment deviations.

Interpreting T Wave Changes in Clinical Practice

Among the various T wave abnormalities, coronary T waves hold particular diagnostic value in identifying myocardial ischemia. The ischemic changes often manifest as flattened, biphasic, or inverted T waves. However, it's important to note that ECG findings suggestive of myocardial ischemia are not exclusive to coronary artery disease. Similar patterns can appear in individuals with other cardiac conditions, various systemic pathologies, and even in otherwise healthy individuals. Therefore, ECG results should always be interpreted in the context of clinical symptoms, patient history, and additional diagnostic tests for a comprehensive assessment.