Certified Cardiographic Technician (CCT) Practice Exam 2025 - Free CCT Practice Questions and Study Guide

Ischemia on an ECG is commonly identified by ST segment depression. This phenomenon occurs when there is insufficient blood flow to the heart muscle, which can happen during exertion or stress. The decreased blood supply leads to a decrease in cellular metabolism and alters the electrical activity of the heart, resulting in characteristic changes in the ST segment.

ST segment depression typically indicates that the myocardial cells are not receiving enough oxygen, which may result in subendocardial ischemia where the innermost layer of the heart muscle is affected. This can often manifest as a downsloping or horizontal shift of the ST segment below the baseline, especially during exercise testing or in the presence of heightened demand on the heart.

Understanding this mechanism is crucial for identifying ischemic episodes, guiding further investigation or interventions to prevent more severe cardiac events such as myocardial infarction. Other ECG changes, such as ST segment elevation or changes in the T wave morphology, indicate different pathophysiological states and are not characteristic of ischemia in the same way as ST segment depression.