As a domain expert in cardiology, I can explain that ST depression on an electrocardiogram (ECG) is typically indicative of myocardial ischemia, which is a condition where the heart muscle does not receive enough blood flow. The primary cause of myocardial ischemia is coronary insufficiency, which occurs when the coronary arteries are narrowed or blocked, often by atherosclerosis. Other conditions that can lead to ST depression include: - Subendocardial ischemia: This refers to ischemia that affects the inner layer of the heart muscle without involving the full thickness of the myocardium. - Infarction: A more severe form of ischemia that can lead to tissue death in the heart muscle. It's important to note that while ST depression is often associated with ischemia, it can also be seen in other conditions and may not always indicate a serious cardiac problem. It requires a comprehensive evaluation by a healthcare professional to determine the underlying cause. read more >>

It is often a sign of myocardial ischemia, of which coronary insufficiency is a major cause. Other ischemic heart diseases causing ST depression include: Subendocardial ischemia or even infarction. Subendocardial means non full thickness ischemia. In contrast, ST elevation is transmural (or full thickness) ischemia.read more >>