coronary ischemia

Coronary ischemia is what happens when the heart muscle is, in effect, short of breath: it is not getting as much oxygen-rich blood as it is asking for. Like any hard-working muscle starved of fuel, it complains — and that complaint is often felt as chest pain.

Mechanistically, ischemia is a mismatch between oxygen supply and demand. Supply falls when a coronary artery is narrowed by plaque, spasms, or is blocked by a clot. Demand rises with exertion, fast heart rates, or high blood pressure, because the muscle then needs more oxygen. When demand outpaces what the narrowed vessel can deliver, the affected muscle switches to inefficient anaerobic metabolism and begins to malfunction.

Ischemia is usually reversible if blood flow is restored quickly: the muscle recovers. If it is severe and prolonged, however, cells die and the result is infarction — irreversible damage. Ischemia can produce angina, breathlessness, or ECG changes such as ST depression; it can also be entirely silent, detected only on testing.

Ischemia describes the under-perfused state itself, distinct from infarction (actual cell death). The same word is used for under-perfusion of any tissue; coronary or myocardial ischemia specifies the heart.