Myocardial ischaemia occurs when the blood supply to part of the heart muscle (myocardium) is insufficient to meet its oxygen demands. The most common cause is narrowing or blockage of a coronary artery due to coronary artery disease, where the build-up of atherosclerotic plaque restricts blood flow.
Ischaemia can be stable or unstable. Stable ischaemia typically occurs during exertion or emotional stress, when the heart’s demand for oxygen increases but cannot be met through narrowed arteries. This produces angina (chest pain or pressure, often also felt in the jaw, left arm, or back), which resolves with rest or nitrate medication. Unstable ischaemia occurs when a plaque ruptures and a clot partially or completely blocks the artery, causing symptoms at rest and raising the risk of heart attack and cardiac arrest.
Prolonged ischaemia without restoration of blood flow leads to irreversible death of heart muscle cells (myocardial infarction). Even after blood flow is restored, a period of reversible dysfunction called myocardial stunning can temporarily impair heart function. Chronically under-perfused muscle that is still alive but barely contracting is called hibernating myocardium, which may recover if blood supply is restored.
Myocardial ischaemia is detected by ECG changes (ST depression or elevation), blood tests (elevated troponin), echocardiography, and functional imaging such as radionuclide studies or cardiac MRI. Treatment aims to restore adequate blood flow through medication, PCI, or CABG surgery.
« Back to Glossary Index