Ischaemia
An inadequate blood supply to a tissue or organ, depriving it of oxygen.
What it means
Ischaemia is a restriction of blood supply to tissue, insufficient to meet its metabolic demand. From the Greek ischein, to restrain, and haima, blood.
The usual mechanism is narrowing or obstruction of an artery, most often by atherosclerosis, thrombosis or embolism. It may also arise from reduced perfusion pressure, as in shock.
Ischaemia is potentially reversible. If blood flow is restored the tissue recovers; if the deficit is severe or prolonged, cell death follows and the process becomes infarction, which is not.
Ischaemia typically causes pain that appears on exertion and resolves with rest — angina in the heart, claudication in the legs — because demand rises above the restricted supply.
In practice
Appears in cardiology, vascular and neurology letters, and in reports of exercise testing and imaging. "Ischaemic changes" on an electrocardiogram describes patterns suggesting inadequate coronary supply.
"Ischaemic heart disease" and "critical limb ischaemia" are established diagnostic terms.
Why it matters
The significance is that ischaemia is a warning of jeopardised tissue and an opportunity to intervene before infarction occurs.
New, worsening or rest-onset ischaemic pain represents an unstable pattern and requires emergency assessment. Chest pain at rest may indicate an impending myocardial infarction; a suddenly cold, pale, painful limb indicates acute limb ischaemia and is a surgical emergency.
Clinically reviewed by Dr Mohammad Zubair Khan, GMC 7563469
Last reviewed
August 30, 2026