Ischaemia

Ischaemia, or ischemia, is a condition in which blood flow to a tissue or organ is reduced below its metabolic needs, leading to an insufficient supply of oxygen and nutrients. The resulting metabolic stress can cause reversible dysfunction if perfusion is restored promptly, but prolonged ischaemia may lead to irreversible cell injury and tissue necrosis. Ischaemia can occur from impaired arterial inflow, venous outflow obstruction, or systemic underperfusion due to low blood pressure or shock, and it can be acute or chronic.

Causes and mechanisms include atherosclerotic narrowing, thrombosis, embolism, vasospasm, external compression, and decreased cardiac output. At the cellular level, reduced oxygen and glucose disrupt aerobic metabolism, deplete ATP, impair ion pumps, cause intracellular swelling and acidosis, and, with continued lack of perfusion, lead to cell death. Reperfusion after ischaemia can also cause injury through inflammatory responses and oxidative stress.

Ischaemia affects various organs differently. Myocardial ischaemia may present as chest pain and can progress to angina or myocardial infarction. Cerebral ischaemia can result in stroke or transient neurological deficits. Mesenteric ischaemia involves the intestines and can cause severe abdominal pain. Peripheral ischaemia can lead to claudication or critical limb ischaemia with potential tissue loss.

Diagnosis relies on clinical presentation supported by imaging and laboratory tests. Cardiac ischaemia is assessed with ECG and biomarkers; cerebral ischaemia uses neuroimaging; vascular ischaemia employs Doppler ultrasound and angiography. Treatment focuses on restoring perfusion and addressing the underlying cause, with supportive care and risk-factor management to prevent recurrence.

Prognosis depends on the tissue involved and the duration of ischaemia. Prevention centers on managing cardiovascular risk factors, rapid recognition, and timely revascularization when occlusion occurs.