Ischaemic

Ischaemic describes a state in which blood flow to a tissue, organ, or region is reduced or blocked, resulting in insufficient oxygen and nutrients for normal metabolism. It can be focal or global and may be acute or chronic. If perfusion is not restored, the affected tissue can sustain injury and, with ongoing deprivation, may progress to infarction.

Common examples include myocardial ischaemia (reduced blood flow to the heart muscle), cerebral ischaemia (reduced brain perfusion), and ischaemia affecting the abdomen, kidneys, or limbs. Myocardial ischaemia can present as chest pain or dyspnoea; cerebral ischaemia can cause stroke symptoms or transient ischaemic attacks.

Causes include atherosclerotic narrowing of arteries, thrombus formation, embolic occlusion, vasospasm, systemic hypotension, and microvascular dysfunction. Chronic ischaemia often results from progressive arterial disease, whereas acute ischaemia typically arises from sudden occlusion by a clot or embolus.

Pathophysiology involves an imbalance between oxygen supply and demand. Reduced inflow prompts anaerobic metabolism, lactate accumulation, and acidosis, leading to cellular injury. If blood flow is not promptly restored, injury may become irreversible. Reperfusion after occlusion can also cause additional injury.

Diagnosis relies on clinical presentation supplemented by targeted testing. Myocardial ischaemia is assessed with ECG changes and cardiac enzymes; cerebral ischaemia is evaluated with imaging such as CT or MRI and vascular studies; peripheral ischaemia uses Doppler ultrasound and imaging to identify occlusions or stenoses.

Management aims to restore perfusion and treat underlying causes. In the heart, antiplatelet or anticoagulant therapy and revascularisation; in the brain, thrombolysis or mechanical thrombectomy when appropriate; in limbs or viscera, surgical or endovascular revascularisation. Prevention focuses on risk-factor modification and prompt recognition to reduce the risk of infarction and disability.