An occluded artery is a blood vessel in which blood flow has been partially or completely blocked. The term ‘occlusion’ means blockage or obstruction. In cardiovascular medicine, arterial occlusion most commonly refers to blockage of the coronary arteries (causing heart attack or myocardial ischaemia) or blockage of arteries supplying the brain (causing stroke), though occlusion can occur in any artery.
Arterial occlusions arise through several mechanisms. Atherothrombosis is the most common cause of acute coronary occlusion: an atherosclerotic plaque ruptures, triggering the clotting system to form a thrombus (blood clot) that suddenly blocks the artery. Embolism occurs when material (usually a blood clot, but also air, fat, or calcified fragments) travels from elsewhere in the body and lodges in a smaller artery. Vasospasm (sudden severe narrowing of the arterial wall) can also produce transient or prolonged occlusion.
Complete occlusion of a major coronary artery produces a STEMI (ST-elevation myocardial infarction), where the supplied area of heart muscle begins to die rapidly. Partial or transient occlusion produces NSTEMI or unstable angina. Chronic total occlusion (CTO) describes a coronary artery that has been completely blocked for three months or more, often with collateral vessels having developed to provide partial compensation.
Restoring blood flow through an occluded coronary artery is the primary goal of emergency treatment. Primary PCI achieves this by threading a balloon catheter to the occlusion site and reopening the vessel, followed by stent placement. Speed is critical: every minute of continued occlusion results in additional heart muscle death.
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