A STEMI (ST-elevation myocardial infarction) is the most serious form of heart attack, caused by complete and sudden blockage of a coronary artery leading to rapid and progressive death of the heart muscle supplied by that artery. The term refers to the characteristic ECG finding: persistent elevation of the ST segment in leads corresponding to the affected coronary territory, indicating full-thickness ventricular ischaemia.
STEMI most commonly results from rupture of an atherosclerotic plaque and the subsequent formation of a blood clot that suddenly occludes the artery. Without treatment, the affected myocardium begins to die within minutes and infarct size grows with every minute of delay. STEMI is also a common cause of sudden cardiac arrest due to ventricular fibrillation triggered by acute myocardial ischaemia.
The treatment of STEMI is emergency reperfusion: restoring blood flow as rapidly as possible. Primary PCI (balloon angioplasty and stenting) is the preferred treatment in the UK when a PCI centre can be reached within 120 minutes of first medical contact. Thrombolysis (clot-dissolving medication) is used as an alternative when PCI cannot be performed within this timeframe. The key metric is ‘door-to-balloon time’; ‘time is muscle’ reflects that every minute of delay results in additional cardiomyocyte death.
For cardiac arrest survivors found to have had a STEMI as the cause, emergency coronary angiography and PCI are typically performed immediately after resuscitation, regardless of whether the patient has regained consciousness. See also: NSTEMI.
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