A non-ST-elevation myocardial infarction (NSTEMI) is one of the two main types of heart attack, distinguished from a STEMI by the absence of persistent ST-segment elevation on the electrocardiogram. Both involve death of heart muscle confirmed by a rise in blood troponin levels, but the underlying coronary artery blockage is typically incomplete in NSTEMI, allowing some residual blood flow to continue through the affected artery.
In a STEMI, a coronary artery is completely occluded, causing the full thickness of the supplied heart muscle wall to be at immediate risk. In an NSTEMI, the artery is partially blocked or has temporarily reopened. This distinction affects urgency of treatment: STEMIs require emergency reperfusion (primary PCI) within minutes to hours, whereas NSTEMIs are typically managed with invasive coronary angiography performed within 24 to 72 hours depending on risk stratification.
NSTEMIs are diagnosed by the combination of ischaemic symptoms (chest pain, breathlessness, jaw or arm pain), ECG changes (such as ST depression or T-wave changes, but not persistent elevation), and a rising and falling troponin pattern. They are common in older patients and those with multi-vessel coronary artery disease, diabetes, or renal impairment. Treatment includes antiplatelet therapy, anticoagulation, coronary angiography, and stenting of the culprit artery.
NSTEMIs can cause sudden cardiac arrest if electrical instability of the ischaemic myocardium triggers ventricular fibrillation. For cardiac arrest survivors found to have had an NSTEMI as the cause, the immediate priority is coronary angiography and revascularisation, followed by secondary prevention therapy and consideration of ICD implantation based on the post-recovery ejection fraction.
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