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Non–ST-Elevation Acute Coronary Syndromes

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Key Points Î ACS has evolved as a useful operational term that refers to a spectrum of conditions compatible with acute myocardial ischemia and/or infarction which are usually due to an abrupt reduction in coronary blood flow (Figure 1). • A key branch point is ST elevation or new left bundle-branch block on the ECG, which are considerations for immediate coronary angiography to determine if there is an indication for reperfusion therapy to open a likely completely occluded coronary artery. Î The hallmark of ACS is the sudden imbalance between myocardial oxygen supply and demand, which is usually the result of coronary artery obstruction. • The imbalance may also be caused by other conditions, including excessive myocardial oxygen demand in the setting of a stable flow-limiting lesion; acute coronary insufficiency due to other causes (e.g., vasospastic [Prinzmetal] angina, coronary embolism, coronary arteritis); noncoronary causes of myocardial oxygen supply-demand mismatch (e.g., hypotension, severe anemia, hypertension, tachycardia, hypertrophic cardiomyopathy, severe aortic stenosis); nonischemic myocardial injury (e.g., myocarditis, cardiac contusion, cardiotoxic drugs); and multifactorial causes that are not mutually exclusive (e.g., stress [Takotsubo] cardiomyopathy, pulmonary embolism, severe HF, sepsis). Î The absence of persistent ST elevation is suggestive of NSTE-ACS (except in patients with true posterior MI). NSTE-ACS can be further subdivided on the basis of cardiac biomarkers of necrosis (e.g., cardiac troponin). • If cardiac biomarkers are elevated and the clinical context is appropriate, the patient is considered to have NSTEMI. Otherwise, the patient is deemed to have UA. • ST depression, transient ST elevation, and/or prominent T-wave inversions may be present but are not required for a diagnosis of NSTEMI. • Abnormalities on the ECG and elevated troponins in isolation are insufficient to make the diagnosis of ACS but must be interpreted in the appropriate clinical context. 1

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