Unstable angina (UA) and non-ST-elevation MI (NSTEMI) are acute coronary syndromes with similar mechanisms, clinical presentations, and treatment strategies.
UA includes (1) new onset of severe angina, (2) angina at rest or with minimal activity, and (3) recent increase in frequency and intensity of chronic angina. NSTEMI is diagnosed when symptoms of UA are accompanied by evidence of myocardial necrosis (e.g., elevated cardiac biomarkers). Some pts with NSTEMI present with symptoms identical to STEMI—the two are differentiated by ECG findings.
May be normal or include diaphoresis, pale cool skin, tachycardia, S4, basilar rales; if large region of ischemia, may demonstrate S3, hypotension.
May include ST depression and/or T-wave inversion; unlike STEMI, there is no Q-wave development.
Cardiac-specific troponins (specific and sensitive markers of myocardial necrosis) and CK-MB (less sensitive marker) are elevated in NSTEMI. Small troponin elevations may also occur in pts with CHF, myocarditis, or pulmonary embolism.
Treatment: Unstable Angina and Non-ST-Elevation Myocardial Infarction First step is appropriate triage based on likelihood of coronary artery disease (CAD) and acute coronary syndrome (Fig. 120-1) as well as identification of higher-risk pts (Fig. 120-2). Pts with low likelihood of active ischemia are initially monitored by serial ECGs and serum cardiac biomarkers, and for recurrent chest discomfort; if these are negative, stress testing (or CT angiography if probability of CAD is low) can be used for further therapeutic planning. Therapy of UA/NSTEMI is directed (1) against the inciting intracoronary thrombus, and (2) toward restoration of balance between myocardial oxygen supply and demand. Pts with the highest-risk scores (Fig. 120-2) benefit the most from aggressive interventions. |
For a more detailed discussion, see Cannon CP, Braunwald E: Non-ST-Segment Elevation Acute Coronary Syndrome (Non-ST-Segment Elevation Myocardial Infarction and Unstable Angina), Chap. 294, p. 1593, in HPIM-19. |
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