6 Acute Coronary Emergencies
Learn how acute coronary syndromes are recognized, distinguished, assessed, and managed from emergency presentation through post-discharge care.
The acute coronary syndrome spectrum
are urgent conditions caused by a sudden reduction in blood flow to the heart muscle. They commonly follow erosion or rupture of a coronary plaque and formation of a clot. The spectrum includes STEMI, NSTEMI, and ; these clinical categories do not guarantee how completely an artery is blocked.
Distinguishing the three conditions
STEMI: The ECG shows persistent ST elevation meeting lead-specific criteria or another acute-occlusion pattern. Troponin often rises, but may initially be normal. Assess for immediate reperfusion; do not wait for troponin when the ECG and presentation indicate STEMI.
NSTEMI: There is no persistent diagnostic ST elevation, though ST depression, T-wave inversion, or a nondiagnostic ECG may occur. Troponin has a rise or fall with at least one value above the assay’s 99th-percentile limit, in an ischemic clinical context.
: The ECG may be normal or show ischemic changes, but there is no acute troponin pattern meeting myocardial infarction criteria. It involves new, worsening, or rest angina without detected acute .
An elevated troponin by itself indicates , not necessarily a heart attack: myocardial infarction also requires evidence of myocardial ischemia. Conversely, an early normal troponin or a nondiagnostic ECG does not by itself exclude ACS.
Recognizing possible ACS
Possible ACS may cause chest pressure, tightness, heaviness, or pain. Discomfort may spread to the arm, shoulder, jaw, back, or upper abdomen. Shortness of breath, sweating, nausea, light-headedness, or unusual fatigue may occur with or without prominent chest pain. Presentations vary, so do not dismiss possible ACS because symptoms seem atypical or the first ECG is normal.
Suspected ACS is an emergency. Activate emergency medical services rather than having the person drive themselves. Rapid assessment should look for instability, including hypotension, altered mental status, acute heart failure, shock, or a dangerous arrhythmia. Consider alternative life-threatening causes of chest pain as well.
Early ECG and troponin assessment
Obtain and interpret a 12-lead ECG within 10 minutes of first medical contact. Compare it with prior tracings when available. If symptoms persist, recur, or worsen, repeat the ECG because ischemic changes can evolve. Obtain right-sided leads when right-ventricular involvement is suspected, and posterior leads when the standard ECG suggests posterior infarction.
Look beyond classic ST elevation: ST depression and T-wave inversion can indicate ischemia, and ST depression in V1–V3 may be a clue to posterior infarction. A normal or equivocal initial tracing does not rule out ACS; interpret it alongside symptoms and serial ECGs.
Measure cardiac troponin promptly, preferably with a high-sensitivity assay. If the initial result is nondiagnostic, repeat testing according to the local assay-specific pathway. Common intervals are 1–2 hours for high-sensitivity assays or 3–6 hours for conventional assays. Interpret the change over time and the assay’s reference limit; do not delay indicated STEMI reperfusion while waiting for a biomarker result.
Use the full clinical picture and a validated risk pathway to guide disposition and invasive evaluation. Consider other diagnoses when appropriate, since troponin elevation can occur in conditions other than type 1 myocardial infarction.
Initial management principles
Care is time-critical and should follow local emergency protocols and clinician judgment. Initial care generally includes cardiac monitoring, IV access, repeated vital signs, and prompt communication with specialists or the catheterization team when indicated. Treat hypoxemia, shock, heart failure, or arrhythmia.
Antiplatelet and anticoagulant therapy: Aspirin is commonly given promptly unless contraindicated. Additional antiplatelet therapy and an anticoagulant are selected according to the ACS diagnosis, planned invasive or fibrinolytic strategy, bleeding risk, and other patient factors.
Oxygen: Give oxygen for hypoxemia or respiratory distress rather than routinely to every patient with ACS.
Nitrates: These may relieve ischemic discomfort when appropriate. Avoid them or use them cautiously with hypotension, suspected right-ventricular infarction, or recent use of certain erectile-dysfunction medicines. Symptom relief does not replace reperfusion or other definitive care.
Other medicines: High-intensity statin therapy is generally started early unless contraindicated. Other medicines, including beta blockers, depend on the patient’s condition and contraindications. Opioids are not routine first-line treatment for ischemic pain.
Reperfusion and invasive care
STEMI reperfusion
Restore coronary blood flow as quickly as possible. is the preferred reperfusion strategy when it can be delivered promptly. If timely PCI is not feasible, clinicians may consider for an eligible patient after checking the time course and contraindications, followed by transfer to a PCI-capable center. Fibrinolytic therapy is not a treatment for NSTEMI or . Cardiogenic shock or persistent ischemia requires urgent specialist-directed assessment and revascularization.
NSTEMI and
Routine has no role in NSTEMI or . Patients with ongoing or recurrent ischemia, hemodynamic instability, acute heart failure, or serious electrical instability need urgent assessment for invasive management. For others, the decision and timing of coronary angiography are guided by clinical risk, test results, comorbidities, and bleeding risk.
Care after the emergency phase
Care continues after initial stabilization. A typical plan includes individualized antiplatelet therapy, lipid lowering, risk-factor management, and cardiac rehabilitation.
At least 12 months of after discharge is recommended for many patients who are not at high bleeding risk. Treatment duration and regimen must be adjusted for bleeding risk and other clinical circumstances.