Initial Assessment and Management of Acute Coronary Syndrome
For any patient with suspected ACS, obtain and interpret a 12-lead ECG within 10 minutes of arrival and draw blood for high-sensitivity cardiac troponin immediately—these two tests form the diagnostic cornerstone and directly determine your management pathway. 1
Immediate Actions (First 10 Minutes)
Electrocardiographic Assessment
- Acquire a 12-lead ECG within 10 minutes and interpret it immediately to distinguish STEMI from non-ST-segment elevation ACS (NSTE-ACS). 1
- ST-segment elevation ≥1 mm in two contiguous leads defines STEMI and mandates immediate activation of the catheterization laboratory for primary PCI. 1, 2
- For suspected posterior STEMI, look for ST-segment depression in leads V1-V3 and obtain posterior leads V7-V9. 1
- For suspected right ventricular involvement in inferior STEMI, obtain right-sided leads. 1
- A normal initial ECG does NOT exclude ACS—serial ECGs are mandatory, especially during recurrent chest pain. 1, 2
Biomarker Testing
- Draw high-sensitivity cardiac troponin immediately with results available within 60 minutes. 1, 2
- Repeat troponin at 1-2 hours if using high-sensitivity assays, or at 3-6 hours if using conventional assays. 1
- A rise or fall in troponin with at least one value above the 99th percentile confirms myocardial infarction. 2
Supportive Measures
- Establish continuous cardiac monitoring to detect life-threatening arrhythmias. 1, 3
- Place intravenous access immediately. 2
- Provide supplemental oxygen only if oxygen saturation <90% or respiratory distress is present—routine oxygen in uncomplicated cases provides no benefit. 2
- Draw additional blood for complete blood count, basic metabolic panel (including creatinine), glucose, and coagulation studies. 2
Immediate Medical Therapy (Before Diagnostic Confirmation)
Antiplatelet Therapy
- Administer aspirin 162-325 mg immediately (chewed, non-enteric coated) unless active gastrointestinal bleeding or documented aspirin allergy exists. 2, 3
- Add a P2Y12 inhibitor (ticagrelor or prasugrel preferred over clopidogrel) once ACS is confirmed. 2, 3
Symptom Management
- Give sublingual nitroglycerin 0.4 mg every 5 minutes (up to 3 doses) for ongoing chest pain, unless systolic blood pressure <90 mmHg or recent phosphodiesterase-5 inhibitor use. 3
- Reserve morphine for severe, persistent chest pain unresponsive to nitroglycerin, recognizing it may delay absorption of oral antiplatelet agents. 2
STEMI Management Pathway
Reperfusion Strategy
- Do NOT delay reperfusion therapy to wait for troponin results or additional diagnostic testing. 2, 3
- Target primary PCI within 90 minutes of first medical contact (door-to-balloon time). 1, 3
- If primary PCI cannot be achieved within 90-120 minutes, administer fibrinolytic therapy within 30 minutes (door-to-needle time) for patients presenting ≤3 hours from symptom onset and age <75 years. 3, 4
- For patients ≥75 years requiring fibrinolysis, use half-dose alteplase, reteplase, or tenecteplase. 4
Prehospital Considerations
- Prehospital catheterization laboratory activation significantly reduces reperfusion times and mortality. 1
- Direct transport to a PCI-capable facility is preferred over transport to the nearest non-PCI hospital. 1
NSTE-ACS Management Pathway
Risk Stratification and Invasive Timing
Immediate invasive strategy (<2 hours) for patients with:
Early invasive strategy (within 24 hours) for patients with:
Invasive strategy within 72 hours for intermediate-risk patients without high-risk features. 3
Anticoagulation
- Initiate parenteral anticoagulation with one of the following options:
Beta-Blocker Therapy
- Initiate beta-blocker therapy unless contraindicated by heart failure, bradycardia (<60 bpm), hypotension (systolic BP <100 mmHg), or severe reactive airway disease. 2, 3
Critical Pitfalls to Avoid
- Never rely on a single troponin measurement—the "troponin-blind" interval exists where initial troponin may be negative despite ongoing MI. 2
- Do not dismiss atypical presentations, particularly in women, elderly patients, and those with diabetes who may present with dyspnea, nausea, or fatigue rather than chest pain. 3, 4
- Ensure troponin results are available within 60 minutes of blood draw to prevent treatment delays. 2
- Do not administer nitroglycerin to patients with right ventricular infarction (identified by ST elevation in right-sided leads) as it may cause profound hypotension. 1
- ST-segment depression in leads V1-V3 may represent posterior STEMI—obtain posterior leads and manage as STEMI if confirmed. 1
Long-Term Management (Initiated During Hospitalization)
Pharmacotherapy
- Start high-intensity statin therapy immediately (e.g., atorvastatin 80 mg or rosuvastatin 40 mg daily) unless contraindicated. 2, 3
- Prescribe an ACE inhibitor (or ARB if ACE intolerant) for patients with left ventricular ejection fraction ≤40%, heart failure, hypertension, or diabetes. 2, 3
- Continue beta-blocker therapy in patients with left ventricular ejection fraction ≤40%. 2, 3
- Add a mineralocorticoid-receptor antagonist (e.g., eplerenone) for patients with left ventricular ejection fraction ≤35% who have heart failure or diabetes, provided no significant renal dysfunction or hyperkalemia exists. 2, 3
- Continue dual antiplatelet therapy for 12 months unless high bleeding risk necessitates shorter duration. 2, 3