What are the key management steps for Acute Coronary Syndrome (ACS) ST-Elevation Myocardial Infarction (STEMI)?

Management of ACS STEMI

All STEMI patients should immediately chew 162-325 mg of non-enteric coated aspirin upon first medical contact and undergo rapid reperfusion therapy—either primary PCI within 90-120 minutes or fibrinolytic therapy within 30 minutes if PCI is not achievable within this timeframe. 1, 2

Immediate Initial Management (First 10 Minutes)

• Obtain 12-lead ECG within 10 minutes of emergency department arrival for all patients with chest discomfort or STEMI symptoms 2
• Administer aspirin 162-325 mg (non-enteric coated, chewed) immediately unless absolute contraindication exists 1
• Provide supplemental oxygen only if arterial oxygen saturation <90% or respiratory distress is present—routine oxygen administration is not indicated 1, 2, 3
• Administer morphine sulfate 2-4 mg IV with increments of 2-8 mg repeated at 5-15 minute intervals for ongoing ischemic pain or pulmonary congestion 1, 2, 3
• Initiate oral beta-blocker therapy promptly in patients without contraindications (avoid in frank cardiac failure, pulmonary congestion, hypotension, or bradycardia) 1
• Start IV nitroglycerin for persistent ischemia, heart failure, or hypertension if systolic BP >100 mmHg 1, 3

Critical Contraindications to Note:

• Do NOT administer IV beta-blockers acutely—oral beta-blockers are preferred 1
• Do NOT give beta-blockers or calcium channel blockers to patients with frank cardiac failure, pulmonary congestion, or low-output state 1

Reperfusion Strategy Decision Algorithm

Time-Critical Decision Points:

Primary PCI is preferred if:

• Can be performed within 90 minutes of first medical contact for high-risk patients presenting within 2 hours of symptom onset 2
• Can be performed within 120 minutes of first medical contact for other patients 1, 2, 3
• Patient has cardiogenic shock (regardless of time delay from MI onset) 1, 3
• Patient has contraindications to fibrinolytic therapy 1

Fibrinolytic therapy is indicated if:

• Primary PCI cannot be performed within 120 minutes of first medical contact 1, 2, 3
• Patient presents within 12 hours of symptom onset 1
• Administer within 30 minutes of hospital arrival 1, 2, 3

Timing of Antiplatelet Loading Dose:

• For UA/NSTEMI patients: loading dose should not be administered until coronary anatomy is established 4
• For STEMI patients presenting >12 hours after symptom onset: wait until coronary anatomy is established 4
• For STEMI patients presenting within 12 hours: loading dose may be given at time of diagnosis, though most receive it at time of PCI 4

Antiplatelet and Anticoagulation Therapy

Dual Antiplatelet Therapy (DAPT):

• Aspirin 75-162 mg daily indefinitely after initial loading dose 1, 3
• Add P2Y12 inhibitor (clopidogrel or prasugrel) as early as possible before PCI 2, 3
• Continue DAPT for at least 12 months in patients receiving stents 1, 2, 3

Prasugrel-Specific Considerations:

• Loading dose: 60 mg orally, then 10 mg daily 4
• Reduce to 5 mg daily in patients <60 kg body weight (increased bleeding risk) 4
• Generally NOT recommended in patients ≥75 years except in high-risk situations (diabetes or prior MI) 4
• Contraindicated in patients with prior TIA or stroke 4
• Discontinue at least 7 days before any surgery when possible 4

Anticoagulation:

• Initiate IV anticoagulation if not already accomplished in patients with recurrent ischemic chest discomfort 1

Post-Reperfusion Management

Within 24 Hours:

• Initiate ACE inhibitors in all patients, particularly those with anterior MI, heart failure, or LVEF ≤0.40 1, 3
  • Start with low-dose short-acting ACE inhibitor (e.g., captopril 1-6.25 mg) unless systolic BP <100 mmHg or >30 mmHg below baseline 1
• Start oral beta-blocker therapy within 24 hours in patients without contraindications and continue indefinitely 1, 3
• Initiate high-intensity statin therapy in all STEMI patients without contraindications 2

Long-Term Therapy:

• Aldosterone blockade for post-STEMI patients with LVEF ≤0.40 and either symptomatic heart failure or diabetes, provided creatinine ≤2.5 mg/dL (men) or ≤2.0 mg/dL (women) and potassium ≤5.0 mEq/L 1
• Discontinue NSAIDs (except aspirin) due to increased risks of mortality, reinfarction, hypertension, heart failure, and myocardial rupture 1, 2

Management of Complications

Cardiogenic Shock:

• Emergency revascularization (PCI or CABG) is recommended for patients <75 years who develop shock within 36 hours of MI, if revascularization can be performed within 18 hours of shock onset 1
• Consider emergency revascularization for selected patients ≥75 years with good prior functional status 1, 2, 3
• Intra-aortic balloon counterpulsation (IABP) when cardiogenic shock is not quickly reversed with pharmacological therapy 1, 3
• Inotropic/vasopressor support with dopamine (5-20 mcg/kg/min if SBP 70-100 mmHg) or dobutamine (5-20 mcg/kg/min) 1

Pulmonary Congestion/Heart Failure:

• Oxygen supplementation to maintain arterial saturation >90% 1
• Morphine sulfate for symptom relief 1
• Nitrates unless systolic BP <100 mmHg or >30 mmHg below baseline 1
• ACE inhibitors with careful titration starting at low doses 1
• Diuretics (furosemide, torsemide, or bumetanide) if volume overload is present 1
• Urgent echocardiography to estimate LV/RV function and exclude mechanical complications 1

Recurrent Ischemia:

• Escalate medical therapy with nitrates and beta-blockers to decrease myocardial oxygen demand 1
• Urgent cardiac catheterization for patients with hemodynamic instability, poor LV function, or large area of myocardium at risk 1
• Consider IABP insertion 1

Thromboembolic Complications:

• DVT/PE: Treat with full-dose LMWH for minimum 5 days plus warfarin (target INR 2-3) 1
• Acute ischemic stroke: Obtain neurological consultation, perform echocardiography and neuroimaging 1
• LV mural thrombus or akinetic segment: Moderate-intensity warfarin (INR 2-3) for at least 3 months in addition to aspirin 1

Critical Pitfalls to Avoid

• Do NOT delay reperfusion to wait for cardiac biomarker results—initiate treatment based on clinical presentation and ECG findings 2
• Do NOT use immediate-release nifedipine in STEMI patients due to reflex sympathetic activation, tachycardia, and hypotension 3
• Do NOT rely on serial biomarker measurements to diagnose reinfarction within the first 18 hours after STEMI onset 2
• Do NOT administer fibrinolytic therapy when increased ICP or intracranial hemorrhage is suspected (absolute contraindication) 5
• Avoid aggressive simultaneous use of hypotensive agents in pulmonary edema, which can precipitate iatrogenic cardiogenic shock 1
• Do NOT use facilitated PCI strategy (full-dose fibrinolysis followed by PCI) as it may be harmful 1

Special Populations

Right Ventricular Infarction:

• Obtain right-sided ECG leads in patients with inferior STEMI to screen for RV infarction 2

Elderly Patients (≥75 years):

• Fibrinolytic therapy at half dose for patients ≥75 years (or full-dose streptokinase if cost is a consideration) 6
• Emergency revascularization can still be effective in cardiogenic shock with good prior functional status 1, 2

Low Body Weight (<60 kg):

• Consider prasugrel 5 mg daily maintenance dose (instead of 10 mg) due to increased bleeding risk 4