Management of ST-Elevation Myocardial Infarction (STEMI)
Immediately administer 162-325 mg of non-enteric coated aspirin upon first medical contact and proceed with urgent reperfusion therapy—either primary PCI within 120 minutes or fibrinolytic therapy within 30 minutes if PCI is not achievable within that timeframe. 1, 2, 3
Initial Assessment and Immediate Actions
Obtain a 12-lead ECG within 10 minutes of emergency department arrival for all patients with chest discomfort or symptoms suggestive of STEMI. 4, 1 If the initial ECG is non-diagnostic but clinical suspicion remains high, perform serial ECGs at 5-10 minute intervals or implement continuous 12-lead ST-segment monitoring. 4, 1
For patients with inferior STEMI, obtain right-sided ECG leads to screen for ST elevation suggestive of right ventricular infarction, as this finding significantly alters management (particularly regarding nitrate and fluid administration). 4, 1
Immediate Medical Therapy
Administer supplemental oxygen only to patients with arterial oxygen desaturation (SaO2 <90%) or overt pulmonary congestion—routine oxygen administration is not indicated. 4, 1, 2
Provide morphine sulfate for patients with ongoing ischemic pain or pulmonary congestion. 4, 1, 2
Initiate oral beta-blocker therapy promptly in patients without contraindications (no frank cardiac failure, pulmonary congestion, or signs of low-output state). 4, 1, 2 Intravenous beta-blockers may be reasonable for patients with tachyarrhythmias or hypertension. 2
Reperfusion Strategy Decision Algorithm
The critical decision point is whether primary PCI can be performed within 120 minutes of first medical contact. 1, 2, 3 For high-risk patients (large anterior infarction, age <75 years) presenting within 2 hours of symptom onset, the PCI-related delay should not exceed 90 minutes. 1, 5
Primary PCI Strategy (Preferred if achievable within 120 minutes)
Administer dual antiplatelet therapy before PCI as early as possible:
- Aspirin 162-325 mg (non-enteric coated) 1, 2, 3
- Plus a P2Y12 inhibitor: Prasugrel 60 mg loading dose is preferred over clopidogrel due to faster onset and superior effectiveness (reduces nonfatal MI from 9.0% to 6.8% and stent thrombosis from 2.8% to 1.6%). 3, 6, 5 Use clopidogrel 600 mg loading dose if prasugrel is contraindicated (prior stroke/TIA, age ≥75 years unless high-risk with diabetes or prior MI, weight <60 kg). 6, 5
Anticoagulation for primary PCI:
- Unfractionated heparin (UFH) with bolus of 60 U/kg (maximum 4000 U) followed by 12 U/kg/hour (maximum 1000 U/hr) adjusted to aPTT 1.5-2.0 times control. 4
- Bivalirudin is an alternative, particularly in patients with high bleeding risk. 5, 7
Glycoprotein IIb/IIIa inhibitors should be limited to patients with high intracoronary thrombus burden; upstream administration is not recommended. 5
Manual thrombus aspiration should be considered during primary PCI. 5, 7
Fibrinolytic Strategy (If primary PCI cannot be performed within 120 minutes)
Administer fibrinolytic therapy within 30 minutes of hospital arrival (door-to-needle time). 4, 1 Acceptable agents include:
- Tenecteplase (preferred, Grade 1A) 8
- Reteplase (Grade 1B) 8
- Alteplase (Grade 1C) 8
- Streptokinase (Grade 2B) 8
Adjunctive therapy with fibrinolysis:
- Aspirin 162-325 mg 1, 3
- Clopidogrel 300-600 mg loading dose 3, 5
- UFH or enoxaparin for anticoagulation 4
Critical: After fibrinolytic therapy, perform cardiac catheterization within 3-24 hours (pharmaco-invasive approach) with PCI if applicable, even if the patient appears clinically stable. 5, 8
Management of Cardiogenic Shock
For patients <75 years with cardiogenic shock developing within 36 hours of STEMI, perform emergency revascularization (PCI or CABG) if it can be accomplished within 18 hours of shock onset, regardless of time delay from MI onset. 4, 2, 3 For patients ≥75 years with good prior functional status, emergency revascularization should still be considered. 4, 2
Immediate management of cardiogenic shock:
- Rapid volume loading with IV infusion in patients without clinical volume overload 4
- Vasopressor support for hypotension not resolving after volume loading 4
- Intra-aortic balloon counterpulsation for patients not quickly stabilized with pharmacological therapy 4, 2, 3
- Urgent echocardiography to estimate LV/RV function and exclude mechanical complications 4
Management of Pulmonary Congestion/Heart Failure
Oxygen supplementation to arterial saturation >90% 4, 2
Morphine sulfate for symptom relief 4
ACE inhibitors starting with low-dose short-acting agent (captopril 1-6.25 mg) unless systolic BP <100 mm Hg or >30 mm Hg below baseline 4
Nitrates unless systolic BP <100 mm Hg or >30 mm Hg below baseline 4
Diuretics (low- to intermediate-dose furosemide, torsemide, or bumetanide) if volume overload is present; use caution in patients who have not received volume expansion 4
Critical pitfall: Do NOT administer beta-blockers or calcium channel blockers acutely to patients with frank cardiac failure, pulmonary congestion, or signs of low-output state. 4, 2 If pulmonary congestion occurs with marginal or low blood pressure, circulatory support with inotropic/vasopressor agents and/or intra-aortic balloon counterpulsation is often needed. 4
Post-STEMI Medical Management
Initiate ACE inhibitors within 24 hours in all patients, particularly those with anterior STEMI, heart failure, or ejection fraction ≤0.40. 4, 1, 2, 3
Continue oral beta-blockers indefinitely in all eligible patients; for those with persistent heart failure, initiate low doses with gradual outpatient titration. 4, 1, 3
High-intensity statin therapy should be initiated or continued in all STEMI patients without contraindications. 1, 2
Dual antiplatelet therapy (DAPT) with aspirin plus a P2Y12 inhibitor should be continued for at least 12 months in patients receiving stents:
- Prasugrel 10 mg daily (or 5 mg daily if ≥75 years or <60 kg) 6, 5
- Or clopidogrel 75 mg daily 1, 2, 3, 5
Long-term aldosterone blockade should be prescribed 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. 4
Blood pressure control to target <140/90 mm Hg (<130/80 mm Hg for patients with diabetes or chronic kidney disease) using lifestyle modifications and pharmacotherapy. 4
Warfarin anticoagulation (INR 2.0-3.0) for patients with persistent or paroxysmal atrial fibrillation, or for at least 3 months if LV thrombus is noted on imaging. 4
Special Populations and Transfer Protocols
Every community should have a written protocol guiding EMS personnel in determining where to take STEMI patients. 4, 1 Patients with STEMI and cardiogenic shock are high-priority triage cases requiring immediate or secondary transfer to PCI-capable facilities. 4
Patients with contraindications to fibrinolytic therapy should be transferred promptly (primary-receiving hospital door-to-departure time <30 minutes) to PCI-capable facilities. 4, 1
Prehospital fibrinolysis is reasonable in settings with physicians in ambulances or well-organized EMS systems with 12-lead ECG transmission capability, paramedic training in ECG interpretation, online medical command, and experienced medical directors. 4
Emergency CABG Indications
Emergency or urgent CABG should be performed for:
- Failed PCI with persistent pain or hemodynamic instability 4
- Persistent/recurrent ischemia refractory to medical therapy with suitable anatomy 4
- Surgical repair of post-infarction ventricular septal rupture or mitral valve insufficiency 4
- Cardiogenic shock with severe multivessel or left main disease (age <75 years, within 18 hours of shock onset) 4
- Life-threatening ventricular arrhythmias with ≥50% left main stenosis and/or triple-vessel disease 4
When possible, discontinue prasugrel at least 7 days prior to any surgery to reduce bleeding risk. 6
Critical Pitfalls to Avoid
Do not delay reperfusion therapy to wait for cardiac biomarker results—initiate treatment based on clinical presentation and ECG findings. 1
Do not use immediate-release nifedipine in STEMI patients due to reflex sympathetic activation, tachycardia, and hypotension. 1
Do not rely on serial biomarker measurements to diagnose reinfarction within the first 18 hours after STEMI onset. 1
Do not discontinue prasugrel or other antiplatelet therapy prematurely—stopping increases the risk of subsequent cardiovascular events including stent thrombosis, MI, and death. 6
Suspect bleeding in any patient who becomes hypotensive after recent invasive or surgical procedures; if possible, manage bleeding without discontinuing prasugrel. 6
Patients routinely taking NSAIDs before STEMI should discontinue these agents due to increased risks of adverse outcomes. 1