What is the management approach for ST-Elevation Myocardial Infarction (STEMI)?

Management of ST-Elevation Myocardial Infarction (STEMI)

Immediately administer 162-325 mg of non-enteric coated aspirin (chewed) to all STEMI patients upon first medical contact, and proceed with urgent reperfusion therapy—primary PCI if achievable within 120 minutes of diagnosis, or fibrinolysis within 30 minutes if PCI cannot be performed in time. 1, 2

Initial Assessment and Immediate Actions

ECG and Diagnosis

• Obtain a 12-lead ECG within 10 minutes of emergency department arrival for all patients with chest discomfort or STEMI symptoms 2
• STEMI is defined as ST-segment elevation >0.1 mV in at least two contiguous precordial or adjacent limb leads, new left bundle branch block, or true posterior MI 1
• If the initial ECG is non-diagnostic but clinical suspicion remains high, perform serial ECGs at 5-10 minute intervals 2
• For inferior STEMI, obtain right-sided ECG leads to screen for right ventricular infarction 2
• Do not delay reperfusion therapy to wait for cardiac biomarker results—initiate treatment based on clinical presentation and ECG findings 2

Immediate Medical Therapy

• Aspirin: 162-325 mg non-enteric coated, chewed immediately 1, 2, 3
• Oxygen: Administer supplemental oxygen only to patients with arterial oxygen desaturation (SaO₂ <90%) or respiratory distress—routine oxygen in non-hypoxemic patients is not indicated 1, 2, 3
• Morphine sulfate: Provide for ongoing ischemic pain or pulmonary congestion 2, 3, 4
• Beta-blockers: Initiate oral beta-blocker therapy promptly in patients without contraindications (avoid in frank cardiac failure, pulmonary congestion, hypotension, bradycardia, or signs of low-output state) 2, 3, 4
• Nitroglycerin: Intravenous administration in the first 48 hours for persistent ischemia, heart failure, or hypertension 3

Reperfusion Strategy Decision Algorithm

Critical Time-Based Decision Point

The fundamental decision is whether primary PCI can be performed within 120 minutes of STEMI diagnosis (first medical contact to device time) 1, 2

Primary PCI Strategy (Preferred)

Choose primary PCI if:

• First medical contact-to-device time can be achieved within 120 minutes 1, 2
• For high-risk patients presenting within 2 hours of symptom onset, PCI-related delay should not exceed 90 minutes 2
• Door-to-balloon time should be <90 minutes 3, 4

PCI-specific management:

• Patients should bypass the emergency department and transfer directly to the catheterization laboratory 1, 2
• Administer dual antiplatelet therapy before or at the time of PCI: aspirin plus a potent P2Y12 inhibitor (prasugrel or ticagrelor preferred over clopidogrel) 1, 4
• Use radial access as the standard approach 1
• Routine drug-eluting stent (DES) implantation is the standard of care 1
• Avoid routine thrombus aspiration or deferred stenting—these are contraindicated 1
• Anticoagulation with unfractionated heparin (bolus of 60 U/kg, maximum 4000 U IV; initial infusion 12 U/kg per hour, maximum 1000 U/h) 1
• Bivalirudin or enoxaparin may be used as alternatives to unfractionated heparin 1
• Glycoprotein IIb/IIIa inhibitors should be reserved only for patients with high intracoronary thrombus burden, not used routinely 1

Fibrinolytic Strategy

Choose fibrinolysis if:

• Primary PCI cannot be performed within 120 minutes of STEMI diagnosis 1, 2
• Patient presents within 12 hours of symptom onset without contraindications 1

Fibrinolysis-specific management:

• Initiate fibrinolytic therapy within 30 minutes of hospital arrival, preferably in the pre-hospital setting 1, 2, 3
• Use a fibrin-specific agent: tenecteplase, alteplase, or reteplase 1
• Administer oral or intravenous aspirin 1
• Add clopidogrel 300 mg loading dose, then 75 mg daily 1, 5
• Anticoagulation with enoxaparin IV followed by subcutaneous (preferred over unfractionated heparin) or weight-adjusted unfractionated heparin 1
• Transfer all patients to a PCI-capable center immediately after fibrinolysis 1
• Perform angiography and PCI of the infarct-related artery between 2-24 hours after successful fibrinolysis 1
• Perform rescue PCI immediately if fibrinolysis has failed (<50% ST-segment resolution at 60-90 minutes) or at any time with hemodynamic/electrical instability or worsening ischemia 1

Special Circumstances Requiring Immediate PCI

• Cardiogenic shock: Immediate transfer to facilities capable of cardiac catheterization and rapid revascularization (PCI or CABG) regardless of time delay from MI onset, especially in patients <75 years if performed within 18 hours of shock onset 2, 3, 4
• Contraindications to fibrinolysis: Immediate transfer to PCI-capable facilities 2
• Severe congestive heart failure: Consider invasive strategy 1

Antithrombotic Therapy

Dual Antiplatelet Therapy (DAPT)

For primary PCI:

• Loading dose of aspirin plus prasugrel (60 mg loading dose) or ticagrelor (180 mg loading dose) as early as possible 1, 4
• Clopidogrel (600 mg loading dose) only if prasugrel or ticagrelor are unavailable or contraindicated 1
• Prasugrel is contraindicated in patients with history of stroke or TIA 1

For fibrinolysis:

• Aspirin plus clopidogrel (300 mg loading dose) 1, 5

Maintenance DAPT:

• Continue aspirin (75-100 mg daily) plus P2Y12 inhibitor for 12 months in all patients 1, 2, 3
• Prasugrel 10 mg daily (or 5 mg daily if ≥75 years or <60 kg body weight) 1
• Ticagrelor 90 mg twice daily 1, 6
• Clopidogrel 75 mg daily if prasugrel or ticagrelor contraindicated 1
• For patients undergoing CABG, withhold clopidogrel for at least 5 days (preferably 7) unless urgency outweighs bleeding risk 1

Anticoagulation

• Unfractionated heparin, enoxaparin, or bivalirudin during acute phase 1
• For high-risk patients (large or anterior MI, atrial fibrillation, previous embolus, known LV thrombus, cardiogenic shock): continue anticoagulation with UFH or LMWH 1

Post-STEMI Medical Management

ACE Inhibitors/ARBs

• Initiate ACE inhibitors within 24 hours in all patients, particularly those with anterior MI, heart failure, or ejection fraction ≤0.40 1, 3, 4
• Target blood pressure <140/90 mm Hg (<130/80 mm Hg for patients with diabetes or chronic kidney disease) 1
• Use ARBs in patients intolerant of ACE inhibitors 3

Beta-Blockers

• Continue oral beta-blockers indefinitely in all eligible patients 1, 3, 4
• Benefits demonstrated for secondary prevention across all age groups 1
• In patients with moderate or severe LV failure, use gradual titration 1

Statins

• Initiate high-intensity statin therapy in all STEMI patients without contraindications 2, 4
• Target HbA1c <7% in diabetic patients 1

Long-term Anticoagulation

• Warfarin (INR 2.0-3.0) for patients with persistent or paroxysmal atrial fibrillation 1
• Warfarin for at least 3 months (indefinitely if no increased bleeding risk) in patients with LV thrombus 1
• Consider warfarin in patients with severe LV dysfunction and extensive regional wall-motion abnormalities 1

Medications to Avoid

• Discontinue NSAIDs (except aspirin) due to increased risks of mortality, reinfarction, hypertension, heart failure, and myocardial rupture 1, 2
• Avoid immediate-release nifedipine due to reflex sympathetic activation, tachycardia, and hypotension 2, 3
• Do not use short-acting dihydropyridine calcium channel blockers for hypertension treatment 1

Management of Complications

Cardiogenic Shock

• Emergency revascularization (PCI or CABG) regardless of time delay from MI onset 3, 4
• Intra-aortic balloon counterpulsation for patients not quickly stabilized with pharmacological therapy 3, 4
• For patients ≥75 years, emergency revascularization can still be effective, especially with good prior functional status 2, 3, 4

Mechanical Complications

• Ventricular septal rupture, free wall rupture, and papillary muscle rupture require urgent surgical consultation 3

Hemodynamic Monitoring

• Pulmonary artery catheter monitoring for severe or progressive heart failure, cardiogenic shock, progressive hypotension, or suspected mechanical complications 1
• Avoid pulmonary artery catheter monitoring in patients without hemodynamic instability or respiratory compromise 1
• Avoid intra-arterial pressure monitoring in patients without pulmonary congestion who have adequate tissue perfusion without circulatory support 1

Arrhythmias and Thromboembolic Events

• Deep venous thrombosis prophylaxis with subcutaneous LMWH or UFH (7500-12,500 U twice daily) until completely ambulatory may be considered, though effectiveness is not well established with routine aspirin use and early mobilization 1
• For established DVT or pulmonary embolism, treat with full-dose LMWH and warfarin 3

Post-Discharge Care and Secondary Prevention

Imaging and Risk Stratification

• Routine echocardiography during hospital stay to assess LV and RV function, detect mechanical complications, and exclude LV thrombus 1
• Follow-up ECGs at 24 hours and hospital discharge to assess reperfusion success and infarct extent 1

Lifestyle Modifications

• Identify smokers and provide repeated cessation advice with follow-up support, nicotine replacement, varenicline, or bupropion 1
• Cardiac rehabilitation program participation 1
• Exercise for minimum 30 minutes daily (or at least 3-4 times weekly) with walking, jogging, cycling, or other aerobic activity 1
• Weight control, dietary changes, physical activity, and sodium restriction for blood pressure control 1

Early Ambulation and Discharge

• Early ambulation and early discharge are optimal for uncomplicated patients 1
• This limited time emphasizes the importance of rapid implementation of secondary prevention measures 1

Critical Pitfalls to Avoid

• Never delay reperfusion for biomarkers: Treatment decisions are based on clinical presentation and ECG, not laboratory results 2
• Avoid facilitated PCI with full-dose fibrinolysis: This strategy may be harmful and is no longer recommended 1
• Do not use beta-blockers or calcium channel blockers acutely in patients with frank cardiac failure, pulmonary congestion, or low-output state 1, 4
• Do not perform routine PCI of occluded infarct-related artery >48 hours after STEMI onset in asymptomatic patients 1
• Avoid fondaparinux for primary PCI 1
• Do not rely on serial biomarkers for reinfarction diagnosis within the first 18 hours after STEMI 2