What is the treatment for myocardial infarction (MI)?

Treatment for Myocardial Infarction (MI)

Primary PCI is the preferred reperfusion strategy for STEMI patients presenting within 12 hours of symptom onset, while immediate pharmacotherapy including aspirin, P2Y12 inhibitors, and anticoagulation should be initiated for all MI patients. 1

Immediate Management

Initial Assessment and Stabilization

• Obtain 12-lead ECG within 10 minutes of first medical contact
• Establish IV access immediately
• Monitor vital signs and provide oxygen only if saturation <94%
• Establish ECG monitoring with defibrillator capacity

Immediate Pharmacotherapy

• Administer aspirin 162-325 mg (chewed, non-enteric coated) immediately 1, 2
• Administer sublingual nitroglycerin 0.4 mg every 5 minutes (up to 3 doses) for ongoing chest pain if systolic BP >90 mmHg 1
• Consider morphine IV (2-4 mg, with additional 2-8 mg every 5-15 minutes as needed) for pain unrelieved by nitroglycerin 1

Reperfusion Strategies

Primary PCI

• Preferred when available within 90 minutes of first medical contact 1
• Mandatory for patients with cardiogenic shock or contraindications to fibrinolysis
• Should be performed regardless of time delay from MI onset in cardiogenic shock patients

Fibrinolytic Therapy

• Implement when primary PCI cannot be performed within 120 minutes
• Administer within 30 minutes of first medical contact
• Contraindications include prior intracranial hemorrhage, known cerebral vascular lesion, malignant intracranial neoplasm, recent ischemic stroke, active bleeding, suspected aortic dissection, and significant head/facial trauma within 3 months 1

Antiplatelet and Anticoagulant Therapy

Dual Antiplatelet Therapy (DAPT)

• Aspirin 75-100 mg daily indefinitely 1
• P2Y12 inhibitor for 12 months:
  • Preferred: Ticagrelor (180 mg loading dose, then 90 mg twice daily) or Prasugrel (60 mg loading dose, then 10 mg daily)
  • Alternative: Clopidogrel (600 mg loading dose, then 75 mg daily) 1, 2

Anticoagulation

• Unfractionated heparin or low molecular weight heparin during acute phase
• Avoid fondaparinux for primary PCI due to risk of catheter thrombosis 1

Post-MI Pharmacotherapy

Beta-Blockers

• Start within 24 hours for hemodynamically stable patients 1, 3
• For IV metoprolol: Three bolus injections of 5 mg at approximately 2-minute intervals, followed by oral metoprolol 50 mg every 6 hours, then 100 mg twice daily maintenance 3
• Particularly indicated for patients with heart failure and/or LVEF <40% 1

ACE Inhibitors/ARBs

• Start within 24 hours for patients with evidence of heart failure, LV systolic dysfunction, diabetes, or anterior infarct 1
• ARBs (preferably valsartan) are an alternative for ACE inhibitor-intolerant patients

Statins

• High-intensity statin therapy should be started as early as possible
• Target LDL-C <70 mg/dL or ≥50% reduction 1

Mineralocorticoid Receptor Antagonists (MRAs)

• Recommended for patients with LVEF <40% and heart failure without severe renal failure or hyperkalemia 1

Management of Complications

Arrhythmias

• Atrial fibrillation: Beta-blockers, digoxin, or amiodarone for rate control; consider cardioversion if hemodynamically unstable 4
• Ventricular arrhythmias: Immediate defibrillation for VF/pulseless VT
• Bradycardia: Atropine 0.3-0.5 mg IV (up to total 1.5-2.0 mg) for symptomatic bradycardia; consider temporary pacing if unresponsive 4

Heart Block

• First-degree heart block: No specific treatment needed
• Type I second-degree (Mobitz I): Usually requires no treatment unless hemodynamically compromised
• Type II second-degree (Mobitz II) and complete heart block: Insert temporary pacing electrode 4

Post-MI Monitoring and Follow-up

• Monitor for at least 24 hours after reperfusion 1
• Echocardiography to assess LV and RV function and detect complications
• Exercise testing (submaximal at 4-7 days or symptom-limited at 10-14 days) to assess functional capacity and risk stratification

Important Considerations and Pitfalls

• Time is myocardium: Minimize time from symptom onset to reperfusion therapy 1, 5
• Avoid NSAIDs (except aspirin) due to increased risk of mortality, reinfarction, and heart failure 1
• Avoid calcium channel blockers as they have not been shown to reduce mortality 1
• Avoid oral nitrates in acute MI; use IV nitroglycerin instead 1
• Avoid routine lidocaine administration as it may increase risk of asystole 4
• Avoid premature discontinuation of antiplatelet therapy due to increased risk of cardiovascular events 1, 2

The European Society of Cardiology guidelines represent the most current and comprehensive approach to MI management, emphasizing rapid reperfusion with primary PCI when available, or fibrinolysis when PCI cannot be performed in a timely manner, along with evidence-based pharmacotherapy to improve outcomes 1.