What is the management of myocardial infarction (MI)?

Management of Myocardial Infarction

The management of myocardial infarction requires immediate reperfusion therapy with primary percutaneous coronary intervention (PCI) within 90-120 minutes of first medical contact, or fibrinolysis within 30 minutes if PCI cannot be performed within the timeframe. 1

Initial Assessment and Immediate Management

• Immediate actions upon presentation:
  • Administer aspirin 162-325 mg (chewed) 2, 1
  • Establish IV access
  • Obtain 12-lead ECG within 10 minutes
  • Assess vital signs and oxygen saturation (provide oxygen only if saturation <94%) 1
  • 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 Strategy

Primary PCI Strategy

• Preferred when available within 90-120 minutes of first medical contact 2, 1
• Routine radial access and drug-eluting stent implantation is the standard of care 2
• Avoid routine thrombus aspiration or deferred stenting 2

Fibrinolytic Therapy

• Administer when primary PCI cannot be performed within 120 minutes 2, 1
• Most effective within first 2-3 hours of symptom onset 1
• Fibrin-specific agents (tenecteplase, alteplase, or reteplase) are preferred 1
• Transfer to a PCI-capable center immediately after fibrinolysis 1
• Rescue PCI is indicated if fibrinolysis fails (<50% ST-segment resolution at 60-90 min) 1

Antithrombotic Therapy

Antiplatelet Therapy

• Aspirin:
  • Loading dose: 162-325 mg 2, 1
  • Maintenance dose: 75-100 mg daily indefinitely 1
• P2Y12 inhibitors:
  • Clopidogrel: 300 mg loading dose (≤75 years old), then 75 mg daily 2, 1
  • Prasugrel: 60 mg loading dose, then 10 mg daily (contraindicated in patients with history of stroke/TIA or age ≥75 years) 3
  • Ticagrelor: Alternative to clopidogrel or prasugrel 1
  • Duration: 12 months of dual antiplatelet therapy (DAPT) 1

Anticoagulation

• Enoxaparin preferred over unfractionated heparin for fibrinolysis 1
• Unfractionated heparin for primary PCI (enoxaparin or bivalirudin as alternatives) 2
• Continue until revascularization or hospital discharge (up to 8 days) 1

Additional Pharmacological Therapy

Beta-Blockers

• Initiate oral beta-blockers within 24 hours for hemodynamically stable patients 2, 1
• Avoid intravenous beta-blockers in STEMI patients 2
• For early treatment of MI, metoprolol can be given as three bolus injections of 5 mg IV at 2-minute intervals, followed by 50 mg orally every 6 hours for 48 hours, then 100 mg twice daily 4

ACE Inhibitors

• Start within 24 hours for patients with:
  • Evidence of heart failure
  • Left ventricular systolic dysfunction
  • Diabetes
  • Anterior infarct 1
• Lisinopril has been shown to reduce mortality when started within 24 hours of MI onset 5

Statins

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

Nitrates

• IV nitroglycerin preferred over oral nitrates in acute phase 1
• Do not substitute nitroglycerin for narcotic analgesics 1

Post-MI Monitoring and Care

• Monitor for at least 24 hours after reperfusion 2, 1
• Assess for complications:
  • Recurrent ischemia/reinfarction
  • Heart failure
  • Arrhythmias
  • Mechanical complications (ventricular septal rupture, free wall rupture, papillary muscle rupture)
• Consider non-invasive imaging to assess left ventricular function 2
• For non-IRA (infarct-related artery) lesions, treatment of severe stenosis should be considered before hospital discharge 2

Rehabilitation and Secondary Prevention

• Cardiac rehabilitation is recommended for all patients 1
• Lifestyle modifications:
  • Smoking cessation
  • Diet low in saturated fat and cholesterol
  • Regular physical activity
  • Weight management

Important Cautions and Contraindications

• Avoid NSAIDs (except aspirin) due to increased risks of mortality, reinfarction, and heart failure 2, 1
• Avoid calcium channel blockers as they have not been shown to reduce mortality and may be harmful 1
• Avoid fondaparinux for primary PCI due to risk of catheter thrombosis 1
• Avoid oral nitrates in acute MI due to inability to titrate dose in evolving hemodynamic situations 1
• Recognize atypical presentations: Up to 33% of MI patients present without chest pain, particularly older patients, women, and those with diabetes. These patients often experience delayed diagnosis and treatment, resulting in higher mortality (23.3% vs 9.3%) 6

Special Considerations

• For patients <60 kg on prasugrel, consider lowering maintenance dose to 5 mg due to increased bleeding risk 3
• For patients ≥75 years, prasugrel is generally not recommended except in high-risk situations (diabetes or prior MI) 3
• Discontinue prasugrel at least 7 days prior to CABG surgery when possible 3
• Patients with MI but without significant coronary artery stenosis (MINOCA) require additional diagnostic tests to identify etiology and tailor appropriate therapy 2