What is the management approach for a patient with myocardial infarction (MI)?

Management of Myocardial Infarction

Immediate reperfusion therapy should be initiated for patients with ST-segment elevation MI (STEMI) or new LBBB within 12 hours of symptom onset, while patients without ST-elevation should receive medical therapy and risk stratification. 1

Initial Management (First 10-20 Minutes)

Immediate Actions

• Administer aspirin 162-325 mg (chewed) immediately 1
• Perform 12-lead ECG within 10 minutes of arrival 1
• Provide oxygen via nasal prongs (2-4 L/min) if breathlessness or heart failure are present 1
• Administer sublingual nitroglycerin (unless systolic BP <90 mmHg or heart rate <50 or >100 bpm) 1
• Provide adequate analgesia with morphine sulfate (4-8 mg IV initially, with 2-8 mg IV every 5-15 minutes as needed) 1

Reperfusion Strategy Based on ECG

• For STEMI or new LBBB:
  • Primary PCI if available within 90 minutes of first medical contact 1
  • Fibrinolytic therapy if PCI not available within required timeframe and symptom onset <12 hours 1
  • Greatest benefit occurs when thrombolysis is initiated within 6 hours of symptom onset 2
• For Non-STEMI:
  • Do not administer thrombolytic therapy 2
  • Consider early invasive strategy based on risk stratification 1

Hospital Management (First 24-48 Hours)

Pharmacological Therapy

• Continue aspirin 160-325 mg daily 1
• Add dual antiplatelet therapy with clopidogrel 75 mg daily 1
• Initiate intravenous β-blockers followed by oral therapy if no contraindications exist 1
  • For metoprolol: 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 orally twice daily 3
• Consider IV nitroglycerin infusion for 24-48 hours if no hypotension, bradycardia, or tachycardia 1
• Initiate ACE inhibitor therapy within 24 hours in stable patients 1
  • For lisinopril: Start with 5 mg within 24 hours of symptom onset, 5 mg after 24 hours, then 10 mg daily (2.5 mg if systolic BP <120 mmHg) 4
• Consider anticoagulation with heparin for large anterior MI or LV mural thrombus 1

Monitoring and Supportive Care

• Maintain continuous ECG monitoring for arrhythmia detection 1
• Assess for hypotension, signs of tissue hypoperfusion, and left ventricular function 1
• Have emergency equipment readily available (atropine, lidocaine, transcutaneous pacing patches, defibrillator, epinephrine) 1

Management of Complications

Cardiogenic Shock

• Consider intra-aortic balloon pump, emergency coronary angiography, and revascularization 1
• Cardiogenic shock affects up to 10% of MI patients and carries a 30-day mortality rate of approximately 40% 5
• Immediate revascularization of the infarct-related coronary artery is the only treatment supported by randomized clinical trials 5

Right Ventricular Infarction

• Provide aggressive intravascular volume expansion with normal saline and inotropic agents if hypotension persists 1

Heart Failure

• Administer IV furosemide and afterload-reducing agents 1
• Consider ACE inhibitors for long-term management 1

Pericarditis

• Administer high-dose aspirin (650 mg every 4-6 hours) 1

Pre-Discharge Evaluation (4-14 Days)

• Perform standard exercise testing:
  • Submaximal at 4-7 days or
  • Symptom-limited at 10-14 days 2
• Assess left ventricular function with echocardiography 1

Long-Term Management

Pharmacological Therapy

• Continue aspirin 160-325 mg daily indefinitely 1
• Continue β-blockers for at least 6 weeks, then transition to long-term oral therapy 1
• Continue ACE inhibitors at appropriate doses 1
• Consider statins to achieve LDL <100 mg/dL (drug therapy if LDL >130 mg/dL despite diet) 1

Lifestyle Modifications

• Achieve ideal weight 1
• Follow low saturated fat and cholesterol diet 1
• Implement smoking cessation 1
• Engage in regular exercise (20 minutes of brisk walking at least three times weekly) 2
• Participate in cardiac rehabilitation 1

Important Caveats

• Time is critical - the benefit of reperfusion therapy is greatest when initiated within the first hour of symptom onset 1
• Calcium channel blockers have not been shown to reduce mortality in acute MI and may be harmful in certain patients 1
• Thrombolytic therapy is associated with a slightly increased risk of intracranial hemorrhage, particularly in patients >65 years, weight <70 kg, hypertension, and TPA administration 2
• Primary PCI should only be performed by skilled personnel with backup emergency CABG availability 2
• Patients with acute MI treated with lisinopril may have higher incidence of persistent hypotension and renal dysfunction 4