What is the management of myocardial infarction (MI)?

Management of Myocardial Infarction (MI)

The management of myocardial infarction requires immediate reperfusion therapy for patients with ST-segment elevation or new left bundle-branch block, along with comprehensive pharmacological therapy including aspirin, P2Y12 inhibitors, beta-blockers, and ACE inhibitors to reduce mortality and improve outcomes. 1

Initial Emergency Department Management

• Administer oxygen via nasal prongs immediately upon arrival 2, 3
• Give sublingual nitroglycerin unless systolic blood pressure is <90 mmHg or heart rate is <50 or >100 beats per minute 2, 3
• Administer adequate analgesia (morphine sulfate or meperidine) for pain control 2, 4
• Give aspirin 160-325 mg orally immediately 2, 1, 5
• Perform a 12-lead ECG within 10 minutes of arrival to assess for ST-segment elevation or new LBBB 2, 3
• Establish continuous cardiac monitoring with emergency resuscitation equipment readily available 3

Reperfusion Strategy

• Evaluate for immediate reperfusion therapy if presenting within 12 hours of symptom onset 2, 3, 1
• Primary PCI is the preferred reperfusion strategy when it can be performed within 90 minutes by skilled personnel with access to emergency CABG surgery 2, 1, 6
• If primary PCI cannot be performed in a timely manner, administer fibrinolytic therapy within 12 hours of symptom onset 2, 1
• The greatest benefit from thrombolysis occurs when administered within the first hour of symptom onset (35 lives saved per 1000 patients treated) 2, 3
• For patients receiving alteplase (tPA), continue intravenous heparin for an additional 48 hours 2

Pharmacological Management in First 24 Hours

• Begin intravenous nitroglycerin for 24-48 hours if no hypotension, bradycardia, or excessive tachycardia is present 2, 3
• Administer early intravenous beta-blocker therapy followed by oral therapy if no contraindications exist 2, 1, 7
• For metoprolol, administer three bolus injections of 5 mg intravenously at approximately 2-minute intervals, followed by 50 mg orally every 6 hours, starting 15 minutes after the last IV dose 7
• Consider dual antiplatelet therapy (DAPT) with aspirin plus a P2Y12 inhibitor (such as prasugrel) for patients undergoing PCI 1, 8
• For prasugrel, administer a 60 mg oral loading dose followed by 10 mg daily (consider 5 mg daily for patients <60 kg) 8
• Consider ACE inhibitors, particularly for patients with anterior MI or left ventricular dysfunction 3, 1

Monitoring and Management After First 24 Hours

• Continue aspirin 160-325 mg daily indefinitely 2, 1
• Continue beta-blocker therapy for at least 6 weeks 2, 3
• Maintain intravenous nitroglycerin for 24-48 hours 2, 3
• Administer magnesium sulfate as needed to replete magnesium deficits for 24 hours 2, 3
• Monitor for and promptly manage complications such as recurrent chest pain, heart failure, arrhythmias, and mechanical complications 2

Management of Complications

• For recurrent chest pain due to pericarditis, administer high-dose aspirin (650 mg every 4-6 hours) 2
• For recurrent chest pain due to ischemia, treat with intravenous nitroglycerin, analgesics, and antithrombotic medications (aspirin, heparin) 2
• For heart failure, administer diuretics (usually intravenous furosemide) and afterload-reducing agents 2, 1
• For cardiogenic shock, consider intra-aortic balloon counterpulsation and emergency coronary angiography followed by PCI or CABG 2, 1
• For right ventricular infarction with dysfunction, provide vigorous intravascular volume expansion (using normal saline) and inotropic agents if hypotension persists 2

Pre-Discharge Evaluation

• Perform echocardiography during hospital stay to assess ventricular function and detect complications 1
• Before discharge or shortly thereafter, conduct exercise testing (submaximal at 4-7 days or symptom-limited at 10-14 days) 2, 1
• Exercise testing helps assess functional capacity, evaluate efficacy of medical regimen, and stratify risk for subsequent cardiac events 2

Long-Term Management

• Continue aspirin, beta-blockers, and ACE inhibitors indefinitely 2, 1
• Encourage smoking cessation with appropriate support 2, 1
• Recommend participation in a formal cardiac rehabilitation program 2, 1
• Advise patients to achieve ideal weight and follow a diet low in saturated fat and cholesterol 2, 1
• Target LDL cholesterol <100 mg/dL with appropriate diet and medication 2
• Encourage regular exercise (at least 20 minutes of brisk walking three times weekly) 2, 1

Common Pitfalls and Caveats

• Delaying reperfusion therapy beyond the golden first hour significantly reduces its effectiveness 3, 9
• Using oral nitrates instead of intravenous nitroglycerin in the acute phase prevents proper dose titration 2, 3
• Calcium channel blockers have not been shown to reduce mortality and may be harmful in certain patients 2
• Prasugrel is contraindicated in patients with a history of TIA or stroke and should be used cautiously in patients ≥75 years of age due to increased bleeding risk 8
• Avoid prophylactic antiarrhythmic agents in the first 24 hours 3