What is the management and treatment for a myocardial infarction (MI)?

Management and Treatment of Myocardial Infarction

For acute MI, immediately initiate reperfusion therapy with primary PCI (if achievable within 90 minutes) or fibrinolysis (if PCI cannot be performed within this timeframe), as this reduces mortality by 21% when started early. 1

Immediate Emergency Department Management (First 10 Minutes)

• Obtain a 12-lead ECG within 10 minutes of arrival to identify ST-segment elevation ≥1 mm in contiguous leads or new left bundle branch block 2, 1, 3
• Administer aspirin 160-325 mg orally immediately—this is non-negotiable and should not wait for any confirmatory testing 2, 1, 3
• Provide oxygen via nasal prongs only if oxygen saturation is <90% or PaO₂ <60 mmHg (avoid routine oxygen administration) 1, 3
• Give sublingual nitroglycerin unless systolic BP <90 mmHg or heart rate <50 or >100 bpm 1, 3
• Establish continuous cardiac monitoring with defibrillator immediately available 2, 1
• Administer titrated intravenous morphine for pain control if needed 1, 3

Critical pitfall to avoid: Do not delay treatment waiting for cardiac biomarkers in patients with ST-elevation or new LBBB—ECG findings alone warrant immediate reperfusion 3

Reperfusion Strategy (Door-to-Treatment Goals)

Primary PCI (Preferred Method)

• Primary PCI is the preferred reperfusion strategy if it can be performed within 90 minutes of first medical contact (or 120 minutes from STEMI diagnosis) 2, 1
• Door-to-balloon time must be ≤90 minutes 3
• Administer unfractionated heparin, loading dose of aspirin, and prasugrel or ticagrelor (preferred over clopidogrel) for primary PCI 1

Fibrinolytic Therapy (When PCI Unavailable)

• Initiate fibrinolysis within 10 minutes of STEMI diagnosis if primary PCI cannot be performed within 120 minutes 1
• Door-to-needle time must be ≤30 minutes 3
• Greatest benefit occurs within the first hour ("golden hour"), saving 35 lives per 1,000 patients treated 1, 3
• Benefit progressively diminishes after 6 hours but extends to 12 hours (16 lives saved per 1,000 patients treated between 7-12 hours) 3
• Administer enoxaparin, loading dose of aspirin, and clopidogrel 75 mg daily with fibrinolysis 1

Time-critical window: Reperfusion therapy should be initiated within 12 hours of symptom onset; beyond 12 hours offers little benefit in most patients 3

Pharmacological Management in First 24-48 Hours

Antiplatelet Therapy

• Continue aspirin 160-325 mg daily indefinitely 4, 1
• For acute coronary syndrome requiring rapid antiplatelet effect, initiate clopidogrel with a 300 mg oral loading dose, then 75 mg once daily 5
• Important caveat: Consider alternative P2Y12 inhibitor (ticagrelor or prasugrel) in patients identified as CYP2C19 poor metabolizers, as clopidogrel has reduced effectiveness in these patients 5
• Dual antiplatelet therapy (DAPT) should continue for one year 1

Beta-Blocker Therapy

• Administer early intravenous β-adrenergic blocker therapy followed by oral therapy, provided no contraindications exist 4, 2
• Beta-blocker therapy should be initiated regardless of whether reperfusion therapy was given, as it diminishes morbidity and mortality 4
• Continue for minimum of 6 weeks, though indefinite use is recommended 4, 1

Nitroglycerin

• Begin intravenous nitroglycerin for 24-48 hours if no hypotension, bradycardia, or excessive tachycardia is present 4, 2
• Intravenous infusion can be titrated successfully with frequent measurement of heart rate and blood pressure 4
• Do not use nitroglycerin as a substitute for narcotic analgesics 4

Anticoagulation

• Administer intravenous heparin, particularly for patients with large anterior MI who are at high risk for LV mural thrombus and embolic stroke 2

Medications to Avoid

• Calcium channel blockers have not been shown to reduce mortality in acute MI and may be harmful in certain patients with cardiovascular disease 4

Management of Complications During Hospitalization

Recurrent Chest Pain

• If due to pericarditis: Administer high-dose aspirin 650 mg every 4-6 hours 4
• If due to myocardial ischemia: Treat with intravenous nitroglycerin, analgesics, and antithrombotic medications (aspirin, heparin); consider coronary angiography with subsequent revascularization 4

Heart Failure

• Administer diuretic (usually intravenous furosemide) and an afterload-reducing agent 4

Cardiogenic Shock

• Consider insertion of intra-aortic balloon pump for hemodynamic support 4
• Proceed to emergency coronary angiography followed by PTCA or CABG 4

Right Ventricular Infarction

• Treat vigorously with intravascular volume expansion using normal saline 4
• Add inotropic agents if hypotension persists 4

Special Considerations for Anterior MI

• Patients with anterior MI are at higher risk for left ventricular dysfunction and heart failure 2
• Perform echocardiography to evaluate LV function and detect potential complications such as mural thrombus 2
• For high-risk anterior MI patients after fibrinolysis, immediate transfer to PCI facility within 6 hours improves outcomes, reducing death, reinfarction, recurrent ischemia, heart failure, and cardiogenic shock (11.0% vs 17.2%) 2

Pre-Discharge Assessment (4-14 Days)

• Perform standard exercise testing: submaximal at 4-7 days or symptom-limited at 10-14 days 4
• This assesses functional capacity for home/work tasks, evaluates efficacy of medical regimen, and stratifies risk for subsequent cardiac events 4

Long-Term Management (Indefinite Duration)

Pharmacotherapy

• Continue aspirin, β-adrenoceptor blocker, and ACE inhibitor indefinitely 4, 1
• ACE inhibitors are especially important for anterior MI or LV dysfunction 1

Lipid Management

• Target LDL cholesterol <100 mg/dL 4
• Initiate drug therapy if LDL >130 mg/dL despite diet 4

Lifestyle Modifications

• Smoking cessation is essential and non-negotiable 4
• Achieve ideal body weight through diet low in saturated fat and cholesterol 4
• Participate in formal cardiac rehabilitation program 4
• Engage in 20 minutes of exercise at brisk walking level at least three times weekly 4

Critical Drug Interactions to Avoid

• Avoid concomitant use of clopidogrel with omeprazole or esomeprazole, as both significantly reduce the antiplatelet activity of clopidogrel 5
• Avoid strong CYP2C19 inducers as a precaution, as they might potentiate bleeding risk 5

Post-Fibrinolysis Catheterization Timing

• For successful fibrinolytic therapy, perform coronary angiography ideally within 24 hours, but not within the first 2-3 hours after fibrinolytic administration due to increased bleeding risk 3
• Very early catheterization (<2-3 hours) should be reserved for failed reperfusion or rescue PCI scenarios 3