What is the treatment for myocardial infarction?

Myocardial Infarction Treatment

The treatment of myocardial infarction requires immediate administration of aspirin (162-325 mg chewed), pain control with morphine, oxygen therapy if needed, and urgent reperfusion therapy with either primary percutaneous coronary intervention (PCI) or fibrinolytic therapy, followed by comprehensive pharmacological management including antiplatelet therapy, beta-blockers, ACE inhibitors, and statins. 1

Initial Management (First Hours)

Immediate Interventions

• Obtain 12-lead ECG within 10 minutes of first medical contact 1
• Establish ECG monitoring with defibrillator capacity immediately 1
• Administer:
  • Aspirin 162-325 mg (chewed, non-enteric coated) 2, 1
  • Sublingual nitroglycerin (0.4 mg every 5 minutes, up to three doses) 2
  • Morphine sulfate for pain (2-4 mg IV, with 2-8 mg IV every 5-15 minutes as needed) 2
  • Consider IV nitroglycerin if no contraindications (hypotension, bradycardia, PDE inhibitor use) 2

Reperfusion Strategy

• Primary PCI is the preferred reperfusion strategy for all STEMI patients presenting within 12 hours of symptom onset 1
• If primary PCI cannot be performed within 120 minutes of first medical contact, administer fibrinolytic therapy within 12 hours of symptom onset 1
• For patients receiving fibrinolytic therapy, continue intravenous heparin for an additional 48 hours 1

Antithrombotic Therapy

• Loading doses of antithrombotic therapy:
  • P2Y12 inhibitor (preferably prasugrel 60 mg or ticagrelor 180 mg) 1
  • Anticoagulation with unfractionated heparin (weight-adjusted IV bolus followed by infusion) 1

Hospital Management

Pharmacological Therapy

• Beta-blockers:

  • For STEMI patients, intravenous beta-blocker therapy is reasonable to manage hypertension if no contraindications 2
  • For patients with definite MI, metoprolol tartrate can be initiated with three bolus injections of 5 mg IV at 2-minute intervals, followed by oral therapy (50 mg every 6 hours) 3
  • Daily oral beta-blocker therapy should be initiated within 24 hours for hemodynamically stable patients 2

• ACE inhibitors:

  • Start in patients with LVEF <40% and/or heart failure 1
  • Add mineralocorticoid receptor antagonist (MRA) in patients with heart failure and LVEF <40% with no severe renal failure or hyperkalemia 1

• Statins:

  • High-intensity statin therapy with goal LDL <70 mg/dL or ≥50% reduction 1

Management of Complications

• Heart failure: Administer diuretic (usually IV furosemide) and afterload-reducing agent 2
• Cardiogenic shock: Consider intra-aortic balloon pump and emergency coronary angiography, followed by PCI or CABG 2
• Right ventricular infarction: Provide vigorous intravascular volume expansion with normal saline and inotropic agents if hypotension persists 2
• Recurrent chest pain due to pericarditis: High-dose aspirin (650 mg every 4-6 hours) 2
• Recurrent ischemic chest pain: IV nitroglycerin, analgesics, and antithrombotic medications 2

Long-term Management

Ongoing Pharmacotherapy

• Continue aspirin 75-100 mg daily indefinitely 1
• Continue P2Y12 inhibitor for 12 months as part of dual antiplatelet therapy (DAPT) 1
• Continue beta-blockers, especially in patients with heart failure or LVEF <40% 1
• Continue ACE inhibitors (or ARBs if intolerant) in appropriate patients 1
• Maintain high-intensity statin therapy 1

Monitoring and Follow-up

• Perform echocardiography to assess LV and RV function, detect mechanical complications, and exclude LV thrombus 1
• Perform standard exercise testing (submaximal at 4-7 days or symptom-limited at 10-14 days) 2
• Participate in cardiac rehabilitation program 1

Important Considerations

Aspirin Dosing

While both 162 mg and 325 mg aspirin doses are recommended in guidelines, studies suggest that 162 mg may be as effective as 325 mg with potentially less bleeding risk 4, 5. However, the most appropriate dose for both primary and secondary prevention of stroke and MI appears to be 160 mg/day 6.

Beta-Blocker Considerations

Routine use of intravenous beta-blocker therapy in the acute phase of STEMI is not recommended due to increased risk of cardiogenic shock, but it is reasonable to use IV beta-blockers to manage hypertension in patients without contraindications 2.

Medications to Avoid

• NSAIDs (except aspirin) should not be administered during hospitalization for STEMI due to increased risk of mortality, reinfarction, hypertension, heart failure, and myocardial rupture 1
• Avoid calcium channel blockers as they have not been shown to reduce mortality and may be harmful in certain patients 1
• Avoid fondaparinux for primary PCI due to risk of catheter thrombosis 1

By following this comprehensive approach to MI management, focusing on rapid reperfusion and evidence-based pharmacotherapy, patient outcomes including mortality, morbidity, and quality of life can be significantly improved.