What is the treatment for myocardial infarction (heart attack)?

Treatment of Myocardial Infarction

The treatment of myocardial infarction requires immediate evaluation within 10 minutes of arrival to the emergency department, with initial management including oxygen administration, sublingual nitroglycerin (unless contraindicated by hypotension or extreme heart rates), adequate analgesia with morphine, and 160-325mg of aspirin, followed by prompt reperfusion therapy for patients with ST-segment elevation. 1, 2

Initial Assessment and Management

• A 12-lead ECG should be performed immediately to identify ST-segment elevation (≥1 mV) in contiguous leads or new left bundle branch block, which indicates the need for reperfusion therapy 2, 1
• Initial evaluation should be completed within 10 minutes of arrival to the emergency department, with no more than 20 minutes elapsing before assessment 2, 1
• Immediate interventions upon arrival should include:
  • Oxygen administration via nasal prongs 2, 1
  • Sublingual nitroglycerin (unless systolic BP <90 mmHg or heart rate <50 or >100 bpm) 2, 1
  • Aspirin 160-325 mg orally 2, 1
  • Adequate analgesia with intravenous morphine or meperidine with concurrent antiemetics 2, 1
• Continuous cardiac monitoring should be established immediately 1

Reperfusion Therapy

• For patients with ST-segment elevation MI (STEMI) or new left bundle branch block, immediate reperfusion therapy is indicated 2
• The benefit of reperfusion therapy is time-dependent:
  • Greatest benefit occurs when initiated within 6 hours of symptom onset 2
  • Within the first hour: 35 lives saved per 1000 patients treated 2
  • Within 7-12 hours: 16 lives saved per 1000 patients treated 2
• Two main reperfusion strategies:
  • Thrombolytic therapy (fibrinolysis) 2
  • Primary percutaneous transluminal coronary angioplasty (PTCA) 2
• Primary PTCA may be performed as an alternative to thrombolytic therapy if it can be accomplished in a timely fashion by skilled personnel with access to emergency coronary artery bypass graft (CABG) surgery 2

Pharmacological Management

• Antiplatelet therapy:
  • Aspirin 160-325 mg should be administered immediately 2, 1
  • For STEMI patients, clopidogrel should be administered in conjunction with aspirin 3
• Analgesics:
  • Intravenous morphine (4-8 mg initially with additional 2 mg doses at 5-minute intervals) or diamorphine with concurrent antiemetics 1, 4
• Beta-blockers:
  • Early intravenous beta-blocker therapy followed by oral therapy should be initiated regardless of whether reperfusion therapy was given 2
• Nitrates:
  • Intravenous nitroglycerin can be titrated for ongoing chest pain 2
• Anticoagulation:
  • Heparin administration is beneficial for patients receiving thrombolytic therapy, particularly with tissue plasminogen activator 1
• ACE inhibitors:
  • Should be continued for an indefinite period after acute MI 2

Special Considerations

• Elderly patients (>65 years), those with low body weight (<70kg), hypertension, or receiving tissue plasminogen activator have increased risk of intracranial hemorrhage with thrombolytic therapy 2, 1
• Patients without chest pain (approximately 33% of MI cases) are at higher risk for delayed presentation, less aggressive treatment, and higher in-hospital mortality 5
• Diabetic patients require strict glycemic control, preferably with insulin-glucose infusion followed by multiple-dose insulin treatment 2
• For patients with large anterior MI or left ventricular mural thrombus, anticoagulation with heparin followed by oral anticoagulants for 3-6 months is recommended 2

Post-Acute Management

• Before hospital discharge, patients should undergo exercise testing to assess functional capacity and stratify risk 2
• Long-term management should include:
  • Continued aspirin therapy 2
  • Beta-blocker therapy 2
  • ACE inhibitor therapy 2
  • Diet low in saturated fat and cholesterol 2
  • Lipid-lowering therapy for LDL >130 mg/dL despite diet, with goal of <100 mg/dL 2
  • Smoking cessation 2
  • Cardiac rehabilitation program with regular exercise 2

Common Pitfalls to Avoid

• Delaying ECG assessment beyond 10 minutes of arrival 1
• Withholding aspirin administration while waiting for definitive diagnosis 1
• Administering thrombolytics to patients without ST-elevation or with contraindications 2, 1
• Failing to provide adequate analgesia, which can increase sympathetic activation 1
• Delaying reperfusion therapy, as benefit is time-dependent 2, 1
• Overlooking atypical presentations, especially in women, elderly, and diabetic patients 5
• Not educating patients about symptoms of MI and appropriate actions, which contributes to prehospital delay 2, 6