Management and Treatment of Myocardial Infarction (Heart Attack)
The management of myocardial infarction requires immediate reperfusion therapy for patients with ST-segment elevation, with thrombolytic treatment ideally administered within 90 minutes of the patient alerting medical services to maximize survival benefits. 1
Initial Assessment and Management
- Evaluation should be completed within 10 minutes (maximum 20 minutes) of arrival to the emergency department 1, 2
- Immediate 12-lead ECG to identify ST-segment elevation (≥1mV) in contiguous leads or new left bundle branch block, which indicates need for reperfusion therapy 1, 2
- Initial interventions upon arrival should include:
- Oxygen administration via nasal prongs (especially for patients with hypoxemia) 2
- Sublingual nitroglycerin (unless systolic BP <90mmHg or heart rate <50 or >100bpm) 1, 2
- Aspirin 160-325mg orally (chewable for faster absorption) 1, 2
- Adequate analgesia with intravenous morphine or diamorphine with concurrent antiemetics 1, 2
Reperfusion Strategy
- Patients with ST-segment elevation or new LBBB should undergo immediate reperfusion therapy 1
- Two main reperfusion options:
- Thrombolytic therapy (fibrinolysis): Most beneficial when given within the first hour (35 lives saved per 1000 patients treated) compared to 7-12 hours (16 lives saved per 1000) 1, 2
- Primary percutaneous transluminal coronary angioplasty (PTCA): Alternative to thrombolysis if performed in a timely fashion by skilled personnel with access to emergency CABG 1, 2
- Time is critical - the "call to needle time" should ideally be within 90 minutes 1, 3
Pharmacological Management
- Aspirin: 160-325mg immediately and continued indefinitely 1, 2
- Nitroglycerin: Sublingual for chest pain relief 1
- Opioid analgesics: IV morphine (4-8mg initially with additional 2mg doses) or diamorphine with antiemetics 1, 2
- Beta-blockers: Metoprolol can be initiated as soon as the patient's clinical condition allows 4
- Initial IV administration: Three bolus injections of 5mg at 2-minute intervals
- Followed by oral therapy: 50mg every 6 hours, then 100mg twice daily maintenance
- ACE inhibitors: Lisinopril has been shown to reduce mortality when initiated within 24 hours of symptom onset 5
- Initial dose: 5mg within 24 hours, 5mg after 24 hours, then 10mg daily
- Reduced dose (2.5mg) for patients with systolic BP <120mmHg
Monitoring and Further Care
- Continuous cardiac monitoring should be established immediately 2
- Emergency resuscitation equipment, including a defibrillator, must be immediately available 1
- Monitor for complications including arrhythmias, which are most common in the first 24 hours 2, 6
- Serial ECGs and measurements of serum cardiac markers to confirm diagnosis and monitor progress 2, 7
- Echocardiography to assess left ventricular function and detect complications 8
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 1, 9
- Women ≥65 years have longer delay times from symptom onset to hospital arrival (median 266 minutes vs 148 minutes in younger women), potentially due to atypical presentation 9
- For patients with large anterior MI or LV mural thrombus, early administration of intravenous heparin may reduce stroke risk 2
Common Pitfalls to Avoid
- Delaying ECG assessment beyond 10 minutes of arrival 1, 2
- Withholding aspirin administration while waiting for definitive diagnosis 2
- Administering thrombolytics to patients without ST-elevation or with contraindications 1
- Failing to provide adequate analgesia, which can increase sympathetic activation and worsen cardiac workload 1, 2
- Delaying reperfusion therapy, as mortality increases significantly when FMC to PCI time exceeds 90 minutes (5.6% vs 1.4% mortality) 3