What is the initial treatment for a patient with myocardial infarction (heart attack)?

Initial Treatment for Myocardial Infarction

Administer aspirin 160-325 mg orally immediately upon suspicion of myocardial infarction—this is the single most important pharmacologic intervention and should not be delayed for any reason. 1, 2

Immediate Actions (First 10 Minutes)

Critical Medications

• Aspirin 160-325 mg orally must be given without delay, even before ECG confirmation 1, 2
• Sublingual nitroglycerin 0.4 mg should be administered unless systolic blood pressure is <90 mmHg or heart rate is <50 or >100 bpm 3, 1, 2
• Intravenous morphine or meperidine for pain control, titrated to effect, though be aware this may delay oral antiplatelet absorption 1, 2

Diagnostic and Monitoring

• 12-lead ECG within 10 minutes of arrival to identify ST-segment elevation or new left bundle branch block 1, 4, 2
• Continuous cardiac monitoring initiated immediately to detect life-threatening arrhythmias 1
• Oxygen only if SaO₂ <90%—routine oxygen is not recommended and may be harmful when saturation is adequate 1, 2

Reperfusion Strategy (Time-Critical Decision)

Primary PCI (Preferred)

• Primary PCI is the preferred reperfusion strategy if available within 90 minutes of first medical contact, with door-to-balloon time ≤90 minutes 1, 4
• Transport directly to a hospital with 24-hour PCI facilities if transport time is reasonable 4

Fibrinolytic Therapy (Alternative)

• Initiate fibrinolytic therapy if PCI cannot be performed within 120 minutes, with door-to-needle time ≤30 minutes 1
• Target call-to-needle time of 90 minutes from alerting medical services 1
• In rural settings, protocols should allow initiation of thrombolytic therapy before transfer to tertiary centers 3, 2

Time-Dependent Benefit

The evidence strongly supports the critical importance of treatment timing:

• Within first hour: 65 lives saved per 1,000 patients treated 1, 4
• Within 2-3 hours: 27 lives saved per 1,000 patients 3
• Within 4-6 hours: 25 lives saved per 1,000 patients 3

Additional Pharmacotherapy

Antiplatelet Therapy

• P2Y12 inhibitor (ticagrelor or prasugrel preferred over clopidogrel) should be administered immediately 1, 2
• The CURE study demonstrated a 20% relative risk reduction in cardiovascular death, MI, or stroke with clopidogrel plus aspirin versus aspirin alone 5

Supportive Medications

• Intravenous nitroglycerin allows for more precise minute-to-minute control than sublingual or transdermal formulations 3
• Antiemetic with diamorphine for adequate analgesia 3
• Atropine 0.5-1.0 mg IV for symptomatic bradycardia (may repeat to maximum 3 mg) 2

Critical Pitfalls to Avoid

Oxygen Administration

Do not administer routine oxygen to patients with SaO₂ ≥90%—this carries a Class III (harm) recommendation, as hyperoxia may increase myocardial injury 2. Oxygen is indicated only when SaO₂ <90% or PaO₂ <60 mmHg 1, 2.

Nitroglycerin Contraindications

Avoid nitrates in inferior STEMI with suspected right ventricular involvement—this can cause profound hypotension 2. Also avoid if systolic BP <90 mmHg or marked bradycardia/tachycardia is present 3, 1.

Morphine Considerations

While morphine provides effective analgesia, it is associated with slower uptake and delayed onset of oral antiplatelet agents, potentially leading to early treatment failure 2. Balance pain relief against this consideration.

Administrative Delays

Delays related to insurance coverage or prolonged attempts to contact private physicians are inappropriate and must not be allowed to occur 3. When diagnosis is classic for acute MI, appropriately trained emergency department physicians should initiate treatment immediately 3.

Organizational Requirements

Emergency Response System

• All emergency vehicles must contain a defibrillator with staff trained in its use 1, 4
• Direct communication between ambulance and admitting hospital should be established 3, 1
• Hospitals should implement "fast tracking" of patients with obvious MI 3, 1

Triage Decisions

Critically ill patients (cardiac arrest, repetitive ventricular tachyarrhythmias, severe bradycardia, or shock) should be taken to a hospital with cardiac catheterization and cardiac surgery facilities, even if this requires slightly longer transport time 3, 4.