What is the immediate management of an ischemic (myocardial infarction) heart attack?

Immediate Management of Ischemic Heart Attack

For a suspected myocardial infarction, immediately obtain a 12-lead ECG within 10 minutes, administer aspirin 160-325 mg orally (chewed), provide sublingual nitroglycerin (unless systolic BP <90 mmHg), give supplemental oxygen if hypoxemic, establish continuous cardiac monitoring, and initiate reperfusion therapy within 30 minutes for ST-elevation MI. 1, 2

Time-Critical Initial Actions (First 10 Minutes)

The emergency department must complete these steps within 10 minutes of patient arrival: 3, 1

• Obtain 12-lead ECG immediately to identify ST-segment elevation ≥1 mm in contiguous leads or new left bundle branch block, which determines reperfusion strategy 1, 2
• Administer aspirin 160-325 mg orally (chewable or water-soluble formulation for faster absorption) - this reduces mortality and should never be delayed 1, 2, 4
• Establish continuous cardiac monitoring with defibrillator immediately available, as ventricular fibrillation risk is highest in the first hour 3, 2
• Assess vital signs and oxygen saturation - provide supplemental oxygen only if SaO₂ <90% or patient is breathless/has heart failure 3, 1, 2

Immediate Pharmacological Management

Administer these medications in the emergency department:

• Sublingual nitroglycerin unless systolic BP <90 mmHg, heart rate <50 or >100 bpm, or marked bradycardia/tachycardia present 3, 1, 2
• Intravenous morphine 4-8 mg for pain relief, with additional 2 mg doses at 5-minute intervals until pain controlled, along with antiemetic 2, 4
  • Caveat: Morphine may delay oral antiplatelet absorption, but pain control is essential to reduce sympathetic activation 1, 2

ECG-Based Reperfusion Decision Algorithm

The treatment pathway diverges based on ECG findings: 3

For ST-Elevation MI or New LBBB:

Primary PCI is the preferred reperfusion strategy if available within 90 minutes of first medical contact (door-to-balloon time ≤90 minutes): 1, 2

• Administer P2Y12 inhibitor (ticagrelor or prasugrel preferred over clopidogrel) 1
• Transport high-risk patients (shock, pulmonary edema, heart rate >100 bpm, systolic BP <100 mmHg) directly to facilities capable of cardiac catheterization and revascularization 3

If PCI cannot be performed within 120 minutes, initiate fibrinolytic therapy with door-to-needle time ≤30 minutes: 3, 1, 2

• Greatest benefit occurs within first hour (35 lives saved per 1000 patients) versus 7-12 hours (16 lives saved per 1000) 2
• Thrombolytic agents include tissue plasminogen activator, streptokinase, or urokinase administered within 3 hours of symptom onset 4
• Administer heparin concurrently, particularly with tissue plasminogen activator 2

For Non-ST-Elevation MI:

Do not administer fibrinolytic therapy - these patients require different therapeutic approach focused on antiplatelet therapy, anticoagulation, and risk stratification for possible catheterization 3

Beta-Blocker Administration

For hemodynamically stable patients, initiate intravenous metoprolol tartrate: 5

• Give three bolus injections of 5 mg each at approximately 2-minute intervals during the early phase after hemodynamic stabilization 5
• Monitor blood pressure, heart rate, and ECG continuously during IV administration 5
• Begin oral metoprolol 50 mg every 6 hours, 15 minutes after last IV dose, continued for 48 hours, then 100 mg twice daily 5
• Contraindications: Avoid in patients with severe intolerance, hypotension, or bradycardia 5

Critical Time Targets

These time benchmarks directly impact mortality and must be met: 3, 1, 2

• ECG completion: ≤10 minutes from arrival 3, 1
• Total initial assessment: ≤20 minutes 1, 2
• Door-to-needle time (fibrinolysis): ≤30 minutes 3, 1
• Door-to-balloon time (primary PCI): ≤90 minutes 1
• Call-to-needle time (prehospital to treatment): 60-90 minutes maximum 2

Common Pitfalls to Avoid

These errors significantly worsen outcomes:

• Delaying aspirin administration while waiting for definitive diagnosis - aspirin should be given immediately on suspicion 1, 2
• Withholding oxygen from all patients - only administer if hypoxemic (SaO₂ <90%), as routine oxygen may worsen outcomes 3, 1
• Administering nitroglycerin to hypotensive patients - this can precipitate cardiovascular collapse and worsen myocardial ischemia 3
• Giving thrombolytics to non-ST-elevation MI - this provides no benefit and increases bleeding risk 3
• Exceeding 10-minute ECG time - every minute of delay reduces reperfusion therapy effectiveness 3, 1
• Failing to recognize atypical presentations - epigastric pain, indigestion, arm/jaw pain, dyspnea, and diaphoresis without chest pain can all represent MI 3, 1

High-Risk Patient Identification

Immediately triage these patients to tertiary centers capable of catheterization: 3

• Cardiogenic shock
• Pulmonary edema (rales greater than halfway up lung fields)
• Heart rate >100 bpm with systolic BP <100 mmHg
• Ongoing chest discomfort >20 minutes but <12 hours
• Signs of large anterior MI or left ventricular mural thrombus (consider early IV heparin to reduce stroke risk) 2

Special Population Considerations

Elderly patients (>65 years), low body weight (<70 kg), hypertensive patients, and those receiving tissue plasminogen activator have increased intracranial hemorrhage risk with thrombolytic therapy - carefully assess bleeding contraindications 2