What is the recommended acute management for an adult patient with suspected acute myocardial infarction?

Acute Myocardial Infarction Management

For an adult with suspected acute MI, immediately administer aspirin 160-325 mg orally, obtain a 12-lead ECG within 10 minutes, initiate continuous cardiac monitoring, and proceed directly to primary PCI if ST-elevation is present and available within 90 minutes—otherwise administer fibrinolytic therapy within 30 minutes if symptoms are <12 hours and no contraindications exist. 1, 2, 3

Immediate Actions (First 10 Minutes)

Time-critical assessment must be completed within 10 minutes of arrival, with total evaluation not exceeding 20 minutes. 2, 3

Diagnostic Steps

• Obtain 12-lead ECG immediately to identify ST-segment elevation ≥1 mm in contiguous leads or new left bundle branch block 1, 2, 3
• Initiate continuous cardiac monitoring to detect life-threatening arrhythmias 1, 3
• Obtain right-sided precordial leads (V3R-V4R) in all patients with inferior MI, as ST elevation ≥0.1 mV in V4R is highly specific for right ventricular infarction 4

Initial Pharmacotherapy

• Aspirin 160-325 mg orally immediately (or IV if unable to swallow), continued indefinitely 1, 3, 5
• Sublingual nitroglycerin (up to 3 doses, 5 minutes apart) UNLESS systolic BP <90 mmHg, heart rate <50 or >100 bpm, or suspected right ventricular infarction 2, 3
• Titrated IV morphine for pain control, though be aware this delays oral antiplatelet absorption 3
• Oxygen only if SaO₂ <90% or PaO₂ <60 mmHg—routine oxygen is contraindicated when SaO₂ ≥90% due to potential harm from hyperoxia 3

Reperfusion Strategy (Based on ECG Findings)

ST-Elevation MI or New LBBB

Primary PCI is the preferred reperfusion strategy when available within 90 minutes of first medical contact. 1, 2, 3

Primary PCI Pathway

• Door-to-balloon time ≤90 minutes 2
• Administer potent P2Y12 inhibitor (ticagrelor or prasugrel preferred over clopidogrel) before or at time of PCI 1, 3, 6
• High-dose IV heparin during procedure 1
• Transfer immediately to PCI-capable center if not available on-site, particularly for high-risk patients with anterior MI, shock, pulmonary congestion, heart rate >100 bpm, or systolic BP <100 mmHg 2

Fibrinolytic Therapy (When PCI Cannot Be Performed Within 120 Minutes)

• Door-to-needle time ≤30 minutes 2
• Use fibrin-specific agent: tenecteplase, alteplase, or reteplase 1
• Administer within 12 hours of symptom onset—greatest benefit within first 6 hours (35 lives saved per 1,000 patients treated within first hour vs 16 lives saved per 1,000 patients treated between 7-12 hours) 2
• Anticoagulation with enoxaparin IV followed by subcutaneous (preferred over unfractionated heparin) until revascularization or up to 8 days 1
• Transfer to PCI-capable center immediately after fibrinolysis 1
• Angiography and PCI of infarct-related artery between 2-24 hours after successful fibrinolysis 1, 2
• Rescue PCI immediately if fibrinolysis fails (<50% ST-segment resolution at 60-90 minutes) or hemodynamic/electrical instability develops 1

First 24 Hours Management

Continuous Monitoring and Medications

• IV beta-blocker followed by oral therapy unless contraindicated (hypotension, acute heart failure, AV block, severe bradycardia)—reduces morbidity and mortality regardless of reperfusion therapy 1
• IV nitroglycerin for 24-48 hours in patients without hypotension, bradycardia, or excessive tachycardia 1
• Dual antiplatelet therapy (aspirin plus P2Y12 inhibitor) for 12 months unless excessive bleeding risk 1, 6
• High-intensity statin therapy initiated as early as possible 1

Hemodynamic Support

• Atropine 0.5-1.0 mg IV (may repeat to maximum 3 mg) for symptomatic bradycardia 3
• Transcutaneous pacing capabilities immediately available 3

Special Consideration: Right Ventricular Infarction

Suspect RV infarction in any inferior MI patient with hypotension, elevated jugular venous pressure, and clear lung fields. 4

Critical Management Differences

• Aggressive normal saline administration: 500 mL bolus initially, followed by 500 mL/hour infusion 4
• Target pulmonary artery wedge pressure 14-18 mmHg 4
• NEVER administer diuretics or nitrates—these cause severe hypotension by reducing right-sided filling pressure required for cardiac output 4
• Dobutamine for refractory hypotension after adequate fluid resuscitation (typically 1-2 liters) 4
• Consider pulmonary artery catheter for hemodynamic monitoring when diagnosis unclear or patient fails initial fluid resuscitation 4

Complications Management

Recurrent Ischemia

• IV nitroglycerin, analgesics, and antithrombotic medications (aspirin, heparin) 1
• Coronary angiography with revascularization should be considered 1

Heart Failure

• IV furosemide and afterload-reducing agent 1
• ACE inhibitor for patients with LVEF <40% or heart failure 1

Cardiogenic Shock

• Intra-aortic balloon pump and emergency coronary angiography followed by PTCA or CABG 1
• Early reperfusion reduces mortality from >85% to approximately 60% 4

Pericarditis

• High-dose aspirin 650 mg every 4-6 hours 1

Long-Term Management (Post-Discharge)

• Aspirin, beta-blocker, and ACE inhibitor indefinitely 1
• LDL-C goal <1.8 mmol/L (70 mg/dL) or ≥50% reduction if baseline 1.8-3.5 mmol/L 1
• Proton pump inhibitor for patients at high gastrointestinal bleeding risk on dual antiplatelet therapy 1, 5
• Cardiac rehabilitation program participation 1
• Exercise testing (submaximal at 4-7 days or symptom-limited at 10-14 days) before discharge to assess functional capacity and stratify risk 1
• Echocardiography during hospital stay to assess LV/RV function, detect mechanical complications, and exclude LV thrombus 1

Critical Pitfalls to Avoid

• Never delay reperfusion therapy waiting for cardiac biomarkers when ECG shows ST-elevation or new LBBB 2, 3
• Never give nitrates in suspected RV infarction regardless of chest pain 4, 3
• Never reflexively administer diuretics for elevated JVP in inferior MI without excluding RV involvement 4
• Avoid calcium channel blockers—not shown to reduce mortality and may be harmful 1
• Avoid routine catheterization within 2-3 hours of fibrinolytic administration unless rescue PCI needed due to increased bleeding risk 2
• Do not send patient to physician's office—transport directly to hospital with 24-hour emergency cardiac care capability 2
• Avoid IV beta-blockers in patients with hypotension, acute heart failure, low-output state, or increased cardiogenic shock risk 1, 3