What is the immediate management for a patient presenting with myocardial infarction (MI)?

Immediate Management of Myocardial Infarction

Administer aspirin 160-325 mg orally (or IV if unable to swallow) immediately upon arrival, obtain a 12-lead ECG within 10 minutes, and proceed directly to primary percutaneous coronary intervention (PCI) if it can be performed within 90-120 minutes of first medical contact—otherwise initiate fibrinolytic therapy within 30 minutes. 1, 2, 3

Initial Assessment and Stabilization (First 10 Minutes)

Time-Critical Actions:

• Perform 12-lead ECG within 10 minutes of arrival to identify ST-segment elevation (≥1 mm in contiguous leads) or new left bundle branch block 2, 3, 4
• Establish continuous cardiac monitoring with defibrillation capacity immediately 2, 4
• Administer aspirin 160-325 mg orally (or IV if patient cannot swallow) without delay 1, 2, 3, 4
• Provide oxygen only if oxygen saturation is <90% or PaO₂ <60 mmHg—routine oxygen is contraindicated when SaO₂ ≥90% as it may increase myocardial injury 4

Immediate Pharmacological Management:

• Give sublingual nitroglycerin unless systolic blood pressure is <90 mmHg or heart rate is <50 or >100 bpm 4
• Administer morphine sulfate for adequate analgesia, though be aware this may delay onset of oral antiplatelet agents 1, 4
• Avoid nitrates completely in inferior STEMI with suspected right ventricular involvement due to risk of profound hypotension 4

Reperfusion Strategy Decision (Within 90-120 Minutes)

Primary PCI (Preferred Strategy):

• Primary PCI is the reperfusion strategy of choice when door-to-balloon time can be achieved within 90 minutes of first medical contact 1, 3, 4
• Transfer patients directly to the catheterization laboratory, bypassing the emergency department 1, 2
• Administer a potent P2Y12 inhibitor (prasugrel or ticagrelor) before or at the time of PCI—clopidogrel only if these are unavailable or contraindicated 1, 2
• For prasugrel: give 60 mg loading dose, then 10 mg daily; consider 5 mg daily maintenance in patients <60 kg due to increased bleeding risk 5
• Prasugrel is contraindicated in patients with prior TIA or stroke (6.5% stroke rate vs 1.2% with clopidogrel in this population) 5

Fibrinolytic Therapy (When PCI Delayed):

• Initiate fibrinolytic therapy if primary PCI cannot be performed within 120 minutes of STEMI diagnosis 1, 3
• Door-to-needle time must be ≤30 minutes 1, 3
• Use fibrin-specific agents: tenecteplase, alteplase, or reteplase 1
• Administer with aspirin, clopidogrel, and anticoagulation (enoxaparin IV followed by subcutaneous preferred over unfractionated heparin) 1
• Greatest benefit occurs within first 6 hours of symptom onset, saving 35 lives per 1,000 patients treated within the first hour 3

Post-Fibrinolysis Management:

• Transfer all patients to PCI-capable center immediately after fibrinolysis 1
• Perform rescue PCI immediately if fibrinolysis fails (<50% ST-segment resolution at 60-90 minutes) or with hemodynamic/electrical instability 1
• Perform routine angiography and PCI of infarct-related artery between 2-24 hours after successful fibrinolysis 1

Special Timing Considerations

Early Presenters (<3 Hours from Symptom Onset):

• If anticipated time from STEMI diagnosis to PCI is >120 minutes, immediate fibrinolysis is indicated 1
• Primary PCI remains preferred if achievable within 120 minutes 1

Late Presenters (12-48 Hours):

• Routine primary PCI strategy should be considered in all patients 1
• After 48 hours, routine PCI of totally occluded infarct-related artery is not recommended in asymptomatic stable patients 1

Ongoing Symptoms at Any Time:

• Primary PCI is indicated regardless of time from symptom onset if signs of ongoing ischemia, hemodynamic instability, or life-threatening arrhythmias are present 1

Additional Immediate Pharmacological Interventions

Anticoagulation:

• Fondaparinux is contraindicated for primary PCI 1
• Continue anticoagulation until revascularization or for duration of hospital stay up to 8 days 1

Beta-Blockers:

• Oral beta-blockers are indicated in patients with heart failure and/or LVEF <40% unless contraindicated 1
• Intravenous beta-blockers must be avoided in patients with hypotension, acute heart failure, AV block, or severe bradycardia 1

Statins:

• Start high-intensity statin therapy as early as possible 2

Management of Cardiac Rhythm Disturbances

Bradyarrhythmias:

• Have transcutaneous pacing capabilities immediately available 4
• For symptomatic or hemodynamically significant bradycardia, administer atropine 0.5-1.0 mg IV (may repeat to maximum of 3 mg) 4
• Monitor patients with inferior wall MI closely for conduction abnormalities and right ventricular involvement 4

Critical Pitfalls to Avoid

• Do not delay reperfusion therapy waiting for cardiac biomarker results when ECG shows ST-elevation or new LBBB 3
• Do not start prasugrel in patients likely to undergo urgent CABG; discontinue at least 7 days prior to surgery when possible 5
• Do not administer routine oxygen when SaO₂ ≥90% (Class III harm recommendation) 4
• Do not give excessive fluids in patients without right ventricular involvement as this may worsen left ventricular failure 4
• Do not send patients to physician offices—transport directly to hospitals with 24-hour emergency cardiac care and catheterization capabilities 3
• Do not use beta-blockers or calcium channel blockers in the setting of conduction abnormalities as they may worsen bradycardia or heart block 4

Post-Reperfusion Management

Dual Antiplatelet Therapy (DAPT):

• Continue aspirin (75-100 mg daily) plus ticagrelor or prasugrel (or clopidogrel if unavailable/contraindicated) for 12 months after PCI unless excessive bleeding risk 1, 2
• Add proton pump inhibitor in patients at high risk of gastrointestinal bleeding 1, 2

Routine Echocardiography:

• Perform during hospital stay to assess LV and RV function, detect mechanical complications, and exclude LV thrombus 1

ACE Inhibitors:

• Initiate within 24 hours in patients with heart failure, LV systolic dysfunction, diabetes, or anterior infarct 2