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

Immediate Treatment of Myocardial Infarction

Administer aspirin 160-325 mg orally (or IV if unable to swallow) immediately upon arrival, before ECG confirmation, as this reduces 35-day mortality by 21% when combined with reperfusion therapy. 1, 2

Initial Stabilization (First 10-20 Minutes)

Immediate Medications

• Aspirin 160-325 mg should be given immediately to all patients without contraindications—do not wait for ECG confirmation 1, 2
• Oxygen via nasal prongs only if oxygen saturation is <90%—avoid routine oxygen in non-hypoxemic patients as hyperoxia may increase myocardial injury 1, 2
• Sublingual nitroglycerin unless systolic BP <90 mmHg, heart rate <50 or >100 bpm, or suspected right ventricular infarction (where it causes profound hypotension) 1, 2
• Morphine sulfate or meperidine for adequate analgesia 1, 2

Diagnostic Assessment

• Obtain 12-lead ECG within 10 minutes (maximum 20 minutes) to identify ST-segment elevation ≥1 mV in contiguous leads or new left bundle branch block 1, 3
• For inferior MI, obtain V4R lead early as ST elevation may resolve within 10 hours in right ventricular infarction 2, 4
• Establish continuous cardiac monitoring with defibrillation capacity 3

Reperfusion Strategy Decision

Primary PCI (Preferred)

Primary percutaneous coronary intervention is the preferred reperfusion strategy when it can be performed within 120 minutes of STEMI diagnosis by experienced operators. 1, 2, 3

• Transfer patients directly to catheterization laboratory, bypassing emergency department when possible 1, 3
• Administer a potent P2Y12 inhibitor (prasugrel or ticagrelor, or clopidogrel if unavailable/contraindicated) before or at the time of PCI, maintained for 12 months 1, 2, 3
• Give unfractionated heparin as weight-adjusted IV bolus for anticoagulation during primary PCI 1, 4

Fibrinolytic Therapy (If PCI Delayed)

If primary PCI cannot be performed within 120 minutes, initiate fibrinolytic therapy immediately if presenting within 12 hours of symptom onset and no contraindications exist. 1, 2

• Use fibrin-specific agents (tenecteplase, alteplase, or reteplase)—reduce tenecteplase dose by 50% in patients ≥75 years to minimize stroke risk 1, 2
• Administer clopidogrel in addition to aspirin 1
• Give enoxaparin IV followed by subcutaneous (preferred over unfractionated heparin) for anticoagulation 1, 4
• Transfer to PCI-capable center immediately after fibrinolysis for angiography between 2-24 hours 1
• Perform rescue PCI immediately if fibrinolysis fails (<50% ST-segment resolution at 60-90 minutes) or hemodynamic/electrical instability develops 1

Additional Pharmacotherapy (First 24 Hours)

Beta-Blockers

• Oral beta-blockers are indicated in hemodynamically stable patients with heart failure and/or LVEF <40% 1, 3
• Avoid IV beta-blockers in patients with hypotension, acute heart failure, AV block, or severe bradycardia 1
• For early IV administration in stable patients: metoprolol 5 mg IV every 2 minutes for 3 doses (total 15 mg), then 50 mg orally every 6 hours starting 15 minutes after last IV dose 5

ACE Inhibitors

• Initiate ACE inhibitors within 24 hours in patients with heart failure, LVEF <40%, diabetes, or anterior infarction 2, 3, 4
• Start lisinopril 5 mg within 24 hours, then 5 mg after 24 hours, then 10 mg daily (reduce to 2.5 mg if systolic BP <120 mmHg at baseline) 6

Statins

• Start high-intensity statin therapy as soon as possible and maintain long-term 1, 2, 3, 4

Nitroglycerin

• Use IV nitroglycerin for 24-48 hours in patients with heart failure, large anterior MI, persistent ischemia, or hypertension 2
• Completely avoid nitroglycerin in right ventricular infarction due to risk of profound hypotension 2, 4

Special Consideration: Right Ventricular Infarction

Up to 50% of inferior MIs involve right ventricular infarction, requiring specific management modifications. 2, 4

• Obtain V4R lead early as ST elevation may resolve within 10 hours 2, 4
• Maintain right ventricular preload with IV saline boluses for hypotension 2, 4
• Avoid all nitrates completely—they cause profound hypotension in RV infarction 2, 4

Maintenance Therapy (After 24 Hours)

Dual Antiplatelet Therapy

• Continue aspirin 75-100 mg daily indefinitely 1, 4
• Maintain dual antiplatelet therapy for 12 months after PCI unless excessive bleeding risk 1, 2, 3, 4
• Add proton pump inhibitor in patients at high risk of gastrointestinal bleeding 1, 3

Long-Term Medications

• Continue beta-blockers in patients with heart failure/LVEF <40% 1, 3, 4
• Continue ACE inhibitors indefinitely 3, 4
• Continue high-intensity statins long-term 1, 3, 4

Critical Pitfalls to Avoid

• Do not give thrombolytics to non-STEMI patients—no benefit and increased bleeding risk 2
• Do not combine fibrinolysis with planned immediate PCI—this increases mortality and adverse outcomes 2
• Do not delay aspirin—give immediately, not after ECG confirmation 2
• Do not use routine oxygen—only if saturation <90% 2
• Do not use fondaparinux for primary PCI 1
• Do not perform routine PCI of occluded infarct-related artery >48 hours after STEMI onset in asymptomatic patients 1

Post-Reperfusion Assessment

• Perform routine echocardiography during hospitalization to assess LV and RV function, detect mechanical complications, and exclude LV thrombus 1, 3
• Initiate cardiac rehabilitation program and provide smoking cessation support with nicotine replacement, varenicline, or bupropion 1, 4