In a patient with acute myocardial infarction, what is the recommended immediate treatment protocol, including antiplatelet therapy (aspirin, clopidogrel or ticagrelor), anticoagulation (unfractionated heparin or low‑molecular‑weight heparin), supplemental oxygen, sublingual nitroglycerin, intravenous morphine, beta‑blocker (metoprolol), reperfusion strategy (primary percutaneous coronary intervention within 90 minutes or fibrinolytic therapy with alteplase), and early secondary‑prevention medications (high‑intensity statin, ACE inhibitor or ARB)?

Immediate Treatment Protocol for Acute Myocardial Infarction

In a patient with acute myocardial infarction, obtain a 12-lead ECG within 10 minutes, give aspirin 150–325 mg and choose primary PCI if it can be performed within 120 minutes (with prasugrel or ticagrelor plus unfractionated heparin), or immediately initiate fibrinolysis within 10 minutes (with clopidogrel and enoxaparin) if PCI will be delayed, while avoiding routine oxygen unless SpO₂ < 90%, using sublingual nitroglycerin and morphine only for symptom relief, and starting high-intensity statin and ACE inhibitor within 24 hours. 1

Initial Diagnosis and Stabilization (First 10 Minutes)

ECG and Monitoring

• Obtain and interpret a 12-lead ECG within 10 minutes of first medical contact—this is "time zero" for all reperfusion decisions 2, 1
• Initiate continuous ECG monitoring with defibrillator capacity immediately, as ventricular fibrillation is the most common early lethal arrhythmia 2, 1

Immediate Pharmacotherapy

• Aspirin 150–325 mg orally (chewed) or 250–500 mg intravenously if the patient cannot swallow—give this immediately at first contact 2, 1, 3
• Oxygen only if SpO₂ < 90%—routine oxygen administration in non-hypoxemic patients is contraindicated as it worsens myocardial injury 2, 1
• Sublingual nitroglycerin for ongoing chest pain, provided systolic blood pressure is ≥ 90 mmHg and heart rate is 50–100 bpm 2
• Intravenous morphine for pain relief if nitroglycerin is insufficient or contraindicated, though use cautiously as it may delay antiplatelet absorption 2, 4

Reperfusion Strategy Selection (Decision Point at 10 Minutes)

Primary PCI Pathway (Preferred if Door-to-Balloon ≤ 120 Minutes)

Primary PCI is the preferred reperfusion strategy when it can be performed within 120 minutes of STEMI diagnosis (or 90 minutes if presenting directly to a PCI-capable hospital). 2, 1

Pre-PCI Antithrombotic Regimen

• Prasugrel 60 mg loading dose OR ticagrelor 180 mg loading dose—these potent P2Y12 inhibitors are mandatory; clopidogrel is inferior and should only be used if the others are unavailable 2, 1, 5
• Unfractionated heparin 100 U/kg IV bolus (reduce to 60 U/kg if GPIIb/IIIa inhibitor is used)—this is first-line anticoagulation 2, 1
• Enoxaparin or bivalirudin are acceptable alternatives to unfractionated heparin 2, 1
• Fondaparinux is contraindicated for primary PCI 1

Procedural Standards

• Transfer the patient directly to the catheterization laboratory, bypassing the emergency department 2, 1
• Use radial artery access as the standard approach to minimize bleeding 2, 1
• Implant drug-eluting stents routinely 2, 1
• Do not perform routine thrombus aspiration or deferred stenting—these are contraindicated as they do not improve outcomes 2, 1

Fibrinolytic Pathway (When PCI Delay > 120 Minutes)

If primary PCI cannot be achieved within 120 minutes, initiate fibrinolytic therapy within 10 minutes of STEMI diagnosis in patients presenting ≤ 12 hours from symptom onset without contraindications. 2, 1, 6

Fibrinolytic Regimen

• Tenecteplase (preferred for single weight-adjusted bolus), alteplase, or reteplase—use a fibrin-specific agent 1, 6
• Continue aspirin (already given) 1, 6
• Clopidogrel 600 mg loading dose (300 mg if age < 75 years)—this is the only P2Y12 inhibitor indicated with fibrinolysis; do not use prasugrel or ticagrelor initially 2, 1, 6
• Enoxaparin: 30 mg IV bolus followed by 1 mg/kg subcutaneously every 12 hours (dose-adjusted for age ≥ 75 years and renal function), continued until revascularization or up to 8 days 1, 6
• Unfractionated heparin (weight-adjusted IV bolus then infusion) is an acceptable alternative if enoxaparin is unavailable 1, 6

Post-Fibrinolysis Management

• Transfer all patients to a PCI-capable center immediately—do not wait to assess reperfusion success 1, 6
• At 60–90 minutes after fibrinolysis, assess ST-segment resolution: ≥ 50% resolution indicates success, < 50% indicates failure 1, 6
• Immediate rescue PCI for failed fibrinolysis (< 50% ST-resolution), hemodynamic instability, cardiogenic shock, or recurrent ischemia 1, 6
• Routine angiography within 2–24 hours after successful fibrinolysis (pharmacoinvasive strategy)—do not delay beyond 24 hours 1, 6, 7
• Switch from clopidogrel to prasugrel or ticagrelor at the time of angiography/PCI 1, 6

Beta-Blocker Administration

• Oral metoprolol should be initiated in hemodynamically stable patients with heart failure or LVEF < 40% after stabilization 1
• Avoid intravenous beta-blockers in patients with hypotension (systolic BP < 90 mmHg), acute heart failure, severe bradycardia (< 50 bpm), or heart block 8
• If IV metoprolol is used in carefully selected stable patients, give three 5 mg IV boluses at 2-minute intervals, then start oral metoprolol 50 mg every 6 hours 15 minutes after the last IV dose 8

Early Secondary Prevention (Within 24 Hours)

High-Intensity Statin

• Atorvastatin 80 mg or rosuvastatin 40 mg daily—initiate early, targeting LDL-C < 1.8 mmol/L (≈ 70 mg/dL) 1

ACE Inhibitor or ARB

• 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) 9
• ACE inhibitors are particularly indicated in patients with heart failure, LV systolic dysfunction, diabetes, or anterior infarction 1, 9
• ARBs are an alternative if ACE inhibitors are not tolerated 1

Mineralocorticoid Receptor Antagonist

• Add spironolactone or eplerenone in patients with LVEF < 40% already on ACE inhibitor and beta-blocker, provided renal function and potassium are acceptable 1

Monitoring and Post-Reperfusion Care

• Monitor continuously for at least 24 hours after reperfusion to detect arrhythmias, heart failure, and mechanical complications 2, 1
• Perform routine transthoracic echocardiography during admission to assess LV/RV function, detect mechanical complications, and exclude LV thrombus 1

Dual Antiplatelet Therapy (DAPT) Maintenance

• Aspirin 75–100 mg daily indefinitely 1
• Prasugrel 10 mg daily OR ticagrelor 90 mg twice daily for 12 months after PCI unless life-threatening bleeding occurs 2, 1, 5
• Add a proton pump inhibitor in patients at high risk of gastrointestinal bleeding 1, 5

Special Clinical Scenarios

Cardiogenic Shock or Severe Heart Failure

• Immediate primary PCI regardless of time delay—this is an absolute indication even if > 120 minutes from diagnosis 2, 1
• Consider PCI of non-infarct-related arteries during the index procedure in cardiogenic shock 2, 1

Cardiac Arrest with ST-Elevation

• Immediate primary PCI in patients with return of spontaneous circulation and ST-elevation on post-resuscitation ECG 2, 1
• Initiate targeted temperature management (32–36°C for 24 hours) in unresponsive patients 1
• Pre-hospital cooling with large volumes of cold IV fluid is contraindicated 1

Contraindications to Fibrinolysis

• Immediate primary PCI regardless of delay in patients with active bleeding, recent stroke, recent major surgery, or aortic dissection 1

Critical Pitfalls to Avoid

• Do not use prasugrel or ticagrelor with initial fibrinolysis—clopidogrel is specifically indicated, with transition to potent agents at PCI 1, 6
• Do not give routine oxygen to non-hypoxemic patients—it worsens outcomes 2, 1
• Do not delay transfer after fibrinolysis—all patients require angiography regardless of apparent success 1, 6
• Do not miss the 2–24 hour window for routine angiography after successful fibrinolysis 1, 6
• Do not perform routine thrombus aspiration or deferred stenting—these are contraindicated 2, 1
• Do not use fondaparinux for primary PCI—it is contraindicated 1
• Do not give IV beta-blockers to patients with hypotension, acute heart failure, or bradycardia 8