What is the recommended treatment for myocardial infarction (MI)?

Treatment of Myocardial Infarction

Primary percutaneous coronary intervention (PCI) is the preferred reperfusion strategy for STEMI when it can be performed by an experienced team within 120 minutes of diagnosis; if this timeframe cannot be met, immediate fibrinolytic therapy should be initiated. 1, 2, 3

Immediate Management at First Medical Contact

Diagnostic Assessment:

• Obtain 12-lead ECG within 10 minutes of first medical contact 1, 2
• Initiate continuous ECG monitoring with defibrillator capacity immediately 1, 2, 3
• Do NOT administer routine oxygen unless oxygen saturation is <90% 1, 2

Initial Pharmacotherapy:

• Aspirin: Administer 150-325 mg chewable (or 250-500 mg IV if unable to swallow) as soon as possible 1, 2, 3
• P2Y12 Inhibitor: Give prasugrel or ticagrelor (preferred), or clopidogrel if these are unavailable or contraindicated, before or at the time of PCI 1, 2

Primary PCI Strategy (Preferred When Available Within 120 Minutes)

Procedural Approach:

• Transfer patients directly to catheterization laboratory, bypassing emergency department 1, 2
• Use radial access as standard approach 2
• Implant drug-eluting stents as standard of care 2
• Do NOT perform routine thrombus aspiration or deferred stenting 2

Periprocedural Anticoagulation:

• Unfractionated heparin: 100 U/kg IV bolus (60 U/kg if GPIIb/IIIa inhibitors used) 2
• Fondaparinux is contraindicated for primary PCI 1, 2

Dual Antiplatelet Therapy:

• Continue aspirin plus potent P2Y12 inhibitor (prasugrel or ticagrelor preferred over clopidogrel) for 12 months unless excessive bleeding risk 1, 2

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

The European Society of Cardiology emphasizes that fibrinolytic therapy must be initiated as soon as possible, preferably in the pre-hospital setting, when primary PCI is not available within the critical 120-minute window. 1, 2, 3

Medication Sequence:

1. Aspirin: 150-325 mg oral or 250-500 mg IV 1, 3
2. Clopidogrel: 300 mg loading dose (75 mg if age >75 years) 1, 3
3. Anticoagulation: Enoxaparin 30 mg IV bolus followed by 1 mg/kg subcutaneous every 12 hours (preferred over UFH), or UFH as weight-adjusted IV bolus followed by infusion 1, 3
4. Fibrin-specific agent: Tenecteplase (30-50 mg weight-adjusted single bolus), alteplase, or reteplase 1, 2, 3

Critical Dosing Adjustment:

• For patients ≥75 years: Reduce tenecteplase dose by 50% to minimize stroke risk 2, 3

Post-Fibrinolysis Management:

• Continue anticoagulation until revascularization or for duration of hospital stay (up to 8 days) 1, 3
• Transfer ALL patients to PCI-capable center immediately after fibrinolysis 1, 3
• Perform angiography and PCI of infarct-related artery between 2-24 hours after successful fibrinolysis 1
• Rescue PCI is mandatory immediately if fibrinolysis fails (<50% ST-segment resolution at 60-90 minutes) or with hemodynamic/electrical instability 1

In-Hospital Management

Mandatory Assessments:

• Routine echocardiography to assess LV/RV function, detect mechanical complications, and exclude LV thrombus 1, 2

Medical Therapy Initiation:

• High-intensity statin: Start immediately and continue long-term, targeting LDL-C <1.8 mmol/L (70 mg/dL) or ≥50% reduction if baseline 1.8-3.5 mmol/L 1, 2, 3
• ACE inhibitor: Start within 24 hours in patients with heart failure, LVEF <40%, diabetes, or anterior infarct 1, 2
• Beta-blocker: Oral therapy for patients with heart failure and/or LVEF <40% (avoid IV beta-blockers in hypotension, acute heart failure, AV block, or severe bradycardia) 1, 2
• Mineralocorticoid receptor antagonist (MRA): Add for patients with LVEF <40% and heart failure or diabetes who are already on ACE inhibitor and beta-blocker, provided no renal failure or hyperkalemia 1, 2

Special Populations and Situations

Cardiogenic Shock:

• Immediate angiography and PCI regardless of time from symptom onset 1, 2

Cardiac Arrest:

• Primary PCI strategy if post-resuscitation ECG shows ST-elevation 1, 2
• Targeted temperature management for patients remaining unresponsive 1

Late Presentation:

• Do NOT perform routine PCI of occluded infarct-related artery >48 hours after symptom onset in asymptomatic patients 1, 2

Long-Term Management

Antiplatelet Therapy:

• Low-dose aspirin (75-100 mg) indefinitely 1, 2
• Continue DAPT for 12 months unless excessive bleeding risk 1, 2
• Add proton pump inhibitor (PPI) with DAPT in patients at high gastrointestinal bleeding risk 1, 2

Risk Factor Modification:

• Aggressive smoking cessation counseling with pharmacological support (nicotine replacement, varenicline, or bupropion) 1, 2
• Mandatory enrollment in cardiac rehabilitation program 1, 2

Critical Pitfalls to Avoid

• Never delay reperfusion therapy for transfer if fibrinolysis can be initiated immediately when PCI is >120 minutes away 2, 3
• Do not use fondaparinux for primary PCI 1, 2
• Avoid IV beta-blockers in acute phase if patient has hypotension, heart failure, or conduction abnormalities 1, 2
• Do not perform routine thrombus aspiration during primary PCI 2
• Recognize atypical presentations, particularly in women, elderly, and diabetic patients, to avoid diagnostic delays 2