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

Treatment of Occlusive Myocardial Infarction

Primary percutaneous coronary intervention (PCI) is the preferred reperfusion strategy for occlusive MI when it can be performed within 90-120 minutes of first medical contact by experienced operators; if this timeframe cannot be met, immediate fibrinolytic therapy should be administered within 10 minutes of diagnosis for patients presenting within 12 hours of symptom onset. 1, 2, 3

Immediate Stabilization (First 10 Minutes)

• Administer aspirin 160-325 mg immediately upon arrival (not after ECG confirmation), which reduces 35-day mortality by 21% when combined with reperfusion therapy 2, 3
• Obtain a 12-lead ECG within 10 minutes to confirm ST-segment elevation or new left bundle branch block 1, 2
• Provide sublingual nitroglycerin unless systolic blood pressure is <90 mmHg, heart rate is <50 or >100 bpm, or right ventricular infarction is suspected (where nitroglycerin is absolutely contraindicated due to risk of profound hypotension) 2, 4
• Administer oxygen via nasal prongs only if oxygen saturation is <90% (routine oxygen in non-hypoxemic patients may increase myocardial injury) 2, 3
• Give morphine sulfate for adequate analgesia of chest pain 2, 5
• Establish continuous cardiac monitoring with defibrillator immediately available 4, 3

Reperfusion Strategy Selection

The choice between primary PCI and fibrinolysis depends strictly on time-to-treatment:

Primary PCI (Preferred Option)

• Perform primary PCI if it can be achieved within 90 minutes of first medical contact (or 120 minutes from STEMI diagnosis) 1, 2, 3
• Primary PCI achieves TIMI flow grade 3 in 70-90% of patients and has lower intracranial bleeding risk compared to fibrinolysis 1, 6
• The mortality benefit of PCI over fibrinolysis is lost if PCI-related time delay exceeds 60-110 minutes, though longer delays may still benefit highest-risk patients 1
• Pre-hospital ECG transmission should activate the catheterization laboratory, allowing direct transfer bypassing the emergency department 1

Antithrombotic regimen for primary PCI: 3

• Unfractionated heparin IV
• Aspirin loading dose
• Prasugrel or ticagrelor (preferred over clopidogrel unless high bleeding risk exists) 1

Fibrinolytic Therapy (When PCI Cannot Be Performed Timely)

• Initiate fibrinolysis within 10 minutes of STEMI diagnosis if primary PCI cannot be performed within the recommended timeframe 1, 2
• Greatest benefit occurs within the first hour of symptom onset (35 lives saved per 1000 patients treated) 4
• Use fibrin-specific agents: tenecteplase, alteplase, or reteplase 2
• Reduce tenecteplase dose by 50% in patients ≥75 years to minimize stroke risk 2

Antithrombotic regimen for fibrinolysis: 3

• Enoxaparin
• Aspirin loading dose
• Clopidogrel 75 mg daily

Absolute contraindications to fibrinolysis include recent surgery (due to substantial bleeding risk at surgical site), making primary PCI the only option for perioperative MI 1, 7

Special Populations and Scenarios

Cardiogenic Shock

• Primary PCI is recommended for patients <75 years who develop shock within 36 hours of MI, when revascularization can be performed within 18 hours of shock onset 1
• For selected patients ≥75 years with good prior functional status who agree to invasive care, primary PCI is reasonable 1
• The SHOCK trial demonstrated 15% absolute reduction in 30-day mortality for patients <75 years treated with emergency revascularization 1

Right Ventricular Infarction

• Occurs in up to 50% of inferior MIs and requires specific management modifications 2
• Obtain V4R lead early for diagnosis 2
• Maintain right ventricular preload with IV saline boluses 2
• Completely avoid nitroglycerin due to risk of profound hypotension 2

Late Presentation (>12 Hours)

• Reperfusion therapy (preferably primary PCI) is indicated if there is evidence of ongoing ischemia, even if symptoms started >12 hours ago 1
• Primary PCI may be considered in stable patients presenting 12-24 hours after symptom onset 1
• Routine PCI of a totally occluded artery >24 hours after symptom onset in stable patients without signs of ischemia is not recommended (based on the Occluded Artery Trial showing no clinical benefit) 1

Failed Fibrinolysis

• Rescue PCI should be performed for patients with hemodynamic or electrical instability or persistent ischemic symptoms after failed fibrinolysis 1
• Rescue PCI is reasonable for patients <75 years with continuing myocardial ischemia within 12 hours after failed fibrinolysis 1

Additional Pharmacotherapy (First 24-48 Hours)

• Intravenous nitroglycerin for 24-48 hours in patients with heart failure, large anterior MI, persistent ischemia, or hypertension (avoid in right ventricular infarction) 2, 4
• ACE inhibitors within the first 24 hours for patients with heart failure, LVEF <40%, diabetes, or anterior infarction 2, 3
• High-intensity statin therapy started as soon as possible and maintained long-term 2
• Beta-blocker therapy (early IV followed by oral) if no contraindications exist 4, 5
• Consider anticoagulation with IV heparin for 48 hours, particularly for large anterior MI or LV mural thrombus 4

Critical Pitfalls to Avoid

• Never combine fibrinolysis with planned immediate PCI (increases mortality and adverse outcomes) 2
• Never give thrombolytics to patients with non-ST-elevation MI (no benefit, increased bleeding risk) 2
• Never delay aspirin administration waiting for ECG confirmation 2
• Never use routine oxygen in non-hypoxemic patients 2
• Never use prophylactic antiarrhythmic agents in the first 24 hours 4
• Never use calcium channel blockers acutely (not shown to reduce mortality and may be harmful) 4

Long-Term Management

• Aspirin 160-325 mg daily indefinitely 3
• Dual antiplatelet therapy (DAPT) for one year 3
• Beta-blockers for minimum of 6 weeks 4, 3
• ACE inhibitors, especially for anterior MI or LV dysfunction 3
• Bed rest for first 12-24 hours for significant LV damage, then progressive ambulation starting day 2 3