What is the immediate management for infarct localization, particularly for myocardial infarctions (MIs)?

Immediate Management of Myocardial Infarction Based on Infarct Localization

For ST-elevation myocardial infarction (STEMI), immediate reperfusion therapy via primary PCI (if achievable within 120 minutes) or fibrinolytic therapy (if PCI delayed) is the cornerstone of management, with aspirin and antiplatelet therapy initiated immediately regardless of infarct location. 1

Initial Stabilization (All MI Types)

Upon arrival to the emergency department, the following must be administered within 10 minutes of presentation 1, 2:

• Aspirin 160-325 mg orally (or IV if unable to swallow) immediately—do not wait for ECG confirmation 1, 2
• Oxygen via nasal prongs only if oxygen saturation <90% (avoid routine oxygen as hyperoxia may increase myocardial injury) 2
• Sublingual nitroglycerin unless systolic BP <90 mmHg or heart rate <50 or >100 bpm 1, 2
• Morphine sulfate or meperidine for adequate analgesia 1, 2
• 12-lead ECG immediately to identify ST-segment elevation ≥1 mV in contiguous leads or new left bundle branch block 1

Reperfusion Strategy Based on ECG Findings

For STEMI (ST-elevation or new LBBB):

Primary PCI is the preferred reperfusion strategy when it can be performed within 120 minutes of diagnosis by an experienced team. 1, 2 Patients should bypass the emergency department and go directly to the catheterization laboratory. 1

If primary PCI cannot be performed within 120 minutes, initiate fibrinolytic therapy immediately (preferably pre-hospital) if presenting within 12 hours of symptom onset and no contraindications exist. 1, 2 Use fibrin-specific agents (tenecteplase, alteplase, or reteplase). 1

For Non-STEMI:

Do not administer thrombolytics—there is no benefit and increased bleeding risk. 2 Primary PCI is recommended but not as time-critical as STEMI. 3

Antiplatelet and Anticoagulation Therapy

Administer a potent P2Y12 inhibitor before or at the time of PCI: 1

• Prasugrel 60 mg loading dose (then 10 mg daily), or
• Ticagrelor, or
• Clopidogrel if the above are unavailable or contraindicated

Continue dual antiplatelet therapy (DAPT) for 12 months unless excessive bleeding risk. 1

For fibrinolytic therapy, add: 1

• Clopidogrel in addition to aspirin
• Enoxaparin IV followed by subcutaneous (preferred over unfractionated heparin) or weight-adjusted UFH bolus and infusion
• Transfer to PCI-capable center immediately after fibrinolysis

Special Consideration: Right Ventricular Infarction

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

• Obtain V4R lead early to identify RV involvement 2
• Avoid nitroglycerin completely—risk of profound hypotension due to preload dependence 2
• Administer aggressive IV normal saline boluses to maintain RV preload 1, 2
• Use inotropic agents if hypotension persists despite volume expansion 1

This is a critical pitfall: nitroglycerin given to a patient with RV infarction can cause catastrophic hypotension. Always check for RV involvement in inferior MIs before administering nitrates.

Additional Acute Pharmacotherapy

Intravenous nitroglycerin (not sublingual) for 24-48 hours in patients with heart failure, large anterior MI, persistent ischemia, or hypertension—but avoid in RV infarction. 1, 2

Beta-blockers: Oral therapy is indicated in patients with heart failure and/or LVEF <40%, but avoid IV beta-blockers in patients with hypotension, acute heart failure, AV block, or severe bradycardia. 1

ACE inhibitors should be initiated within 24 hours in patients with heart failure, LVEF <40%, diabetes, or anterior infarction. 2, 4

High-intensity statin therapy should be started immediately and maintained long-term. 1, 2, 4

Post-Fibrinolysis Management

Rescue PCI is indicated immediately when fibrinolysis has failed (<50% ST-segment resolution at 60-90 minutes) or with hemodynamic/electrical instability. 1

Routine angiography and PCI of the infarct-related artery should be performed 2-24 hours after successful fibrinolysis. 1

Critical Pitfalls to Avoid

• Never combine fibrinolysis with planned immediate PCI—this increases mortality and bleeding 2
• Never give thrombolytics to non-STEMI patients 2
• Never delay aspirin—give immediately, not after ECG 2
• Never give routine oxygen to non-hypoxemic patients 2
• Never give nitroglycerin in RV infarction 2
• Do not perform routine PCI of occluded infarct-related artery >48 hours after STEMI onset in asymptomatic patients 1

In-Hospital Monitoring

Routine echocardiography during hospital stay is recommended to assess LV and RV function, detect mechanical complications, and exclude LV thrombus. 1