What is the management of an inferior ST-Elevation Myocardial Infarction (STEMI) on an electrocardiogram (ECG)?

Management of Inferior ST-Elevation Myocardial Infarction (STEMI)

Immediate reperfusion therapy is the cornerstone of management for inferior STEMI and should be initiated as soon as possible, with primary percutaneous coronary intervention (PCI) as the preferred strategy when available within 90 minutes of first medical contact.

Initial Assessment and Diagnosis

• A 12-lead ECG should be performed and interpreted within 10 minutes of first medical contact for all patients with suspected STEMI 1
• In patients with inferior STEMI, right-sided ECG leads (V3R and V4R) must be obtained to screen for right ventricular (RV) infarction, which affects management decisions 1
• Continuous cardiac monitoring with defibrillator capacity should be initiated immediately 1
• Laboratory tests should be ordered but should not delay reperfusion therapy 1
• Cardiac-specific troponins are the preferred biomarkers but reperfusion decisions should not wait for results 1

Immediate Management

Reperfusion Strategy

1. Primary PCI (preferred approach):

   • Should be performed within 90 minutes of first medical contact 1, 2
   • Patients should bypass the emergency department and go directly to the catheterization laboratory 1

2. Fibrinolytic therapy:

   • If primary PCI cannot be performed within 90 minutes, administer fibrinolytic therapy within 30 minutes of hospital arrival 1
   • Only for patients presenting within 12 hours of symptom onset without contraindications 1

Antithrombotic Therapy

• Aspirin: 162-325 mg chewed immediately 2
• P2Y12 inhibitor: Load with either:
  • Prasugrel (60 mg) or ticagrelor (180 mg) preferred, or
  • Clopidogrel (300-600 mg) if others unavailable or contraindicated 1, 2
• Anticoagulation: Based on reperfusion strategy and patient factors

Special Considerations for Inferior STEMI

Right Ventricular Infarction Management

If right ventricular involvement is present (ST elevation in V4R):

• Maintain right ventricular preload:
  • IV fluid loading is often effective 1
  • Avoid vasodilators (nitrates, opioids), diuretics, and ACE inhibitors/ARBs initially 1
• Treat bradyarrhythmias promptly:
  • Atrial fibrillation should be corrected quickly as atrial contribution to RV filling is important 1
  • If heart block develops, dual chamber pacing should be implemented 1, 3

Post-Reperfusion Management

Medication Therapy

• Dual antiplatelet therapy: Continue for 12 months 2
• Beta-blockers: Start early if no contraindications 2
• ACE inhibitors: Start within 24 hours in patients with anterior STEMI, heart failure, or EF ≤40% 2
• Statins: High-intensity statin therapy for all patients 2
• Aldosterone antagonists: For patients with EF ≤40% and either symptomatic heart failure or diabetes 2

Monitoring and Hospital Course

• Monitor for at least 24 hours after reperfusion therapy 1
• Patients can be transferred from CCU to step-down unit after 12-24 hours of clinical stability 2
• Low-risk patients who have undergone successful PCI can be admitted directly to a step-down unit 2

Complications to Monitor

• Complete heart block: Common in inferior STEMI due to right coronary artery occlusion; may require temporary pacing 3
• Right ventricular failure: Presents with hypotension, clear lung fields, and elevated jugular venous pressure 1
• Ventricular arrhythmias: Require immediate treatment

Pitfalls to Avoid

1. Delaying reperfusion while waiting for laboratory results - This increases mortality and should be avoided 1, 2
2. Missing right ventricular involvement - Always obtain right-sided ECG leads in inferior STEMI 1
3. Administering nitrates in RV infarction - Can cause profound hypotension 1
4. Continuing NSAIDs (except aspirin) - Increases risk of mortality, reinfarction, and complications 1
5. Overdiagnosis of STEMI - Experienced electrocardiographers show wide variation in interpreting STE patterns; when in doubt, seek expert consultation 4

Remember that time is myocardium - the most critical factor in STEMI management is minimizing the time from symptom onset to reperfusion therapy to reduce mortality and improve long-term outcomes.