Inferior Myocardial Infarction on ECG

Introduction

An inferior myocardial infarction (MI) refers to a heart attack affecting the inferior (bottom) part of the heart, usually supplied by the right coronary artery (RCA) or sometimes the left circumflex artery (LCx).

Key ECG Features of Inferior MI:

  1. ST-segment elevation in leads II, III, and aVF (these leads reflect the inferior wall of the heart).
  2. Reciprocal ST-segment depression in leads I and aVL (suggesting a true ischemic event).
  3. Possible right ventricular involvement:
    • If ST elevation is greater in lead III than in lead II, it suggests right ventricular infarction.
    • Obtain right-sided chest leads (V4R, V5R, V6R) if right ventricular infarction is suspected.
  4. Bradycardia and heart blocks due to involvement of the AV node, which is often supplied by the RCA.

Clinical Significance

  • Inferior MI often presents with nausea, vomiting, and vagal symptoms (slow heart rate and low blood pressure) rather than severe chest pain.
  • Complications: May include hypotension, heart block, and right ventricular infarction, which require careful management.
  • Treatment: Patients require immediate aspirin, P2Y12 inhibitors (e.g., clopidogrel), heparin, and most require urgent revascularization with PCI (percutaneous coronary intervention).

Conclusion

Recognizing an inferior MI on ECG is critical for early diagnosis and treatment, especially considering the potential for severe complications.

Source recommendations

1. American Heart Association Guidelines for Management of ST-Elevation Myocardial Infarction

  1. https://professional.heart.org/en/science-news/2021-acc-aha-scai-guideline-for-coronary-artery-revascularization
  2. https://www.ahajournals.org/doi/10.1161/cir.0b013e3182742cf6
  3. https://pubmed.ncbi.nlm.nih.gov/23256914/
  4. https://www.ahajournals.org/doi/10.1161/01.cir.0000134791.68010.fa
  5. https://www.sciencedirect.com/science/article/pii/S073510972106157X

2. European Society of Cardiology Guidelines for Acute Coronary Syndromes

  1. https://www.escardio.org/Guidelines/Clinical-Practice-Guidelines/Acute-Coronary-Syndromes-ACS-Guidelines
  2. https://academic.oup.com/eurheartj/article/44/38/3720/7243210
  3. https://pubmed.ncbi.nlm.nih.gov/37622654/
  4. https://academic.oup.com/eurheartj/article/42/14/1289/5898842
  5. https://pubmed.ncbi.nlm.nih.gov/32860058/

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