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Inferior STEMI

Not medically reviewed · Content last updated · 2 min read ·

This is the date the draft was written, not a medical review date.

Inferior ST-elevation myocardial infarction shows ST elevation in II, III and aVF, from occlusion of the right coronary artery in most people and of the left circumflex in others. It is commonly complicated by bradyarrhythmias and may involve the right ventricle.

ECG criteria

  • New J-point ST elevation of 1 mm or more in at least two contiguous inferior leads (II, III, aVF).
  • Reciprocal ST depression in I and aVL, often early and a useful clue.
  • ST elevation greater in III than in II suggests right coronary artery occlusion; greater in II than III suggests left circumflex.
  • Extension to the right ventricle (ST elevation in V1 or right-sided leads V3R-V4R) and possible AV block, sinus bradycardia.
  • Evolution: hyperacute T waves, then Q waves in the inferior leads and T inversion.

Mechanism

Acute thrombotic occlusion of the artery supplying the inferior wall, the posterior descending artery arising from the right coronary artery (right-dominant circulation, the majority of people) or the left circumflex, causes inferior wall injury. The right coronary artery also supplies the sinoatrial and AV nodes in most people, explaining the conduction disturbances.

Common causes

  • Atherosclerotic plaque rupture or erosion with thrombosis in the right coronary artery or left circumflex.
  • Risk factors: smoking, diabetes, hypertension, dyslipidaemia, family history.
  • Less common: coronary spasm, spontaneous coronary artery dissection, embolism, aortic dissection involving the right coronary ostium.

Management principles

Management is rapid reperfusion within the local STEMI pathway, preferably by primary percutaneous coronary intervention. When the right ventricle is involved, preload-dependent haemodynamics need careful handling, and bradyarrhythmias are managed by the local protocol; follow local guidelines.

High-level principles for study. Treatment decisions follow local guidelines and the clinical situation.

Pitfalls and mimics

  • Right ventricular involvement is easily missed on a standard 12-lead ECG; record right-sided leads (V3R-V4R), because preload-reducing drugs such as nitrates can cause severe hypotension.
  • Pericarditis (diffuse ST elevation with PR depression, no reciprocal change) and early repolarisation mimic inferior STEMI.
  • Inferior ST elevation with reciprocal depression in V1-V3 may signal concurrent posterior involvement; consider leads V7-V9.

Practise in the ECG trainer — Recognise this pattern on generated tracings.

References

  1. 2023 ESC Guidelines for the management of acute coronary syndromes. European Society of Cardiology (2023) — Tier 2 (guidelines / primary literature)
  2. Fourth Universal Definition of Myocardial Infarction (2018). ESC / ACC / AHA / World Heart Federation (2018) — Tier 2 (guidelines / primary literature)
  3. Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine. Elsevier, 12th edition (2022) — Tier 3 (textbook)

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