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Lateral STEMI

Not medically reviewed · Content last updated · 1 min read ·

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

Lateral ST-elevation myocardial infarction shows ST elevation in I, aVL, V5 and V6, from occlusion of the left circumflex artery or a diagonal branch of the left anterior descending artery. It is often small in isolation but frequently coexists with anterior or inferior involvement.

ECG criteria

  • New J-point ST elevation of 1 mm or more in two contiguous lateral leads: I, aVL, V5, V6.
  • Reciprocal ST depression in the inferior leads (III and aVF).
  • Often associated with anterior (anterolateral) or inferior (inferolateral) changes.
  • Pathological Q waves and T-wave inversion appear as the infarct evolves.
  • Isolated high lateral changes in I and aVL alone can be subtle and are easily missed.

Mechanism

Acute occlusion of the left circumflex artery or of a diagonal branch of the left anterior descending artery deprives the lateral wall of the left ventricle of blood. The injury current is directed toward the lateral leads, with mirror-image changes in the inferior leads.

Common causes

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

Management principles

Management follows the general STEMI principle of rapid reperfusion, preferably by primary percutaneous coronary intervention, within the local STEMI pathway. The circumflex territory can be electrically silent, so a high index of suspicion is needed; follow local guidelines.

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

Pitfalls and mimics

  • Isolated circumflex occlusion may produce little or no ST elevation on the 12-lead ECG; the ECG can be normal despite a significant infarct.
  • ST elevation limited to I and aVL with inferior reciprocal depression is easily overlooked or attributed to a normal variant.
  • Early repolarisation, pericarditis and left ventricular hypertrophy can mimic lateral ST elevation.

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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