The lateral wall of the left ventricle is supplied by branches of the left anterior descending (LAD) and left circumflex (LCx) arteries.
STEMI of the lateral wall usually occurs as part of a larger territory infarction, e.g. anterolateral STEMI.
Lateral extension of an anterior, inferior or posterior MI indicates a larger territory of myocardium at risk with consequent worse prognosis.
STEMI of the lateral wall is usually caused by acute atherosclerotic plaque rupture with subsequent thrombus formation in the left circumflex artery (LCx) or one of its branches (marginal branch).
More commonly, left anterior descending (LAD) artery is involved in the ensuing anterolateral MI (diagonal branch). Ramus intermedius occlusion might be seen as well.
Inferolateral STEMI - ST-elevation involving lateral (I, aVL, V5, V6) and inferior leads (II, III, aVF) - usually seen with occlusion of the proximal LCx artery.
Anterolateral STEMI - ST-elevation involving lateral (I, aVL, V5, V6) and anterior leads (V1, V2, V3) - usually highly indicative of proximal LAD occlusion.
ECG 1 STEMI lateral (ST elevations I, aVL, V4-V6, ST depressions in inferior leads) - diagonal branch occlusion
ECG 2 STEMI of lateral wall (ST elevations in I, aVL, V5-V6) in a patient with occlusion of ramus intermedius