Ischaemia and infarction
Anterior STEMI
Convex ST elevation across the anterior chest leads — the LAD occlusion you cannot afford to sit on.
What you see
- ST elevation ≥ 2 mm (men) or ≥ 1.5 mm (women) in two contiguous chest leads, V1–V4.
- The elevated segment is convex — it bulges upward rather than smiling.
- Reciprocal ST depression in II, III and aVF.
- Q waves appear within hours; loss of R wave progression follows.
Why it looks like that
Occlusion of the left anterior descending artery stops perfusion of a large wedge of anterior myocardium. Injured but still-living muscle holds an abnormal resting potential, and the resulting current of injury shifts the ST segment towards the leads facing the infarct — and away from the leads facing it from the other side, which is what reciprocal change is.
What to do
- Primary PCI within 120 minutes of first medical contact; thrombolysis if that is not achievable.
- Dual antiplatelet therapy and anticoagulation as per local protocol before transfer.
- Treat the complications you can predict: pump failure, VT/VF in the first hours, and later ventricular septal rupture or free wall rupture.
The trap
A proximal LAD occlusion can present with ST elevation in aVR and widespread depression instead of the classic anterior picture. Diffuse ST depression with aVR elevation is left main or proximal LAD disease until proven otherwise, and it belongs in the cath lab, not on a medical ward.
More in ischaemia and infarction
Inferior STEMI
ST elevation in II, III and aVF with reciprocal change in aVL — and a right ventricle you must check before giving nitrates.
Posterior myocardial infarction
Tall R waves and ST depression in V1–V3 — a STEMI viewed from behind, and easy to call NSTEMI by mistake.
Wellens' syndrome
Deep or biphasic T waves in V2–V3 in a pain-free patient — critical LAD stenosis waiting to declare itself.
De Winter T waves
Upsloping ST depression with tall symmetrical T waves in the chest leads — an LAD equivalent without the elevation.