Ischaemia and infarction
Posterior myocardial infarction
Tall R waves and ST depression in V1–V3 — a STEMI viewed from behind, and easy to call NSTEMI by mistake.
What you see
- Horizontal ST depression in V1–V3, deepest in V2.
- R wave taller than the S wave is deep in V2, with a broad R in V1–V2.
- Upright T waves in the same leads — depression with an upright T is the giveaway.
- Posterior leads V7–V9 show ST elevation of ≥ 0.5 mm.
Why it looks like that
The posterior wall has no lead facing it in the standard twelve. The anterior chest electrodes look at it from the opposite side, so every vector reverses: elevation becomes depression, Q waves become tall R waves, and inverted T waves become upright ones.
What to do
- Apply posterior leads whenever there is ST depression maximal in V1–V3.
- Treat a confirmed posterior infarct as a STEMI — it meets criteria for primary PCI.
- Look for accompanying inferior or lateral change; isolated posterior infarction is uncommon.
The trap
Anterior ST depression gets labelled 'anterior ischaemia' or NSTEMI and the patient waits overnight for an angiogram. The combination of ST depression *and* an upright T *and* a dominant R in V2 should stop that happening.
More in ischaemia and infarction
Anterior STEMI
Convex ST elevation across the anterior chest leads — the LAD occlusion you cannot afford to sit on.
Inferior STEMI
ST elevation in II, III and aVF with reciprocal change in aVL — and a right ventricle you must check before giving nitrates.
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.