Anterior MI — Distal LAD
What it is: The most common type of anterior STEMI.
Where the block is: The LAD is occluded distal to (after) the large diagonal branch.
Area affected: Only the anterior wall and the apex of the heart.
Golden rule: The block is far down the artery, so injury is strictly precordial (V1–V4) with no inferior reciprocal change.
ST elevation: Convex (“coved”) in V1–V4, peaking in V2–V3, with mild spread to V5–V6.
Key differentiator: No reciprocal ST depression in II III aVF.
This absence is what tells you the lesion is distal, not proximal.
T-waves: Upright, tall, hyperacute T waves.
R-waves: Poor R-wave progression or QS complexes in V1–V3.
QRS: Narrow / preserved.
The conduction system is supplied proximally, so it is spared by this distal block.
Diagnose STEMI from J-point ST elevation (STE) meeting these thresholds:
In V2–V3
- ≥ 2.0 mm — men aged 40 and older
- ≥ 2.5 mm — men under 40
- ≥ 1.5 mm — women
In V1, V4 and other leads: ≥ 1.0 mm
Territory size: The smallest of the three anterior territories.
Prognosis: Excellent — the best among anterior STEMIs, if treated quickly.
Clinical mantra: “Time is muscle.” Outcomes are highly favorable with reperfusion within 6–12 hours.
Why is there no reciprocal ST depression in the inferior leads?
Which single feature localises the lesion as distal to D1?
What is the reperfusion window for a good prognosis?