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Lesson 18 of 21 · Ischemia

ST Changes & STEMI Evolution

Myocardial infarction evolves on the EKG over minutes to weeks. Recognizing each stage tells you how old the infarct is and whether reperfusion is still possible.

01Evolution

STEMI evolution
NormalbaselineHyperacute TminutesST elevationminutes–hoursQ wave + STEhours–daysQ + T inversiondays–weeks
V2
Minutes: hyperacute T waves.
V3
Hours: ST elevation with developing Q waves.
III
Days–weeks: pathologic Q wave with T inversion.

02STEMI equivalents (no classic STE, still occlusion)

  • Posterior MI: ST depression V1–V3 with tall R and upright T, so get V7–V9
  • de Winter T waves: upsloping ST depression + tall symmetric T in V1–V6 (proximal LAD)
  • Sgarbossa-positive LBBB or paced rhythm
  • STE in aVR with diffuse ST depression: left main / 3-vessel disease
V3
de Winter pattern: upsloping ST depression into a tall T wave.

03Wellens syndrome

Seen pain-free, after an episode of chest pain. It signals critical proximal LAD stenosis. Avoid stress testing; these patients need angiography.

V2
Type A: biphasic T in V2–V3.
V2
Type B: deep symmetric T inversion.

Key takeaways

  • Hyperacute T → STE → Q wave → T inversion
  • Posterior MI hides as anterior ST depression
  • Wellens = pain-free, critical LAD