STEMI

Time course of ECG progression
  • ​Variable; phases may be skipped
  • ECG progression is modified by reperfusion therapy
ECG Leads
 Location of MI
Probable Culprit
II, III, aVF (±V5,V6)
Inferior
RCA (or dominant LCX)
Mirror image V1-V2 (R­, ST¯, T­)
Posterolateral
LCX
II-III-aVF, plus V1 and RV4
Inferior + RV
Proximal RCA
V1-V4
Anteroseptal
LAD
V1-V6 (± I, aVL)
Extensive Anterior
LAD
I, aVL, V4-V6  ​
Lateral
LCX
I, aVL, V2 (± mirror image III)
High Lateral
LAD-D1
FREQUENTLY MISSED MIs
Posterolateral (LCX)
  • Almost always due to LCX occlusion, accounts for 10-15% of all STEMIs and is the most frequently missed
  • ST depression but upright T waves in V1-V3 (diff dx: ant. ischemia or posterolateral STEMI)
  • Later: increased R/S ratio in V1-V2
  • Frequently accompanied by small Q waves or T-wave inversion in inferior or lateral leads
  • If you suspect posterior MI, place additional electrodes
    • V7 posterior axillary
    • V8 tip of the scapula
    • V9 left paraspinal line
  • Frequently associated with ischemia or infarction of the posterior papillary muscle
  • May result in mitral regurgitation
Picture
ST Depression in V1-V4, subtle ST Elevation in I, aVL
High lateral
  • Second most frequently missed MI, rare and usually small
  • Typically LAD-D1
  • Subtle ST in aVL, V2, sometimes in I
  • Mirror image (QRS, ST and T) in lead III
  • "South African Flag" sign
  • If you suspect high lateral MI, move V4, v5, V6 up one intercostal space
RV infarct
  • Almost always in association with inferior MI
  • ST in R-sided chest leads; sometimes in V1; rarely in V1-V4 (may mimic anterior STEMI)
  • Combination of ST in inferior leads plus ST in V1 is highly specific for RV infarct
  • Frequently associated with sinus bradycardia or atrial fibrillation with AV block
Anterior “STEMI” without ST elevation
  • J-point depression followed by upsloping STs in the anterior chest leads
  • Very tall (“hyperacute”) T waves usually taller than the corresponding QRS complexes
DeWinter's Sign
  • Proximal LAD occlusion
  • 1-3 mm upsloping ST depression at the J point in V1-V6
  • Tall, positive symmetrical T waves
  • Ts may be taller than R waves
  • Slight ST elevation in aVR
  • Patients frequently young males
  • No distinct anatomic pattern of CAD