EKG
Axis, LVH, RVH — the basics
EKG

Axis, LVH, RVH — the basics

Quick axis determination, LVH/RVH criteria, BBB recognition.

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◆Axis in 5 seconds

  • •Look at QRS in lead I and lead II (or aVF)
  • •I up + II up → NORMAL axis (-30 to +90)
  • •I up + II down → LEFT axis (-30 to -90) — LVH, LBBB, inferior MI, LAFB, WPW
  • •I down + II up → RIGHT axis (+90 to +180) — RVH, PE, lateral MI, COPD, LPFB, dextrocardia
  • •I down + II down → EXTREME axis (NW quadrant) — VT, hyperkalemia, severe pathology

◆LVH criteria (Sokolow-Lyon)

  • •S in V1 + R in V5 or V6 ≥ 35 mm
  • •R in aVL ≥ 11 mm
  • •Strain pattern: ST depression and T inversion in lateral leads (I, aVL, V5–V6)

◆RVH criteria

  • •R/S ratio in V1 > 1 (R wave > S in V1)
  • •Right axis deviation
  • •Causes: chronic lung disease (COPD), pulmonary HTN, congenital heart disease, severe PE

◆Bundle branch blocks (QRS >120 ms)

  • •RBBB: rSR' (M shape) in V1; wide S in I, V6
  • •LBBB: broad notched R in I, V5–V6; QS or rS in V1
  • •New LBBB with chest pain = STEMI equivalent
  • •RBBB doesn't typically affect QRS axis or invalidate STEMI criteria; LBBB does

High-yield pearls

  • ◆LVH with strain in a hypertensive patient = chronic uncontrolled HTN until proven otherwise
  • ◆S1Q3T3 in PE reflects acute RV strain — accompanied by sinus tach and T inversions V1–V4
  • ◆Bifascicular block (RBBB + LAFB or LPFB) + 1° AV block = trifascicular block — high risk of complete heart block
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