Left Bundle Branch Block

Conduction

Recognition

  • QRS ≥120 ms
  • Broad notched 'M' R wave in I, aVL, V5–V6
  • Deep QS in V1
  • Discordant ST/T (opposite to QRS direction)

Key findings

  • No septal Q in I, V5, V6
  • Left axis common

Clinical importance

  • Obscures STEMI diagnosis — use Sgarbossa / modified Sgarbossa
  • Often structural heart disease — echo indicated

Management pearls

  • Investigate cause (IHD, cardiomyopathy, AS)
  • Consider CRT if EF ≤35 + symptomatic HF + QRS ≥130 ms
WardRound

WardRound

Clinical Decisions in Seconds