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Lbbb ecg fast

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LBBB left bundle branch block ECG pattern

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Here's a rapid LBBB ECG summary:

LBBB — ECG Quick Reference

Panel E (LBBB) from Goldman-Cecil Medicine:
LBBB ECG — Goldman-Cecil Medicine
12-lead LBBB example:
12-lead LBBB

Diagnostic Criteria (complete LBBB)

FeatureFinding
QRS duration≥ 120 ms (wide)
V1Broad, deep QS or rS (predominantly negative)
I, aVL, V5–V6Broad, notched or monophasic R wave (no septal q waves)
AxisNormal or left axis deviation
ST/T wavesDiscordant — opposite direction to QRS throughout precordium
Memory tool — WiLLiaM: In LBBB, Lead W in V1 (down-up), M in V5/V6 (up-down). (Vs. RBBB = MaRRoW)

Key ECG Features Explained

  • No septal q waves in I, V5, V6 — because normal left-to-right septal activation is reversed
  • Broad notched R in lateral leads — slurred, "M-shaped" upstroke
  • QS or rS in V1 — deep negative deflection; initial small r may be absent
  • Discordant ST-T — ST elevation in V1–V3, ST depression + T-wave inversion in lateral leads (this is normal/expected in LBBB, not ischemia)

LBBB vs. RBBB at a glance

LBBBRBBB
V1QS or rS (negative)rSR' (rabbit ears)
V6Broad R, no qWide S wave
ST/TDiscordant throughoutDiscordant in V1–V2 only
AxisNormal/LADNormal

Clinical Significance

ContextAction
New LBBB + chest painTreat as STEMI equivalent — activate cath lab
Sgarbossa criteriaConcordant ST elevation ≥1 mm, or discordant ST elevation >25% of S-wave depth → suggests AMI in LBBB
Incidental LBBB2× increased cardiovascular mortality — evaluate for underlying cardiac disease
Wide complex tachycardia with LBBB morphologyConsider bundle branch re-entry VT or RV-origin VT
Sources: Goldman-Cecil Medicine, Table 42-3 & Fig. 42-5E; Tintinalli's Emergency Medicine; Braunwald's Heart Disease
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