Compare
RBBB vs LBBB
| Dimension | RBBB | LBBB |
|---|---|---|
| V1 morphology | rSR' (rabbit ears) | Deep QS or rS |
| Lateral leads (I, V6) | Wide slurred S wave | Broad monophasic R, no septal Q |
| Clinical weight | Can be benign; new RBBB with hypoxia suggests PE | Almost always structural disease; new LBBB reframes chest pain |
| Ischemia reading | Early QRS preserved: Q waves stay readable | Whole QRS rewritten: use concordance criteria |
Pearls
- Turn to V1 first: the direction of the terminal force names the bundle.
- LBBB plus chest pain is a reperfusion conversation when concordance criteria fire.
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