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LBBB on echo: septal flash, apical rocking and dyssynchrony

An early, quick inward "flash" of the septum, then paradoxical motion as the lateral wall contracts late, with the apex rocking from septum to lateral. The septum still thickens (sometimes less than normal): this is dyssynchrony, not ischaemia.

Watch it in the simulator →Practise random cases

Where to look

Apical 4-chamber (septal flash and apical rocking), PLAX and PSAX (early septal inward flick followed by paradoxical motion). Check the QRS on the ECG strip.

Typical wall-motion pattern

Example: Left bundle branch block

All 17 segments thicken normally.

EF in this example: 37% (Impaired (36–49%)).

1 Normal2 Hypokinetic3 Akinetic4 Dyskinetic5 Aneurysmal

Ejection fraction

Across 24 simulated cases of this pattern the true EF ranged from 34% to 40% (median 37%, Impaired (36–49%)). Every case in the simulator is different, so practise until your visual estimate lands in the right 5% range.

Teaching points

LBBB: early septal "flash" inward then paradoxical motion, with apical rocking toward the late-contracting lateral wall. Thickening is preserved (it may be reduced), so this is dyssynchrony, NOT an ischaemic RWMA.
Ventricular ectopics: the premature beat is weak and dyssynchronous and the beat after the pause is stronger. Judge EF and wall motion on normal sinus beats only.

Common pitfalls

The septum moves abnormally but still thickens, so it is graded normal. Thickening may be reduced if there is also septal infarction.

Try it now: open the LBBB dyssynchrony example with the segment overlay, then test yourself in Practice where cases are random and graded against the exact answer.