SVT with Right Bundle Branch Block Aberrancy

Report:

SVT 212/min.

Right bundle branch block (RBBB).

Right axis deviation +120o probably left posterior hemiblock (LPHB).

Comment:

The likelihood of aberrancy rests with the rSR’ morphology in lead V1 and the absence of any bizarre features. Verapamil was used legitimately in this context; adenosine would have been even better, but was not yet available. She rapidly reverted to sinus rhythm (Fig 35a).

A verapamil-sensitive fascicular VT cannot be completely excluded. The rate is very rapid, but this, too, does not help distinguish VT from SVT, as readers of this Volume know or are about to find out. For a fast SVT, it is noteworthy that there is no electrical alternans. This may mean that there is no bypass tract, concealed or otherwise – the (micro)reentry is a nodal one.

Retrograde P waves are seen in most leads; they do not advance the diagnosis.

The sinus rhythm ECG is normal apart from small voltage and borderline ST/T changes. The reason for the former was not clinically obvious; the latter were uninterpretable in view of the preceding SVT.

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