Left Anterior Hemiblock Aberrancy

Report:

Sinus rhythm

Normal axis +70o

Allorhythmic triplets of SVT following single sinus beats

First complex LAHB aberrant –40o

Comment:

The SVT triplets are separated by a single sinus beat – a minimalist (three-beat) form of repetitive atrial tachycardia. Second complex in each group of four is, as expected – aberrant but, not as expected, with LAHB as its sole aberrancy. This is uncommon. There is not a smidgen of the more usual RBBB: it would have shown as a shortening of the S wave in lead V1.

The allorhythmia persisted, but its aberration took on more familiar form of variable degrees of RBBB. In the tracing below (Fig 36a), only the second beat in the first group is “pure” LAHB. Other second beats and, at the end, a third beat, all have RBBB.

Fig 36a. The smallest aberrant complex in V1 has an embryonic R’ wave – not yet born above the baseline.

Fig 37. 79 year old man with permanent pacemaker inserted for LBBB and 2o AV block three years previously.

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