Rate-Dependent RBBB

Report:

Sinus rhythm 75/min

First degree AV block

PR 0.22”

VEBs, uniform

Rate-dependent right bundle branch block

Borderline ST segment depression in 2, aVF

Comment:

Without a hemiblock, RBBB has a qRS pattern in V6. This is a normal, “septal” q wave, inscribed by the initial left-to-right myocardial depolarisation across the septum. There are, however, similar q waves all the way to V2: this may indicate an old infarction or septal fibrosis, perhaps from chronic LVH.

The two VEBs are followed by normalised QRS complexes which, as often happens in intermittent RBBB, show a tendency to incomplete RBBB pattern. They are 0.10” long and have “embryonic” R’ waves (not reaching beyond the baseline).

The precordial sequence is almost concordant, with large voltages in both right and left ventricular leads. The RBBB prevents the diagnosis of LVH, which emerges in normal conduction (Fig 67a). The RV5 is 36 mm and the ST/T changes and the LAA are more convincing than in the original ECG.

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