Delectable Deductive Diagnosis of RBBB/LPHB

Report:

Dual chamber pacemaker rhythm 70/min 2

Frontal plane axis –20o 2

Ventricular fusion complexes throughout 3

Probable underlying right bundle branch block with right axis deviation 3

Comment:

I make no apologies for the subcontinental flavour of the title.

The inference of the intrinsic intraventricular conduction deficit is based on the knowledge of what “pure” paced complexes are like: they have LBBB morphology with LAD in the frontal plane. Normalised QRS and axis in this paced rhythm imply fusion of RBBB and LBBB morphologies; normalised axis means fusion of beats with RAD and LAD, respectively. Fat parents – lean children! All one has to do is think of it and decide that the QRS complexes look “funny” enough to be fusion beats.

This was indeed the case. The trace shown below (Fig 50a) shows the classical RBBB + LPHB combination, perhaps due to an old septal infarction manifest as qR in V1. In assessing the electrical axis of the limb leads, only the initial 0.06” of the QRS is considered, although in this case it matters little (the rest of the complex has the same axis). As always, LPHB cannot be diagnosed with certainty unless RVH is excluded on other-than-ECG grounds. Both qRV1 and RAD are cardinal signs of RVH.

I recently published this case, more the aliterative original title than for its ECGs30.