COCM: Trifascicular Block

Report:

Sinus rhythm 84 - 94/min

Left atrial abnormality

First degree AV block

Right bundle branch block

Right axis deviation +125o

?Left posterior hemiblock

?Right ventricular hypertrophy

Left ventricular hypertrophy voltage

Limb lead R wave > 20 mm

Biventricular hypertrophy?

Comment:

RVH is supported by qR morphology of V1 and the RAD, but a hemiblock or even an old septal infarction could account for the former. The answer is obtained, as often happens, from another trace: in AIVR with AV dissociation (lower panel), the axis is left, - 65o, with LAHB morphology. The RBBB is retained.

How is this evidence against RVH and for LPHB in the original tracing? Well, the escape rhythm tends to arise from distal, unblocked parts of the blocked bundle branch, which in this case must have been beyond the blocked posterior division of the left bundle branch. Hence, a ventricular focus beyond the LPHB would cause a QRS resembling LAHB.

Also, empirically, RVH would have to be disproportionately huge to be expressed in the ECG of a COCM patient. I have never seen it.

The term trifascicular is to be avoided in reporting, because of the multiplicity of its possible meanings. Here it is, more permissibly, used only in the title. To attract attention.

287. 68 year old lady with permanent pacemaker. What is the cause of her rhythm?

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