ECG of the Week 20 July 2022 Answer

A 83 year old male presents to ED after a syncopal episode. Below is the patients ECG

Describe and Interpret the ECG


Rate: 54 beats per minute

Rhythm: Mobitz Type I Second Degree AV block

Axis: Left Axis


PR: Increasing PR segment, followed by drop QRS

QRS: 160ms

QTc: 455ms


RBBB Morphology

Left Anterior Fascicular Block noted by left axis,  qR wave I and aVL, rS wave in II, III, aVF

The combination of RBBB, LAFB and second degree block indicates a possible incomplete trifascicular block. As second degree AV blocks can occur at the AV node and therefore might not involve fascicular disease, so a diagnosis of a trifascicular block can only be made through a His Bundle recording.

In the context of syncope a Mobitz Type I Second degree AV block alone as well as a possible trifascicular block requires referral and admission under cardiology.