ECG of the Week 18th January 2023 – Interpretation
The key determination here is what the patient’s rhythm is. It is a tachyarrhythmia, with no visible P waves, and a rate marginally exceeding 150 beats per minute. Looking at an entire 10 second rhythm strip in lead I, the rhythm is irregularly irregular, with broad complexes as well as narrow complexes. The short two seconds of narrow complex rhythm is typical of atrial fibrillation. The most logical deduction is the patient has an aberrant conduction pathway, and is also in atrial fibrillation, at times conducting down the native AV node / Bundle of His /Purkinje fibres and at other times, conducting down an aberrant pathway after passing through the AV node. If the broad complex rhythm was more regular, there would be more consideration for runs of non-sustained ventricular tachycardia, but this is less likely the case, especially given the luxury of observing the patient’s cardiac rhythm over a longer period than 10 seconds the ECG.
As a reminder, the Brugada criteria that make a rhythm more likely to be ventricular tachycardia than a supraventricular tachycardia with aberrant conduction are:
Absence of RS complexes in the precordial leads
RS duration exceeding 100 ms in any precordial lead
Ventriculoatrial dissociation in any of 12 leads (capture beats, fusion beats, presence of P waves seen amongst wide complex QRS)
Certain QRS morphologies, such as QR or QS in lead V6