A regularly irregular tachycardia with variable QRS morphologies - What is the mechanism?

Area of Science:

• Cardiology
• Electrophysiology
• Cardiac Arrhythmias

Background:

• Understanding complex cardiac arrhythmias is crucial for accurate diagnosis and treatment.
• Bundle branch block alternans, a rare phenomenon, requires further investigation into its underlying mechanisms.

Observation:

• A unique case of atrial tachycardia with Mobitz type I AV block and concurrent right bundle branch block (RBBB) alternans during a Wenckebach cycle was observed.
• This presentation differs from previously described cases of bundle branch alternans, which typically occur during 1:1 atrioventricular conduction.

Findings:

• The study provides a detailed explanation of the complex arrhythmia mechanism, integrating atrial tachycardia, AV Wenckebach, and RBBB alternans.
• The mechanism of bundle branch alternans is reviewed in the context of this complex presentation.

Implications:

• This case expands the understanding of bundle branch alternans by demonstrating its occurrence with more complex AV conduction abnormalities.
• The findings may contribute to improved diagnostic criteria and therapeutic strategies for patients with intricate cardiac arrhythmias.