A wide QRS complex tachycardia with different initiation patterns: what is the mechanism?

Area of Science:

• Cardiology
• Electrophysiology
• Cardiac Arrhythmias

Background:

• Electrophysiologic testing (EPS) is crucial for diagnosing cardiac arrhythmias.
• Wide QRS tachycardias can present diagnostic challenges, necessitating advanced testing.
• Isoproterenol infusion is often used during EPS to unmask underlying arrhythmias.

Observation:

• A 47-year-old male patient presented with palpitations and underwent EPS.
• Non-reproducible wide QRS tachycardias with an unusual H-A-V activation pattern were induced.
• Tachycardias exhibited consistent cycle length but varied initiation patterns, with earliest atrial activation near the His bundle.
• No dual atrioventricular (AV) nodal physiology was evident.

Findings:

• A definitive diagnosis of atrioventricular (AV) nodal reentrant tachycardia was not established.
• Slow pathway ablation was performed prophylactically to mitigate risks of inadvertent AV block.
• Repeat burst atrial pacing after ablation failed to induce any tachycardias.

Implications:

• This case highlights a rare presentation of wide QRS tachycardia potentially related to the AV node.
• Prophylactic slow pathway ablation may be considered in ambiguous cases to ensure patient safety.
• Further investigation into unusual activation patterns in wide QRS tachycardias is warranted.