4:2:1 conduction of an AF initiating trigger.

Area of Science:

• Cardiology
• Electrophysiology
• Cardiac Arrhythmias

Background:

• Idiopathic dilated cardiomyopathy can be associated with complex atrial arrhythmias.
• Persistent atrial fibrillation (AF) management often involves catheter ablation.
• Unusual conduction patterns can complicate arrhythmia ablation procedures.

Purpose of the Study:

• To report a case of unusual 4:2:1 conduction of superior vena cava (SVC) tachycardia during AF ablation.
• To describe the electrophysiological mechanism linking SVC tachycardia to AF initiation and maintenance.
• To demonstrate the efficacy of targeted ablation of the SVC focus for rhythm restoration.

Main Methods:

• Electrophysiological study in a patient with idiopathic dilated cardiomyopathy undergoing AF ablation.
• Mapping of earliest activation during a regular narrow complex rhythm post-antral ablation.
• Analysis of conduction ratios from SVC focus to atria and ventricles.
• Catheter ablation of the identified SVC focus.

Main Results:

• Following antral ablation, AF terminated into a regular narrow complex rhythm originating from the SVC.
• An unusual 4:2:1 conduction pattern of SVC tachycardia to the ventricles was observed.
• 1:1 conduction of SVC tachycardia to the atrium preceded AF initiation, and SVC tachycardia continued during AF.
• Catheter ablation of the SVC focus successfully restored sinus rhythm.

Conclusions:

• Superior vena cava (SVC) tachycardia with 4:2:1 conduction can manifest during AF ablation.
• Targeted ablation of the SVC focus is effective in terminating this unusual arrhythmia and restoring sinus rhythm.
• Understanding complex conduction patterns is crucial for successful arrhythmia ablation.