Ventricular activity during atrial fibrillation. Studies with His bundle electrography.

Area of Science:

• Cardiology
• Electrophysiology
• Cardiac Arrhythmias

Background:

• Atrial fibrillation (AF) is a common arrhythmia.
• Understanding conduction patterns during AF is crucial for diagnosis and management.
• His bundle electrograms provide detailed insights into cardiac electrical activity.

Purpose of the Study:

• To investigate the electrophysiological characteristics of His bundle activity during atrial fibrillation.
• To identify the potential for concealed conduction within the His-Purkinje system during AF.
• To differentiate various ventricular and supraventricular beats on His bundle tracings in AF patients.

Main Methods:

• His bundle electrograms were recorded in 12 patients diagnosed with atrial fibrillation.
• Analysis focused on identifying dominant rhythms, ventricular, fascicular, and junctional beats.
• H-V intervals were assessed during episodes of sinus rhythm.

Main Results:

• Atrial fibrillation was the dominant rhythm in 11 out of 12 patients.
• One patient exhibited fascicular tachycardia, possibly due to digitalis toxicity.
• Ventricular, fascicular, and junctional beats were recognizable on His bundle tracings, despite similar QRS morphology to conducted beats in AF.
• The His-ventricular (H-V) interval remained stable when sinus rhythm occurred.

Conclusions:

• His bundle electrograms can detect distinct ventricular and fascicular beats during atrial fibrillation, even with similar QRS morphology.
• Concealed penetration of atrial impulses into the fascicular system can occur in patients with atrial fibrillation, especially those not treated with digitalis.
• These findings refine our understanding of cardiac conduction during complex arrhythmias.