Retrograde ventriculoatrial jump-What is the mechanism?

Area of Science:

• Electrophysiology
• Cardiology
• Cardiac Electrophysiology

Background:

• Ventricular extra stimuli (VES) are crucial for diagnosing accessory pathways (AP).
• VA jump phenomenon during electrophysiological studies indicates complex conduction patterns.
• Retrograde conduction abnormalities, including bundle branch block, can influence VA intervals.

Purpose of the Study:

• To elucidate the mechanism of a VA jump during a VES protocol.
• To differentiate between accessory pathway-mediated and pure nodal retrograde conduction.
• To investigate the role of retrograde RBBB in the observed electrophysiological findings.

Main Methods:

• Electrophysiological study utilizing ventricular extra stimuli (VES) at varying intervals (500/270 ms and 500/260 ms).
• Analysis of His (H) signal timing relative to atrial electrogram (A-EGM) and ventricular electrogram (V-EGM).
• Assessment of retrograde conduction pathways, including accessory pathways and the AV node-His-Purkinje system.

Main Results:

• A VA jump was observed during the VES protocol, with His signal latency suggesting accessory pathway involvement.
• Pure nodal VA conduction was ruled out, confirming the presence of an accessory pathway (AP).
• Retrograde conduction via the accessory pathway, followed by block in the left bundle-His-node due to retrograde RBBB, was identified. At shorter VES intervals, conduction shifted to the AV node, demonstrating a jump from AP to AV node.

Conclusions:

• The VA jump phenomenon in this case was attributed to a transition from accessory pathway conduction to AV node conduction.
• Retrograde RBBB significantly impacted the His signal timing and conduction patterns.
• Electrophysiological study with VES is effective in characterizing complex retrograde conduction mechanisms involving accessory pathways.