Fasciculoventricular Pathway Mimicking Wolff-Parkinson-White Syndrome

Figures

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  Visual Summary. FVP Mimicking Wolff-Parkinson-White Syndrome The key electrocardiographic and electrophysiological features of an FVP are summarized. Despite subtle ventricular preexcitation on surface electrocardiography, a fixed HV interval is consistently observed during sinus rhythm, atrial pacing, atrial extrastimulus pacing, and junctional rhythm. Recognition of this benign pathway is essential to avoid unnecessary ablation near the His-Purkinje system. AVN = Atrioventricular Node; FVP = fasciculoventricular pathway; HV = His-ventricular LBB = Left Bundle Branch; RBB = Right Bundle Branch.

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  Figure 1. Baseline 12-Lead Electrocardiogram Baseline sinus rhythm demonstrating a short PR interval (115 milliseconds) with subtle ventricular preexcitation. The QRS complex is isoelectric in lead V1, with small positive delta waves in leads V5 and V6. Overall QRS duration is near normal.

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  Figure 2. Baseline His-Ventricular Interval Intracardiac electrograms during sinus rhythm demonstrating a fixed His-ventricular interval of 28 milliseconds.

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  Figure 3. Fixed His-Ventricular Interval With Decremental Atrial Pacing Intracardiac recordings during atrial pacing with 400-millisecond (left panel) and 360-millisecond (right panel) pacing rates. Despite increasing atrial rates, the His-ventricular interval remains unchanged, consistent with a fasciculoventricular pathway.

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  Figure 4. Atrial Extrastimulus Testing Demonstrating atrial-His Decrement With Fixed His-Ventricular Interval Atrial extrastimulus pacing (600/580, 600/480, and 600/420 milliseconds) demonstrating progressive atrial-His prolongation without disappearance of ventricular preexcitation, indicating atrioventricular nodal decremental conduction. Blue asterisks mark the His-ventricular interval, which remained constant at 29 milliseconds during all pacing maneuvers.

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  Figure 5. Loss of Preexcitation With Emergence of Complete Right Bundle Branch Block At an atrial pacing cycle length of 600/400 milliseconds, ventricular preexcitation disappears and the QRS complex transitions to a complete right bundle branch block morphology, reflecting functional right bundle branch refractoriness. Asterisks mark the HV interval for each beat. The HV interval measures 29 milliseconds in the preexcited beat and 48 milliseconds in the non-preexcited beat. In the preexcited beat, delta waves are most prominent in leads V5 and V6. HV = His-ventricular.

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  Figure 6. Fixed His-Ventricular Interval During Junctional Rhythm Intracardiac recordings during junctional rhythm demonstrating a persistently fixed His-ventricular interval of 29 milliseconds, further supporting the diagnosis of a fasciculoventricular pathway. Asterisks mark the His-ventricular interval for each beat.