What does this research mean for the field?

Invasive electrophysiological study findings largely consistent with a fasciculoventricular pathway in a patient, yet the absence of tachycardia raises diagnostic ambiguity. Novelty: ClaimNovelty.NOVEL_FINDING. Consensus alignment: ConsensusAlignment.CHALLENGES_CONSENSUS.

What question did this study set out to answer?

The report aims to illustrate diagnostic challenges in identifying fasciculoventricular pathways using invasive electrophysiological studies.

February 8, 2026Open Access

Conflicting Invasive Electrophysiological Study Results in a Suspected Fasciculoventricular Pathway: A Case Report

Key Result

An invasive EPS in a 23-year-old with suspected fasciculoventricular pathway showed atypical findings suggesting a novel upper FVP insertion site and supported conservative management.

Key Points

The report aims to illustrate diagnostic challenges in identifying fasciculoventricular pathways using invasive electrophysiological studies.
Conducted an invasive electrophysiological study on a 23-year-old patient with preexcitation phenomena.
Analyzed resting surface ECG for preexcitation patterns.
Evaluated junctional beats and HV-interval changes to understand conduction pathways.
Electrophysiological findings largely supported fasciculoventricular pathway diagnoses but included atypical features.
Observed loss of preexcitation during junctional beats with normalized HV-interval.
No tachycardia was inducible, and no evidence of retrograde conduction through accessory pathways was found.

Structured PICO

Population

A 23-year-old patient with a history of brief, weekly episodes of palpitations and a resting surface ECG demonstrating a preexcitation pattern suggestive of either a parahisian or fasciculoventricular pathway.

Intervention

Invasive electrophysiological study (EPS) followed by conservative, observational management

This case highlights the diagnostic ambiguity of fasciculoventricular pathways during invasive electrophysiological studies, underscoring the need for refined diagnostic criteria.

Main Result

Absolute Event Rate: 0% vs 0%

Abstract

Abstract Background Fasciculoventricular pathways (FVP) are variants of preexcitation syndrome with uncertain prevalence in the human heart. This case report presents findings from an invasive electrophysiological study (EPS) that mostly fulfill the established diagnostic criteria for FVP, but also exhibit atypical features, highlighting diagnostic ambiguity in clinical practice. Case Summary A 23-year-old patient presented with a history of brief, weekly episodes of palpitations. The resting surface ECG demonstrated a preexcitation pattern suggestive of either a parahisian or fasciculoventricular pathway. The EPS findings were largely consistent with a FVP. During junctional beats, we observed a loss of preexcitation and normalization of HV-interval. No tachycardia was inducible, and there was no evidence of retrograde conduction via an accessory pathway. Discussion Three potential anatomical locations of the upper FVP take-off side were considered: (1) a single FVP originating from the lower part of the His-bundle or (2) a single FVP originating close to the upper, junctional part of the His-bundle or even from the distal part of the AV-node and (3) the presence of an additional second accessory pathway. Based on the above-mentioned evidence, the second anatomical location of the upper FVP-insertion was most likely, differing from previous findings of FVP in the literature. A conservative, observational management strategy was adopted. Current diagnostic criteria for FVP are based on retrospective studies and case reports, lacking prospective validation. This case underscores the need for further research to refine the diagnostic approach to FVP and improve risk stratification in such patients.