Typical Atrioventricular Nodal Re-entrant Tachycardia With Fasciculo-Ventricular Bypass Tract: Diagnostic and Therapeutic Challenges.

BACKGROUND

Fasciculo-ventricular bypass tracts (FVBTs) are uncommon, atypical bypass tracts (BTs) that may co-exist with other supra-ventricular tachycardias (SVTs). These BTs themselves do not require treatment.

CASE SUMMARY: A 45-year-old male presented with recurrent episodes of palpitations. Electrocardiography (ECG) during tachycardia revealed short RP SVT. Baseline ECG showed subtle ventricular pre-excitation. During a cardiac electrophysiology study, typical slow-fast atrio-ventricular nodal re-entrant tachycardia was induced, and fixed degree of ventricular pre-excitation on surface ECG and short and fixed H-V interval was observed. This finding suggested co-existence of a FVBT. Successful radio-frequency catheter ablation of slow pathway and the bystander was performed, and FVBT was not targeted for ablation.

DISCUSSION: FVBTs are uncommon variants of ventricular pre-excitation. Subtle ventricular pre-excitation on ECG hints toward the possibility of FVBT. Prevalence of FVBT is believed to be underestimated due to the lack of attention on ECG and electrophysiology characteristics. A unique combination of typical slow-fast atrio-ventricular nodal re-entrant tachycardia with an FVBT has been rarely reported.

TAKE-HOME MESSAGES: FVBT can keep company with other SVTs. Differentiation of FVBT from close mimics like anteroseptal BT and nodo-fascicular or nodo-ventricular BTs is essential as radio-frequency catheter ablation near the high-risk atrioventricular nodal region would be implicated to cure these BTs.