Abstract 14411: Block in the Fasciculoventricular Pathway in a Complex Arrhythmia Presentation

Abstract

Background: Fasciculoventricular pathway (FVP) is a rare form of preexcitation without known clinical tachycardia. As it is connected to the His bundle, they conduct whenever it is engaged. Conduction through the His Bundle but block at FVP has not been reported. Case presentation: We present a case of a 42-year-old male with a history of Wolff-Parkinson-White syndrome (WPWS), supraventricular tachycardia (SVT), syncope, embolic stroke, paroxysmal atrial fibrillation, hypertension, hypothyroidism, Sjogren's syndrome and prior unsuccessful attempts at elimination of the preexcitation. He underwent electrophysiology (EP) study for presumed SVT ablation. The EP study identified an FVP as the cause of preexcitation, and the planned accessory pathway ablation was deemed unnecessary. Atrial tachycardia originating from the right superior pulmonary vein (PV) was induced, eventually degenerating into atrial fibrillation, and the patient successfully underwent pulmonary vein isolation with the resolution of symptoms. Discussion: FVP is usually an incidental finding when patients with symptomatic preexcitation are studied. If tachycardia is induced, it is unrelated to the preexcitation. The FVP is connected to the His bundle and invariably conducts if the impulse engages the His Bundle. We are unaware of a case when the His bundle conducts, but the impulse loses preexcitation due to a block in the FVP. This unusual finding was noted in our case. To further confirm the location of the accessory pathway, IV adenosine was given with a complete heart block suggesting the preexcitation is beyond the level of the AV node and within the conduction system. It is not at the annulus with independent atrial and ventricular insertion, typical of an accessory pathway. Conclusions: This case demonstrates an FV pathway's unusual conduction block and physiological characteristics.