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Fascicular VT — EECC MCQ

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HardArrhythmia & ElectrophysiologyFascicular VTEECC

A 35-year-old man presents with palpitations and a broad-complex tachycardia at 200 bpm with left axis deviation and a relatively narrow QRS morphology (130 ms) consistent with an RBBB pattern. The tachycardia responds to intravenous verapamil. What is the most likely diagnosis?

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Correct answer: A — Left posterior fascicular VT (Belhassen VT) — a verapamil-sensitive idiopathic VT

Fascicular VT (also known as Belhassen VT or idiopathic left ventricular tachycardia) originates from the left posterior fascicle and has characteristic features: RBBB morphology with left axis deviation (left posterior fascicular VT) or right axis deviation (left anterior fascicular VT), relatively narrow QRS (typically 120-140 ms), and response to intravenous verapamil (which is unique among VTs and differentiates it from other causes). It occurs in structurally normal hearts, predominantly in young men. The re-entrant circuit involves the Purkinje fibres. Catheter ablation is curative with >90% success rates. This VT is important to recognise as verapamil would be harmful in most other VTs.

Reference: ESC (2022): Guidelines on Ventricular Arrhythmias and Prevention of Sudden Cardiac Death