Idiopathic Fascicular Ventricular Tachycardia
A 42-year-old man with no prior cardiac history presented to the emergency department after experiencing a syncopal episode a few hours after a 20-minute run.
At presentation, he had a heart rate of 189 beats/min and blood pressure of 100/59 mm Hg. Electrocardiography results revealed a wide-complex tachycardia, with a QRS duration of 124 milliseconds, a right bundle-branch block pattern, and left axis deviation (Figure 1).
The disconjugate P waves noted in lead II suggested ventricular tachycardia, differentiating it from supraventricular tachycardia (SVT) with bifascicular block. The short intrinsicoid deflection in lead V1 of less than 45 milliseconds, typically seen in a sinus rhythm, implied that the origin of the ventricular tachycardia was in the His-Purkinje system. The pattern was consistent with left posterior fascicular tachycardia.
Three consecutive doses of adenosine had no effect. Amiodarone, 300 mg intravenously, was given with successful conversion to normal rhythm (Figure 2). Results of a resting echocardiogram were normal, with no inducible ventricular tachycardia on the stress portion.
The clinical picture was consistent with idiopathic posterior fascicular left ventricular tachycardia, also known as Belhassen ventricular tachycardia, a very rare arrhythmia that can be confused with SVT due to its relatively narrow QRS complex.1,2
Verapamil, the standard treatment for this tachycardia, was initiated in our patient but was not tolerated due to a hypotensive response. He was referred to an electrophysiologist for consideration of possible cardiac ablation in the future.
References:
- Morgera T, Hrovatin E, Mazzone C, Humar F, De Biasio M, Salvi A. Clinical spectrum of fascicular tachycardia. J Cardiovasc Med (Hagerstown). 2013;14(11):791-798.
- Metzner A, Ouyang F, Wissner E, Kuck K-H. Monomorphic and polymorphic ventricular tachycardias arising from the His-Purkinje system: what do we know? Future Cardiol. 2011;7(6):835-846.