Alternative names include Idiopathic Fascicular Left Ventricular Tachycardia (IFLVT), Belhassen-type VT, verapamil-sensitive VT.
Introduction
Fascicular VT was originally described by Zipes et al (1979) and treatment with verapamil was suggested by Belhassen et al (1981)
It is the second most common cause of idiopathic left ventricular tachycardia, which is defined as VT that occurs in patients without structural heart disease, metabolic abnormalities, or the long QT syndrome.
It typically occurs in young adult patients without structural heart disease and it predominantly affects men (60-80%)
Typical clinical presentation includes palpitations, dizziness or syncope. It usually occurs at rest but it can also be triggered by exercise, emotional stress and catecholamine infusion
It is a reentrant tachycardia with the reentry circuit comprising interventricular septum and fascicular system
ECG characteristics
monomorphic VT with typical features of VT such as AV dissociation, possible presence of fusion beats and other ECG signs
VT with a relatively narrow QRS complex that usually doesn’t exceed 140-150 ms and RS of 60-80 ms
Typically having RBBB morphology
Immediately after tachycardia termination, T wave inversion may be present.
Because of its narrow QRS complex morphology it can be mistaken for SVT conducted with aberrancy. It must also be distinguished from other narrow complex VTs.
Classification
a) Posterior fascicular ventricular tachycardia - is the most common type (90-95% of cases) and it uses the posterior fascicle as part of its circuit. It is characterised by RBBB morphology and left axis deviation.
b) Anterior fascicular ventricular tachycardia - is less frequent and it uses the anterior fascicle as part of its circuit. It is characterised by RBBB morphology and right axis deviation.
c) Upper septal fascicular ventricular tachycardia is a rare variant that usually presents as RBBB morphology but cases resembling LBBB have been described.
Management
In acute situations when the patient is hemodynamically unstable and/or does not tolerate the IFLVT, electrical cardioversion is recommended
In case when the patient does not require electrical cardioversion, administration of verapamil is effective in terminating the arrhythmia
IFLVT usually does not respond to vagal manoeuvres, adenosine or beta blockers
Currently recommended first-line treatment is catheter ablation in experienced centres. This is based on the fact that long-term verapamil treatment is not effective. Success rate of catheter ablation is 85-95% and recurrence is present in 0-20% of patients
ECG 1AMonomorphic VT (posterior fascicular ventricular tachycardia) with a ventricular rate of 176/min and a narrow QRS (116ms), RBBB morphology + left axis deviation
ECG 1B VT after termination
ECG 2 Monomorphic VT (posterior fascicular ventricular tachycardia) with a ventricular rate of 174/min and QRS duration of 128ms, RBBB morphology + left axis deviation
References
Idiopathic fascicular left ventricular tachycardia, An article from the E-Journal of the ESC
Council for Cardiology Practice Vol. 9, N° 13 - 20 Dec 2010, Dr. Sara Moreno Reviriego
Zipes D. P., Foster P. R., Troup P. J. et al. Atrial induction of ventricular tachycardia: reentry versus triggered automaticity. Am J Cardiol, 1979. 44: 1-8. 10.
Belhassen B., Rotmensch H. H., & Laniado S. Response of recurrent sustained ventricular tachycardia to verapamil. Br Heart J, 1981. 46: 679-82.
Kapa S, Gaba P, DeSimone CV, Asirvatham SJ. Fascicular Ventricular Arrhythmias: Pathophysiologic Mechanisms, Anatomical Constructs, and Advances in Approaches to Management. Circ Arrhythm Electrophysiol. 2017 Jan;10(1):e002476. doi: 10.1161/CIRCEP.116.002476. PMID: 28087563.
Silvia G Priori, Carina Blomström-Lundqvist, Andrea Mazzanti et al. ESC Scientific Document Group, 2015 ESC Guidelines for the management of patients with ventricular arrhythmias and the prevention of sudden cardiac death: The Task Force for the Management of Patients with Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death of the European Society of Cardiology (ESC) Endorsed by: Association for European Paediatric and Congenital Cardiology (AEPC), European Heart Journal, Volume 36, Issue 41, 1 November 2015, Pages 2793–2867, https://doi.org/10.1093/eurheartj/ehv316
