Fascicular Ventricular Tachycardia: Initial Treatment Approach
For hemodynamically stable patients with fascicular VT, intravenous verapamil is the recommended first-line acute treatment, while catheter ablation should be considered as definitive first-line therapy for symptomatic patients, particularly in young individuals who would otherwise require lifelong medical therapy. 1, 2
Acute Pharmacologic Management
Hemodynamically Stable Patients
Administer intravenous verapamil as the acute treatment of choice for fascicular VT (also called left ventricular fascicular VT or verapamil-sensitive VT), which presents characteristically with right bundle branch block morphology and left axis deviation 1, 3
IV verapamil terminates fascicular VT in the majority of cases by blocking the slow conduction zone within the reentrant circuit 4, 3
Beta-blockers are an alternative acute option if verapamil is contraindicated or unavailable 1, 2
Note that some fascicular VT variants, particularly those originating from papillary muscles, may only slow rather than terminate with verapamil (responding in only 46% of cases in one series), making them less verapamil-sensitive than classic fascicular VT 5
Hemodynamically Unstable Patients
Perform immediate synchronized cardioversion if the patient presents with hypotension, altered mental status, or signs of shock 1, 6
Provide appropriate sedation before cardioversion if the patient is conscious 1
Definitive Management Strategy
Catheter Ablation as First-Line Therapy
Catheter ablation by experienced operators is recommended as first-line treatment for symptomatic patients with idiopathic left fascicular VT, with acute success rates exceeding 90% and recurrence rates of 0-20% 1, 2
This recommendation is particularly strong for young patients who would otherwise require decades of antiarrhythmic therapy 1
The ablation target is typically the site where mid-diastolic Purkinje potentials are recorded during tachycardia, representing the slow conduction zone of the reentrant circuit 4, 7
For left posterior fascicular VT (the most common subtype, comprising >90% of cases), ablation targets the distal left posterior fascicle region along the inferior left ventricular septum 1, 4
Long-Term Medical Management
Beta-blockers, verapamil, or class IC sodium channel blockers (flecainide or propafenone) are recommended when catheter ablation is not available, not desired by the patient, or has failed 1, 2
Chronic oral verapamil can prevent recurrences but may not be effective long-term in all patients 2
Avoid class IC agents in patients with any history of myocardial infarction or structural heart disease, as they are contraindicated in this population 6
Clinical Recognition and Diagnostic Pearls
ECG Characteristics
Left posterior fascicular VT (>90% of cases): Right bundle branch block morphology with superior axis (left axis deviation) and relatively narrow QRS complex (typically <140 ms) 1, 4, 7
Left anterior fascicular VT (<10% of cases): Right bundle branch block morphology with right axis deviation 1
The relatively narrow QRS duration distinguishes fascicular VT from most other forms of ventricular tachycardia 4, 8
Mechanism
Fascicular VT involves a reentrant circuit utilizing the Purkinje network, with a verapamil-sensitive slow conduction zone and fast Purkinje fiber conduction as the retrograde limb 4, 5
This mechanism explains both the characteristic ECG morphology and the unique responsiveness to verapamil 4, 3
Critical Pitfalls to Avoid
Do not administer adenosine expecting termination—fascicular VT does not respond to adenosine like supraventricular tachycardia does, though it may help diagnostically by ruling out SVT 3
Avoid confusing fascicular VT with supraventricular tachycardia with aberrancy, which can lead to inappropriate management; the relatively narrow QRS with RBBB pattern and specific axis deviation should raise suspicion for fascicular VT 3, 7
Do not use IV amiodarone as first-line therapy for fascicular VT when verapamil or beta-blockers are available, as these are more specific and effective for this arrhythmia 1
Be aware that contact inhibition during endocardial mapping can make the tachycardia non-inducible, which is a principal limiting factor during ablation procedures 7
Recognize that non-reentrant focal fascicular tachycardia exists as a rare variant (2.8% of idiopathic VT cases) that does not respond to verapamil and requires activation mapping rather than pacemap-guided ablation for successful treatment 8