Idiopathic fascicular left ventricular tachycardia
Background
- Rare
- Also known as narrow complex ventricular tachycardia, fascicular tachycardia, Belhassen-type VT, verapamil-sensitive VT, or intrafascicular tachycardia
- Reentrant tachycardia seen typically in young patients without structural heart disease
Clinical Features
- Young adult
- Male (60-80%)[1]
- Palpitations
- Dizziness
- Syncope is infrequent
Differential Diagnosis
Narrow-complex tachycardia
- Regular
- AV Node Independent
- Sinus tachycardia
- Atrial tachycardia (uni-focal or multi-focal)
- Atrial fibrillation
- Atrial flutter
- Idiopathic fascicular left ventricular tachycardia
- AV Node Dependent
- AV Node Independent
- Irregular
- Multifocal atrial tachycardia (MAT)
- Sinus tachycardia with frequent PACs, PJCs, PVCs
- Atrial fibrillation
- Atrial flutter with variable conduction
- Digoxin Toxicity
Palpitations
- Arrhythmias:
- Non-arrhythmic cardiac causes:
- Psychiatric causes:
- Drugs and Medications:
- Alcohol
- Caffeine
- Drugs of abuse (e.g. cocaine)
- Medications (e.g. digoxin, theophylline)
- Tobacco
- Misc
Evaluation
- Assume ventricular tachycardia until proven otherwise
- Often misdiagnosed as SVT with aberrancy
- Look for specific features of VT
- fusion/capture beats
- AV dissociation
- ECG findings
- Monomorphic VT
- QRS duration <140 ms
- RS interval 60-80 ms
- Right Bundle Branch Block
- Axis deviation depending on classification
Classification
Posterior fascicular VT
- 90-95% of cases
- RBBB
- Left axis deviation
Anterior fascicular VT
- second most common
- RBBB
- Right axis deviation
Upper septal fascicular VT
- rare
- RBBB or LBBB
- Normal axis
Management
Unstable
Synchronized Cardioversion
- Adults: 0.5-1.0 J/kg
- Pediatrics: 0.5-1 J/kg
- If unsuccessful, increase to 2 J/kg
- Consider sedation prior to cardioversion only if it will not significantly delay the procedure
Stable
Verapamil
- 10 mg over 1 min
- Only administer in stable patients with an established diagnosis of IFLVT
Digoxin Immune Fab
- IFLVT as a result of Digoxin toxicity is responsive to digoxin immune Fab