Idiopathic fascicular left ventricular tachycardia (IFLVT)

A 13 year old female came to JIPMER hospital, Pondicherry India with chief complaints of acute onset palpitation of 2 hours duration. Patient was giving history of two episode of similar  palpitation over the last 6 months for which she was admitted at private hospital. Last episode of palpitation was treated with DC cardioversion. During the time of admission patient pulse was 190 beats per minute, regular, normal volume. Her Blood pressure was 110/80 mmhg, RS was normal, CVS was normal, ECHO heart of the patient was normal. ECG of the patient done in the emergency department is shown below.

ECG during the episode of tachycardia

Broad complex, regular tachycardia at the rate of 190 beats per minute, QRS duration 120 msec, Left axis deviation, there is rS complexes seen in lead II,III,avF suggestive of left anterior hemiblock pattern, QRS complex were of RBBB morphology in lead V1, V2, P wave are seen intermittently merged into the qrs complexes, there is complete AV dissociation but no capture beat no fusion beat seen. So the ECG is suggestive of ventricular tachycardia originating from left ventricle, most likely left posterior fascicular tachycardia.


Another tachycardia ECG of the patient

Tachycardia ECG of the patient

Patient was given injection verapamil, following which her tachycardia subsided. Her sinus ecg is shown below.

ECG is showing sinus rhythm at 75 beats per minute, normal axis, T wave inversion was seen in lead II,III,avF, V3-V6 suggestive of cardiac memory T waves.

Patient underwent electrophysiology study which conform our diagnosis. Patient underwent successful radiofrequency ablation. Later she was discharged in stable condition.

So the final diagnosis if Idiopathic fascicular left ventricular tachycardia

Lets discuss about idiopathic fascicular left ventricular tachycardia

Idiopathic fascicular left ventricular tachycardia (IFLVT) is the most common idiopathic ventricular tachycardia of left ventricle. It  is characterised by right bundle branch block (RBBB) morphology and left axis deviation on the ECG. The QRS duration during the time of tachycardia is relatively narrow.  This tachycardia is highly sensitive to verapamil. It is originating near the posterior fascicle.

It occur mainly in young adults (15 to 40 years) and mainly affects males (60-80%0. Patient most frequently present with paroxysmal episodes of palpitation. Although most episodes occur at rest, exercise, emotional stress and catecholamine infusion can act as triggers.

Electrocardiographical features

Baseline ECG is normal in most patient though it may present T-wave inversion immediately after tachycardia (cardiac memory).

 IFLVT usually shows a QRS complex duration inferior to 140-150 ms and fast initial forces (RS interval of 60-80 ms). 

The ECG varies depending on the site of origin of the tachycardia:

1. Posterior fascicular ventricular tachycardia (P-IFLVT). It is characterised by right bundle branch block (RBBB) morphology and left axis suggesting that the exit of the circuit is located in the inferoposterior septum.It occur in 90-95% of cases. 
2. Anterior fascicular ventricular tachycardia (A-IFLVT). It is the second variant in terms of frequency. Its ECG pattern typically shows RBBB morphology and right axis. The earliest activation has been described in the anterolateral wall of the left ventricle.
3. Upper septal fascicular ventricular tachycardia. This presentation is exceptional. As a general rule, it presents RBBB but a few cases with morphology of left bundle branch block have also been described. 

Thank you

Praveen Gupta