Left anterior fascicular ventricular tachycardia

A 23 years old male came with the history of palpitation of one-hour duration. There was no history of giddiness, syncope dyspnoea or past history of any heart diseases. ECG of the patient is shown below.

ECG during tachycardia (Click on the ECG to enlarge it) 

ECG is showing wide complex regular tachycardia at heart rate of 186 beats per minute, there is right axis deviation, QRS morphology is RBBB, QRS duration 200 msec, visible P wave are seen after QRS merged into the ST-segment, there was no capture beat no fusion beat seen, there was no AV dissociation seen. So ECG diagnosis was wide complex tachycardia with a possibility of either supraventricular tachycardia or ventricular tachycardia arising from left posterior fascicule.

 Sinus ECG of the patient

Sinus ECG is showing normal sinus rhythm at a rate around 78 beats per minutes, normal axis, No ST-T wave changes seen.

The patient underwent electrophysiological study which showed left anterior fascicular tachycardia. The patient underwent successful radiofrequency ablation.

Let's discuss how to approach in patient with wide complex tachycardia

A Little bit about Fascicular tachycardia.

Idiopathic fascicular left ventricular tachycardia (IFLVT) is the most common idiopathic ventricular tachycardia of left ventricle. It is characterized 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 occurs mainly in young adults (15 to 40 years) and mainly affects males (60-80%0. The 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.

Electrocardiographic 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 characterized by right bundle branch block (RBBB) morphology and left axis suggesting that the exit of the circuit is located in the inferoposterior septum.It occurs 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 the morphology of left bundle branch block have also been described. 

Thank you

Praveen Gupta