Last update: April 2020

  This type of ventricular tachycardia (VT) is also called as Belhassen type VT since Belhassen et al. first reported that it was sensitive to Verapamil .



Etiology

  This is a Purkinje-related arrhythmia. It is seen usually in patients with structurally normal heart.

  This arrhythmia originates from the left ventricle (LV).

  Usually,
reentry is the mechanism of this tachycardia. Rarely, non-reentrant mechanism may be involved.

  Generally occurs at rest, but exercise or emotional stress may also trigger this VT.




Diagnostic criteria

  Morphology of the VT is right bundle branch block (RBBB) and left axis deviation.

  When there is no VT, the basal ECG is generally normal.

  In some patients, ECG recorded after the fascicular VT attack may show T wave negativity (
T wave memory).

  These patients usually do not have any accompanying cardiac diseases.

  Unlike the more common ischemic VT, fascicular VT does not respond to lidocaine.




Classification of Fascicular VTs according to the point of origin

  Left posterior fascicular VT (LPF VT): is the most common type.

  Left anterior fascicular VT (LAF VT)

  Left upper septal VT (septal VT)




  Left Posterior Fascicular (LPF) VT is frequently misdiagnosed as supraventricular tachycardia (SVT) with RBBB and left anterior hemiblock aberrancy.



ECG features that suggest Left Posterior Fascicular (LPF) VT
(These criteria do not have 100% sensitivity or specificity. In the absence of atrioventricular dissociation or fusion/capture beats, achievement of correct diagnosis is difficult.)

  46% have atypical QRS morphology in lead V1: no rsR’, or R larger than R’. Only about 54% of LPF VT patients have typical RBBB morphology in V1. Initial q wave preceding typical rsR' pattern in lead V1 suggests LPF-VT.

  QRS width <140 ms.

  V6 R/S ratio <1.

  Positive QRS complex in aVR. Most patients with LPF-VT have qR complex in aVr. The q wave is narrower than 40 ms.




ECG features that suggest SVT with RBBB and Left Anterior Hemiblock (LHB) aberrancy:
(these criteria do not have 100% sensitivity or specificity)

  Typical QRS morphology in lead V1. In V1, S wave below the isoelectric line supports aberrancy.

  QRS width >140 ms.

  V6 R/S ratio >1.

  Negative QRS complex in aVR.



A possible differential diagnosis of LPV-VT is posterior papillary muscle (PPM)-VT. Probably an overlap probably exists between the ECG findings of LPF-VT and fascicular VT originating from the PPM.


ECG features that suggest left posterior papillary muscle (PPM)-VT:

  Mean QRS duration is 142 ms. in patients with PPM-VT (whereas 127 ms. in patients with LPF-VT).

  QRS width >160 ms. is the most reliable parameter that supports PPM-VT. This is very rare in LPF-VT.

  Spontaneous variable QRS morphologies occur more often among patients with PPM-VT.

  PPM-VT is not verapamil sensitive.




ECG characteristics of Non-Reentrant Fascicular Tachycardia (NRFT)

  During VT, QRS duration is relatively narrow (123 ± 12 ms).

  VT exhibited may be RBBB or left bundle branch block (LBBB) configuration.

  Usually, NRFT exhibits RBBB configuration and superior axis, consistent with its origin from the LPF.

  To a lesser extent, it exhibits RBBB configuration and inferior axis, indicating its origin from the left anterior fascicle.

  Rarely, VT may exhibit LBBB and superior axis configuration, indicating RV origin.




Clinical significance of Fascicular VT

  Left Posterior Fascicular (LPF) VT is frequently misdiagnosed as supraventricular tachycardia with aberrant right bundle branch block (RBBB) and left anterior hemiblock (LAHB).

  During a fascicular VT attack, the patient usually complains of palpitation, fatique, dizziness or dyspnea.

  Syncope or sudden cardiac death is very rare. It is uaually considered as benign in its clinical course.

  Since the QRS complex is not so wide, fascicular VT may be easily mistaken for SVT.

  Unlike SVT, fascicular VT does not respond to adenosine or vagal maneuvers.

  Unlike the common ischemic VT, fascicular VT does not respond to lidocain.

 
Atrial or ventricular pacing may initiate this tachycardia.

  Generally occurs at rest. Exercise or emotional stress may also trigger this arryhthmia.




References

  J Electrocardiol 2018;51:874-878.

  Circ Arrhythm Electrophysiol. 2017;10:e005074. DOI: 10.1161/CIRCEP.117.005074

  Circ Arrhythm Electrophysiol 2016;9.pii: e004177. DOI: 10.1161/CIRCEP.116.004177.

  Pacing Clin Electrophysiol 2011;34:624-650.

  Am J Emerg Med 2007;25:572-575.

  Circulation 2002;105:462-469.

  Ann Emerg Med 1998;31:406-409.

  Am Heart J 1994;128:147-156.

  Circulation 1990;82:1561-1573.

  Br Heart J 1981;46:679-682.





ECG 1a. The basal ECG of the patient is seen above. No ventricular tachycardia (VT).

Prof. Dr. Bernard Belhassen has donated the above ECG to our website.

Click here for a more detailed ECG




ECG 1b. The same patient's ECG during fascicular VT showed right bundle branch block (RBBB) and left axis deviation.

Prof. Dr. Bernard Belhassen has donated the above ECG to our website.

Click here for a more detailed ECG




ECG 1c. Pacing from right ventricular apex in the same patient induced VT with RBBB morphology and right axis deviation.

Prof. Dr. Bernard Belhassen has donated the above ECG to our website.

Click here for a more detailed ECG




ECG 1d.

Prof. Dr. Bernard Belhassen has donated the above ECG to our website.

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ECG 1e. Left ventricular pacing in the same patient resulted in a VT attack with RBBB and right axis deviation.

Prof. Dr. Bernard Belhassen has donated the above ECG to our website.

Click here for a more detailed ECG




ECG 1f. Final ECG after a total of 6 RF (radiofrequency) pulses shows that the VT attack is terminated.

Prof. Dr. Bernard Belhassen has donated the above ECG to our website.

Click here for a more detailed ECG





ECG 2a. Above is an ECG from a patient with Belhassen type VT (verapamil-sensitive VT, fascicular VT). Limb leads are seen.
The ECG is recorded at a paper speed of 50mm/second.

Dr. Peter Kukla has donated the above ECG to our website.

Click here for a more detailed ECG




ECG 2b. The same patient's chest leads are seen above. The above ECG is recorded at a paper speed of 50 mm/second.

Dr. Peter Kukla has donated the above ECG to our website.

Click here for a more detailed ECG




ECG 2c. The same patient's ECG after fascicular VT has been terminated.
The T wave negativity in inferior leads and C4-to-C6 denote to T wave memory effect.

Dr. Peter Kukla has donated the above ECG to our website.

Click here for a more detailed ECG





ECG 3. Above is an ECG from a patient with idiopathic left posterior fascicular VT.

Asst. Prof. Dr. Jorge Romero has donated the above ECG to our website.

Click here for a more detailed ECG