1) Fascicular ventricular tachycardia is the most common form of idiopathic ventricular tachycardia originating from the left ventricle. It typically presents in young patients without structural heart disease. 2) It has characteristic ECG features including a monomorphic ventricular rhythm with fusion complexes and AV dissociation. The QRS duration is between 100-140 ms with a short RS interval of 60-80 ms. It also shows a right bundle branch block pattern and axis deviation. 3) Posterior fascicular ventricular tachycardia, which arises near the left posterior fascicle, shows a right bundle branch block pattern with left axis deviation. Anterior fascicular ventricular tachycardia arises

1. Domina Petric, MD
ECG F

2. Fascicular VT
Burns E. Idiopathic Fascicular Left Ventricular Tachycardia (April 4, 2017).
Retrieved from https://lifeinthefastlane.com/ecg-library/fascicular-vt/

3. Fascicular VT
Synonyms are:
• fascicular tachycardia
• Belhassen-type VT
• verapamil-sensitive VT
• infrafascicular tachycardia
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4. Fascicular VT
Fascicular tachycardia is the most common
idiopathic VT of the left ventricle.
It is a re-entrant tachycardia, typically seen in
young patients without structural heart disease.
Verapamil is the first line treatment.
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5. ECG features
Monomorphic
ventricular
tachycardia with
fusion complexes, AV
dissociation and
capture beats.
QRS duration is
100-140 ms.
Short RS interval
of 60-80 ms.
The RS interval is
usually >100 ms in
other types of VT.
RBBB pattern.
Axis deviation!
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6. Classification
• Posterior fascicular VT (90-95%) arises close to the
left posterior fascicle: RBBB morphology + left axis
deviation.
• Anterior fascicular VT (5-10%) arises close to the left
anterior fascicle: RBBB morphology + right axis
deviation.
• Upper septal fascicular VT (rare) arises from the
region of the upper septum: usually RBBB (or LBBB
instead), narrow QRS and normal axis have also
been reported.
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7. Note!
Posterior fascicular VT
• Left axis deviation!
Explanation: impulses
arise close to the left
posterior fascicle.
Posterior left hemiblock
• Right axis deviation!
Explanation: impulses
are conducted to the
left ventricle via the
left anterior fascicle.
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Conclusion: when impulses arise close to or are conducted via the left posterior fascicle,
there is left axis deviation (the posterior fascicle is directed toward the left ventricle).

8. Note!
Anterior fascicular VT
• Right axis deviation!
Explanation: impulses
arise close to the left
anterior fascicle.
Anterior left hemiblock
• Left axis deviation!
Explanation: impulses
are conducted to the
left ventricle via the
left posterior fascicle.
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Conclusion: when impulses arise close to or are conducted via the left anterior fascicle,
there is right axis deviation (the anterior fascicle is directed toward the right ventricle).

9. Rebel EM
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10. Posterior fascicular VT
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There is left axis deviation (if it was hemiblock, it would have been left anterior fascicular block).
RBBB morphology

11. Fusion beat
Burns E. Fusion Beats (July 19, 2018). Retrieved from
https://lifeinthefastlane.com/ecg-library/basics/fusion-beats/
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12. Fusion beat
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13. Fusion beats are seen with:
• Ventricular tachycardia
• Accelerated idioventricular rhythm
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14. Literature
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