A 25-year-old man with structurally normal heart presents with recurrent episodes of wide-complex tachycardia at 200 bpm with RBBB morphology and left axis deviation. The tachycardia is terminated with verapamil 5 mg IV. What is the mechanism of this tachycardia?
- A Re-entry involving an accessory pathway
- B Triggered activity in the right ventricular outflow tract
- C Re-entry within the left posterior fascicle (fascicular VT) ✓
- D Automaticity in the His-Purkinje system
Correct answer: C. Re-entry within the left posterior fascicle (fascicular VT)
Explanation
Fascicular VT (Belhassen type) is a verapamil-sensitive VT with RBBB and left axis morphology, caused by re-entry involving the left posterior fascicle. It occurs in structurally normal hearts, typically in young males. The re-entry circuit involves the diseased posterior fascicle and adjacent ventricular muscle. Verapamil slows conduction in the fascicle and terminates the tachycardia.
Reference: Zipes and Jalife: Cardiac Electrophysiology, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.