Key result
Baseline fascicular block does not alter VT QRS duration compared to no block.
Why the study?
The involvement of the fascicle of the left bundle branch in the reentrant circuit of verapamil-sensitive idiopathic left ventricular tachycardia with RBBB configuration remains unclear and understudied.
Observational (n=49)
Absolute Event Rate: 141% vs 140%
p-value: p=0.78
The fascicle of the left bundle branch may not be involved in the antegrade limb of the reentry circuit in idiopathic left VT, as QRS duration and transitional zones during VT were similar regardless of baseline fascicular block.
May not involve left bundle fascicles in antegrade reentry of verapamil-sensitive VT; leaves open precise circuit mapping before changing ablation targets.
The exact reentrant circuit of the verapamil-sensitive idiopathic left VT with a RBBB configuration remains unclear. Furthermore, if the fascicle of left bundle branch is involved in the reentrant circuit has not been well studied. Forty-nine patients with verapamil-sensitive idiopathic left VT underwent electrophysiological study and RF catheter ablation. Group I included 11 patients (10 men, 1 woman; mean age 25 +/- 8 years) with left anterior fascicular block (4 patients), or left posterior fascicular block (7 patients) during sinus rhythm. Group II included 38 patients (29 men, 9 women; mean age 35 +/- 16 years) without fascicular block during sinus rhythm. Duration of QRS complex during sinus rhythm before RF catheter ablation in group I patients was significant longer than that of group II patients (104 +/- 12 vs 95 +/- 11 ms, respectively, P=0.02). Duration of QRS complex during VT was similar between group I and group II patients (141 +/- 13 vs 140 +/- 14 ms, respectively, P=0.78). Transitional zones of QRS complexes in the precordial leads during VT were similar between group I and group II patients. After ablation, the QRS duration did not prolong in group I or group II patients (104 +/- 11 vs 95 +/- 10 ms, P=0.02); fascicular block did not occur in group II patients. Duration and transitional zone of QRS complex during VT were similar between the two groups, and new fascicular block did not occur after ablation. These findings suggest the fascicle of left bundle branch may be not involved in the antegrade limb of reentry circuit in idiopathic left VT.
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KUO et al. (2003) conducted an observational in Verapamil-sensitive idiopathic left ventricular tachycardia (n=49). Fascicular block during sinus rhythm vs. No fascicular block during sinus rhythm was evaluated on Duration of QRS complex during VT (p=0.78). Baseline fascicular block did not affect QRS duration during ventricular tachycardia compared to no block (141 vs 140 ms, P=0.78), suggesting the fascicle is not involved in the reentry circuit.
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