Background-Atrial fibrillation (AF) may cause life-threatening ventricular
arrhythmias in patients with Wolff-Parkinson-White syndrome. We prospective
ly evaluated the effects of ibutilide on the conduction system in patients
with accessory pathways (AP).
Methods and Results-In part I, we gave ibutilide to 22 patients (18 men, 31
+/-3 years of age) who had AF during electrophysiology study, including 6
pediatric patients less than or equal to 18 years of age. Ibutilide termina
ted AF in 21 of 22 patients (95%) during or 8 +/-5 minutes after infusion a
nd prolonged the shortest preexcited R-R interval during AF. Successful abl
ation was performed in all patients. In part II, ibutilide was given to 18
patients ( 14 men, 28 +/- 21 years) to assess its effects on the AP and con
duction system. Ibutilide prolonged the antegrade atrioventricular node eff
ective refractory period (ERP) (from 252 +/- 60 to 303 +/- 70 ms; P <0.02).
Ibutilide caused transient loss of the delta wave in 1 patient and abolish
ed inducible tachycardia in 2 patients, although retrograde mapping still a
llowed for successful AP ablation. The antegrade AP ERP prolonged from 275
+/- 40 to 320 +/- 60 ms (P <0.01), as did the antegrade AP block cycle leng
th; the retrograde AP ERP and block cycle length similarly prolonged with i
butilide. The relative and effective refractory period of the His-Purkinje
system increased in 61% of patients after ibutilide. There were no adverse
side effects.
Conclusions-We report the use of ibutilide in terminating AP-mediated AF, i
ncluding the first report in the pediatric population. Ibutilide prolonged
refractoriness of the atrioventricular node, His-Purkinje system, and AP.