Sequential Bilateral Bundle Branch Block During Dofetilide, A New Class III Antiarrhythmic Agent, In a Patient with Atrial Fibrillation

Sequential Bilateral BBB During Dofetilide. Introduction: I in mechanism of wide QRS complex tachycardias during dofetilide infusion was studied in a patient with atrial fibrillation.
Methods and Results: Endocardial recording from the intraventricular conduction system showed that dofetilide caused "classic" aberrant conduction (Ashman phenomenon, typical QKS morphology) at high prematurity ratios (preceding interval = 1.78 X coupling interval 290), thus mimicking ventricular ectopy. In addition, there was frequent sequential bilateral bundle branch block, caused by a significant difference in preceding bundle-to-bundle intervals (mean difference ± 1 SD: 74 ± 26 msec).
Conclusion: The present findings may prove helpful in the clinical assessment of wide QKS complex rhythms after dofetilide and possibly other "pure" Class III antiarrhythmics.