Longitudinal QT stability and impact of baseline cardiac rhythm on discharge dose in dofetilide-treated patients.

INTRODUCTION

Dofetilide suppresses atrial fibrillation (AF) in a dose-dependent fashion. The protective effect of AF against QT prolongation induced torsades de pointe and transient post-cardioversion QT prolongation may result in dofetilide under-dosing during initiation. Thus, the optimal timing of cardioversion for AF patients undergoing dofetilide initiation to optimize discharge dose remains unknown as does the longitudinal stability of QT . The purpose of this study was to evaluate the impact of baseline rhythm on dofetilide dosing during initiation and assess the longitudinal stability of QT (Bazzett, Fridericia, Framingham, and Hodges) over time.

METHODS

Medical records of patients who underwent preplanned dofetilide loading at a tertiary care center between January 2016 and 2019 were reviewed.

RESULTS

A total of 198 patients (66 ± 10 years, 32% female, CHADS -Vasc 3 [2-4]) presented for dofetilide loading in either AF (59%) or sinus rhythm (SR) (41%). Neither presenting rhythm, nor spontaneous conversion to SR impacted discharge dose. The cumulative dofetilide dose before cardioversion moderately correlated (r = .36; p = .0001) with discharge dose. Postcardioversion QT prolongation (p < .0001) prompted discharge dose reduction (890 ± 224 mcg vs. 552 ± 199 mcg; p < .0001) in 30% patients. QT in SR prolonged significantly during loading (p < .0001). All patients displayed QT reduction (p < .0001) from discharge to short-term (46 [34-65] days) that continued at long-term (360 [296-414] days) follow-ups. The extent of QT reduction over time moderately correlated with discharge QT (r = .54-0.65; p < .0001).

CONCLUSION

Dofetilide initiation before cardioversion is equivalent to initiation during SR. Significant QT reduction proportional to discharge QT is seen over time in all dofetilide-treated patients. QT returns to preloading baseline during follow-up in patients initiated in SR.