Dofetilide (Tikosyn) treatment for atrial arrhythmias requires initiation of the drug in the hospital, careful attention to multiple QTc intervals, and adherence to standard guidelines. Ventricular pacing, by widening the QRS interval, can prolong the QTc interval. As no data exists regarding monitoring of the QTc interval in patients with ventricular pacing, our objective was to assess the effect of ventricular pacing on QTc intervals in patients receiving dofetilide.
Over a two year period, 119 patients including 50 patients with implanted device (ID), [permanent pacemaker (PPM), ± internal cardioverter defibrillator (ICD)] and 69 patients without ID were admitted for initiation of dofetilide using institutional protocol. Baseline and serial QRS intervals and QTC intervals (with manual correction) were utilized to guide drug therapy. In patients with ID (PPM ± ICD), longer QTC intervals were accepted (in patients with PPM due to QRS widening; in the ICD group due to perceived safety) to achieve therapeutic drug effect.
Fifty patients with ID (mean age 71.7 yrs), 68% with a history of antiarrhythmic therapy (AAR), were compared to 69 patients without ID (mean age 61.7 yrs), 50% of whom also had history of AAR. Their ECG parameters are shown in Table 1. Within the group with ID, QRS (duration) and QTc intervals were significantly longer than in PPM category. In each group, 96% of the patients were discharged to home in sinus rhythm and 4% of the patients required dofetilide to be discontinued due to torsade de pointes. After mean follow-up of 65 ± 30 weeks in the ICD group, only one patient required discontinuation of dofetilide treatment due to torsade de pointes. None of the patients experienced a fatal outcome.
Ventricular pacing is associated with significant QRS widening and, therefore, prolongation of QTc interval.
Maximum limit of 500 msc. for QTc interval used for patients without ID may be safely extended by an additional 30 msc. in patients with ID and dofetilide therapy.
Pramod Deshmukh, None.