Reduction over time of QTc prolongation in patients with sotalol after cardioversion of atrial fibrillation

Longitudinal QTc Stability and Impact of Baseline Cardiac Rhythm on Discharge Dose in Dofetilide-treated Patients

BACKGROUND

Dofetilide suppresses AF in a dose-dependent fashion. The protective effect of AF against QT_c prolongation induced torsades de pointe and transient post-cardioversion QT_c 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_c .

OBJECTIVE

To evaluate the impact of baseline rhythm on dofetilide dosing during initiation and assess the longitudinal stability of QT_c-all (Bazzett, Fridericia, Framingham, and Hodges) over time.

METHODS

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

RESULTS

A total of 198 patients (66±10 years, 32% female, CHADS₂ -Vasc 3 [2-4]) presented for dofetilide loading in either AF (59%) or SR (41%). Neither presenting rhythm, nor spontaneous conversion to SR impacted discharge dose. The cumulative dofetilide dose prior to cardioversion moderately correlated (r=0.36; p=0.0001) with discharge dose. Post-cardioversion QT_c-all prolongation (p<0.0001) prompted discharge dose reduction (890±224mcg vs 552±199mcg; p<0.0001) in 30% patients. QT_c-all in SR prolonged significantly during loading (p<0.0001). All patients displayed QT_c-all reduction (p<0.0001) from discharge to short-term (46 [34-65] days) that continued at long-term (360 [296-414] days) follow-ups. The extent of QT_c-all reduction over time moderately correlated with discharge QT_c-all (r=0.54-0.65; p<0.0001).

CONCLUSION

Dofetilide initiation prior to cardioversion is equivalent to initiation during SR. Significant QT_c reduction proportional to discharge QT_c is seen over time in all dofetilide-treated patients. QT_c returns to pre-loading baseline during follow-up in patients initiated in SR. This article is protected by copyright. All rights reserved.

Antiarrhythmic Drugs for Atrial Fibrillation: Selected Features of Ventricular Repolarization That Facilitate Proarrhythmic Torsades de Pointes and Favor Inpatient Initiation

The management approaches to patients with atrial fibrillation (AF) include rhythm-control strategies for those patients who are symptomatic despite rate control and for selected others in whom sinus rhythm is necessary for reasons beyond current symptoms (including commercial pilots, those who are felt likely to develop symptoms as comorbidities progress, and more). First-line therapies among the rhythm-control options are antiarrhythmic drugs (AADs). For many AADs, their initiation in-hospital is either a requirement or strongly advised- especially when the patient is in AF. This article explores some of the rationale behind this requirement to give clinicians a better understanding of the reasons for this undesired inconvenience.

Diurnal QT analysis in patients with sotalol after cardioversion of atrial fibrillation

Background

The risk of ventricular arrhythmias in patients on QT prolonging drugs is indicated to be increased early after cardioversion (CV) of atrial fibrillation (AF) to sinus rhythm (SR). Sotalol, used to prevent AF relapse, prolongs cardiac repolarization and corrected QT interval (QTc). A pronounced QTc prolongation is an established marker of pro‐arrhythmias. Our objective was to use novel technique to quantify and evaluate the diurnal variation of the QTc interval after elective CV to SR in patients on sotalol or metoprolol.

Methods

Fifty patients underwent twelve‐lead Holter recording for 24 hr after elective CV for persistent AF. All patients had the highest tolerable stable dose of sotalol (n = 27) or metoprolol (n = 23). Measurements of QT and RR intervals were performed on all valid beats.

Results

A clear diurnal variation of both HR and QTc was seen in both groups, more pronounced in patients on sotalol, where a high percentage of heartbeats with QTc >500 ms was observed, especially at night. Six patients (22%) on sotalol but none on metoprolol had >20% of all heart beats within the 24‐hour recording with QTc >500 ms.

Conclusion

Twenty‐four‐hour Holter recordings with QT‐measurement immediately after CV demonstrated that one in five patients on sotalol had >20% of all heart beats with prolonged QTc >500 ms, especially during night‐time. The QTc diurnal variation was retained in patients on β‐blockade or a potent class III anti‐arrhythmic drug with β‐blocking properties.