Early QTc Patterns During Antiarrhythmic Drug Loading as Predictors of Ventricular Arrhythmia and QT-prolongation

Abstract 2279847, presented at Western Atrial Fibrillation Symposium 2026

Atrial fibrillation (AF) is the most common arrhythmia worldwide, with a lifetime risk of 1 in 3. Antiarrhythmic drugs (AAD) require hospitalization for cardiac monitoring due to risks of ventricular arrhythmias (VA), like Torsades de Pointes (TdP). This study investigated the relationship between initial AAD response (ΔQTc) and adverse outcomes. Determine the significance of novel ECG biomarkers in predicting VA and long-QT in patients with AF.We conducted a retrospective analysis of patients admitted for sotalol and dofetilide loading (July 2022-April 2023) at an academic center. Patient demographics, AF history, AAD dosing, and ECG parameters were analyzed as predictors of adverse events.Among 110 patients (median age: 70 years; 69.1% male) undergoing dofetilide (n=101) and sotalol (n=9), baseline QTc was 442.6 ± 33.0 ms, with a ΔQTc of 22.7 ± 33.4 ms (5.36 ± 0.08% increase). Adverse events (AE) including VA and prolonged-QT occurred in 47 (42.7%) patients. Results from univariate, bivariate, and multivariate logistic regression are displayed in Table I. Importantly, a 10.5% change in QTc (post-dose 1) from baseline was a strongly significant independent indicator of AE risk (Model G, ACCc=136.87). In models fully adjusted for baseline QTc, CrCl, BMI, and contraindications, QTc Change >48 ms (OR 17.80, 95% CI 4.73-67.01) and %QTc Change >10.5% (OR 18.58, 95% CI 4.96-69.65) demonstrated the strongest associations with adverse events. However, Model Y predicted AE better than all others, emphasizing the significance and simplicity of ΔQTc>10.5% in predicting VA and prolonged QT.Initial QTc response (ΔQTc>10.5%) emerged as the strongest predictor of adverse outcomes, even when compared to current clinical indicators of VA/prolonged QT risk (e.g. contraindication). These findings offer a biomarker to potentially improve risk stratification for AF patients initiating AADs.