Enhanced Sensitivity to Drug-Induced QT Interval Lengthening in Patients With Heart Failure Due to Left Ventricular Systolic Dysfunction.

Patients with heart failure (HF) are at increased risk for drug-induced torsades de pointes (TdP) due to unknown mechanisms. Our objective was to determine if sensitivity to drug-induced QT interval lengthening is enhanced in patients with HF. In this multicenter, prospective study, 15 patients with atrial fibrillation or flutter requiring conversion to sinus rhythm were enrolled: 6 patients with New York Heart Association class II to III HF (mean ejection fraction [EF], 30% ± 9%), and 9 controls (mean EF, 53% ± 6%). Patients received ibutilide 1 mg intravenously. Blood samples and 12-lead electrocardiograms were obtained prior to and during 48 hours postinfusion. Serum ibutilide concentrations at 50% maximum effect on Fridericia-corrected QT (QTF) intervals (EC50) were determined, and areas under the effect (QTF interval vs time) curves (AUECs) were calculated. Ibutilide concentration–QTF relationships were best described by a sigmoidal Emax model with a hypothetical effect compartment. Median [interquartile range] AUEC from 0 to 4 hours was larger in the HF group than in controls (1.86 [1.86-1.93] vs 1.82 [1.81-1.84] s·h; P = .04). Median EC50 was lower in the HF group (0.48 [0.46-0.49] vs 1.85 [1.10-3.23] μg/L; P = .008). Sensitivity to drug-induced QT interval lengthening is enhanced in patients with systolic HF, which may contribute to the increased risk of drug-induced TdP. [ABSTRACT FROM PUBLISHER]