DETERMINING THE ECG CUT-OFF POINT IN SYSTEMIC LUPUS ERYTHEMATOSUS PATIENTS UNDERGOING HYDROXYCHLOROQUINE THERAPY
Authors: Carmen Lasa et al.
Hydroxychloroquine (HCQ) is a widely used drug in SLE with arrhythmic events in the short-term and dose-dependent cardiomyopathy in the medium to long-term.
This observational study assessed ECG abnormalities (atrioventricular block, bundle branch block or QT interval prolongation) in 105 consecutive SLE patients who had an electrocardiogram at baseline and at least one ECG at follow-up. The mean daily dose of HCQ was 256 mg per day. The ROC curve showed the highest efficacy cut-off point after a cumulative HCQ:dose of 4097g (Sensitivity 15%; Specificity 100%) and the optimal cut-off of 901g (Sensitivity 85%; Specificity 52.9%). This cut-off point was reached with a mean HCQ treatment in our sample of 9.7 years. High grade atrio-ventricular block was found in 5 patients. In all of them the cHCQ dose was over 901g.
This study suggests that an ECG should routinely be performed after about 10 years of usual HCQ dosing (200 mg/d) to detect dose-dependent medium-to long-term HCQ cardiotoxicity with reasonable sensitivity, but short term arrhythmic HCQ effects (QT-interval prolongation) may need earlier detection.