Objective: To determine whether hydroxychloroquine (HCQ) dose is associated with adverse cardiac outcomes in patients with systemic lupus erythematosus (SLE). Methods: Patients with SLE taking HCQ and with ≥1 echocardiogram followed at a tertiary care center in the Bronx, New York between 2005 and 2021 were included. The HCQ weight-based dose at the HCQ start date was the main exposure of interest. The outcome was incident all-cause heart failure with reduced ejection fraction (HFrEF), life-threatening arrhythmia, or cardiac death. We used Fine-Gray regression models with death as a competing event to study the association of HCQ dose with the outcome. Due to a significant interaction between smoking and HCQ exposure, models were stratified by smoking status. Propensity score analysis was performed as a secondary analysis. Results: Of 294 patients, 37 (13%) developed the outcome over a median follow-up time of 7.9 years (interquartile range [IQR] 4.2–12.3 years). In nonsmokers (n = 226), multivariable analysis adjusted for age, body mass index, hypertension, chronic kidney disease, diabetes mellitus, and thromboembolism showed that higher HCQ weight-based doses were not associated with an increased risk of the outcome (subdistribution hazard ratio [HR] 0.62 [IQR 0.41–0.92], P = 0.02). Similarly, higher baseline HCQ doses were not associated with a higher risk of the outcome among smokers (n = 68) (subdistribution HR 0.85 [IQR 0.53–1.34] per mg/kg, P = 0.48). Propensity score analysis showed comparable results. Conclusion: Higher HCQ doses were not associated with an increased risk of HFrEF, life-threatening arrhythmia, or cardiac death among patients with SLE and may decrease the risk among nonsmokers.
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