Risk of Arrhythmia Among New Users of Hydroxychloroquine in Rheumatoid Arthritis and Systemic Lupus Erythematosus: A Population‐Based Study.

Objectives: We assessed the association between hydroxychloroquine (HCQ) initiation and risk of arrhythmia among patients with incident rheumatoid arthritis (RA) or with incident systemic lupus erythematosus (SLE). Methods: All patients with incident RA or SLE and no arrhythmic events, not receiving antiarrhythmic medications, and not receiving HCQ prior to the index date of disease in British Columbia, Canada, between January 1996 and December 2014 were identified from administrative databases. We identified patients who were dispensed HCQ prescriptions (HCQ initiators) or were not dispensed HCQ prescriptions (HCQ noninitiators) during each study year; groups were matched 1:1 by propensity scores using baseline confounders on demographics, comorbidities, medications, and health care utilization. Outcomes were any new arrhythmias, atrial fibrillation, abnormal electrocardiograms, including long QT syndrome and conduction disorder, and other unspecified arrhythmias during follow‐up. We used cause‐specific Cox proportional hazards models with death as a competing event to assess the association between HCQ initiation and the outcomes. Results: We identified 11,518 propensity score–matched patients with RA or SLE in each group. Over the mean follow‐up of 8 years, there were 1,610 and 1,646 incident arrhythmias in the HCQ initiator group and the noninitiator group, respectively, with crude incidence rates of arrhythmia of 17.5 and 18.1 in 1,000 persons per year, respectively. The adjusted cause‐specific hazard ratio (cHR) for patients who received HCQ was 0.96 (95% confidence interval [95% CI] 0.89–1.03) compared with HCQ noninitiators, and the cHRs for patients who took HCQ and had arrhythmia subtypes of atrial fibrillation, abnormal electrocardiograms, and other unspecified arrhythmias were 0.93 (95% CI 0.83–1.04), 0.98 (95% CI 0.87–1.11), and 0.95 (95% CI 0.84–1.07), respectively. Conclusion: Risk of any type of arrhythmia was not increased among new users of HCQ. [ABSTRACT FROM AUTHOR]