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Objective

To assess the association between hydroxychloroquine (HCQ) initiation and risk of incident arrhythmia among incident rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) patients.

Methods

All patients with incident RA or SLE and no arrhythmic events, anti-arrhythmic medications and no HCQ use prior to disease index date in British Columbia, Canada, between January 1996 and December 2014 were identified using administrative databases. HCQ initiator and HCQ non-initiator groups were identified and matched 1:1 by propensity scores using baseline confounders on demographics, comorbidities, medications, and healthcare utilization. Outcomes were any new arrhythmias, atrial fibrillation, abnormal electrocardiogram including prolonged QT syndrome and conduction disorder, and other unspecified arrhythmias during follow-up. We used cause-specific Cox proportional hazard 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 RA and SLE individuals in each group. Over the mean follow-up of eight years, there were 1,610 and 1,646 incident arrhythmias in the HCQ initiator and non-initiator groups, respectively. The crude incidence rates of arrhythmia were 17.5, and 18.1 per 1,000 person-years, respectively. Adjusted cause-specific hazard ratio (cHR) for HCQ initiators was 0.96 (95% CI: 0.89-1.03) compared to non-initiators. The corresponding adjusted cHRs for HCQ initiators in subtypes of arrhythmia – atrial fibrillation, abnormal electrocardiogram, 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

There is no increased risk of any type of arrhythmia among new users of HCQ.

Read a Q&A with a study coauthor here and expert commentary on the clinical implications here.