Hydroxychloroquine Inhibits Cardiac Conduction in Aged Patients with Nonmalaria Diseases

BACKGROUND: The COVID-19 pandemic has brought increased focus on hydroxychloroquine (HCQ), as doctors, the medical community, and policymakers around the world attempt to understand how the risks of HCQ weigh against unknown benefits. We aim to evaluate the effects of HCQ on cardiac conduction, thus contributing to the global understanding of implications of HCQ use. METHODS: We reviewed 717 cases of nonmalaria patients treated with HCQ (302) or without HCQ (415) in our hospital from 2008 to 2019, analyzed the cardiac conduction recorded by electrocardiogram (122 vs. 180) including heart rate (HR), PR, and corrected-QT (QTc) intervals, and explored the relationship of cardiac conduction with age, HCQ dosage, HCQ duration, sex, and primary diseases in HCQ users. RESULTS: The all-cause mortality is similar between HCQ and non-HCQ groups (4.0 vs. 4.3%, p = 0.85). Patients aged 45 years or older, not younger ones, have lower HR (80.1 ± 1.7 vs. 85.7 ± 1.8 bpm, p = 0.03) but longer PR (163 ± 3.4 vs. 146.6 ± 4.2 ms, p = 0.003) and QTc (417.8 ± 3.8 vs. 407.7 ± 2.7 ms, p = 0.03) in HCQ than those in non-HCQ. The age in the HCQ group is positively correlated with PR (R = 0.31, p < 0.01) and QTc (R = 0.34, p < 0.01) but not HR. HR, PR, and QTc are not related to HCQ dosage (0.1–0.6 g/day), HCQ duration (0.2–126 months), sex, primary diseases, and repeated exams. CONCLUSION: Age is the most important risk factor of HCQ on cardiac conduction in nonmalaria patients. Electrocardiogram monitoring is suggested in aged patients due to the effects of HCQ on HR, PR, and QTc.