An 84-year-old woman with hypertension, Alzheimer's disease, and chronic kidney disease presented with fever and was diagnosed with corona virus disease 2019 (COVID-19). During the hospitalization, she experienced unexpected sinus bradycardia with prolonged QTc, which was thought to be closely related to the short-term use of hydroxychloroquine (HCQ), an old drug used to treat malaria and autoimmune diseases, but now used against COVID-19. The cardiac side effects of HCQ were rare, seen with short-term and low-dose use. With the COVID-19 pandemic, this case alerts clinicians to be aware of the arrhythmogenic effects of HCQ when it is used as an antiviral drug, especially in patients with preexisting cardiovascular diseases.
