Hydroxychloroquine and Cardiotoxicity.

Hydroxychloroquine (HCQ) has been used for rheumatological diseases such as systemic lupus erythematous and rheumatoid arthritis and demonstrated to improve clinical symptoms and reduce long-term sequelae. The drug is metabolized in the liver, is primarily excreted through the kidney, and works by modulating major histocompatibility complex (MHC) and various cytokines, suppressing the immune system in the process. Prolonged administration and high dosages of HCQ have been associate with cardiotoxic effects such as bradycardia, tachycardia, QT prolongation, atrioventricular block, and cardiomyopathy. Common cardiac biopsy findings of HCQ-induced toxicity are enlarged and vacuolated cells on light microscopy along with the presence of myelinoid and curvilinear bodies on transmission electron microscopy. HCQ cardiotoxicity is not very well recognized, and there are no current guidelines for routine cardiac function monitoring from either rheumatology or cardiology societies.