QT Interval Prolongation in Patients Treated for COVID-19

Background: Many of the drugs commonly used for the treatment of COVID-19 cause QT interval prolongation and increase the risk of life-threatening cardiac arrhythmias. It has been shown that maintaining serum potassium and magnesium levels above 4 and 3 mg/dL, respectively, would prevent the QTc prolongation. Objective: To determine if keeping only the serum magnesium level above 3 mg/dL could be considered an effective measure to prevent QTc prolongation in patients with COVID-19 receiving these drugs. Methods: In a retrograde observational study, QTc interval was measured in 14 patients diagnosed with COVID-19 before and 3 days after initiation of treatment with either hydroxychloroquine or lopinavir-ritonavir, while their serum magnesium levels were kept ≥3 mg/dL. Results: The baseline QTc interval of 412 (SD 36) ms significantly increased by an average of 34 (95% CI 13 to 55) ms after 3 days of treatment. 5 patients, mostly those with lower serum potassium levels, had QTc prolongation ≥60 ms. Conclusion: Although it seems that the risk of fatal cardiac arrhythmias in this setting is not high, it is prudent to monitor the serum electrolytes, particularly potassium, in patients with COVID-19 who are treated with either hydroxychloroquine or lopinavir-ritonavir.