Another observation in COVID-19 patients admitted to ICU showed that QTc intervals increased in 93% of patients receiving HCQ with or without azithromycin, prolonged QTc was observed in 36% of patients after a duration of the treatment for 2 to 5 days, and 6 of 18 (33%) patients treated with HCQ and azithromycin and 1 of 22 (5%) of those treated with HCQ alone developed an increase in QTc of 500 ms or greater [69].