The key findings of the present study are the following: (1) in patients with active severe COVID-19 and elevated IL-6 levels, regardless of acute myocardial injury/strain and concomitant QT-prolonging risk factors, QTc is significantly prolonged and rapidly normalized in correlation with IL-6 decrease; (2) direct administration of IL-6 in an in vivo guinea pig model acutely prolongs QTc duration; and (3) ventricular myocytes incubated in vitro with IL-6 show evident APD prolongation, along with significant inhibition in the IKr current (Figure 5). Here, IL6 is linked to COVID-19.