To investigate the pharmacological mechanisms of quinidine (i.e., a common antiarrhythmic drug for treating SQTS) on the KCNH2 T618I-associated short QT syndrome, we modeled the drug actions by adding two additional states to the Markov chain states (Fig. 7B) as in Whittaker et al.’s study13. Here, KCNH2 is linked to short QT syndrome.