KCNH2 and Familial short QT syndrome: 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.