TMEM43 and arrhythmogenic right ventricular cardiomyopathy: Here, using induced‐pluripotent‐stem‐cell‐derived cardiomyocytes (iPSC‐CMs) and knock‐in mice as models, it is demonstrated that a novel TMEM43 mutation (TMEM43‐P386S) causes Ca2+ dysregulation that leads to arrhythmic phenotypes in ARVC, which can be prevented by flecainide.