DMD and Duchenne muscular dystrophy: A reduced peak INa, a characteristic feature of cardiomyocytes derived from dystrophin-deficient animal models for DMD (4, 5, 7–9), as well as cardiomyocytes derived from induced pluripotent stem cells of patients with DMD (2), slows the action potential upstroke velocity and cardiac conduction, thereby setting the stage for re-entrant arrhythmias and sudden cardiac death (1).