Time-course of the electrophysiological maturation and integration of transplanted cardiomyocytes

► Fetal cardiomyocytes coupled to host cells mature after transplantation. ► The pace of maturation correlates with the quality of electrical integration. ► Well-coupled transplanted cells have adult-like action potentials after 12 days. ► Electrical integration improves between days 6 and 12 after transplantation. ► Conduction decelerations and blocks still occur after 12 days.