A. Top panels: Representative images of early mitotic luminal cardiomyocytes in E8.5 wild-type hearts co-stained for pHH3 (green), Pcnt (yellow), TnT (purple), and DAPI (blue). Lower panels: Superimposed axis of cell division (solid line) relative to the cardiac lumen (dashed line). B. Radial histogram depicting the orientation of cardiomyocyte divisions in early-stage mitotic cells from E8.5 wild-type hearts. C. Top panels: Representative images of luminal telophase cardiomyocytes in E8.5 wild-type hearts co-stained for survivin (green), TnT (red), and DAPI (blue). Lower panels: Superimposed axis of cell division (solid line) relative to the cardiac lumen (dashed line). D. Radial histogram depicting the orientation of cardiomyocyte divisions in late-stage mitotic cells from E8.5 wild-type hearts. Scale bars: 10µm.