Cardiomyocyte maturation and cell cycle activity. A: terminal differentiation, as measured by binucleation, was not different between the right carotid artery-jugular vein (AV) and the sham group. B: left ventricular (LV) cell cycle activity, required for proliferation and binucleation, was 60% lower in AV fetuses. RV, right ventricle. Values are means ± SE. *P < 0.02 between groups.