Cardiac hypertrophy in chronically anemic fetal sheep: increased vascularization is associated with increased myocardial expression of vascular endothelial growth factor and hypoxia-inducible factor 1

Chronically inadequate oxygenation of the fetal heart appears to induce ventricular enlargement and increased blood vessel development. Researchers deprived fetal sheep of oxygen by diluting their blood. Oxygen-deprived, or hypoxic, hearts were bigger, had larger capillaries, and denser capillary networks than the hearts of fetuses normally oxygenated. Vascular endothelial growth factor and hypoxia-inducible factor 1 alpha protein levels were higher in the ventricles of hearts deprived of oxygen. Oxygen deprivation may cause compensatory changes in the fetal heart.