Fetal Cardiac Physiology and Fetal Cardiac Intervention

Three shunts that are critical to carrying out streaming of blood in the fetal circulatory system are the ductus venosus, the foramen ovale (FO), and the patent arterial duct. At birth, the pattern of circulation changes from the fetal “parallel” type to the adult “series” type, leading to more efficient oxygen uptake and delivery. This happens with rapid establishment of pulmonary circulation, loss of placental circulation, and the closure of the ductus vein, the FO, and eventually the arterial duct. The utility of fetal cardiac intervention is based on the fundamental principle that congenital heart disease evolves in utero, and that intervention in the fetus may beneficially alter the natural progression of the disease. Fetal aortic valvuloplasty is the most commonly performed fetal cardiac intervention, and is primarily indicated for critical valvar aortic stenosis with evolving hypoplastic left heart syndrome.