Congenital heart diseases (CHD) result from abnormal development of the cardiovascular system and usually involve defects in specific steps or structural components of the developing heart and vessels. The determination of left-right patterning of our body proceeds by the steps involving the leftward “nodal flow” by motile cilia in the node and molecules that are expressed only on the left side of the embryo, eventually activating the molecular pathway for the left-side specific morphogenesis. Disruption of any of these steps may result in left-right patterning defects or heterotaxy syndrome. As for the outflow tract development, neural crest cells migrate into the cardiac outflow tract and contribute to form the septum of the outflow tract that divides the embryonic single truncus arteriosus into the aortic and the pulmonary trunk. Reciprocal signaling between neural crest cells and another population of myocardial precursor cells originated from the second heart field are essential for the steps of outflow tract development. To better understand the etiology of CHD, it is important to consider what kind of CHD is caused by abnormalities in each step during the complex development of the cardiovascular system.
Fontan; heterotaxy; left–right axis; neural crest; outflow tract; second heart field.