Molecular Basis of Cardiac Development

The heart begins simply as a bilateral field within the lateral plate mesoderm (Figure 1.1, Table 1.1). As the early embryo undergoes formation of the gut-tube, these bilateral fields migrate toward the midline, where the cranial-most aspect of the fields will fuse ventrally to form the outer curvature of the heart tube.1 These fields will continue to migrate together, with more of the heart fields contributing to the forming tube, until the dorsal aspect of the heart fields fuse to form a closed tube.1 The initial contributors to the heart tube are known as the first heart field.2 The first heart field gives rise to the left ventricle, with some contributions to the atria and the right ventricle.3 Additional heart field progenitors from the lateral plate mesoderm continue to add to the arterial and venous poles of the heart tube; these later-adding cells are known as the second heart field. The second heart field gives rise to most of the right ventricle and atria, the most distal myocardium that surrounds the aorta and pulmonary artery, and the most proximal smooth muscle that contributes to the tunica media of the great arteries.2