Genetics of cardiovascular development.

Structural malformations of the heart are the commonest abnormalities found at the time of birth and the incidence is higher in fetuses that are lost during the first trimester. Although the form of the heart has been studied for centuries, it is in the past decades that the genetic pathways that control heart development have been unraveled. Recently, the concept of the second heart field, a population of multipotent cardiac cells that augment the initial simple heart tube, has clarified the development of the heart. Understanding how the second heart field is used in morphogenesis and how genes interact in a subtle and more complex way is moving us closer to understanding how the normal heart forms and why abnormalities occur. In this chapter, we present a description of the morphological processes that create the formed postnatal human heart and emphasize key genetic pathways and genes that control these aspects. Where possible, these are also linked to the common patterns of human cardiac malformation. Undoubtedly, the details will refine or change with further research but emphasis has been placed on areas of greatest certainty and the presentation designed to promote a general understanding.