• According to Clark (2002) classification, there are six causative mechanisms (1) ectomesenchymal tissue migration abnormalities (causing conotruncal malformations and aortic arch anomalies); (2) intracardiac blood flow defects (causing septal defects and left or right heart obstructive malformations); (3) cell death abnormalities (causing septal defects and valve abnormalities); (4) extra cellular matrix abnormalities (causing atrioventricular canal defects); (5) abnormal targeted growth (causing partial or total anomalous pulmonary venous return and cor triatriatum) and (6) abnormal situs and looping (causing left–right positioning problems)• According to clinical presentation congenital heart disease is often divided into two types: cyanotic (blue discoloration caused by a relative lack of oxygen) and non-cyanotic.• The heart is the first organ to form during embryogenesis and its circulatory function is critical early on for viability of the embryo. The development of the integrated cardiovascular tissue is the result of multiple tissue and cell to cell interactions involving temporal and spatial events under genetic control. some of the genes involved in normal cardiogenesis include transcription factors (e.g., NKX2.5, GATA6, GATA4, HAND1, HAND2, and NFATC)• Transcription factors are proteins that contain DNA binding domains and serve a fundamental regulatory role by controlling gene expression. Signaling molecules are proteins that allow cells to respond to their environment and are thereby involved in regulation of many important biological functions.