TBX20 and Tetralogy of Fallot: Studies have reported mutations in the TBX1 gene in families with a history of CHD, and some mutations have been related to isolated abnormalities such as tetralogy of Fallot, interrupted aortic arch, double ventricular right ventricle, pulmonary atresia, and ventricular septal defects (VSD) [7], while the TBX20 gene performs critical activities in the development of the heart and adult cardiac function [12].