Although the α-myosin heavy chain, encoded by MYH6, is predominantly expressed during fetal development and becomes less prominent postnatally, mutations in MYH6 have been strongly implicated in a range of cardiac diseases, including hypertrophic cardiomyopathy, dilated cardiomyopathy, and congenital heart defects such as atrial septal defects. This evidence concerns the gene MYH6 and atrial septal defect.