<Li> L--Limb defects </Li> <P> Ventricular septal defect (VSD), atrial septal defects, and tetralogy of Fallot are the most common congenital heart defects seen in the VACTERL association . Less common defects in the association are truncus arteriosus and transposition of the great arteries . </P> <P> The cause of congenital heart disease may be genetic, environmental, or a combination of both . </P> <P> Most of the known causes of congenital heart disease are sporadic genetic changes, either focal mutations or deletion or addition of segments of DNA . Large chromosomal abnormalities such as trisomies 21, 13, and 18 cause about 5--8% of cases of CHD, with trisomy 21 being the most common genetic cause . Small chromosomal abnormalities also frequently lead to congenital heart disease, and examples include microdeletion of the long arm of chromosome 22 (22q11, DiGeorge syndrome), the long arm of chromosome 1 (1q21), the short arm of chromosome 8 (8p23) and many other, less recurrent regions of the genome, as shown by high resolution genome - wide screening (Array comparative genomic hybridization). </P>

A congenital heart defect manifested by four key features all involving the heart is known as