Combination of four heart defects: ventricular septal defect (VSD), right ventricular outflow tract obstruction (pulmonary stenosis), right ventricular hypertrophy, and overriding aorta (aorta positioned above the VSD) (see Looking at tetralogy of Fallot)

Occurs equally in males and females and accounts for about 10% of all congenital heart diseases

Blood shunts from right to left through the VSD, which permits unoxygenated blood to mix with oxygenated blood, resulting in cyanosis.

VSD may (at times) coexist with other congenital heart defects, such as patent ductus arteriosus or atrial septal defect.