Congenital heart defects make up the largest category of malformations in Canadian children and are a significant cause of death in infants under one. However, improved detection, intervention, and care strategies are now allowing more individuals born with these defects to survive into adulthood and have children of their own. A better understanding of the genetic factors that predispose an individual to congenital heart disease is essential to not just treatment but also prevention. The database compiled in this study will continue to be augmented with information from more patients, but it has already shown that a particular type of heart defect, left ventricular outflow tract obstruction (LVOTO), is strongly linked to the inheritance of two or more genes.