The Mustard procedure was developed in 1963 by Dr. William Mustard at the Hospital for Sick Children in Toronto, Ontario, Canada. Dr. Mustard, with support from the Heart and Stroke Foundation of Canada, developed an alternative and simplified technique to the Senning procedure which was used to correct a congenital heart defect that produced “blue babies”. The technique was adopted by other surgeons and became the standard operation for d-TGA.