Inclusion criteria:  Minor patient (<18 years old) Cardiac surgery act under cardiopulmonary bypass for correction of congenital heart disease Platelet transfusion for any reason  Cardiac surgery performed at Bordeaux or Strasbourg University Hospital over two periods:  Period A: January 01, 2016 - June 30, 2017 (before treatment) Period B: January 01, 2018 - June 30, 2019 (after treatment) Subject (and / or his parental authority) not having expressed, after information, his opposition to the reuse of his data for the purposes of this research  Exclusion criteria  Subject (and / or his parental authority) having expressed, after information, his opposition to the reuse of his data for the purposes of this research Presence or installation of transient circulatory assistance (outside of the CEC) or definitive Heart or cardiopulmonary transplantation