An Observational Study to Learn More About How Safe Rivaroxaban is And How Well it Works in Children With Congenital Heart Disease Who Had a Heart Surgery Called the Fontan Procedure

This is an observational study in which the data from children with congenital heart disease will be collected and studied. These children will include those who are prescribed rivaroxaban by their doctors after a heart surgery called the Fontan procedure. Congenital heart disease (CHD) is a heart problem that some children are born with. It sometimes requires a surgery called the Fontan procedure to improve the blood flow in the body. The Fontan procedure can increase the risk of the formation of blood clots in the blood vessels (called thrombosis), which might lead to death. The study drug, rivaroxaban, is an approved treatment for preventing the formation of blood clots. It is a type of anticoagulant that prevents the blood from clotting by blocking a protein responsible for it. Rivaroxaban can increase the risk of bleeding. A previous study suggested that the number of major bleeding episodes did not differ much while taking rivaroxaban compared to aspirin in children with CHD who had undergone the Fontan procedure. However, there is limited information available for Japanese patients. To better understand the safety and potential risks of this drug in children, more knowledge is needed about the use of rivaroxaban in the real world. The main purpose of this study is to learn more about the occurrence of major bleeding or non-major bleeding in children who were treated with rivaroxaban. Major bleeding is defined as a serious or life-threatening bleeding episode that can have an impact on a person's health and requires medical attention. Non-major bleeding is defined as a type of bleeding that may negatively impact a person's health if not treated. The data will be collected from December 2023 to June 2026. Researchers will observe each participant for up to 30 days after stopping the treatment or for a maximum of 2 years. In this study, only available data from regular health visits will be collected. No visits or tests are required as part of this study. Researchers will use the medical records or interview the children and/or their guardians during regular visits.