Prospective Randomized Open Label Multi-center Study of the Safety and Pharmacokinetics of Apixaban versus Vitamin K Antagonist or Low Molecular Weight Heparin in Pediatric Subjects with Congenital or Acquired Heart Disease Requiring Chronic Anticoagulation for Thromboembolism Prevention

Inclusion Criteria
Congenital or acquired heart diseases requiring chronic anticoagulation for thromboprophylaxis (eg, single ventricle physiology including all 3 stages of palliation, dilated cardiomyopathy, Kawasaki disease with coronary aneurysms, and pulmonary hypertension).
Eligible subjects include those who newly start anticoagulants and those who are currently on VKA or LMWH or other anticoagulants for thromboprophylaxis.
Able to tolerate enteral medication [eg, by mouth, Nasogastric (NG) tube, or Gastric-(G) tube].
Exclusion Criteria
Recent thromboembolic events less than 6 months prior to enrollment
Use of aggressive life-saving therapies such as ventricular assist devices (VAD) or extracorporeal membrane oxygenation (ECMO) at the time of enrollment
Prosthetic heart valves, and mechanical heart valves
Active bleeding at the time of enrollment
Known inherited bleeding disorder or coagulopathy (eg, hemophilia, von Willebrand disease, etc)
Known intracranial congenital vascular malformation or tumor
Any major bleeding other than perioperative in the preceding 3 months
Uncontrolled severe hypertension
Liver dysfunction
Renal dysfunction
In the opinion of the Investigator, it is not possible for the subject to be compliant with the protocol and study procedures
Pregnancy during the study period
Concurrent use of or participation in another experimental drug/device trial