Who was in the study?

From 2017 to 2021, 192 participants ages 28 days to 17 years with congenital or acquired heart disease who needed to take medication to prevent blood clots were enrolled and randomized.

What happened during the study?

Participation lasted for up to 14 months, or until anticoagulation was no longer needed.  The study consisted of:

1. Screening: physical examination, including heart rate, blood pressure, body temperature, height and weight, and blood draw for laboratory tests. Children 5 years and older had a bone density scan.
2. Randomization: Children were randomly assigned to receive either apixaban (by mouth or feeding tube) or to receive one of the blood thinners commonly used to treat this condition: either VKA or LMWH. Older participants were also be asked to answer survey questions about quality of life. A blood sample was requested.
3. Treatment: Participants took the study medication for 12 months, or until they no longer need a blood thinner. Return visits to the study center occurred at 2 weeks, 3 months, 6 months, 12 months and 14 months after beginning treatment. Visits included a physical examination, blood draw for laboratory tests, and questions about side effects, adverse events, and blood clots or bleeding. Some visits also included a bone density scan and quality of life questionnaires. The study center also called to check up on the child after 8 months and 10 months of treatment.

What were the results of the study?

One apixaban participant (0.8%) and 3 with other standard treatments (4.8%) had major or clinically relevant nonmajor bleeding (% difference -4.0 [95% CI: -12.8 to 0.8]). Apixaban incidence rate for all bleeding events was nearly twice the rate of other treatments (100.0 vs 58.2 per 100 person-years), driven by 12 participants with ≥4 minor bleeding events. No thromboembolic events or deaths occurred in either group. Apixaban pediatric PK steady-state exposures were consistent with adult levels.

In this pediatric multinational, randomized trial, bleeding and thromboembolism were infrequent. These results support the use of apixaban as an alternative for thromboprophylaxis in pediatric heart disease.