Rivaroxaban in Paediatric Venous Malformations: Preliminary Data from a Retrospective Single-Center Study

Background and Aims: Venous malformations (VMs) are the most frequent type among congenital vascular malformations, with an incidence between 0.8-1%. VMs can be cutaneous and extracutaneous, single or multiple; typically, VMs appear from birth, show progressive growth and persist throughout life. They require a multidisciplinary approach to ensure early diagnosis and prevent or treat any complications. We report preliminary data from our center's experience with the use of rivaroxaban in pediatric venous malformations complicated by thrombosis.

Methods: We conducted a retrospective observational single-center study at Bambino Gesù Children's Hospital. Data were collected from patients < 18 years old with venous malformations complicated by thrombosis treated with rivaroxaban, during the period from September 2022 to February 2024. Primary outcome was to evaluate improvement, resolution or progression of venous thrombosis, in patients treated with rivaroxaban. Secondary outcome was to evaluate symptomatic recurrences in patients undergoing secondary prophylaxis.

Results: Rivaroxaban was used for the treatment of acute venous thrombosis in 30 patients, after at least 5 days of parenteral anticoagulant therapy, and for secondary prophylaxis in 5 patients. Thrombophilia was found in 23 (66%) patients by hemocoagulative screening. The safety and efficacy of rivaroxaban were evaluated in all 35 enrolled patients; no patient was lost to follow-up. Clinical follow-up was performed at 3, 6, 12 months. Twenty-seven (90%) patients treated with rivaroxaban, reassessed at 3 to 6 months, reported complete regression of pain due to thrombosis. Among them, 71% had been previously treated with acetylsalicylic acid, with no improvement in pain symptoms and subsequent development of thrombosis. Two patients reported occasional pain and one persistence of pain symptoms after 3 months. Among the five patients on secondary prophylaxis, one had symptomatic recurrence 12 months after starting rivaroxaban, with recent onset of thrombosis detected on ultrasound. Follow-up imaging was performed at 6 and 12 months. Sixteen (46%) patients showed complete resolution of thrombosis at the end of treatment period; imaging improvement with almost complete recanalisation was observed in 11 (31%) patients. Two (5.7%) patients showed unchanged imaging with persistence of thrombosis at 6 months, while one patient developed thrombosis after 12 months of secondary prophylaxis. Five patients have not yet had ultrasound re-evaluation. Thirty-one (89%) patients experienced no side effects. Three patients reported nausea and diarrhea a few days after starting treatment, which resolved by halving the dose for 2 weeks; no further gastrointestinal symptoms after resuming the initial dose. One girl complained of menorrhagia in the first 3 menstrual cycles after starting rivaroxaban.

Conclusions: Preliminary data of our study showed that rivaroxaban was safe and effective in paediatric patients with complicated venous malformations or at risk of thrombotic recurrence. To date, bodyweight-adjusted rivaroxaban regimens are a viable alternative to standard anticoagulation, especially in patients requiring prolonged treatment, because they are available in oral formulations, oral suspension granules and tablets, and do not require laboratory monitoring.