Incidence and risk factors for postthrombotic syndrome in neonates and children in a single-center cohort study

Background: Postthrombotic syndrome (PTS) is a chronic condition following deep vein thrombosis (DVT) and is associated with pain, swelling, and restricted use of the affected limb. In pediatric age groups, its incidence and risk factors are not well-known. Methods: This observational cohort study of all consecutive children (<= 18 years) with DVT treated at the Emma Children's Hospital Amsterdam between January 2001 and January 2021 was conducted to identify incidence and risk factors for PTS in neonates aged <= 2 months and children aged >2 months. PTS was diagnosed using the modified Villalta scale. Results: In total, 315 patients were included. The 20-year incidence of PTS was 20.0% in neonates and 40.0% in children. In neonates, involvement of >= 3 vessels (odds ratio [OR], 6.6; 95% CI, 1.6-26.4) and incomplete thrombus resolution (OR, 3.0; 95% CI, 1.18.0) were risk factors for PTS. In children, involvement of >= 3 vessels (OR, 6.2; 95% CI, 2.2-17.8), recurrent DVT (OR, 3.7; 95% CI, 1.3-10.3), and incomplete thrombus resolution (OR, 5.2; 95% CI, 1.6-17.0) were associated with PTS. Exercise >= 3 times/wk (OR, 0.4; 95% CI, 0.2-0.9), central venous catheter-related DVT (OR, 0.2; 95% CI, 0.1-0.5), and provoked DVT (OR, 0.4; 95% CI, 0.1-0.97) were protective factors for PTS. Conclusion: This study demonstrated a high incidence of pediatric PTS. Additionally, risk factors for PTS differed between neonates and children. These findings provide a basis for better prevention and management of PTS that may differ between neonates and children.