Frequency of, and Prognostic Factors for, Residual Thrombosis and Complete Veno-Occlusion Following Anticoagulation for Provoked Venous Thromboembolism (VTE) in Patients <21 years: Findings from the Kids-DOTT Multinational Trial

BACKGROUND: Prognostic factors for residual thrombosis (RT) and complete veno-occlusion (CVO) after 6 weeks of anticoagulation in pediatric acute VTE remain unknown. OBJECTIVES: This study assessed the frequency and predictors of RT and CVO through a prespecified secondary analysis of the Kids-DOTT randomized clinical trial. METHODS: Per trial protocol, RT and CVO were radiologically assessed 6 weeks after acute VTE diagnosis. Univariate logistic regression analyses were performed for both outcomes, and variables with a P value of .05 were included in a multivariable models, where a P value of <.05 denoted statistical significance. RESULTS: Among 532 enrolled patients, 28.8% demonstrated RT and 12.6% CVO after 6 weeks of treatment. Age and gender distributions did not differ significantly by RT and CVO status. In multivariable analysis, cerebral venous sinus location of VTE (odds ratio [OR], 2.52; 95% CI, 1.22-5.21; P = .01) and comorbid infection (OR, 1.61; 95% CI, 1.00-2.58; P = .049) were independently associated with RT. Internal jugular vein (OR, 3.97; 95% CI, 1.26-12.48; P = .02) and lower extremity VTE (OR, 2.28; 95% CI, 1.01-5.15; P = .046) were independently associated with CVO. CONCLUSION: Approximately 29% of young patients developed RT, and 13% CVO, after 6 weeks of anticoagulation. VTE location and comorbid infection were identified as predictors for RT and CVO. These findings highlight the need for further studies on long-term outcomes of RT and CVO, particularly their impact on postthrombotic syndrome development and quality-of-life measures in pediatric VTE.