The present European database study was designed to evaluate the risk of recurrent venous thrombosis (rVT) in 407 consecutively recruited CVT children from the Israel, United Kingdom, and Germany. Children were recruited between January 1996 and January 2003. 330 of them were prospectively followed at least 12 months. Median(range) age at first thrombosis onset was 5.3 years (newborn to < 18; male: 55%). The median(range) follow-up time was 33months (12–216).

Acute antithrombotic treatment (AT) with UFH or LMWH was applied in 252 of 330 patients (76.4%), followed by secondary AT in 212 subjects (64%). The latter was carried out in the majority of cases with LMWH (77.8%: enoxaparin or dalteparin: 2–4 hours anti-Xa activity 0.3–0.5 U/ml; duration: 6 months [3–12]), vitamin K-antagonists (17.5%; duration: 12 months [(4-lifelong]), or aspirin (1.5%).

18 of 330 surviving children (5.5%) suffered a second venous thrombosis 6 months (0.5–114) after first CVT. The rate of recurrences was no different in the three European countries (p=0.94). A significant positive correlation between higher age at first CVT and rVT was calculated (r=0.34; p=0.0002), and recurrence was significantly associated with the duration or secondary AT (p=0.0025). In contrast, no significant associations between rVT and mode of treatment (p=54), 3–6 months patency rates (p=0.08), basic diseases (p=0.2), or the presence of prothrombotic risk factors (p=0.8) were found. At the time of recurrence six of 18 patients were on AT, whereas in the remaining 12 patients rVT occurred 8 to 114 months after first thrombosis and after withdrawal of AT. In 87.5% of cases rVTs were associated with HIT, infections diseases, malignancies, diabetes type I, nephrotic syndrome, trauma, and the use of oral contraception. Spontaneous rVT occurred in two further children. Prothrombotic risk factors were found in 7 of 15 patients (46.6%) tested. In conclusion, in this European database study the rate of rVT in children with CVT is 5.5%. Since rVT was associated with age, AT therapy and co-morbid risk factors, the need for appropriate guidelines for prophylactic administration of AT in risk situations in children suffering a first CVT deserves consideration.

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