Prevalence of post-thrombotic syndrome following asymptomatic thrombosis in survivors of acute lymphoblastic leukemia

Validation of a predictive model for identifying an increased risk for thromboembolism in children with acute lymphoblastic leukemia: results of a multicenter cohort study

Among risk factors for developing thromboembolism (VTE) in children with acute lymphoblastic leukemia were Escherichia coli asparaginase, concomitant steroid use, presence of central venous lines, and thrombophilic abnormalities. Developing a predictive model for determining children at increased risk would be beneficial in targeting interventional studies to high-risk groups (HRGs). Predictive variables were incorporated into a risk assessment model, which was evaluated in 456 children and then validated in 339 patients. VTE risk by score was no greater than 2.5 for low-risk group (LRG) and greater than 2.5 for HRG. VTE rates at 3.5 months (validation cohorts) were 2.5% in LRG and 64.7% in HRG. In multivariate analysis adjusted for age, duration of asparaginase administration, enoxaparin prophylaxis, and T-immunophenotype, the HRG was significantly associated with VTE compared with the LRG (hazard/95% confidence interval [CI], 8.22/1.85-36.53). Model specificity was 96.2% and sensitivity was 63.2%. As secondary objective we investigated the use of enoxaparin for VTE prophylaxis in the HRG. HRG patients without enoxaparin prophylaxis showed a significantly reduced thrombosis-free survival compared with children on low-molecular-weight heparin (LMWH). On the basis of the high specificity, the model may identify children with leukemia at risk of VTE. LMWH may help prevent VTE in the HRG; this warrants assessment in larger cooperative clinical trials.

Low-dose systemic thrombolytic therapy for deep vein thrombosis in pediatric patients

Reduction of thrombus size and recanalization of vessels after deep vein thrombosis (DVT) are important goals to prevent recurrent thrombosis and development of postthrombotic syndrome. Thrombolysis is effective but concern for bleeding complications has limited its use in children. We retrospectively analyzed data for children with DVT treated with a low-dose systemic tissue plasminogen activator (tPA) regimen. Twenty-three pediatric patients (12 males and 11 females, median age 12 y) received low-dose systemic tPA, initiated at 0.03 to 0.06 mg/kg/h for a median of 24 hours (range 12 to 48 h). Of the 20 patients imaged within 24 hours of therapy, 6 (30%) showed partial to complete thrombus resolution. Eight patients subsequently received increased tPA at 0.12 mg/kg/h for an additional 24 hours (range 12 to 36 h). Six of these 8 (75%) patients responded to the increased dose. The overall response at the end of thrombolytic therapy was 59% (13/22). Two bleeding complications occurred without serious sequelae. Low-dose tPA administration leads to a substantial response rate although the risk of bleeding remains unclear. A prospective multicenter trial of low-dose thrombolytic therapy in children with acute DVT is warranted.

The use of elastic compression stockings for post-thrombotic syndrome in a child

Post-thrombotic syndrome (PTS) is a potential complication following deep vein thrombosis (DVT) in children. Guidelines for management of PTS in children are non-existent. The absence of guidelines may limit the use of elastic compression stockings (ECS), offered for prevention and treatment of PTS in adults. We report the case of a 6-year-old, who developed PTS following a presumed line-related lower limb DVT, with dramatic improvement in functional status with ECS use. The presented case highlights the subtle nature of symptoms, potential benefits and limitations of ECS use for PTS, and current lack of evidence in children.

Thrombosis in childhood acute lymphoblastic leukaemia: epidemiology, aetiology, diagnosis, prevention and treatment

Acute lymphoblastic leukaemia (ALL) is the most common malignancy associated with venous thromboembolism (VTE) in children. The prevalence of symptomatic VTE ranges from 0% to 36%, and the variation can be explained, at least in part, by differences in chemotherapeutic protocols. The mechanism for increased risk of VTE is associated with alterations in the haemostatic system by use of L-asparaginase (ASP) alone or in combination with vincristine or prednisone, presence of central venous lines (CVLs) and/or inherited thrombophilia. The children at greatest risk are generally those receiving Escherichia coli ASP concomitant with prednisone. The majority of symptomatic VTEs occur in the central nervous system or in the upper venous system. In the majority of cases, asymptomatic VTEs are associated with CVLs. External CVLs are affected more often than internal CVLs. Evidence-based guidelines on prevention and treatment guidelines for ALL-related VTE are lacking, and carefully designed clinical trials are needed urgently.

Heparin-bonded central venous catheters do not reduce thrombosis in infants with congenital heart disease: a blinded randomized, controlled trial

BACKGROUND

Infants with congenital heart disease who require central venous lines are at increased risk of thrombosis. Heparin-bonded catheters provide protection from thrombotic events in some children. However, heparin-bonded catheters may not be as effective in infants </=1 year old because of other potential risk factors (smaller vessel size, longer duration of catheter use). No studies have assessed the benefit of heparin-bonded catheters in such specific high-risk populations. The objective of this study was to assess the efficacy of heparin-bonded catheters for preventing thrombosis in infants aged </=1 year with congenital heart disease.

STUDY DESIGN

This study was designed as a randomized, controlled, blinded single-center trial. Infants </=1 year old with congenital heart disease requiring a central venous line for clinical care were randomly assigned to receive either a heparin-bonded catheter or a standard non-heparin-bonded catheter. Catheters were visually indistinguishable. The primary outcome was incidences of both silent and clinically noticeable thrombosis confirmed by ultrasound. Ultrasounds were reviewed by a blinded central adjudication committee. Interim analysis was performed after enrollment of 97 patients.

RESULTS

Eighty-seven patients were evaluable (41 of the patients were female). Thrombotic events occurred in 17 (42.5%) of 40 patients in the non-heparin-bonded catheter group and in 21 (44.7%) of 47 patients in the heparin-bonded catheters group. The study was stopped when the interim analysis showed convincing evidence for no difference between groups over the alternative hypothesis of 50% risk reduction.

CONCLUSIONS

Infants with congenital heart disease are at significant risk of both silent and clinically identified thrombosis. There seems to be no advantage in using heparin-bonded catheters in infants </=1 year of age.