Definition of post-thrombotic syndrome following lower extremity deep venous thrombosis and standardization of outcome measurement in pediatric clinical investigations

Hemostatic and thrombotic disorders in the pediatric patient

This review focuses on significant advances in the field of pediatric hemostasis and thrombosis, with a focus on published studies within the past decade. The evaluation and management of patients with excessive bleeding remain cornerstones of consultative hematology. We will describe the development of validated bleeding assessment tools relevant to pediatric practice, laboratory advances in the evaluation of von Willebrand disease, and a shift in clinical practice regarding the interpretation of normal coagulation studies in patients with significant bleeding phenotypes. There have also been critical advances in the management of hemostatic disorders. This review highlights new treatment paradigms in hemophilia and the rise of multidisciplinary medical homes for women living with bleeding disorders. Given the continued increase in the incidence of thrombosis, particularly in the hospital setting, a full call to arms against pediatric venous thromboembolism is now essential. We will describe recently completed clinical trials of direct oral anticoagulants in children and adolescents and ongoing work to elucidate the appropriate duration of therapy for children with provoked thrombosis. Recent work regarding the prevention of pediatric venous thromboembolism is highlighted, including studies of thromboprophylaxis and the development of risk prediction models for hospital-acquired thrombosis. Finally, we review advances in our understanding of thrombotic sequelae and the need for continued refinement of our evaluation tools. Despite the significant advances in pediatric hemostasis and thrombosis over the past decade, many unanswered questions remain for the next generation of investigators.

Effect of Anticoagulant Therapy for 6 Weeks vs 3 Months on Recurrence and Bleeding Events in Patients Younger Than 21 Years of Age With Provoked Venous Thromboembolism: The Kids-DOTT Randomized Clinical Trial

Importance

Among patients younger than 21 years of age, the optimal duration of anticoagulant therapy for venous thromboembolism is unknown.

Objective

To test the hypothesis that a 6-week duration of anticoagulant therapy for provoked venous thromboembolism is noninferior to a conventional 3-month therapy duration in patients younger than 21 years of age.

Design, Setting, and Participants

Randomized clinical trial involving 417 patients younger than 21 years of age with acute, provoked venous thromboembolism enrolled at 42 centers in 5 countries from 2008-2021. The main exclusions were severe anticoagulant deficiencies or prior venous thromboembolism. Patients without persistent antiphospholipid antibodies and whose thrombi were resolved or not completely occlusive upon repeat imaging at 6 weeks after diagnosis underwent randomization. The final visit for the primary end points occurred in January 2021.

Interventions

Total duration for anticoagulant therapy of 6 weeks (n = 207) vs 3 months (n = 210) for provoked venous thromboembolism.

Main Outcomes and Measures

The primary efficacy and safety end points were centrally adjudicated symptomatic recurrent venous thromboembolism and clinically relevant bleeding events within 1 year blinded to treatment group. The primary analysis was noninferiority in the per-protocol population. The noninferiority boundary incorporated a bivariate trade-off that included an absolute increase of 0% in symptomatic recurrent venous thromboembolism with an absolute risk reduction of 4% in clinically relevant bleeding events (1 of 3 points on the bivariate noninferiority boundary curve).

Results

Among 417 randomized patients, 297 (median age, 8.3 [range, 0.04-20.9] years; 49% female) met criteria for the primary per-protocol population analysis. The Kaplan-Meier estimate for the 1-year cumulative incidence of the primary efficacy outcome was 0.66% (95% CI, 0%-1.95%) in the 6-week anticoagulant therapy group and 0.70% (95% CI, 0%-2.07%) in the 3-month anticoagulant therapy group, and for the primary safety outcome, the incidence was 0.65% (95% CI, 0%-1.91%) and 0.70% (95% CI, 0%-2.06%). Based on absolute risk differences in recurrent venous thromboembolism and clinically relevant bleeding events between groups, noninferiority was demonstrated. Adverse events occurred in 26% of patients in the 6-week anticoagulant therapy group and in 32% of patients in the 3-month anticoagulant therapy group; the most common adverse event was fever (1.9% and 3.4%, respectively).

Conclusions and Relevance

Among patients younger than 21 years of age with provoked venous thromboembolism, anticoagulant therapy for 6 weeks compared with 3 months met noninferiority criteria based on the trade-off between recurrent venous thromboembolism risk and bleeding risk.

Trial Registration

ClinicalTrials.gov Identifier: NCT00687882.

Venous Thromboembolism among Critically Ill Children: A Narrative Review

Venous thromboembolism (VTE) is a leading cause of morbidity and mortality among hospitalized patients, including children. In recent years, it has become clear that hospitalization and critical illness bestow an increased VTE risk in pediatrics and relate to mortality and life-limiting comorbidities. For critically ill children, reported rates of VTE vary by study sampling techniques, presence of inherited or acquired thrombophilia, acute and chronic immobility, underlying illness prompting hospitalization, and clinical factors related to illness severity such as central venous catheterization, length of stay, mechanical ventilation, and patient age. Accordingly, critically ill children with new signs of venous congestion, acute inflammation, or unexplained acute organ dysfunction should be routinely evaluated for VTE. This narrative review summarizes recent and historical literature regarding risk factors, prevention, presentation, treatment, and outcomes of VTE in critically ill children. In addition, we identify knowledge gaps and priorities for future collaborative research on this vital condition. Special attention is given to the clinical trial opportunities, challenges, and ongoing efforts in thromboprophylaxis in critically ill children, including those hospitalized for disease related to novel coronavirus (COVID-19) and multisystem inflammatory disease in children.

Physical activity in children at risk of postthrombotic sequelae: a pilot randomized controlled trial

Increased physical activity is protective against worsening of postthrombotic syndrome (PTS) in adults. We assessed patient eligibility, consent, adherence, and retention rates in a pilot trial of prescribed physical activity following venous thromboembolism (VTE) in children. Secondary objectives were to describe the within-subject changes in PTS, quality of life, and coagulation biomarkers before and after the intervention in each group. We enrolled and randomized patients between 7 and 21 years of age to the physical activity group or the standard care (education-only) group in a 1:1 allocation ratio. The physical activity group wore a Fitbit for 4 weeks to determine habitual activity and then increased activity over an 8-week "active" period, followed by a 4-week "do-as-you-wish" period. Two hundred thirty-five children were diagnosed with VTE; 111 patients were screened, of whom 40 (36%) met study eligibility criteria. Of these, 23 (57%) consented to participate and were randomized (Fitbit,11; standard group, 12). The trial was of greater interest to overweight and obese children, as they comprised 83% of consented patients. Only 33% adhered to the activity prescription, and 65% (15/23) completed the trial. The PTS scores (P = .001) improved in the physical activity group compared with the education-only group. It is feasible to enroll and randomize pediatric VTE patients to a prescribed physical activity regimen 3 months following VTE. Metrics for adherence to enhanced physical activity and retention were not met. These results provide the rationale to explore low adherence and retention rates before moving forward with a larger trial of exercise training following VTE. This trial was registered at www.clinicaltrials.gov as #NCT03075761.

Prevalence of post-thrombotic syndrome in a cohort of upper extremity vein thrombosis

OBJECTIVE

Post-thrombotic syndrome (PTS) is one of the main complications that occurs after venous thrombosis. There are few data on the proportion of patients that will develop upper extremity PTS (UE-PTS) after upper extremity venous thrombosis (UEVT). The main objective of the study was to assess the prevalence of PTS in a UEVT cohort and to identify predictive factors of UE-PTS.

METHODS

This study included patients with a history of proximal or arm UEVT, diagnosed on duplex ultrasound examination, between January 1, 2015, and December 31, 2017, in a university hospital. After UEVT, each patient was evaluated by a prospective standardized recording of clinical manifestations and duplex ultrasound examination in case of upper limb symptoms. UE-PTS was defined as a modified Villalta score of 4 or higher.

RESULTS

Ninety-two patients were included; 68 (73.9%) had deep vein thrombosis (DVT) and 24 (19.2%) arm superficial vein thrombosis. Thirteen patients had PTS (14.1%), 12 (17.6%) in the DVT group and 1 (4.2%) in the superficial vein thrombosis group. There was a history of DVT in 92.3% of the cases of PTS. PTS was more frequent in patients with strokes with limb movement reduction (P = .01). On multivariate Cox analysis, a history of stroke (hazard ratio, 5.4; 95% confidence interval, 1.46-20.22; P = .01) was predictive of UE-PTS.

CONCLUSIONS

UE-PTS occurred in 14.1% of cases after UEVT. Stroke with a decrease in limb movement was a predictor of developing PTS. Diagnostic criteria should be established for UE-PTS and prospective studies are needed to improve the description and management of UE-PTS.

Validation of Outcome Instruments for Pediatric Postthrombotic Syndrome: Introducing the Peds-VEINES-QOL, a New Health-Related Quality of Life Instrument

BACKGROUND

 There is need for validated outcome measures for postthrombotic syndrome (PTS) following pediatric venous thromboembolism (VTE), with a focus on quality of life (QoL).

AIMS

 This article assesses reliability and validity of two PTS and two QoL scales for children following lower extremity VTE.

METHODS

 Pediatric patients following lower extremity VTE were recruited from three thrombosis clinics. The Manco-Johnson (MJ) and the modified Villalta (MV) PTS scales were compared with each other and with the generic pediatric health-related QoL, PedsQL, and a newly developed pediatric venous-specific QoL, the Peds-VEINES-QOL.

RESULTS

 Eighty children following VTE and 60 healthy control children were enrolled. Internal consistency measured by Cronbach's α was high for the two QoL scales, and moderate for the two PTS scales. Inter-rater reliability using intraclass correlation coefficients was moderate to high for the MJ, MV, and Peds-VEINES-QOL, and moderate for the PedsQL. Evidence of high internal consistency by Cronbach's α coefficients, and moderate to high interitem correlations support the premise that a single construct was measured by each instrument. Correlations between the four instruments indicate convergent validity.

CONCLUSION

 The MJ and MV scales detect similar outcomes in children following VTE. As used, the MJ is slightly more sensitive to QoL because a positive diagnosis requires pain which is the leading factor in reduced QoL following deep vein thrombosis. When using the MV, a requirement for pain or abnormal use to diagnose PTS would make the MV a better predictor of QoL.

Predictors of postthrombotic syndrome in pediatric thrombosis: A systematic review and meta-analysis of the literature

BACKGROUND

Postthrombotic syndrome (PTS) is a significant complication of pediatric deep venous thrombosis (DVT). There is a gap in the understanding of the risk factors associated with the development of pediatric PTS preventing the early identification of those patients at greatest risk, and the development of risk-stratified interventions.

OBJECTIVES

To conduct a systematic review and meta-analysis of the literature on prognostic factors for PTS development in pediatric patients.

METHODS

A systematic search of MEDLINE, EMBASE, and the Cochrane Library from 1960 to December 2018 was performed. Eligible studies reported at least one prognostic factor for PTS development in patients < 21 years of age with a radiographically confirmed DVT. To be included in the meta-analysis, prognostic factors had to be reported in at least three published studies.

RESULTS AND CONCLUSIONS

Twelve studies (n = 1160 patients) met criteria for inclusion. Ninety-three percent of patients with an extremity DVT (n = 1076) were assessed for PTS. PTS developed in 40% (n = 434) of these patients. Central venous catheter-associated DVT (odds ratio [OR], 1.8; 95% confidence interval [CI], 1.08-2.98), complete veno-occlusion (OR, 1.89; 95% CI, 1.04-3.46), and incomplete DVT resolution (OR, 2.07; 95% CI, 1.4-3.07) were identified as candidate prognostic factors for pediatric PTS. These findings should be interpreted in the context of the heterogeneity of the included studies and the limitations of current pediatric PTS assessment tools. Further, the predictive value of these prognostic factors will need to be validated in future collaborative prospective multicenter studies that maximize the homogeneity of pediatric DVT patients.

Safety of dabigatran etexilate for the secondary prevention of venous thromboembolism in children

This open-label, single-arm, prospective cohort trial is the first phase 3 safety study to describe outcomes in children treated with dabigatran etexilate for secondary venous thromboembolism (VTE) prevention. Eligible children aged 12 to <18 years (age stratum 1), 2 to <12 years (stratum 2), and >3 months to <2 years (stratum 3) had an objectively confirmed diagnosis of VTE treated with standard of care (SOC) for ≥3 months, or had completed dabigatran or SOC treatment in the DIVERSITY trial (NCT01895777) and had an unresolved clinical thrombosis risk factor requiring further anticoagulation. Children received dabigatran for up to 12 months, or less if the identified VTE clinical risk factor resolved. Primary end points included VTE recurrence, bleeding events, and mortality at 6 and 12 months. Overall, 203 children received dabigatran, with median exposure being 36.3 weeks (range, 0-57 weeks); 171 of 203 (84.2%) and 32 of 203 (15.8%) took capsules and pellets, respectively. Overall, 2 of 203 children (1.0%) experienced on-treatment VTE recurrence, and 3 of 203 (1.5%) experienced major bleeding events, with 2 (1.0%) reporting clinically relevant nonmajor bleeding events, and 37 (18.2%) minor bleeding events. There were no on-treatment deaths. On-treatment postthrombotic syndrome was reported for 2 of 162 children (1.2%) who had deep vein thrombosis or central-line thrombosis as their most recent VTE. Pharmacokinetic/pharmacodynamic relationships of dabigatran were similar to those in adult VTE patients. In summary, dabigatran showed a favorable safety profile for secondary VTE prevention in children aged from >3 months to <18 years with persistent VTE risk factor(s). This trial was registered at www.clinicaltrials.gov as #NCT02197416.

A bibliometric analysis of publications on venous thromboembolism in children from 1988 to 2019

INTRODUCTION

Venous thromboembolism (VTE) in children not only imposes a heavy burden on the medical resources and economy of the society, but also seriously affects the growth and development of children, even threaten children's lives. A large number of publications have been performed in this field in recent years. In this bibliometric analysis, publications on VTE in children were examined and analyzed to explain the present research hotspots.

METHODS

Articles related to VTE in children published in the PubMed database from 1988 to June 18, 2019 were selected as the research sample. BICOMB software was used to retrieve the annual publications, journals, journal source countries and the high-frequency major medical subject headings (MeSH) terms on the articles. Then, the co-word matrix was constructed by BICOMB using the selected high-frequency MeSH terms. Next, gCLUTO software was used to analyze the matrix by double clustering and visual analysis in a strategy of hotspot identification. In addition, CiteSpace software was used to perform the knowledge map of co-authors to explore the core authors.

RESULTS

One thousand seven hundred seventy-nine articles on VTE in children were obtained. Seven hundred ninety academic journals distributed in 58 countries have published articles on VTE in children, and the developed countries and the United States were the major force in the journal source countries. Nowak-Göttl U occupied an important position in this field. We constructed a co-word matrix composing of 37 high-frequency MeSH terms, generated visual matrix and visual hill, and classified the hot-spots into 5 aspects based on 8 categories.

CONCLUSION

The results show that the research trend of children's VTE has been increasing gradually, and the sound achievement has been obtained in these hotspots in relation to the area of inherited thrombophilia, prevention and control, treatment, diagnosis, prevalence, risk factors, and complication study. However, there is a lack of communication and cooperation in this field, and the gap of national and regional research results is huge. To sum up, this study provides evidence and guidance for researchers, clinicians, and educators.

Reduced Physical Activity Levels in Children after a First Episode of Acute Venous Thromboembolism

OBJECTIVE

To assess physical activity in children following acute venous thromboembolism (VTE), examine predictors of reduced physical activity and its relationship to post-thrombotic syndrome.

STUDY DESIGN

Using a case-control study design, we enrolled 44 children with acute VTE, and compared physical activity using the Godin-Shephard Leisure-Time Physical Activity Questionnaire and health-related quality of life at 3 and 6 months after diagnosis relative to 44 age- and sex-matched controls. We assessed post-thrombotic syndrome scores using the Manco-Johnson Instrument to measure symptoms and signs attributed to sequelae of DVT in cases.

RESULTS

The physical activity of VTE cases was decreased at 3 months after diagnosis (36.6 ± 29.0 vs 56.8 ± 25.0; P = .002), but the differences disappeared at 6 months (57.5 ± 39.0 vs 56.8 ± 25.0; P = .60) relative to controls. At 3 and 6 months after diagnosis, overall, 70% and 50% of VTE cases were below their pre-VTE physical activity levels; providers did not address physical activity in the majority. In multivariable analysis, physical activity of cases was lower by 32 points for completely veno-occlusive thrombosis at diagnosis, 11 points for a diagnosis of pulmonary embolism relative to DVT, and increased by 0.72 points for every unit increase in health-related quality of life score. Physical activity at 3 months after diagnosis did not predict the short-term risk of post-thrombotic syndrome.

CONCLUSIONS

VTE limits physical activity in children in the first 3 months after the acute event, but the differences were nonexistent at 6 months. Only 50 percent of VTE survivors resume their pre-VTE physical activity levels within 6 months after diagnosis.

Post-thrombotic syndrome in children: Measurement properties of CAPTSure, a new diagnostic tool

BACKGROUND

CAPTsure (Clinical Assessment of PTS) is a new tool for diagnosis and severity rating of pediatric postthrombotic syndrome (PTS). Our objective was to test the reliability, measurement error, and minimal detectable change of CAPTSure.

METHODS

Children aged newborn to 18 years who sustained upper extremity or lower extremity deep vein thrombosis (DVT) were enrolled ≥ 6 months after DVT diagnosis. Patients were assessed by 2 raters to determine the reliability of the clinician assessment component (CC) of CAPTSure. Patients/proxies completed CAPTSure at baseline and approximately 2 weeks later to assess test-retest reliability of the symptoms component (SC).

RESULTS

Of 148 patients enrolled in the study; 30 had sustained either bilateral or both upper and lower extremity DVT. Hence, 178 extremities were assessed for PTS signs (86 upper extremity, 92 lower extremity). Intraclass correlation coefficient (ICC) for the CC was 0.89 (95% confidence interval [CI], 0.84-0.93) for upper extremity and 0.88 (95% CI, 0.83-0.92) for lower extremity. Nonclinicians performed 59% of measurements. Ninety-eight patients completed the SC at baseline and follow-up, for a total of 60 upper extremity and 61 lower extremity assessments. ICC for the SC was 0.89 (95% CI, 0.84-0.93) for upper extremity and 0.92 (0.87-0.95) for lower extremity. ICC for CAPTSure was 0.92 (95% CI, 0.87-0.95) for upper extremity and 0.93 (95% CI, 0.88-0.95) for lower extremity assessment. Measurement error ranged between 1.7 and 4.3 of 100 points. A change of approximately 11 of 100 points in CAPTSure score would be required to be confident that there was a change in PTS severity.

CONCLUSION

CAPTSure has excellent reliability and a small measurement error, even when applied by nonhematologists.

Characterization of Post-Thrombotic Syndrome in Children with Cardiac Disease

OBJECTIVE

To assess the validity of existing clinical scales assessing the presence of physical and functional abnormalities for diagnosing post-thrombotic syndrome (PTS) in children, including specific evaluation of use in children with congenital heart disease (CHD).

STUDY DESIGN

One hundred children aged >2 years (average age, 6 years), including 33 with CHD and previously proven extremity deep vein thrombosis (DVT), 37 with CHD and no previous DVT, and 30 healthy siblings, were blindly assessed for PTS using the modified Villalta Scale (MVS). All patients aged <6 years underwent neurodevelopmental testing and an age-appropriate quality of life assessment.

RESULTS

The MVS identified mild PTS in 20 children and moderate PTS in 1 child (including 14 of 33 [42%] in the CHD/DVT group, 5 of 37 [14%] in the CHD/no DVT group, and 2 of 30 controls [7%]). The diagnosis of PTS was confirmed clinically in 14 patients, all of whom had previous thrombosis and 1 of whom was MVS-negative. MVS had an accuracy of 91% and performed reasonably well as a screening tool but poorly as a diagnostic tool. MVS reliability was acceptable. Children with PTS had similar quality of life as those without PTS but had higher rates of neurodevelopmental delays in gross motor skills (70% vs 24%; P = .02) and problem-solving indicators (60% vs 15%; P = .008).

CONCLUSIONS

Using the MVS scale for PTS screening in children with CHD is feasible and reliable, and the scale has good correlation with a clinical diagnosis of PTS despite a high prevalence of false-positive findings. Further research is needed to determine the clinical relevance of PTS in this population.

Thrombosis in Children: Approach to Anatomic Risks, Thrombophilia, Prevention, and Treatment

Pediatric venous thromboembolism (VTE) is increasing in incidence but minimal data exist for best practices regarding therapy, use of thrombophilia testing, and management of long-term complications. Classification schema use anatomic location and presence of clinical or thrombophilic inciting factors. There are a small number of risk-assessment and risk-modeling systems for incident VTE, but all suffer from low numbers, single-institution design, and lack of prospective validation. Acute treatment is limited to heparin products and thrombolysis may be indicated in specific situations. In addition, chronic postthrombotic comorbidities are expected to increase in incidence and lack evidence-based treatment paradigms.

Characteristics of pain, other symptoms and function in pediatric post-thrombotic syndrome

ESSENTIALS

BACKGROUND

Symptoms and function in pediatric post-thrombotic syndrome (PTS) remain poorly characterized.

METHODS

The present cross-sectional study describes the characteristics of pain, other symptoms, and impaired function in pediatric PTS in a cohort of children with history of upper or lower limb deep vein thrombosis and PTS diagnosis. The frequency of clinical findings was compared between patients with and without pain, and between patients with upper and lower extremity PTS.

RESULTS

Seventy-eight children were included in the study. The most common PTS symptoms were pain, tired limb and heaviness. Symptoms were usually reported to occur at mid-day or later and were typically triggered by exercise. Half the patients reported impaired endurance. Pain was reported by 45% of patients and was usually mild-moderate. Heaviness, tightness, tired limb, paresthesia, self-reported limb edema, and impaired endurance were most common in patients with than in patients without pain. Conversely, activity and participation scores, skin redness, and clinician-assessed limb edema did not differ between patients with and without pain. Lastly, there was no difference in pain intensity or frequency of paresthesia, swelling, heaviness, or impaired endurance when comparing the upper and lower extremities.

CONCLUSION

Tired limb, heaviness, pain, and impaired endurance were the most frequent clinical findings in pediatric PTS. Frequency of symptoms and pain intensity did not differ between upper and lower extremities. Pain was associated with the presence of other symptoms and impaired function, but not with activity limitation and participation restriction. Better tools are needed to measure these two latter aspects of health.

NEOnatal Central-venous Line Observational study on Thrombosis (NEOCLOT): evaluation of a national guideline on management of neonatal catheter-related thrombosis

BACKGROUND

In critically ill (preterm) neonates, central venous catheters (CVCs) are increasingly used for administration of medication or parenteral nutrition. A serious complication, however, is the development of catheter-related thrombosis (CVC-thrombosis), which may resolve by itself or cause severe complications. Due to lack of evidence, management of neonatal CVC-thrombosis varies among neonatal intensive care units (NICUs). In the Netherlands an expert-based national management guideline has been developed which is implemented in all 10 NICUs in 2014.

METHODS

The NEOCLOT study is a multicentre prospective observational cohort study, including 150 preterm and term infants (0-6 months) admitted to one of the 10 NICUs, developing CVC-thrombosis. Patient characteristics, thrombosis characteristics, risk factors, treatment strategies and outcome measures will be collected in a web-based database. Management of CVC-thrombosis will be performed as recommended in the protocol. Violations of the protocol will be noted. Primary outcome measures are a composite efficacy outcome consisting of death due to CVC-thrombosis and recurrent thrombosis, and a safety outcome consisting of the incidence of major bleedings during therapy. Secondary outcomes include individual components of primary efficacy outcome, clinically relevant non-major and minor bleedings and the frequency of risk factors, protocol variations, residual thrombosis and post thrombotic syndrome.

DISCUSSION

The NEOCLOT study will evaluate the efficacy and safety of the new, national, neonatal CVC-thrombosis guideline. Furthermore, risk factors as well as long-term consequences of CVC-thrombosis will be analysed.

TRIAL REGISTRATION

Trial registration: Nederlands Trial Register NTR4336 . Registered 24 December 2013.

Thrombophilia testing in children: What and when should be tested?

Venous thrombosis (VTE) in children is gaining increased awareness and apart from underlying medical conditions, recently reported systematic reviews on pediatric VTE (70% provoked) have shown significant associations between thrombosis and presence of inherited thrombophilic risk factors (IT), such as protein C-, protein S- and antithrombin deficiency, mutations of factor 5 (F5: rs6025) and factor 2 (F2: rs1799963), even more pronounced when combined IT were involved. Although we have learned more about the pathophysiology of VTE with the increased discovery of IT evidence is still lacking as to whether IT influence the clinical outcome in pediatric VTE. It still remains controversial as to whether children with VTE or offspring from thrombosis-prone families benefit from IT screening. Thus, IT testing in children should be individualized. If the decision "pro screening" is discussed as an appropriate option in adolescents with unprovoked VTE and in children with a positive family history for VTE screening should be performed in a specialized coagulation unit for acquired or inherited and prothrombotic defects based on the individual population background. Apart from the laboratory assessment for the presence/absence of lupus anticoagulants and antiphospholipid antibodies screening should be performed beyond the acute VTE onset and after withdrawal of anticoagulant medication possibly influencing laboratory results.

Markers of coagulation activation, inflammation and fibrinolysis as predictors of poor outcomes after pediatric venous thromboembolism: A systematic review and meta-analysis

BACKGROUND

Sequelae of venous thromboembolism (VTE) in children include recurrence, development of post thrombotic syndrome (PTS) when venous return from a limb is affected and chronic thromboembolic pulmonary hypertension (CTEPH) after pulmonary embolism. Identification of laboratory-based risk factors may be useful for individualized risk assessment for VTE sequelae. Coagulation activation and inflammation may contribute to their pathophysiology. We performed a systematic review to investigate the association between biomarkers of coagulation activation, inflammation and fibrinolysis and adverse VTE outcomes in children and young adults.

METHODS

A systematic search of electronic databases, PubMed (NIH), EMBASE (Ovid), Web of Science (Thompson Reuters), and SCOPUS (Elsevier) for studies published through November 2016 was conducted using "VTE" including MeSH terms for "coagulation activation," "inflammation" and "fibrinolysis," with no limit on publication date. A study was eligible for inclusion when it evaluated patients (< 21years) with VTE and biomarkers of coagulation activation, inflammation, and fibrinolysis and assessed for their association with development of adverse thrombotic outcomes. A modified Newcastle Ottawa Scale was applied to examine the quality of included studies.

RESULTS

Our search strategy yielded 200 references. A total of 3 cohort studies representing 220 patients with VTE were included. Two authors independently assessed all references for inclusion. Three studies (2 prospective cohort and one mixed cohort study) were identified that reported on biomarkers of coagulation activation, inflammation and fibrinolysis, checked at least once after VTE diagnosis and assessed association with primary outcomes of recurrent VTE, PTS and CTEPH. Studies varied with regards to definition of outcomes, the type of biomarkers measured and time point of measurement. We were unable to meta-analyze results due to marked clinical heterogeneity and <3 studies available for each biomarker. Descriptively, a significant association was found for elevated plasma levels of FVIII and D-dimer for a compound outcome of PTS, recurrence and progression in one study, and positive lupus anticoagulant at DVT diagnosis and subsequent PTS by another study. No studies were found for CTEPH.

CONCLUSIONS

Elevated D-dimer, FVIII and lupus anticoagulant show promise for predicting recurrent VTE and PTS in children and young adults. Further research is needed to elucidate whether these markers might be useful to predict development of adverse outcomes after VTE in children.

Post thrombotic syndrome following deep vein thrombosis in paediatric patients

Background Although well characterised in adults, less is known about post-thrombotic syndrome in children. In this review, current knowledge regarding paediatric post-thrombotic syndrome is summarised, with particular emphasis on pathophysiology, aetiology, diagnosis and management. Methods A Medline literature review was performed using search terms 'post thrombotic syndrome', 'post phlebitic syndrome', paediatric and children. Relevant articles were identified and included for summation analysis. Results The incident of paediatric venous thromboembolism is rising. Deep vein thrombosis can cause venous hypertension through a combination of venous reflux, venous obstruction and impairment of the calf muscle pump, leading to development of post-thrombotic syndrome. In children, this is more likely to occur if deep vein thrombosis diagnosis and treatment are delayed, if a higher number of vessels are involved, and if factors such as D-dimer are elevated at diagnosis and throughout treatment. Post-thrombotic syndrome occurs in about 26% of paediatric deep vein thrombosis, though the results of individual studies vary widely. A number of tools exist to diagnose paediatric post-thrombotic syndrome, including the modified Villalta scale and Manco-Johnson instrument. Once post-thrombotic syndrome develops, the mainstay of treatment remains supportive, with little evidence of benefit from pharmacological measures. Conclusion Surgical or interventional treatment is not advised except in exceptional cirumstances, due to variable prognosis of PTS in paediatric populations with rising incidence of paediatric venous thromboembolism, it follows that the prevalence of post-thrombotic syndrome in children may also increase. Evidence-based venous thromboembolism prevention strategies need to be implemented for prevention of deep vein thrombosis, but when it does occur, deep vein thrombosis requires prompt and effective treatment to prevent post-thrombotic syndrome. Optimum treatment strategies for post-thrombotic syndrome require further investigation.

Epidemiology and Risk Assessment of Pediatric Venous Thromboembolism

The incidence of diagnosed venous thromboembolism (VTE) has been increasing concurrent with advances in technology and medical care that enhance our ability to treat pediatric patients with critical illness or complex multiorgan system dysfunction. Although the overall incidence of VTE is estimated at 0.07-0.49 per 10,000 children, higher rates are observed in specific populations including hospitalized children, those with central venous catheters (CVCs) or patients convalescing from a major surgery. While the absolute number of pediatric VTE events may seem trivial compared to adults, the increasing incidence, associated with increased mortality and morbidity, the availability of novel therapies, and the impact on the cost of care have made investigation of VTE risk factors and prevention strategies a high priority. Many putative risk factors for pediatric VTE have been reported, primarily from single-institution, retrospective studies which lack appropriate methods for verifying independent risk factors. In addition, some risk factors have inconsistent definitions, which vex meta-analyses. CVCs are the most prevalent risk factors but have not consistently been assigned the highest level of risk as defined by odds ratios from retrospective, case-control studies. Few risk-assessment models for hospital-acquired pediatric VTE have been published. Some models focus exclusively on hospitalized pediatric patients, while others target specific populations such as patients with cancer or severe trauma. Multicenter, prospective studies are needed to identify and confirm risk factors in order to create a pediatric risk-assessment tool and optimize preventive measures and reduce unintended harm.

Risk factors for symptomatic venous and arterial thromboembolism in newborns, children and adolescents - What did we learn within the last 20years?

Venous thrombosis (VTE) in children is increasingly diagnosed, as advanced medical care has increased treatment intensity of hospitalized pediatric patients. The aim of this review was to summarize the data available and to discuss the controversial issue of thrombophilia screening in the light of the pediatric data available. Follow-up data for VTE recurrence in children suggest a recurrence rate between 3% (neonates) and 21% in individuals with unprovoked VTE. Apart from underlying medical conditions, recently reported systematic reviews on pediatric VTE (70% provoked) have shown significant associations between thrombosis and presence of protein C-, protein S- and antithrombin deficiency, factor 5 (F5: rs6025), factor 2 (F2: rs1799963), even more pronounced when combined inherited thrombophilias [IT] were involved. The F2 mutation, protein C-, protein S-, and antithrombin deficiency did also play a significant role at VTE recurrence. Although we have learned more about the pathophysiology of VTE with the increased discovery of IT evidence is still lacking as to whether IT influence the clinical outcome in pediatric VTE. It still remains controversial as to whether children with VTE or offspring from thrombosis-prone families benefit from IT screening. Thus, IT testing in children should be individualized.

The post-thrombotic syndrome

The post-thrombotic syndrome (PTS) is a frequent, sometimes disabling complication of deep vein thrombosis (DVT) that reduces quality of life and is costly. This article discusses risk factors for PTS after DVT and available means to prevent and treat PTS, with a focus on new information in the field. After DVT, PTS will develop in 20% to 50% of patients, and severe PTS, including venous ulcers, will develop in 5% to 10%. The principal risk factors for PTS are anatomically extensive DVT, recurrent ipsilateral DVT, persistent leg symptoms 1 month after acute DVT, obesity, and older age. By preventing the initial DVT and ipsilateral DVT recurrence, primary and secondary prophylaxes of DVT will prevent cases of PTS. Based on recent evidence from a large multicenter trial, routine use of elastic compression stockings (ECS) after DVT to prevent PTS is not advocated, but in patients with DVT-related leg swelling that is bothersome, a trial of ECS is reasonable. Selecting DVT patients for catheter-directed thrombolytic treatment as a means of preventing PTS should be done on a case-by-case basis, with a focus on patients with extensive thrombosis, recent symptoms onset, and low bleeding risk. For patients with established PTS, daily use of ECS may help to relieve symptoms and edema. Intermittent compression devices can be tried in patients with moderate-to-severe PTS whose symptoms are inadequately controlled with ECS alone. A supervised exercise training program may improve PTS symptoms. Management of post-thrombotic ulcers should ideally involve a multidisciplinary approach. Important areas for future research are summarized.

Development of CAPTSureTM - a new index for the assessment of pediatric postthrombotic syndrome

Essentials We developed a discriminative and evaluative index for pediatric postthrombotic syndrome (PTS). A Delphi-survey was used for item reduction and multi-criteria decision analysis for item weighting. The new index assesses limb PTS based on the relative severity of each sign and symptom. Higher scores related to higher odds of parental dissatisfaction with their child's condition.

SUMMARY

Background Postthrombotic syndrome (PTS) is a complication of deep vein thrombosis defined by the presence of characteristic signs and symptoms. We developed a discriminative and evaluative index for the assessment of upper extremity (UE) and lower extremity (LE) pediatric PTS. Methods The items to be included in the index were voted for by 26 pediatric thrombosis experts invited to participate in a Delphi survey. Subsequent item weighting was based on item importance elicited by the use of multicriteria decision analysis (MCDA); 122 healthcare providers and patients/parents were invited to participate in item weighting. The implications of the overall scores were explored by comparison with PTS diagnosis (independently assessed by two clinical experts) and parental satisfaction/dissatisfaction with their child's current condition. Results Items voted for inclusion by at least 70% of the Delphi survey respondents (81% response rate) were pain, paresthesia, swelling, heaviness, endurance, collateral circulation and arm circumference difference for the UE, and pain, paresthesia, swelling, heaviness, tightness, tired limb, redness/purple or blotchy skin, endurance, ulcers and thigh/calf circumference difference for the LE. Items were then weighted by the use of MCDA (82% response rate). The index had excellent discrimination for patients with/without PTS. For every 10-point increase in index scores (with higher scores being indicative of worse PTS), the odds of parental dissatisfaction increased by 75% and 92% in the UE and LE, respectively. Conclusion We report the development of the CAPTSure™ (index for the Clinical Assessment of Postthrombotic Syndrome in children), which reflects collective judgement of the severity of pediatric PTS. We also provide information on the meaning of the scores.

Postthrombotic syndrome and other outcomes of lower extremity deep vein thrombosis in children

The frequency of PTS, PE, and DVT recurrence was higher in children with Non-LR DVT than in children with LR DVT. Thrombus resolution, DVT triggering event, and sex were predictors of LE PTS in children.

Ultrasound Assisted Endovascular Thrombolysis in Adolescents: 2 Case Reports

Descending iliofemoral thrombosis in children is a rare event. Anticoagulation therapy with low-molecular-weight-heparin is standard of care. However, patency cannot be achieved in all cases, increasing the risk for rethrombosis and postthrombotic syndrome. To reduce the risk of venous valve failure in adults, local catheter-directed thrombolysis is used to reopen vessels. Two adolescent girls (17 and 15 years old) presented with acute descending iliofemoral thrombosis of the left common iliac, external, and common femoral veins. Anticoagulation with enoxaparin was started until insertion of an EkoSonic Mach 4e catheter for ultrasound-assisted local thrombolysis with recombinant tissue plasminogen activator and administration of unfractionated heparin. Success was monitored by increases in D-dimer levels and ultrasound findings. After 24 hours respectively 48 hours, complete recanalization was obtained. No complication occurred except minimal local bleeding. Screening for hereditary thrombophilia revealed a heterozygous antithrombin mutation in 1 girl (ie, the 15-year-old). May-Thurner syndrome was identified in both girls, necessitating stenting of the left common iliac veins and continuation of anticoagulation therapy with enoxaparin and acetylsalicylic acid. No rethrombosis or complications occurred during the follow-up period. Ultrasound-assisted catheter-directed local thrombolysis with the EkoSonic Mach 4e system was effective in achieving immediate recanalization of the occluded veins and should be considered in children experiencing descending iliofemoral thrombosis. The fast recanalization might reduce the incidence of postthrombotic syndrome. May-Thurner syndrome is regularly found in these patients, and if present, requires stenting of the common iliac vein to avoid early reocclusion. However, long-term patency of iliac vein stenting in children remains to be examined.

Comparison of 3 Postthrombotic Syndrome Assessment Scales Demonstrates Significant Variability in Children and Adolescents With Deep Vein Thrombosis

Postthrombotic syndrome (PTS) is an important outcome in children with deep vein thrombosis (DVT). There are several instruments to measure PTS, and no accepted "gold standard." The objective of this cross-sectional prospective study was to compare the prevalence of PTS in patients above 8 years old with a history of DVT using 3 scales: the Villalta scale, a pediatric modification of the Villalta scale, and the Manco-Johnson instrument. Forty-four subjects (22 females) were enrolled; mean age 16.6 years (SD 3.6 y). The majority had a lower extremity DVT. The average duration from DVT to PTS assessment was 2.6 years. The proportion of subjects with PTS using the adult Villalta scale was 11%, which was significantly less than the 66% of patients identified using both pediatric scales (P<0.0001). The majority of patients with PTS as determined by the pediatric scales had mild PTS. There was significant discordance between the prevalence of PTS using the Villalta scale compared with the 2 pediatric scales. This is especially relevant when considering which instrument to use in adolescent patients. This study demonstrates that PTS, as defined by these scales, is not a well-defined or standardized outcome, particularly when comparing adult and pediatric instruments.

Multicenter randomized controlled trial on Duration of Therapy for Thrombosis in Children and Young Adults (the Kids-DOTT trial): pilot/feasibility phase findings

BACKGROUND

Randomized controlled trials (RCTs) on pediatric venous thromboembolism (VTE) treatment have been challenged by unsubstantiated design assumptions and/or poor accrual. Pilot/feasibility (P/F) studies are critical to future RCT success.

METHODS

The Kids-DOTT trial is a multicenter RCT investigating non-inferiority of a 6-week (shortened) versus 3-month (conventional) duration of anticoagulation in patients aged < 21 years with provoked venous thrombosis. Primary efficacy and safety endpoints are symptomatic recurrent VTE at 1 year and anticoagulant-related, clinically relevant bleeding. In the P/F phase, 100 participants were enrolled in an open, blinded-endpoint, parallel-cohort RCT design.

RESULTS

No eligibility violations or randomization errors occurred. Of the enrolled patients, 69% were randomized, 3% missed the randomization window, and 28% were followed in prespecified observational cohorts for completely occlusive thrombosis or persistent antiphospholipid antibodies. Retention at 1 year was 82%. Interobserver agreement between local and blinded central determination of venous occlusion by imaging at 6 weeks after diagnosis was strong (k-statistic = 0.75; 95% confidence interval [CI] 0.48-1.0). The primary efficacy and safety event rates were 3.3% (95% CI 0.3-11.5%) and 1.4% (95% CI 0.03-7.4%).

CONCLUSIONS

The P/F phase of the Kids-DOTT trial has demonstrated the validity of vascular imaging findings of occlusion as a randomization criterion, and defined randomization, retention and endpoint rates to inform the fully powered RCT.

Chronic Complications After Femoral Central Venous Catheter-related Thrombosis in Critically Ill Children

Prescription of thromboprophylaxis is not a common practice in pediatric intensive care units. Most thrombi are catheter-related and asymptomatic, without causing acute complications. However, chronic complications of these (a)symptomatic catheter-related thrombi, that is, postthrombotic syndrome (PTS) and residual thrombosis have not been studied. To investigate these complications, critically ill children of 1 tertiary center with percutaneous inserted femoral central venous catheters (FCVCs) were prospectively followed. Symptomatic FCVC-thrombosis occurred in 10 of the 134 children (7.5%; 95% confidence interval [CI], 2.4-9.5). Only FCVC-infection appeared to be independently associated (P=0.001) with FCVC-thrombosis. At follow-up 2 of the 5 survivors diagnosed with symptomatic thrombosis developed mild PTS; one of them had an occluded vein on ultrasonography. A survivor without PTS had a partial occluded vein at follow-up. Asymptomatic FCVC-thrombosis occurred in 3 of the 42 children (7.1%; 95% CI, 0.0-16.7) screened by ultrasonography within 72 hours after catheter removal. At follow-up, mild PTS was present in 6 of the 33 (18.2%; 95% CI, 6.1-30.3) screened children. Partial and total vein occlusion was present in 1 (3%) and 4 (12%) children, respectively. In conclusion, children on pediatric intensive care units are at risk for (a)symptomatic FCVC-thrombosis, especially children with FCVC-infection. Chronic complications of FCVC-thrombosis are common. Therefore, thromboprophylaxis guidelines are warranted in pediatric intensive care units to minimize morbidity as a result of FCVC-thrombosis.

Outcomes in children with deep vein thrombosis managed with percutaneous endovascular thrombolysis

BACKGROUND

Our center has developed a multidisciplinary approach to percutaneous endovascular thrombolysis with the goal of improving outcomes in children with thrombosis. There is little data describing the safety and efficacy of endovascular thrombolysis and the frequency of post-thrombotic syndrome after thrombolysis in children.

OBJECTIVE

Retrospective analysis of children undergoing percutaneous endovascular thrombolysis to determine (1) the safety and efficacy of this procedure and (2) the frequency of the diagnosis of post-thrombotic syndrome after thrombolysis.

MATERIALS AND METHODS

We reviewed the medical and imaging databases for children who underwent percutaneous endovascular thrombolysis for deep venous thrombosis (DVT) between November 2008 and June 2013 at our institution. Demographic data were reviewed for the technical success and complications of thrombolysis and the last assigned post-thrombotic syndrome score using standardized scoring tools.

RESULTS

Forty-one children ages 3 months to 21 years (median age: 15 years; 44% male) underwent percutaneous endovascular thrombolysis between November 2008 and June 2013. Upper extremity DVT occurred in 13 patients (32%); lower extremity DVT occurred in 28 patients (68%). All 41 patients received thrombolysis grading; 90% of those patients achieved greater than 50% thrombus lysis. Twenty-eight patients received formal post-thrombotic syndrome scoring and 4 (14%) met diagnostic criteria for post-thrombotic syndrome. One major bleeding episode and one pulmonary embolism occurred with no long-term sequelae.

CONCLUSION

Endovascular thrombolysis for DVT in children is safe, effective at thrombus removal and may reduce the incidence of post-thrombotic syndrome. Randomized or larger clinical trials would be needed to determine the long-term benefits of endovascular thrombolysis.

Efficacy of a short course of complex lymphedema therapy or graduated compression stocking therapy in the treatment of post-thrombotic syndrome

Treatment options for established post-thrombotic syndrome (PTS) are limited. Complex lymphedema therapy (CLT), a non-invasive treatment that improves lymphatic flow, may have the potential to improve PTS. We conducted a single-center, investigator-blind, randomized controlled trial of 31 patients with a clinically established diagnosis of PTS and compared the efficacy of graduated compression stockings alone (30-40 mmHg) with CLT, a treatment that includes compression stockings, exercise, patient education, skin care and lymphatic drainage. Primary outcomes were the 1- and 3-month changes in PTS severity by the Villalta score and disease-specific quality of life using the VEINES-QOL (Venous Insufficiency Epidemiological and Economic Study Quality of Life) questionnaire. Analysis was by intent-to-treat. We found from a baseline average score of 9.9 points, CLT reduced mean PTS severity scores by -2.4 points (p=0.02) at the 1-month and -2.3 points (p=0.05) at the 3-month follow-up. Score reductions with stockings only were similar at -2.1 (p=0.03) and -3.3 points (p=0.03) at 1 and 3 months. The differences in score between treatments were not significant. Neither treatment significantly changed the VEINES-QOL score except in patients with severe disease. Patients with moderate to severe PTS derived the greatest benefit from either therapy and the two therapies differentially impacted PTS signs and symptoms. We found a short course of lymphedema therapy and compression stockings offer similar benefit in patients with PTS; however, larger studies are needed to further explore the potential use of CLT in PTS, particularly in patients with more severe disease. ClinicalTrials.gov Identifier: NCT00633971.

Postthrombotic syndrome following upper extremity deep vein thrombosis in children

Upper limb PTS in children depends on DVT pathogenesis (primary vs secondary) and on the age of the patient (neonates vs non-neonates). DVT pathogenesis and thrombus resolution are independent predictors of upper limb PTS in children.

Natural history of deep vein thrombosis in children

OBJECTIVE

To determine the natural history of deep vein thrombosis in children presented with a first episode in the lower extremity veins.

METHODS

Children with objective diagnosis of acute deep vein thrombosis were followed up with ultrasound and clinical examination. Risk factors and clinical presentation were prospectively collected. The prevalence of recurrent deep vein thrombosis and the development of signs and symptoms of chronic venous disease were recorded.

RESULTS

There were 27 children, 15 males and 12 females, with acute deep vein thrombosis, with a mean age of 4 years, range 0.1-16 years. The median follow-up was 23 months, range 8-62 months. The location of thrombosis involved the iliac and common femoral vein in 18 patients and the femoral and popliteal veins in 9. Only one vein was affected in 7 children, two veins in 14 and more than two veins in 6. Recurrent deep vein thrombosis occurred in two patients, while no patient had a clinically significant pulmonary embolism. Signs and symptoms of chronic venous disease were present at last follow-up in 11 patients. There were nine patients with vein collaterals, but no patient developed varicose veins. Reflux was found in 18 veins of 11 patients. Failure of recanalization was seen in 7 patients and partial recanalization in 11. Iliofemoral thrombosis (p = 0.012) and failure to recanalize (p = 0.036) increased significantly the risk for developing signs and symptoms.

CONCLUSIONS

Children with acute proximal deep vein thrombosis develop mild chronic venous disease signs and symptoms at mid-term follow-up and are closely related with iliofemoral thrombosis and failure to recanalization.

Health-related quality of life in children and young adults with post-thrombotic syndrome: results from a cross-sectional study

OBJECTIVE

While post-thrombotic syndrome (PTS) is increasingly recognized in children with a history of deep vein thrombosis (DVT), its impact on the health-related quality of life (HRQoL) is unknown. Our objective was to evaluate the association between the PTS and HRQoL by surveying a cohort of patients treated at our institution for DVT.

MATERIALS/METHODS

All unique pediatric patients (0-18 years) treated for a DVT at the Mayo Clinic during the 15-year period, 1995-2009 were identified. A previously validated PTS survey instrument and age appropriate Pediatric Quality of Life inventory, version 4 (PedsQL 4.0) were mailed to eligible patients. Linear regression models were fit to compare the HRQoL scores between PTS groups (none, mild, moderate/severe), after adjusting for the presence of potential covariates.

RESULTS

Of the 90 respondents, 65 (72%) reported signs and/or symptoms of PTS. Mean age (± SD) at DVT diagnosis and survey completion were 12.8 (± 6.1) and 19.3 (± 7.7) years, respectively. Self-report PedsQL 4.0 module was completed by 79 patients, and 34 guardians completed the parent-proxy module. Patients with moderate to severe PTS reported significantly worse total HRQoL score (mean ± SD, 71.3 ± 13.4) as compared to patients with mild PTS (84.8 ± 14.2) and no PTS (83.4 ± 14) (P = 0.001).

CONCLUSION

Moderate to severe PTS has a significant impact on self-reported HRQoL as measured using the generic PedsQL 4.0. Further research is warranted to develop a venous disease-specific quality of life measure for children with a history of DVT.

Updates in thrombosis in pediatrics: where are we after 20 years?

The incidence of venous thromboembolism (VTE) in the pediatric population is increasing. Technological advances in medicine and imaging techniques, improved awareness of the disease, and longer survival of life-threatening or chronic medical conditions all contribute to the increase in VTE rates. There is a paucity of data on management of VTE based on properly designed clinical trials, but there is significant advancement in the last 2 decades. This review summarizes the progress made in pediatric thrombosis, including epidemiological changes, advances in anticoagulant agents, and outcomes of VTE.