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

The role of coagulation factors VIII, IX and XI in the prediction and mediation of recurrent thrombotic events in children with non-central venous catheter deep vein thrombosis

BACKGROUND

The role of elevated coagulation factors VIII (FVIII), FIX, FXI for the prediction of recurrent thrombotic events in children after an index non-central venous catheter (non-CVC) related deep vein thrombosis (DVT) remains unclear.

OBJECTIVE

This study investigates the predictive role of FVIII, FIX, and FXI for recurrent thrombosis in children with index non-CVC DVTs, and the mediation effect of FVIII on chronic inflammation and recurrent thrombosis.

METHODS

Children aged 0-18 years diagnosed with an index non-CVC related DVT (1993-2020) were included in this single-center retrospective cohort study. Plasma levels of FVIII, FIX, FXI were measured cross-sectionally ≥30 days after the acute DVT. The association between the continuous variables FVIII, FIX, FXI and thrombosis recurrence was investigated using uni- and multivariable logistic regression, adjusting for age, sex, and chronic inflammation. Mediation analysis assessed the role of FVIII as a mediator between chronic inflammation and recurrent thrombosis. Ethics approval was obtained.

RESULTS

A total of 139 children with an index non-CVC related DVT were included. Thirty-eight (27 %) had a recurrent thrombosis at a median of 237 days (P25-P75 65-657 days) after the index DVT. In uni- and multivariable-analysis, FVIII, FIX or FXI did not predict thrombosis recurrence; However, chronic inflammation was an independent predictor. There was no evidence that FVIII mediated the effect of chronic inflammation on thrombosis recurrence.

CONCLUSION

We found no evidence that elevated FVIII, FIX or FXI predicted thrombosis recurrence, or evidence of a mediating role of FVIII. Underlying chronic inflammation predicted venous recurrent thrombotic events in this cohort.

Risk factors and clinical impact of thrombosis during induction chemotherapy for pediatric acute lymphoblastic leukemia: A report from CYP-C

Thromboembolism (TE) is associated with reduced survival in pediatric acute lymphoblastic leukemia (ALL). It has been hypothesized that TE might signal leukemic aggressiveness. The objective was to determine risk factors for TE during ALL induction (TEind ) therapy and whether TEind is associated with treatment refractoriness. This retrospective cohort study using the population-based Cancer in Young People Canada (CYP-C) registry included children <15 years of age diagnosed with ALL (2000-2019) and treated at one of 12 Canadian pediatric centers outside of Ontario. Univariate and multivariable logistic regression models were used to determine risk factors for TEind and whether TEind predicted induction failure and ALL treatment intensification. The impact of TEind on overall and event-free survival was estimated using Cox proportional hazard regression models. The study included 2589 children, of which 45 (1.7%) developed a TEind . Age (<1 year and ≥10 years vs. 1-<10 years), T-cell phenotype, high-risk ALL, and central nervous system involvement were all associated with TEind in univariate analysis. Age and T-cell phenotype remained independent predictors of TEind in multivariable analysis. Induction failure occurred in 53 patients (2.1%). TEind was not associated with induction failure (OR: not estimable) or treatment intensification (adjusted OR [95% CI]: 0.66 [0.26-1.69]). TEind was independently associated with overall survival (adjusted HR [95% CI]: 2.54 [1.20-5.03]) but not event-free survival (adjusted HR [95% CI] 1.86 [0.98-3.51]). In this population-based study of children treated with contemporary chemotherapy protocols, TEind was associated with age and T-cell phenotype and mortality but did not predict induction failure.

Biomarkers in pediatric venous thromboembolism: a systematic review of the literature

BACKGROUND

Accurate prediction of the individual risk of venous thromboembolism (VTE) remains suboptimal in children, and biomarkers are currently not used to stratify the risk of VTE in children.

OBJECTIVES

This study aimed to assess which biological or radiological biomarkers may predict VTE or VTE complications in children.

PATIENTS/METHODS

A literature search was performed for peer-reviewed publications (1990-2022). We included studies addressing the use of biomarkers for patients aged 29 days to 18 years to predict VTE or its complications, including but not limited to TE-related death, VTE recurrence, or postthrombotic syndrome. Given the heterogeneity of the study designs, populations, and outcomes, no quantitative data synthesis was performed.

RESULTS

Forty studies were included, totaling 10,987 participants (median age: 4.7 years). Reports were often lacking critical methodological data, including blood collection method (68% of studies) and timepoints, laboratory testing technique (41%), or primary outcome definition (20%). Forty-six individual biomarkers were assessed for VTE prediction (32 studies, 9525 participants), including d-dimers, fibrinogen, platelet count, white blood cell count, and factor VIII. Albumin, C-reactive protein, d-dimers, factor VIII, and thrombin-antithrombin levels showed promising results for VTE prediction. In 9 studies (1606 participants), no biomarker was consistently predictive of postthrombotic syndrome, VTE persistence, or VTE recurrence in children.

CONCLUSIONS

Several candidate biomarkers were promising in the prediction of VTE in children. Still, discrepancies between different studies and the high risk of bias from the current literature prevent their widespread use in the clinical setting. Further prospective research in various pediatric subpopulations is required.

Unraveling the pathophysiology of lower-limb postthrombotic syndrome in adolescents: a proof-of-concept study

A better understanding of the pathophysiology of pediatric postthrombotic syndrome (PTS) is needed to develop strategies to treat this condition. We investigated calf pump function, exercise capacity, balance in power output, and changes in limb muscle oxygen saturation (SmO2) and fluid content during exercise in 10 pediatric patients with unilateral lower-limb PTS, and in age- and sex-matched controls (1:1-1:2 ratio). Outcomes were investigated using bioimpedance spectroscopy, torque-sensing pedals, and near-infrared spectroscopy during incremental- and constant-load cycling tests. The median age at participation was 17 years (25th-75th percentile, 15-18 years); 68% of participants were females. The median CAPTSure score in the affected leg of affected participants was 35 points (25th-75th percentile, 24-46 points), indicating moderate/severe PTS; 20% of patients had a history of central venous catheter-related thrombosis. Increasing PTS severity was associated with higher calf pump venous volume and higher ejection volume, leading to compensated calf pump performance. We found no evidence of PTS impact on exercise capacity. Leg contribution to power output was similar in affected and unaffected legs. However, the PTS-affected legs showed lower SmO2 during active cycling and recovery with increasing PTS severity, indicating impaired microvascular function in the muscle. These findings suggest that PTS severity is associated with impaired blood flow, presumably from elevated venous pressure during and after exercise. The fact that microvascular function is impaired in young patients with PTS underscores the relevance of developing strategies to mitigate the effects of this chronic vascular disease to minimize its deleterious effects as children grow older.

Role of factor VIII, IX, and XI in venous thrombosis recurrence risk in adults and children: A systematic review

Background

Predicting recurrent venous thromboembolic events (VTEs) is challenging in clinical practice for both adults and children, but it is relevant for clinical management. Identifying laboratory risk factors for VTE recurrence may aid in clinical decision-making.

Objective

The goal of this systematic review is to investigate the predictive role of FVIII, IX, or XI in recurrent VTE in adult and pediatric patients with a first VTE.

Methods

A systematic review of the published literature was conducted in databases MEDLINE In-Process, Other Nonindexed Citations, MEDLINE Epub Ahead of Print, EMBASE Classic + EMBASE (OvidSP), and Cochrane (Wiley). We included observational and interventional studies that comprised adults or children with a first VTE, FVIII, FIX, and/or FXI and objectively confirmed VTE recurrence. The quality in prognosis studies tool was used to assess the risk of bias.

Results

We identified 2177 unique studies, of which 19 were included (18 for adults and 1 for children). The risk of bias was overall low to moderate. The studies were heterogenous with regards to population (provoked/unprovoked primary VTE), exposure (type of assay and cut-off values), and statistical analysis results (measures of association and modeling strategy). In adults, contradictory evidence was found for FVIII and FXI as outcome predictors, while no research could establish if FIX predicts VTE recurrence. Data in pediatrics were limited. Given the extensive heterogeneity of the literature, a meta-analysis was not performed.

Conclusions

Overall, there is contradictory evidence that FVIII, FIX, or FXI predict recurrent VTE in adults and children. Addressing heterogeneity is a relevant aspect to consider in future studies investigating prognostic factors for VTE recurrence.

Functional impact of pediatric postthrombotic syndrome

BACKGROUND

Postthrombotic syndrome (PTS) is the most common complication of deep vein thrombosis (DVT) in children.

OBJECTIVES

We aimed to assess the impact of pediatric PTS on functioning as assessed by movement ability, mobility, functional disability, and physical activity levels in children after diagnosis of limb DVT.

METHODS

Patients aged 8-21 years in follow-up care after objectively documented limb DVT were prospectively recruited in this cross-sectional study. Measures of functioning (outcomes) included self-reported questionnaires that assessed: 1) movement ability, measured with the Movement Ability Measure-Computer Adaptive Test version; 2) mobility, evaluated with the Computer Adaptive Test version of the Patient-Reported Outcomes Measurement Information System Pediatric Physical Functioning, Mobility domain; 3) functional disability, evaluated with the Functional Disability Inventory; and 4) physical activity levels, evaluated with the Godin Leisure-Time Exercise Questionnaire. The main predictor was PTS severity, which was assessed using the index for the Clinical Assessment of PTS in children. The association between PTS and outcomes was analyzed using linear models.

RESULTS

Eighty-seven patients (median age, 16 years; 25th-75th percentile, 15-18 years; 56% boys) were enrolled. Adjusted for age, sex, and underlying condition, increasing PTS severity was associated with lower current movement ability, a wider gap between current vs preferred movement ability, lower mobility, and slightly higher functional disability scores. There was a nonsignificant effect of PTS severity on moderate-strenuous physical activity.

CONCLUSION

In children, increased PTS severity is associated with lower movement ability and impaired mobility. Reducing the gap between the patients' current vs preferred movement ability is a relevant aspect of PTS management in children.

Developing and optimizing a machine learning predictive model for post-thrombotic syndrome in a longitudinal cohort of patients with proximal deep venous thrombosis

BACKGROUND

Post-thrombotic syndrome (PTS) is the most common chronic complication of deep venous thrombosis (DVT). Risk measurement and stratification of PTS are crucial for patients with DVT. This study aimed to develop predictive models of PTS using machine learning for patients with proximal DVT.

METHODS

Herein, hospital inpatients from a DVT registry electronic health record database were randomly divided into a derivation and a validation set, and four predictive models were constructed using logistic regression, simple decision tree, eXtreme Gradient Boosting (XGBoost), and random forest (RF) algorithms. The presence of PTS was defined according to the Villalta scale. The areas under the receiver operating characteristic curves, decision-curve analysis, and calibration curves were applied to evaluate the performance of these models. The Shapley Additive exPlanations analysis was performed to explain the predictive models.

RESULTS

Among the 300 patients, 126 developed a PTS at 6 months after DVT. The RF model exhibited the best performance among the four models, with an area under the receiver operating characteristic curves of 0.891. The RF model demonstrated that Villalta score at admission, age, body mass index, and pain on calf compression were significant predictors for PTS, with accurate prediction at the individual level. The Shapley Additive exPlanations analysis suggested a nonlinear correlation between age and PTS, with two peak ages of onset at 50 and 70 years.

CONCLUSIONS

The current predictive model identified significant predictors and accurately predicted PTS for patients with proximal DVT. Moreover, the model demonstrated a nonlinear correlation between age and PTS, which might be valuable in risk measurement and stratification of PTS in patients with proximal DVT.

Impact of deep vein thrombosis on adolescent athletes: Navigating an invisible disability

Background

Injury in adolescent athletes that threatens their sport participation can result in a sense of identity loss during critical years for identity development, creating the potential for significant mental health challenges. The specific effect of deep vein thrombosis (DVT) in this vulnerable population has not been characterized.

Purpose

To describe the impact of DVT diagnosis, treatment, and long-term complications on the mental well-being of athletes who sustained a DVT during adolescence and to identify strategies to improve the quality of care for these patients.

Methods

Using a qualitative study design, athletes with a history of DVT during adolescence and their parents were recruited to participate in semistructured interviews. Interviews were transcribed and analyzed using thematic analysis. Participants were recruited until reaching thematic saturation.

Results

In total, 19 participants (12 athletes, 7 parents) were recruited. Athletes were mainly males (67%), median age at time of DVT was 15 years (range, 12-18 years), and median age at study participation was 19 years (range, 16-34 years). Thematic analysis revealed four main themes: Theme 1: DVT posed a threat to sport participation; Theme 2: at a personal level, there were significant mental health challenges; Theme 3: at a societal level, DVT is an invisible disability; and Theme 4: physical, psychological, and transition support are important to improve the care of these patients.

Conclusion

Deep vein thrombosis threatens an athlete's participation in sport, resulting in a significant and complex impact on their mental well-being. Heightened awareness and a multidisciplinary approach are needed to help young athletes navigate the consequences of DVT.

T1 mapping is useful for staging deep venous thrombosis in the lower extremities

BACKGROUND

The discrimination of acute and chronic deep venous thrombosis (DVT) is of great importance. Quantitative imaging is an urgent requirement in reflecting intrinsic characteristics of thrombosis.

PURPOSE

To investigate the feasibility of T1 mapping in staging DVT in the lower extremities.

MATERIAL AND METHODS

A total of 57 patients with DVT in the lower extremities (26 men, 31 women; mean age = 53.3 years) underwent T1-weighted imaging and T1 mapping for obtaining T1 signal intensity (SI) and T1 time of thrombus. The relative SI (rSI) of DVT was obtained by calculating the ratio of thrombus SI to muscle SI. The Mann-Whitney U test was used to compare rSI and T1 time of DVT between acute group (patients with limb edema ≤ 2 weeks) and chronic group (patients with limb edema > 2 weeks). A receiver operator characteristic (ROC) curve was constructed for further evaluation.

RESULTS

DVT rSI was significantly higher in the acute group versus the chronic group (2.8 ± 1.2 vs. 1.4 ± 0.6; P<0.05). DVT T1 time was significantly lower in the acute group versus the chronic group (819.4 ± 223.7 ms vs. 1264.8 ± 270.7 ms; P<0.05). The area under the curve (AUC) was 0.93 for T1 time and 0.75 for rSI. When using 1015 ms as the cut-off, the sensitivity and specificity of T1 time were 91% (32/35) and 86% (19/22), respectively.

CONCLUSION

T1 mapping is a potential technique in discriminating acute from chronic DVT in the lower extremities and warrants further investigation.

Compression garments for the management of pediatric post-thrombotic syndrome: A prospective longitudinal study

BACKGROUND

Graduated compression garments (CG) are a standard form of management of post-thrombotic syndrome (PTS) in adults, but data in children are lacking.

OBJECTIVES

We aimed to study the attitudes toward CG and change in PTS severity score in children who were prescribed CG for PTS management.

METHODS

Children with PTS were enrolled in this longitudinal prospective study at the time of CG prescription. PTS severity was measured at baseline and follow-up using CAPTSure© ; attitude toward CG was registered at follow-up.

RESULTS

Forty-five patients were enrolled (median age 13 years, 25th-75th percentile 8-15 years; 53% male patients); 71% were prescribed socks and 29% sleeves; pressure was 15-20 mmHg in 84% of CG. Median baseline PTS CAPTSure© score was 31 points (25th-75th percentile 21-45 points). At follow-up, 49% of patients found CG helpful, 27% found CG not helpful, and 16% did not buy or wear the CG. Eight percent of enrolled patients did not return for study follow-up. Ninety-five percent of the children who found CG helpful wore them for ≥3 days/week. Hours of CG wear at the time of follow-up were associated with lower PTS scores at follow-up in a non-linear manner (e.g., wearing 12 vs. 0 h/day was associated with a 16-point reduction in PTS scores at follow-up, 95% CI -29 to -2 points).

CONCLUSION

Nearly half the patients who were prescribed CG found them helpful. We observed non-linear improvement in PTS severity with the use of low-pressure CG for 8-12 h/day and ≥3 days/week, providing guidance in their prescription.

Clinical characteristics and outcomes of combined thrombolysis and anticoagulation for pediatric and young adult lower extremity and inferior vena cava thrombosis

Effective treatment for acute, extensive, symptomatic lower extremity (LE) thrombosis involves thrombolysis in addition to anticoagulation. There is limited available data on the outcomes and safety of thrombolysis to help guide its use in pediatrics and young adults. A retrospective study of children and young adults (<21 years of age) that received catheter directed thrombolysis (CDT) for LE and inferior vena cava (IVC) thrombosis was performed over a 5-year span at a pediatric tertiary care center. A total of 29 patients were identified for inclusion in the study, 76% (n = 22) received overnight CDT while 24% (n = 7) received tissue plasminogen activator as a bolus dose during a single interventional procedure. The median age of the cohort was 15.8 years (range 0-19.1). All patients were treated with a course of therapeutic anticoagulation. The thromboses represented were extensive, with 93% (n = 27) being occlusive and affecting multiple venous segments. Thrombus resolution occurred in 35% (n = 10) of patients. Rivaroxaban use (p < 0.01) during the course of anticoagulation and estrogen-containing hormonal therapy (p = 0.01) use prior to diagnosis were associated with thrombus resolution, while Hispanic ethnicity (p = 0.06) had a trend toward thrombus persistence. There were one major and 3 minor bleeding events that occurred as complications of thrombolysis and no treatment related deaths. This study provides baseline information that can be used to help guide clinicians treating similar patients and suggests the need to develop an improved, uniform treatment approach for superior resolution rates.

Thrombosis is associated with worse survival in children with acute lymphoblastic leukemia: A report from CYP-C

There are conflicting data about whether the development of cancer-associated thrombo-embolism (TE) negatively impacts survival in children. The objective was to determine whether TE during treatment was associated with overall survival (OS) and event-free survival (EFS) in children with acute lymphoblastic leukemia (ALL). We performed a population-based retrospective cohort study using the Cancer in Young People-Canada registry. Children <15 years of age were diagnosed with de novo ALL (2000-2016). The primary exposure variable was radiologically-confirmed thrombo-embolism requiring medical intervention. Multivariable Cox regression models were used to determine the impact of thrombo-embolism on survival, where TE was time-dependent. We included 2006 children (median age: 4 years, 88.5% precursor B-cell ALL). Thrombo-embolism occurred in 113 patients (5.6%), at a median time of 107 days (interquartile range: 35-184 days) after ALL diagnosis. Among standard/low-risk patients, 41/1165 (3.5%) developed TE while among high/very high-risk patients, 72/841 (8.6%) developed TE. Patients with TE had a significantly worse OS (adjusted HR [aHR] of death: 2.61, 95% CI: 1.62-4.22, p < 0.001) and EFS (aHR of an event [death, relapse, second malignancy]: 2.03, 95% CI: 1.35-3.05, p = 0.001), compared with patients without TE. No statistically significant difference was seen in standard/low risk ALL for OS and EFS, but TE was associated with a significantly lower OS and EFS in children with high/very high-risk ALL (aHR of death: 2.90, 95% CI: 1.79-4.72, p < 0.001; aHR of an event: 2.02, 95% CI: 1.30-3.12, p = 0.002). Thus, TE led to a statistically significant reduction in OS and EFS in children with high risk/very high-risk leukemia.

Risk factors determining central venous access device-associated deep vein thrombosis resolution in children: a retrospective study

The risk factors associated with the probability of central venous access device (CVAD)-associated deep vein thrombosis (DVT) resolution have been hardly evaluated in children. Current guidelines suggest anticoagulation for a maximum of 3 months in patients with provoked DVT if the provoking factor is resolved. To know if the thrombus will resolve after anticoagulant therapy will help to choose whether to initiate and/or continue this treatment or not. We did a retrospective study of 85 pediatric patients (45 girls, 40 boys) with CVAD-associated DVT to examine the risk factors associated with lack of thrombus resolution in the first 6 months after diagnosis. Sixty-two children had their thrombosis resolved after a median of 50 days (p25-p75 25-97) since diagnosis. In multivariate analysis, variables significantly associated with no resolution were total occlusion (OR 12.50, 95% CI 2.99-52.14, p=.001), location in upper extremity, head, and neck veins (OR 17.70, 95% CI 1.64-191.43, p=.018); collateral circulation in the first 45 days after diagnosis (OR 33.55, 95% CI 2.42-464.71, p=.009); and having between 0 and 3 prothrombotic risk factors at diagnosis (OR 6.20, 95% CI 1.21-31.75, p=.029).Conclusion: CVAD-associated DVT resolution in children in the first 6 months since diagnosis was significantly lower if the thrombosis was occlusive, if it was located in the upper extremity, head, and neck veins; if collateral circulation was seen on ultrasound in the first 45 days; and/or when the patient showed less prothrombotic risk factors at diagnosis. What is Known: • The risk factors associated with central venous access device-associated deep vein thrombosis resolution have been hardly evaluated in children. • Current guidelines suggest anticoagulation for a maximum of 3 months in provoked vein thrombosis if the provoking factor is resolved. What is New: • Thrombus resolution was lower if it was occlusive, located in the upper extremity veins, if collateral circulation was seen, and with less prothrombotic risk factors at diagnosis. • To know if the thrombus will resolve after anticoagulation will help to choose whether to initiate and/or continue it or not.

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.

Pediatric May-Thurner Syndrome-Systematic review and individual patient data meta-analysis

BACKGROUND

The outcomes of deep vein thrombosis (DVT) in children with May-Thurner Syndrome (MTS) remain unclear.

OBJECTIVES

This systematic review and patient-level meta-analysis aims to describe the outcomes of children with MTS presenting with DVT.

METHODS

A systematic review of the published literature was performed. Data related to patients <18 years diagnosed with MTS and DVT was extracted. Risk of bias was assessed using the Murad criteria. Outcomes included vessel patency post-treatment, DVT recurrence, and post-thrombotic syndrome (PTS). Predictive and explanatory models were developed for these outcomes.

RESULTS

In total, 109 cases were identified (age range 4-17 years; 77 females) in 28 studies; 75% of patients had ≥1 additional risk factor for DVT. PTS was seen in 61% of patients, DVT recurrence in 38%, and complete vessel patency post-treatment in 65%. The models developed to predict and explain PTS performed poorly overall. Recurrent thrombosis (adjusted for age and patency) predicted PTS (odds ratio [OR] 3.36, 95% confidence interval [CI] 1.28-8.82). DVT management strategies (adjusted for age and DVT characteristics) predicted vessel patency (OR 2.10, 95% CI 1.43-3.08). Lack of complete vessel patency (adjusted for age and thrombophilia) predicted recurrent DVT (OR 2.70, 95% CI 1.09-6.67). Sensitivity analyses showed the same direction of effects for all outcomes.

CONCLUSIONS

PTS and DVT recurrence occur frequently in pediatric MTS. PTS prediction is complex and it was not possible to identify early predictors to guide clinical practice. Use of imaging-guided therapy and thrombus burden predicted venous patency, and lack of patency predicted DVT recurrence.

Diagnosis, Clinical Characteristics, and Treatment Modalities of Adolescent May-Thurner Syndrome-associated Deep Venous Thrombosis

May-Thurner syndrome (MTS) predisposes individuals to develop lower extremity deep venous thrombosis (DVT) because of compression of the left common iliac vein. Diagnosis of the anatomic obstruction is critical for effective therapy, as treatment by interventional radiology is often required in addition to anticoagulation to prevent thrombus progression and recurrence. The authors performed a retrospective review of adolescent patients who presented with MTS-associated DVT at a pediatric tertiary care center from 2009 to 2018 to assess for delays in MTS diagnosis after the presentation. Fourteen patients (median age 16.5 y, range, 13.8 to 17.9 y) were included, no DVTs were provoked by a central venous catheter. The median time from DVT to MTS diagnosis was 0.65 months (range, 0 to 21.5 mo). The initial imaging modalities used for DVT diagnosis were not able to diagnosis MTS. All patients were treated with anticoagulation and 13 underwent interventional therapy. Four patients had thrombus progression or recurrence, whereas 6 had complete thrombus resolution on follow-up imaging. Three patients who had a delayed MTS diagnosis had clinical worsening despite therapeutic anticoagulation requiring rehospitalization. Adolescent patients with "unprovoked" left lower extremity DVT should undergo appropriate imaging to diagnose MTS to allow for adequate medical and interventional therapy.

Patient Characteristics and Treatment Outcomes of Symptomatic Catheter-Related Arterial Thrombosis in Infants: A Retrospective Cohort Study

OBJECTIVE

To describe the clinical characteristics, outcomes, and adverse events of treatment for symptomatic infant catheter-related arterial thrombosis.

STUDY DESIGN

Single-center retrospective medical record review of 99 infants (age <365 days) with catheter-related arterial thrombosis, either following indwelling arterial catheter placement or cardiac catheterization, who were treated with anticoagulation over an 8-year span at a pediatric tertiary care center. Outcomes measured include thrombosis progression, bleeding events, and thrombus resolution following the treatment period.

RESULTS

Thromboses were secondary to indwelling arterial catheter placement in 51 (51.5%) and cardiac catheterization in 48 (48.5%). The median age at diagnosis of catheter-related arterial thrombosis was 52 days. All patients received therapeutic anticoagulation with either unfractionated heparin or low molecular weight heparin for a maximum of 28 days. Progression of catheter-related arterial thrombosis occurred in 8 (8.1%) patients. One (1%) major and 3 (3%) minor bleeding events occurred within the cohort. Complete thrombus resolution was observed in 60 (60.6%), partial resolution in 33 (33.3%), and no resolution in 6 (6.1%) following the treatment period. Factors associated with complete thrombus resolution included time from intervention to catheter-related arterial thrombosis diagnosis (median of 1 day vs 5 days in those who experienced thrombus resolution vs those who did not, P = .035), and iliac and/or femoral artery involvement (P = .015).

CONCLUSIONS

Our treatment approach to infant catheter-related arterial thrombosis is safe and effective. Limitations of the study are its retrospective nature with a limited number of patients from a single institution. Additional prospective studies are needed to determine the optimal treatment approach to catheter-related arterial thrombosis in infants.

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.

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.

Risk factors for venous thromboembolic events in pediatric surgical patients: Defining indications for prophylaxis

BACKGROUND

Venous thromboembolism (VTE) in pediatric surgical patients is a rare event. The risk factors for VTE in pediatric general surgery patients undergoing abdominopelvic procedures are unknown.

STUDY DESIGN

The American College of Surgeon's National Surgical Quality Improvement Program-Pediatric (NSQIP-P) database (2012-2015) was queried for patients with VTE after abdominopelvic general surgery procedures. Patient and operative variables were assessed to identify risk factors associated with VTE and develop a pediatric risk score.

RESULTS

From 2012-2015, 68 of 34,813 (0.20%) patients who underwent abdominopelvic general surgery procedures were diagnosed with VTE. On multivariate analysis, there was no increased risk of VTE based on concomitant malignancy, chemotherapy, inflammatory bowel disease, or laparoscopic surgical approach, while a higher rate of VTE was identified among female patients. The odds of experiencing VTE were increased on stepwise regression for patients older than 15 years and those with preexisting renal failure or a diagnosis of septic shock, patients with American Society of Anesthesia (ASA) classification ≥ 2, and for anesthesia time longer than 2 h. The combination of age > 15 years, ASA classification ≥ 2, anesthesia time > 2 h, renal failure, and septic shock was included in a model for predicting risk of VTE (AUC = 0.907, sensitivity 84.4%, specificity 88.2%).

CONCLUSION

VTE is rare in pediatric patients, but prediction modeling may help identify those patients at heightened risk. Additional studies are needed to validate the factors identified in this study in a risk assessment model as well as to assess the efficacy and cost-effectiveness of prophylaxis methods.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

Phase 3, single-arm, multicenter study of dabigatran etexilate for secondary prevention of venous thromboembolism in children: Rationale and design

BACKGROUND

Anticoagulant therapy for venous thromboembolism (VTE) in children is largely based on treatment recommendations for adults. However, differences in both physiology (ie, renal maturation and drug excretion) and developmental hemostasis must be considered when treating children, as such differences could affect dose appropriateness, safety and efficacy.

OBJECTIVES

To address these concerns, a study was designed to evaluate the safety of dabigatran etexilate in children requiring secondary thrombus prevention in whom an initial VTE was associated with an identified risk factor that persisted after the acute VTE treatment period. We report herein the rationale and design of the study.

PATIENTS/METHODS

This phase 3, open-label, single-arm, multicenter, multinational, prospective cohort study will be conducted in ≥100 children aged 0 to <18 years at ~100 specialist sites worldwide. Children will be treated with dabigatran etexilate for 12 months, or for a shorter duration if their identified VTE risk factor resolves, as per current American College of Chest Physicians recommendations. A nomogram will be used to determine starting doses for each patient.

RESULTS

The primary outcomes of the study will be VTE recurrence, bleeding events, overall mortality, and VTE-related mortality. Secondary outcomes will include occurrence of post-thrombotic syndrome, the pharmacokinetics of dabigatran, and the need for dose adjustments during treatment. Data on adverse events during the study will also be collected.

CONCLUSION

This study will evaluate the safety of dabigatran etexilate for the secondary prevention of VTE in children, in addition to providing further data to guide pediatric dosing with dabigatran.

Assessment of limb edema in pediatric post-thrombotic syndrome

BACKGROUND

Pediatric tools for diagnosis of post-thrombotic syndrome (PTS) include the assessment of limb edema as a symptom (patient/proxy-reported) and as a sign. However, it is unclear whether these two approaches refer to the same clinical aspect of PTS. This could result in overestimation of disease severity. We sought to evaluate the correlation among different techniques to assess limb edema as a sign and as a symptom in children who sustained upper extremity (UE) or lower extremity (LE) deep vein thrombosis (DVT) and were, therefore, at risk of PTS.

METHODS

Limb edema was cross-sectionally measured as a symptom (ie, patient- or proxy-reported) and as a sign (ie, clinician-assessed limb circumference difference, limb volume ratio, bioimpedance spectroscopy ratio (BIS), and durometry ratio) in 140 children at risk of PTS (n = 70 UE-DVT, n = 70 LE-DVT). Item-item correlations were estimated using Pearson or Spearman correlation coefficients, as appropriate, and separately for the UE and LE groups.

RESULTS

In the UE-DVT group, proxy-reported swelling correlated weakly to moderately with circumference difference and with volume ratio, but not with BIS ratio. In the LE-DVT group, proxy-reported swelling correlated moderately with thigh circumference difference and volume ratio, and patient-reported swelling correlated moderately with BIS ratio.

CONCLUSION

Our findings suggest that patient/proxy-reported and clinician-assessed limb edema measure slightly different aspects of PTS, justifying their inclusion in pediatric PTS tools. In addition, proxy-reported swelling was in closer agreement with clinician-assessed total limb size (ie, observed edema), and patient-reported swelling in the LE seemed to reflect limb fluid content (ie, perceived edema).

Can thrombophilia predict recurrent catheter-related deep vein thrombosis in children?

Thrombophilia was not predictive of recurrent catheter-related deep vein thrombosis in children. Young age at the time of catheter insertion and lack of administration of anticoagulation were predictive of recurrent events.

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.