Post-thrombotic syndrome in children: a systematic review of frequency of occurrence, validity of outcome measures, and prognostic factors

Thromboprophylaxis in Children: Navigating Uncharted Waters

The rising incidence of pediatric thrombosis, increasing nearly 10% annually over the past decade, underlines a need for effective preventive strategies, particularly in hospitalized children. This narrative review explores existing literature on venous thromboembolism prevention in pediatric patients to clarify current strategies in children undergoing general, orthopaedic, and Fontan surgeries, and with conditions such as acute lymphoblastic leukemia and gastrointestinal disease. While recent studies have provided some insights into potential preventive strategies, real evidence is lacking on the best practices for thromboprophylaxis in these patient groups. In the absence of substantial studies, clinicians must rely on individual assessments weighting thrombotic and bleeding risk to effectively and safely manage these "uncharted waters."

Incidence and risk factors for postthrombotic syndrome in neonates and children in a single-center cohort study

BACKGROUND

Postthrombotic syndrome (PTS) is a chronic condition following deep vein thrombosis (DVT) and is associated with pain, swelling, and restricted use of the affected limb. In pediatric age groups, its incidence and risk factors are not well-known.

METHODS

This observational cohort study of all consecutive children (≤18 years) with DVT treated at the Emma Children's Hospital Amsterdam between January 2001 and January 2021 was conducted to identify incidence and risk factors for PTS in neonates aged ≤2 months and children aged >2 months. PTS was diagnosed using the modified Villalta scale.

RESULTS

In total, 315 patients were included. The 20-year incidence of PTS was 20.0% in neonates and 40.0% in children. In neonates, involvement of ≥3 vessels (odds ratio [OR], 6.6; 95% CI, 1.6-26.4) and incomplete thrombus resolution (OR, 3.0; 95% CI, 1.1-8.0) were risk factors for PTS. In children, involvement of ≥3 vessels (OR, 6.2; 95% CI, 2.2-17.8), recurrent DVT (OR, 3.7; 95% CI, 1.3-10.3), and incomplete thrombus resolution (OR, 5.2; 95% CI, 1.6-17.0) were associated with PTS. Exercise ≥3 times/wk (OR, 0.4; 95% CI, 0.2-0.9), central venous catheter-related DVT (OR, 0.2; 95% CI, 0.1-0.5), and provoked DVT (OR, 0.4; 95% CI, 0.1-0.97) were protective factors for PTS.

CONCLUSION

This study demonstrated a high incidence of pediatric PTS. Additionally, risk factors for PTS differed between neonates and children. These findings provide a basis for better prevention and management of PTS that may differ between neonates and children.

Thrombosis in Children: A Retrospective Study from a Single-center Database

BACKGROUND/AIM

The incidence and characteristics of pediatric thrombotic events have become increasingly recognized, due to the enhanced utilization of advanced diagnostic techniques. Pediatric thrombosis remains less frequent than in adults, often manifesting in those with underlying congenital or acquired risk factors. This study aimed to establish epidemiological data on pediatric thrombotic events in Bihor County, Romania, highlighting the challenges of diagnosis in smaller medical centers and proposing a relevant diagnostic and treatment algorithm.

PATIENTS AND METHODS

This retrospective study, conducted over 22 years at the Emergency County Clinical Hospital Bihor, identified 39 pediatric patients diagnosed with thrombotic events using electronic medical records.

RESULTS

Most patients (82.1%) were diagnosed between 2013 and 2024, with a slight male predominance. The age distribution shows two peak clusters: newborns up to one year and adolescents. The majority of cases (53.8%) were venous thromboembolism, followed by arterial thromboembolism at 41%, while 5.1% involved both types. Cerebral thrombosis was the most common, followed by lower and upper limb events. Inherited thrombophilia factors were found in all patients tested, with antithrombin, protein S, and protein C deficiencies identified. Malignancy was the most frequently acquired risk factor, and PAI-1 4G/5G was the most common genetic variant detected among inherited factors.

CONCLUSION

This study highlights the significant rise in pediatric thromboembolism recognition over the past two decades; however, underdiagnosis remains an issue. Improved awareness among healthcare professionals is crucial, particularly for unprovoked thrombosis cases where a thorough thrombophilia panel and the involvement of a multidisciplinary team may be necessary.

Evidence-based summary of preventive care for central venous access device-related thrombosis in hospitalized children

PURPOSE

This study aims to summarize the latest and best evidence on central venous access device-related thrombosis (CRT) in hospitalized children, which provides theoretical support for standardizing the preventive care practice of CRT in hospitalized children.

METHODS

Relevant guidelines, systematic reviews and expert consensuses were reviewed through ten guideline websites, six professional association websites and seven databases. The literature evaluation was conducted, and the best evidence from qualified studies was extracted and summarized. Furthermore, the best evidence was summarized through expert consultation and localized for the preventive care practice of CRT in hospitalized children in China.

RESULTS

A total of 14 topics and 68 best evidence were collected, including personnel qualification and quality management, pediatric patient selection, risk assessment, central venous access device (CVAD) selection and use, tip position, catheter maintenance, basic prevention, drug prevention, imaging examination, health education, nursing records, follow-up, CVAD removal and others.

CONCLUSION

In this study, the best evidence based on evidence-based nursing was summarized, and expert consultation was adopted to localize the best evidence collected. It is of great significance to standardize the clinical practice of pediatric nurses and ensure the effectiveness of CRT preventive care for hospitalized children, thus guaranteeing the safety of hospitalized children with CVAD catheterization.

Incidence of acute Deep Vein Thrombosis in pediatric and adolescent orthopedic trauma hospitalized patients and effect of rivaroxaban treatment

OBJECTIVE

Deep vein thrombosis (DVT) provoked by orthopedic trauma is increasing in pediatric hospitalized patients. The purpose of our study is to identify the prevalence of acute DVT in pediatric and adolescent orthopedic trauma hospitalized patients and focus on evaluating the anticoagulation strategies and the clinical outcomes after a confirmed acute DVT.

METHODS

Patients (age ≤18 years) with a confirmed acute DVT admitted for orthopedic trauma between September 2017 and December 2023 were included. Patients were classified into the non-anticoagulation (NA), the in-hospital anticoagulation (IHA), and the in-and-out-of-hospital anticoagulation (IOHA) groups based on their anticoagulation regimen. Efficacy outcomes were the venous thromboembolism (VTE) recurrence within 3 months and change in thrombus burden by repeat imaging at 2 weeks after discharge compared with baseline. Safety outcomes were major bleeding (MB) and clinically relevant non-major bleeding (CRNMB) within 3 months.

RESULTS

Of the 11,206 pediatric and adolescent orthopedic trauma inpatients, 94(median age,16 [15, 18] years) were diagnosed with acute DVT, with an incidence of 0.84 %, of which 8(8.5 %) received NA, 41(43.6 %) received IHA, and 45(47.9 %) received IOHA. After the diagnosis of DVT, of patients who received anticoagulation, 97.9 % were treated with rivaroxaban as an oral anticoagulant, and 71.7 % received an LMWH course of ≥5 days before starting rivaroxaban therapy. With a median anticoagulation course of 22(8, 37.3) days, the duration in the IOHA was significantly longer than the IHA (37 days vs. 8 days, p = 0.000). No patients experienced recurrent VTE and MB at 3 months, and 1 received IOHA had a CRNMB event (0 % vs. 0 % vs. 2.2 %, p = 1.000). Thrombus resolution was significantly higher in patients who received anticoagulation therapy (IOHA 91.1 % vs. IHA 80.5 % vs. NA 37.5 %, P = 0.002), and thrombus-no relevant change was significantly lower in patients who received the IOHA strategy compared with the other groups (4.4 % vs. 19.5 % vs. 62.5 %, P = 0.000).

CONCLUSIONS

A rivaroxaban-predominant IOHA strategy significantly reduced the thrombotic burden without increasing the risk of bleeding for the treatment of DVT in adolescents with orthopedic trauma. Duration of anticoagulation therapy <6 weeks appears appropriate for adolescent orthopedic trauma-related DVT.

Percutaneous Transluminal Angioplasty Alleviate Pediatric Postthrombotic Syndrome: A Case Report and Literature Review

PURPOSE

Postthrombotic syndrome (PTS) is one of the long-term sequelae of deep vein thrombosis (DVT), and effective symptom management in pediatric PTS remains a challenge, with interventional therapy rarely explored in this population. We present a successful case of interventional treatment pediatric PTS, resulting in a remarkable amelioration of her symptoms.

CASE REPORT

This case features a 6-year-old girl diagnosed with hyperinsulinemia, leading to a hypoglycemic coma. Following a mini-pancreatic partial pancreatectomy, she required further intensive care in the pediatric intensive care unit. It was during this period that left lower extremity DVT was identified, prompting warfarin anticoagulation therapy. During the anticoagulation period, she had several bleeding events and was switched to anticoagulation with low molecular heparin. One month later, the left common iliac vein and external iliac vein was found to be completely occluded. Over time, she experienced a gradual onset of lower limb swelling and pain, which, after 6 months, was accompanied by perineal edema and venous claudication. As a result, she underwent successful percutaneous transluminal angioplasty. In addition, the anticoagulation regimen was adjusted to rivaroxaban. At the 8-month follow-up, we observed significantly improvement in her postoperative lower extremity swelling and symptoms related to venous occlusion had completely disappeared. Moreover, vascular imaging confirmed improvement in stenosis and uninterrupted blood flow.

CONCLUSIONS

In our review of pediatric PTS studies, we observed limited options to alleviate symptoms, and interventional treatments have not been reported. Our case study, demonstrating the safe and effective use of percutaneous transluminal angioplasty, helps to illuminate this area and alleviate pediatric PTS symptoms.

CLINICAL IMPACT

This case validates the efficacy and safety of using percutaneous transluminal angioplasty (PTA) for the treatment of postthrombotic syndrome (PTS) in pediatric patients. This interventional approach offers significant symptomatic relief and improves quality of life, especially in cases where traditional anticoagulation therapies fail or lead to complications. The successful case presented emphasizes the necessity of considering endovascular interventions for children with moderate to severe PTS, particularly when conservative management is ineffective. This research underscores the potential for PTA to be adopted in clinical practice, offering a promising new approach for managing pediatric PTS.

Interventional Treatment of Pediatric Venous Thromboembolic Disease

This review explores the clinical presentation of lower extremity DVT and pulmonary embolism (PE), treatment strategies, and outcomes for venous thromboembolism (VTE) in the pediatric population. Traditional therapy for pediatric VTE was anticoagulation alone with thrombolysis and surgery reserved only in life or limb-threatening cases. Catheter-directed thrombolysis (CDT), pharmacomechanical thrombectomy (PMT) and mechanical thrombectomy (MT) have emerged as effective and safe treatment options for VTE management. Although most data are from adult studies, early pediatric studies suggest that these interventional procedures can be effective in children. The significant clinical impact of post-thrombotic syndrome (PTS) is also discussed, as PTS can lead to lifelong physical symptoms and psychosocial damage.

Sequelae and post-thrombotic syndrome after venous thromboembolism in acute lymphoblastic leukemia survivors treated on the NOPHO ALL2008 protocol

The treatment of acute lymphoblastic leukemia (ALL) is frequently complicated by toxicity, including venous thromboembolism (VTE) affecting roughly 8% of patients. VTE can lead to post-thrombotic syndrome (PTS), a group of signs and symptoms developed as a complication to deep venous thrombosis (DVT), imposing risk of permanent disability and reduced quality of life (QoL). PTS prevalence ranges from 0% to 70%, reflecting very heterogenous cohorts and assessment tools. We aimed to estimate sequelae, including PTS and QoL in children and adults (<45 years old) who had a DVT during ALL treatment. PTS and QoL scores were obtained through use of Villalta and Modified Villalta Scale, PedsQL, and Short Form-36 questionnaires. The cohort comprised 20 children (<18 years) and seven adults (median age: 12.9 years, range: 2-44 years) at the time of DVT diagnosis. In total, 25 ALL survivors underwent PTS examination. The examination took place when survivors were 7-48 years (median age: 20.3 years, median follow-up time 6.8 years). QoL was assessed correlating cases with three matching ALL survivors without VTE. Two adults (15.4%) showed mild or moderate PTS. Eight children (66.7%) were diagnosed with mild PTS, while three cases had collaterals as sole symptoms. Pain or symptoms affecting daily life were reported by 16%. No difference in QoL was found (p = .9). This study underscores the need for comprehensive population-based investigations with validation of PTS instruments in ALL survivors.

Venous Compressive Disorders

Venous compressive disorders are a heterogenous group of vascular syndromes characterized by extrinsic venous compression that can lead to complications of venous hypertension or venous thrombosis. Endovascular damage secondary to deep venous thrombosis (DVT) can result in post-thrombotic syndrome (PTS), a potentially debilitating condition that can be associated with significant morbidity in the pediatric population. Here we discuss 4 venous compressive disorders: iliac vein compression (May-Thurner syndrome [MTS]); subclavian vein compression at the venous thoracic inlet (Paget-Schroetter syndrome); left renal vein compression (nutcracker syndrome); and popliteal vein compression (popliteal entrapment syndrome) with a focus on clinical evaluation and diagnostic methods. Where endovascular therapy is appropriate, specific procedural considerations including procedure indications, equipment, procedural steps, technical challenges, complications, clinical follow-up and expected outcomes are discussed.

Anticoagulation of pediatric patients with venous thromboembolism in 2023

Venous thromboembolism (VTE) is a rare and heterozygous disease in children. Management of VTE in children is complicated by age-related differences in epidemiology, recurrent VTE and bleeding risk, hemostatic proteins and pharmacokinetics of anticoagulants. Recently, the choice of anticoagulation has expanded to oral factor IIa and Xa inhibitors, which have been authorized for children for treatment of acute VTE and extended secondary prevention. These drugs have several properties that make them extremely suitable for use in children, including oral administration, antithrombin independence, less interactions with food and drugs and no need for monitoring. Unfortunately, the phase 3 studies had many exclusion criteria, and only a few term neonates and infants were included in these studies. Additional real-world data is needed to make evidence-based recommendations in these age and patient groups, as well.

Percutaneous treatment of symptomatic deep vein thrombosis in adolescents using large-bore thrombectomy systems

BACKGROUND

While large-bore mechanical thrombectomy provides effective venous thrombus removal, often with avoidance of thrombolytics, literature surrounding the application of these devices in pediatric patients is sparse.

OBJECTIVE

To report technical success and outcomes following large-bore thrombectomy systems in adolescent patients with deep venous thrombosis.

MATERIALS AND METHODS

A retrospective review identified all patients less than 18 years of age undergoing mechanical venous thrombectomy at a single institution between 2018 and 2022. No patients were excluded. Technical success was defined as extraction of thrombus sufficient to restore unimpeded flow in affected segments. Clinical success was defined as resolution of presenting symptoms.

RESULTS

Nine consecutive patients (6 females, 3 males; age range 15-17 years) underwent 10 thrombectomy procedures using ClotTriever (n=6; 60%), FlowTriever (n=2; 20%), or both (n=2; 20%). Chronicity of thrombus was categorized as acute (<2 weeks) in 6 (60%), subacute (2-6 weeks) in 1 (10%), and chronic (>6 weeks) in 3 (30%). Distribution of thrombus was lower extremity and/or inferior vena cava (IVC) in 9 (90%) and unilateral axillo-subclavian in 1 (10%). Technical success was achieved in 9 interventions (90%). Clinical success was achieved in 8 patients (88.9%). No patients received thrombolytics. There were no intraprocedural adverse events (AE). Minor complications (Society of Interventional Radiology mild adverse events) were observed in a delayed fashion following 2 interventions (20%).

CONCLUSIONS

This preliminary experience demonstrated high rates of technical and clinical success with large-bore deep venous thrombectomy in adolescent patients across a range of thrombus chronicity and locations.

Evaluation of venous thromboembolism risk factors reveals subtype heterogenicity in children with central venous catheters: a multicenter study from the Children's Hospital Acquired Thrombosis consortium

BACKGROUND

Acutely ill and medically complex children frequently rely on central venous catheters (CVCs) to provide life-sustaining treatment. Unfortunately, catheter-related thrombosis (CRT) is a serious and common complication. Little is known why some with a CVC develop CRT and others develop venous thromboembolism unrelated to the CVC (non-CRT).

OBJECTIVES

The aim of this study was to identify factors associated with CRT in children with hospital-acquired venous thromboembolism (HA-VTE).

METHODS

This case-case study included participants in the Children's Hospital Acquired Thrombosis Registry with HA-VTE and CVC aged 0 to 21 years from 8 US children's hospitals. Participants were excluded if they developed HA-VTE prior to CVC insertion or if the CVC insertion date was unknown. Logistic regression models were used to assess associations between clinical factors and CRT status.

RESULTS

There were 1144 participants with HA-VTE who had a CVC. CRT developed in 833 participants, and 311 developed non-CRT. Multivariable analysis showed increased odds of CRT (compared with non-CRT) in participants with peripherally inserted central catheters (odds ratio [OR], 3.80; 95% CI, 2.04-7.10; p < .001), CVCs inserted in the femoral vein (OR, 4.45; 95% CI, 1.70-11.65; p = .002), multiple CVCs (OR, 1.42; 95% CI, 1.18-1.71; p < .001), and CVC malfunction (OR, 3.30; 95% CI, 1.80-6.03; p < .001).

CONCLUSION

The findings of this study provide new insights on risk factor differences between CRT and non-CRT. Prevention efforts should be directed at modifying the type of CVC, insertion location, and/or number of CVCs placed, if possible, to decrease the incidence of CRT.

Development and validation of knowledge, attitude and practice questionnaire for pediatric nurses to prevent central venous device-related thrombosis in hospitalized children

AIM

This study aimed to develop and validate a scientific and standardized knowledge, attitude and practice questionnaire of pediatric nurses' preventive care for central venous device-related thrombosis among hospitalized children.

BACKGROUND

Pediatric nurses play a significant role in the prevention of central venous device-related thrombosis for hospialized children. However, the status of pediatric nurses' knowledge, attitude and practice of central venous device-related thrombosis prevention has not been revealed due to the lack of assessment tools.

METHODS

This questionnaire was framed by the theory of knowledge, attitude and practice. The item pool was compiled through a literature review and a preliminary questionnaire was formed based on expert consultation. A total of 457 pediatric nurses from 10 tertiary class A general hospitals and specialized pediatric hospitals in China were selected for pre-survey. Item analysis, reliability and validity test were conducted to refine and evaluate the items to form a formal questionnaire.

RESULTS

A total of 54 items were proposed in three dimensions of knowledge, attitude and practice. In the exploratory factor analysis, five, three and three common factors were extracted for each dimension, accounting for 60.552%, 89.829% and 84.258% of the total variance, respectively. The content validity index of the three dimensions ranged from 0.968 to 1.000 at the scale level and from 0.833 to 1.000 at the item level. The Cronbach's α coefficients for the total questionnaire and each dimension were between 0.926 and 0.973. The retest reliability for the total questionnaire and each dimension was between 0.688 and 0.898.

CONCLUSION

The proposed questionnaire has good reliability and validity and it can be applied to evaluate pediatric nurses' knowledge, attitude and practice in preventing central venous device-related thrombosis for hospitalized children.

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.

High Rates of Pediatric Venous Thromboembolism After Elective Laparoscopic Splenectomy Suggest Need for Perioperative Prophylaxis

INTRODUCTION

In adult populations, postoperative venous thromboembolism (VTE) is a reported complication of up to 8% of elective laparoscopic splenectomy (LS) cases. VTE is a rare event in the pediatric population, affecting less than 1% of all pediatric surgical patients. We hypothesized that pediatric patients are at a higher risk of postoperative VTE after undergoing elective LS relative to other laparoscopic procedures and may warrant prophylactic treatment.

MATERIALS AND METHODS

We queried the American College of Surgeons National Surgical Quality Improvement Program-Pediatric (NSQIP-P) database from 2012 to 2020. Patients were identified using the Current Procedural Terminology code 38120 and only elective cases were analyzed.

RESULTS

The incidence of VTE in all pediatric patients undergoing surgery in the American College of Surgeons NSQIP-P database was 0.13%. The incidence of VTE in pediatric patients undergoing elective laparoscopic abdominopelvic procedures was 0.17%. There were seven total cases of VTE (0.41%) in pediatric patients undergoing elective LS, more than twice the rate of the general population (P = 0.001). Eighty percent of pediatric patients undergoing elective LS had an underlying hematological disorder.

CONCLUSIONS

By analyzing the NSQIP-P database, we evaluated the largest cohort of pediatric patients undergoing elective LS to date. We identified a higher incidence of VTE following this procedure relative to the rate of VTE in the overall population in the NSQIP-P database, as well as those undergoing elective laparoscopic abdominopelvic operations. The relatively higher incidence of VTE after elective LS is likely due to the presence of underlying hematological conditions. Given the low incidence of complications associated with pharmacologic VTE prophylaxis, the results of this study suggest that further research is warranted to establish the efficacy of perioperative pharmacological VTE prophylaxis in pediatric patients undergoing elective LS.

The Incidence of Thromboembolic Events During Hospitalizations Following Surgical Resection of Lower Extremity Sarcomas in Children: Utilizing the Pediatric Health Information System Database

BACKGROUND

Venous thromboembolism (VTE) is a frequent occurrence during treatment for adults with sarcoma. The incidence and underlying risk factors of postsurgical VTE in children and adolescents undergoing resection of sarcoma are unknown.

METHODS

Using International Classification of Disease revision-9 diagnostic and procedure codes, the Pediatric Health Information System database was queried for patients aged 18 years and younger, discharged from 2004 to 2015 with a diagnosis of lower extremity malignant neoplasm who had a tumor resection or amputation performed during the encounter. Malignant neoplasms of the pelvic bones and soft tissues were categorized as "pelvis tumors", whereas malignant neoplasms of bone and soft tissues of the lower limbs were categorized as "lower limb tumors". Hospitalizations were evaluated for the occurrence of VTE. Demographic characteristics (age at admission, sex, race, and race/ethnicity) and incidence of VTE were reported.

RESULTS

There were 2400 patients identified. Of these, 19 experienced VTE (0.79%) during their surgical hospitalization encounter. By anatomic group, the rate of VTE was 1.4% (CI: 0.5%-3.2%) for tumors in the pelvis and 0.6% (CI: 0.3%-1.0%) in lower limb tumors. Categorizing by age, the incidence of VTE was 1.2% in patients aged zero to 5, 0.3% in patients 6 to 13, and 1.2% in patients 14 to 18 years old. (Table 1). The extremely low rate of VTE occurrence precluded further analysis of risk factors.

CONCLUSIONS

In this analysis, postsurgical VTE during hospitalization after pelvic and lower extremity sarcoma resection was an uncommon event in children and adolescents. There seemed to be an increased incidence of postsurgical VTE in pelvic tumors when compared with lower limb tumors, however, the rarity of all events precluded formal statistical analysis. A more robust data set would be required to determine if there are subsets of children and adolescents with sarcoma at higher risk of VTE that could benefit from thromboprophylaxis in the postoperative setting.

LEVEL OF EVIDENCE

Level II.

Timing of Central Venous Line Insertion During Induction in Children With Acute Lymphoblastic Leukemia

PURPOSE

Central venous lines (CVL) in children with acute lymphoblastic leukemia (ALL) provide comfortable administration of intensive chemotherapy and blood sampling. The optimal time for the insertion of CVL in patients with ALL during induction therapy is controversial. This study aimed to investigate the frequency of CVL-related complications in children with ALL concerning the time of CVL insertion.

PATIENTS AND METHODS

We reviewed the records of 52 pediatric ALL patients with CVL. CVL placement before or on treatment day 15 was defined as "early insertion", and after treatment day 15 was defined as "late insertion". Demographics, preoperative blood counts, type of central line, time of CVL placement, CVL-related complications, and blood counts during complications were all noted. All the data were collected from those with the first catheter use.

RESULTS

CVL was placed ≤15 days in 26 patients (50%) and after 15 days in 26 patients (50%). Regarding the infection rates, no statistical difference was found between early and late CVL-inserted groups ( P =n.s.). Five patients developed thrombosis, and risk was found to be similar between early and late CVL-inserted groups ( P =n.s.). Catheter-related mechanical complications were recorded in 7 patients (3 in early and 4 in late CVL-inserted group, ( P =n.s.).

CONCLUSION

The present study showed no relation between the timing of CVL placement during induction therapy and the occurrence of infection and thrombosis. Our results suggest that CVL can be placed safely at the time of diagnosis or early induction treatment to provide a comfortable administration of chemotherapy and decrease painful blood samplings.

Risk of venous thromboembolism in pediatric hospitalized patients undergoing noncardiac surgery: A report from the Children's Hospital-Acquired Thrombosis consortium

Background

Surgery is a known risk factor for hospital-acquired venous thromboembolism (HA-VTE) in children.

Objectives

To assess whether the odds of HA-VTE differs across six anatomic sites of noncardiac surgery and to identify risk factors for HA-VTE in these children.

Methods

This was a multicenter, case-control study. Anatomic sites of surgery and risk factors for HA-VTE were collected on hospitalized pediatric patients who had undergone a single noncardiac surgery and developed HA-VTE (cases), and those who did not develop HA-VTE (controls), via the Children's Hospital-Acquired Thrombosis (CHAT) Registry. Logistic regression estimated the odds ratio (OR) and 95% confidence intervals (CIs) between six anatomic sites of surgery and 16 putative HA-VTE risk factors. Variables with a p value of 0.10 or less in unadjusted analyses were included in adjusted models for further evaluation. The final model used backward selection, with a significance level of 0.05.

Results

From January 2012 to March 2020, 163 cases (median age, 5.7 years; interquartile range [IQR], 0.3-14.2) and 208 controls (median age of 7.5 years; IQR, 3.7-12.9) met our criteria. There was no statistically significant increased odds of VTE among the types of noncardiac surgery. In the final adjusted model, central venous catheter (CVC; OR, 14.69; 95% CI, 7.06-30.55), intensive care unit (ICU) stay (OR, 5.31; 95% CI, 2.53-11.16), and hospitalization in the month preceding surgery (OR, 2.75; 95% CI, 1.24-6.13) were each independently significant risk factors for HA-VTE.

Conclusion

In children undergoing noncardiac surgery, placement of CVCs, admission/transfer to the ICU, or hospitalization in the month prior to surgery were positively associated with HA-VTE.

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.

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.

Prophylaxis of Venous Thromboembolism in Children: A Systematic Review

Venous thromboembolism (VTE) in children is a rare but serious event. Current guidance on pharmacological thromboprophylaxis in children is mostly based on adult studies and expert opinions. The aim of this systematic review was to examine under which conditions children (age ≤ 18 years) would benefit from pharmacological thromboprophylaxis with low molecular weight heparin or unfractionated heparin. Eligible studies included children, who did not receive pharmacological thromboprophylaxis as comparator, and VTE events were radiologically verified. MEDLINE and Embase were searched up to October 3, 2021. Ten studies were included presenting data for 976 children receiving pharmacological thromboprophylaxis. We divided the studies into three categories based on the population studied: children in the intensive care unit (n = 2), children with fractures and/or undergoing surgery (n = 5), and children with systemic disease (n = 3). A lower incidence of VTE was found when pharmacological thromboprophylaxis was used compared with no prophylaxis in children in intensive care unit with central venous catheter and mechanical ventilation (7/27 vs. 13/24), children in the intensive care unit admitted after trauma with a very high risk of VTE based on several risk factors (0/21 vs. 13/96), and children with acute lymphoblastic leukemia treated with L-asparaginase concomitant with steroid and presence of central venous catheter (0/82 vs. 8/121). Pharmacological thromboprophylaxis was not associated with an increased bleeding risk. In conclusion, pharmacological thromboprophylaxis in children is sparsely investigated. Only children with several risk factors for VTE are likely to benefit from pharmacological thromboprophylaxis.

Successful Secondary Endovascular Intervention in Pediatric Patients with Venous Thromboembolic Events

BACKGROUND

 In the past, pediatric patients with venous thromboembolic events (VTE) were treated with low-molecular-weight heparin (LMWH) which was successful in around 70% of the cases. However, anticoagulation alone might not restore patency in all patients, and advanced therapeutic options to prevent postthrombotic syndrome are needed. During recent years, endovascular interventions have become a treatment option for pediatric patients with persistent thrombotic occlusion, not only in life- or limb-threatening VTE.

METHODS

 We evaluated 12 consecutive patients (11-17 years) with newly diagnosed VTE being treated at our department during the last 4 years (2017-2020). In case follow-up examination showed persistent venoocclusion under anticoagulation, patients received secondary interventional therapy like recanalization, percutaneous transluminal angioplasty with or without catheter-directed thrombolysis, and stenting. Patients with no clinical signs of venoocclusion or regredient thrombosis in imaging examination received anticoagulation alone.

RESULTS

 Six of 12 (50%) patients underwent catheter intervention. Median time from diagnosis to intervention was 4 months (0-12 months). Reintervention was necessary in one (8%) case and complete recanalization failed in one (8%) case. There were no major bleeding events or other major postinterventional complications, no acute or late local recurrence, and all patients reported clinical improvement after the procedure.

CONCLUSION

 If endovascular intervention is used in teenage patients with persistent symptomatic VTE, reduction of postthrombotic symptoms is possible, even if intervention is performed secondary to failure of anticoagulation. Multidisciplinary treatment decisions can be based on the clinical course and follow-up imaging.

Thrombosis Complications in Pediatric Acute Lymphoblastic Leukemia: Risk Factors, Management, and Prevention: Is There Any Role for Pharmacologic Prophylaxis?

Pediatric acute lymphoblastic leukemia (ALL) has achieved close to 90% cure rates through extensive collaborative and integrative molecular research, clinical studies, and advances in supportive care. Despite this high achievement, venous thromboembolic complications (VTE) remain one of the most common and potentially preventable therapy-associated adverse events in ALL. The majority of thromboses events involve the upper central venous system which is related to the use and location of central venous catheters (CVC). The reported rates of symptomatic and asymptomatic CVC-related VTE range from 2.6 to 36.7% and 5.9 to 43%, respectively. Thrombosis can negatively impact not only disease-free survival [e.g., therapy delays and/or interruption, omission of chemotherapy agents (e.g., asparaginase therapy)] but also can result in long-term adverse effects that can impair the quality of life of ALL survivors (e.g., post-thrombotic syndrome, central nervous system (CNS)-thrombosis related complications: seizures, neurocognitive deficits). In this review, will discuss thrombosis pathophysiology in pediatric ALL, risk factors, treatment, and prevention strategies. In addition, the recently published clinical efficacy and safety of direct oral anticoagulants (DOACs) use in thrombosis treatment, and their potential role in primary/secondary thrombosis prevention in pediatric patients with ALL will be discussed. Future clinical trials involving the use of these novel oral anticoagulants should be studied in ALL not only for primary thrombosis prevention but also in the treatment of thrombosis and its secondary prevention. These future research findings could potentially extrapolate to VTE prevention strategies in other pediatric cancer diagnoses and children considered at high risk for VTE.

Systemic Catheter-Related Venous Thromboembolism in Children: Data From the Italian Registry of Pediatric Thrombosis

BACKGROUND

Central venous catheters (CVCs) represent one of the main risk factors for venous thrombotic events (VTEs) in children.

METHODS

We studied the Italian Registry of Pediatric Thrombosis (RITI) with regard to systemic radiologically confirmed CVC-related VTEs (CVC-VTEs) occurred during 6.5 years in children aged 29 days to 18 years.

RESULTS

A total of 78 CVC-VTEs were included, which occurred in 76 patients (40/76, 53% males). CVC-VTEs comprised 67 non-cardiac VTEs (86%) and 11 intracardiac thrombotic events (ICTEs) (14%); the median age at onset was 19 and 17 months, respectively. The most frequent reason for CVC insertion was supportive therapy. The catheters were placed percutaneously in 85% of cases (56/66) and surgically in the remaining 15% (10/66). Peripherally inserted central catheters (PICCs) were used in 47% (31/66) cases, partially implanted catheters in 42% (28/66), non-implantable catheters in 7% (5/66), and totally implanted catheters (Port) in 2% (1/66). CVC-VTEs were symptomatic in 77% of cases (60/78), while in the remaining 23%, they were incidentally detected on the imaging performed for the underlying condition. The median time between CVC insertion and the onset of symptoms was 10 days in non-cardiac VTEs and 39 days in ICTEs. Doppler ultrasound was the diagnostic technique most frequently used. The venous compartment most frequently affected was the veins of the lower extremities (52%, 43/73). Anti-thrombotic treatment was administered in 96% of CVC-VTEs (75/78). About 2.6% (2/76) of patients experienced a second thrombotic event. At discharge, post-thrombotic syndrome was reported in 13.5% (5/37) events with available data, CVC replacement in 10.8% (4/47), and ischemic necrosis with toe finger amputation in 2.7% (1/37). Three patients died due to an underlying condition; no CVC-VTE-related deaths were reported.

CONCLUSIONS

We have carried out a registry-based study on CVC-VTEs in the children in Italy, providing the data that may help improve the detection and management of this CVC-related complication.

Venous Thromboembolism in Premature Neonates

While the incidence of venous thromboembolism (VTE) is lower among children than adults, the newborn period is one of two bimodal peaks (along with adolescence) in VTE incidence in the pediatric population. Most VTE cases in neonates occur among critically ill neonates being managed in the neonatal intensive care unit, and most of these children are born premature. For this reason, the presentation, diagnosis, management, and outcomes of VTE among children born premature deserve special emphasis by pediatric hematologists, neonatologists, pharmacists, and other pediatric health care providers, as well as by the scientific community, and are described in this review.

Thrombolysis with Systemic Recombinant Tissue Plasminogen Activator in Children: A Multicenter Retrospective Study

Objective

This study aimed to evaluate systemic thrombolysis experiences with recombinant tissue plasminogen activator (rtPA).

Materials and Methods

Retrospective data were collected from 13 Turkish pediatric hematology centers. The dose and duration of rtPA treatment, concomitant anticoagulant treatment, complete clot resolution (CCR), partial clot resolution (PCR), and bleeding complications were evaluated. Low-dose (LD) rtPA treatment was defined as 0.01-0.06 mg/kg/h and high-dose (HD) rtPA as 0.1-0.5 mg/kg/h.

Results

Between 2005 and 2019, 55 thrombotic episodes of 54 pediatric patients with a median age of 5 years (range: 1 day to 17.75 years) were evaluated. These patients had intracardiac thrombosis (n=16), deep vein thrombosis (DVT) (n=15), non-stroke arterial thrombosis (n=14), pulmonary thromboembolism (PE) (n=6), and stroke (n=4). The duration from thrombus detection to rtPA initiation was a median of 12 h (range: 2-504 h) and it was significantly longer in cases of DVT and PE compared to stroke, non-stroke arterial thrombosis, and intracardiac thrombosis (p=0.024). In 63.6% of the episodes, heparin was initiated before rtPA treatment. LD and HD rtPA were administered in 22 and 33 of the episodes, respectively. Concomitant anticoagulation was used in 90% and 36% of the episodes with LD and HD rtPA, respectively (p=0.0001). Median total duration of LD and HD rtPA infusions was 30 h (range: 2-120 h) and 18 h (2-120 h), respectively (p=0.044). Non-fatal major and minor bleeding rates were 12.5% and 16.7% for LD and 3.2% and 25.8% for HD rtPA, respectively. At the end of the rtPA infusions, CCR and PCR were achieved in 32.7% and 49.0% of the episodes, respectively. The most successful site for thrombolysis was intracardiac thrombosis. HD versus LD rtPA administration was not correlated with CCR/PCR or bleeding (p>0.05).

Conclusion

Systemic thrombolytic therapy may save lives and organs effectively if it is used at the right indications and the right times in children with high-risk thrombosis by experienced hematologists with close monitoring of recanalization and bleeding.

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.

Endothelial dysfunction and thromboembolism in children, adolescents, and young adults with acute lymphoblastic leukemia

Endothelial dysfunction has not previously been investigated as a thrombogenic risk factor among patients with acute lymphoblastic leukemia (ALL), known to be at high risk of thromboembolism. We retrospectively explored the association between three circulating biomarkers of endothelial dysfunction (thrombomodulin, syndecan-1, VEGFR-1) measured in prospectively collected blood samples and risk of thromboembolism in 55 cases and 165 time-matched controls, treated according to the NOPHO ALL2008 protocol. In age-, sex-, and risk group-adjusted analysis, increasing levels of thrombomodulin and VEGFR-1 were independently associated with increased odds of developing thromboembolism (OR 1.37 per 1 ng/mL [95% CI 1.20‒1.56, P < 0.0001] and OR 1.21 per 100 pg/mL [95% CI 1.02‒1.21, P = 0.005], respectively). These associations remained significant when including only samples drawn >30 days before thromboembolic diagnosis. Thrombomodulin levels were on average 3.2 ng/mL (95% CI 2.6-8.2 ng/mL) higher in samples with measurable asparaginase activity (P < 0.0001). Among single nucleotide variants located in or neighboring coding genes for the three biomarkers, none were significantly associated with odds of thromboembolism. If results are validated in another cohort, thrombomodulin and VEGFR-1 could serve as predictive biomarkers, identifying patients in need of preemptive antithrombotic prophylaxis.

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.

Plasma fibrinolysis, inflammatory markers, and postthrombotic syndrome: preliminary findings from the Kids-DOTT Biobank

Plasma levels of markers of coagulation and inflammation have been identified as prognostic factors for adult postthrombotic syndrome (PTS). We aimed to determine whether plasma fibrinolytic capacity and cytokine levels during the first 3 months after provoked deep venous thrombosis (DVT) are associated with risk of PTS in young patients. We analyzed plasma biospecimens (6 weeks and 3 months after provoked DVT) and clinical data from a National Heart, Lung, and Blood Institute-sponsored multinational trial of anticoagulation for provoked venous thromboembolism in patients younger than age 21 years (Kids-DOTT). Patients with a provoked extremity DVT who had plasma samples available at both 6-week and 3-month post-DVT time points and PTS assessment at 1 year were included. We measured plasma fibrinolytic capacity using the Clot Formation and Lysis (CloFAL) assay and plasma cytokine levels by multiplex immunoassay. Logistic regression analyses evaluated prognostic associations with PTS. Seventy-nine patients were included (median age, 12.8 years; range, 0.04-20.8 years). PTS developed in 34%. Complete veno-occlusion at 6 weeks after diagnosis of DVT (odds ratio [OR], 3.12; 95% confidence interval [CI], 0.81-11.94; P = .097), low fibrinolytic capacity in plasma at 3 months post-DVT (OR, 2.71; 95% CI, 0.92-7.97; P = .07), and elevated serum amyloid A at 3 months post-DVT (OR, 2.85; 95% CI, 0.98-8.34; P = .055) were identified as putative prognostic factors for development of PTS. In multivariable logistic regression analysis, these factors did not retain a statistically significant independent association with PTS, but these preliminary results warrant further investigation in an independent data set to definitively evaluate these findings and identify additional potential prognostic factors for the development of PTS after a provoked DVT in young patients.

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.

Efficacy and Safety of Non-Vitamin K Antagonist Oral Anticoagulants in Pediatric Venous Thromboembolism Treatment and Thromboprophylaxis: A Systematic Review of the Literature

Venous thromboembolism (VTE) in children can lead to significant morbidity and mortality. Traditionally, treatment for thrombotic events in pediatric patients has been limited mainly to unfractionated heparin, low-molecular-weight heparin (LMWH), or vitamin K antagonists. Since the first non-vitamin K antagonist oral anticoagulant (NOAC) was approved for adult use, these agents have gained popularity for a variety of indications. This is largely due to their ease of administration, favorable pharmacokinetic and pharmacodynamic profile, decreased food interactions, and decreased need for therapeutic drug monitoring. Treating and preventing VTE with traditional anticoagulants in pediatric patients presents many challenges. This systematic review evaluated the current literature regarding pediatric NOAC trials. Additionally, based on an up-to-date query of clinicaltrials.gov, we detail current ongoing and as-yet unpublished clinical trials, study outcomes, and projected completion dates. Published pediatric NOAC trials have included 1,007 total children to date and have ranged from phase 1 to 4, with "indications" including both thromboembolism prophylaxis and VTE treatment. Three recent phase 3 trials, specifically involving rivaroxaban and dabigatran, have shown the agents to be at least as effective as traditional anticoagulants for acute and/or extended VTE treatment, with low frequency of recurrent thrombosis and clinically significant bleeding rates. Additionally, specially developed and tested pediatric formulations have allowed for accurate and reliable dosing, oral administration, stable pharmacokinetics and pharmacodynamics, and fewer drug or food interactions. Ongoing trials, anticipated for completion in the next few years, will reveal important information with regard to thromboembolism prophylaxis in special pediatric subpopulations and settings.

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.

International pediatric thrombosis network to advance pediatric thrombosis research: Communication from the ISTH SSC subcommittee on pediatric and neonatal thrombosis and hemostasis

Pediatric thromboembolism is a rare and heterogenous disease. As a result, there is a paucity of knowledge with regard to natural history, management, and outcomes of most types of pediatric venous and arterial thromboembolism. International research collaboration is needed to fill these knowledge gaps. Not only randomized controlled trials, but also representative observational studies are required to answer all research questions. Therefore, the ISTH SSC Subcommittee on Pediatric and Neonatal Thrombosis and Hemostasis initiated the International Pediatric Thrombosis Network (IPTN). The aims of the IPTN include (1) development of the Throm-PED registry to facilitate international prospective observational studies, and (2) establishment of a network of pediatric thrombosis centers experienced in effectively conducting clinical trials and observational studies. The IPTN needs dedicated clinicians all over the world and several funding sources to obtain high-quality research data to reach its ultimate goal of improving care in children with thrombosis. The aim of this communication is to call for active participation in the IPTN to all physicians taking care of children with thrombosis worldwide.

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.

Performance of two clinical scales to assess quality of life in patients with post-thrombotic syndrome

OBJECTIVE

We directly compared the Villalta scale and the Venous Clinical Severity Score (VCSS) to determine which of the two measures would be better at capturing clinically important cases of post-thrombotic syndrome (PTS) and PTS severity compared with patient-reported quality of life (QOL) scores.

METHODS

We performed a secondary analysis of the ATTRACT (acute venous thrombosis: thrombus removal with adjunctive catheter-directed thrombolysis) trial study population. We calculated the correlations of the Villalta scores and VCSSs with QOL scores (short-form 36-item health survey [SF-36] physical component summary [PCS] and mental component summary [MCS]; and VEINES [venous insufficiency epidemiological and economic study]-QOL/symptom [VEINES-QOL/Sym] questionnaire) at each study visit (6, 12, 18, and 24 months of follow-up). The correlation of the random intercept (mean scores) and random slope (rate of change of the scores) among the Villalta scores, VCSS, and VEINES-QOL/Sym scores was assessed using a multivariate longitudinal model.

RESULTS

The median correlation between Villalta scores and VCSSs was 0.72. The median correlation between the Villalta scores and VEINES-QOL and VEINES-Sym scores at all follow-up visits was -0.68 and -0.71, respectively. The median correlation between the Villalta scores and SF-36 PCS and MCS scores was -0.51 and -0.31, respectively. For the VCSSs, the median correlation with the VEINES-QOL and VEINES-Sym scores at all follow-up visits was -0.39 and -0.41, respectively. The median correlation between the VCSSs and SF-36 PCS and MCS scores was -0.32 and -0.13, respectively. The correlations between the random effects in the multivariate longitudinal models showed a similar pattern. The effect of covariate adjustment by age, sex, and body mass index was minor.

CONCLUSIONS

The Villalta scores and VCSSs correlated strongly. The Villalta scale showed a substantially greater correlation with venous disease-specific and general QOL scores compared with the correlation with the VCSS. Our findings suggest that when a single scale is used to assess for clinically meaningful PTS, the Villalta scale will better capture the effects of PTS on patient-reported QOL.

Risk factors for the development of hospital-acquired pediatric venous thromboembolism-Dealing with potentially causal and confounding risk factors using a directed acyclic graph (DAG) analysis

Introduction

Hospital-acquired venous thromboembolism (HA-VTE) in children comprises multiple risk factors that should not be evaluated separately due to collinearity and multiple cause and effect relationships. This is one of the first case-control study of pediatric HA-VTE risk factors using a Directed Acyclic Graph (DAG) analysis.

Material and methods

Retrospective, case-control study with 22 cases of objectively confirmed HA-VTE and 76 controls matched by age, sex, unit of admission, and period of hospitalization. Descriptive statistics were used to define distributions of continuous variables, frequencies, and proportions of categorical variables, comparing cases and controls. Due to many potential risk factors of HA-VTE, a directed acyclic graph (DAG) model was created to identify confounding, reduce bias, and increase precision on the analysis. The final model consisted of a DAG-informed conditional logistic regression.

Results

In the initial conventional univariable model, the following variables were selected as potential risk factors for HA-VTE: length of stay (LOS, days), immobility, ICU admission in the last 30 days, LOS in ICU, infection, central venous catheter (CVC), number of CVCs placed, L-asparaginase, heart failure, liver failure, and nephrotic syndrome. The final model using the set of variables selected by DAG analysis revealed LOS (OR = 1.106, 95%CI = 1.021–1.198, p = 0.013), L-asparaginase (OR = 26.463, 95%CI = 1.609–435.342, p = 0.022), and nephrotic syndrome (OR = 29.127, 95%CI = 1.044–812.508, p = 0.004) as independent risk factors for HA-VTE.

Conclusion

The DAG-based approach was useful to clarify the influence of confounders and multiple causalities of HA-VTE. Interestingly, CVC placement—a known thrombotic risk factor highlighted in several studies—was considered a confounder, while LOS, L-asparaginase use and nephrotic syndrome were confirmed as risk factors to HA-VTE. Large confidence intervals are related to the sample size; however, the results were significant.

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.

The Edoxaban Hokusai VTE PEDIATRICS Study: An open-label, multicenter, randomized study of edoxaban for pediatric venous thromboembolic disease

BACKGROUND

Little evidence is available for treatment of pediatric venous thromboembolism (VTE). Large randomized controlled trials are challenging in children. Current antithrombotic agents have many limitations, including nonoral administration and frequent monitoring. Edoxaban is an oral direct inhibitor of factor Xa without need of monitoring. In adults with VTE, edoxaban has shown to be effective and safe.

OBJECTIVES

The Edoxaban Hokusai VTE PEDIATRICS Study is an open-label, randomized clinical trial to evaluate pharmacokinetics (PK) and pharmacodynamics (PD) of edoxaban and whether edoxaban is noninferior to standard of care in treatment of pediatric VTE.

METHODS

A goal of 274 patients will be recruited in 5 age categories. A multidose PK/PD assessment on day 5 in the first 12 patients of each age group is incorporated into this study. The primary composite efficacy outcome comprises symptomatic recurrent VTE, death due to VTE, and no change or extension of thrombotic burden. The principal safety end point is a combination of major and clinically relevant nonmajor bleeding. PK end points include apparent systemic clearance and volume of distribution of edoxaban. PD end points include prothrombin time, activated partial thromboplastin time, and anti-factor Xa level for the edoxaban treatment arm.

RESULTS

To increase feasibility, the multidose PK/PD study is integrated in the phase 3 trial. In addition, thrombotic burden, which is a prognostic factor for post thrombotic syndrome in children, is one of the components of the primary composite efficacy outcome.

CONCLUSION

This study will increase the level of evidence for treatment in pediatric VTE.

Hospital-Associated Venous Thromboembolism in a Pediatric Cardiac ICU: A Multivariable Predictive Algorithm to Identify Children at High Risk

OBJECTIVES

Critically ill children with cardiac disease are at significant risk for hospital-associated venous thromboembolism, which is associated with increased morbidity, hospital length of stay, and cost. Currently, there are no widely accepted guidelines for prevention of hospital-associated venous thromboembolism in pediatrics. We aimed to develop a predictive algorithm for identifying critically ill children with cardiac disease who are at increased risk for hospital-associated venous thromboembolism as a first step to reducing hospital-associated venous thromboembolism in this population.

DESIGN

This is a prospective observational single-center study.

SETTING

Tertiary care referral children's hospital cardiac ICU.

PATIENTS

Children less than or equal to18 years old admitted to the cardiac ICU who developed a hospital-associated venous thromboembolism from December 2013 to June 2017 were included. Odds ratios and 95% CIs are reported for multivariable predictors.

MEASUREMENTS AND MAIN RESULTS

A total of 2,204 separate cardiac ICU encounters were evaluated with 56 hospital-associated venous thromboembolisms identified in 52 unique patients, yielding an overall prevalence of 25 hospital-associated venous thromboembolism per 1,000 cardiac ICU encounters. We were able to create a predictive algorithm with good internal validity that performs well at predicting hospital-associated venous thromboembolism. The presence of a central venous catheter (odds ratio, 4.76; 95% CI, 2.0-11.1), sepsis (odds ratio, 3.5; 95% CI, 1.5-8.0), single ventricle disease (odds ratio, 2.2; 95% CI, 1.2-3.9), and extracorporeal membrane oxygenation support (odds ratio, 2.7; 95% CI, 1.2-5.7) were independent risk factors for hospital-associated venous thromboembolism. Encounters with hospital-associated venous thromboembolism were associated with a higher rate of stroke (17% vs 1.2%; p < 0.001).

CONCLUSIONS

We developed a multivariable predictive algorithm to help identify children who may be at high risk of hospital-associated venous thromboembolism in the pediatric cardiac ICU.

In Children with Provoked Venous Thromboembolism, Increasing Plasma Coagulability during the First 3 Months Postdiagnosis is Prognostic of Recurrence

Prognostic factors for venous thromboembolism (VTE) recurrence following provoked VTE are largely unknown. Using the Clot Formation and Lysis (CloFAL) assay, single institutional research has shown overall improvement in acute hypercoagulability during the first 3 months postpediatric VTE, yet a rise in plasma coagulability in a subgroup of patients. We sought to define the incidence of rise in coagulability during the first 3 months post-provoked VTE, to investigate its relationship with elevated D-dimer, and to test the hypothesis that a marked rise in coagulability is independently prognostic of VTE recurrence. CloFAL and D-dimer assays were performed on plasma at 4 to 6 weeks and 3 months post-VTE in the Johns Hopkins pediatric VTE cohort and National Institutes of Health-sponsored Kids-DOTT trial. Associations of VTE recurrence with D-dimer and CloFAL assay measures were evaluated via logistic regression. Eighty-seven patients were included. Median follow-up was 1 year. Complete veno-occlusion was determined in 12% at 6 weeks. During the first 3 months post-VTE, a marked rise in coagulability was observed by CloFAL assay in 17% of patients, while D-dimer was elevated in 21%. Recurrent VTE occurred in 10% of patients. CloFAL assay, but not D-dimer, was associated with recurrence (odds ratio [OR] 5.87, 95% confidence interval [95% CI], 1.34-25.8]). After adjustment for veno-occlusion, patients with a marked rise in coagulability by CloFAL assay had a 10-fold increased risk of recurrent VTE (OR 10.33 [95% CI, 1.83-58.19]). Future work should seek to elucidate the mechanisms underlying a rise in plasma coagulability following provoked VTE and to substantiate its prognostic utility for recurrent VTE.

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.

Venous thromboembolism in children undergoing surgery: incidence, risk factors and related adverse events

Background

Although less common in adults, venous thromboembolism (VTE) in children is a highly morbid, preventable adverse event. While VTE has been well studied among pediatric hospitalized and trauma patients, limited work has been done to examine postoperative VTE in children undergoing surgery.

Methods

Using data from National Surgical Quality Improvement Project Pediatric database (NSQIP-P) from 2012 to 2016, a retrospective cohort analysis was performed to determine the incidence of, and risk factors for, VTE in children undergoing surgery. Additionally, the relationships between VTE and other postoperative adverse outcomes were evaluated.

Results

Of 361 384 pediatric surgical patients, 378 (0.10%) were identified as experiencing postoperative VTE. After controlling for patient and surgical factors, we found that American Society of Anesthesiologists (ASA) class of II or greater, aged 16–18 years, non-elective surgery, general surgery (compared with several other surgical specialties), cardiothoracic surgery (compared with general surgery) and longer operative time were significantly associated with VTE in pediatric patients (p<0.001 for each comparison). Furthermore, a majority of adverse events were found to be associated with increased risk of subsequent VTE (p<0.001).

Conclusion

In a large pediatric surgical population, an incidence of postoperative VTE of 0.10% was observed. Defined patient and surgical factors, and perioperative adverse events were found to be associated with such VTE events.

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.