Long-term follow-up of Greenfield inferior vena cava filter placement in children

Management options for pediatric venous thromboembolic disease: Beyond anticoagulation with endovascular therapies

Venous thromboembolism (VTE) in pediatric patients is an uncommon but serious diagnosis that has an array of therapeutic options and challenges. An assessment of the existing literature on management of pediatric patients with VTE was conducted. The interventions reviewed include anticoagulation, thrombolysis, thrombectomy, inferior vena cava (IVC) filters, and venous stenting. For each intervention, a discussion of mechanism of action, indications, contraindications, and potential complications was performed. While anticoagulants are considered the first-line pediatric VTE treatment, many drugs remain investigational in this patient population and treatment recommendations are extrapolated from adult practice. Thrombolysis may be indicated in cases of acute thrombosis requiring more rapid clot resolution but presents a greater bleeding risk than anticoagulation. Similarly, thrombectomy also provides rapid clot resolution and offers a larger therapeutic window and usage in more mature thrombi than thrombolysis. In select patient groups, IVC filters may be indicated in the prevention of PE but present with inherent thrombogenicity and risk of migration. The data regarding pediatric VTE treatment options, monitoring, and long term outcomes is limited compared to the adult population. The relatively few clinical trials including pediatric patients have a relatively small sample size and are heterogenous with regards to predisposing factors that further exacerbate generalizability. Additional research is needed to help construct and evaluate a robust treatment algorithm for pediatric patients with VTE.

An Up-to-Date Narrative Review on Congenital Heart Disease Percutaneous Treatment in Children Using Contemporary Devices

Background: Congenital heart pathology has a significant burden regarding morbidity and mortality in the pediatric population. Several transcatheter interventions and devices have been designed as an alternative to surgical repair. Percutaneous interventions have been proven to yield good results in most cases but with less stress and trauma than that attributed to surgical treatment, especially in frail pediatric patients. We aimed to review the literature and to investigate the feasibility and efficacy of transcatheter interventions and implantable devices for congenital heart disease management in children. Methods: We performed a search in Scopus and MEDLINE databases using prespecified keywords to retrieve clinical studies published between 2000 and 2021. Results: This article provides an up-to-date review regarding the applicability of interventional techniques in simple inter-atrial or inter-ventricular defects, and in challenging congenital defects, such as hypoplastic left heart syndrome, tetralogy of Fallot, or coronary artery fistula. Furthermore, we reviewed recent indications for defibrillator and cardiac resynchronization therapy, and new and promising devices currently being tested. Conclusion: Transcatheter treatment represents a feasible and efficient alternative to surgical repair of congenital heart defects. Novel devices could extend the indications and possibilities of percutaneous interventions in pediatric patients with congenital heart diseases.

Vena Caval Filters: A Review for Intensive Care Specialists

Venous thromboembolism (VTE) is a common complication among patients in the intensive care unit. While anticoagulation remains standard therapy, vena caval filters are an important alternative when anticoagulation is contraindicated. To determine the safety and efficacy of vena caval filters in the treatment of VTE, a comprehensive review of the English-language medical literature was performed. Except for one randomized controlled trial, the literature supporting the use of vena caval filters consists almost exclusively of case series, which in many instances are limited by incomplete and short follow-up. While case series suggest that filters function effectively in the prevention of pulmonary embolism (2%-4% symptomatic pulmonary embolism [PE], fatal PE < 2%), recent higher quality studies indicate that filters may not provide significant additional protection to that provided by anticoagulation alone. Furthermore, filters are associated with a 2- fold increase in the incidence of recurrent DVT. Until randomized comparative studies are available, the safety and efficacy of all the available devices should be considered to be roughly equivalent. Since filters do not inhibit continued clot formation, all filter patients should receive anticoagulation for durations appropriate for their thrombotic disorder. Although extended anticoagulation may prevent thrombotic complications associated with filter placement, this strategy has yet to be experimentally tested. While many additional indications for vena caval filter use have been proposed (VTE in cancer patients, PE prophylaxis in trauma patients, etc), well-designed clinical trials demonstrating their efficacy in these situations are lacking. Further development of temporary/retrievable filters, which offer the potential to avoid the long-term complications of permanent filters, should be a research priority. Until additional data are available, vena caval filters should generally be restricted to patients with VTE who cannot receive anticoagulation.

A Multicenter Cohort Study of Inferior Vena Cava Filter Use in Children

BACKGROUND

To describe inferior vena cava (IVC) filter use in pediatric patients admitted to U.S. children's hospitals and to determine factors associated with prophylactic placement.

PROCEDURE

This retrospective multicenter cohort study utilized data from the Pediatric Health Information Systems (PHIS) administrative database, with 44 participating children's hospitals. Subjects included for analysis were less than 21 years of age, admitted to a PHIS hospital between January 1, 2004 and December 31, 2012 and had a procedure code for IVC filter placement. ICD-9-CM discharge codes were used to identify subjects with a venous thromboembolism (VTE). Pharmaceutical billing codes were used to identify anticoagulation use.

RESULTS

During this 9-year-study period, 276 subjects met the inclusion criteria. The median age of subjects was 15 years (range 1 month-20 years). Subjects had an ICD-9-CM code for VTE 76% of the time and were started on anticoagulation after IVC filter placement 77% of the time. The mean number of IVC filters placed per year was 6 per 100,000 admissions (SD-1.4), which was constant throughout the study period (P = 0.12). The median number of filters placed by center was 4.5 (range 0-32). In multivariate analysis, subjects undergoing orthopedic surgery were more likely to have prophylactic placement of an IVC filter (OR 4.5; 95%CI 1.8-11).

CONCLUSIONS

IVC filter placement in pediatric patients remains a rare event and is most common in adolescents. Unlike in adults, pediatric IVC filter placement does not appear to be increasing over time and is predominantly used in the setting of a venous thrombotic event.

Inferior vena cava (IVC) filters in children: A 10-year single center experience

BACKGROUND

Venous thromboembolism (VTE) is an increasingly recognized problem among children and adolescents. Although inferior vena cava (IVC) filter placement for pulmonary embolism prevention is well reported in adults, data regarding safety and efficacy in the pediatric age group are lacking.

PROCEDURE

At a large university hospital with a level I trauma center, medical records of children and adolescents who underwent IVC filter insertion were reviewed. Appropriateness of referral for retrieval was assessed in each case.

RESULTS

Fifty-nine children and adolescents (mean age 16 years) successfully underwent IVC filter insertion. All filters placed were retrievable. In 47 patients (79.7%), prophylactic filters were placed in the absence of acute VTE in the setting of trauma. In eight patients (13.5%), filters were placed due to contraindication to anticoagulation therapy with concomitant lower extremity deep vein thrombosis or pulmonary embolism. Filters were successfully retrieved in only 12 patients (20.3%), although an attempt at removal was appropriate and feasible in over 90% of cases. Mean duration of follow-up was 2.1 (range 0.4-7.3) years. A significantly higher retrieval rate was found in patients followed at our thrombosis clinic (P < 0.01). Ten patients (17%) experienced at least one filter-related complication.

CONCLUSIONS

Although in most cases, IVC filters were placed for prophylactic indications, the evidence to support their role in this setting is limited. Their low retrieval rate and high filter-related complication rate question their extensive utilization in children. Dedicated follow-up is necessary to detect complications and to ensure that an attempt at retrieval is made when feasible.

Extensive thrombotic complications after inferior vena cava filter placement in 2 adolescents with spinal cord injury: a cautionary tale and review

We report extensive thrombotic complications of inferior vena cava (IVC) filters that were placed for primary prophylaxis in 2 pediatric trauma patients with spinal cord injuries. Although thrombosis is a known common complication in adults with IVC filters, we were unable to find any reports in the literature of this complication in children. These cases highlight a significant problem with the use of prophylactic IVC filters that are not subsequently retrieved, particularly in young trauma patients with decades to live. The overall reported complications of IVC filters in the pediatric literature are also reviewed.

Pulmonary embolism in children

Unlike in adults, pulmonary embolism (PE) is an infrequent event in children. It has a marked bimodal distribution during the paediatric years, occurring predominantly in neonates and adolescents. The most important predisposing factors to PE in children are the presence of a central venous line (CVL), infection, and congenital heart disease. Clinical signs of PE are non-specific in children or can be masked by underlying conditions. Diagnostic testing is necessary in children, especially with the lack of clinical prediction rules. Recommendations for tests are derived from adult studies with ventilation/perfusion (V/Q) scintigraphy being well established. There exists an increasing role for computerised tomography pulmonary angiography (CTPA) and magnetic resonance pulmonary angiography (MRPA). Thrombotic events in children are initially treated with unfractionated heparin (UFH) or low molecular weight heparin (LMWH). For the extended anticoagulant therapy LMWH or vitamin K antagonists can be used with duration of treatment recommendations extrapolated from adult data. Mortality rates for PE in children are reported to be around 10%, with death usually related to the underlying disease processes. Exact data about recurrence risk in children is unknown. Because of the difference in aetiology, presentation, diagnostic methods and treatment between adults and children further research is necessary to assess the validity of recommendations for children.

Antithrombotic therapy in neonates and children: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines

BACKGROUND

Neonates and children differ from adults in physiology, pharmacologic responses to drugs, epidemiology, and long-term consequences of thrombosis. This guideline addresses optimal strategies for the management of thrombosis in neonates and children.

METHODS

The methods of this guideline follow those described in the Methodology for the Development of Antithrombotic Therapy and Prevention of Thrombosis Guidelines: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines.

RESULTS

We suggest that where possible, pediatric hematologists with experience in thromboembolism manage pediatric patients with thromboembolism (Grade 2C). When this is not possible, we suggest a combination of a neonatologist/pediatrician and adult hematologist supported by consultation with an experienced pediatric hematologist (Grade 2C). We suggest that therapeutic unfractionated heparin in children is titrated to achieve a target anti-Xa range of 0.35 to 0.7 units/mL or an activated partial thromboplastin time range that correlates to this anti-Xa range or to a protamine titration range of 0.2 to 0.4 units/mL (Grade 2C). For neonates and children receiving either daily or bid therapeutic low-molecular-weight heparin, we suggest that the drug be monitored to a target range of 0.5 to 1.0 units/mL in a sample taken 4 to 6 h after subcutaneous injection or, alternatively, 0.5 to 0.8 units/mL in a sample taken 2 to 6 h after subcutaneous injection (Grade 2C).

CONCLUSIONS

The evidence supporting most recommendations for antithrombotic therapy in neonates and children remains weak. Studies addressing appropriate drug target ranges and monitoring requirements are urgently required in addition to site- and clinical situation-specific thrombosis management strategies.

Pneumothorax, pneumomediastinum, and pulmonary embolism

This article discusses pneumothorax, pneumomediastinum, and pulmonary embolism in pediatric practice. Although children appear to have better outcomes than adults, the risk factors are substantial. Topics covered include the pathophysiology incidence, presentation, diagnosis, and management of these diseases.

Septic Pulmonary Embolism Case Report: Optimal Outcome after Insertion of an Inferior Vena Cava Filter in a Patient with Staphylococcus aureus Bacteraemia

A 14-year-old patient presented with bilateral pneumonia and pleural effusions, septic arthritis of the hip, deep venous thrombosis, and pulmonary thromboembolism. Methicillin-sensitive Staphylococcus aureus (S. aureus) containing the Panton Valentine Leukocidin (PVL) genes was isolated. Contraindication to anticoagulation prompted inferior vena cava filter placement. He completed 4 weeks of treatment with flucloxacillin, with good clinical outcome. S. aureus containing PVL genes should be sought in cases of necrotizing pneumonia as it seems to increase the risk of severe multifocal infection and thrombotic complications. There are few reports of placement of filters during S. aureus sepsis and bacteraemia. This case highlights that when anticoagulation is not feasible, an inferior vena cava filter can be inserted safely, even in patients with active sepsis and high risk for seeding of the filter. Long-term follow-up confirmed a successful outcome with sterilization of the septic thrombosis with no further pulmonary embolism or additional sepsis episodes.

Postoperative pulmonary embolism in a three year old with Klippel-Trenaunay syndrome

Massive pulmonary embolism (PE) in a small child is a rare event and unified guidelines for its treatment are missing. Timely diagnosis and management of massive pulmonary embolism is of crucial importance for a good outcome. We describe a unique management of PE causing oxygenation failure using a combination of catheter extraction technique, and regional thrombolysis on top of systemic heparin administration and inferior vena cava filter placement. Pulmonary hypertension was treated with inhaled nitric oxide. We believe that catheter extraction technique and regional thrombolysis is an option to consider provided that resources and expertise are available. Preoperative placement of an inferior vena cava filter should be contemplated in such high risk situations.

A prospective observational study of IVC filters in pediatric patients

BACKGROUND

The use of inferior vena cava (IVC) filters to prevent pulmonary embolism (PE) has increased with the advent of retrievable filters (Crowther: Am J Med 120: S13-S17, 2007). Both permanent and retrievable filters have been used in the pediatric population, though reports describing such patients and their outcomes are limited.

PROCEDURE

Our center has established a longitudinal prospective cohort study of consecutive patients with acute venous thromboembolism (VTE) at our pediatric tertiary care institution. Data collection in this study includes medical history, risk factors, radiologic and laboratory studies, therapy, and follow-up.

RESULTS

Two hundred ten patients were enrolled into this cohort from January 2003 to January 2007. IVC filters were percutaneously placed into 11 patients, ranging in age from 6.8 to 23.4 years. The primary reason for filter placement was a VTE and a contraindication to anticoagulation. Nine patients had retrievable filters placed and two received permanent filters. Seven of the nine retrievable filters were removed 21-97 days (median 37 days) after placement. In the remaining two patients, thrombus prevented removal in one, and the filter was electively retained in the other. One patient with a permanent filter died from malignancy. The three patients who are alive and well with IVC filters have had them for 25-60 months. No patient with an IVC filter developed a subsequent PE.

CONCLUSIONS

Approximately 5% of patients in this pediatric thrombosis cohort received an IVC filter. The placement and removal of these devices is technically feasible in children.

Antithrombotic therapy in neonates and children: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition)

This chapter about antithrombotic therapy in neonates and children is part of the Antithrombotic and Thrombolytic Therapy: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition). Grade 1 recommendations are strong and indicate that the benefits do, or do not, outweigh risks, burden, and costs, and Grade 2 suggests that individual patient values may lead to different choices (for a full understanding of the grading, see Guyatt et al in this supplement, pages 123S-131S). In this chapter, many recommendations are based on extrapolation of adult data, and the reader is referred to the appropriate chapters relating to guidelines for adult populations. Within this chapter, the majority of recommendations are separate for neonates and children, reflecting the significant differences in epidemiology of thrombosis and safety and efficacy of therapy in these two populations. Among the key recommendations in this chapter are the following: In children with first episode of venous thromboembolism (VTE), we recommend anticoagulant therapy with either unfractionated heparin (UFH) or low-molecular-weight heparin (LMWH) [Grade 1B]. Dosing of IV UFH should prolong the activated partial thromboplastin time (aPTT) to a range that corresponds to an anti-factor Xa assay (anti-FXa) level of 0.35 to 0.7 U/mL, whereas LMWH should achieve an anti-FXa level of 0.5 to 1.0 U/mL 4 h after an injection for twice-daily dosing. In neonates with first VTE, we suggest either anticoagulation or supportive care with radiologic monitoring and subsequent anticoagulation if extension of the thrombosis occurs during supportive care (Grade 2C). We recommend against the use of routine systemic thromboprophylaxis for children with central venous lines (Grade 1B). For children with cerebral sinovenous thrombosis (CSVT) without significant intracranial hemorrhage (ICH), we recommend anticoagulation initially with UFH, or LMWH and subsequently with LMWH or vitamin K antagonists (VKAs) for a minimum of 3 months (Grade 1B). For children with non-sickle-cell disease-related acute arterial ischemic stroke (AIS), we recommend UFH or LMWH or aspirin (1 to 5 mg/kg/d) as initial therapy until dissection and embolic causes have been excluded (Grade 1B). For neonates with a first AIS, in the absence of a documented ongoing cardioembolic source, we recommend against anticoagulation or aspirin therapy (Grade 1B).

Venous thromboembolism in children

With improved pediatric survival from serious underlying illnesses, greater use of invasive vascular procedures and devices, and a growing awareness that vascular events occur among the young, venous thromboembolism (VTE) increasingly is recognized as a critical pediatric concern. This review provides background on etiology and epidemiology in this disorder, followed by an in-depth discussion of approaches to the clinical characterization, diagnostic evaluation, and management of pediatric VTE. Prognostic indicators and long-term outcomes are considered, with emphasis on available evidence underlying current knowledge and key questions for further investigation.

Pulmonary Embolism in an Adolescent Soccer Player

Pulmonary emboli are potentially life threatening and are rare in the young, healthy, athletic population. We describe the presentation of pulmonary emboli in an otherwise healthy athlete; this has not been reported previously in the literature. A 16-yr-old male soccer player with no apparent risk factors presented in distress with bilateral pulmonary emboli. An extensive workup did not reveal a cause for this phenomenon. The patient was anticoagulated, and a Greenfield inferior vena cava filter was placed because of recurrent symptoms and poor compliance with anticoagulation. This case report illustrates the importance of considering pulmonary embolism as a diagnosis in athletes who present with sudden onset of dyspnea with no discernable cause. Greenfield filter placement in the management of these cases remains controversial.

Iliofemoral Deep Vein Thrombosis in Childhood; Developing a Management Protocol

OBJECTIVE

To develop an evidence-based protocol for the management of iliofemoral deep vein thrombosis (IDVT) in childhood.

METHODS

A search of the literature was undertaken. All publications pertaining to IDVT in childhood were analysed and then categorised according to their level of evidence. Recommendations were then made on the basis of this.

RESULTS

The commonest presenting symptoms were pain and swelling in the affected limb (evidence level II). Predisposing risk factors of special significance in children included the recent use of a venous access device, malignancy, prothrombotic disorders, infection, surgery and congenital venous anomalies (evidence level II). The most frequently described imaging modalities were B-mode ultrasonography, duplex, venography, and helical CT (evidence level III). The mainstay of treatment was anticoagulation with LMWH alone or followed by warfarin (evidence level I). Early clot removal through catheter-directed thrombolysis or surgical thrombectomy has been shown to be beneficial (evidence level II/III). There is little evidence for the benefit of early mobilisation and compression therapy in childhood.

CONCLUSION

Level I evidence relating to IDVT in childhood is sparse. The possibility of IDVT should be considered when examining a child with a swollen and painful limb. Imaging should be with duplex ultrasound, followed by spiral CT to include assessment of the IVC. A thrombophilia screen should be taken prior to anticoagulation with LMWH (and warfarin). Thrombolysis should be considered in cases of extensive IDVT.

Venous thrombosis associated with staphylococcal osteomyelitis in children

BACKGROUND

Venous thrombosis (VT) in children with Staphylococcus aureus osteomyelitis occurs rarely. We describe clinical features of infections and molecular characterization of isolates of children at Texas Children's Hospital with S aureus osteomyelitis and VT.

METHODS

We reviewed records and imaging studies (chest radiographs, ultrasound, computed tomography, and MRI) of 9 patients at Texas Children's Hospital with acute S aureus osteomyelitis and new onset VT between August 1999 and December 2004. Isolates were fingerprinted by pulsed-field gel electrophoresis and tested for the presence of genes encoding selective virulence factors.

RESULTS

The mean age of the patients was 10.6 years. All 9 of the patients had osteomyelitis with sites of infection adjacent to the VT. The femoral and popliteal veins were most commonly affected. Two patients had VTs develop on the same side in which a central line had been in place. Four patients had chest radiographs consistent with septic emboli; inferior vena cava filters were placed in 3. Evaluation for hypercoagulable state revealed 3 patients with lupus anticoagulant, 1 with anticardiolipin IgG antibody, and 5 with no defect. Most laboratory abnormalities had resolved at follow-up. Seven patients had infections caused by methicillin-resistant S aureus belonging to the same clonal group (USA300); all were community acquired. Seven isolates carried the Panton-Valentine leukocidin (luk-S-PV and luk-F-PV) genes.

CONCLUSIONS

The predominant community-acquired, methicillin-resistant S aureus clone in Houston, Texas, (USA300) may have a unique propensity to cause VT in association with osteomyelitis. Management of the venous thrombosis in this setting may be complicated by the rapid evolution of septic emboli.

Use of Vena Cava Filters in Pediatric Trauma Patients: Data from the National Trauma Data Bank

BACKGROUND

Placement of vena cava filters (VCFs) in high-risk adult trauma patients is a well-described intervention for prophylaxis against pulmonary embolism (PE). Few data exist regarding the use of VCFs in pediatric trauma.

METHODS

We performed a cross-sectional study using the National Trauma Data Bank of the American College of Surgeons. Patients 17 years old or younger were included. Data regarding demographics, injuries, hospitalization, survival, and treating institution were analyzed. The prevalence of deep vein thrombosis (DVT), PE, and VCF placement were calculated. Odds ratios (ORs) for predictors of VCF placement were determined using multivariate logistic regression.

RESULTS

There were 116,357 pediatric patients in the National Trauma Data Bank. VCFs were placed in 214 (0.18%) patients. VCF patients had longer mean hospital (23.99 vs. 4.12 days) and intensive care unit stays (13.65 vs. 1.12 days) and more severe injuries (mean Injury Severity Score, 30.89 vs. 9.04) than those without VCFs. Sixty-five patients had DVT, and PE was diagnosed in 28 patients, representing 0.06% and 0.02% of the cohort, respectively. University-associated teaching hospitals placed 72.4% (95% confidence interval, 65.9-78.3%) of VCFs and Level I trauma centers placed 46.3% (95% confidence interval, 39.4-53.2%) of VCFs. In multivariate analysis, significant predictors of VCF use were DVT (OR, 33.13), spinal cord injury (OR, 15.28), probability of survival (OR, 10.52), severe femur fracture (OR, 3.39), increasing age (OR, 1.99), ISS (OR, 1.05), intensive care unit stay (OR, 1.04), and length of stay (OR, 1.02). Higher Glasgow Coma Scale score decreased the likelihood of VCF use (OR, 0.87).

CONCLUSION

Placement of VCFs in pediatric trauma patients is uncommon and is associated with several characteristics of the patient, the injury, and the treating institution. Long-term VCF efficacy in pediatric trauma is not known, and application of VCFs in these patients requires further investigation.

A six-year old with fatal pulmonary embolism

Pulmonary thromboembolism is rarely recognized in young children, even in hospital settings. All current management decisions for children with deep vein thrombosis (DVT) are directly extrapolated from treatment recommendations for adults with no further validation. We report the case of a 6-y-old child presenting with deep vein thrombosis of the leg veins and fatal pulmonary embolism. The fatal outcome in our case highlights the need for more epidemiological studies in children, not only to predict the recurrence of pulmonary emboli but also to prepare standard treatment guidelines for the management of DVT and pulmonary emboli in children. We speculate that there may be a role for temporary inferior vena cava filters in young children with extensive DVT of the legs.

CONCLUSIONS

This case highlights the need for more epidemiological studies to predict the recurrence of pulmonary emboli and effective guidelines for the management of paediatric DVT and pulmonary emboli in children.

Percutaneous treatment of pediatric thrombosis

While rare, thrombosis in the pediatric population can result serious sequelae including death. The best treatment options have not yet been firmly established for this age group. During childhood, there are age-related changes in components of the coagulation system that can affect treatment choices. This review article gives an overview of pediatric coagulation and describes the current state of percutaneous treatment options including local thrombolysis and thrombectomy.

Central venous catheter occlusion and thrombosis

Central venous catheters are widely used in children with critical illness and chronic disease. These devices are often essential in the delivery of medications and intravenous fluids and in hemodynamic monitoring. Central venous catheter occlusion and thrombosis are common problems in patients using these devices. This article reviews the background, pathophysiology, and incidence of catheter occlusion and catheter-related thrombosis. Diagnostic, preventive, and treatment strategies, along with future research directions, are addressed.

Thromboembolism in children

Acquired and inherited prothrombotic risk factors increase the risk of thrombosis in children. This review is based on "milestone" pediatric reports and new literature data (January 2001-February 2002) on the presence of acquired and inherited prothrombotic risk factors, imaging methods, and treatment modalities in pediatric thromboembolism. After confirming clinically suspected thromboembolism with suitable imaging methods, pediatric patients should be screened for common gene mutations (factor V G1691A, prothrombin G20210A and MTHFR C677T genotypes), rare genetic deficiencies (protein C, protein S, antithrombin, and plasminogen), and new candidates for genetic thrombophilia causing elevated levels of lipoprotein(a), and homocysteine, and probable genetic risk factors (elevations in fibrinogen, factor IX, and factor VIIIC, and decreases in factor XII). Data interpretation is based on age-dependent reference ranges or the identification of causative gene mutations/polymorphisms with respect to individual ethnic backgrounds. Pediatric treatment protocols for acute thromboembolism, including thrombolytic and anticoagulant therapy, are mainly adapted from adult patient protocols.