Thromboembolism and resistance to activated protein C in children with underlying cardiac disease

Thrombophilia, left ventricular dysfunction and intracardiac thrombi in children

Background and Objectives

Reports on the incidence of intracardiac thrombi (ICT) have increased over the last few decades, but ICT are still relatively rare among children. Left ventricular systolic dysfunction and dilatation may contribute to the formation of ICT, especially when a hypercoagulable state exists. The aim of this study was to describe the incidence of ICT in children suffering from cardiac failure with left ventricular dysfunction and to identify risk factors on admission for developing ICT.

Subjects and Methods

We conducted a retrospective chart review of children up to 18 years of age admitted to the Pediatric Intensive Care Unit due to cardiac failure with left ventricular dysfunction between January 1, 2003 and December 31, 2008.

Results

Twenty-one patients were admitted with clinical signs of cardiac failure and echocardiographic findings compatible with dilated cardiomyopathy or acute myocarditis. Dilated cardiomyopathy was diagnosed in 11 patients (52%). Adenoviruses and enteroviruses were suspected to be the cause of acute myocarditis in 5 cases. The personal or family history of hypercoagulable states were obtained from 19 out of 21 patients (90%). Among patients with a hypercoagulable state, 3 out of 7 developed ICT compared with none out of 12 among patients without hypercoagulability (p=0.043). Two of these 3 patients experienced an embolic event.

Conclusion

Cardiac failure with left ventricular dysfunction may predispose the patient to ICT and increase the risk of thromboembolism, especially when an underlying hypercoagulable state exists. The hypercoagulable state must be carefully evaluated on admission in these patients.

Thrombotic disease in critically ill children

OBJECTIVES

To summarize a) epidemiology of arterial and venous thromboembolism, pulmonary embolism, and deep venous thrombosis in children; b) the risk factors for thrombosis in the pediatric intensive care unit; c) diagnostic techniques for arterial/venous thromboembolism; and d) the current recommendations for management and prevention of thromboembolic disease in critically ill children.

DATA SOURCE

Literature review, using National Library of Medicine PubMed and the following terms: arterial, venous thromboembolism; deep venous thrombosis; pulmonary embolism; thrombosis; as well as citations of interest from these articles.

STUDY SELECTION

Both pediatric and adult literature addressing thrombotic disease were reviewed.

DATA EXTRACTION AND SYNTHESIS

Articles were chosen for more extensive discussion when containing prospective studies, guidelines for practice, or data in critically ill patients. When data in children were unavailable, applicable data in adults were referenced. Due to the paucity of data in critically ill children, available adult and pediatric data were combined with institutional experience to provide suggestions for current practice and future inquiry.

CONCLUSIONS

Increasing awareness regarding the recognition and current approaches to management and prevention of thromboembolic disease in children is needed among pediatric intensivists, so outcome of these life-threatening processes might be improved.

Intracardiac thrombi in pediatric patients: presentation profiles and clinical outcomes

We document the presentation profiles, treatment strategies, and clinical outcomes in a relatively large cohort of pediatric patients with intracardiac thrombi (ICT). We performed a retrospective review of patients diagnosed with ICT by echocardiography at a tertiary pediatric hospital during a 10-year period. These patients received medical therapy or thrombectomy. We provided echocardiographic descriptions of the ICT-size, chamber location, and mobility/morphology. The outcome measures were ICT (persistence, resolution, or embolization), effectiveness of therapy, and patient morbidity and mortality. There were 40 ICT diagnosed in 31 patients (22 males and 9 females). Mean age at diagnosis was 8.8 years (range, 15 days to 18 years). Overall mortality was 12/31 patients (39%); only one death was attributed to ICT embolization. Embolic events occurred in 4/31 patients (13%). The most common initial therapies included heparin infusion (n = 15), warfarin (n = 7), and aspirin (n = 7). The ICT resolved with medical therapy alone in 19/30 patients (63%). One patient required surgical thrombectomy. The cohort was divided into group 1 (dilated cardiomyopathy), group 2 (status post Fontan operation), and group 3 (other diagnoses). In group 1 (n = 11), there were 8 deaths. Embolization occurred in 2/5 large ICT, resulting in cerebral infarction and death (n = 1) and renal infarction (n = 1). The most common ICT location was the left ventricle (n = 10). Severe ventricular systolic dysfunction was present in 10/11 patients (91%). In group 2 (n = 9), there was 1 death. Embolization occurred in 1/7 large ICT, resulting in seizures and temporary paresis. All ICT were located in the Fontan pathway. Severe ventricular systolic dysfunction was present in 2/9 patients (22%). In group 3 (n = 11), there were 3 deaths. Embolization occurred in 1/9 small ICT, resulting in coronary emboli. ICT are most commonly diagnosed in pediatric patients with dilated cardiomyopathy or patients status post Fontan operation. The majority of ICT resolve with medical therapy. Larger ICT tend to embolize more frequently, and the morbidity secondary to embolization is significant. Rarely is mortality due to ICT embolization. The prognosis is poor for patients with left ventricular ICT or ICT in the presence of ventricular systolic dysfunction.

Antithrombotic Therapy in Children*

This article about antithrombotic therapy in children is part of the 7th American College of Chest Physicians Conference on Antithrombotic and Thrombolytic Therapy: Evidence-Based Guidelines. Grade 1 recommendations are strong and indicate that the benefits do, or do not, outweigh the risks, burden, and costs. Grade 2 suggests that individual patients' values may lead to different choices (for a full understanding of the grading see Guyatt et al, CHEST 2004; 126:179S-187S). Among the key recommendations in this article are the following. In neonates with venous thromboembolism (VTE), we suggest treatment with either unfractionated heparin or low-molecular-weight heparin (LMWH), or radiographic monitoring and anticoagulation therapy if extension occurs (Grade 2C). We suggest that clinicians not use thrombolytic therapy for treating VTE in neonates, unless there is major vessel occlusion that is causing the critical compromise of organs or limbs (Grade 2C). For children (ie, > 2 months of age) with an initial VTE, we recommend treatment with i.v. heparin or LMWH (Grade 1C+). We suggest continuing anticoagulant therapy for idiopathic thromboembolic events (TEs) for at least 6 months using vitamin K antagonists (target international normalized ratio [INR], 2.5; INR range, 2.0 to 3.0) or alternatively LMWH (Grade 2C). We suggest that clinicians not use thrombolytic therapy routinely for VTE in children (Grade 2C). For neonates and children requiring cardiac catheterization (CC) via an artery, we recommend i.v. heparin prophylaxis (Grade 1A). We suggest the use of heparin doses of 100 to 150 U/kg as a bolus and that further doses may be required in prolonged procedures (both Grade 2 B). For prophylaxis for CC, we recommend against aspirin therapy (Grade 1B). For neonates and children with peripheral arterial catheters in situ, we recommend the administration of low-dose heparin through a catheter, preferably by continuous infusion to prolong the catheter patency (Grade 1A). For children with a peripheral arterial catheter-related TE, we suggest the immediate removal of the catheter (Grade 2C). For prevention of aortic thrombosis secondary to the use of umbilical artery catheters in neonates, we suggest low-dose heparin infusion (1 to 5 U/h) (Grade 2A). In children with Kawasaki disease, we recommend therapy with aspirin in high doses initially (80 to 100 mg/kg/d during the acute phase, for up to 14 days) and then in lower doses (3 to 5 mg/kg/d for > or = 7 weeks) [Grade 1C+], as well as therapy with i.v. gammaglobulin within 10 days of the onset of symptoms (Grade 1A).

Interaction of fibrinolysis and prothrombotic risk factors in neonates, infants and children with and without thromboembolism and underlying cardiac disease. a prospective study

To evaluate the role of plasminogen activator inhibitor-1 (PAI-1) and tissue-type plasminogen activator (t-PA) in children with an estimated risk of vascular occlusion reported to range from 7% to 16%, we conducted a prospective study in infants and children with underlying cardiac disease. One hundred and twenty-five children (neonate - 16 years) were investigated. In 9 infants out of the 125 children vascular occlusion occurred, closely related to cardiac catheterisation and arterial or venous lines during major cardiac surgery. Six of the nine neonates and infants with (n=6) and without (n=3) prothrombotic risk factors showed evidence of a basically impaired fibrinolytic system. Five of the nine infants showed increased PAI-1 clearly correlated to the 4G/4G genotype of the plasminogen activator-1 promoter polymorphism along with elevated t-PA concentration before the first diagnostic cardiac catheterisation was performed. One infant presented with increased t-PA concentration only. Five of the six children with reduced fibrinolytic capacity had further prothrombotic risk factors.

CONCLUSION

Data of this study indicate that neonates and infants with underlying cardiac disease and basically increased PAI-1 due to the 4G/4G variant of the PAI-1 promoter polymorphism along with elevated t-PA levels in combination with further prothrombotic risk factors are at high risk of developing early thromboembolism during cardiac catheterisation.

Sudden infant death syndrome, childhood thrombosis, and presence of genetic risk factors for thrombosis

Sudden infant death syndrome or "cot death" has until the late eighties been a significant cause of death in children between the ages of 1 month and 1 year. Approximately two per 1000 children born alive dies of sudden infant death syndrome each year in Western Europe, North America, and Australia. The vulnerability of the infant brain stem to ischemia has been suggested to be a conceivable cause of sudden infant death syndrome. This is compatible with a hypothesis that genetic risk factors for cerebral thrombosis could cause microinfarction in the brain stem during the first month of life, affecting vital centers or their blood supply. The presence of three common point mutations seen in families with thrombophilia (1691G-->A in the coagulation factor V gene, 677C-->T in the methylenetetrahydrofolate reductase gene, and the 20210G-->A mutation in the prothrombin gene) could increase the risk for thrombosis in the child. This prompted us to investigate these genetic markers of thromboembolic disease in 121 cases of sudden infant death syndrome and in relevant controls, in the expectation of a more frequent occurrence of these markers if thrombosis is an etiological factor in sudden infant death syndrome. The frequency of homozygous 1691G-->A mutation in SIDS cases was higher than expected (odds ratio: 7.3, 95% confidence interval, 1.2-45.8). The allele frequencies (theta;) in cases of sudden infant death syndrome of the 1691G-->A, 677C-->T, and 20210G-->A alleles was 2.6% (1.0-5.5), 32.6% (26.8-38.9), and 0.9% (0.1-3.4), respectively. None of the allele frequencies found in the background population (3.4% for the 1691G-->A allele, 29% for the 677C-->T allele, and 1% for the 20210G-->A allele) differed significantly from that in cases of sudden infant death syndrome. In 5,251,027 inhabitants in Denmark, the incidence of venous thromboembolism was 0.9 per 1000 per year in the background population, and less than one-thousandth of these were children. Consequently it is not likely that venous thrombosis is a major cause of sudden infant death syndrome. On the other hand, this does not exclude other known or unknown risk factors for thrombosis as possible etiological factors for sudden infant death syndrome. It is likely that we must continuously employ the exclusion principle on possible etiological causes in genetic material from a large group of victims of sudden infant death syndrome if the phenomenon of sudden infant death syndrome is to be ascribed to a specific hereditary disorder.

Postoperative stroke in a child with cerebral palsy heterozygous for factor V Leiden

A 5-year-old with spastic quadraparetic cerebral palsy suffered multiple strokes after extensive orthopedic surgery. Coagulation testing was undertaken to determine whether a familial thrombophilia was present. The patient was found to be heterozygous for factor V Leiden. Factor V Leiden may be a risk factor for central nervous system events in special-needs children, particularly when common medical conditions create additional procoagulant risks.

Prothrombotic abnormalities in children with venous thromboembolism

PURPOSE

The aim of this study was to determine the frequency of acquired or inherited prothrombotic disorders in a pediatric population with venous thromboembolism (VTE).

PATIENTS AND METHODS

From May 1992 to April 1998, 56 consecutive children with VTE were prospectively studied at a single center.

RESULTS

The median age was 8.4 years (range, 0.1-18 years). There was a male predominance. Fifty (89%) children had thrombosis in the lower venous system. Risk factors were detected in 54 (96%) children. Twenty-one (38%) thrombotic episodes were related to central venous lines. Family history of thrombosis was positive in 13 (23%) patients. In 26 (46%) patients, a prothrombotic disorder was detected. Nine of them had inherited disorders (protein C deficiency, 5 patients; protein S deficiency, 3 patients; Factor V Leiden mutation, 1 patient), and 13 children had acquired disorders (antiphospholipid antibodies, 5 patients; antithrombin deficiency, 8 patients). The remaining four showed combined abnormalities (Factor V Leiden mutation associated with inherited protein S deficiency, 1 patient; acquired antithrombin deficiency, 2 patients and inherited antithrombin deficiency, 1 patient).

CONCLUSIONS

In the series, a high percentage of prothrombotic disorders was detected; thus, a complete hemostatic evaluation should be performed in all of the children with VTE whether the patients have one or more risk factors.

Coagulation and fibrinolysis in children, adolescents, and young adults with inflammatory bowel disease

BACKGROUND

Patients with Crohn's disease and ulcerative colitis have an increased risk of thromboembolic events.

METHODS

Data were collected from 24 patients aged 4.5 to 23 years who had inflammatory bowel disease. Platelet count, antithrombin, fibrinogen, prothrombin fragment F1+2, soluble thrombomodulin, tissue plasminogen activator, D-dimer, and plasminogen activator inhibitor-1 antigen were investigated. In addition the response to activated protein C, the factor V R506Q mutation, protein C, free protein S antigen, and lipoprotein (a) were analyzed. These data were compared with medical treatment, duration, and disease activity, estimated with the Pediatric Crohn's Disease Activity Index or the Clinical Colitis Activity Index.

RESULTS

Forty-five percent of our patients showed an increase in fibrinogen, 29% in prothrombin fragment F1+2, and 20% in platelet count, plasminogen activator inhibitor- antigen, and soluble thrombomodulin. Thrombomodulin was higher in active disease than in inactive disease and in Crohn's disease than in ulcerative colitis. Fibrinogen was also higher with Crohn's disease and tended to be higher in active disease than in ulcerative colitis and inactive disease. Plasminogen activator inhibitor-1 antigen was significantly higher in patients with Crohn's disease than in those with ulcerative colitis and was higher in the patient group treated with steroids.

CONCLUSION

As has been shown in adults, young patients with active and inactive inflammatory bowel disease were found to have abnormal coagulation and fibrinolysis. The relevance as a thromboembolic risk factor is discussed.

Resistance to activated protein C in thalassaemic patients: an underlying cause of thrombosis

We evaluated 81 thalassaemia major and 4 thalassaemia intermedia patients (48 M, 37 F), median age 17 years; 62/85 patients were HCV-positive, 3/85 HIV-positive, 19/85 were splenectomized. Forty normal healthy children were recruited as the control group. The number of thrombotic events was studied retrospectively. Platelet poor plasma was filtered and quick-frozen at -70 degrees C until time of assay. APC resistance was measured in an activated thromboplastin time and results were expressed as normalized ratio. All tests were done with diluted 1 in 5 (v/v) factor V deficient plasma and with undiluted plasma. Molecular genetic investigation of factor V gene was performed with polymerase chain reaction, followed by digestion of amplified products with restriction enzyme Mnl I. Data obtained with molecular investigation revealed the presence of 4 heterozygous subjects for factor V Leiden (4.7%). Functional tests were able to detect all heterozygotes for factor V Leiden both with undiluted and with diluted plasma, and there were no false negative subjects. However, undiluted plasma revealed a greater number of false positive subjects (n=15) than did diluted plasma. Therefore, tests done with undiluted and diluted plasma revealed a 100% sensitivity, while specificity was 81% for undiluted plasma and 97% for diluted plasma. Only one thrombotic event was observed in one of the 85 studied patients, as a case of stroke in a thalassaemia intermedia patient with APC resistance. In the same patient an additional thrombogenic risk factor was represented by a pronounced haematocrit increase at the beginning of her transfusion regimen.

Factor V Leiden, protein C, and lipoprotein (a) in catheter-related thrombosis in childhood: a prospective study

OBJECTIVE

To determine the association between catheter-related thromboses and hereditary causes of thrombophilia, including the factor V Leiden mutation, deficiencies of protein C or protein S, or increased lipoprotein (a).

STUDY DESIGN

To evaluate the incidence of genetic risk factors for familial thrombophilia in catheter-related thrombosis, 163 consecutively admitted infants and children (cardiac disease and catheter placement [C] n = 140; Broviac catheter [B] n = 23) were prospectively investigated. In addition, an age-matched, healthy control group undergoing elective surgery (S: n = 155) was investigated.

RESULTS

Heterozygous factor V Leiden mutation was diagnosed in 20 of the 318 study subjects (C: n = 5; B: n = 4; S: n = 11), homozygous factor V Leiden mutation was found in two subjects (C: n = 1; S: n = 1), protein C deficiency type I was diagnosed in nine subjects (C: n = 4; B: n = 1; S: n = 4), and five subjects showed increased lipoprotein (a) (C: n = 3; S: n = 2). The frequency of thrombosis (C: n = 13; B: n = 5) in patients with familial thrombophilia was significantly higher (p < 0.0001; chi square: 27.79) in the catheter groups (15 of 17 subjects) than in control subjects after minor elective surgery (none of 18). Fifteen of the 18 infants with thrombosis had congenital thrombophilia; two children with congenital thrombophilia did not have documented thrombosis, and three infants with vascular occlusion had no inherited predisposition to thrombophilia.

CONCLUSIONS

Genetic risk factors for familial thrombophilia play an important role in the manifestation of catheter-related thromboembolism in children.

Lipoprotein (a): its role in childhood thromboembolism

PURPOSE

Elevated lipoprotein (a) [LP (a)] concentrations are independent risk factors of coronary heart disease or stroke in young adults. To clarify its role in childhood thromboembolism, Lp (a) was measured in 72 children with thromboembolism.

METHODS

In addition to Lp (a), defects of the protein C anticoagulant system, antithrombin, and antiphospholipid antibodies were investigated in children with arterial (n = 36) or venous (n = 36) thrombosis.

RESULTS

Enhanced Lp (a) >50 mg/dL was diagnosed in 8 out of 36 children with arterial and 5 out of 36 patients with venous thrombosis. Of the 72 children, 25 showed the factor V Leiden mutation, 10 showed protein C deficiency, 2 showed antithrombin deficiency, and 4 showed primary antiphospholipid syndrome. Three children with increased Lp (a) were heterozygous for the factor V Leiden mutation, and 1 girl showed additional protein C deficiency.

CONCLUSIONS

Data of this study indicate that increased concentrations of Lp (a) play an important role in childhood thrombosis.