High prevalence of dysfibrinogenemia among patients with chronic thromboembolic pulmonary hypertension

Current understanding of the pathophysiology of chronic thromboembolic pulmonary hypertension

Chronic thromboembolic pulmonary hypertension (CTEPH) is a unique form of pulmonary hypertension arising from fibrotic obliteration of major pulmonary arteries. Pro-thrombotic states, large clot burden and impaired dissolution are believed to contribute to the occurrence and progression of thrombosis after an acute pulmonary embolic event. Recent data utilizing several models have facilitated the understanding of clot resolution. This review summarizes current knowledge on pathophysiological mechanisms of major vessel occlusion in CTEPH.

The pathophysiology of chronic thromboembolic pulmonary hypertension

Chronic thromboembolic pulmonary hypertension (CTEPH) is a rare, progressive pulmonary vascular disease that is usually a consequence of prior acute pulmonary embolism. CTEPH usually begins with persistent obstruction of large and/or middle-sized pulmonary arteries by organised thrombi. Failure of thrombi to resolve may be related to abnormal fibrinolysis or underlying haematological or autoimmune disorders. It is now known that small-vessel abnormalities also contribute to haemodynamic compromise, functional impairment and disease progression in CTEPH. Small-vessel disease can occur in obstructed areas, possibly triggered by unresolved thrombotic material, and downstream from occlusions, possibly because of excessive collateral blood supply from high-pressure bronchial and systemic arteries. The molecular processes underlying small-vessel disease are not completely understood and further research is needed in this area. The degree of small-vessel disease has a substantial impact on the severity of CTEPH and postsurgical outcomes. Interventional and medical treatment of CTEPH should aim to restore normal flow distribution within the pulmonary vasculature, unload the right ventricle and prevent or treat small-vessel disease. It requires early, reliable identification of patients with CTEPH and use of optimal treatment modalities in expert centres.

An Update on the Management of Chronic Thromboembolic Pulmonary Hypertension

Chronic thromboembolic pulmonary hypertension (CTEPH) is a rare but life-threatening form of pulmonary artery hypertension that is defined as a mean arterial pulmonary pressure greater than 25mmHg that persists for more than 6 months following anticoagulation therapy in the setting of pulmonary emboli. CTEPH is categorized by the World Health Organization as group IV pulmonary hypertension and is thought to be due to unresolved thromboemboli in the pulmonary artery circulation. Among the 5 classes of pulmonary hypertension, CTEPH is unique in that it is potentially curable with the use of pulmonary thromboendarterectomy surgery. Despite an increasing array of medical and surgical treatment options for patients with CTEPH over the past 2 decades, patients commonly present with advanced disease and carry a poor prognosis, thus, the need for early diagnosis and appropriate referral to an expert center. This review article first highlights the epidemiology, pathophysiology, and clinical presentation of CTEPH. The article then provides diagnostic and therapeutic algorithms for the management of the patient with suspected CTEPH.

Current concepts in the pathogenesis of chronic thromboembolic pulmonary hypertension

Chronic thromboembolic pulmonary hypertension (CTEPH) is characterized by fibrotic obstruction of the proximal pulmonary arteries, and it is believed to result from incomplete thrombus resolution after acute pulmonary embolism. While treatment for this condition with surgery and medical therapy has improved outcomes, our understanding of the molecular mechanisms underlying CTEPH is incomplete. Numerous risk factors have been associated with the development of CTEPH, including but not limited to acquired thrombophilias and chronic inflammatory states. A minority of patients with CTEPH have an abnormal fibrin structure that may delay thrombus resolution. Recently, examination of resected scar material in patients with CTEPH has suggested that deficient angiogenesis may play a role in thrombus nonresolution, and there is increasing interest in factors that drive intravascular scar formation. An additional challenge in CTEPH research is understanding the etiology and implications of the small-vessel disease present in many patients. Future work will likely be directed at understanding the pathways important to disease pathogenesis through further examinations of resected tissue material, continued work on animal models, and genomic approaches to identify alterations in gene expression or gene variants that may distinguish CTEPH from other forms of pulmonary hypertension.

The clinical significance of antiphospholipid antibodies in systemic lupus erythematosus

Antiphospholipid syndrome (APS) is the association of thrombosis and/or pregnancy morbidity with antiphospholipid antibodies (aPL). Thirty to forty percent of systemic lupus erythematosus (SLE) patients are tested positive for aPL, which may have an impact on the SLE presentation, management, and prognosis. Compared with SLE patients without aPL, those with aPL have a higher prevalence of thrombosis, pregnancy morbidity, valve disease, pulmonary hypertension, livedo reticularis, thrombocytopenia, hemolytic anemia, acute/chronic renal vascular lesions, and moderate/severe cognitive impairment; worse quality of life; and higher risk of organ damage. The use of low-dose aspirin (LDA) is controversial for primary thrombosis and pregnancy morbidity prevention because of the lack of strong prospective controlled data. Similarly, the use of anticoagulation is controversial for patients with an aPL-related nephropathy. Until further studies are available, physicians should discuss the risk/benefits of LDA or anticoagulation as well as the available literature with patients.

Chronic Thromboembolic Pulmonary Hypertension: the End Result of Pulmonary Embolism

Chronic thromboembolic pulmonary hypertension (CTEPH) occurs when a pulmonary embolism fails to undergo complete thrombolysis leading to vascular occlusion and pulmonary hypertension. Despite the fact that CTEPH is a potential consequence of pulmonary embolism, diagnosis requires a high degree of vigilance as many patients will not have a history of thromboembolic disease. The ventilation perfusion scan is used to evaluate for the possibility of CTEPH although right heart catheterization and pulmonary artery angiogram are needed to confirm the diagnosis. Pulmonary thromboendarterectomy is the first-line treatment for patients who are surgical candidates. Recently, riociguat has been approved for patients with nonsurgical disease or residual pulmonary hypertension despite surgical intervention. This review describes the pathophysiology, risk factors, diagnosis, and management of CTEPH.

Chronic Thromboembolic Pulmonary Hypertension: Experience from a Single Center in Mexico

INTRODUCTION

Chronic thromboembolic pulmonary hypertension (CTEPH) is characterized by precapillary pulmonary hypertension secondary to vaso-occlusive pulmonary vasculopathy and is classified as Pulmonary Hypertension Group 4. The aim of this study is to report the clinical experience of CTEPH in Mexico.

METHODS

Consecutive patients diagnosed with CTEPH were identified from the Registro de Pacientes con Hipertension Pulmonar del Instituto de Seguridad y Servicio Social de los Trabajadores del Estado (REPHPISSSTE) registry between January 2009 and February 2014. Right heart catheterization was not routinely performed prior to August 2010 in the work-up of CTEPH.

RESULTS

We identified 50 patients with CTEPH; their median age was 63 years and 58 % were female. Patients had multiple associated co-morbidities and moderate hemodynamic impairment. All patients were treated with anticoagulation. Despite surgical evaluation for pulmonary endarterectomy (PEA), only one patient underwent PEA given the lack of infrastructure for post-operative care and lack of insurance for this procedure. Most of the patients were treated with sildenafil, bosentan, or both, with increasing use of rivaroxaban and sildenafil in recent years. The overall survival of the cohort was similar to that reported in other international registries, despite the limitations of care imposed by drug availability and surgical feasibility.

CONCLUSION

This is the first report on the CTEPH experience in Mexico. It highlights the similarity of patients in the REPHPISSSTE registry to those in international registries as well as the challenges that clinicians face in a resource-limited setting.

Chronic thromboembolic pulmonary hypertension: evolution in management

PURPOSE OF REVIEW

Chronic thromboembolic pulmonary hypertension (CTEPH) is an important cause of pulmonary hypertension. Although surgery is potentially curative, some patients present with inoperable disease. In these patients, medical therapies for pulmonary arterial hypertension are increasingly being used.

RECENT FINDINGS

The pathobiology of CTEPH development remains incompletely understood; however, evidence supports both large and small vessel disorder in patients with the disease. Surgical thromboendarterectomy is an increasingly well tolerated and often curative procedure and is the management strategy of choice for most patients. Although excellent outcomes in surgical management have been noted, the role of medical management in selected patients with inoperable or recurrent or persistent disease after surgery is increasing. A recent large, randomized controlled clinical trial of riociguat in CTEPH demonstrated improvements in exercise capacity, functional class, and hemodynamics. A safe, effective angioplasty approach to CTEPH is being pursued in addition.

SUMMARY

The approach to CTEPH management in the operable patient remains surgical, without clear benefit to preoperative pulmonary arterial hypertension-specific therapy at this time. Patients with inoperable disease or pulmonary hypertension following thromboendarterectomy, however, should be considered for medical management, with riociguat currently having the strongest evidence specific to CTEPH.

Chronic thromboembolic pulmonary hypertension

Chronic thromboembolic pulmonary hypertension (CTEPH) is a form of pulmonary hypertension (PH) characterized by the persistence of thromboembolic obstructing the pulmonary arteries as an organized tissue and the presence of a variable small vessel arteriopathy. The consequence is an increase in pulmonary vascular resistance resulting in progressive right heart failure. CTEPH is classified as group IV pulmonary hypertension according to the WHO classification of pulmonary hypertension. CTEPH is defined as precapillary pulmonary hypertension (mean pulmonary artery pressure ≥ 25 mmHg with a pulmonary capillary wedge pressure ≤ 15 mmHg) associated with mismatched perfusion defects on ventilation-perfusion lung scan and signs of chronic thromboembolic disease on computed tomography pulmonary angiogram and/or conventional pulmonary angiography, in a patient who received at least 3 months of therapeutic anticoagulation. CTEPH as a direct consequence of symptomatic pulmonary embolism (PE) is rare, and a significant number of CTEPH cases develop in the absence of history of PE. Thus, CTEPH should be considered in any patient with unexplained PH. Splenectomy, chronic inflammatory conditions such as inflammatory bowel disease, indwelling catheters and cardiac pacemakers have been identified as associated conditions increasing the risk of CTEPH. Ventilation-perfusion scan (V/Q) is the best test available for establishing the thromboembolic nature of PH. When CTEPH is suspected, patients should be referred to expert centres where pulmonary angiography, right heart catheterization and high-resolution CT scan will be performed to confirm the diagnosis and to assess the operability. Pulmonary endarterectomy (PEA) remains the gold standard treatment for CTEPH when organized thrombi involve the main, lobar or segmental arteries. This operation should only be performed by experienced surgeons in specialized centres. For inoperable patients, current ESC/ERS guidelines for the diagnosis and treatment of pulmonary hypertension recommend the use of riociguat and say that off-label use of drugs approved for PAH and pulmonary angioplasty may be considered in expert centres.

Management of pulmonary arterial hypertension associated to thalassemia: when pulmonary endarterectomy is the best therapeutical option? A case report

Pulmonary arterial hypertension (PAH) has been reported with nearly all forms of the inherited as well as the acquired hemolytic anemias. Although screening studies suggested that PAH has emerged as major complication of thalassemia patients, its impact on survival is unknown; the pathophysiology of the PAH in these patients is multifactorial, and a thorough diagnostic evaluation is essential. Understanding the PAH pathogenesis, diagnostic options, prevention is critical for clinicians who care for the thalassemic patients; there are virtually no high-quality data on the safety/efficacy of PAH treatment strategy in this patient population. We are reporting the case of a thalassemic patient suffering from progressive severe PAH, not responding to medical treatment and related to chronic thromboembolic disease. After carefully considering all the options, we decided to proceed with vascular disobliteration by pulmonary endarterectomy (PEA), the first line choice in these cases. This intervention led to a significant improvement in the clinical status and in the functional parameters. Therefore, even if haemolytic anemia-associated-PAH is included in the group I of the Dana-point classification, an individualized approach is recommended as well as a particular management with disease-specific measures and a comprehensive evaluation of other causes of PAH; this current report supports the feasibility and effectiveness of PEA also in the thalassemic patients with surgically accessible chronic thromboembolic pulmonary hypertension.

Dysfibrinogenemia: from molecular anomalies to clinical manifestations and management

Congenital dysfibrinogenemia is a qualitative congenital fibrinogen disorder characterized by normal antigen levels of a dysfunctional fibrinogen. The diagnosis is usually based on discrepancies between fibrinogen activity and antigen levels, but could require more specialized techniques for the assessment of fibrinogen function, owing to some limitations in routine assays. Molecular abnormalities, which are frequently heterozygous missense mutations localized in exon 2 of FGA and exon 8 of FGG, lead to defects in one or more phases of fibrinogen to fibrin conversion, fibrin network formation, and other important functions of fibrinogen. The clinical phenotype is highly heterogeneous, from no manifestations to bleeding and/or thrombotic events. Asymptomatic propositi and relatives with the predisposing genotype are at risk of developing adverse outcomes during the natural course of the disease. Correlations between genotype and phenotype have not yet been clearly established, with the exception of some abnormal fibrinogens that severely increase the risk of thrombosis. Functional analysis of polymerization and fibrinolysis, structural studies of the fibrin network and the viscoelastic properties of fibrin clot could help to predict the phenotype of congenital dysfibrinogenemia, but have not yet been evaluated in detail. The management is essentially based on personal and family history; however, even individuals who are still asymptomatic and without a family history should be carefully assessed and monitored. Particular situations, such as pregnancy, delivery, and surgery, require a multidisciplinary approach.

Chronic thromboembolic pulmonary hypertension: a distinct disease entity

Chronic thromboembolic pulmonary hypertension (CTEPH) is a distinct subtype of pulmonary hypertension (PH). One disease hypothesis is that CTEPH results from the non-resolution of venous thromboembolism. CTEPH is characterised by the presence of obstructive fibrotic thromboembolic material in the major pulmonary vessels, with concomitant microvascular arteriopathy, resulting in progressive PH. The clinical presentation of CTEPH is similar to pulmonary arterial hypertension with nonspecific symptoms, but it is distinguished from pulmonary arterial hypertension by the presence of mismatched segmental defects on the ventilation/perfusion scan. The exact prevalence and incidence of CTEPH are unknown, but are thought to have been underestimated in the past. CTEPH is unique among the subgroups of PH in that it is potentially curable with pulmonary endarterectomy, a surgical intervention intended to remove the occlusive material from the pulmonary vasculature. However, in some patients the obstructions are technically inaccessible or the risk/benefit ratios are unfavourable, making the condition inoperable. It is thought that the involvement of the smaller, more distal vessels is a target for medical treatment. Untreated, CTEPH may result in right heart failure and death. The pathophysiological mechanisms which cause CTEPH are complex and have not yet been fully elucidated.

CTEPH is distinct from other types of pulmonary hypertension, both in terms of its pathophysiology and treatmenthttp://ow.ly/L54ag

Hypofibrinogenemia and liver disease: a new case of Aguadilla fibrinogen and review of the literature

INTRODUCTION

Fibrinogen storage disease (FSD) is characterized by hypofibrinogenemia and hepatic inclusions due to impaired release of mutant fibrinogen which accumulates and aggregates in the hepatocellular endoplasmic reticulum. Liver disease is variable.

AIM

We studied a new Swiss family with fibrinogen Aguadilla. In order to understand the molecular peculiarity of FSD mutations, fibrinogen Aguadilla and the three other causative mutations, all located in the γD domain, were modelled.

METHOD

The proband is a Swiss girl aged 4 investigated because of fatigue and elevated liver enzymes. Protein structure models were prepared using the Swiss-PdbViewer and POV-Ray software.

RESULTS

The proband was found to be heterozygous for fibrinogen Aguadilla: FGG Arg375Trp. Familial screening revealed that her mother and maternal grandmother were also affected and, in addition, respectively heterozygous and homozygous for the hereditary haemochromatosis mutation HFE C282Y. Models of backbone and side-chain interactions for fibrinogen Aguadilla in a 10-angstrom region revealed the loss of five H-bonds and the gain of one H-bond between structurally important amino acids. The structure predicted for fibrinogen Angers showed a novel helical structure in place of hole 'a' on the outer edge of γD likely to have a negative impact on fibrinogen assembly and secretion.

CONCLUSION

The mechanism by which FSD mutations generate hepatic intracellular inclusions is still not clearly established although the promotion of aberrant intermolecular strand insertions is emerging as a likely cause. Reporting new cases is essential in the light of novel opportunities of treatment offered by increasing knowledge of the degradation pathway and autophagy.

Chronic thromboembolic pulmonary arterial hypertension: a review of the literature and novel therapeutic approaches

Chronic thromboembolic pulmonary hypertension is defined as pulmonary hypertension (PH) caused by single or recurrent pulmonary emboli and is characterized by chronic obstruction of the pulmonary arteries leading to increased vascular resistance and PH. Also, progressive remodeling may occur in occluded and nonoccluded territories. Better understanding of the underlying mechanisms and risk factors could improve diagnosis and allow appropriate interventions. Pulmonary endarterectomy is an established approach and is considered the definitive treatment for chronic PH, resulting from thromboembolic disease. Furthermore, percutaneous transluminal pulmonary angioplasty is technically feasible, especially for those with peripheral-type of the disease. In addition, several agents, including prostanoids, endothelin receptor antagonists and phosphodiesterase type-5 inhibitors, have been tested in selected patients yielding promising results. Several novel agents are under investigation, and extensive research is currently in progress aiming to resolve uncertainties in the understanding and treatment of the disease.

Fibrinogen and red blood cells in venous thrombosis

Deep vein thrombosis and pulmonary embolism, collectively termed venous thromboembolism (VTE), affect over 1 million Americans each year. VTE is triggered by inflammation and blood stasis leading to the formation of thrombi rich in fibrin and red blood cells (RBCs). However, little is known about mechanisms regulating fibrin and RBC incorporation into venous thrombi, or how these components mediate thrombus size or resolution. Both elevated circulating fibrinogen (hyperfibrinogenemia) and abnormal fibrin(ogen) structure and function, including increased fibrin network density and resistance to fibrinolysis, have been observed in plasmas from patients with VTE. Abnormalities in RBC number and/or function have also been associated with VTE risk. RBC contributions to VTE are thought to stem from their effects on blood viscosity and margination of platelets to the vessel wall. More recent studies suggest RBCs also express phosphatidylserine, support thrombin generation, and decrease fibrinolysis. RBC interactions with fibrin(ogen) and cells, including platelets and endothelial cells, may also promote thrombus formation. The contributions of fibrin(ogen) and RBCs to the pathophysiology of VTE warrants further investigation.

Chronic thromboembolic pulmonary hypertension is not associated with iron overload

BACKGROUND

Chronic thromboembolic pulmonary hypertension (CTEPH) is characterized as the incomplete resolution of emboli after pulmonary embolism (PE) and the subsequent fibrotic organization and remodeling of pulmonary vascular bed. It has been reported that abnormal fibrin probably contributes to the incomplete resolution of emboli. And there is evidence that free iron could convert fibrinogen into fibrin which is remarkably resistant to lysis. Thus, we hypothesized that persistent iron overload might participate in the development of CTEPH.

MATERIALS AND METHODS

A case-control study was conducted. Forty-five CTEPH patients were enrolled as cases, and 36 age and sex frequency-matched chronic PE patients without pulmonary hypertension were selected as controls. Levels of free iron, soluble transferrin receptor (sTfR), ferritin, sTfR/ferritin ratio, hepcidin-25, tumor necrosis factor-alpha (TNF-α), interleukin (IL)-6, and malondialdehyde (MDA) were compared between the two groups. Logistic regression analysis was carried out to estimate odds ratios.

RESULTS

There was no difference of the levels of free iron, hepcidin-25, sTfR, ferritin, sTfR/ferritin ratio, TNF-α, and MDA between CTEPH patients and the controls. Levels of sTfR and ferritin in both groups were within the normal limits. Levels of IL-6 in CTEPH patients were significantly higher than that in the controls. A negative correlation was observed between hepcidin-25 and sTfR (Spearman's r=-0.438, P<.001), and a positive correlation was observed between hepcidin-25 and ferritin (Spearman's r=0.503, P<.001). In the univariate logistic regression model, there was no association observed between CTEPH and free iron, hepcidin-25, sTfR, ferritin, sTfR/ferritin ratio, TNF-α, IL-6, and MDA.

CONCLUSIONS

CTEPH has no association with iron overload. The iron status evaluated by sTfR and ferritin is within the normal limits in this CTEPH population.

Coagulation and the vessel wall in pulmonary embolism

Venous thromboembolism comprises deep-vein thrombosis, thrombus in transit, acute pulmonary embolism, and chronic thromboembolic pulmonary hypertension (CTEPH). Pulmonary thromboemboli commonly resolve, with restoration of normal pulmonary hemodynamics. When they fail to resorb, permanent occlusion of the deep veins and/or CTEPH are the consequences. Apart from endogenous fibrinolysis, venous thrombi resolve by a process of mechanical fragmentation, through organization of the thromboembolus by invasion of endothelial cells, leukocytes, and fibroblasts leading to recanalization. Recent data utilizing various models have contributed to a better understanding of venous thrombosis and the resolution process that is directed at maintaining vascular patency. This review summarizes the plasmatic and cellular components of venous thrombus formation and resolution.

Chronic thromboembolic pulmonary hypertension: time for research in pathophysiology to catch up with developments in treatment

The modern treatment era in chronic thromboembolic disease has seen significant advances in both surgical and medical treatment. One such treatment, the pulmonary endarterectomy (where established chronic organized thrombus is removed), has dramatically affected morbidity and mortality. These advances have outstripped basic research into the causes and pathophysiology of disease, which remain largely poorly understood. In this review, we will set out to explain some of the historical reasons for this, including the difficulties inherent in human studies and the lack of good animal models. We will review some of the recent advances in pathophysiology from registries and translational research, and we will summarize the treatment options, with some discussion of very recently published work, including medical and surgical treatments, both traditional and more experimental work in non-invasive techniques.

Fibrinogen plasma concentration is an independent marker of haemodynamic impairment in chronic thromboembolic pulmonary hypertension

Fibrinogen has a crucial role in both inflammation and coagulation, two processes pivotal for the pathogenesis of pulmonary hypertension. We therefore aimed to investigate whether fibrinogen plasma concentrations a) are elevated in pulmonary arterial hypertension (PAH) and chronic thromboembolic pulmonary hypertension (CTEPH) and b) may serve as a novel biomarker for haemodynamic impairment. In a dual-centre, retrospective analysis including 112 patients with PAH (n = 52), CTEPH (n = 49) and a control cohort of patients with suspected PAH ruled out by right heart catheterisation (n = 11), we found fibrinogen plasma concentrations to be increased in patients with PAH (4.1 ± 1.4 g/l) and CTEPH (4.3 ± 1.2 g/l) compared to control patients (3.4 ± 0.5 g/l, p = 0.0035 and p = 0.0004, respectively). In CTEPH patients but not in PAH patients fibrinogen was associated with haemodynamics (p < 0.036) and functional parameters (p < 0.041). Furthermore, fibrinogen was linked to disease severity (WHO functional class, p = 0.017) and independently predicted haemodynamic impairment specifically in CTEPH (p < 0.016). Therefore, fibrinogen seems to represent an important factor in CTEPH pathophysiology and may have the potential to guide clinical diagnosis and therapy.

Why acute pulmonary embolism becomes chronic thromboembolic pulmonary hypertension: clinical and genetic insights

PURPOSE OF REVIEW

Chronic thromboembolic pulmonary hypertension (CTEPH) is a life-threatening complication that affects a small but appreciable percentage of patients after acute pulmonary embolism. The cause of CTEPH is under investigation, but no single causative mechanism has yet been identified.

RECENT FINDINGS

CTEPH is likely a complication of residual thrombotic material in the pulmonary arteries that becomes transformed into intravascular scars. Pulmonary artery residua are relatively common after acute pulmonary embolism, and CTEPH may be an extreme manifestation of this phenomenon. Several intriguing observations have been made in patients with CTEPH that give insights into the mechanisms responsible for its formation. Two general pathways have been investigated: resistance of thromboemboli to lysis and attenuation of cellular processes involved in thrombus resolution. This review discusses the evidence supporting each pathway as a mechanism for CTEPH formation, as well as the interaction between the two.

SUMMARY

CTEPH may be due to a complex interaction between thrombotic/thrombolytic processes and angiogenic cellular remodeling of organized thrombi. The factors involved may, in fact, vary among CTEPH patients. An understanding of the interplay between the factors that cause CTEPH may help quantify the risk of its occurrence and provide insights into how it can be prevented.

Defective angiogenesis delays thrombus resolution: a potential pathogenetic mechanism underlying chronic thromboembolic pulmonary hypertension

OBJECTIVE

Restoration of patency is a natural target of vascular remodeling after venous thrombosis that involves vascular endothelial cells and smooth muscle cells, as well as leukocytes. Acute pulmonary emboli usually resolve <6 months. However, in some instances, thrombi transform into fibrous vascular obstructions, resulting in occlusion of the deep veins, or in chronic thromboembolic pulmonary hypertension (CTEPH). We proposed that dysregulated thrombus angiogenesis may contribute to thrombus persistence.

APPROACH AND RESULTS

Mice with an endothelial cell-specific conditional deletion of vascular endothelial growth factor receptor 2/kinase insert domain protein receptor were used in a model of stagnant flow venous thrombosis closely resembling human deep vein thrombosis. Biochemical and functional analyses were performed on pulmonary endarterectomy specimens from patients with CTEPH, a human model of nonresolving venous thromboembolism. Endothelial cell-specific deletion of kinase insert domain protein receptor and subsequent ablation of thrombus vascularization delayed thrombus resolution. In accordance with these findings, organized human CTEPH thrombi were largely devoid of vascular structures. Several vessel-specific genes, such as kinase insert domain protein receptor, vascular endothelial cadherin, and podoplanin, were expressed at lower levels in white CTEPH thrombi than in organizing deep vein thrombi and organizing thrombi from aortic aneurysms. In addition, red CTEPH thrombi attenuated the angiogenic response induced by vascular endothelial growth factor.

CONCLUSIONS

In the present work, we propose a mechanism of thrombus nonresolution demonstrating that endothelial cell-specific deletion of kinase insert domain protein receptor abates thrombus vessel formation, misguiding thrombus resolution. Medical conditions associated with the development of CTEPH may be compromising early thrombus angiogenesis.

Comparison of gene expression profiles and related pathways in chronic thromboembolic pulmonary hypertension

Chronic thromboembolic pulmonary hypertension (CTEPH) is one of the main causes of severe pulmonary hypertension. However, despite treatment (pulmonary endarterectomy), in approximately 15–20% of patients, pulmonary vascular resistance and pulmonary arterial pressure continue to increase. To date, little is known about the changes that occur in gene expression in CTEPH. The identification of genes associated with CTEPH may provide insight into the pathogenesis of CTEPH and may aid in diagnosis and treatment. In this study, we analyzed the gene expresion profiles of pulmonary artery endothelial cells from 5 patients with CTEPH and 5 healthy controls using oligonucleotide microarrays. Bioinformatics analyses using the Gene Ontology (GO) and KEGG databases were carried out to identify the genes and pathways specifically associated with CTEPH. Signal transduction networks were established to identify the core genes regulating the progression of CTEPH. A number of genes were found to be differentially expressed in the pulmonary artery endothelial cells from patients with CTEPH. In total, 412 GO terms and 113 pathways were found to be associated with our list of genes. All differential gene interactions in the Signal-Net network were analyzed. JAK3, GNA15, MAPK13, ARRB2 and F2R were the most significantly altered. Bioinformatics analysis may help gather and analyze large amounts of data in microarrays by means of rigorous experimental planning, scientific statistical analysis and the collection of complete data. In this study, a novel differential gene expression pattern was constructed. However, further studies are required to identify novel targets for the diagnosis and treatment of CTEPH.

MetAmyl: a METa-predictor for AMYLoid proteins

The aggregation of proteins or peptides in amyloid fibrils is associated with a number of clinical disorders, including Alzheimer's, Huntington's and prion diseases, medullary thyroid cancer, renal and cardiac amyloidosis. Despite extensive studies, the molecular mechanisms underlying the initiation of fibril formation remain largely unknown. Several lines of evidence revealed that short amino-acid segments (hot spots), located in amyloid precursor proteins act as seeds for fibril elongation. Therefore, hot spots are potential targets for diagnostic/therapeutic applications, and a current challenge in bioinformatics is the development of methods to accurately predict hot spots from protein sequences. In this paper, we combined existing methods into a meta-predictor for hot spots prediction, called MetAmyl for METapredictor for AMYLoid proteins. MetAmyl is based on a logistic regression model that aims at weighting predictions from a set of popular algorithms, statistically selected as being the most informative and complementary predictors. We evaluated the performances of MetAmyl through a large scale comparative study based on three independent datasets and thus demonstrated its ability to differentiate between amyloidogenic and non-amyloidogenic polypeptides. Compared to 9 other methods, MetAmyl provides significant improvement in prediction on studied datasets. We further show that MetAmyl is efficient to highlight the effect of point mutations involved in human amyloidosis, so we suggest this program should be a useful complementary tool for the diagnosis of these diseases.

Chronic thromboembolic pulmonary hypertension

Chronic thromboembolic pulmonary hypertension (CTEPH) is a disease with high mortality and few treatment options. This article reviews the epidemiology of CTEPH and identifies risk factors for its development. The pathobiology and the progression from thromboembolic events to chronically increased right-sided pressures are discussed. The diagnosis and assessment of CTEPH requires several modalities and the role of these is detailed. The pre-operative evaluation assesses peri-operative risk and determines the likelihood of benefit from PTE. Pulmonary thromboendarterectomy (PTE) remains the treatment of choice in appropriate patients. Nonsurgical therapies for CTEPH may provide benefit in patients who cannot be offered surgery.

Structural insights into fibrinogen dynamics using amide hydrogen/deuterium exchange mass spectrometry

We determined the amide hydrogen/deuterium exchange profile of native human fibrinogen under physiologic conditions. After optimization of the quench and proteolysis conditions, more than 1,200 peptides were identified by mass spectrometry, spanning more than 90% of the constituent Aα, Bβ, and γ chain amino acid sequences. The compact central and distal globular regions of fibrinogen were well protected from deuterium exchange, with the exception of the unfolded amino-terminal segments of the Aα and Bβ chains extending from the central region, and the short γ chain "tail" extending from each distal globular region. The triple-helical coiled-coil regions, which bridge the central region to each distal region, were also well protected with the exception of a moderately fast-exchanging area in the middle of each coiled-coil adjacent to the γ chain carbohydrate attachment site. These dynamic regions appear to provide flexibility to the fibrinogen molecule. The γ chain "out loop" contained within each coiled-coil also exchanged rapidly. The αC domain (Aα 392-610) exchanged rapidly, with the exception of a short segment sandwiched between a conserved disulfide linkage in the N-terminal αC subdomain. This latter finding is consistent with a mostly disordered structure for the αC domain in native fibrinogen. Analysis of the dysfibrinogen Bβ 235 Pro/Leu, which exhibits abnormal fibrin structure, revealed enhanced deuterium exchange surrounding the Pro/Leu substitution site as well as in the vicinity of the high affinity calcium binding site and the A knob polymerization pocket within the γC domain. The implication of these changes with respect to fibrin structure is discussed.

Clinical phenotype, laboratory features and genotype of 35 patients with heritable dysfibrinogenaemia

Heritable dysfibrinogenaemia (HD) is a rare qualitative disorder of fibrinogen (FGN). To better describe the clinical, laboratory and genotypic spectrum of HD, we evaluated 35 subjects identified at two UK centres using laboratory criteria. 12/35(34%) subjects with HD experienced bleeding (bleeding score >1 at any site), 3/35(9%) thrombosis and 20/35(57%) were asymptomatic. Amongst subjects with bleeding, symptoms were typically mild, at one anatomical site and seldom occurred after invasive procedures. All subject showed dry clot weight within or above laboratory reference interval (median 3·2 g/l; range 1·9-5·1), reduced Clauss fibrinogen (median 0·52 g/l; range 0·21-1·3), and prolonged thrombin (median 30·7 s; range 21·3-45·7) and reptilase (median 42·0 s; range 20·0-68·0) times. In all subjects, the prothrombin time ratio (PTR), determined by Sysmex CA-1500 coagulometer and Innovin activator, was abnormal (median 1·42; range 1·22-1·61). The activated partial thromboplastin time ratio and PTR with other coagulometers and activators were comparatively insensitive to HD. All subjects with HD harboured heterozygous candidate nucleotide variations within known hotspots in the FGN genes. The HD variants identified in this cross-sectional study seldom have significant clinical manifestations and show similar laboratory features irrespective of genotype. Selection of coagulometer and PT activator may markedly affect the detection of new HD cases using coagulation screening tests.

Natural history of venous thromboembolism

Venous thromboembolism (VTE) originates in systemic venous thrombosis and has different etiological mechanisms and natural history from arterial thrombosis. VTE typically originates as deep venous thrombosis in a lower extremity, where it may give rise to acute symptoms “upstream” from the obstructed vein, result in pulmonary embolism, and/or cause chronic venous obstruction. Pulmonary embolism may result in acute respiratory symptoms, cardiovascular collapse and, uncommonly, may also cause chronic disease.

Diagnostic evaluation and management of chronic thromboembolic pulmonary hypertension: a clinical practice guideline

BACKGROUND

Pulmonary embolism is a common condition. Some patients subsequently develop chronic thromboembolic pulmonary hypertension (CTEPH). Many care gaps exist in the diagnosis and management of CTEPH patients including lack of awareness, incomplete diagnostic assessment, and inconsistent use of surgical and medical therapies.

METHODS

A representative interdisciplinary panel of medical experts undertook a formal clinical practice guideline development process. A total of 20 key clinical issues were defined according to the patient population, intervention, comparator, outcome (PICO) approach. The panel performed an evidence-based, systematic, literature review, assessed and graded the relevant evidence, and made 26 recommendations.

RESULTS

Asymptomatic patients postpulmonary embolism should not be screened for CTEPH. In patients with pulmonary hypertension, the possibility of CTEPH should be routinely evaluated with initial ventilation/perfusion lung scanning, not computed tomography angiography. Pulmonary endarterectomy surgery is the treatment of choice in patients with surgically accessible CTEPH, and may also be effective in CTEPH patients with disease in more 'distal' pulmonary arteries. The anatomical extent of CTEPH for surgical pulmonary endarterectomy is best assessed by contrast pulmonary angiography, although positive computed tomography angiography may be acceptable. Novel medications indicated for the treatment of pulmonary hypertension may be effective for selected CTEPH patients.

CONCLUSIONS

The present guideline requires formal dissemination to relevant target user groups, the development of tools for implementation into routine clinical practice and formal evaluation of the impact of the guideline on the quality of care of CTEPH patients. Moreover, the guideline will be updated periodically to reflect new evidence or clinical approaches.

Evaluation and management of chronic pulmonary thromboembolic disease

Pulmonary embolism (PE) is common and the majority of patients survive the acute event. Survivors are at increased risk for adverse outcomes, including persistent thrombi, recurrent embolism, chronic thromboembolic pulmonary hypertension (CTEPH), and death. Anticoagulation protects against recurrence, which has a high mortality rate. The recommended duration of anticoagulation for patients with reversible PE risk factors is 3 months. For patients with idiopathic PE or persistent risk factors, extended duration of anticoagulation is preferred, balanced with an individual patient's risk of hemorrhage, which in itself is a major cause of morbidity and mortality. Among patients with malignancy who develop venous thromboembolism (VTE), low-molecular-weight heparin is preferred over oral vitamin K antagonists in the first 6 months. Thereafter, anticoagulation should be continued indefinitely with either low-molecular-weight heparin or oral vitamin K antagonists. Inferior vena cava filters are not routinely recommended and should only be used in patients who have a contraindication to anticoagulation. Patients who have had VTE and with persistent or recurrent dyspnea should be evaluated for recurrence of VTE or development of CTEPH. Patients with recurrent VTE should be anticoagulated indefinitely. Routine screening for CTEPH in asymptomatic patients is not recommended. Echocardiography often provides the first indication of the presence of pulmonary hypertension. Once presence of CTEPH is established by right-sided heart catheterization and perfusion imaging (ie, ventilation/perfusion scintigraphy, computed tomography angiography, or pulmonary angiography), patients should be referred early to a center with expertise, as it is potentially surgically curable by pulmonary endarterectomy. Those who are deemed inoperable after being evaluated may gain symptomatic benefit from drugs approved for idiopathic pulmonary arterial hypertension. Lung transplantation may also be an option for patients who are not candidates for pulmonary endarterectomy.

Characterization of myofibroblasts in chronic thromboembolic pulmonary hypertension

BACKGROUND

It has been generally accepted that chronic thromboembolic pulmonary hypertension (CTEPH) results from pulmonary embolism arising from deep vein thrombosis. An unresolved question regarding the etiology of CTEPH is why pulmonary thromboemboli are stable and resistant to effective anticoagulation. Recently non-resolving pulmonary thromboemboli in CTEPH have been shown to include myofibroblasts. This study investigates the cellular characteristics of myofibroblasts included in the organized thrombotic tissues of CTEPH.

METHODS

Organized thrombotic tissues of patients with CTEPH were obtained following pulmonary endarterectomy. We isolated cells from endarterectomized tissue from patients with CTEPH and identified them as endothelial-like cells and myofibroblast-like cells.

RESULTS

Myofibroblast-like cells were characterized as hyperproliferative, anchorage-independent, invasive and serum-independent.

CONCLUSIONS

Here we report the presence of active myofibroblast-like cells in endarterectomized tissue of CTEPH. We suggest that the formation of myofibroblasts with a high growth potential in the organized thrombotic tissues may be an important event in the pathobiology of this disease.