Thrombotic lesions in primary plexogenic arteriopathy. Similar pathogenesis or complication?

Nets, pulmonary arterial hypertension, and thrombo-inflammation

Pulmonary arterial hypertension (PAH) is a progressive and fatal vascular disease in which high blood pressure in the pulmonary artery and remodeling of the pulmonary vasculature ensues. This disorder is characterized by the presence of thrombotic lesions, resulting from chronic platelet, coagulation factors, and endothelium activation, which translate into platelet aggregation, vasoconstriction, and medial thickening. Neutrophil extracellular traps (NETs), a network of chromatin and cytoplasmatic enzymes (myeloperoxidase and neutrophil elastase) forming after neutrophil programmed cell death, were described in multiple cardiovascular diseases as thrombotic mediators, by creating a scaffold or by surface receptor interaction. In this review, we analyze the possible involvement of NETs in PAH, to enlighten future studies to explore this hypothesis. NETs may have a determining role in pulmonary hypertension through activation of platelets and endothelial cells. Simultaneously, NETosis may be induced by endothelial signaling and/or cell-cell interaction between platelets and primed neutrophils, creating a positive feedback loop. Confirming its role in the pathophysiology and prognosis of PAH may represent a new opportunity to explore new therapeutic options. KEY MESSAGES: Thrombosis and innate immunity are relevant axes in PAH. Patients with PAH display elevated levels of NETs. NETs could activate platelets/endothelium with proliferative and thrombotic effects. Activated platelets and endothelium could contribute to NETosis. NETs could open new therapy research avenues.

Platelets, extracellular vesicles and coagulation in pulmonary arterial hypertension

Pulmonary arterial hypertension is a rare disease of the pulmonary vasculature, characterised pathologically by proliferation, remodelling and thrombosis in situ. Unfortunately, existing therapeutic interventions do not reverse these findings and the disease continues to result in significant morbidity and premature mortality. A number of haematological derangements have been described in pulmonary arterial hypertension which may provide insights into the pathobiology of the disease and opportunities to explore new therapeutic pathways. These include quantitative and qualitative platelet abnormalities, such as thrombocytopaenia, increased mean platelet volume and altered platelet bioenergetics. Furthermore, a hypercoagulable state and aberrant negative regulatory pathways can be observed, which could contribute to thrombosis in situ in distal pulmonary arteries and arterioles. Finally, there is increasing interest in the role of extracellular vesicle autocrine and paracrine signalling in pulmonary arterial hypertension, and their potential utility as biomarkers and novel therapeutic targets. This review focuses on the potential role of platelets, extracellular vesicles and coagulation pathways in the pathobiology of pulmonary arterial hypertension. We highlight important unanswered clinical questions and the implications of these observations for future research and pulmonary arterial hypertension-directed therapies.

Hypercoagulability in Pulmonary Hypertension

Pulmonary hypertension (PH) is divided into varied pathophysiological and etiologic groupings, as classified by the World Health Organization (WHO). Pulmonary arterial hypertension (PAH), which falls under WHO group 1 PH, is a progressive and potentially fatal disease characterized by a vasoconstrictive, proliferative, and thrombotic phenotype, which leads to increased pulmonary artery pressure, right heart failure, and death. Pathologically, in situ thromboses are found in the small distal pulmonary arteries. Dysregulation of coagulation, platelet function, and endothelial cells may contribute to a prothrombotic state. There is mixed evidence for the use of anticoagulation or antiplatelet therapy in PAH patients.

New insights into the recognition, classification and management of systemic sclerosis-associated pulmonary hypertension

PURPOSE OF REVIEW

Pulmonary hypertension is a common complication of systemic sclerosis (SSc), and remains a leading cause of morbidity and mortality. We will review recent developments in the recognition, classification and treatment of pulmonary hypertension in SSc.

RECENT FINDINGS

Advances in screening for pulmonary arterial hypertension (PAH) and use of exercise haemodynamics may help to identify pulmonary vascular disease earlier in SSc. Recent studies have led to changes in recommendations for adjunct therapy and selection of pulmonary vasodilators for the treatment of SSc-associated PAH.

SUMMARY

Recent advances in the diagnosis, classification and management of pulmonary hypertension in SSc have continued to improve our understanding of this challenging disease. Ongoing investigation in the pathogenesis of this disease will afford the opportunity to develop targeted therapies to improve outcomes for SSc patients with pulmonary hypertension.

Current Approach to the Diagnosis and Management of Portopulmonary Hypertension

Portopulmonary hypertension (POPH) is a form of pulmonary arterial hypertension occurring in the setting of portal hypertension with or without hepatic cirrhosis. The presence of both portal and pulmonary vascular disease contributes to complicated hemodynamics and therapeutic challenges, though the severities do not appear to correlate directly. Diagnosis of POPH, and distinction from the commonly observed hyperdynamic state of end-stage liver disease, is typically accomplished with an initial screening transthoracic echocardiogram, followed by right heart catheterization for confirmation of hemodynamic parameters. Though few studies have directly evaluated use in POPH, pulmonary artery-directed therapy is the cornerstone of management, along with consideration of liver transplantation. Perioperative and long-term outcomes are variable, but uniformly worse in the setting of uncontrolled pulmonary pressures. Risk stratification and optimal patient selection for these interventions are areas of ongoing investigation.

Portuguese validation of the Cambridge pulmonary hypertension outcome review (CAMPHOR) questionnaire

BACKGROUND

Patients with pulmonary arterial hypertension (PAH) and other forms of precapillary pulmonary hypertension (PH) have impaired quality of life (QoL). The Cambridge Pulmonary Hypertension Outcome Review (CAMPHOR) is a PH-specific patient-reported outcome measure that assesses symptoms, activity limitations and QoL. It was originally developed in UK-English. The main objective of this study was to create an adaptation of the CAMPHOR suitable for a Portuguese-speaking population.

METHODS

A multi-step approach was followed: bilingual and lay panel translation; cognitive debriefing interviews; and psychometric testing in repeated postal surveys (2 weeks apart) including assessment of internal consistency, reproducibility and validity. The Nottingham Health Profile (NHP) questionnaire was used as a comparator instrument to test convergent validity.

RESULTS

The CAMPHOR was translated without difficulty by the two panels. Cognitive debriefing interviews showed the questionnaire was easily understood and considered relevant to patients' experience with their illness. Psychometric evaluation was performed with 50 PAH patients (47 ± 14 years, 37 women). Cronbach's alpha coefficients showed good internal consistency for the three CAMPHOR scales [Symptoms = 0.95; Activities = 0.93 and QoL = 0.94]. Test-retest coefficients showed that all scales had excellent reliability (Symptoms = 0.94; Activities = 0.89 and QoL = 0.93), indicating low levels of random measurement error. The CAMPHOR correlated as expected with the NHP. The magnitude of correlations followed a similar pattern to those in the original development study. The CAMPHOR also exhibited evidence of known group validity in its ability to distinguish between self-reported severity and general health groups.

CONCLUSIONS

A valid and reliable version of the CAMPHOR questionnaire for the European Portuguese-speaking population was developed and is recommended for use.

Age-Dependent Likelihood of In Situ Thrombosis in Secondary Pulmonary Hypertension

Pulmonary arterial thrombosis (PAT) may complicate the clinical course of pulmonary hypertension associated with congenital heart disease (so-called Eisenmenger syndrome, ES). In this study, variables were sought that could represent risk factors for the occurrence of this complication. Twenty patients aged 11 to 53 (median, 33) years were studied. The presence of PAT (spiral computed tomography angiography) was correlated with age, gender group, PAP, hematocrit, peripheral oxygen saturation (SpO2), and plasma levels of endothelial and coagulation dysfunction markers: von Willebrand factor antigen (vWF: Ag), tissue plasminogen activator (t-PA), and D-dimer (enzyme immunoassay). Patients were classified according to the presence (group 1, N=7), or absence (group 2, N=13) of PAT. Group 1 patients were older (42±8 vs. 27±10 years in group 2, p=0.0051), had lower SpO2 (82±7% vs. 89±6% in group 2, p=0.0462) and increased D-dimer levels (637 vs. 149 ng/mL in group 2, median values, p=0.0235). A trend was observed toward an increase in vWF: Ag (125±29 vs. 103±18 U/dL in group 2, p=0.0789) and t-PA (15.7 vs. 9.4 ng/mL in group 2, median values, p=0.0689). Age was the main variable influencing the occurrence of PAT in multivariate analysis (p=0.0026), with odds ratio of 1.204 per year. The age of 35 years was 86% sensitive and 85% specific for occurrence of PAT. Age correlated positively with t-PA (r=0.57, p=0.0111). Thus, PAT is highly prevalent in ES as an age-dependent event, probably associated with endothelial dysfunction. Prophylactic anticoagulation should be considered before the age of 30 years, in particular in subjects with low SpO2 and increased D-dimer levels.

15-Lipoxygenase and 15-hydroxyeicosatetraenoic acid regulate intravascular thrombosis in pulmonary hypertension

Pulmonary arterial hypertension (PAH) is a disease characterized by thickening of pulmonary artery walls, elevated pulmonary vascular resistance, pulmonary vascular thrombotic lesions, and right heart failure. Recent studies suggest that 15-lipoxygenase (15-LO)/15-hydroxyeicosatetraenoic acid (15-HETE) play an important role in PAH, acting on arterial walls. Here, we show evidence for the action of the 15-LO/15-HETE signaling in the pulmonary vascular thrombotic lesions in the experimental PAH models. Platelet deposition was augmented in rats exposed to hypoxia and Sugen 5416, which were both prevented by nordihydroguaiaretic acid (NDGA), a 15-LO inhibitor. Chronic hypoxic resulted in the platelet deposition specifically in pulmonary vasculature, which was reversed by 15-LO inhibitor. The 15-LO pathway mediated in the endothelial dysfunction induced by hypoxia in vivo. Meanwhile, 15-HETE positively regulated the generation of IL-6 and monocyte chemoattractant protein-1 (MCP-1). The coagulation and platelet activation induced by hypoxia were reversed by 15-LO inhibitor NDGA or the MCP-1 inhibitor synthesis inhibitor bindarit in rats. The 15-LO/15-HETE signaling promoted the coagulation and platelet activation, which was suppressed by MCP-1 inhibition. These results therefore suggest that 15-LO/15-HETE signaling plays a role in platelet activation and pulmonary vascular thrombosis in PAH, involving MCP-1.

Current clinical management of pulmonary arterial hypertension

During the past 2 decades, there has been a tremendous evolution in the evaluation and care of patients with pulmonary arterial hypertension (PAH). The introduction of targeted PAH therapy consisting of prostacyclin and its analogs, endothelin antagonists, phosphodiesterase-5 inhibitors, and now a soluble guanylate cyclase activator have increased therapeutic options and potentially reduced morbidity and mortality; yet, none of the current therapies have been curative. Current clinical management of PAH has become more complex given the focus on early diagnosis, an increased number of available therapeutics within each mechanistic class, and the emergence of clinically challenging scenarios such as perioperative care. Efforts to standardize the clinical care of patients with PAH have led to the formation of multidisciplinary PAH tertiary care programs that strive to offer medical care based on peer-reviewed evidence-based, and expert consensus guidelines. Furthermore, these tertiary PAH centers often support clinical and basic science research programs to gain novel insights into the pathogenesis of PAH with the goal to improve the clinical management of this devastating disease. In this article, we discuss the clinical approach and management of PAH from the perspective of a single US-based academic institution. We provide an overview of currently available clinical guidelines and offer some insight into how we approach current controversies in clinical management of certain patient subsets. We conclude with an overview of our program structure and a perspective on research and the role of a tertiary PAH center in contributing new knowledge to the field.

Anticoagulation in pulmonary arterial hypertension: Contemporary data from COMPERA registry

The use of anticoagulant therapy in patients with pulmonary arterial hypertension (PAH) has been controversial for decades. Recommendations for anticoagulation in these patients are often derived from small, retrospective, and single centre studies without any placebo-controlled randomized study. Furthermore, uncertainties exist regarding a number of issues such as patient selection, risk stratification for bleeding, the intensity of anticoagulation, appropriateness of anticoagulation in different types of PAH, and the potential use of new oral anticoagulants.

Recently, the database of the Comparative, Prospective Registry of Newly Initiated Therapies for Pulmonary Hypertension (COMPERA) has been analyzed to assess the effect of anticoagulation on the long-term outcome of patients with various forms of PAH. This analysis is the largest to date to assess anticoagulant therapy in PAH patients in a prospective design with long observation period. The results of COMPERA lend support to current recommendations for the use of anticoagulant therapy in patients with idiopathic PAH, but not in other forms of PAH. Also, the study confirmed the previously reported concern that anticoagulant therapy may be harmful in patients with scleroderma-associated PAH.

Physiologic and molecular consequences of endothelial Bmpr2 mutation

Background

Pulmonary arterial hypertension (PAH) is thought to be driven by dysfunction of pulmonary vascular microendothelial cells (PMVEC). Most hereditary PAH is associated with BMPR2 mutations. However, the physiologic and molecular consequences of expression of BMPR2 mutations in PMVEC are unknown.

Methods

In vivo experiments were performed on adult mice with conditional endothelial-specific expression of the truncation mutation Bmpr2^delx4+, with age-matched transactivator-only mice as controls. Phenotype was assessed by RVSP, counts of muscularized vessels and proliferating cells, and staining for thromboses, inflammatory cells, and apoptotic cells. The effects of BMPR2 knockdown in PMVEC by siRNA on rates of apoptosis were assessed. Affymetrix expression arrays were performed on PMVEC isolated and cultured from triple transgenic mice carrying the immortomouse gene, a transactivator, and either control, Bmpr2^delx4+ or Bmpr2^R899X mutation.

Results

Transgenic mice showed increased RVSP and corresponding muscularization of small vessels, with histologic alterations including thrombosis, increased inflammatory cells, increased proliferating cells, and a moderate increase in apoptotic cells. Expression arrays showed alterations in specific pathways consistent with the histologic changes. Bmpr2^delx4+ and Bmpr2^R899X mutations resulted in very similar alterations in proliferation, apoptosis, metabolism, and adhesion; Bmpr2^delx4+ cells showed upregulation of platelet adhesion genes and cytokines not seen in Bmpr2^R899X PMVEC. Bmpr2 mutation in PMVEC does not cause a loss of differentiation markers as was seen with Bmpr2 mutation in smooth muscle cells.

Conclusions

Bmpr2 mutation in PMVEC in vivo may drive PAH through multiple, potentially independent, downstream mechanisms, including proliferation, apoptosis, inflammation, and thrombosis.

A dosing/cross-development study of the multikinase inhibitor sorafenib in patients with pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) and cancer share elements of pathophysiology. This provides an opportunity for the cross-development of anticancer agents that can be used in improving PAH care. The adaptation of new drugs across these disease populations warrants a structured approach. This study was a 16-week, phase Ib, single-center, open-label trial of the multikinase/angiogenesis inhibitor sorafenib. In order to assess the safety of sorafenib in PAH, patients with advanced but stable disease on parenteral prostanoids (with or without oral sildenafil) were initiated on treatment at the lowest active dosage administered to cancer patients: 200 mg daily. Patients underwent weekly clinical evaluations and monthly functional testing and dose escalations to a final dosage of 400 mg twice daily. Among 12 patients (10 of them women), sorafenib was well tolerated at 200 mg twice daily. The most common adverse events were moderate skin reactions on the hands and feet and alopecia. Our conclusion was therefore that this is a tolerable dosing regimen for testing the therapeutic activity of sorafenib in PAH patients.

Tissue factor pathway inhibitor overexpression inhibits hypoxia-induced pulmonary hypertension

Pulmonary hypertension (PH) is a commonly recognized complication of chronic respiratory disease. Enhanced vasoconstriction, pulmonary vascular remodeling, and in situ thrombosis contribute to the increased pulmonary vascular resistance observed in PH associated with hypoxic lung disease. The tissue factor pathway regulates fibrin deposition in response to acute and chronic vascular injury. We hypothesized that inhibition of the tissue factor pathway would result in attenuation of pathophysiologic parameters typically associated with hypoxia-induced PH. We tested this hypothesis using a chronic hypoxia-induced murine model of PH using mice that overexpress tissue factor pathway inhibitor (TFPI) via the smooth muscle-specific promoter SM22 (TFPI(SM22)). TFPI(SM22) mice have increased pulmonary TFPI expression compared with wild-type (WT) mice. In WT mice, exposure to chronic hypoxia (28 d at 10% O(2)) resulted in increased systolic right ventricular and mean pulmonary arterial pressures, changes that were significantly reduced in TFPI(SM22) mice. Chronic hypoxia also resulted in significant pulmonary vascular muscularization in WT mice, which was significantly reduced in TFPI(SM22) mice. Given the pleiotropic effects of TFPI, autocrine and paracrine mechanisms for these hemodynamic effects were considered. TFPI(SM22) mice had less pulmonary fibrin deposition than WT mice at 3 days after exposure to hypoxia, which is consistent with the antithrombotic effects of TFPI. Additionally, TFPI(SM22) mice had a significant reduction in the number of proliferating (proliferating cell nuclear antigen positive) pulmonary vascular smooth muscle cells compared with WT mice, which is consistent with in vitro findings. These findings demonstrate that overexpression of TFPI results in improved hemodynamic performance and reduced pulmonary vascular remodeling in a murine model of hypoxia-induced PH. This improvement is in part due to the autocrine and paracrine effects of TFPI overexpression.

Liver transplantation for pulmonary vascular complications of pediatric end-stage liver disease

PURPOSE

Hepatopulmonary syndrome (HPS) and portopulmonary hypertension (PPH) are poorly understood pulmonary complications of end-stage liver disease (ESLD). We present a case series of children with HPS and PPH.

METHODS

After institutional review board approval, query of our medical database identified children 0 to 18 years of age with ESLD diagnosed with HPS or PPH. Data were collected via chart review.

RESULTS

We identified 7 children with either HPS (n = 5) or PPH (n = 2). Patients with HPS presented with progressive dyspnea over a mean of 7 months (range, 4-12 months) at a mean of 13 years (range, 5-17 years) of age. Pulmonary shunting by albumin perfusion scan averaged 41% (range, 20%-66%) with an initial mean resting SpO(2) of 88% (range, 84%-94%) and mean SpO(2) during exertion of 79% (range, 60%-89%). Four patients required supplemental O(2) and, upon United Network for Organ Sharing (UNOS) appeal, received pediatric model for ESLD (or Child-Pugh) score exceptions, enabling them to undergo orthotopic liver transplant (OLT) within 1-2 months. The fifth patient was initially rejected by the UNOS regional review board, but 6 months of worsening hypoxemia led to OLT 2 months after successful UNOS appeal. All patients with HPS undergoing OLT experienced complete resolution of hypoxemia within 8 months. Both children with PPH were treated with intravenous epoprostenol, which lowered or stabilized mean pulmonary artery pressure and bridged them to OLT within 7 months of listing. Overall, there were no pulmonary complications; however, 1 patient with PPH expired shortly after OLT. The remaining patients are alive at a median follow-up of 27 months (range, 6-96 months).

CONCLUSION

Hepatopulmonary syndrome and PPH are uncommon complications of ESLD in children. Epoprostenol can bridge PPH patients to OLT. OLT leads to rapid resolution of HPS and PPH and currently represents the only successful treatment for these children.

Portopulmonary hypertension

As a result of the success of orthotopic liver transplantation, there has been increasing interest in the diagnosis and therapeutic options for the pulmonary vascular complications of hepatic disease. These pulmonary vascular complications range from the hepatopulmonary syndrome, which is characterized by intrapulmonary vascular dilatations, to portopulmonary hypertension (POPH), which is characterized by an elevated pulmonary vascular resistance as a consequence of obstruction to pulmonary arterial blood flow. This review concentrates on POPH.

Portopulmonary hypertension

Portopulmonary hypertension is a common condition in patients who have portal hypertension. This article reviews the definition and clinical presentation of this disorder and outlines our current understanding of its pathophysiology. A diagnostic approach is provided , and novel medical therapies that are being investigated to treat this condition are discussed. Finally, the safety of liver transplantation in patients who have portopulmonary hypertension is reviewed.

[Pulmonary hypertension associated with disorders of the respiratory system]

Pulmonary hypertension associated with disorders of the respiratory system is defined by a pulmonary artery mean pressure above 20 mmHg at rest in stable disease. The most frequent form of precapillary pulmonary hypertension is associated with chronic obstructive pulmonary disease, because of its high prevalence. Pulmonary vascular remodeling occurs in the small pulmonary arteries and is due mainly to chronic alveolar hypoxia. Pulmonary hypertension associated with disorders of the respiratory system is usually mild to moderate, with resting pulmonary artery mean pressure ranging between 20 and 35 mm Hg. It may increase markedly during sleep, exercise or exacerbation of respiratory failure, however. Abrupt postload elevation can lead to right heart failure, an indisputable indicator of prognosis. Because the symptoms of pulmonary hypertension are minimal relative to those of the chronic hypoxic lung disease, noninvasive diagnosis is difficult, particularly in patients with chronic obstructive pulmonary disease. Oxygen therapy (at least 16 h/day) is currently the best treatment for this type of pulmonary arterial hypertension.

Systemic collateral supply in patients with chronic thromboembolic and primary pulmonary hypertension: assessment with multi-detector row helical CT angiography

PURPOSE

To compare retrospectively the frequency of systemic collateral supply in patients who have chronic thromboembolic pulmonary hypertension with the frequency of systemic collateral supply in patients who have primary pulmonary hypertension by using multi-detector row helical computed tomographic (CT) angiography.

MATERIALS AND METHODS

For this review, neither institutional board approval nor informed consent was required. Thirty-six consecutive patients, including 22 patients (four men, 18 women; mean age, 46.0 years) with chronic thromboembolic pulmonary hypertension (group 1) and 14 patients (five men, nine women; mean age, 63.0 years) with primary pulmonary hypertension (group 2), underwent multisection spiral CT angiography of the pulmonary and systemic circulations with a four- (n = 17) or 16- (n = 19) detector row scanner. CT angiograms were assessed for the presence of abnormal bronchial and/or nonbronchial systemic arteries, CT features of pulmonary hypertension, and right ventricular dysfunction. Vascular and parenchymal signs of chronic pulmonary embolism were specifically analyzed on CT angiograms of group 1 patients. Comparative analyses were performed by using the chi(2) or the Fisher exact test for categoric data. An unpaired bilateral Wilcoxon rank sum test was used for continuous data. A chi(2) goodness-of-fit test was used to compare observed proportions with equal proportions.

RESULTS

The degree of pulmonary hypertension was comparable in groups 1 and 2. Abnormally enlarged systemic arteries were identified in 16 (73%) of 22 patients from group 1 and in two (14%) of 14 patients from group 2 (P = .002). The systemic collateral supply in group 1 comprised enlargement of both bronchial and nonbronchial systemic arteries in nine (56%) of the 16 patients; the remaining seven patients had an exclusive enlargement of bronchial systemic arteries (n = 6, 38%) or nonbronchial (n = 1, 6%) systemic arteries. A total of 31 enlarged nonbronchial systemic arteries were depicted, including 13 inferior phrenic arteries, 10 intercostal arteries, seven internal mammary arteries, and one lateral thoracic artery. The mean +/- standard deviation of abnormal nonbronchial systemic arteries per patient was 1.4 +/- 1.9. No relationship was found between the mean number of abnormally enlarged nonbronchial systemic arteries and the CT angiographic features of chronic pulmonary embolism.

CONCLUSION

These results demonstrate the higher frequency of abnormally enlarged bronchial and nonbronchial systemic arteries in patients who have chronic thromboembolic pulmonary hypertension compared with patients who have primary pulmonary hypertension; this finding could help distinguish these two entities on CT angiograms.

Significance of a plasma D-dimer test in patients with primary pulmonary hypertension

BACKGROUND

D-dimer, a degradation product of fibrin, has been increasingly used as a marker or prognostic factor in various thrombotic diseases.

OBJECTIVE

To assess the significance of a d-dimer test in patients with primary pulmonary hypertension (PPH).

PATIENTS AND METHODS

Fourteen patients with PPH (12 women and 2 men) aged 25 to 68 years (mean +/- SD age, 50 +/- 14 years) entered the study. Plasma d-dimer was determined by Miniquant assay (Biopool International; Venture, CA) 3 +/- 5 months after the disease onset, and patients were followed up for 1 year. We compared the d-dimer levels to the demographic, clinical, and hemodynamic data of the patients.

RESULTS

D-dimer levels were positively correlated with New York Heart Association classification (r = 0.59, p = 0.01) and pulmonary artery pressure (r = 0.43, p = 0.03) and were negatively correlated with oxygen saturation (r = - 0.45, p = 0.03) and 6-min walk distance (r = - 0.49, p = 0.04). One-year survival was also negatively correlated with d-dimer (point-biserial r = - 0.71, p = 0.004), with a higher d-dimer value associated with poorer survival. No significant correlations were found between d-dimer values and sex, age, diffusing capacity of the lung for carbon monoxide, or cardiac index.

CONCLUSION

D-dimer levels may have a role in the evaluation of patients with PPH. This simple, noninvasive test may be helpful for identifying patients who are at a higher risk for severe disease.

Microsatellite instability of endothelial cell growth and apoptosis genes within plexiform lesions in primary pulmonary hypertension

Primary pulmonary hypertension (PPH) is a frequently fatal disease whose pathobiology is poorly understood. Monoclonal endothelial cell growth is present within plexiform lesions of patients with PPH but not secondary PH because of congenital heart malformations. We hypothesized that endothelial cells within PPH plexiform lesions harbor mutations permissive for clonal cell growth. We found that endothelial cells in PPH plexiform lesions demonstrated microsatellite instability within the human MutS Homolog 2 gene (10 of 20 lesions) and displayed microsatellite site mutations and reduced protein expression of transforming growth factor-beta receptor type II (6 of 19 lesions) and Bax (4 of 19 lesions). These results suggest that, in PPH, proliferated endothelial cells have genetic alterations associated with microsatellite instability and concomitant perturbation of growth and apoptosis gene expression akin to neoplasia. The full text of this article is available at http://www.circresaha.org.

Protein targets of monocrotaline pyrrole in pulmonary artery endothelial cells

A single administration of monocrotaline to rats results in pathologic alterations in the lung and heart similar to human pulmonary hypertension. In order to produce these lesions, monocrotaline is oxidized to monocrotaline pyrrole in the liver followed by hematogenous transport to the lung where it injures pulmonary endothelium. In this study, we determined specific endothelial targets for (14)C-monocrotaline pyrrole using two-dimensional gel electrophoresis and autoradiographic detection of protein metabolite adducts. Selective labeling of specific proteins was observed. Labeled proteins were digested with trypsin, and the resulting peptides were analyzed using matrix-assisted laser desorption ionization mass spectrometry. The results were searched against sequence data bases to identify the adducted proteins. Five abundant adducted proteins were identified as galectin-1, protein-disulfide isomerase, probable protein-disulfide isomerase (ER60), beta- or gamma-cytoplasmic actin, and cytoskeletal tropomyosin (TM30-NM). With the exception of actin, the proteins identified in this study have never been identified as potential targets for pyrroles, and the majority of these proteins have either received no or minimal attention as targets for other electrophilic compounds. The known functions of these proteins are discussed in terms of their potential for explaining the pulmonary toxicity of monocrotaline.

Hyperuricemia in severe pulmonary hypertension

STUDY OBJECTIVE

Hyperuricemia occurs frequently in patients with myeloproliferative and lymphoproliferative disorders and in patients with congenital heart disease associated with polycythemia. Whether hyperuricemia is common in patients with severe pulmonary hypertension is not known.

DESIGN, PATIENTS, MEASUREMENTS

In the Pulmonary Hypertension Center at the University of Colorado Health Sciences Center between September 1991 and August 1997, 442 consecutive patients were evaluated with right heart catheterization; 191 patients also had a measurement of the serum uric acid (UA) in close temporal proximity to the hemodynamic evaluation.

RESULTS

Of the 191 patients with a complete data set, 99 patients had primary pulmonary hypertension (PPH) and 92 had secondary pulmonary hypertension. For the entire cohort with severe pulmonary hypertension (n = 191), there was a positive correlation between the natural logarithm of the serum UA (lnUA) and the mean right atrial pressure (RAP; r = 0.47; p < 0.001). When analyzed separately, the correlation between lnUA and RAP was stronger in the patients with PPH (r = 0.642; p < 0.001). This correlation cannot be explained by diuretic use or impaired hepatocellular function. Neither mean pulmonary artery pressure nor cardiac output was as well correlated with the RAP when compared with the lnUA. Some patients with PPH had serum UA measurements repeated during treatment with chronic IV prostacyclin infusion. Eleven of these 18 patients (61%) demonstrated a decrease in serum UA during prostacyclin treatment.

CONCLUSION

There is a positive correlation between the RAP elevation and the serum UA levels in patients with PPH. Serum UA levels drop in some, but not all PPH patients during chronic prostacyclin infusion therapy.

Central pulmonary artery lesions in chronic obstructive pulmonary disease: A transesophageal echocardiography study

BACKGROUND

In patients with acute pulmonary embolism, transesophageal echocardiography (TEE) often reveals presumably thrombotic lesions within the central pulmonary arteries (CPAs). These CPA lesions, when found in patients with primary pulmonary hypertension, have been attributed to in situ thrombosis or atherosclerosis. We hypothesized that similar CPA lesions may also develop in patients with chronic obstructive pulmonary disease (COPD) in the absence of pulmonary embolism.

METHODS AND RESULTS

We examined by TEE 25 patients with COPD and 27 control patients with left heart disease. None of the patients had previous pulmonary embolism or ileofemoral and popliteal vein thrombosis. By use of TEE, CPA lesions were found in 12 COPD patients (48%) and 2 control patients (7.4%) (P<0.01). When CPA lesions were subdivided into types 1 (protruding and mobile) and 2 (wall-adherent), type 1 lesions proved to be uncommon, being found within the pulmonary trunk in 12% and 3.7% of COPD and control patients, respectively (P=NS). Conversely, type 2 lesions, which were always localized in the right pulmonary artery, were frequent in COPD patients (36%) and rare in control patients (3.7%) (P<0.01). When available, helical CT and MR angiography confirmed TEE findings, supporting an atherosclerotic origin of type 2 lesions, which were different from typical thrombotic lesions. FEV(1)/FVC ratio, RV/TLC ratio, PaO(2), hematocrit value, and pulmonary artery systolic pressure were not significantly different in COPD patients with and without CPA lesions. At TEE, however, COPD patients with CPA lesions showed a larger size of the main and right pulmonary arteries.

CONCLUSIONS

TEE often reveals CPA lesions in stable patients with COPD even in the absence of significant pulmonary hypertension and not in close relation with the severity of pulmonary dysfunction.

How to manage primary pulmonary hypertension. Giving hope to patients with a life-threatening illness

Primary pulmonary hypertension presents a challenge to practicing physicians, in both diagnosis and management. Exposure to anorexigens and complaints of dyspnea and fatigue should prompt careful physical examination and Doppler echocardiography to assess patients for pulmonary hypertension. The burden on office practitioners is heavy, considering how often fatigue and dyspnea are reported, but the key is recognizing when these findings are out of proportion to the patient's well appearance. The discovery of epoprostenol therapy has revolutionized the approach to primary pulmonary hypertension. It has markedly improved quality of life and extended survival in patients with the condition, and it has changed the physician's role from providing emotional support to dying patients to providing management of a chronic disease.

Monocrotaline pyrrole interacts with actin and increases thrombin-mediated permeability in pulmonary artery endothelial cells

One of the earliest morphologic changes evident in the monocrotaline (MCT) model of pulmonary hypertension in rats is microvascular leak. Whether this represents a direct effect of MCT metabolites or is secondary to inflammatory and thrombotic changes remains uncertain. To determine whether MCT directly affects endothelial cell permeability barrier function, we characterized the interaction of the reactive pyrrole intermediate of MCT (MCTP) with endothelial cell actin and characterized its effects on thrombin-mediated signal transduction and monolayer permeability. Bovine pulmonary endothelial cells (BPAEC) treated with MCTP had altered distribution of filamentous actin evident by fluorescence microscopy. Correlative Western blots and autoradiography of actin isolated from BPAEC treated with 14C-MCTP showed comigration of actin and MCTP-derived 14C. MCTP treatment did not alter cellular free Ca2+ concentrations nor did it interfere with thrombin-mediated intracellular Ca2+ signal. Pretreatment with MCTP significantly augmented the thrombin-mediated transudation of Evan's blue albumin in BPAEC monolayers apparently by increasing the size of intercellular gaps. We conclude that MCTP directly interacts with actin to alter its polymerization state but does not significantly affect endothelial cell response to contractile stimulus. Our results suggest that MCTP may affect endothelial cell barrier function through alterations in intracellular junctions.

Primary pulmonary hypertension

Primary pulmonary hypertension (PPH) is a progressive disease characterised by raised pulmonary vascular resistance, which results in diminished right-heart function due to increased right ventricular afterload. PPH occurs most commonly in young and middle-aged women; mean survival from onset of symptoms is 2-3 years. The aetiology of PPH is unknown, although familial disease accounts for roughly 10% of cases, which suggests a genetic predisposition. Current theories on pathogenesis focus on abnormalities in interaction between endothelial and smooth-muscle cells. Endothelia-cell injury may result in an imbalance in endothelium-derived mediators, favouring vasoconstriction. Defects in ion-channel activity in smooth-muscle cells in the pulmonary artery may contribute to vasoconstriction and vascular proliferation. Diagnostic testing primarily excludes secondary causes. Catheterisation is necessary to assess haemodynamics and to evaluate vasoreactivity during acute drug challenge. Decrease in pulmonary vascular resistance in response to acute vasodilator challenge occurs in about 30% of patients, and predicts a good response to chronic therapy with oral calcium-channel blockers. For patients unresponsive during acute testing, continuous intravenous epoprostenol (prostacyclin, PGI2) improves haemodynamics and exercise tolerance, and prolongs survival in severe PPH (NYHA functional class III-IV). Thoracic transplantation is reserved for patients who fail medical therapy. We review the progress made in diagnosis and treatment of PPH over the past 20 years.

Abnormalities in circulating von Willebrand factor and survival in pulmonary hypertension

BACKGROUND

Changes in circulating von Willebrand factor (vWF) have been widely used for evaluating the severity of endothelial dysfunction in vascular disorders. In pulmonary hypertension, quantitative and structural abnormalities in circulating von Willebrand factor have been identified. We therefore hypothesized that these abnormalities could have prognostic implications.

PATIENTS AND METHODS

We studied 30 consecutive medically treated patients with primary (n = 11) or secondary precapillary pulmonary hypertension associated with congenital heart disease (n = 16) or schistosomiasis (n = 3). Plasma antigenic activity of vWF (vWF:Ag) was measured by electroimmunodiffusion. The relative concentration of low molecular weight vWF multimers (vWF:LMW/Total) was determined by Western immunoblotting. Results of initial evaluation were analyzed at the end of the first and third years of follow-up.

RESULTS

Baseline vWF:Ag activity (P <0.0002) and the vWF: LMW/Total ratio (P <0.005) were higher in patients who died during the first year than in survivors. All patients with vWF:Ag activity >250% or a vWF:LMW/Total ratio >70% died in the first year. All 7 patients with vWF:Ag activity <100% were alive at the end of 3 years of follow-up. A vWF:LMW/Total ratio >68% was 67% sensitive and 95% specific for 1-year mortality, with an overall predictive value of 80%. Both vWF:Ag levels and mortality were greater in the patients with primary pulmonary hypertension than in patients with secondary pulmonary hypertension.

CONCLUSION

Patients with pulmonary hypertension who have abnormalities in circulating vWF have reduced 1-year survival. This might affect decisions such as patient assignment to lung transplantation.

Coagulation and fibrinolytic profiles in patients with severe pulmonary hypertension

STUDY OBJECTIVES

Although in situ thrombosis is a prominent finding in lung vessels from patients with primary and secondary pulmonary hypertension, to our knowledge, plasma coagulation factors that might contribute to a hypercoagulable state have not been fully investigated. We hypothesized that the local coagulation environment in the lung vasculature is important to progression if not initiation of pulmonary hypertension.

DESIGN

Quasi-experimental cross-sectional design with concurrent controls.

SETTING

Referral clinics and inpatient services of a University Hospital and a Veterans Administration Medical Center.

PARTICIPANTS

To investigate the role of plasma coagulation factors in severe pulmonary hypertension, we sampled plasma from patients with primary pulmonary hypertension, patients with pulmonary hypertension secondary to a discernible etiology, and normal adult control subjects.

RESULTS

We detected abnormalities of the thrombomodulin/protein C anticoagulant system, evidenced by a decrease in soluble thrombomodulin, in patients with primary pulmonary hypertension. In the patients with primary pulmonary hypertension, we found impaired fibrinolytic activity, with a rise in the fibrinolytic inhibitor plasminogen activator 1 and elevated euglobulin lysis time. Lower fibrinolytic activity correlated with high mean pulmonary artery pressure. In contrast, in patients with secondary pulmonary hypertension, von Willebrand factor antigen and fibrinogen levels were increased, and fibrinolytic activity decreased.

CONCLUSIONS

Different patterns of coagulation and fibrinolytic abnormalities are apparent in plasma from patients with primary and secondary pulmonary hypertension. Although we are unable to address causality with this study, we speculate that abnormalities of these coagulation mechanisms may initiate or play a role in perpetuation of pulmonary hypertension.

Pathology of pulmonary thromboembolism

The incidence of pulmonary thromboembolism is hard to assess by the pathologist as a result of seasonal variation of embolism and disappearance of emboli by thrombolysis. However, the great differences in estimates of the incidence in routine hospital autopsies is mainly related to variation in scrutiny of the investigation and in size of area searched microscopically. Obstruction of major pulmonary arteries almost always results from thromboembolism which is most often found in its acute stage. In chronic major vessel embolism, arterial obstruction by an organized mass may produce pulmonary hypertension. Recanalization of such a mass results in so-called bands and webs. There are no reliable criteria to differentiate between emboli and primary thrombi or their sequelae. In peripheral, particularly muscular pulmonary arteries, thrombi are most likely primary, especially when associated with advanced age and with pulmonary hypertension. However, small arteries may be subject to extensive microembolism following fragmentation of large thromboemboli. Thrombotic arteriopathy is the pulmonary arterial disease based upon either primary thrombosis or embolism. It is often associated with pulmonary hypertension, and characterized by irregular, nonlaminar, often obliterative, intimal fibrosis. Recanalization channels, sometimes widening to separate intravascular fibrous septa, are characteristic features. Reversibility of post-thrombotic lesions is very limited.

Exploration of the pulmonary circulation. Festschrift to Professor Donald Heath

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Plexogenic arteriopathy

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