Updated clinical classification of pulmonary hypertension

Emerging drugs for pulmonary hypertension

IMPORTANCE OF THE FIELD

Pulmonary arterial hypertension (PAH) is a clinical syndrome characterized by structural narrowing of the small pulmonary arteries that often culminates in fatal right heart failure.

AREAS COVERED IN THIS REVIEW

PubMed was searched for PAH and treatment. Data from scientific meetings and pharmaceutical websites are also included. There are currently eight FDA approved drugs for PAH that fall into one of three classes: prostacyclins, endothelin-receptor antagonists and PDE-5 inhibitors. All have important limitations and morbidity and mortality remain high. Several new agents with similar mechanisms of action are in clinical development. Multiple novel therapeutic targets are being explored. New applications for PAH therapies, such as pulmonary hypertension due to left heart and lung disease, are also being investigated.

WHAT THE READER WILL GAIN

An understanding of currently available drugs and those in clinical development for pulmonary hypertension.

TAKE HOME MESSAGE

Drugs targeting the pulmonary vasculature have been an extremely active area of basic and clinical research for the past 20 years and will continue to be so for the foreseeable future. Considerable progress has been made, and yet there continues to be a great unmet medical need for developing more efficacious therapies.

Schistosomiasis-associated pulmonary hypertension: pulmonary vascular disease: the global perspective

Inflammation is likely a critical underlying etiology in many forms of severe pulmonary hypertension (PH), and schistosomiasis-associated PH, one of the most common causes of PH worldwide, is likely driven by the host response to parasite antigens. More than 200 million people are infected with schistosomiasis, the third most common parasitic disease, and approximately 1% of those chronically infected develop PH. Acute cutaneous infection causes inflammation at the site of parasite penetration followed by a subacute immune complex-mediated hypersensitivity response as the parasite migrates through the lungs. Chronic schistosomiasis infection induces a granulomatous inflammation around ova deposited in the tissue. In particular, Schistosoma mansoni migrates to the portal venous system and causes preportal fibrosis in a subset of individuals and appears to be a prerequisite for PH. Portal hypertension facilitates shunting of ova from the portal system to the pulmonary arterial tree, resulting in localized periovular pulmonary granulomas. The pulmonary vascular remodeling is likely a direct consequence of the host inflammatory response, and portopulmonary hypertension may be a significant contributor. New specific therapies available for PH have not been widely tested in patients with schistosomiasis and often are unavailable for those infected in resource-poor areas of the world where schistosomiasis is endemic. Furthermore, the current PH therapies in general target vasodilation rather than vascular remodeling and inflammation. Further research is needed into the pathogenic mechanism by which this parasitic infection results in pulmonary vascular remodeling and PH, which also may be informative regarding the etiology of other types of PH.

Characterization of connective tissue disease-associated pulmonary arterial hypertension from REVEAL: identifying systemic sclerosis as a unique phenotype

BACKGROUND

REVEAL (the Registry to Evaluate Early and Long-term Pulmonary Arterial Hypertension Disease Management) is the largest US cohort of patients with pulmonary arterial hypertension (PAH) confirmed by right-sided heart catheterization (RHC), providing a more comprehensive subgroup characterization than previously possible. We used REVEAL to analyze the clinical features of patients with connective tissue disease-associated PAH (CTD-APAH).

METHODS

All newly and previously diagnosed patients with World Health Organization (WHO) group 1 PAH meeting RHC criteria at 54 US centers were consecutively enrolled. Cross-sectional and 1-year mortality and hospitalization analyses from time of enrollment compared CTD-APAH to idiopathic disease and systemic sclerosis (SSc) to systemic lupus erythematosus (SLE), mixed connective tissue disease (MCTD), and rheumatoid arthritis (RA).

RESULTS

Compared with patients with idiopathic disease (n = 1,251), patients with CTD-APAH (n = 641) had better hemodynamics and favorable right ventricular echocardiographic findings but a higher prevalence of pericardial effusions, lower 6-min walk distance (300.5 ± 118.0 vs 329.4 ± 134.7 m, P = .01), higher B-type natriuretic peptide (BNP) levels (432.8 ± 789.1 vs 245.6 ± 427.2 pg/mL, P < .0001), and lower diffusing capacity of carbon monoxide (Dlco) (44.9% ± 18.0% vs 63.6% ± 22.1% predicted, P < .0001). One-year survival and freedom from hospitalization were lower in the CTD-APAH group (86% vs 93%, P < .0001; 67% vs 73%, P = .03). Compared with patients with SSc-APAH (n = 399), those with other CTDs (SLE, n = 110; MCTD, n = 52; RA, n = 28) had similar hemodynamics; however, patients with SSc-APAH had the highest BNP levels (552.2 ± 977.8 pg/mL), lowest Dlco (41.2% ± 16.3% predicted), and poorest 1-year survival (82% vs 94% in SLE-APAH, 88% in MCTD-APAH, and 96% in RA-APAH).

CONCLUSIONS

Patients with SSc-APAH demonstrate a unique phenotype with the highest BNP levels, lowest Dlco, and poorest survival of all CTD-APAH subgroups.

TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT00370214; URL: clinicaltrials.gov.

Development of pulmonary arterial hypertension in women: interplay of sex hormones and pulmonary vascular disease

Pulmonary arterial hypertension (PAH) is a progressive disease of the pulmonary vasculature, ultimately resulting in right heart failure and death. This disease is strongly predominant in females, although little is known regarding how sex influences disease development. Recent developments highlighting the importance of estrogen metabolites in both animal models and human disease have substantially increased our understanding of PAH in women. This review will focus on general knowledge of PAH, translational and basic science data regarding sex hormones in the pulmonary vasculature and on clinical issues that are particular to women with PAH. Future directions for study include the influence of sex hormones on right ventricular responses, improving the understanding of the influence of estrogen exposure in human disease and the study of dehydroepiandrosterone in basic science and human disease.

Association of anemia and long-term survival in patients with pulmonary hypertension

BACKGROUND

Anemia is a marker of worsened clinical outcome in patients with heart failure from left ventricular dysfunction. Pulmonary hypertension often results in right ventricular dysfunction. Accordingly we sought to examine the association of hemoglobin levels and long-term all-cause mortality in a cohort of patients with pulmonary hypertension.

METHODS

Baseline demographic information, clinical characteristics and fasting blood work were obtained in a cohort of 145 patients with pulmonary hypertension referred for pulmonary vasodilator testing. Data was retrospectively analyzed with Cox-proportional hazards analysis.

RESULTS

Baseline characteristics of the cohort included age (mean±SD) 55.8±14.6 years, 75% women, 50% with idiopathic pulmonary hypertension, mean pulmonary artery pressure 46.1±14.2 mm Hg and arterial O(2) saturation 91±6 %. The most commonly utilized pulmonary hypertension specific therapeutic agents in descending order of frequency were epoprostenol (27%), sildenafil (21%), bosentan (17%), and treprostinil (6%). Over a median follow-up of 2.1 years, there were 39 deaths (26.9%). Patients who died had significantly lower hemoglobin levels than those survived (12.2±2.3 vs. 13.7±2.0, p<0.001). After adjustment for known predictors of death and pulmonary hypertension etiology, anemic patients were 3.3 times more likely to die than non-anemic patients (95% CI [1.43-7.51], p=0.005).

CONCLUSIONS

Hemoglobin levels closely parallel survival in pulmonary hypertension. Modification of anemia in this disorder could alter the clinical course and calls for further research in this area.

The emergence of oral tadalafil as a once-daily treatment for pulmonary arterial hypertension

Pulmonary hypertension (PH) is found in a vast array of diseases, with a minority representing pulmonary arterial hypertension (PAH). Idiopathic PAH or PAH in association with other disorders has been associated with poor survival, poor exercise tolerance, progressive symptoms of dyspnea, and decreased quality of life. Left untreated, patients with PAH typically have a progressive decline in function with high morbidity ultimately leading to death. Advances in medical therapy for PAH over the past decade have made significant inroads into improved function, quality of life, and even survival in this patient population. Three classes of pulmonary artery-specific vasodilators are currently available in the United States. They include prostanoids, endothelin receptor antagonists, and phosphodiesterase type 5 (PDE5) inhibitors. In May 2009, the FDA approved tadalafil, the first once-daily PDE5 inhibitor for PAH. This review will outline the currently available data on tadalafil and its effects in patients with PAH.

Hemodynamic effects of chronic smoking in liver cirrhosis: a role for adrenomedullin

OBJECTIVE

To evaluate the effect of smoking on the hemodynamic status of liver cirrhosis and several vasoactive substances.

METHODS

Hemodynamic, blood gases values, liver parameters, and several vasopressors and vasodilators substances were measured in consecutive inpatients diagnosed of liver cirrhosis divided into two groups: smokers and nonsmokers.

RESULTS

Nineteen smoking cirrhotic patients and 13 nonsmoking cirrhotic patients were studied. Both groups showed similar age, Child--Pugh and model for end-stage liver disease indexes. Smokers had higher levels of hemoglobin and lower partial pressure of arterial oxygen, FEV1/FVC %, cardiac output and total vascular resistance than nonsmokers. Plasma level of adrenomedullin was independently higher in nonsmoking cirrhotic patients than in smokers.

CONCLUSION

In contrast with smoking cirrhotic patients, nonsmoking cirrhotic patients show an increased systemic vasodilation, which could depend on higher plasmatic levels of adrenomedullin.

Right ventricular function in patients with pulmonary hypertension; the value of myocardial performance index measured by tissue Doppler imaging

AIMS

Myocardial performance index (MPI) measured by conventional Doppler is routinely used to assess right ventricular (RV) systolic function in patients with pulmonary hypertension (PH). Our aim was to determine whether MPI measured by Doppler tissue imaging (tMPI) is effective in assessing RV function in these patients.

METHODS AND RESULTS

Retrospectively, we have studied 196 patients with chronic PH [pulmonary arterial systolic pressure (PASP) 81 +/- 40 mmHg] and 37 healthy volunteers (PASP of 27 +/- 7 mmHg). According to the exclusion criteria, 172 patients were included in the final study cohort. All patients were evaluated for RV systolic function by different parameters. MPI was measured by both conventional and tissue Doppler imaging. Bland-Altman analysis showed moderate agreement between MPI and tMPI (the mean difference was -0.02, absolute difference = -0.32 to 0.29; 95% intervals of agreement, percentage of average = -46.6 to 40.8%). In 50 consecutive PH patients where additional parameters were calculated, we found a significant correlation between tMPI and RV ejection fraction (r = -0.73, P< 0.0001) and RV fractional area change (r = -0.58, P< 0.0001). No significant inter- and intra-observer variability was identified.

CONCLUSION

This study demonstrated a moderate agreement between two methods of measuring MPI. A good correlation of tMPI with RV ejection fraction and RV fractional area change was found indicating that tMPI might be superior to MPI Doppler. tMPI is a parameter unaffected by RV geometry and importantly has the advantage of simultaneously recording the time intervals from the same cardiac cycle.

Usefulness of right-to-left shunting and poor exercise gas exchange for predicting prognosis in patients with pulmonary arterial hypertension

We hypothesized that the longitudinal changes in peak oxygen uptake, ventilatory efficiency, and exercise-induced right-to-left shunting in patients with pulmonary arterial hypertension (PAH) would predict outcomes better than baseline measurements alone. Patients with PAH die prematurely. Identifying prognostic markers is critical for treating patients with PAH; however, longitudinal prognostic information of PAH is limited. We enrolled 103 patients with PAH into a long-term, prospective outcome study using serial cardiopulmonary exercise testing to measure the peak oxygen uptake, ventilatory efficiency (ratio of ventilation to carbon dioxide output at the anaerobic threshold), right-to-left shunting, and other factors in patients treated with optimal therapy. The patients were followed up for a mean of 4.7 years. During the study period, 20 patients died, and 3 underwent lung transplantation. The baseline peak oxygen uptake and ventilatory efficiency was 0.79 L/min and 49 (normal <34), respectively, reflecting severe disease. Poorer ventilatory efficiency and greater New York Heart Association classification were associated with poor outcome at baseline and at follow-up. On multivariate analysis, the persistence or development of an exercise-induced right-to-left shunt strongly predicted death or transplantation (p <0.0001), independent of the hemodynamics and all other exercise measures, including peak oxygen uptake and ventilatory efficiency. The absence of a shunt at baseline was associated with a 20% rate of nonsurvival, which decreased to 7% at follow-up. A poorer ventilatory efficiency appeared to be associated with a poor outcome in patients without a shunt. In conclusion, a persistent exercise-induced right-to-left shunt and poor ventilatory efficiency were highly predictive of poor outcomes in patients with pulmonary arterial hypertension.

[Scleroderma]

Scleroderma (synonyms: systemic sclerosis, systemic scleroderma) is a systemic disease which affects the skin as well as internal organs such as the lungs, gastrointestinal tract, kidneys, and the heart. Pathogenetically a distinction should be made between uncontrolled formation of extracellular matrix proteins (fibrosis) and vasculopathy. In addition to organ fibrosis, this leads to a clinical picture of vascular manifestations. These include fingertip ulcers, pulmonary arterial hypertension, and acute renal crisis. Localized forms of scleroderma, such as morphea, which do not involve organ complications, should be differentiated from systemic sclerosis. Due to its clinical heterogeneity and high rate of morbidity and mortality, systemic sclerosis poses an enormous diagnostic and therapeutic challenge in everyday clinical practice. This review article summarizes the current status of classification and epidemiology, pathogenesis, and the most important clinical manifestations such as interstitial fibrosis, pulmonary arterial hypertension, acute renal crisis, and peripheral vasculopathy and provides an overview of current and future treatment options.

Portopulmonary hypertension: short review

Portopulmonary hypertension (PoPH) is an underrecognized complication of portal hypertension, related to cirrhosis and noncirrhotic portal hypertension. PoPH has been found in 5-6% of patients with decompensated liver disease and may adversely affect outcome after liver transplantation. The prevalence of PoPH is unrelated to the severity of liver disease but associated with female sex and underlying autoimmune liver disease. Diagnosis of PoPH is based on screening with Doppler echocardiography and confirmation by right-heart catheterization. Treatment options with proven efficacy in idiopathic pulmonary hypertension include endothelin receptor antagonists, prostanoids, and sildenafil. In PoPH, such targeted treatment was found to be safe in small uncontrolled studies but randomized trials demonstrating its benefit are lacking.

Systemic sclerosis-associated pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a devastating vascular complication of a number of connective tissue diseases, including systemic sclerosis (SSc), where it has a dramatic impact on the clinical course and overall survival and is the single most common cause of death in patients afflicted with this syndrome. Although remarkable advances have been achieved in elucidating the pathogenesis of PAH over the past 2 decades, leading to the development of disease-targeted therapies for the idiopathic form of this condition (IPAH), the response to therapy is suboptimal in SSc-related PAH (SSc-PAH), and survival remains very poor. Factors accounting for striking clinical and prognostic differences between these two syndromes are unclear but may include a more pronounced autoimmune, cellular, and inflammatory response, and a higher prevalence of comorbidities in SSc-PAH, including cardiac and pulmonary venous and parenchymal involvement. Furthermore, currently available markers of disease severity and clinical tools to assess response to therapy, which may be reliable in IPAH, are either limited or lacking in SSc-PAH. Thus, a more focused approach, including a better understanding of the pathogenesis and genetic factors underlying the development of SSc-PAH, a search for more specific and reliable tools to adequately assess functional impairment and monitor therapy, as well as the design of novel targeted therapies, are all urgently required to alter the dismal course of this syndrome.

Nursing considerations in the care of patients with pulmonary hypertension

Pulmonary hypertension is a potentially lethal condition that may be encountered during the entire life span of patients with many forms of congenital or acquired heart disease, pulmonary disorders, and other diseases. Each pulmonary hypertensive patient requires anticipatory interventions geared to prevent severe exacerbations of the pulmonary hypertensive condition, promote pulmonary vasodilation, and optimize ventricular function. Patients with pulmonary hypertension are at higher risk for developing pulmonary hypertensive episodes in the immediate postoperative period after cardiac surgery, as well as during nonsurgical admissions. Nurses are in a critical position to provide anticipatory care to prevent the development of pulmonary hypertensive events. Nurses can be instrumental in optimizing outcomes for patients with pulmonary hypertension by providing immediate care upon the development of a pulmonary hypertension event and by monitoring ongoing responses to adjustments in therapeutic interventions.

Riociguat for pulmonary hypertension

Pulmonary hypertension (PH) encompasses a group of diseases associated with progressively increasing pulmonary vascular resistance, right heart failure and premature death. Riociguat is a novel, first-in-class oral drug that directly stimulates soluble guanylate cyclase, both independently of the endogenous vasodilator nitric oxide (NO) and in synergy with NO. Single oral doses of riociguat were well tolerated in a Phase I study of healthy volunteers. They had a favorable safety profile, and improved pulmonary hemodynamics and cardiac index to a greater extent than inhaled NO in a proof-of-concept study in patients with moderate-to-severe PH. In a 12-week Phase II trial in patients with chronic thromboembolic PH or pulmonary arterial hypertension, pulmonary hemodynamics and exercise capacity improved following individual dose titration with oral riociguat, which was generally well tolerated. Further trials in PH have been initiated.

CXC-chemokine ligand 10 in idiopathic pulmonary arterial hypertension: marker of improved survival

CXC-chemokine ligand 10 (CXCL10) inhibits angiogenesis and attracts activated T lymphocytes. Abnormal angiogenesis and lymphocytic infiltration participate in the pathobiology of pulmonary arterial hypertension (PAH). We hypothesized that serum CXCL10 is elevated in idiopathic PAH and that it is associated with clinical outcomes. This was a cohort study that included 40 idiopathic PAH patients (age = 44 +/- 14 years, 37 females) and 22 healthy controls (age = 35 +/- 6 years, 18 females). It took place at the Pulmonary Vascular Program at the Cleveland Clinic. Serum CXCL10 levels were measured by an enzyme-linked immunosorbent assay. A cutoff value of CXCL10 for best distinguishing alive and dead patients was obtained from a receiver operating characteristic curve (ROC). Survival and time to clinical worsening curves according to the appropriate CXCL10 level were derived by the Kaplan-Meier method and compared by means of the log-rank test. The prognostic value of CXCL10 and of other variables of interest was tested by Cox proportional hazards regression analysis. Serum CXCL10 levels were elevated in PAH subjects compared to controls [CXCL10 pg/ml (mean +/- SEM) for PAH: 306 +/- 73, and for controls: 92 +/- 10; p < 0.0001]. CXCL10 levels higher than 111 pg/ml discriminated survivors from nonsurvivors with a sensitivity of 81% and a specificity of 75% (area under the ROC curve = 0.74). After a mean follow-up of 23.5 +/- 13.5 months since the day of venous sampling, higher CXCL10 levels were associated with improved survival (hazard ratio for mortality = 0.10, 95% confidence interval = 0.01-0.97; p = 0.01). Serum CXCL10 is elevated in PAH and this is associated with improved survival.

Pulmonary hypertension associated with bone marrow transplantation

Bone marrow transplantation (BMT) is one of the promising methods of treatment of hematologic malignancy. However, it has a variety of complications since it involves fatal doses of anti-cancer drugs and radiation during the conditioning period. Among the various complications of BMT, pulmonary hypertension is rare and its pathogenesis is poorly understood. A 35-year-old female with acute myeloid leukemia (AML) presented with pulmonary hypertension after BMT. Although she exhibited severe dyspnea on admission, her general condition markedly improved after oxygen therapy and treatment with warfarin and beraprost sodium. Her pulmonary hypertension was diagnosed as pulmonary arterial hypertension (PAH) related to BMT. Although PAH has only rarely been reported as a complication of BMT, we present here for the first time an adult patient with PAH associated with BMT who exhibited marked improvement with medical treatment. This case indicates that attention needs to be paid to the clinical symptoms and physical findings of PAH as a complication of BMT.

[Guidelines for the diagnosis and treatment of pulmonary hypertension]

INTRODUCTION

A joint Task Force of the ESC and of the ERS has developed guidelines on the diagnosis and treatment of pulmonary hypertension (PH) to provide updated information on the management of patients with this condition.

STATE OF THE ART

The term pulmonary hypertension (PH) describes a group of devastating and life-limiting diseases, defined by mean pulmonary artery pressure >25 mmHg at rest. The diagnosis of PH requires a series of investigations intended to confirm the diagnosis, clarify the clinical group and the specific aetiology and an algorithm for this is proposed. Several drugs are currently approved to try to correct endothelial dysfunction. They lead to a significant improvement in the prognosis of patients who are in NYHA functional class II, III or IV. The evaluation of the severity of PH has a pivotal role in the choice of initial treatment and evaluation of the response to therapy in individual patients.

PERSPECTIVE

These guidelines should be widely disseminated and implemented in order to improve the management of patients with PH.

CONCLUSION

These guidelines summarise recent advances in the understanding and management of PH.

A comparison of echocardiography to invasive measurement in the evaluation of pulmonary arterial hypertension in a rat model

Pulmonary arterial hypertension (PAH) is a life-threatening condition characterized by progressive elevation in pulmonary artery pressure (PAP) and total pulmonary vascular resistance (TPVR). Recent advances in imaging techniques have allowed the development of new echocardiographic parameters to evaluate disease progression. However, there are no reports comparing the diagnostic performance of these non-invasive parameters to each other and to invasive measurements. Therefore, we investigated the diagnostic yield of echocardiographically derived TPVR and Doppler parameters of PAP in screening and measuring the severity of PAH in a rat model. Serial echocardiographic and invasive measurements were performed at baseline, 21 and 35 days after monocrotaline-induction of PAH. The most challenging echocardiographic derived TPVR measurement had good correlation with the invasive measurement (r = 0.92, P < 0.001) but also more simple and novel parameters of TPVR were found to be useful although the non-invasive TPVR measurement was feasible in only 29% of the studies due to lack of sufficient tricuspid valve regurgitation. However, echocardiographic measures of PAP, pulmonary artery flow acceleration time (PAAT) and deceleration (PAD), were measurable in all animals, and correlated with invasive PAP (r = -0.74 and r = 0.75, P < 0.001 for both). Right ventricular thickness and area correlated with invasive PAP (r = 0.59 and r = 0.64, P < 0.001 for both). Observer variability of the invasive and non-invasive parameters was low except in tissue-Doppler derived isovolumetric relaxation time. These non-invasive parameters may be used to replace invasive measurements in detecting successful disease induction and to complement invasive data in the evaluation of PAH severity in a rat model.

Diagnosis and management of pulmonary hypertension in systemic sclerosis

Patients with systemic sclerosis (SSc) can develop pulmonary hypertension (PH; mean pulmonary artery pressure >/= 25 mm Hg) caused by pulmonary arterial hypertension (PAH), left ventricular disease, or pulmonary fibrosis. PAH is a pulmonary vascular disease, the diagnosis of which requires pulmonary capillary wedge pressure less than 15 mm Hg, pulmonary vascular resistance greater than 3 Wood Units, and exclusion of thromboembolism and parenchymal lung disease. Molecular mechanisms underlying PAH-SSc include activation of inflammatory and fibrogenic pathways in the vasculature and right ventricle. Circulating autoantibodies trigger endothelial damage and fibroblast activation. PAH most commonly occurs as a late complication in patients with limited cutaneous disease and anticentromere antibodies. Although echocardiography is a useful screening tool, heart catheterization is required to diagnose PAH before initiating therapy. Prognosis and therapeutic response are worse in PAH-SSc than in other PAH categories (median survival, 1-3 y). Approved therapies include prostacyclins, endothelin antagonists, and phosphodiesterase type 5 inhibitors. Research is needed to define disease mechanisms and develop effective therapies.

Hypoxia inducible-factor1alpha regulates the metabolic shift of pulmonary hypertensive endothelial cells

Severe pulmonary hypertension is irreversible and often fatal. Abnormal proliferation and resistance to apoptosis of endothelial cells (ECs) and hypertrophy of smooth muscle cells in this disease are linked to decreased mitochondria and preferential energy generation by glycolysis. We hypothesized this metabolic shift of pulmonary hypertensive ECs is due to greater hypoxia inducible-factor1alpha (HIF-1alpha) expression caused by low levels of nitric oxide combined with low superoxide dismutase activity. We show that cultured ECs from patients with idiopathic pulmonary arterial hypertension (IPAH-ECs) have greater HIF-1alpha expression and transcriptional activity than controls under normoxia or hypoxia, and pulmonary arteries from affected patients have increased expression of HIF-1alpha and its target carbonic anhydrase IX. Decreased expression of manganese superoxide dismutase (MnSOD) in IPAH-ECs paralleled increased HIF-1alpha levels and small interfering (SI) RNA knockdown of MnSOD, but not of the copper-zinc SOD, increased HIF-1 protein expression and hypoxia response element (HRE)-driven luciferase activity in normoxic ECs. MnSOD siRNA also reduced nitric oxide production in supernatants of IPAH-ECs. Conversely, low levels of a nitric oxide donor reduced HIF-1alpha expression in normoxic IPAH-ECs. Finally, mitochondria numbers increased in IPAH-ECs with knockdown of HIF-1alpha. These findings indicate that alterations of nitric oxide and MnSOD contribute to pathological HIF-1alpha expression and account for lower numbers of mitochondria in IPAH-ECs.

Bosentan: a review of its use in the management of mildly symptomatic pulmonary arterial hypertension

Bosentan (Tracleer) is an orally administered dual endothelin-1 (ET-1) receptor antagonist approved for use in patients with WHO class II (mildly symptomatic) pulmonary arterial hypertension (PAH). Oral bosentan therapy was beneficial and generally well tolerated in patients with mildly symptomatic PAH. In a well designed, placebo-controlled trial in adolescents and adults with mildly symptomatic PAH, pulmonary vascular resistance was significantly reduced with bosentan relative to placebo, but the 6-minute walk distance did not increase significantly. Similarly, pediatric patients (most of whom had mildly symptomatic PAH) in a small uncontrolled trial experienced some improvement in hemodynamic variables with bosentan, but did not experience a significant increase in exercise capacity. Adverse events associated with bosentan were consistent with those seen in other indications, with major concerns being the potential for teratogenicity and hepatotoxicity, for which regular liver function monitoring is recommended. Overall, considering the progressive nature of PAH, bosentan extends the treatment options available to patients with mildly symptomatic PAH.

Clinical outcomes of pulmonary arterial hypertension in patients carrying an ACVRL1 (ALK1) mutation

RATIONALE

Activin A receptor type II-like kinase-1 (ACVRL1, also known as ALK1) mutation is a cause of hereditary hemorrhagic telangiectasia (HHT) and/or heritable pulmonary arterial hypertension (PAH).

OBJECTIVES

To describe the characteristics of patients with PAH carrying an ACVRL1 mutation.

METHODS

We reviewed clinical, functional, and hemodynamic characteristics of 32 patients with PAH carrying an ACVRL1 mutation, corresponding to 9 patients from the French PAH Network and 23 from literature analysis. These cases were compared with 370 patients from the French PAH Network (93 with a bone morphogenetic protein receptor type 2 [BMPR2] mutation and 277 considered as idiopathic cases without identified mutation). Distribution of mutations in the ACVRL1 gene in patients with PAH was compared with the HHT Mutation Database.

MEASUREMENTS AND MAIN RESULTS

At diagnosis, ACVRL1 mutation carriers were significantly younger (21.8 +/- 16.7 yr) than BMPR2 mutation carriers and noncarriers (35.7 +/- 14.9 and 47.6 +/- 16.3 yr, respectively; P < 0.0001). In seven of the nine patients from the French PAH Network, PAH diagnosis preceded manifestations of HHT. ACVRL1 mutation carriers had better hemodynamic status at diagnosis, but none responded to acute vasodilator challenge and they had shorter survival when compared with other patients with PAH despite similar use of specific therapies. ACVRL1 mutations in exon 10 were more frequently observed in patients with PAH, as compared with what was observed in the HHT Mutation Database (33.3 vs. 5%; P < 0.0001).

CONCLUSIONS

ACVRL1 mutation carriers were characterized by a younger age at PAH diagnosis. Despite less severe initial hemodynamics and similar management, these patients had worse prognosis compared with other patients with PAH, suggesting more rapid disease progression.

Evaluation of imatinib mesylate in the treatment of pulmonary arterial hypertension

Imatinib mesylate is a small molecule inhibitor that selectively inhibits the PDGF receptor kinase as well the cKIT and Abl kinases, among other targets. Various studies have implicated the PDGF pathway in the pathogenesis of pulmonary arterial hypertension (PAH). Inhibition with imatinib mesylate has shown efficacy in human case reports and experimental models of PAH. Results from a Phase II trial of imatinib mesylate in PAH did not meet the primary end point but showed improvement in several secondary end points and in a subgroup analysis. As suggested by this study as well as a few case reports, imatinib may be effective in a subset of patients with more severe disease. However, this remains to be further validated through a Phase III study, which is already underway. In conclusion, it appears that imatinib mesylate may hold promise as an adjunct drug in PAH therapy, especially since it is directed at a pathway not previously targeted.