Medical therapy of pulmonary hypertension. The prostacyclins

Recent Developments in Nanomaterials-Based Drug Delivery and Upgrading Treatment of Cardiovascular Diseases

Cardiovascular diseases (CVDs) are the leading causes of morbidity and mortality worldwide. However, despite the recent developments in the management of CVDs, the early and long outcomes vary considerably in patients, especially with the current challenges facing the detection and treatment of CVDs. This disparity is due to a lack of advanced diagnostic tools and targeted therapies, requiring innovative and alternative methods. Nanotechnology offers the opportunity to use nanomaterials in improving health and controlling diseases. Notably, nanotechnologies have recognized potential applicability in managing chronic diseases in the past few years, especially cancer and CVDs. Of particular interest is the use of nanoparticles as drug carriers to increase the pharmaco-efficacy and safety of conventional therapies. Different strategies have been proposed to use nanoparticles as drug carriers in CVDs; however, controversies regarding the selection of nanomaterials and nanoformulation are slowing their clinical translation. Therefore, this review focuses on nanotechnology for drug delivery and the application of nanomedicine in CVDs.

Oral treprostinil in the treatment of pulmonary arterial hypertension

INTRODUCTION

Pulmonary arterial hypertension (PAH) is a rare disease resulting in progressive remodeling of the pulmonary vasculature and eventual right ventricular failure. Despite the development of 13 therapies for PAH since 2000, the use of continuously infused prostanoids retains a special role. Infused medications present unique challenges, and the search for an efficacious oral prostanoid culminated in the FDA approval of oral treprostinil - a first in class oral prostanoid medication approved to treat pulmonary arterial hypertension (PAH). Areas covered: In this discussion, we review the pharmacologic properties of oral treprostinil, and discuss three original major registration studies that resulted in the approval and widespread use of the drug. We also review several post-approval analyses and transitional studies. We discuss administration issues including side effects, transitioning, cost, and comparative analysis with selexipag. Expert opinion: Though the prospects of harnessing the benefits of continuously infused prostanoid therapy in a pill form are tantalizing, the gap in efficacy between oral and infused treatment is substantial. Major side effects and exorbitant cost are further barriers to broad uptake. Competition from oral prostaglandin receptor agonist selexipag challenges the commercial success of oral treprostinil. The long-term viability of oral treprostinil rests largely on the outcome of the long-term event-driven study of the molecule added to background approved ERA or PDE5 inhibitor monotherapy.

Chemical and biological assessment of metal organic frameworks (MOFs) in pulmonary cells and in an acute in vivo model: relevance to pulmonary arterial hypertension therapy

Pulmonary arterial hypertension (PAH) is a progressive and debilitating condition. Despite promoting vasodilation, current drugs have a therapeutic window within which they are limited by systemic side effects. Nanomedicine uses nanoparticles to improve drug delivery and/or reduce side effects. We hypothesize that this approach could be used to deliver PAH drugs avoiding the systemic circulation. Here we report the use of iron metal organic framework (MOF) MIL-89 and PEGylated MIL-89 (MIL-89 PEG) as suitable carriers for PAH drugs. We assessed their effects on viability and inflammatory responses in a wide range of lung cells including endothelial cells grown from blood of donors with/without PAH. Both MOFs conformed to the predicted structures with MIL-89 PEG being more stable at room temperature. At concentrations up to 10 or 30 µg/mL, toxicity was only seen in pulmonary artery smooth muscle cells where both MOFs reduced cell viability and CXCL8 release. In endothelial cells from both control donors and PAH patients, both preparations inhibited the release of CXCL8 and endothelin-1 and in macrophages inhibited inducible nitric oxide synthase activity. Finally, MIL-89 was well-tolerated and accumulated in the rat lungs when given in vivo. Thus, the prototypes MIL-89 and MIL-89 PEG with core capacity suitable to accommodate PAH drugs are relatively non-toxic and may have the added advantage of being anti-inflammatory and reducing the release of endothelin-1. These data are consistent with the idea that these materials may not only be useful as drug carriers in PAH but also offer some therapeutic benefit in their own right.

Targeting vascular (endothelial) dysfunction

Cardiovascular diseases are major contributors to global deaths and disability-adjusted life years, with hypertension a significant risk factor for all causes of death. The endothelium that lines the inner wall of the vasculature regulates essential haemostatic functions, such as vascular tone, circulation of blood cells, inflammation and platelet activity. Endothelial dysfunction is an early predictor of atherosclerosis and future cardiovascular events. We review the prognostic value of obtaining measurements of endothelial function, the clinical techniques for its determination, the mechanisms leading to endothelial dysfunction and the therapeutic treatment of endothelial dysfunction. Since vascular oxidative stress and inflammation are major determinants of endothelial function, we have also addressed current antioxidant and anti-inflammatory therapies. In the light of recent data that dispute the prognostic value of endothelial function in healthy human cohorts, we also discuss alternative diagnostic parameters such as vascular stiffness index and intima/media thickness ratio. We also suggest that assessing vascular function, including that of smooth muscle and even perivascular adipose tissue, may be an appropriate parameter for clinical investigations.

LINKED ARTICLES

This article is part of a themed section on Redox Biology and Oxidative Stress in Health and Disease. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.12/issuetoc.

Regio- and Stereocontrolled Dieckmann Approach to Treprostinil-Inspired, Polycyclic Scaffold For Building Macrocyclic Diversity

We developed a regio- and stereocontrolled Dieckmann cyclization approach to the synthesis of a novel, natural-product-like scaffold that was inspired from treprostinil (UT-15). This was further utilized in a diversity-based, 15-membered macrocyclic synthesis of two different sets of hybrid compounds. The amino acid moiety embedded in the macrocyclic skeleton allow exploring various chiral side chain groups within the ring.

Prostaglandin I2 signaling drives Th17 differentiation and exacerbates experimental autoimmune encephalomyelitis

Background

Prostaglandin I₂ (PGI₂), a lipid mediator currently used in treatment of human disease, is a critical regulator of adaptive immune responses. Although PGI₂ signaling suppressed Th1 and Th2 immune responses, the role of PGI₂ in Th17 differentiation is not known.

Methodology/Principal Findings

In mouse CD4⁺CD62L⁺ naïve T cell culture, the PGI₂ analogs iloprost and cicaprost increased IL-17A and IL-22 protein production and Th17 differentiation in vitro. This effect was augmented by IL-23 and was dependent on PGI₂ receptor IP signaling. In mouse bone marrow-derived CD11c⁺ dendritic cells (BMDCs), PGI₂ analogs increased the ratio of IL-23/IL-12, which is correlated with increased ability of BMDCs to stimulate naïve T cells for IL-17A production. Moreover, IP knockout mice had delayed onset of a Th17-associated neurological disease, experimental autoimmune encephalomyelitis (EAE), and reduced infiltration of IL-17A-expressing mononuclear cells in the spinal cords compared to wild type mice. These results suggest that PGI₂ promotes in vivo Th17 responses.

Conclusion

The preferential stimulation of Th17 differentiation by IP signaling may have important clinical implications as PGI₂ and its analogs are commonly used to treat human pulmonary hypertension.

Intravenous epoprostenol versus high dose inhaled iloprost for long-term treatment of pulmonary hypertension

BACKGROUND

Intravenous prostacyclin (iv PGI) and inhaled Iloprost (inh ilo) are established therapies in pulmonary arterial hypertension (PAH), however comparative data are lacking.

METHODS AND PATIENTS

We performed a long-term open label comparison trial of iv PGI or high dose inh ilo in 24 patients with severe PAH: 12 patients (9 female, 40 +/- 14 years, 10 idiopathic PAH, 2 PAH in connective tissue disease CTD) received iv PGI, whereas 12 patients (7 female, 43 +/- 12 years, 5 IPAH, 6 CTD, 1 porto-pulmonary hypertension) were commenced on inh ilo with a median dose of 120 μg/24 h. Haemodynamic parameters and 6 min walking distance (6MWD) at baseline did not differ between both groups.

RESULTS

After 3 months therapy, patients on iv PGI showed a significant increase in 6MWD from 220 to 280 m (p < 0.01), whereas patients on high dose inh ilo increased 6MWD from 200 to 275 m (p < 0.05). The event free follow up was 23 [1-76] months in the iv PGI2I group, and 16 [7-38] months in the high dose inh ilo group (p < 0.05). Patients with a 6MWD ≥ 300 m after 3 months therapy had a significantly longer event free follow up [16 vs. 35 months; p < 0.004].

CONCLUSION

In this patient population with severe pulmonary hypertension of different etiologies, event free follow up on treatment with iv PGI is significantly longer compared to high dose inh ilo. The 6MWD after 3 months treatment might be predictive for long term outcome.

Comparison of the usage of intravenous iloprost and nitroglycerin for pulmonary hypertension during valvular heart surgery

BACKGROUND

Pulmonary hypertension secondary to valvular heart disease is a cause of acute right heart failure during valve replacement operations. This study compares the hemodynamic effects of intravenous use of iloprost and nitroglycerin in patients with pulmonary hypertension undergoing valvular replacement surgery. We sought to determine the acceptable doses of these medications for use in surgery to decrease mean pulmonary artery pressure to <30 mmHg without causing systemic side effects. The plasma nitric oxide levels that were obtained from pulmonary mixed venous blood have been compared to demonstrate the difference in the action mechanism of these drugs.

METHODS

Eighteen patients undergoing mitral or aortic and mitral valvular replacement with pulmonary hypertension >25 mmHg were included in the study. The 2 groups received iloprost or nitroglycerin via a central pulmonary catheter, and the hemodynamic parameters were evaluated before incision (T1), 10 minutes after chest opening (T2), and 5 minutes and 20 minutes after cardiopulmonary bypass (T3 and T4). The plasma nitric oxide levels were obtained from the mixed venous blood at the T1 and T4 intervals.

RESULTS

The data have been analyzed for each group and for repeated measurements of hemodynamic parameters at T1-T4 time points. The analysis of hemodynamic parameters before (T1 and T2) and after (T3 and T4) bypass showed similar responses depending on the use of either iloprost or nitroglycerin. The administration of iloprost after bypass (T3) at a dosage of 1.25 to 2.5 ng/kg per minute reduced mean pulmonary artery pressure (from 28.8 +/- 7.89 to 20.63 +/- 6.39 mmHg) and pulmonary vascular resistance (from 226.88 +/- 101.93 to 118.00 +/- 82.36 dyn sec cm -5) better than nitroglycerin at a dosage of 0.5 to 1 microg/kg per minute (from 23.20 +/- 5.20 to 18.50 +/- 5.10 mmHg and from 160.80 +/- 39.76 to 137.40 +/- 56.54 dyn sec cm -5, respectively). Iloprost causes significant increase in cardiac output (from 4.91 +/- 0.91 to 5.49 +/- 0.91 L/min) compared to nitroglycerin (from 5.23 +/- 0.80 to 5.27 +/- 0.74 L/min). The plasma nitric oxide levels of the iloprost group did not show an increase from T1 to T4, whereas the nitroglycerin group levels did (P <.05).

CONCLUSIONS

Intravenous use of both iloprost and nitroglycerin effectively reduces mean pulmonary artery pressure, although only the iloprost group was accompanied by an increase in cardiac output. During operation, where abrupt management of pulmonary hypertension is required, systemic use of iloprost or nitroglycerin at appropriate doses via a pulmonary artery catheter offers adequate relief of hypertension and is well tolerated without any significant adverse effects. The plasma nitric oxide levels did not rise with the use of iloprost.

Systemic and localized scleroderma

Sclerosing conditions of the skin are manifested by a full spectrum of presentations that includes skin-limited forms as well as those which can involve internal organs and result in death. At this point, we are just beginning to understand the mechanisms of tissue fibrosis, and it is likely that the fibrotic processes are a heterogeneous group of disorders in which perturbation of multiple molecular pathways, including vascular and immunologically mediated pathways, can lead to fibrosis. We now have some moderately effective therapies for vascular aspects of systemic sclerosis (eg, bosentan for pulmonary arterial hypertension, calcium-channel blockers for Raynaud's, or angiotensin-converting enzyme inhibitors for renal crisis). We also are beginning to find treatments interrupting the immunologic pathways that manifest as systemic sclerosis (eg, methotrexate for the skin or cyclophosphamide for the lungs). The basic process of fibrosis, however, awaits proven, effective therapy.

Advances in the Medical Treatment of Pulmonary Hypertension

Increased pulmonary precapillary vascular resistance due to vasoconstriction and vasoproliferative processes is the basic pathophysiological mechanism in the development of pulmonary hypertension (PH). With the exception of pulmonary venous hypertension, where the primary cause of PH is left ventricular failure or mitral valvular disease, all the other PH categories will benefit to a greater or lesser extent from pulmonary vasodilator and antivasoproliferative therapy. Today, for this purpose, in addition to intravenous prostacyclin (epoprostenol), which is restricted to severe pulmonary arterial hypertension (NYHA class IV and late class III), other therapeutic options such as treatment with more stable prostacyclin analogs (oral beraprost, aerosolized iloprost), endothelin-receptor antagonists (bosentan) or phosphodiesterase inhibitors (sildenafil) are also available and these are especially useful for the treatment of the early stages of the disease. The recent progress in medical therapy has markedly increased the life expectancy in patients with pulmonary arterial hypertension and substantially improved their quality of life. Chronic hemodialysis (HD) patients show higher endothelin-1 (ET-1) activity in comparison to healthy individuals and there is evidence that the increase of pulmonary vascular resistance in these patients is at least in part mediated by ET-1. Recent data show good results after PH therapy with the endothelin-receptor antagonist bosentan in HD patients. Also prostacyclin and its analogs, as well as phosphodiesterase inhibitors, can be useful for the treatment of pulmonary hypertension in patients with chronic renal failure.

Cost-minimization analysis of treprostinil vs. epoprostenol as an alternate to oral therapy non-responders for the treatment of pulmonary arterial hypertension

INTRODUCTION

Idiopathic pulmonary arterial hypertension (IPAH) is associated with substantial morbidity and mortality. Treprostinil was compared to epoprostenol for the economic impact of treating IPAH patients who failed or were not candidates for bosentan.

METHODS

The model was a cost-minimization analysis, assuming clinical equivalence was achieved by proper dosing of both drugs, in terms of survival and surrogate measures. Two theoretical cohorts of 270 patients were treated with subcutaneous treprostinil and intravenous epoprostenol, and were evaluated over 3 years using a spreadsheet model. Annual survival rates were estimated for the cohorts so that at endpoint 114 (42%) patients survived in both groups. The model utilized resource valuation data for medication and supply costs from Medicare; hospital, consultation, surgical, and diagnostic procedural fees from North Carolina hospitals; and costs to treat adverse events from published sources. Costs were obtained from standard lists and were presented as 2003 US dollars, discounted at 3%. Sensitivity analyses were performed testing all model uncertainties.

RESULTS

In the base case analysis, treprostinil demonstrated savings of 22,701 US dollars and 37,433 US dollars per patient over 1- and 3-year time horizons, respectively. The greatest savings came from reduced or minimal hospitalizations attributed to the dose titration and treatment of adverse events, such as sepsis, associated with epoprostenol and its delivery system. Probabilistic sensitivity analyses resulted in average 3-year cost-savings of 41,051 US dollars (Standard Deviation = 13,902 US dollars) per patient.

CONCLUSIONS

By initiating and continuing treatment with treprostinil over a 3-year period, the economic burden associated with IPAH may be reduced compared to treatment with epoprostenol. The greatest saving with treprostinil was attributed to decreased sepsis.

Efficacy and optimal dose of sildenafil in primary pulmonary hypertension

PURPOSE

We aimed to assess the effects of sildenafil and evaluate optimal dosing in primary pulmonary hypertension (PPH). Sildenafil selectively inhibits phosphodiesterase 5 (PDE5), which is abundant in pulmonary and penile tissue. This results in increasing nitric oxide (NO) at tissue level leading to pulmonary vasodilatation.

SUBJECTS AND METHODS

Our study was a prospective study of sildenafil in 15 consecutive patients with severe symptomatic PPH of NYHA class III-IV. All patients were stabilized for a minimum period of 5 days with antifailure medications. Sildenafil was started at 50 mg twice daily for 4 weeks and increased to 100 mg bid for 4 more weeks in a step-up protocol. Primary end-points were change in Borg dyspnea index, NYHA class and 6-min walk distance, estimated at baseline 1, 2, 4 and 8 weeks.

RESULTS

NYHA class (baseline 3.8 +/- 0.4 vs. 4 weeks 2.4 +/- 0.5, p = 0.002), Borg dyspnea index (8.1 +/- 1.7 vs. 4.4 +/- 1.9, p = 0.0007), 6-min walk distance (234 +/- 44 vs. 377 +/- 128 m, p = 0.001) and Pulmonary artery pressure (125 +/- 15 vs. 113 +/- 18 mm Hg p = 0.05) are significantly improved with sildenafil 50 mg bid at 4 weeks. Increasing the dose to 100 mg bid did not produce further benefit. Echocardiography parameters of right heart dimensions and functions did not change markedly in the study period.

CONCLUSION

Sildenafil is well tolerated with no adverse effects in severe pulmonary hypertension. It reduces symptoms, improves effort tolerance and controls refractory heart failure significantly by 2 weeks in 70% of patients at 50 mg twice daily. Three patients (20%) failed to respond with sildenafil.

Effects of Long-Term Bosentan in Children With Pulmonary Arterial Hypertension

OBJECTIVES

This study investigated the long-term outcome of children with pulmonary arterial hypertension (PAH) treated with bosentan therapy, with or without concomitant prostanoid therapy.

BACKGROUND

Bosentan, an oral endothelin ET(A)/ET(B) receptor antagonist, improves hemodynamics and exercise capacity in adults with PAH; however, limited data are available on its long-term effects in children.

METHODS

In this retrospective study, 86 children with PAH (idiopathic, associated with congenital heart or connective tissue disease) started bosentan with or without concomitant intravenous epoprostenol or subcutaneous treprostinil therapy. Hemodynamics, World Health Organization (WHO) functional class, and safety data were collected.

RESULTS

At the cutoff date, 68 patients (79%) were still treated with bosentan, 13 (15%) were discontinued, and 5 (6%) had died. Median exposure to bosentan was 14 months. In 90% of the patients (n = 78), WHO functional class improved (46%) or was unchanged (44%) with bosentan treatment. Mean pulmonary artery pressure and pulmonary vascular resistance decreased (64 +/- 3 mm Hg to 57 +/- 3 mm Hg, p = 0.005 and 20 +/- 2 U x m2 to 15 +/- 2 U x m2, p = 0.01, respectively; n = 49). Kaplan-Meier survival estimates at one and two years were 98% and 91%, respectively. The risk for worsening PAH was lower in patients in WHO functional class I/II at bosentan initiation than in patients in WHO class III/IV at bosentan initiation.

CONCLUSIONS

These data suggest that bosentan, an oral endothelin ET(A)/ET(B) receptor antagonist, with or without concomitant prostanoid therapy, is safe and efficacious for the treatment of PAH in children.

Correlation between Right Ventricular Indices and Clinical Improvement in Epoprostenol Treated Pulmonary Hypertension Patients

The aim of this study was to evaluate which parameter of right ventricular (RV) echocardiographic best mirrors the clinical status of patients with pulmonary arterial hypertension. Patients with pulmonary arterial hypertension on epoprostenol therapy were identified via hospital registry. Twenty patients, (16 females, 4 males) were included in the study, 9 with primary pulmonary hypertension and 11 with other diseases. Echocardiograms before therapy and at 22.7 (+/-9.3) months into therapy were compared. The right ventricular myocardial performance index (RVMPI) was measured as the sum of the isometric contraction time and the isometric relaxation time divided by right ventricular ejection time. Other measures included peak tricuspid regurgitation jet velocity (TRV), pulmonary artery systolic pressure (PASP), pulmonary valve velocity time integral (PVVTI), PASP/PVVTI (as an index of total pulmonary resistance) and symptoms by New York Heart Association (NYHA) functional class. Echo parameters of right ventricular function were analyzed in patients, before and during therapy. There was significant improvement of NYHA class in patients following epoprostenol therapy (P < 0.0001). Peak tricuspid regurgitant jet velocity (pre 4.2 +/- 0.6 m/sec, post 3.8 +/- 0.7 m/sec, P = 0.02) and PASP/PVVTI (pre 6.7 +/- 3.3 mmHg/m per second, post 4.8 +/- 2.2 mmHg/m per second, P < 0.0001) were significantly improved during treatment. RVMPI did not improve (pre 0.6 +/- 0.3, post 0.6 +/- 0.3, P = 0.54). Changes in NYHA class did not correlate with changes in RVMPI (P = 0.33) or changes in PASP/PVVTI (P = 0.58). Despite significant improvements in TRV, PASP/PVVTI, and NYHA class, there was no significant change in RVMPI on epoprostenol therapy. Changes in right ventricular indices were not correlated with changes in NYHA class.

Staggered Transition to Epoprostenol from Treprostinil in Pulmonary Arterial Hypertension

OBJECTIVE:

To describe a successful transition process from subcutaneous treprostinil to intravenous epoprostenol after the failure of treprostinil in a patient with idiopathic pulmonary arterial hypertension and present an algorithm to achieve the conversion without significant adverse reactions.

CASE SUMMARY:

A 25-year-old white female receiving subcutaneous treprostinil 97 ng/kg/min was admitted to the intensive care unit for transition from subcutaneous treprostinil to a target intravenous epoprostenol dose of 72 ng/kg/min via a staggered interval dose adjustment approach. The patient experienced facial flushing, hot flashes, and headache when dose adjustments of the drugs were made simultaneously; however, when dose adjustments were staggered, the adverse reactions did not occur and larger adjustments could be achieved.

DISCUSSION:

This case demonstrates a suboptimal therapeutic response to treprostinil for the treatment of idiopathic pulmonary arterial hypertension. The transition of treprostinil to epoprostenol is rare; however, in the event therapy change is needed, dosing information is minimal. A staggered transition dosing regimen that accounts for the pharmacokinetic differences between epoprostenol and treprostinil was successfully used in this case.

CONCLUSIONS:

The approach in this case demonstrates the success of staggered-interval dose adjustments to minimize supratherapeutic symptoms and coincides with the pharmacokinetic profile of the 2 medications.

Endothelin and pulmonary arterial hypertension

BACKGROUND AND OBJECTIVES

Pulmonary arterial hypertension (PHT) is a potentially fatal disease. The purpose of this article is to review the current knowledge of the role played by endothelin (ET) in PHT and the relevant drug regimens used in the treatment of this condition.

METHODS

A detailed search via MEDLINE (PubMed) was performed by using PHT and ET as the key terms.

RESULTS

PHT could be a primary or a secondary diagnosis associated with various heart and lung diseases. PHT appears during the late stage of systemic sclerosis and may complicate other systemic diseases such as systemic lupus erythematosus. The vascular endothelium and activation of various mediators and growth factors such as the ET system are thought to play a crucial role in the development of this condition. The pathologic process progresses very rapidly from vasoconstriction to widespread pulmonary vascular obstruction. The use of high doses of calcium channel blockers is of limited value. Life-long anticoagulant therapy is recommended for the treatment of PHT. Currently, the drug being used in PHT therapy is continuous central-venous prostacyclin infusion. Prostacyclin is a strong vasodilator with antiaggregate and antifibrotic properties and has the potential to reduce endothelial injury and to induce vasculature remodeling. This treatment results in improved functional status and increased life span. Unfortunately, its use is accompanied by various side effects, technical difficulties, and high cost. The role of other therapeutic modalities (inhaled prostacyclin, subcutaneous treprostinil, oral beraprost, sildenafil) in vascular remodeling, and the improvement in functional capacity and survival of patients with PHT, are currently under investigation. Bosentan, administered orally, is a recently developed active ET receptor antagonist. It is a promising new therapeutic tool in the treatment of PHT because of its potent vasodilator, antiproliferative, and vascular remodeling activity.

CONCLUSIONS

The revolutionary conceptual shift in understanding the pathogenesis of PHT from a vasoconstrictive process to a vasoproliferative one, has led to a modification in the treatment of this disease from the use of vasodilators to the use of drugs with antiproliferative and vascular remodeling activity. Until now, prostacyclin was the only drug of this type available for the treatment of PHT. ET blockade seems to be a reasonable and potential therapeutic option.

Signaling through the prostaglandin I2 receptor IP protects against respiratory syncytial virus-induced illness

The role of prostanoids in modulating respiratory syncytial virus (RSV) infection is unknown. We found that RSV infection in mice increases production of prostaglandin I(2) (PGI(2)). Mice that overexpress PGI(2) synthase selectively in bronchial epithelium are protected against RSV-induced weight loss and have decreased peak viral replication and gamma interferon levels in the lung compared to nontransgenic littermates. In contrast, mice deficient in the PGI(2) receptor IP have exacerbated RSV-induced weight loss with delayed viral clearance and increased levels of gamma interferon in the lung compared to wild-type mice. These results suggest that signaling through IP has antiviral effects while protecting against RSV-induced illness and that PGI(2) is a potential therapeutic target in the treatment of RSV.

Diagnosis of pulmonary vascular limit to exercise by cardiopulmonary exercise testing

BACKGROUND

Given the recent development of newer and less-invasive treatments for pulmonary hypertension, and the long wait for lung transplantation, early and correct diagnosis of this condition is increasingly important. The purpose of this study was to determine and improve the accuracy of a non-invasive, cardiopulmonary exercise-testing algorithm for detecting a pulmonary vascular limit to exercise.

METHODS

We performed 130 consecutive, incremental cycling-exercise tests for exertional symptoms with pulmonary and radial artery catheters in place. Pulmonary vascular limit was defined as pulmonary vascular resistance at maximum exercise >120 dynes. sec/cm(5) and a peak-exercise systemic oxygen delivery <80% predicted, without a pulmonary mechanical limit or poor effort. We applied a previously reported non-invasive exercise-test-interpretation algorithm to each patient and sequentially manipulated branch point threshold values to maximize accuracy.

RESULTS

The sensitivity of the original non-invasive algorithm for pulmonary vascular limit was 79%, specificity was 75%, and accuracy was 76%. Sensitivity did not change with systematic alteration of branch-point threshold values, but specificity and accuracy improved to 88% and 85%, respectively. Accuracy improved most by modifying the threshold values for percent predicted maximum oxygen uptake and carbon dioxide output ventilatory equivalents at lactate threshold.

CONCLUSION

Non-invasive cardiopulmonary exercise testing is a useful tool for detecting and excluding a pulmonary vascular limit and for determining whether abnormal pulmonary hemodynamics limit aerobic capacity.

Clinical value of vasodilator test with inhaled nitric oxide for predicting long-term response to oral vasodilators in pulmonary hypertension

Acute vasodilator tests with prostacyclin (PGI2) or inhaled nitric oxide (iNO) are used to select patients with pulmonary arterial hypertension (PAH) who should be treated with oral vasodilators. The haemodynamic effects of PGI2 and iNO are different, and the limits for considering a vasodilator response as significant are controversial. The study was aimed to investigate the diagnostic performance of acute vasodilator testing with iNO and PGI2 in predicting the clinical outcome after 1 year treatment with oral vasodilators. Twenty-seven patients with severe PAH were studied. Nineteen patients were treated with oral vasodilators and their outcome after 1 year was qualified as favourable or unfavourable. The diagnostic performance of vasodilator tests in predicting this outcome was evaluated using receiver operating characteristics (ROC) curves. The acute effects of iNO and PGI2 on pulmonary artery pressure (PAP) were similar. By contrast, PGI2 produced more marked changes on cardiac output and pulmonary vascular resistance than iNO (P<0.05). The evolution at 1 year was favourable in 11 patients and unfavourable in 8. Patients with favourable evolution showed greater decrease of PAP with iNO than with PGI2 (P<0.05). The decrease of PAP with iNO had the greatest predictive value on the clinical outcome (area under ROC curve, 0.83). We conclude that in patients with PAH, acute vasodilator testing with iNO is preferable to PGI2 because it reflects more consistently the changes in pulmonary vascular tone. The acute decrease of PAP with iNO is the best predictor of the long-term response to oral vasodilator treatment.

Paradoxical increase of pulmonary vascular resistance during testing of inhaled iloprost

The case of a 14 month old girl with primary pulmonary hypertension treated with domiciliary oxygen is described. After invasive evaluation and testing of nitric oxide with very good response, the testing was repeated to study the effect of inhaled iloprost on pulmonary vascular resistance (PVR). An unexpected and severe increase of PVR was observed, rising from 392 dynes x s x cm(-5) with oxygen to a maximum of 1192 dynes x s x cm(-5) with oxygen and iloprost. Underlying ventilatory and technical problems were excluded. While inhaled iloprost has been described to be highly effective in the treatment of primary pulmonary hypertension, the possibility of contrary "paradoxical" reactions in isolated patients is emphasised, with a dramatic increase of PVR and a possible adverse outcome.

Inhaled iloprost in patients with chronic thromboembolic pulmonary hypertension: effects before and after pulmonary thromboendarterectomy

BACKGROUND

In primary pulmonary hypertension, aerosolized prostanoids selectively reduce pulmonary vascular resistance and improve right ventricular function. In this study, hemodynamic effects of inhaled iloprost, a stable prostacyclin analogue, were evaluated in patients with chronic thromboembolic pulmonary hypertension (CTEPH) before and early after pulmonary thromboendarterctomy (PTE).

METHODS

Ten patients (mean age 49 years old [32 to 70 years old], New York Heart Association functional class III and IV) received a dose of 33 micro g aerosolized iloprost immediately before surgery (T1), after intensive care unit admission (T2), and 12-hours postoperatively (T3). Effects on pulmonary and systemic hemodynamics and gas exchange were recorded and compared with preinhalation baseline values.

RESULTS

Preoperatively, inhaled iloprost did not significantly change mean pulmonary artery pressure (mPAP), cardiac index (CI), or pulmonary vascular resistance (PVR). Postoperatively, inhaled iloprost induced a significant reduction of mPAP and PVR and a significant increase of CI at T2 and T3. Preinhalation versus postinhalation PVR was as follows: at T1, 847 versus 729 dynes. s. cm(-5), p = 0.45; at T2, 502 versus 316 dynes. s. cm(-5), p = 0.008; and at T3, 299 versus 227 dynes. s. cm(-5), p = 0.004.

CONCLUSIONS

In patients with CTEPH, inhalation of iloprost elicits no significant pulmonary vasodilation before surgery, and may have detrimental effects on systemic hemodynamics. Postoperatively, it significantly reduces mPAP and PVR, and enhances CI. Following PTE, inhalation of iloprost is useful to improve early postoperative hemodynamics.

Update on disease-modifying antirheumatic drugs in the treatment of systemic sclerosis

Treatment of systemic sclerosis has been somewhat haphazard and treatment has often been "borrowed" from the experience gained from treating other connective tissue diseases. There was a period of time that was focused mainly on organ-specific manifestations of systemic sclerosis and some advance in preventing vital organ damage (such as renal crisis) was achieved. The vast improvement in mortality from the use of ACE inhibitors raises one's hopes for other effective therapeutic interventions. At this juncture, the evidence is strong that the ACE inhibitors that are used in scleroderma renal crisis are disease-modifying, even without proving it by a randomized controlled trial. The evidence is strong that the use of epoprostenol for primary pulmonary hypertension is life-saving; however, whether epoprostenol is life-saving in the pulmonary hypertension in scleroderma remains to be proven. There are suggestions that bosentan (for the pulmonary hypertension of scleroderma), cyclophosphamide (for SSc alveolitis), stem cell transplant, interferon-gamma (for interstitial pulmonary fibrosis), and methotrexate (for the skin thickening of diffuse scleroderma) may improve organ function or functional activities, but whether they are truly disease-modifying remains to be proven. As we increase our understanding of the pathophysiology of systemic sclerosis and we learn how better to design trials for systemic sclerosis, we may be more successful in developing optimal disease-modifying therapy. Although the treatment of systemic sclerosis remains difficult, there are an increasing number of potentially effective regimens that are undergoing clinical investigations. A rational approach to therapy seems possible, based on a hypothesis of the pathogenesis of systemic sclerosis. Thus, there is accumulating evidence that supports the use of prostacyclin derivatives to treat systemic sclerosis, some evidence that antifibrotic regimens may be effective, and moderate evidence that immunosuppression also may be effective in certain stages of this disease.

Emerging medical therapies for pulmonary arterial hypertension

Until a few years ago, "conventional" treatment for pulmonary arterial hypertension (PAH) included oral anticoagulants, calcium channel blockers, diuretics, digoxin, and oxygen. In the 1990s, 3 randomized studies demonstrated that the continuous intravenous infusion of epoprostenol improved functional capacity, cardiopulmonary hemodynamics, and survival in patients with severe PAH. Recently, the thromboxane inhibitor terbogrel, the prostacyclin analogues treprostinil, beraprost, and iloprost, and the endothelin receptor antagonist bosentan have been tested in clinical trials in more than 1,100 patients. Except for terbogrel, all compounds have improved by different degrees the mean exercise capacity as assessed by 6 minutes walking distance. Conversely, these trials differ for the severity and etiology of included PAH patients as well as for the effects on combined clinical events, on quality of life, and on hemodynamics. No trials have shown effects on mortality, and each new compound presents different side effects that seem unpredictable in the individual patient. At present, additional new compounds such as sitaxentan, ambisentan, L-arginine, and sildenafil are studied in clinical trials. The new therapeutic options are currently in different phases of approval by regulatory agencies, and when they will become available we will have the opportunity to select the most appropriate treatment for the single patient, according to an individualized benefit-to-risk ratio.

Current and emerging therapy for primary pulmonary hypertension

OBJECTIVE

To review the epidemiology, pathophysiology, clinical symptoms, and diagnostic workup of primary pulmonary hypertension (PPH) and to discuss the available data on the current and emerging therapies being used to treat this disorder.

DATA SOURCES

Primary and review articles were identified with a MEDLINE search (1966-December 2001) and through secondary sources.

STUDY SELECTION AND DATA EXTRACTION

All articles identified from the data sources were evaluated and all information deemed relevant was included in this review.

DATA SYNTHESIS

In the absence of a definable cause, PPH is a disorder classified by a progressive increase in pulmonary vascular resistance and mean pulmonary artery pressure. A relatively rare condition, PPH has an annual incidence of 1-2 cases per million people, slightly higher in women than men. The prognosis is poor, with a mean survival time of 2.8 years after diagnosis if untreated. Vasoconstriction, vascular remodeling, and thrombosis are hallmarks of the disease process. Anticoagulation and vasodilators are the most commonly employed treatment options, showing benefits in clinical outcomes, hemodynamic parameters, and mortality. Several new vasodilators are being evaluated for the treatment of PPH. Bosentan was recently approved as the first oral agent for the treatment of PPH. Iloprost, treprostinil, and beraprost are investigational agents in Phase III studies.

CONCLUSIONS

Until additional studies and experience with these agents become available, calcium-channel blockers (CCBs) remain the first option for therapy. For patients not responding to CCBs, therapeutic options will now include epoprostenol and bosentan. Since there are no comparison trials between these 2 agents, therapeutic decisions should be based on patient-specific concerns. Clinical data and experience support the use of epoprostenol; however, in patients at risk or considered unsuitable candidates, bosentan may become a preferred option. Additional studies are warranted to address the potential therapeutic benefits of combination therapy and long-term benefits of agents to treat PPH.