Effects of long-term infusion of prostacyclin on exercise performance in patients with primary pulmonary hypertension

Intravenous prostacyclin-analogue therapy in pulmonary arterial hypertension - A review of the past, present and future

Therapy with intravenous prostacyclin analogues in patients with pulmonary arterial hypertension (PAH) has been established for decades and is an integral component of the current guidelines for the treatment of pulmonary hypertension. Initially, these drugs were infused by external pump systems via tunnelled right atrial catheters with the need for cooling and frequent exchange of drug reservoirs. Associated complications included, among others, catheter-related infections. More recently, fully implantable pump systems have been developed with drug reservoirs that are filled transcutaneously, allowing intervals between refills of several weeks. This technique results in a low rate of infections. Epoprostenol, iloprost and treprostinil have all been used intravenously in PAH, but titration, dosing and dose escalation in long-term therapy are not standardized. Intravenous prostacyclin analogues are still under-used, despite available data suggesting that early and broad application of these therapies as part of risk-oriented, guideline-directed combination therapy for patients with PAH may lead to a survival benefit. This review provides a detailed overview of the drugs, infusion systems and dosing strategies used for intravenous therapy in patients with PAH.

[Current Aspects of Definition and Diagnosis of Pulmonary Hypertension]

At the 6th World Symposium on Pulmonary Hypertension (WSPH), which took place from February 27 until March 1, 2018 in Nice, scientific progress over the past 5 years in the field of pulmonary hypertension (PH) was presented by 13 working groups. The results of the discussion were published as proceedings towards the end of 2018. One of the major changes suggested by the WSPH was the lowering of the diagnostic threshold for PH from ≥ 25 to > 20 mmHg mean pulmonary arterial pressure, measured by right heart catheterization at rest. In addition, the pulmonary vascular resistance was introduced into the definition of PH, which underlines the importance of cardiac output determination at the diagnostic right heart catheterization.In this article, we discuss the rationale and possible consequences of a changed PH definition in the context of the current literature. Further, we provide a current overview on non-invasive and invasive methods for diagnosis, differential diagnosis, and prognosis of PH, including exercise tests.

Sex-specific cardiopulmonary exercise testing indices related to hemodynamics in idiopathic pulmonary arterial hypertension

Background:

Many studies have highlighted sex preponderance in idiopathic pulmonary arterial hypertension (IPAH). It is well established that there are differences in exercise capacities in the two sexes but how much of that difference reflects on disease severity or correlates to markers of severity in the two sexes is still not clear. Right heart catheterization (RHC) and cardiopulmonary exercise testing (CPET) have been widely used for assessing functional capacity, prognosis and treatment response in IPAH. We aimed to investigate the ‘sex-specific’ CPET parameters in relation to hemodynamics in IPAH.

Methods:

Data were retrieved from 30 males and 53 females [mean ± standard deviation (SD) age: 39.6 ± 17.2 and 37.5 ± 12.0] stable IPAH patients who underwent both RHC and CPET at Shanghai Pulmonary Hospital from 2010 to 2016. Univariate and forward/backward multiple stepwise regression analysis was performed to assess the prognostic value of CPET and hemodynamic parameters.

Results:

There were no significant differences in clinical variables between men and women. Peak workload, peak oxygen uptake, anaerobic threshold (AT), peak minute ventilation, carbon dioxide output, O₂ pulse and oxygen uptake efficiency slope were significantly higher in men compared with women (p < 0.05). Several CPET indexes correlated with hemodynamics. Pulmonary vascular resistance (PVR) and cardiac output (CO) were distinctly different between the sexes. Peak end-tidal partial pressure of CO₂ (P_ETCO₂) was an independent predictor of PVR elevation in all patients and in men. Peak maximum oxygen consumption (VO₂) was independently predictive of CO decline in all patients and in men. Only peak O₂ pulse was an independent predictor of increased PVR and decreased CO in women.

Conclusions:

Even after adjusting for age, body mass index and World Health Organization functional class, different CPET parameters correlated with PVR elevation and CO decline in men and women differently, which could potentially better predict severity in men and women with IPAH.

Effects of chronic nitric oxide synthase inhibition on V'O2max and exercise capacity in mice

Acute inhibition of NOS by L-NAME (N^ω-nitro-L-arginine methyl ester) is known to decrease maximal oxygen consumption (V'O_2max) and impair maximal exercise capacity, whereas the effects of chronic L-NAME treatment on V'O_2max and exercise performance have not been studied so far. In this study, we analysed the effect of L-NAME treatment, (LN2 and LN12, respectively) on V'O_2max and exercise capacity (in maximal incremental running and prolonged sub-maximal incremental running tests), systemic NO bioavailability (plasma nitrite (NO₂^-) and nitrate (NO₃^-)) and prostacyclin (PGI₂) production in C57BL6/J mice. Mice treated with L-NAME for 2 weeks (LN2) displayed higher V'O_2max and better running capacity than age-matched control mice. In LN2 mice, NO bioavailability was preserved, as evidenced by maintained NO₂^- plasma concentration. PGI₂ production was activated (increased 6-keto-PGF_1α plasma concentration) and the number of circulating erythrocytes (RBC) and haemoglobin concentration were increased. In mice treated with L-NAME for 12 weeks (LN12), NO bioavailability was decreased (lower NO₂^- plasma concentration), and 6-keto-PGF_1α plasma concentration and RBC number were not elevated compared to age-matched control mice. However, LN12 mice still performed better during the maximal incremental running test despite having lower V'O_2max. Interestingly, the LN12 mice showed poorer running capacity during the prolonged sub-maximal incremental running test. To conclude, short-term (2 weeks) but not long-term (12 weeks) treatment with L-NAME activated robust compensatory mechanisms involving preservation of NO2- plasma concentration, overproduction of PGI₂ and increased number of RBCs, which might explain the fully preserved exercise capacity despite the inhibition of NOS.

Use of exercise testing in the evaluation of interventional efficacy: an official ERS statement

This document reviews 1) the measurement properties of commonly used exercise tests in patients with chronic respiratory diseases and 2) published studies on their utilty and/or evaluation obtained from MEDLINE and Cochrane Library searches between 1990 and March 2015.

Exercise tests are reliable and consistently responsive to rehabilitative and pharmacological interventions. Thresholds for clinically important changes in performance are available for several tests. In pulmonary arterial hypertension, the 6-min walk test (6MWT), peak oxygen uptake and ventilation/carbon dioxide output indices appear to be the variables most responsive to vasodilators. While bronchodilators do not always show clinically relevant effects in chronic obstructive pulmonary disease, high-intensity constant work-rate (endurance) tests (CWRET) are considerably more responsive than incremental exercise tests and 6MWTs. High-intensity CWRETs need to be standardised to reduce interindividual variability. Additional physiological information and responsiveness can be obtained from isotime measurements, particularly of inspiratory capacity and dyspnoea. Less evidence is available for the endurance shuttle walk test. Although the incremental shuttle walk test and 6MWT are reliable and less expensive than cardiopulmonary exercise testing, two repetitions are needed at baseline. All exercise tests are safe when recommended precautions are followed, with evidence suggesting that no test is safer than others.

Lung function in pulmonary hypertension

Breathlessness is a common symptom in pulmonary hypertension (PH) and an important cause of morbidity. Though this has been attributed to the well described pulmonary vascular abnormalities and subsequent cardiac remodelling, changes in the airways of these patients have also been reported and may contribute to symptoms. Our understanding of these airway abnormalities is poor with conflicting findings in many studies. The present review evaluates these studies for the major PH groups. In addition we describe the role of cardiopulmonary exercise testing in the assessment of pulmonary arterial hypertension (PAH) by evaluating cardiopulmonary interaction during exercise. As yet, the reasons for the abnormalities in lung function are unclear, but potential causes and the possible role of inflammation are discussed. Future research is required to provide a better understanding of this to help improve the management of these patients.

Effects of 1-Methylnicotinamide (MNA) on Exercise Capacity and Endothelial Response in Diabetic Mice

1-Methylnicotinamide (MNA), which was initially considered to be a biologically inactive endogenous metabolite of nicotinamide, has emerged as an anti-thrombotic and anti-inflammatory agent with the capacity to release prostacyclin (PGI2). In the present study, we characterized the effects of MNA on exercise capacity and the endothelial response to exercise in diabetic mice. Eight-week-old db/db mice were untreated or treated with MNA for 4 weeks (100 mg·kg-1), and their exercise capacity as well as NO- and PGI2-dependent response to endurance running were subsequently assessed. MNA treatment of db/db mice resulted in four-fold and three-fold elevation of urine concentrations of MNA and its metabolites (Met-2PY + Met-4PY), respectively (P<0.01), but did not affect HbA1c concentration, fasting glucose concentration or lipid profile. However, insulin sensitivity was improved (P<0.01). In MNA-treated db/db mice, the time to fatigue for endurance exercise was significantly prolonged (P<0.05). Post-exercise Δ6-keto-PGF1α (difference between mean concentration in the sedentary and exercised groups) tended to increase, and post-exercise leukocytosis was substantially reduced in MNA-treated animals. In turn, the post-exercise fall in plasma concentration of nitrate was not affected by MNA. In conclusion, we demonstrated for the first time that MNA improves endurance exercise capacity in mice with diabetes, and may also decrease the cardiovascular risk of exercise.

Coronary and muscle blood flow during physical exercise in humans; heterogenic alliance

In this review, we present the relation between power generation capabilities and pulmonary oxygen uptake during incremental cycling exercise in humans and the effect of exercise intensity on the oxygen cost of work. We also discuss the importance of oxygen delivery to the working muscles as a factor determining maximal oxygen uptake in humans. Subsequently, we outline the importance of coronary blood flow, myocardial oxygen uptake and myocardial metabolic stability for exercise tolerance. Finally, we describe mechanisms of endothelium-dependent regulation of coronary and skeletal muscle blood flow, dysregulation of which may impair exercise capacity and increase the cardiovascular risk of exercise.

Medical therapeutics for pulmonary arterial hypertension: from basic science and clinical trial design to evidence-based medicine

Pulmonary arterial hypertension is a severe disease with poor prognosis, caused by obliteration of the pulmonary vasculature as a result of pulmonary-vascular remodeling, active vasoconstriction and in situ thrombosis. Left untreated, pulmonary arterial hypertension results in right-ventricular failure and death. There has been dramatic progress in the treatment of pulmonary arterial hypertension during recent years. A remarkable number of randomized-controlled trials with agents known to target specific abnormalities present in pulmonary arterial hypertension have been completed. Most commonly, therapeutic efficacy was judged by the ability of the drug under study to improve exercise capacity and to decrease the rate of severe complications. Completed clinical trials have mainly evaluated patients with relatively advanced disease. Despite these advances, responses to therapy in pulmonary arterial hypertension are not uniformly favorable and frequently incomplete. In addition, the methods of delivery and the adverse effect profile of the currently available pulmonary arterial hypertension-specific drugs create further management difficulties. Based on newly identified pathobiologic abnormalities in the pulmonary vasculature, future studies are likely to focus on the discovery of new therapeutic targets. Clinical trial design will continue to evolve in an attempt to enable inclusion of patients with less advanced disease and evaluation of treatment combinations or comparisons of the currently approved drugs.

Diagnosis of pulmonary arterial hypertension

Accurate diagnosis of pulmonary arterial hypertension can be challenging and often requires a high index of clinical suspicion. Use of a variety of noninvasive tests can help define the population of patients in whom invasive cardiac catheterization should be pursued. An understanding of the historical, physical exam, electrocardiographic, radiographic, and echocardiographic clues in the diagnosis is important. A ventilation-perfusion scan and careful assessment for left-to-right shunting are mandatory to avoid missing reasons for pulmonary hypertension that may require nonpharmacologic management. Right heart, and sometimes concomitant left heart, catheterization is required to establish the diagnosis and distinguish pulmonary arterial from pulmonary venous hypertension.

Prognostic relevance of changes in exercise test variables in pulmonary arterial hypertension

INTRODUCTION

Exercise variables determined in patients with pulmonary arterial hypertension (PAH) at the time of diagnosis, predict survival. It is unknown whether upon treatment, subsequent changes in these exercise variables reflect improvements in survival. The aim of this study was to determine changes in exercise variables in PAH patients and to relate these changes to survival.

METHODS

Baseline cardiopulmonary exercise test (CPET) variables and six-minute-walk-distance (6MWD) were available from 65 idiopathic PAH patients (50 females; mean age 45±2yrs). The same variables were determined after treatment (13months) in a sub group of 43 patients. To estimate the association between changes in exercise variables and changes in cardiac function, right-ventricle ejection fraction (RVEF) was measured by cardiac MRI at baseline and after treatment in 34 patients. Mean follow-up time after the second CPET was 53 (range: 4-111) months. Kaplan-Meier analysis was used to relate survival to baseline and treatment-associated changes in exercise variables.

RESULTS

Survivors showed a significantly greater change in maximal oxygen uptake than non-survivors and this change in aerobic capacity was significantly related to changes in RVEF. From baseline until the end of the study period, two patients underwent a lung transplantation and 19 patients died. Survival analysis showed that baseline 6MWD (p<0.0001), maximal heart rate (p<0.0001) and the slope relating ventilation with carbon dioxide production (p≤0.05) were significant predictors of survival, whereas baseline oxygen uptake and oxygen pulse held no predictive value. Treatment associated changes in 6MWD (p<0.01), maximal heart rate (p<0.05), oxygen uptake (p<0.001) and oxygen pulse predicted survival (p<0.05), whereas changes in the slope relating ventilation with carbon dioxide production did not.

CONCLUSION

Exercise variables with prognostic significance when determined at baseline, retain their prognostic relevance after treatment. However, when changes in exercise variables upon treatment are considered, a different set of variables provides prognostic information.

Screening and treating pulmonary arterial hypertension in a tertiary hospital-based multidisciplinary clinic: the first 200 patients

BACKGROUND

Pulmonary arterial hypertension (PAH) is an increasingly recognised serious illness with insidious onset, delayed diagnosis, complex diagnostic algorithms and poor prognosis, but with recently available effective treatments.

AIMS

To efficiently diagnose and to offer treatment for PAH, we established a multidisciplinary service in 2005, where patients attend a clinic staffed by specialists in cardiology, respiratory medicine, rheumatology and immunology in a tertiary referral hospital setting.

METHODS

We studied the first 200 patients referred. Serology, echocardiography, lung function tests, high-resolution computed tomography, World Health Organisation Class determination and 6-min walk tests and/or right heart catheterisation were performed, as clinically indicated.

RESULTS

Of the 200 patients seen, 66 had confirmed pulmonary hypertension (mean pulmonary artery pressure > 25 mmHg) diagnosed on echocardiography ± right heart catheterisation. Of these patients, 58 had catheter-proven PAH (mean pulmonary artery pressure > 25 mmHg with mean wedge pressure < 15 mmHg). Underlying diagnoses for the confirmed PAH patients were idiopathic (32), scleroderma-associated (14), other connective tissue disease (4) and associated with congenital heart disease (8). Patients with confirmed PAH were commenced on PAH-specific therapy--initially bosentan in the majority but sildenafil, and iloprost were occasionally used initially for patient-specific reasons. Median time from when the patient first called the clinic to prescription of therapy was 16 days (interquartile range; 0-31 days). All surviving patients with PAH have attended for regular 6-monthly follow-up visits with a 100% retention rate up to 4 years.

CONCLUSION

A multidisciplinary clinic can provide efficient diagnosis and rapid triage to PAH-specific therapy, if appropriate. Retention rates remain high, at follow up.

Prognostic factors and outcomes of patients with pulmonary hypertension admitted to the intensive care unit

PURPOSE

Patients with pulmonary hypertension (PH) can decompensate to the point where they require care in the intensive care unit (ICU). Our objective is to examine the outcomes and characteristics of patients with PH admitted to the ICU.

METHODS

This is a retrospective study of 99 patients with PH who were admitted to the medical ICU of a single tertiary care center. Baseline characteristics, interventions during ICU admission, and ICU and 6-month outcome were documented. Univariate and multivariate logistic regressions were used to evaluate association of patient characteristics with mortality.

RESULTS

Intensive care unit mortality was 30%, and 6-month mortality was 40%. Acute Physiology and Chronic Health Evaluation II score, World Health Organization Group 3 PH, and preexisting treatment with a prostacyclin at time of ICU admission were associated with worse outcome. Patients who received cardiopulmonary resuscitation had 100% mortality. The requirement for mechanical ventilation and dialysis was also associated with increased mortality. Pulmonary artery catheter placement was associated with reduced mortality, specifically if it was placed early during ICU admission and if associated with a change in the present management.

CONCLUSIONS

Mortality is high in critically ill patients with PH. The identification of prognostic baseline characteristics and interventions in the ICU is important and warrants further investigation.

Prostanoids for Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a severe condition that markedly reduces exercise capacity and survival in the affected patient population. PAH includes primary pulmonary hypertension (PPH) and pulmonary hypertension associated with collagen vascular diseases, congenital systemic-to-pulmonary shunts, portal hypertension and HIV infection. All these conditions share virtually identical obstructive pathologic changes of the pulmonary microcirculation and probably similar pathobiologic processes. The pathophysiology is characterized by a progressive increase in pulmonary vascular resistance, leading to right ventricular failure and death. Prostacyclin is an endogenous substance that is produced by vascular endothelial cells and induces vasodilatation, inhibition of platelet activity, and antiproliferative effects. A dysregulation of prostacyclin metabolic pathways has been shown in patients with PAH and this represents the rationale for the exogenous therapeutic administration of this substance. The clinical use of prostacyclin in patients with PAH has been made possible by the synthesis of stable analogs that possess different pharmacokinetic properties but share similar pharmacodynamic effects. Experience in humans has been initially collected with epoprostenol, which is a synthetic salt of prostacyclin. Epoprostenol has a short half-life in the circulation and requires continuous administration by the intravenous route by means of infusion pumps and permanent tunnelized catheters. In addition, epoprostenol is unstable at room temperature, and the complex delivery system required is associated with several adverse effects and potentially serious complications. For these reasons, alternatives to intravenous epoprostenol have been sought and this has led to the development of analogs that can be administered subcutaneously (treprostinil), orally (beraprost sodium) or by inhalation (iloprost). Three unblinded clinical trials and several uncontrolled trials have shown that treatment with epoprostenol improved symptoms and exercise capacity in New York Heart Association (NYHA) class III and IV PAH patients and also survival in patients with PPH. Subcutaneous treprostinil improved symptoms, exercise, hemodynamics and clinical events in the largest clinical trial ever performed in PAH, but local infusion site reactions limited efficacy in a proportion of patients. Oral beraprost sodium improved exercise capacity only in patients with PPH and is the only prostacyclin analog that has also been tested in NYHA class II patients. Inhaled iloprost has improved symptoms, exercise capacity and clinical events in patients with PAH and inoperable chronic thromboembolic pulmonary hypertension. The favorable effects of prostanoids observed in all studies coupled with different profiles of adverse events and tolerability for each prostacyclin analog allow the unique opportunity to select the most appropriate compound for the individual patient with PAH.

Endurance training increases exercise-induced prostacyclin release in young, healthy men--relationship with VO2max

In the present study, we evaluated the effect of 5 weeks of moderate-intensity endurance training on the basal and exercise-induced systemic release of prostacyclin (PGI(2)), as assessed by plasma 6-keto-PGF(1 alpha) concentration. Twelve physically active young men with the following characteristics participated in this study (the mean +/- SD): age, 22.7 +/- 2.0 years; body mass, 76.8 +/- 8.9 kg; BMI, 23.48 +/- 2.17 kg x m(-2); and maximal oxygen uptake (VO(2 max)), 46.1 +/- 4.0 ml x kg(-1) x min(-1). Plasma 6-keto-PGF(1 alpha) concentrations were measured in venous blood samples taken prior to the exercise and at exhaustion (at VO(2 max)) before and after completing the training protocol. On average, the training resulted in a significant increase in VO(2 max) (p = 0.03), power output at VO(2 max) (p = 0.001) and a significant increase (p = 0.05) in the net-exercise-induced increase in plasma 6-keto-PGF(1 alpha) concentration (Delta 6-keto-PGF(1 alpha) i.e., the difference between the end-exercise and pre-exercise 6-keto-PGF(1 alpha) concentrations). No effect of training on the basal PGI(2) concentration was found. Interestingly, within the study sample (n = 12), two subgroups could be defined with a differential pattern of response with respect to Delta 6-keto-PGF(1 alpha) concentrations. In one subgroup (n = 7), a significant increase in Delta 6-keto-PGF(1 alpha) concentration after training was found (p < 0.02) (responders). This enhancement in the exercise-induced PGI(2) release was accompanied by a significant (p < 0.05) increase in VO(2 max) after training. In contrast, in another subgroup (n = 5), there was no observed effect of training on the Delta 6-keto-PGF(1 alpha) concentration and the VO(2 max) after training (non-responders). In both of these subgroups, training did not influence the basal PGI(2) concentration. In conclusion, the endurance training resulted in the adaptive augmentation of the systemic release of PGI(2) in response to exercise, which plays a role in the training-induced increase in VO(2 max) in young, healthy men. The impairment of the training-induced augmentation of PGI(2) release in response to exercise demonstrated in the non-responders subgroup may predispose them to increased cardiovascular risk during vigorous exercise.

Diagnosis of pulmonary arterial hypertension

Accurate diagnosis of pulmonary arterial hypertension is a challenging and complex process that requires a high index of clinical suspicion from even the most astute clinician. This article discusses the use of a variety of noninvasive tests that can help define the population of patients in whom invasive cardiac catheterization should be pursued. It points out the vagaries and limitations of electrocardiography and the radiographic and echocardiographic clues to the diagnosis. Ultimately, right- and, often, concomitant left-heart catheterization is required to establish the diagnosis and distinguish pulmonary arterial hypertension from pulmonary venous hypertension.

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.

The pulmonary involvement in portal hypertension: portopulmonary hypertension and hepatopulmonary syndrome

Pulmonary abnormalities are common in patients with advanced chronic liver disease. Two distinct syndromes strictly related to the presence of portal hypertension, but clearly different from a pathophysiologic point of view, have been identified. Portopulmonary hypertension, characterized by an increased pulmonary arterial pressure, is due to a progressive arteriolar vasoconstriction induced by excess local production of vasoconstrictor substances. Hepatopulmonary syndrome results from intrapulmonary microvascular dilation caused by an inadequate synthesis or metabolism of putative pulmonary vasoactive substances leading to a functional vasodilation of the pulmonary vasculature, ultimately leading to hypoxemia. Controversies on pathogenesis imply different tentative therapeutic approaches for the medical management of these conditions. The development of portopulmonary hypertension or the hepatopulmonary syndrome has important clinical and prognostic implications facing the impact of new therapeutic strategies for the management of the main complications of advanced liver diseases on cardiopulmonary function.

Life-threatening dermatoses due to connective tissue disorders

Connective tissue disorders such as scleroderma, dermatomyositis and lupus erythematosus are autoimmune, multi-system disorders whose clinical manifestations can be restricted to the skin or may involve many organs. The degree and rate of organ system involvement defer, as does the prognosis and rapidity of disease progression. In this article, scleroderma, dermatomyositis and lupus erythematosus will be reviewed in respect to their life-threatening potential.

End-tidal Pco 2 Abnormality and Exercise Limitation in Patients With Primary Pulmonary Hypertension

OBJECTIVES

Primary pulmonary hypertension (PPH) is a pulmonary vasculopathy resulting in exercise intolerance, usually due to dyspnea. We hypothesized that ventilation is increased during exercise in PPH relative to normal because the ventilated lung is underperfused, cardiac output increase is restricted, and arterial hypoxemia may develop. Our aim was to determine the size of the reduction in end-tidal Pco(2) (Petco(2)) as a reflection of the abnormality in ventilatory efficiency and ventilatory drive in PPH patients.

METHODS

We performed cardiopulmonary exercise testing (CPET) in 52 PPH patients. All had hemodynamic measurements to confirm the diagnosis of PPH. A subgroup of 29 patients who underwent right-heart catheterization within 50 days of CPET were studied to compare their CPET responses to resting hemodynamics. Nine healthy volunteers matched for age and gender served as CPET control subjects.

RESULTS

In PPH patients, the percentage of predicted peak oxygen uptake (Vo(2)) correlated significantly with mean pulmonary artery pressure (mPAP) [r = - 0.59, p = 0.0007, n = 29]. Petco(2) values at rest, anaerobic threshold (AT), and peak Vo(2) were proportionately reduced as percentage of predicted peak Vo(2) decreased (r = 0.66 to 0.72, p < 0.0001, n = 52). Petco(2) values at rest, AT, and peak Vo(2) were also reduced as mPAP increased (r = - 0.51 to - 0.53, p < 0.005, n = 29). In contrast to normal subjects in whom Petco(2) increased from rest to AT, Petco(2) decreased in PPH patients, except for two patients with mild PPH in whom there was no change. Also, Petco(2) increased rather than decreased further at the start of recovery, in contrast to normal. Although usually normal at rest, oxyhemoglobin saturation decreased during exercise in most PPH patients.

CONCLUSIONS

In patients with PPH, Petco(2) at rest and exercise is significantly reduced in proportion to physiologic disease severity. The range of values is unusually low. Furthermore, the directional changes of Petco(2) during exercise and early recovery are in the opposite direction of normal.

Utility of cardiopulmonary stress testing in assessing disease severity in children with pulmonary arterial hypertension

This study sought to assess the safety of cardiopulmonary stress testing in 40 children with pulmonary arterial hypertension and to compare exercise responses in this patient cohort with those of a healthy control population. Patients with pulmonary hypertension had significant impairment in aerobic capacity, with a peak oxygen consumption of 20.7 +/- 6.9 versus 35.5 +/- 7.4 ml/kg/min in healthy controls (p <0.0001). Peak oxygen consumption was strongly correlated with invasive measures of disease severity, including pulmonary vascular resistance index (r = -0.6, p = 0.006). Exercise testing can be performed safely in this group of patients and can yield valuable clinical information.

The influence of VIP and epoprostenol on platelet CD62P expression and primary haemostasis in vitro

Human vasoactive intestinal peptide (VIP) and epoprostenol (prostacyclin) have vasodilatative effects in the pulmonary circulation. Both VIP and epoprostenol are successfully used to treat pulmonary hypertension in humans and experimental animal models. The positive effects of epoprostenol on the course of this disease are achieved through vasodilatation and inhibitory effects on platelet activity. Since VIP also binds specifically to platelets, we compared the in vitro effects of VIP and epoprostenol on platelet P-Selectin (CD62P) expression and primary haemostasis. Anti-aggregative effects of VIP (10(-6) mol and 10(-8) mol) and epoprostenol (50, 5 and 0.5 ng/ml) on platelets were determined by agonist-induced CD62P expression and in vitro bleeding time (PFA-100 trade mark system). Blood from healthy individuals was either incubated with epoprostenol, VIP or saline control and was analysed by whole blood flow cytometry and the PFA-100 trade mark. Prior to flow cytometric analysis, the platelets were stimulated with either arachidonic acid (AA) or adenosine diphosphate (ADP). Whole blood flow cytometry analysis showed that epoprostenol inhibited dose-dependently agonist-induced CD62P expression, whereas VIP did not inhibit CD62P expression. PFA analysis revealed substantial closure time prolongation by epoprostenol and again no effects of VIP. These results indicate that VIP, in contrast to epoprostenol, has no effect on platelet CD62P expression and primary haemostasis.

End points and clinical trial designs in pulmonary arterial hypertension

To date, randomized controlled clinical trials performed in pulmonary arterial hypertension (PAH) have been relatively short-term studies involving mainly patients with advanced disease. The primary end points in these trials have addressed exercise capacity, usually by using the 6-min walk test. Although this approach is still warranted in future trials assessing new treatments, it is likely that the focus will shift toward trials of longer duration, involving patients with less advanced disease, and that different drugs and drug-combination regimens will be compared. In such trials, it is possible that a composite of markers indicating clinical deterioration (e.g., hospitalization for right heart failure, the requirement for the introduction of an alternative treatment, and predefined indicators of worsening exercise tolerance) may be more useful as primary end points. Quality of life will become a very important issue; however, appropriate quality-of-life questionnaires for PAH have yet to be developed. In addition, hemodynamics will likely remain valuable as secondary end points, but future clinical trials should include hemodynamics obtained both during exercise and at rest. Finally, cardiopulmonary exercise testing, echocardiographic studies, and biochemical parameters, such as brain natriuretic peptide or troponin T, may also prove useful as secondary end points in the future.

Effects of epoprostenol on right ventricular hypertrophy and dilatation in pulmonary hypertension

OBJECTIVES

To gain more knowledge of changes in main pulmonary artery flow and right ventricular mass and volumes in patients with pulmonary hypertension during epoprostenol therapy.

METHODS

Eleven patients (9 women) were evaluated before the start of therapy and every 4 months thereafter. Right and left ventricular volumes and masses were measured by cine MRI. Flow was measured with MRI velocity quantification. At the same times, 6-min walking tests were performed. Right-heart catheterizations were performed at baseline and after 1 year.

RESULTS

Right ventricular mass in the patient group was significantly higher from that in a control group of healthy volunteers (95 +/- 26 g vs 42 +/- 10 g, p < 0.05 [mean +/- SD]), whereas the stroke volume was lower (34 +/- 11 mL vs 81 +/- 11 mL, p < 0.05). The greatest improvement in right ventricular stroke volume (to 41 +/- 11 mL, p < 0.05) took place in the first 4 months. During the 1-year follow-up, right ventricular end-diastolic volume and mass did not change, and mean pulmonary artery pressure remained nearly stable at 55 mm Hg at baseline and 53 mm Hg after 1 year. Pulmonary vascular resistance decreased by 12.5% (p = 0.06).

CONCLUSIONS

From these data we conclude that epoprostenol lowers pulmonary vascular resistance, leading to an increase in pulmonary artery flow. This increase in pulmonary artery flow corresponds well with the increase in 6-min walking distance and can be noninvasively monitored by MRI (flow quantification). Right ventricular dilatation and hypertrophy are not reversed by epoprostenol therapy, but do not progress either.

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.

Pulmonary function in primary pulmonary hypertension

OBJECTIVES

The study was done to ascertain the degree to which abnormalities in resting lung function correlate with the disease severity of patients with primary pulmonary hypertension (PPH).

BACKGROUND

Patients with PPH are often difficult to diagnose until several years after the onset of symptoms. Despite the seriousness of the disorder, the diagnosis of PPH is often delayed because it is unsuspected and requires invasive measurements. Although PPH often causes abnormalities in resting lung function, these abnormalities have not been shown to be statistically significant when correlated with other measures of PPH severity.

METHODS

Resting lung mechanics and diffusing capacity for carbon monoxide DL(CO) were assessed in 79 patients whose findings conformed to the classical diagnostic criteria of PPH and who had no evidence of secondary causes of pulmonary hypertension. These findings were correlated with severity of disease as assessed by cardiac catheterization, New York Heart Association (NYHA) class, and cardiopulmonary exercise testing.

RESULTS

When PPH patients were first evaluated at our referral clinic, the DL(CO) and lung volumes were decreased in approximately three-quarters and one-half, respectively. The decreases in DL(CO), and to a lesser extent lung volumes, correlated significantly with decreases in peak oxygen uptake (reflecting maximum cardiac output), peak oxygen pulse (reflecting maximum stroke volume), and anaerobic threshold (reflecting sustainable exercise capacity) and higher NYHA class.

CONCLUSIONS

Patients with PPH commonly have abnormalities in lung mechanics and DL(CO) levels that correlate significantly with disease severity. These measurements can be useful in evaluating patients with unexplained dyspnea and fatigue.

[Ten years' experience in continuous intravenous epoprostenol therapy in severe pulmonary arterial hypertension]

INTRODUCTION

Primary pulmonary hypertension and its associated forms is a progressive and often fatal disease, the course of which has been favourably modified by prostacyclin therapy in the last decade.

OBJECTIVE

The aim of this study is to analize retrospectively the efficacy of continuous intravenous epoprostenol (synthetic prostacyclin) therapy in pulmonary arterial hypertension, and to compare it with conventional therapy (anticoagulants, digoxin and diuretics).

METHODS

Between 1990-2000, 31 patients with severe precapillary pulmonary hypertension in functional class III or IV went on continuous intravenous epoprostenol therapy, administered by a portable infusion pump through a Hickman catheter. We compared their survival with a group of 16 patients treated with conventional therapy alone.

RESULTS

Time of follow-up was 33.25 months in the prostacyclin group and 20 months in the conventional group. The one- three- and five- year survival rates were 86%, 50% and 38% respectively for patients treated with epoprostenol compared with 40%, 40% and 8% survival rates at idetical periods for patients treated conventionally (p = 0,02). Functional class and the mean distance walked in the 6 minutes test were improved in patients treated with prostacyclin (p < 0,01). Serious complications attributable to the delivery system included 3 deaths, mainly due to infection.

CONCLUSION

Continuous intravenous epoprostenol therapy improves survival and exercise capacity in patients with severe pulmonary arterial hypertension despite potentially serious complications attributable to the delivery system.

Portopulmonary hypertension: a tale of two circulations

Pulmonary involvement is common in patients with portal hypertension and can manifest in diverse manners. Changes in pulmonary arterial resistance, manifesting either as the hepatopulmonary syndrome or portopulmonary hypertension (PPHTN), have been increasingly recognized in these patients in recent years. This review summarizes the clinicopathologic features, diagnostic criteria, as well as the latest concepts in the pathogenesis and management of PPHTN, which is defined as an elevated pulmonary artery pressure in the setting of an increased pulmonary vascular resistance and a normal wedge pressure in a patient with portal hypertension.

Primary pulmonary hypertension and cor pulmonale

Primary pulmonary hypertension and cor pulmonale represent forms of precapillary pulmonary hypertension due to intrinsic lung disease. In the case of primary pulmonary hypertension, this is due to disease of the pulmonary vasculature while cor pulmonale is related to diseases of the pulmonary vasculature, airways, or interstitium. Patients present with signs and symptoms of right ventricular dysfunction and low cardiac output including dyspnea, chest pain and peripheral edema. Therapy is directed at the underlying disease and may include supplemental oxygen for diseases causing chronic hypoxemia and anticoagulation for thrombotic disease. Vasodilator therapy has variable efficacy for pulmonary vascular disorders. Postacyclin by continuous infusion has been a major advance in the therapy of primary pulmonary hypertension and has prolonged survival and delayed the need for lung transplantation. Bosentan, an endothelin receptor blocking agent is the first oral medication approved for the therapy of pulmonary hypertension.

A combination of oral endothelin-A receptor antagonist and oral prostacyclin analogue is superior to each drug alone in ameliorating pulmonary hypertension in rats

OBJECTIVES

We sought to investigate whether the combination of an oral endothelin (ET)A receptor antagonist and an oral prostacyclin (PGI(2)) analogue is superior to the single use of each drug alone for treating pulmonary hypertension (PH).

BACKGROUND

Treatment with intravenous PGI(2) or an ET(A) receptor antagonist was effective for PH; however, the effect of both agents is unclear.

METHODS

We administered the oral ET(A) receptor antagonist TA-0201 and/or the oral PGI(2) analogue beraprost sodium (BPS) to rats with monocrotaline-induced PH for 19 days. The groups were: normal rats with vehicle treatment (Control group), PH rats with vehicle treatment (PH group), PH rats with TA-0201 treatment (PH + TA group), PH rats with BPS treatment (PH + BPS group) and PH rats with TA-0201 and BPS treatment (PH + TA + BPS group).

RESULTS

Right ventricular (RV) systolic pressure and the ratio of RV systolic pressure to systemic systolic blood pressure (Pp/Ps) were markedly higher in the PH group than in the Control group. The increased RV systolic pressure and Pp/Ps were significantly and comparably depressed in the PH + TA and PH + BPS groups; it was more greatly depressed in the PH + TA + BPS group than in the groups with each drug alone. The indexes of RV hypertrophy showed the same tendency as the increase in RV systolic pressure among the five groups. The expression of beta-myosin heavy chain messenger ribonucleic acid in the RV was markedly augmented in the PH group; the enhancement was inhibited in the PH + TA + BPS group to the greatest degree. Medial wall thickness of the pulmonary artery was markedly increased in the PH group; the increase was depressed in the PH + TA + BPS group. Combined treatment also ameliorated PH, even if it started after the onset of PH.

CONCLUSIONS

The combination of an oral ETA receptor antagonist and an oral PGI(2) analogue is superior to the single use of each drug alone in inhibiting the progression of PH.

Current management of primary pulmonary hypertension

Primary pulmonary hypertension (PPH) is a rare disorder of the lung vasculature characterised by an increase in pulmonary artery pressure. Although the aetiology of this disease remains unknown, knowledge of the pathophysiology of the disease has advanced considerably. Diagnosis of PPH is largely by exclusion. The clinical symptoms associated with PPH are aspecific and similar to those seen in other cardiovascular and pulmonary diseases. Electrocardiography, echocardiography, pulmonary function tests, and a lung perfusion scan are necessary to exclude secondary forms of pulmonary hypertension and also help to confirm the diagnosis of PPH. A definite diagnosis of PPH is established by right-heart catheterisation which gives a precise measure of the blood pressure in the right side of the heart and the pulmonary artery, right ventricular function and cardiac output. Once a diagnosis of PPH is established, treatment involving drug therapy or surgery is commenced on the basis of the New York Heart Association functional class. Conventional treatment consists of lifetime administration of anticoagulants, oxygen, diuretics, and digoxin. Vasodilator therapy with calcium channel antagonists is indicated in patients who are 'vasoreactive' to acute vasodilator challenge as assessed by right-heart catheterisation. Promising results are obtained by continuous intravenous administration of epoprostenol (prostacyclin). Newer therapies for PPH include prostacyclin analogues, endothelin receptor antagonists, nitric oxide, phosphodiesterase-5 inhibitors, elastase inhibitors, and gene therapy. Surgical treatment consists of atrial septostomy, thromboendarterectomy, and lung or heart-lung transplantation.

Cellular pathophysiology and therapy of pulmonary hypertension

The identification of several mutations of the bone morphogenetic protein receptor 2 (BMPR2) gene, a member of the transforming growth factor beta receptor family, gives hope for new insights into the pathophysiology of pulmonary hypertension. Genetic predisposition might dictate the responses of pulmonary artery fibroblasts, smooth muscle cells, and endothelial cells, as well as platelets and leukocytes, or their specific interactions with different extrinsic factors. These cells possess distinct subtypes and interact with each other. Pulmonary hypertension is associated with vasoconstriction, remodeling, and in situ thrombosis of the pulmonary arteries, but the initial events and their relationship to the genetic background are presently unknown. Current therapeutic approaches are based on our knowledge of the physiologic regulation of pulmonary artery tone, pathophysiologic changes, and our clinical experience with different treatment strategies. Beyond diuretics and anticoagulants, prostaglandins are generally accepted therapeutic agents for primary pulmonary hypertension and related diseases, whereas high-dose calcium-channel blockers are reserved for a small subset of patients, those who respond favorably to vasodilators in an acute test. Long-term intravenous prostacyclin infusion has become the most important specific therapy for primary pulmonary hypertension and associated diseases. However, this therapy is hampered by catheter complications and systemic side effects. Alternative application routes of prostacyclin or its stable analogs may avoid these problems. Inhaled application of the prostacyclin analog iloprost results in predominant pulmonary vasodilation with few systemic side effects and may possess clinical efficacy similar to that of intravenous prostacyclin. Inhaled nitric oxide is widely accepted as a screening agent for active responders to vasodilators and has a similar hemodynamic profile as inhaled iloprost, although the percentage of responders is considerably lower. However, there are unsolved toxicologic questions and practical difficulties concerning the safe long-term application of nitric oxide. Combining inhaled vasodilators with phosphodiesterase inhibitors may prolong the duration of the effects and improve the convenience of inhaled therapy for pulmonary hypertension. Therapeutic approaches in the future may aim at the transforming growth factor beta pathway and at the identification of early stages of the disease to prevent further disease progression.

Pulmonary function test abnormalities in pulmonary vascular disease and chronic heart failure

Diagnostic criteria based on pulmonary function testing for pulmonary vascular disease and CHF are imprecise. Although these tests constitute a necessary part of the work-up of a patient with dyspnea, additional studies are required to obtain a final diagnosis in the setting of cardiopulmonary vascular disease. In contrast, specific pulmonary function tests may offer an objective means of assessing severity of dysfunction resulting from pulmonary hypertension or CHE Serial measurements of pulmonary function offer insight into general and specific patterns of cardiopulmonary vascular disease and are useful in evaluating response to treatment.

Residual pulmonary vasoreactivity to inhaled nitric oxide in patients with severe obstructive pulmonary hypertension and Eisenmenger syndrome

OBJECTIVE

To determine whether inhaled NO (iNO) can reduce pulmonary vascular resistance in adults with congenital heart disease and obstructive pulmonary hypertension or Eisenmenger syndrome.

DESIGN

23 patients received graded doses of iNO. Pulmonary and systemic haemodynamic variables and circulating cyclic guanosine monophosphate (cGMP) concentrations were measured at baseline and after 20 and 80 ppm iNO. Patients were considered responders when total pulmonary resistance was reduced by at least 20%, and rebound was defined as a greater than 10% increase in total pulmonary resistance upon withdrawal from iNO.

RESULTS

In response to 20 ppm iNO, total pulmonary resistance decreased in four patients (18%, 95% confidence interval (CI), 2% to 34%), while in response to 80 ppm iNO it decreased in six patients (29%, 95% CI 10% to 38%). Systemic blood pressure did not change. Withdrawal resulted in rebound in three patients (16%, 95% CI 0% to 32%) after cessation of 20 ppm iNO, and in six patients (35%, 95% CI 12% to 58%) after cessation of 80 ppm iNO. Patients with predominant right to left shunting did not respond. In all patients cGMP increased from (mean (SD)) 28 (13) micromol/l at baseline to 55 (30) and 78 (44) micromol/l after 20 and 80 ppm iNO (p < 0.05 v baseline).

CONCLUSIONS

NO inhalation is safe and is associated with a dose dependent increase in circulating cGMP concentrations. Pulmonary vasodilatation in response to iNO was observed in 29% of patients and was influenced by baseline pulmonary haemodynamics. Responsiveness to acute iNO may identify patients with advanced obstructive pulmonary hypertension and Eisenmenger syndrome who could benefit from sustained vasodilator treatment.

Medical therapy of pulmonary hypertension. The prostacyclins

Prostacyclin is a substance produced by endothelial cells that induces vasodilation and inhibition of platelet aggregation and of vascular cell migration and proliferation. A dysregulation of the prostacyclin metabolic pathways has been shown in patients with pulmonary arterial hypertension. The clinical use of prostacyclin has been made possible by the synthesis of stable analogues that possesses different pharmacokinetic properties but share similar pharmacodynamic effects. The greatest experience has been collected with intravenous epoprostenol while other compounds like subcutaneous UT-15, inhaled iloprost and oral beraprost are currently in different stages of clinical development. Although favorable results have been reported for each compound, different benefit-to-side effects profiles characterize the various modalities of the administration.

Exercise pathophysiology in patients with primary pulmonary hypertension

BACKGROUND

Patients with primary pulmonary hypertension (PPH) have a pulmonary vasculopathy that leads to exercise intolerance due to dyspnea and fatigue. To better understand the basis of the exercise limitation in patients with PPH, cardiopulmonary exercise testing (CPET) with gas exchange measurements, New York Heart Association (NYHA) symptom class, and resting pulmonary hemodynamics were studied.

METHODS AND RESULTS

We retrospectively evaluated 53 PPH patients who had right heart catheterization and cycle ergometer CPET studies to maximum tolerance as part of their clinical workups. No adverse events occurred during CPET. Reductions in peak O(2) uptake (VO(2)), anaerobic threshold, peak O(2) pulse, rate of increase in VO(2), and ventilatory efficiency were consistently found. NYHA class correlated well with the above parameters of aerobic function and ventilatory efficiency but less well with resting pulmonary hemodynamics.

CONCLUSIONS

Patients with PPH can safely undergo noninvasive cycle ergometer CPET to their maximal tolerance. The CPET abnormalities were consistent and characteristic and correlated well with NYHA class.