Haemodynamics, exercise capacity and clinical events in pulmonary arterial hypertension

Reduced exercise capacity occurs before intrinsic skeletal muscle dysfunction in experimental rat models of pulmonary hypertension

Reduced exercise capacity in pulmonary hypertension (PH) significantly impacts quality of life. However, the cause of reduced exercise capacity in PH remains unclear. The objective of this study was to investigate whether intrinsic skeletal muscle changes are causative in reduced exercise capacity in PH using preclinical PH rat models with different PH severity. PH was induced in adult Sprague-Dawley (SD) or Fischer (CDF) rats with one dose of SU5416 (20 mg/kg) injection, followed by 3 weeks of hypoxia and additional 0-4 weeks of normoxia exposure. Control s rats were injected with vehicle and housed in normoxia. Echocardiography was performed to assess cardiac function. Exercise capacity was assessed by VO2 max. Skeletal muscle structural changes (atrophy, fiber type switching, and capillary density), mitochondrial function, isometric force, and fatigue profile were assessed. In SD rats, right ventricular systolic dysfunction is associated with reduced exercise capacity in PH rats at 7-week timepoint in comparison to control rats, while no changes were observed in skeletal muscle structure, mitochondrial function, isometric force, or fatigue profile. CDF rats at 4-week timepoint developed a more severe PH and, in addition to right ventricular dysfunction, the reduced exercise capacity in these rats is associated with skeletal muscle atrophy; however, mitochondrial function, isometric force, and fatigue profile in skeletal muscle remain unchanged. Our data suggest that cardiopulmonary impairments in PH are the primary cause of reduced exercise capacity, which occurs before intrinsic skeletal muscle dysfunction.

Impact of selexipag use within 12 months of pulmonary arterial hypertension diagnosis on hospitalizations and medical costs: A retrospective cohort study

BACKGROUND

Oral selexipag, a prostacyclin pathway agent (PPA), is effective in patients with pulmonary arterial hypertension (PAH). The objective of this study is to assess the impact of initiating oral selexipag within 12 months of diagnosis on health outcomes.

METHODS

This retrospective cohort study used data from Optum's de-identified Clinformatics® Data Mart Database. PAH patients between 1 October 2015 and 30 September 2019 were included. Patients were also required to have received PAH medication within 12 months of their initial diagnosis. Study groups included patients who initiated selexipag within 12 months of PAH diagnosis (SEL ≤ 12) and those who did not initiate any PPA within 12 months of PAH diagnosis (No PPA ≤ 12). Inverse probability of treatment weighting was used to remove potential confounding between groups. Cox and Poisson regression models were used to compare hospitalization and disease progression. Generalized linear model with gamma distribution and log link was used to compare costs.

RESULTS

SEL ≤ 12 had lower rate of all-cause hospitalizations (rate ratio: 0.76, 95% confidence interval [CI]: 0.60, 0.96) versus no PPA ≤ 12, but no differences in PAH-related hospitalization rate (rate ratio: 1.03, 95% CI: 0.79, 1.33) or risk of disease progression (hazard ratio: 1.01, 95% CI: 0.71, 1.44). SEL ≤ 12 incurred lower all-cause (mean difference: -$23 623; 95% CI: -35 537, -8512) and PAH-related total medical costs (mean difference: -$12 927; 95% CI: -19 559, -5679) versus no PPA ≤ 12.

CONCLUSION

Selexipag initiation within 12 months of PAH diagnosis demonstrated reductions in all-cause hospitalization rate and medical costs.

Evolution and optimization of clinical trial endpoints and design in pulmonary arterial hypertension

Selection of endpoints for clinical trials in pulmonary arterial hypertension (PAH) is challenging because of the small numbers of patients and the changing expectations of patients, clinicians, and regulators in this evolving therapy area. The most commonly used primary endpoint in PAH trials has been 6-min walk distance (6MWD), leading to the approval of several targeted therapies. However, single surrogate endpoints such as 6MWD or hemodynamic parameters may not correlate with clinical outcomes. Composite endpoints of clinical worsening have been developed to reflect patients' overall condition more accurately, although there is no standard definition of worsening. Recently there has been a shift to composite endpoints assessing clinical improvement, and risk scores developed from registry data are increasingly being used. Biomarkers are another area of interest, although brain natriuretic peptide and its N-terminal prohormone are the only markers used for risk assessment or as endpoints in PAH. A range of other genetic, metabolic, and immunologic markers is currently under investigation, along with conventional and novel imaging modalities. Patient-reported outcomes are an increasingly important part of evaluating new therapies, and several PAH-specific tools are now available. In the future, alternative statistical techniques and trial designs, such as patient enrichment strategies, will play a role in evaluating PAH-targeted therapies. In addition, modern sequencing techniques, imaging analyses, and high-dimensional statistical modeling/machine learning may reveal novel markers that can play a role in the diagnosis and monitoring of PAH.

The Role of Exercise Testing in Pulmonary Vascular Disease: Diagnosis and Management

Exercise intolerance is the dominant symptom of pulmonary hypertension (PH). The gold standard for the estimation of exercise capacity is a cycle ergometer incremental cardiopulmonary exercise test (CPET). The main clinical variables generated by a CPET are peak oxygen uptake (Vo2peak), ventilatory equivalents for carbon dioxide (VE/Vco₂), systolic blood pressure, oxygen (O2) pulse, and chronotropic responses. PH is associated with hyperventilation at rest and at exercise, and an increase in physiologic dead space. Maximal cardiac output depends on right ventricular function and critically determines a PH patient's exercise capacity. Dynamic arterial O2 desaturation can also depress the Vo2peak.

Exercise intolerance in pulmonary arterial hypertension: insight into central and peripheral pathophysiological mechanisms

Exercise intolerance is a cardinal symptom of pulmonary arterial hypertension (PAH) and strongly impacts patients' quality of life (QoL). Although central cardiopulmonary impairments limit peak oxygen consumption (V' O2peak ) in patients with PAH, several peripheral abnormalities have been described over the recent decade as key determinants in exercise intolerance, including impaired skeletal muscle (SKM) morphology, convective O2 transport, capillarity and metabolism indicating that peripheral abnormalities play a greater role in limiting exercise capacity than previously thought. More recently, cerebrovascular alterations potentially contributing to exercise intolerance in patients with PAH were also documented. Currently, only cardiopulmonary rehabilitation has been shown to efficiently improve the peripheral components of exercise intolerance in patients with PAH. However, more extensive studies are needed to identify targeted interventions that would ultimately improve patients' exercise tolerance and QoL. The present review offers a broad and comprehensive analysis of the present literature about the complex mechanisms and their interactions limiting exercise in patients and suggests several gaps in knowledge that need to be addressed in the future for a better understanding of exercise intolerance in patients with PAH.

Risk Reduction and Hemodynamics with Initial Combination Therapy in Pulmonary Arterial Hypertension

Rationale: An initial oral combination of drugs is being recommended in pulmonary arterial hypertension (PAH), but the effects of this approach on risk reduction and pulmonary vascular resistance (PVR) are not known.Objectives: To test the hypothesis that a low-risk status would be determined by the reduction of PVR in patients with PAH treated upfront with a combination of oral drugs.Methods: The study enrolled 181 treatment-naive patients with PAH (81% idiopathic) with a follow-up right heart catheterization at 6 months (interquartile range, 144-363 d) after the initial combination of endothelin receptor antagonist + phosphodiesterase-5 inhibitor drugs and clinical evaluation and risk assessments by European guidelines and Registry to Evaluate Early and Long-Term PAH Disease Management scores.Measurements and Main Results: Initial combination therapy improved functional class and 6-minute-walk distance and decreased PVR by an average of 35% (median, 40%). One-third of the patients had a decrease in PVR <25%. This poor hemodynamic response was independently predicted by age, male sex, pulmonary artery pressure and cardiac index, and at echocardiography, a right/left ventricular surface area ratio of greater than 1 associated with low tricuspid annular plane systolic excursion of less than 18 mm. A low-risk status at 6 months was achieved or maintained in only 34.8% (Registry to Evaluate Early and Long-Term PAH Disease Management score) to 43.1% (European score) of the patients. Adding criteria of poor hemodynamic response improved prediction of a low-risk status.Conclusions: A majority of patients with PAH still insufficiently improved after 6 months of initial combinations of oral drugs is identifiable at initial evaluation by hemodynamic response criteria added to risk scores.

Follow-Up Functional Class and 6-Minute Walk Distance Identify Long-Term Survival in Pulmonary Arterial Hypertension

PURPOSE

Guidelines recommend specific treatment goals for pulmonary arterial hypertension (PAH) patients: functional class I or II, 6-min walk distance (6MWD) ≥ 380 to 440 m, normal natriuretic peptide levels, and normal right-sided invasive hemodynamics. Only observational registry data support this recommendation. Our aim was to test these goals in a large group 1 PAH cohort against long-term survival.

METHODS

We analyzed the PHIRST and TRIUMPH populations (n = 563, age 53.5 ± 14.7 years, female sex 79%). The predictor variables were the treatment goals measured at the end of the placebo-controlled phase (16 and 12 weeks, respectively). The primary outcome was all-cause mortality at the end of follow-up during the open-label extension phase.

RESULTS

There were 73 deaths during median follow of 1072 days (range 27 to 2177). Patients who achieved a functional class I or II had better survival. Both a 6MWD ≥ 380 m and ≥ 440 m were associated with lower mortality, but survival was better in patients able to walk ≥ 440 m. The best long-term survival was achieved with functional class I or II and 6MWD ≥ 440 m. In a subset of the population, cardiac index > 2.5 L/min/m² was weakly associated with better survival.

CONCLUSION

WHO functional class I or II, 6MWD ≥ 440 m and CI > 2.5 L/min/m² measured 12-16 weeks after the introduction of PAH-targeted therapy are associated with better long-term survival in PAH. Best survival is observed by reaching both the functional class and the 6MWD goals.

Evidence synthesis in pulmonary arterial hypertension: a systematic review and critical appraisal

BACKGROUND

The clinical landscape of pulmonary arterial hypertension (PAH) has evolved in terms of disease definition and classification, trial designs, available therapies and treatment strategies as well as clinical guidelines. This study critically appraises published evidence synthesis studies, i.e. meta-analyses (MA) and network-meta-analyses (NMA), to better understand their quality, validity and discuss the impact of the findings from these studies on current decision-making in PAH.

METHODS

A systematic literature review to identify MA/NMA studies considering approved and available therapies for treatment of PAH was conducted. Embase, Medline and the Cochrane's Database of Systematic Reviews were searched from database inception to April 22, 2020, supplemented by searches in health technology assessment websites. The International Society for Pharmacoeconomics and Outcomes Research (ISPOR) checklist covering six domains (relevance, credibility, analysis, reporting quality and transparency, interpretation and conflict of interest) was selected for appraisal of the included MA/NMA studies.

RESULTS

Fifty-two full publications (36 MAs, 15 NMAs, and 1 MA/NMA) in PAH met the inclusion criteria. The majority of studies were of low quality, with none of the studies being scored as 'strong' across all checklist domains. Key limitations included the lack of a clearly defined, relevant decision problem, shortcomings in assessing and addressing between-study heterogeneity, and an incomplete or misleading interpretation of results.

CONCLUSIONS

This is the first critical appraisal of published MA/NMA studies in PAH, suggesting low quality and validity of published evidence synthesis studies in this therapeutic area. Besides the need for direct treatment comparisons assessed in long-term randomized controlled trials, future efforts in evidence synthesis in PAH should improve analysis quality and scrutiny in order to meaningfully address challenges arising from an evolving therapeutic landscape.

Assessment of Right Ventricular Function in the Research Setting: Knowledge Gaps and Pathways Forward. An Official American Thoracic Society Research Statement

BACKGROUND

Right ventricular (RV) adaptation to acute and chronic pulmonary hypertensive syndromes is a significant determinant of short- and long-term outcomes. Although remarkable progress has been made in the understanding of RV function and failure since the meeting of the NIH Working Group on Cellular and Molecular Mechanisms of Right Heart Failure in 2005, significant gaps remain at many levels in the understanding of cellular and molecular mechanisms of RV responses to pressure and volume overload, in the validation of diagnostic modalities, and in the development of evidence-based therapies.

METHODS

A multidisciplinary working group of 20 international experts from the American Thoracic Society Assemblies on Pulmonary Circulation and Critical Care, as well as external content experts, reviewed the literature, identified important knowledge gaps, and provided recommendations.

RESULTS

This document reviews the knowledge in the field of RV failure, identifies and prioritizes the most pertinent research gaps, and provides a prioritized pathway for addressing these preclinical and clinical questions. The group identified knowledge gaps and research opportunities in three major topic areas: 1) optimizing the methodology to assess RV function in acute and chronic conditions in preclinical models, human studies, and clinical trials; 2) analyzing advanced RV hemodynamic parameters at rest and in response to exercise; and 3) deciphering the underlying molecular and pathogenic mechanisms of RV function and failure in diverse pulmonary hypertension syndromes.

CONCLUSIONS

This statement provides a roadmap to further advance the state of knowledge, with the ultimate goal of developing RV-targeted therapies for patients with RV failure of any etiology.

Dart to the target: an alternative bull's eye parametric display for European Society of Cardiology / European Respiratory Society goal-orientated risk reduction strategy in pulmonary arterial hypertension

Despite the significant mortality and mobidity benefits being obtained with the targeted therapies in patients with pulmonary arterial hypertension (PAH), mid- to long-term survival of patients with this disease has remained unsatisfactory. For earlier and reliable risk stratification in PAH and tailoring the dynamic management strategies, various risk assessment models have been developed. Currently available risk reduction strategy recommended by the European Society of Cardiology (ESC)/European Respiratory Society (ERS) 2015 Pulmonary Hypertension Guidelines has been utilized in three recent registries. In this review, we evaluated the risk prediction models and management algorithms in this setting and propose an alternative parametric display, a bull's eye, dart table scheme for ESC/ERS goal-orientated risk reduction strategy in patients with PAH.

Hepatoma-derived Growth Factor Predicts Disease Severity and Survival in Pulmonary Arterial Hypertension

RATIONALE

Pulmonary arterial hypertension (PAH) is a fatal disease, and pulmonary microvascular remodeling is an important contributor to PAH development. Therefore, we hypothesized that a circulating angiogenic factor could predict disease severity and survival.

OBJECTIVES

We sought to assess the relationship of serum hepatoma-derived growth factor (HDGF) with PAH disease severity and survival.

METHODS

Using a newly developed enzyme-linked immunosorbent assay, we evaluated circulating HDGF levels in two independent PAH cohorts and two different characterized control cohorts. Clinical and laboratory data were also used to assess the value of HDGF as a PAH prognostic biomarker.

MEASUREMENTS AND MAIN RESULTS

Serum HDGF levels were significantly elevated in two independent PAH cohorts. Importantly, serum HDGF levels were not elevated in a noncardiac chronic disease cohort. Further, patients with elevated HDGF had significantly lower exercise tolerance, worse New York Heart Association functional class, and higher levels of N-terminal pro-brain natriuretic peptide. HDGF was a strong predictor of mortality, with an unadjusted hazard ratio of 4.5 (95% confidence interval, 1.9-10.3; P = 0.003 by log-rank test). In multivariable Cox proportional hazards models, elevated HDGF levels predicted decreased survival after being adjusted for age, PAH subtype, invasive hemodynamics, and N-terminal pro-brain natriuretic peptide.

CONCLUSIONS

Elevated HDGF was associated with worse functional class, exertional intolerance, and increased mortality in PAH, suggesting HDGF as a potential biomarker for predicting mortality and as having possible diagnostic value for distinguishing PAH from non-PAH. HDGF may add additional value in PAH risk stratification in clinical trials and may represent a potential target for future PAH drug development.

Impaired Skeletal Muscle Oxygenation and Exercise Tolerance in Pulmonary Hypertension

BACKGROUND

Limb muscle dysfunction is documented in pulmonary arterial hypertension (PAH), but little is known regarding muscle oxygen (O2) supply and its possible effects on exercise tolerance in PAH.

METHODS

Ten patients with PAH and 10 matched controls underwent progressive maximal cardiopulmonary exercise test, voluntary and nonvolitional dominant quadriceps muscle strength measures, and nondominant quadriceps biopsy to assess maximal oxygen uptake, muscle function, and lower limb fiber type and capillarity, respectively. Both groups then performed normoxic and hyperoxic submaximal intensity exercise protocol at the same absolute workload during which muscle O2 supply was assessed by measuring changes in myoglobin-deoxyhemoglobin level (Δ[Mb-HHb]) and tissue oxygenation index in the dominant quadriceps using near-infrared spectroscopy. Changes in cardiac output, estimated systemic O2 delivery, and systemic O2 saturation were also assessed noninvasively throughout both submaximal exercises.

RESULTS

Patients with PAH displayed lower maximal oxygen uptake (P < 0.01), skeletal muscle strength (P < 0.05), and capillarity (P = 0.01). Throughout the normoxic submaximal exercise protocol, Δ[Mb-HHb] (P < 0.01) was higher whereas changes in tissue oxygenation index (P < 0.01) and systemic O2 saturation (P = 0.01) were lower in patients with PAH compared with those in controls. Conversely, changes in cardiac output and estimated systemic O2 delivery were similar between groups. Muscle oxygenation remained unchanged with O2 supplementation. Among variables known to influence tissue oxygenation, only quadriceps capillarity density correlated with Δ[Mb-HHb] (r = -0.66, P < 0.01), which in turn correlated with maximal oxygen uptake (r = -0.64, P < 0.01), 6-min walked distance (r = -0.74, P = 0.01), and both voluntary (r = -0.46, P = 0.04) and nonvolitional (r = -0.50, P = 0.02) quadriceps strength.

CONCLUSIONS

Capillary rarefaction within the skeletal muscle influences exercise tolerance and quadriceps strength at least partly through impaired muscle oxygen supply in PAH.

Ambrisentan and Tadalafil Up-front Combination Therapy in Scleroderma-associated Pulmonary Arterial Hypertension

BACKGROUND

Scleroderma-associated pulmonary arterial hypertension (SSc-PAH) is a rare disease characterized by a very dismal response to therapy and poor survival. We assessed the effects of up-front combination PAH therapy in patients with SSc-PAH.

METHODS

In this prospective, multicenter, open-label trial, 24 treatment-naive patients with SSc-PAH received ambrisentan 10 mg and tadalafil 40 mg daily for 36 weeks. Functional, hemodynamic, and imaging (cardiac magnetic resonance imaging and echocardiography) assessments at baseline and 36 weeks included changes in right ventricular (RV) mass and pulmonary vascular resistance as co-primary endpoints and stroke volume/pulmonary pulse pressure ratio, tricuspid annular plane systolic excursion, 6-minute walk distance, and N-terminal pro-brain natriuretic peptide as secondary endpoints.

RESULTS

At 36 weeks, we found that treatment had resulted in significant reductions in median (interquartile range [IQR]) RV mass (28.0 g [IQR, 20.6-32.9] vs. 32.5 g [IQR, 23.2-41.4]; P < 0.05) and median pulmonary vascular resistance (3.1 Wood units [IQR, 2.0-5.7] vs. 6.9 Wood units [IQR, 4.0-12.9]; P < 0.0001) and in improvements in median stroke volume/pulmonary pulse pressure ratio (2.6 ml/mm Hg [IQR, 1.8-3.5] vs. 1.4 ml/mm Hg [IQR 8.9-2.4]; P < 0.0001) and mean ( ± SD) tricuspid annular plane systolic excursion (2.2 ± 0.12 cm vs. 1.65 ± 0.11 cm; P < 0.0001), 6-minute walk distance (395 ± 99 m vs. 343 ± 131 m; P = 0.001), and serum N-terminal pro-brain natriuretic peptide (647 ± 1,127 pg/ml vs. 1,578 ± 2,647 pg/ml; P < 0.05).

CONCLUSIONS

Up-front combination therapy with ambrisentan and tadalafil significantly improved hemodynamics, RV structure and function, and functional status in treatment-naive patients with SSc-PAH and may represent a very effective therapy for this patient population. In addition, we identified novel hemodynamic and imaging biomarkers that could have potential value in future clinical trials. Clinical trial registered with www.clinicaltrials.gov (NCT01042158).

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.

Right atrial pressure/pulmonary artery wedge pressure ratio: A more specific predictor of survival in pulmonary arterial hypertension

BACKGROUND

Pulmonary arterial hypertension (PAH) is a progressive, fatal disease. Current prognostic models are not ideal, and identifying more accurate prognostic variables is needed. The objective of this study was to evaluate the relative prognostic value of the right atrial pressure/pulmonary artery wedge pressure (RAP/PAWP) ratio in PAH patients. We hypothesized that the RAP/PAWP ratio is more predictive of survival than any of the other measured or calculated hemodynamic variables.

METHODS

We performed a secondary analysis of a PAH cohort (Cohort 1) and validated our results in a separate cohort (Cohort 2). Cohort 1 included primarily patients enrolled in prospective, short-term, randomized clinical trials and subsequently followed long term. Cohort 2 included patients prospectively enrolled in a PAH registry at a tertiary PAH referral center.

RESULTS

Cohort 1 (n = 847) and Cohort 2 (n = 697) had a mean age of 47 and 54 years, respectively. Most were female (78% and 73%, respectively), Caucasian (83% and 82%), with advanced functional class disease status (New York Heart Association Functional Class III/IV 85% and 68%) and with significantly elevated hemodynamics (mean RAP/PAWP ratio: 1.2 and 1.0; pulmonary vascular resistance: 13.5 and 9.4 Wood units). RAP/PAWP ratio indicated a 1-year hazard ratio of 1.44 (p = 0.0001) and 1.35, respectively (p < 0.0001), and was the most consistently predictive hemodynamic variable across the 2 cohorts. These results remain valid even when adjusted for other covariables in multivariable regression models.

CONCLUSIONS

The RAP/PAWP ratio is a more specific predictor of survival than any other hemodynamic variable, and we recommend that it be used in clinical prognostication and PAH predictive models.

The changing paradigm in pulmonary hypertension trials: longer duration, new endpoints

PURPOSE OF REVIEW

Approved therapies for pulmonary arterial hypertension (PAH) currently consist of 12 agents, the majority of which were approved following short-term randomized clinical trials using change in 6 minute walk distance (6MWD) as the primary outcome. However, there is growing concern that significant improvements in this measure do not translate into morbidity and mortality benefits.

RECENT FINDINGS

As a result of data questioning the association between improvements in 6 minute walk distance and improvements in outcome, PAH clinical trial design is increasingly utilizing morbidity and mortality events as a composite primary outcome. This concept was recently illustrated in the published phase 3 trial of macitentan versus placebo, during which the clinical worsening event rate was decreased by 45%. Several additional unpublished trials have been similarly designed, all of which will require extended blinded treatment time in order to accrue sufficient event rates. The definition of morbidity events has varied across clinical studies; further standardization of this parameter is necessary.

SUMMARY

Although multiple direct and surrogate outcomes have been studied in PAH clinical research, rate of clinical worsening events, using prolonged, event-driven trial design, has emerged as the new standard.

Clinical Worsening as Composite Study End Point in Pediatric Pulmonary Arterial Hypertension

BACKGROUND

Clinical worsening (CW), an increasingly used composite end point in adult pulmonary arterial hypertension (PAH), has not yet been evaluated in pediatric PAH. This study aims to evaluate the usefulness of CW in pediatric PAH by assessing the event incidence and prognostic value of each separate component of CW and of the composite CW end point.

METHODS

Seventy pediatric patients with PAH from the Dutch National Network for Pediatric Pulmonary Hypertension, who started PAH-targeted therapy between January 2000 and January 2014, were included in the study and underwent standardized follow-up. The following CW components were prospectively registered: death, lung transplantation (LTx), PAH-related hospitalizations, initiation of IV prostanoids, and functional deterioration (World Health Organization functional-class deterioration, ≥ 15% decrease in 6-min walk distance, or both). The longitudinal event incidence and prognostic value were assessed for each separate component and their combination.

RESULTS

The end-point components of death, LTx, hospitalizations, initiation of IV prostanoids, and functional deterioration occurred with a longitudinal event rate of 10.1, 2.5, 21.4, 9.4 and 48.1 events per 100 person-years, respectively. The composite CW end point occurred 91.5 times per 100 person-years. The occurrences of either hospitalization, initiation of IV prostanoids, or functional deterioration were predictive of death or LTx (P < .001 for each component). In this cohort, 1-, 3-, and 5-year transplant-free survival was 76%, 64%, and 56%, respectively. Freedom from CW at 1, 3, and 5 years was 43%, 22%, and 17%, respectively.

CONCLUSIONS

CW occurred with a high event incidence and each of the soft end-point components was predictive of death or LTx. This supports the usefulness of CW as a study end point in clinical trials in pediatric PAH.

Medical treatment update on pulmonary arterial hypertension

Pulmonary arterial hypertension is a chronic, progressive disease of the pulmonary vasculature resulting in poor outcomes if left untreated. The management of group 1 pulmonary arterial hypertension has included the use of prostanoids, phosphodiesterase-5 inhibitors, and endothelin receptor antagonists targeting the prostacyclin, endothelin-1, and nitric oxide pathways. Three new medications have been approved by the US Food and Drug Administration over the past couple of years. Macitentan is the newest endothelin receptor antagonist, riociguat is a soluble guanylate cyclase stimulator, and treprostinil diolamine is the first oral prostanoid. This review will focus on the key trials leading to their approval, special considerations for each medication, and their potential place in therapy. The use of combination therapy as initial therapy in pulmonary arterial hypertension will also be discussed.

Use of outcome measures in pulmonary hypertension clinical trials

OBJECTIVES

To evaluate the use of surrogate measures in pulmonary hypertension (PH) clinical trials and how it relates to clinical practice.

BACKGROUND

Studies of pulmonary arterial hypertension (PAH) employ a variety of surrogate measures in addition to clinical events because of a small patient population, participant burden, and costs. The use of these measures in PH drug trials is poorly defined.

METHODS

We searched PubMed/MEDLINE/Embase for randomized or prospective cohort PAH clinical treatment trials from 1985 to 2013. Extracted data included intervention, trial duration, study design, patient characteristics, and primary and secondary outcome measures. To compare with clinical practice, we assessed the use of surrogate measures in a clinical sample of patients on PH medications at Duke University Medical Center between 2003 and 2014.

RESULTS

Between 1985 and 2013, 126 PAH trials were identified and analyzed. Surrogate measures served as primary endpoints in 119 trials (94.0%). Inclusion of invasive hemodynamics decreased over time (78.6%, 75.0%, 52.2%; P for trend = .02), while functional testing (7.1%, 60.0%, 81.5%; P for trend < .0001) and functional status or quality of life (0%, 47.6%, 62.8%; P for trend < .0001) increased in PAH trials over the same time periods. Echocardiography data were reported as a primary or secondary outcome in 32 trials (25.4%) with increased use from 1985-1994 to 1995-2004 (7.1% vs 35.0%, P = .04), but the trend did not continue to 2005-2013 (25.0%). In comparison, among 450 patients on PAH therapies at our institution between 2003 and 2013, clinical assessments regularly incorporated serial echocardiography and 6-minute walk distance tests (92% and 95% of patients, respectively) and repeat measurement of invasive hemodynamics (46% of patients).

CONCLUSIONS

The majority of PAH trials have utilized surrogate measures as primary endpoints. The use of these surrogate endpoints has evolved significantly over time with increasing use of patient-centered endpoints and decreasing or stable use of imaging and invasive measures. In contrast, imaging and invasive measures are commonly used in contemporary clinical practice. Further research is needed to validate and standardize currently used measures.

Physicians' and patients' expectations of therapies for pulmonary arterial hypertension: where do they meet?

In recent years, many new, effective therapies for pulmonary arterial hypertension (PAH) have become available and are widely used, yet the long-term prognosis for patients with PAH remains poor. In the absence of a cure, physicians' expectations of PAH-specific therapies are to: 1) improve patients' symptoms and functional capacity; 2) slow disease progression; and 3) improve survival. However, patients with PAH may prioritise other more tangible needs, such as improvements in their ability to carry out their daily tasks and increase their quality of life. Patients with PAH have also called out for social and emotional support from their physicians, caregivers, families and patient associations. Therefore, it is necessary that clinical trials of PAH-specific treatments include end-points that are meaningful to both patients and physicians, and that a multidisciplinary approach to the management of patients with PAH takes into consideration the broader aspects of patients' and caregivers' needs and wishes beyond simple physiological measurements.

Change of right heart size and function by long-term therapy with riociguat in patients with pulmonary arterial hypertension and chronic thromboembolic pulmonary hypertension

BACKGROUND

Riociguat is a soluble guanylate cyclase stimulator approved for pulmonary arterial hypertension (PAH) and chronic thromboembolic pulmonary hypertension (CTEPH). The objective of this study was to evaluate the change of right heart size and function assessed by echocardiography during long-term treatment with riociguat.

METHODS

We assessed patients who started riociguat treatment (1.0-2.5mg tid) within the trials PATENT, PATENTplus, EAS and CHEST and continued for 3-12 months. Echocardiography, 6-minute walking distance (6MWD) and further clinical parameters were analyzed at baseline, after 3, 6 and 12 months. Right heart catheterization was performed at baseline and after 3 months. For missing data we performed the last and baseline observation carried forward (LOCF, BOCF) method as sensitivity analyses.

RESULTS

Thirty-nine patients (21 PAH, 18 CTEPH, mean pulmonary arterial pressure 43 ± 2 mmHg, PVR 600 ± 43 dyn ∗ s ∗ cm(-5), 56.4% treatment-naïve) were included. Mean right ventricular (RV) area significantly decreased after 3 (-2.1 ± 3.9 cm(2), equals -7.4 ± 15.3%, p = 0.002), 6 (-4.2 ± 3.2 cm(2), equals -16.1 ± 11.5%, p < 0.001) and 12 months (-5.9 ± 4.6 cm(2), equals -22.1 ± 14.2%, p < 0.001) compared to baseline. Right atrial area significantly decreased after 12 months (-3.5 ± 4.1cm(2), equals -16.8 ± 19.2%, p < 0.001) and TAPSE significantly improved after 6 (+ 2 ± 4.7, equals 12 ± 25.8%, p = 0.025) and 12 months (+ 3.6 ± 5.4, equals 21.0 ± 29.6%, p = 0.002). Furthermore, RV wall thickness and 6MWD significantly improved after 3, 6 and 12 months (p < 0.05). Invasive hemodynamics significantly improved after 3 months. Both LOCF and BOCF showed similar significance and lower effect sizes.

CONCLUSION

Long-term treatment with riociguat significantly reduced right heart size and improved RV function in PAH and CTEPH. Further prospective studies are needed to confirm these results.

Experience with exercise right heart catheterization in the diagnosis of pulmonary hypertension: a retrospective study

BACKGROUND

Data on exercise pulmonary hemodynamics in healthy people and patients with pulmonary hypertension (PH) are rare. We analyzed exercise right heart catheterization (RHC) data in a symptomatic collective referred with suspected PH to characterize the differential response by diagnostic groups, to correlate resting with exercise hemodynamics, and to evaluate safety.

METHODS

This is a retrospective single-center study reviewing data from patients in whom an exercise RHC was performed between January 2006 and January 2013. Patients with follow-up RHC under PH -therapy were excluded.

RESULTS

Data from 101 patients were analyzed, none of them had an adverse event. In 35% we detected a resting PH (27.8% precapillary, 6.9% postcapillary). Exercise PH (mean pulmonary arterial pressure (mPAP) >30 mmHg at exercise) was found in 38.6%, whereas in 25.7% PH was excluded. We found a remarkable number of exercise PH in scleroderma patients, the majority being postcapillary. 83% of patients with mPAP-values between 20 and 24.9 mmHg at rest had exercise PH. Patients with resting PH had worse hemodynamics and were older compared with exercise PH ones.

CONCLUSION

In this real-life experience in symptomatic patients undergoing exercise RHC for suspected PH, we found that exercise RHC is safe. The facts that the vast majority of patients with mPAP-values between 20 and 24.9 mmHg at rest had exercise PH and the older age of patients with resting PH may indicate that exercise PH is a precursor of resting PH. Whether earlier treatment start in patients with exercise PH would stabilize the disease should be addressed in future studies.

Clinical value of echocardiographic Doppler-derived right ventricular dp/dt in patients with pulmonary arterial hypertension

AIMS

Right ventricular (RV) dp/dt is the instantaneous rate of RV pressure rise during early systole and is a surrogate marker of RV contractility. The main objective of this study was to evaluate the ability of echocardiographic Doppler obtained RV dp/dt to predict long-term survival in patients with pulmonary arterial hypertension (PAH) and chronic thrombo-embolic pulmonary hypertension (CTEPH).

METHODS AND RESULTS

Seventy-eight consecutive newly diagnosed untreated patients (64 ± 15 years, 71% female, 57% PAH, 43% inoperable CTEPH) were included in the study. At baseline, patients were assessed clinically [New York Heart Association (NYHA) and 6 minutes walking distance (6MWD)], by transthoracic cardiac ultrasound and by right heart catherization. RV dp/dt was assessed using spectral Doppler recordings from the tricuspid regurgitation signal at a sweep speed of 200 mm/s by measuring the time interval in which the regurgitant velocity increased from 0.5 to 2 m/s. During a mean follow-up period of 3.5 ± 1.7 years, 31 patients died and 3 received a lung transplant [study endpoint reached in 34/78 (44%) patients]. The optimal RV dp/dt cut-off was determined by receiver operating characteristic analysis at 3 years to be 410 mmHg/s (specificity 84%, positive-predictive value 55%, and negative-predictive value 83%). In univariate analysis, RV dp/dt <410 mmHg/s (hazard ratio 2.67, 95% CI 1.30-5.47, P = 0.007), tricuspid annulus plane systolic excursion (TAPSE) <15 mm, NYHA, 6MWD, and right atrial pressure were predictors of mortality. In a multivariate model with TAPSE, RV dp/dt remained an independent predictor of mortality (P = 0.01).

CONCLUSION

A reduced baseline RV dp/dt is a clear indicator of poor outcome independent of TAPSE in patients with PAH/CTEPH.

Are hemodynamics surrogate end points in pulmonary arterial hypertension?

BACKGROUND

Although frequently assessed in trials and clinical practice, hemodynamic response to therapy has never been validated as a surrogate end point for clinical events in pulmonary arterial hypertension (PAH).

METHODS AND RESULTS

We performed a patient-level pooled analysis of 4 randomized, placebo-controlled trials to determine whether treatment-induced changes in hemodynamic values at 12 weeks accounted for the relationship between treatment assignment and the probability of early clinical events (death, lung transplantation, atrial septostomy, PAH hospitalization, withdrawal for clinical worsening, or escalation in PAH therapy). We included 1119 subjects with PAH. The median (interquartile range) age was 48 years (37-59 years), and 23% were men. A total of 656 patients (59%) received active therapy (101 [15%] iloprost, 118 [18%] sitaxsentan, 204 [31%] sildenafil, and 233 [36%] subcutaneous treprostinil). Active treatment significantly lowered right atrial pressure, mean pulmonary artery pressure, and pulmonary vascular resistance and increased cardiac output and index (P<0.01 for all). Changes in hemodynamic values (except for right atrial pressure and mean pulmonary artery pressure) were significantly associated with the risk of a clinical event (P<0.02 for all). Although active treatment approximately halved the odds of a clinical event compared with placebo (P<0.001), changes in hemodynamics accounted for only 1.2% to 13.9% of the overall treatment effect.

CONCLUSIONS

Treatment-induced changes in hemodynamics at 12 weeks only partially explain the impact of therapy on the probability of early clinical events in PAH. These findings suggest that resting hemodynamics are not valid surrogate end points for short-term events in PAH clinical trials.