Right ventricular contractility in systemic sclerosis-associated and idiopathic pulmonary arterial hypertension

Right ventricle-pulmonary artery coupling in pulmonary artery hypertension its measurement and pharmacotherapy

The right ventricular (RV) function correlates with prognosis in severe pulmonary artery hypertension (PAH) but which metric of it is most clinically relevant is still uncertain. Clinical methods to estimate RV function from simplified pressure volume loops correlate with disease severity but the clinical relevance has not been assessed. Evaluation of right ventricle pulmonary artery coupling in pulmonary hypertensive patients may help to elucidate the mechanisms of right ventricular failure and may also help to identify patients at risk or guide the timing of therapeutic interventions in pulmonary hypertension. Complete evaluation of RV failure requires echocardiographic or magnetic resonance imaging, and right heart catheterization measurements. Treatment of RV failure in PAH relies on decreasing afterload with drugs targeting pulmonary circulation; fluid management to optimize ventricular diastolic interactions; and inotropic interventions to reverse cardiogenic shock. The ability to relate quantitative metrics of RV function in pulmonary artery hypertension to clinical outcomes can provide a powerful tool for management. Such metrics could also be utilized in the future as surrogate endpoints for outcomes and evaluation of response to therapies. This review of literature gives an insight on RV-PA coupling associated with PAH, its types of measurement and pharmacological treatment.

Pulmonary hypertension

Pulmonary hypertension encompasses a range of conditions directly or indirectly leading to elevated pressures within the pulmonary arteries. Five main groups of pulmonary hypertension are recognized, all defined by a mean pulmonary artery pressure of >20 mmHg: pulmonary arterial hypertension (rare), pulmonary hypertension associated with left-sided heart disease (very common), pulmonary hypertension associated with lung disease (common), pulmonary hypertension associated with pulmonary artery obstructions, usually related to thromboembolic disease (rare), and pulmonary hypertension with unclear and/or multifactorial mechanisms (rare). At least 1% of the world's population is affected, with a greater burden more likely in low-income and middle-income countries. Across all its forms, pulmonary hypertension is associated with adverse vascular remodelling with obstruction, stiffening and vasoconstriction of the pulmonary vasculature. Without proactive management this leads to hypertrophy and ultimately failure of the right ventricle, the main cause of death. In older individuals, dyspnoea is the most common symptom. Stepwise investigation precedes definitive diagnosis with right heart catheterization. Medical and surgical treatments are approved for pulmonary arterial hypertension and chronic thromboembolic pulmonary hypertension. There are emerging treatments for other forms of pulmonary hypertension; but current therapy primarily targets the underlying cause. There are still major gaps in basic, clinical and translational knowledge; thus, further research, with a focus on vulnerable populations, is needed to better characterize, detect and effectively treat all forms of pulmonary hypertension.

Functional and molecular determinants of right ventricular response to severe pulmonary hypertension in a large animal model

Right ventricular (RV) failure is the major determinant of outcome in pulmonary hypertension (PH). Calves exposed to 2-wk hypoxia develop severe PH and unlike rodents, hypoxia-induced PH in this species can lead to right heart failure. We, therefore, sought to examine the molecular and structural changes in the RV in calves with hypoxia-induced PH, hypothesizing that we could identify mechanisms underlying compensated physiological function in the face of developing severe PH. Calves were exposed to 14 days of environmental hypoxia (equivalent to 4,570 m/15,000 ft elevation, n = 29) or ambient normoxia (1,525 m/5,000 ft, n = 25). Cardiopulmonary function was evaluated by right heart catheterization and pressure volume loops. Molecular and cellular determinants of RV remodeling were analyzed by cDNA microarrays, RealTime PCR, proteomics, and immunochemistry. Hypoxic exposure induced robust PH, with increased RV contractile performance and preserved cardiac output, yet evidence of dysregulated RV-pulmonary artery mechanical coupling as seen in advanced disease. Analysis of gene expression revealed cellular processes associated with structural remodeling, cell signaling, and survival. We further identified specific clusters of gene expression associated with 1) hypertrophic gene expression and prosurvival mechanotransduction through YAP-TAZ signaling, 2) extracellular matrix (ECM) remodeling, 3) inflammatory cell activation, and 4) angiogenesis. A potential transcriptomic signature of cardiac fibroblasts in RV remodeling was detected, enriched in functions related to cell movement, tissue differentiation, and angiogenesis. Proteomic and immunohistochemical analysis confirmed RV myocyte hypertrophy, together with localization of ECM remodeling, inflammatory cell activation, and endothelial cell proliferation within the RV interstitium. In conclusion, hypoxia and hemodynamic load initiate coordinated processes of protective and compensatory RV remodeling to withstand the progression of PH.NEW & NOTEWORTHY Using a large animal model and employing a comprehensive approach integrating hemodynamic, transcriptomic, proteomic, and immunohistochemical analyses, we examined the early (2 wk) effects of severe PH on the RV. We observed that RV remodeling during PH progression represents a continuum of transcriptionally driven processes whereby cardiac myocytes, fibroblasts, endothelial cells, and proremodeling macrophages act to coordinately maintain physiological homeostasis and protect myocyte survival during chronic, severe, and progressive pressure overload.

Differences in right ventricular function and response to targeted therapy between patients with IPAH and PAH-CHD

Background and aims: Pulmonary arterial hypertension (PAH) is a chronic pulmonary vascular disorder characterized by elevated pulmonary vascular resistance (PVR) and pulmonary arterial pressure (PAP). Right heart failure is a life-threatening complication of PAH and predicts a poor prognosis. PAH associated with congenital heart disease (PAH-CHD) and idiopathic PAH (IPAH) are two prevalent PAH subtypes in China. In this section, we set out to explore baseline right ventricular (RV) function and its response to targeted agents between IPAH and PAH-CHD. Methods and results: Consecutive patients diagnosed with IPAH or PAH-CHD by right heart catheterization (RHC) in the Second Xiangya Hospital from November 2011 to June 2020 were included. All patients received PAH-targeted therapy and the RV function was assessed by echocardiography at baseline and during follow-up. A total of 303 patients (age, 36.23 ± 13.10 years; women, 213 (70.3%); mean PAP [mPAP], 63.54 ± 16.12 mmHg; PVR, 14.74 ± 7.61 WU) with IPAH (n = 121) or PAH-CHD (n = 182) were included in this study. Compared with PAH-CHD, patients with IPAH had worse baseline RV function. As of the latest follow-up, forty-nine patients with IPAH and six patients with PAH-CHD died. Kaplan-Meier analyses showed better survival in PAH-CHD versus IPAH. After PAH-targeted therapy, patients with IPAH had less improvement in 6 MWD, World Health Organization functional class, and RV functional parameters compared with patients with PAH-CHD. Conclusion: Compared with patients with PAH-CHD, patients with IPAH had worse baseline RV function, unfavourable prognosis, and inadequate response to targeted treatment.

Pulmonary Hypertension Associated with Connective Tissue Disease

Pulmonary hypertension (PH), a syndrome characterized by elevated pulmonary pressures, commonly complicates connective tissue disease (CTD) and is associated with increased morbidity and mortality. The incidence of PH varies widely between CTDs; patients with systemic sclerosis are most likely to develop PH. Several different types of PH can present in CTD, including PH related to left heart disease and respiratory disease. Importantly, CTD patients are at risk for developing pulmonary arterial hypertension, a rare form of PH that is associated with high morbidity and mortality. Future therapies targeting pulmonary vascular remodeling may improve outcomes for patients with this devastating disease.

The evaluation of right ventricle dyssynchrony by speckle tracking echocardiography in systemic sclerosis patients

PURPOSE

Systemic sclerosis (SSc) is associated with right ventricle (RV) remodeling and dysfunction. The primary aim of this study was to evaluate RV dyssynchrony (RV-Dys) in SSc patients using two-dimensional speckle tracking echocardiography (2D-STE).

METHODS

Fifty-five SSc patients with functional class I-II and 45 healthy controls were consecutively included and underwent 2D-STE. RV-Dys was defined as the standard deviation of time to peak strain of mid and basal segments of RV free wall and interventricular septum. SSc group was further classified according to the presence of pulmonary arterial hypertension (PAH). Patients with tricuspid regurgitant velocity >2.8 m/s with additional echocardiographic PAH signs were defined as SSc PAH (+).

RESULTS

SSc patients had lower RV longitudinal strain (RV-LS) (-17.6 ± 4.6% vs. -20.8 ± 2.8%, p < 0.001) and greater RV-Dys (49.9 ± 25.4 ms vs 24.3 ± 11.8 ms, p = 0.006) than controls despite no significant difference in conventional echocardiographic variables regarding RV function. Although SSc PAH(+) patients had lower RV-LS and higher RV-Dys than SSc PAH(-) patients, the differences were not statistically significant. The only independent predictor of RV-Dys was RV-LS (β:-0.324 [-3.89- -0.45]; p = 0.014).

CONCLUSION

SSc patients had not only reduced RV-LS but also impaired RV synchronicity even as conventional echocardiographic variables were preserved.

Indication of the prognosis of pulmonary hypertension by using CMR function parameters

OBJECTIVE

This study aimed to compare the cardiac function among different sub-types of pulmonary hypertension (PH) and to explore the independent predictors of major adverse cardiovascular events (MACE).

METHODS

Eighty-seven PH patients diagnosed by right heart catheterization (RHC) were recruited. Patients underwent cardiac magnetic resonance (CMR) and RHC examination within 2 weeks. The CMR images were analyzed to calculate the cardiac functional parameters including right ventricle (RV) and left ventricle (LV) end-diastolic volume index (EDVI), end-systolic volume index (ESVI), stroke volume index (SVI), ejection fraction (EF), tricuspid annular plane systolic excursion (TAPSE), and myocardial mass (MM). The median follow-up time was 46.5 months (interquartile range: 26-65.5 months), and the endpoints were the occurrence of MACE.

RESULTS

RVEDVI, LVEDVI, and LVESVI were higher in congenital heart disease-related PH (CHD-PH) than in other sub-types (p < 0.05). RVMM, RVSVI, and RVCI were highest in CHD-PH. There was no significant difference in the prognosis among different sub-types (p > 0.05). Comparing with the non-MACE group, RVEF, TAPSE, and LVSVI significantly decreased in the MACE group, while the RVESVI significantly increased (p < 0.05). TAPSE ≤ 15.65 mm and LVSVI ≤ 30.27 mL/m² were significant independent predictors of prognosis in PH patients.

CONCLUSION

CHD-PH had a higher RV function reserve but lowest LVEF comparing to other subgroups. TAPSE and LVSVI could contribute to the prediction of MACE in PH patients.

KEY POINTS

• CMR imaging is a noninvasive and accurate tool to assess ventricular function. • CHD-PH had higher RV function reserve but lowest LVEF. • TAPSE and LVSVI could contribute to the prediction of MACE in PH patients.

Animal models of pulmonary hypertension: Getting to the heart of the problem

Despite recent therapeutic advances, pulmonary hypertension (PH) remains a fatal disease due to the development of right ventricular (RV) failure. At present, no treatments targeted at the right ventricle are available, and RV function is not widely considered in the preclinical assessment of new therapeutics. Several small animal models are used in the study of PH, including the classic models of exposure to either hypoxia or monocrotaline, newer combinational and genetic models, and pulmonary artery banding, a surgical model of pure RV pressure overload. These models reproduce selected features of the structural remodelling and functional decline seen in patients and have provided valuable insight into the pathophysiology of RV failure. However, significant reversal of remodelling and improvement in RV function remains a therapeutic obstacle. Emerging animal models will provide a deeper understanding of the mechanisms governing the transition from adaptive remodelling to a failing right ventricle, aiding the hunt for druggable molecular targets.

The role of pulmonary arterial hypertension-targeted therapy in systemic sclerosis

Pulmonary arterial hypertension, categorized as group 1 pulmonary hypertension by the World Health Organization classification system, represents a major complication of systemic sclerosis resulting from pulmonary vascular involvement of the disease. The high mortality seen in systemic sclerosis-associated pulmonary arterial hypertension is likely due to the impairment of right ventricular systolic function and the coexistence of other non-group-1 pulmonary hypertension phenotypes that may negatively impact clinical response to pulmonary arterial hypertension-targeted therapy. This review highlights two areas of recent advances regarding the management of systemic sclerosis patients with pulmonary hypertension: the tolerability of pulmonary arterial hypertension-targeted therapy in the presence of mild to moderate interstitial lung disease and the potential clinical significance of the antifibrotic effect of soluble guanylate cyclase stimulators demonstrated in preclinical studies.

Haemodynamics and serial risk assessment in systemic sclerosis associated pulmonary arterial hypertension

The prognostic importance of follow-up haemodynamics and the validity of multidimensional risk assessment are not well established for systemic sclerosis (SSc)-associated pulmonary arterial hypertension (PAH).We assessed incident SSc-PAH patients to determine the association between clinical and haemodynamic variables at baseline and first follow-up right heart catheterisation (RHC) with transplant-free survival. RHC variables included cardiac index, stroke volume index (SVI), pulmonary arterial compliance and pulmonary vascular resistance. Risk assessment was performed according to the number of low-risk criteria: functional class I or II, 6-min walking distance (6MWD) >440 m, right atrial pressure <8 mmHg and cardiac index ≥2.5 L·min^-1·m^-2Transplant-free survival from diagnosis (n=513) was 87%, 55% and 35% at 1, 3 and 5 years, respectively. At baseline, 6MWD was the only independent predictor. A follow-up RHC was available for 353 patients (median interval 4.6 months, interquartile range 3.9-6.4 months). The 6MWD, functional class, cardiac index, SVI, pulmonary arterial compliance and pulmonary vascular resistance were independently associated with transplant-free survival at follow-up, with SVI performing better than other haemodynamic variables. 1-year outcomes were better with increasing number of low-risk criteria at baseline (area under the curve (AUC) 0.63, 95% CI 0.56-0.69) and at first follow-up (AUC 0.71, 95% CI 0.64-0.78).Follow-up haemodynamics and multidimensional risk assessment had greater prognostic significance than at baseline in SSc-PAH.

Inflammation in Right Ventricular Failure: Does It Matter?

Right ventricular (RV) failure is a common consequence of acute and chronic RV overload of pressure, such as after pulmonary embolism and pulmonary hypertension. It has been recently realized that symptomatology and survival of patients with pulmonary hypertension are essentially determined by RV function adaptation to increased afterload. Therefore, improvement of RV function and reversal of RV failure are treatment goals. Currently, the pathophysiology and the pathobiology underlying RV failure remain largely unknown. A better understanding of the pathophysiological processes involved in RV failure is needed, as there is no proven treatment for this disease at the moment. The present review aims to summarize the current understanding of the pathogenesis of RV failure, focusing on inflammation. We attempt to formally emphasize the importance of inflammation and associated representative inflammatory molecules and cells in the primum movens and development of RV failure in humans and in experimental models. We present inflammatory biomarkers and immune mediators involved in RV failure. We focus on inflammatory mediators and cells which seem to correlate with the deterioration of RV function and also explain how all these inflammatory mediators and cells might impact RV function adaptation to increased afterload. Finally, we also discuss the evidence on potential beneficial effects of targeted anti-inflammatory agents in the setting of acute and chronic RV failure.

Right Ventricular-Pulmonary Vascular Interactions

Accurate and comprehensive evaluation of right ventricular (RV)-pulmonary vascular (PV) interactions is critical to the assessment of cardiopulmonary function, dysfunction, and failure. Here, we review methods of quantifying RV-PV interactions and experimental results from clinical trials as well as large- and small-animal models based on pressure-volume analysis. We conclude by outlining critical gaps in knowledge that should drive future studies.

Role of cardiac inflammation in right ventricular failure

Right ventricular failure (RVF) is the main determinant of mortality in patients with pulmonary arterial hypertension (PAH). Although the exact pathophysiology underlying RVF remains unclear, inflammation may play an important role, as it does in left heart failure. Perivascular pulmonary artery and systemic inflammation is relatively well studied and known to contribute to the initiation and maintenance of the pulmonary vascular insult in PAH. However, less attention has been paid to the role of cardiac inflammation in RVF and PAH. Consistent with many other types of heart failure, cardiac inflammation, triggered by systemic and local stressors, has been shown in RVF patients as well as in RVF animal models. RV inflammation likely contributes to impaired RV contractility, maladaptive remodelling and a vicious circle between RV and pulmonary vascular injury. Although the potential to improve RV function through anti-inflammatory therapy has not been tested, this approach has been applied clinically in left ventricular failure patients, with variable success. Because inflammation plays a dual role in the development of both pulmonary vascular pathology and RVF, anti-inflammatory therapies may have a potential double benefit in patients with PAH and associated RVF.

Exercise-based evaluations and interventions for pulmonary hypertension with connective tissue disorders

INTRODUCTION

Exercise intolerance is a common and often significant limitation in pulmonary arterial hypertension (PAH). This intolerance greatly affects the quality of life and function of the individual with PAH, irrespective of its etiology. In PAH associated with connective tissue disorders (PAH-CTD), exercise intolerance is further amplified by the presence of coexisting musculoskeletal manifestations of CTD. The evaluation of exercise capacity and prescription for exercise training therefore becomes a challenge to the clinician. Areas covered: This review highlights factors contributing to exercise intolerance in PAH-CTD, evaluation methods of exercise capacity and an overview on exercise training and a roadmap for future research. Expert commentary: Exercise intolerance is a complex interplay of cardiovascular, pulmonary, and musculoskeletal systems. Data from cardiopulmonary exercise tests have shown predictive abilities for both diagnosis and prognosis. In its absence, the 6-min walk test can be used to provide similar information thereby making the role of exercise testing an invaluable evaluation method in PAH-CTD. Exercise training data in PAH-CTD are still sparse, though, data from PAH studies suggest potential benefit. However, more research is required in this area of testing and training for greater understanding on exercise hemodynamic, phenotypes, and training benefits.

Right Ventricle Remodeling and Function in Scleroderma Patients

Scleroderma, known also as systemic sclerosis (SSc), is a severe disease associated with high mortality rates, and right ventricular (RV) remodeling and dysfunction, along with pulmonary artery hypertension (PAH), are among the most important internal organ manifestations of this disease. PAH has a higher prevalence in patients with SSc compared to the general population and represents a significant predictor of mortality in SSc. In patients with SSc, the morphological remodeling and alteration of RV function begin even before the setting of PAH and lead to development of a specific adaptive pattern of the RV which is different from the one recorded in patients with IAPH. These alterations cause worse outcomes and increased mortality rates in SSc patients. Early detection of RV dysfunction and remodeling is possible using modern imaging tools currently available and can indicate the initiation of specific therapeutic measures before installation of PAH. The aim of this review is to summarize the current knowledge related to mechanisms involved in the remodeling and functional alteration of the RV in SSc patients.

Pulmonary arterial hypertension: pathogenesis and clinical management

Pulmonary hypertension is defined as a resting mean pulmonary artery pressure of 25 mm Hg or above. This review deals with pulmonary arterial hypertension (PAH), a type of pulmonary hypertension that primarily affects the pulmonary vasculature. In PAH, the pulmonary vasculature is dynamically obstructed by vasoconstriction, structurally obstructed by adverse vascular remodeling, and pathologically non-compliant as a result of vascular fibrosis and stiffening. Many cell types are abnormal in PAH, including vascular cells (endothelial cells, smooth muscle cells, and fibroblasts) and inflammatory cells. Progress has been made in identifying the causes of PAH and approving new drug therapies. A cancer-like increase in cell proliferation and resistance to apoptosis reflects acquired abnormalities of mitochondrial metabolism and dynamics. Mutations in the type II bone morphogenetic protein receptor (BMPR2) gene dramatically increase the risk of developing heritable PAH. Epigenetic dysregulation of DNA methylation, histone acetylation, and microRNAs also contributes to disease pathogenesis. Aberrant bone morphogenetic protein signaling and epigenetic dysregulation in PAH promote cell proliferation in part through induction of a Warburg mitochondrial-metabolic state of uncoupled glycolysis. Complex changes in cytokines (interleukins and tumor necrosis factor), cellular immunity (T lymphocytes, natural killer cells, macrophages), and autoantibodies suggest that PAH is, in part, an autoimmune, inflammatory disease. Obstructive pulmonary vascular remodeling in PAH increases right ventricular afterload causing right ventricular hypertrophy. In some patients, maladaptive changes in the right ventricle, including ischemia and fibrosis, reduce right ventricular function and cause right ventricular failure. Patients with PAH have dyspnea, reduced exercise capacity, exertional syncope, and premature death from right ventricular failure. PAH targeted therapies (prostaglandins, phosphodiesterase-5 inhibitors, endothelin receptor antagonists, and soluble guanylate cyclase stimulators), used alone or in combination, improve functional capacity and hemodynamics and reduce hospital admissions. However, these vasodilators do not target key features of PAH pathogenesis and have not been shown to reduce mortality, which remains about 50% at five years. This review summarizes the epidemiology, pathogenesis, diagnosis, and treatment of PAH.

Vascular narrowing in pulmonary arterial hypertension is heterogeneous: rethinking resistance

In idiopathic pulmonary arterial hypertension (PAH), increased pulmonary vascular resistance is associated with structural narrowing of small (resistance) vessels and increased vascular tone. Current information on pulmonary vascular remodeling is mostly limited to averaged increases in wall thickness, but information on number of vessels affected and internal diameter decreases for vessels of different sizes is limited. Our aim was to quantify numbers of affected vessels and their internal diameter decrease for differently sized vessels in PAH in comparison with non‐PAH patients. Internal and external diameters of transversally cut vessels were measured in five control subjects and six PAH patients. Resistance vessels were classified in Strahler orders, internal diameters 13 μm (order 1) to 500 μm (order 8). The number fraction, that is, percentage of affected vessels, and the internal diameter fraction, that is, percentage diameter of normal diameter, were calculated. In PAH, not all resistance vessels are affected. The number fraction is about 30%, that is, 70% of vessels have diameters not different from vessels of control subjects. Within each order, the decrease in diameter of affected vessels is variable with an averaged diameter fraction of 50–70%. Narrowing of resistance vessels is heterogeneous: not all vessels are narrowed, and the decrease in internal diameters, even within a single order, vary largely. This heterogeneous narrowing alone cannot explain the large resistance increase in PAH. We suggest that rarefaction could be an important contributor to the hemodynamic changes.

A novel single-beat approach to assess right ventricular systolic function

Clinical assessment of right ventricular (RV) contractility in diseases such as pulmonary arterial hypertension (PAH) has been hindered by the lack of a robust methodology. Here, a novel, clinically viable, single-beat method was developed to assess end-systolic elastance (E_es), a measure of right ventricular (RV) contractility. We hypothesized that this novel approach reduces uncertainty and interobserver variability in the estimation of the maximum isovolumic pressure (P_iso), the key step in single-beat methods. The new method was designed to include a larger portion of the RV pressure data and minimize subjective adjustments by the operator. Data were obtained from right heart catheterization of PAH patients in a multicenter prospective study ( data set 1) and a single-center retrospective study ( data set 2). To obtain P_iso, three independent observers used an established single-beat method (based on the first derivative of the pressure waveform) and the novel method (based on the second derivative). Interobserver variability analysis included paired t-test, one-way ANOVA, interclass correlation (ICC) analysis, and a modified Bland-Altman analysis. The P_iso values obtained from the two methods were linearly correlated for both data set 1 ( R² = 0.74) and data set 2 ( R² = 0.91). Compared with the established method, the novel method resulted in smaller interobserver variability ( P < 0.001), nonsignificant differences between observers, and a narrower confidence interval. By reducing uncertainty and interobserved variability, this novel approach may pave the way for more effective clinical management of PAH. NEW & NOTEWORTHY A novel methodology to assess right ventricular contractility from clinical data is demonstrated. This approach significantly reduces interobserver variability in the analysis of ventricular pressure data, as demonstrated in a relatively large population of subjects with pulmonary hypertension. This study may enable more accurate clinical monitoring of systolic function in subjects with pulmonary hypertension.

Epigenetics, inflammation and metabolism in right heart failure associated with pulmonary hypertension

Right ventricular failure (RVF) is the most important prognostic factor for both morbidity and mortality in pulmonary arterial hypertension (PAH), but also occurs in numerous other common diseases and conditions, including left ventricle dysfunction. RVF remains understudied compared with left ventricular failure (LVF). However, right and left ventricles have many differences at the morphological level or the embryologic origin, and respond differently to pressure overload. Therefore, knowledge from the left ventricle cannot be extrapolated to the right ventricle. Few studies have focused on the right ventricle and have permitted to increase our knowledge on the right ventricular-specific mechanisms driving decompensation. Here we review basic principles such as mechanisms accounting for right ventricle hypertrophy, dysfunction, and transition toward failure, with a focus on epigenetics, inflammatory, and metabolic processes.

Idiopathic and Systemic Sclerosis-Associated Pulmonary Arterial Hypertension: A Comparison of Demographic, Hemodynamic, and MRI Characteristics and Outcomes

BACKGROUND

Previous studies have identified survival in systemic sclerosis (SSc)-associated pulmonary arterial hypertension (SSc-PAH) as being worse than in idiopathic pulmonary arterial hypertension (IPAH). We investigated differences between these conditions by comparing demographic, hemodynamic, and radiological characteristics and outcomes in a large cohort of incident patients.

METHODS

Six hundred fifty-one patients diagnosed with IPAH or SSc-associated precapillary pulmonary hypertension were included. Patients with pulmonary disease or two or more risk factors for left heart disease were identified, leaving a primary analysis set of 375 subjects. Subgroup analysis using cardiac magnetic resonance (CMR) imaging was performed.

RESULTS

Median survival was 7.8 years in IPAH and 3 years in SSc-PAH (P < .001). Patients with SSc-PAH were older with less severe hemodynamics but lower gas transfer (diffusing capacity for carbon monoxide [Dlco]). Independent prognostic factors were age, SSc, Dlco, pulmonary artery saturation, and stroke volume. After excluding patients with normal or only mildly elevated resistance, there was no difference in the relationship between pulmonary vascular resistance (PVR) and compliance in IPAH and SSc-PAH. The relationship between mean pulmonary arterial pressure (mPAP) and systolic pulmonary arterial pressure (sPAP) in IPAH was identical to that previously reported (mPAP = 0.61 sPAP + 2 mm Hg). The relationship in SSc-PAH was similar: mPAP = 0.58 sPAP + 2 mm Hg (P value for difference with IPAH = 0.095). The correlation between ventricular mass index assessed at CMR imaging and PVR was stronger in SSc-PAH.

CONCLUSIONS

The reasons for poorer outcomes in SSc-PAH are likely to be multifactorial, including but not limited to older age and reduced gas transfer.

Survival protection by bodyweight in isolated scleroderma-related pulmonary artery hypertension

In chronic heart failure (CHF) due to systemic cardiovascular disease, obese patients have better survival. Bodyweight versus survival was analyzed post hoc in subjects with limited scleroderma (SSc) and isolated pulmonary artery hypertension (PAH), i.e. with CHF due to pulmonary vascular disease. Rheumatologists referred scleroderma subjects for evaluation, and PAH was ascertained by right heart catheterization (RHC). Forty-nine SSc-PAH subjects were stratified by body mass index (BMI): obese 7 (14.3 %), overweight 11 (22.4 %), normal weight 21 (42.9 %), and underweight 10 (20.4 %) for 24-month follow-up and pooled together for long-term 72-month follow-up. Survival was analyzed by Kaplan-Meier method. Multivariate Cox proportional hazards modeling helped to assess variables associated to survival. At 24 months (17 events), survival increases with BMI across four groups (logrank for trend P = 0.031). By Cox multivariate mortality, best model included: BMI (P = 0.043), low lung diffusion (DLco, P = 0.007), and reduced stroke volume index (SVI, P = 0.017). At 72 month (37 events), higher BMI values were associated with better survival but not significantly (P = 0.076). By multivariate modeling BMI did not enter any model, whereas low DLco entered all (P < 0.001). Also low SVI (P = 0.02) and low mixed venous saturation (SvO2, P = 0.009) were associated with the prognosis. From PAH diagnosis to final event, BMI had small (5.4 %), but significant decline (P < 0.001). This is ascribed to CHF progression, and may explain BMI predictive power weakening. The results suggest BMI decline should be contrasted, DLco is useful for screening and with SVI and SvO2 for assessing prognosis and treatment.

Adverse Events in Connective Tissue Disease-Associated Pulmonary Arterial Hypertension

OBJECTIVE

Patients with connective tissue disease (CTD)-associated pulmonary arterial hypertension (PAH) have a poorer prognosis compared to those with idiopathic PAH, but little is known about the differences in treatment-related adverse events (AEs) and serious adverse events (SAEs) between these groups. This study was undertaken to characterize these differences.

METHODS

Individual patient-level data from 10 randomized controlled trials of therapies for PAH were obtained from the US Food and Drug Administration. Patients diagnosed as having either CTD-associated PAH or idiopathic PAH were included. A treatment-by-diagnosis interaction term was used to examine whether the effect of treatment on occurrence of AEs differed between patients with CTD-associated PAH and those with idiopathic PAH. Studies were pooled using fixed-effect models.

RESULTS

The study sample included 2,370 participants: 716 with CTD-associated PAH and 1,654 with idiopathic PAH. In the active treatment group compared to the placebo group, the risk of AEs was higher among patients with CTD-associated PAH than among those with idiopathic PAH (odds ratio [OR] 1.57, 95% confidence interval [95% CI] 1.00-2.47 versus OR 0.94, 95% CI 0.69-1.26; P for interaction = 0.061), but there was no difference in the risk of SAEs in analyses adjusted for age, race, sex, hemodynamic findings, and laboratory values. Despite the higher occurrence of AEs in patients with CTD-associated PAH assigned to active therapy compared to those receiving placebo, the risk of drug discontinuation due to an AE was similar to that in patients with idiopathic PAH assigned to active therapy (P for interaction = 0.27).

CONCLUSION

Patients with CTD-associated PAH experienced more treatment-related AEs compared to those with idiopathic PAH in therapeutic clinical trials. These findings suggest that the overall benefit of advanced therapies for PAH may be attenuated by the greater frequency of AEs.

Effects of ranolazine on exercise capacity, right ventricular indices, and hemodynamic characteristics in pulmonary arterial hypertension: a pilot study

Ranolazine, a late inward sodium current and fatty acid oxidation inhibitor, may improve right ventricular (RV) function in pulmonary arterial hypertension (PAH); however, the safety and efficacy of ranolazine in humans with PAH is unknown. Therefore, we sought to (1) determine whether ranolazine is safe and well tolerated in PAH and (2) explore ranolazine's effect on symptoms, exercise capacity, RV structure and function, and hemodynamic characteristics. We therefore conducted a 3-month, prospective, open-label pilot study involving patients with symptomatic PAH (n = 11) and echocardiographic evidence of RV dysfunction. We evaluated the safety and tolerability of ranolazine and compared symptoms, exercise capacity, exercise bicycle echocardiographic parameters, and invasive hemodynamic parameters between baseline and 3 months of ranolazine therapy using paired t tests. Of the 11 patients enrolled, one discontinued ranolazine therapy due to a drug-drug interaction after 3 days of therapy. All 10 of the remaining patients continued therapy for 3 months, and 8 (80%) of 10 completed all study tests. After 3 months, ranolazine administration was safe and associated with improvement in functional class (P = 0.0013), reduction in RV size (P = 0.015), improved RV function (improvement in RV strain during exercise at 3 months; P = 0.037), and a trend toward improved exercise time and exercise watts on bicycle echocardiography (P = 0.06 and 0.01, respectively). Ranolazine was not associated with improvement in invasive hemodynamic parameters. In conclusion, in a pilot study involving PAH, ranolazine therapy was safe and well tolerated, and it resulted in improvement in symptoms and echocardiographic parameters of RV structure and function but did not alter invasive hemodynamic parameters. ClinicalTrials.gov Identifier: NCT01174173.

The right ventricle in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a right heart failure syndrome. In early-stage PAH, the right ventricle tends to remain adapted to afterload with increased contractility and little or no increase in right heart chamber dimensions. However, less than optimal right ventricular (RV)-arterial coupling may already cause a decreased aerobic exercise capacity by limiting maximum cardiac output. In more advanced stages, RV systolic function cannot remain matched to afterload and dilatation of the right heart chamber progressively develops. In addition, diastolic dysfunction occurs due to myocardial fibrosis and sarcomeric stiffening. All these changes lead to limitation of RV flow output, increased right-sided filling pressures and under-filling of the left ventricle, with eventual decrease in systemic blood pressure and altered systolic ventricular interaction. These pathophysiological changes account for exertional dyspnoea and systemic venous congestion typical of PAH. Complete evaluation of RV failure requires echocardiographic or magnetic resonance imaging, and right heart catheterisation measurements. Treatment of RV failure in PAH relies on: decreasing afterload with drugs targeting pulmonary circulation; fluid management to optimise ventricular diastolic interactions; and inotropic interventions to reverse cardiogenic shock. To date, there has been no report of the efficacy of drug treatments that specifically target the right ventricle.

The striated muscles in pulmonary arterial hypertension: adaptations beyond the right ventricle

Pulmonary arterial hypertension (PAH) is a fatal lung disease characterised by progressive remodelling of the small pulmonary vessels. The daily-life activities of patients with PAH are severely limited by exertional fatigue and dyspnoea. Typically, these symptoms have been explained by right heart failure. However, an increasing number of studies reveal that the impact of the PAH reaches further than the pulmonary circulation. Striated muscles other than the right ventricle are affected in PAH, such as the left ventricle, the diaphragm and peripheral skeletal muscles. Alterations in these striated muscles are associated with exercise intolerance and reduced quality of life. In this Back to Basics article on striated muscle function in PAH, we provide insight into the pathophysiological mechanisms causing muscle dysfunction in PAH and discuss potential new therapeutic strategies to restore muscle dysfunction.

Right ventricular remodeling in idiopathic and scleroderma-associated pulmonary arterial hypertension: two distinct phenotypes

Patients with scleroderma (SSc)-associated pulmonary arterial hypertension (PAH) have worse survival than patients with idiopathic PAH (IPAH). We hypothesized that the right ventricle (RV) adapts differently in SSc-PAH versus IPAH. We used cardiac magnetic resonance imaging (cMRI) and hemodynamic characteristics to assess the relationship between RV morphology and RV load in patients with SSc-PAH and IPAH. In 53 patients with PAH (35 with SSc-PAH and 18 with IPAH) diagnosed by right heart catheterization (RHC), we examined cMRIs obtained within 48 hours of RHC and compared RV morphology between groups. Regression analysis was used to assess the association between diagnosis (IPAH vs. SSc-PAH) and RV measurements after adjusting for age, sex, race, body mass index (BMI), left ventricular (LV) mass, and RV load. There were no significant differences in unadjusted comparisons of cMRI measurements between the two groups. Univariable regression showed RV mass index (RVMI) was linearly associated with measures of RV load in both the overall cohort and within each group. Multivariable linear regression models revealed a significant interaction between disease type and RVMI adjusting for pulmonary vascular resistance (PVR), age, sex, race, BMI, and LV mass. This model showed a decreased slope in the relationship between RVMI and PVR in the SSc-PAH group compared with the IPAH group. RVMI varies linearly with measures of RV load. After adjusting for multiple potential confounders, patients with SSc-PAH demonstrated significantly less RV hypertrophy with increasing PVR than patients with IPAH. This difference in adaptive hypertrophy may in part explain previously observed decreased contractility and poorer survival in SSc-PAH.

Biomechanics of the right ventricle in health and disease (2013 Grover Conference series)

Right ventricular (RV) function is a major determinant of the symptomatology and outcome in pulmonary hypertension. The normal RV is a thin-walled flow generator able to accommodate large changes in venous return but unable to maintain flow output in the presence of a brisk increase in pulmonary artery pressure. The RV chronically exposed to pulmonary hypertension undergoes hypertrophic changes and an increase in contractility, allowing for preserved flow output in response to peripheral demand. Failure of systolic function adaptation (homeometric adaptation, described by Anrep's law of the heart) results in increased dimensions (heterometric adaptation; Starling's law of the heart), with a negative effect on diastolic ventricular interactions, limitation of exercise capacity, and vascular congestion. Ventricular function is described by pressure-volume relationships. The gold standard of systolic function is maximum elastance (E max), or the maximal value of the ratio of pressure to volume. This value is not immediately sensitive to changes in loading conditions. The gold standard of afterload is arterial elastance (E a), defined by the ratio of pressure at E max to stroke volume. The optimal coupling of ventricular function to the arterial circulation occurs at an E max/E a ratio between 1.5 and 2. Patients with severe pulmonary hypertension present with an increased E max, a trend toward decreased E max/E a, and increased RV dimensions, along with progression of the pulmonary vascular disease, systemic factors, and left ventricular function. The molecular mechanisms of RV systolic failure are currently being investigated. It is important to refer biological findings to sound measurements of function. Surrogates for E max and E a are being developed through bedside imaging techniques.

Physiology of the pulmonary circulation and the right heart

The pulmonary circulation is a high-flow and low-pressure circuit. The functional state of the pulmonary circulation is defined by pulmonary vascular pressure-flow relationships conforming to distensible vessel models with a correction for hematocrit. The product of pulmonary arterial compliance and resistance is constant, but with a slight decrease as a result of increased pulsatile hydraulic load in the presence of increased venous pressure or proximal pulmonary arterial obstruction. An increase in left atrial pressure is transmitted upstream with a ratio ≥1 for mean pulmonary artery pressure and ≤1 the diastolic pulmonary pressure. Therefore, the diastolic pressure gradient is more appropriate than the transpulmonary pressure gradient to identify pulmonary vascular disease in left heart conditions. Exercise is associated with a decrease in pulmonary vascular resistance and an increase in pulmonary arterial compliance. Right ventricular function is coupled to the pulmonary circulation with an optimal ratio of end-systolic to arterial elastances of 1.5-2.

Saudi Guidelines on the Diagnosis and Treatment of Pulmonary Hypertension: Pulmonary arterial hypertension associated with connective tissue diseases

The explosive growth of medical literature on pulmonary hypertension (PH) has led to a steady increase in awareness of this disease within the medical community during the past decade. The recent revision of the classification of PH is presented in in the main guidelines.

Group 1 PH or pulmonary arterial hypertension (PAH) is a heterogeneous group and includes PH due to inheritable, drug-induced, and toxin-induced causes and to such underlying systemic causes as connective tissue diseases, human immunodeficiency viral infection, portal hypertension, congenital heart disease, and schistosomiasis.

Systemic sclerosis (SSc) is an autoimmune multisystem disorder, which affects over 240 persons per million in the United States.[1] Its manifestations are not confined to the skin but may also involve the lungs, kidneys, peripheral circulation, musculoskeletal system, gastrointestinal tract, and heart.

The outcome of PAH associated with SSc is worse when compared to other subtypes of PAH.

In this review, we summarize available information about the pulmonary vascular and cardiac manifestations of SSc with special emphasis on their prognostic implications as well as the peculiarity of their detection.

Improved survival in limited scleroderma-related pulmonary artery hypertension

Reportedly, patients with scleroderma-related pulmonary hypertension (SSc-PAH) respond poorly to new vasoactive drugs (NVD). Forty-nine SSc-PAH patients underwent right heart catheterization (RHC) and, according to NVD availability, divided as follows: Group 1 (n = 23, from 1999 to 2004, poor availability), and Group 2 (n = 26, from 2005 to 2010, good availability). Before diagnostic RHC, NVD had been given to 30 % of the patients in Group 1, and 58 % of those in Group 2 (p = 0.049). At diagnosis, patients in Group 1 had greater heart dilatation (p < 0.01), higher mean pulmonary artery pressure (p < 0.05), lower pulmonary artery capacitance (p < 0.05), and lower carbon monoxide lung diffusing capacity (DLco, p < 0.05) than those in Group 2. At a median follow-up time of 15.5 months, DLco further decreased in Group 1 (p < 0.05), whereas cardiac index increased in Group 2 (p < 0.05). At 36 months of follow-up, 72.4 % of the patients in Group 2 were still alive as opposed to 30.4 % in Group 1 (p = 0.02). In multivariate analysis, DLco and mixed venous oxygen saturation (SvO2) were independent predictors of survival. A value of DLco <7.2 mL/mmHg/min was associated with a hazard ratio (HR) of 5.3 (p < 0.001); for SvO2 <63.8 %, the HR was 3.7 (p < 0.01).NVD have beneficial effects in patients with SSc-PAH. Both DLco and SvO2 are predictors of survival and may assist in planning treatment.

Ambrisentan therapy in pulmonary hypertension: clinical use and tolerability in a referral centre

INTRODUCTION

Ambrisentan is an oral selective endothelin receptor antagonist licensed for use in pulmonary arterial hypertension (PAH). There are few data on clinical use and long-term tolerability in a wider range of patients with pulmonary hypertension (PH).

METHODS

All patients treated with ambrisentan over a 4-year period were identified. Baseline characteristics, liver function test (LFT) results and World Health Organization (WHO) functional class were retrieved from hospital databases.

RESULTS

272 patients received ambrisentan between March 2009 and June 2013 (32% idiopathic PAH, 36% connective tissue disease PAH, 11% congenital heart disease PAH, 6% portopulmonary hypertension, 1% HIV PAH, 4% PH in association with lung disease, 8% chronic thromboembolic PH and 2% PH in association with sarcoidosis). 33.5% of patients received ambrisentan as monotherapy and 12% received ambrisentan as their initial PH therapy. 18% stopped treatment due to side effects and 12% stopped due to lack of efficacy. Oedema was the most common side effect leading to cessation of therapy, which occurred in 7% of patients. 57% of patients who discontinued ambrisentan due to side effects also discontinued other PAH therapies due to side effects previously or subsequently. Ambrisentan was discontinued in two (<1%) patients due to abnormal LFTs. The 3-year survival in congenital heart disease PAH, idiopathic PAH and systemic sclerosis-associated PAH was 80%, 62%, and 38%, respectively (p = 0.003). Survival was superior in patients in whom WHO functional class improved in response to therapy.

CONCLUSION

Ambrisentan is used as an initial therapy and as monotherapy in a minority of patients in a large UK PH referral centre. Discontinuation due to side effects, and especially oedema, was higher than reported in previous studies while discontinuation due to abnormal LFTs was very uncommon. A majority of patients who discontinued therapy due to side effects also previously or subsequently discontinued other PAH therapies. Improvement in WHO functional class was associated with superior survival.

Therapies for scleroderma-related pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH), a common complication of systemic sclerosis, carries a very severe prognosis and is one of the leading causes of death in patients who suffer from it. Indeed, response to modern medical therapy has been disappointing in scleroderma-related PAH compared with other forms of PAH from the WHO group 1 classification of diseases, despite similar histological changes involving the pulmonary vasculature. This review discusses specific features of scleroderma-related PAH, currently available and US FDA-approved therapy for this syndrome, as well as potential future therapeutic developments based on newly acquired knowledge of this disorder.

Right ventricular dysfunction in systemic sclerosis-associated pulmonary arterial hypertension

BACKGROUND

Systemic sclerosis–associated pulmonary artery hypertension (SScPAH) has a worse prognosis compared with idiopathic pulmonary arterial hypertension (IPAH), with a median survival of 3 years after diagnosis often caused by right ventricular (RV) failure. We tested whether SScPAH or systemic sclerosis–related pulmonary hypertension with interstitial lung disease imposes a greater pulmonary vascular load than IPAH and leads to worse RV contractile function.

METHODS AND RESULTS

We analyzed pulmonary artery pressures and mean flow in 282 patients with pulmonary hypertension (166 SScPAH, 49 systemic sclerosis–related pulmonary hypertension with interstitial lung disease, and 67 IPAH). An inverse relation between pulmonary resistance and compliance was similar for all 3 groups, with a near constant resistance×compliance product. RV pressure–volume loops were measured in a subset, IPAH (n=5) and SScPAH (n=7), as well as SSc without PH (n=7) to derive contractile indexes (end-systolic elastance [Ees] and preload recruitable stroke work [Msw]), measures of RV load (arterial elastance [Ea]), and RV pulmonary artery coupling (Ees/Ea). RV afterload was similar in SScPAH and IPAH (pulmonary vascular resistance=7.0±4.5 versus 7.9±4.3 Wood units; Ea=0.9±0.4 versus 1.2±0.5 mm Hg/mL; pulmonary arterial compliance=2.4±1.5 versus 1.7±1.1 mL/mm Hg; P>0.3 for each). Although SScPAH did not have greater vascular stiffening compared with IPAH, RV contractility was more depressed (Ees=0.8±0.3 versus 2.3±1.1, P<0.01; Msw=21±11 versus 45±16, P=0.01), with differential RV-PA uncoupling (Ees/Ea=1.0±0.5 versus 2.1±1.0; P=0.03). This ratio was higher in SSc without PH (Ees/Ea=2.3±1.2; P=0.02 versus SScPAH).

CONCLUSIONS

RV dysfunction is worse in SScPAH compared with IPAH at similar afterload, and may be because of intrinsic systolic function rather than enhanced pulmonary vascular resistive and pulsatile loading.

Endothelial injury in a transforming growth factor β-dependent mouse model of scleroderma induces pulmonary arterial hypertension

OBJECTIVE

To delineate the constitutive pulmonary vascular phenotype of the TβRIIΔk-fib mouse model of scleroderma, and to selectively induce pulmonary endothelial cell injury using vascular endothelial growth factor (VEGF) inhibition to develop a model with features characteristic of pulmonary arterial hypertension (PAH).

METHODS

The TβRIIΔk-fib mouse strain expresses a kinase-deficient transforming growth factor β (TGFβ) receptor type II driven by a fibroblast-specific promoter, leading to ligand-dependent up-regulation of TGFβ signaling, and replicates key fibrotic features of scleroderma. Structural, biochemical, and functional assessments of pulmonary vessels, including in vivo hemodynamic studies, were performed before and following VEGF inhibition, which induced pulmonary endothelial cell apoptosis. These assessments included biochemical analysis of the TGFβ and VEGF signaling axes in tissue sections and explanted smooth muscle cells.

RESULTS

In the TβRIIΔk-fib mouse strain, a constitutive pulmonary vasculopathy with medial thickening, a perivascular proliferating chronic inflammatory cell infiltrate, and mildly elevated pulmonary artery pressure resembled the well-described chronic hypoxia model of pulmonary hypertension. Following administration of SU5416, the pulmonary vascular phenotype was more florid, with pulmonary arteriolar luminal obliteration by apoptosis-resistant proliferating endothelial cells. These changes resulted in right ventricular hypertrophy, confirming hemodynamically significant PAH. Altered expression of TGFβ and VEGF ligand and receptor was consistent with a scleroderma phenotype.

CONCLUSION

In this study, we replicated key features of systemic sclerosis-related PAH in a mouse model. Our results suggest that pulmonary endothelial cell injury in a genetically susceptible mouse strain triggers this complication and support the underlying role of functional interplay between TGFβ and VEGF, which provides insight into the pathogenesis of this disease.

Metabolism and bioenergetics in the right ventricle and pulmonary vasculature in pulmonary hypertension

Pulmonary arterial hypertension (PAH) is a syndrome in which pulmonary vascular cross sectional area and compliance are reduced by vasoconstriction, vascular remodeling, and inflammation. Vascular remodeling results in part from increased proliferation and impaired apoptosis of vascular cells. The resulting increase in afterload promotes right ventricular hypertrophy (RVH) and RV failure. Recently identified mitochondrial-metabolic abnormalities in PAH, notably pyruvate dehydrogenase kinase-mediated inhibition of pyruvate dehydrogenase (PDH), result in aerobic glycolysis in both the lung vasculature and RV. This glycolytic shift has diagnostic importance since it is detectable early in experimental PAH by increased lung and RV uptake of ¹⁸F-fluorodeoxyglucose on positron emission tomography. The metabolic shift also has pathophysiologic and therapeutic relevance. In RV myocytes, the glycolytic switch reduces contractility while in the vasculature it renders cells hyperproliferative and apoptosis-resistant. Reactivation of PDH can be achieved directly by PDK inhibition (using dichloroacetate), or indirectly via activating the Randle cycle, using inhibitors of fatty acid oxidation (FAO), trimetazidine and ranolazine. In experimental PAH and RVH, PDK inhibition increases glucose oxidation, enhances RV function, regresses pulmonary vascular disease by reducing proliferation and enhancing apoptosis, and restores cardiac repolarization. FAO inhibition increases RV glucose oxidation and RV function in experimental RVH. The trigger for metabolic remodeling in the RV and lung differ. In the RV, metabolic remodeling is likely triggered by ischemia (due to microvascular rarefaction and/or reduced coronary perfusion pressure). In the vasculature, metabolic changes result from redox-mediated activation of transcription factors, including hypoxia-inducible factor 1α, as a consequence of epigenetic silencing of SOD2 and/or changes in mitochondrial fission/fusion. Randomized controlled trials are required to assess whether the benefits of enhancing glucose oxidation are realized in patients with PAH.

Updating clinical endpoint definitions

The 6-Minute Walk Distance (6-MWD) has been the most utilized endpoint for judging the efficacy of pulmonary arterial hypertension (PAH) therapy in clinical trials conducted over the past two decades. Despite its simplicity, widespread use in recent trials and overall prognostic value, the 6-MWD has often been criticized over the past several years and pleas from several PAH experts have emerged from the literature to find alternative endpoints that would be more reliable in reflecting the pulmonary vascular resistance as well as cardiac status in PAH and their response to therapy. A meeting of PAH experts and representatives from regulatory agencies and pharmaceutical companies was convened in early 2012 to discuss the validity of current as well as emerging valuable endpoints. The current work represents the proceedings of the conference.

Methods for measuring right ventricular function and hemodynamic coupling with the pulmonary vasculature

The right ventricle (RV) is a pulsatile pump, the efficiency of which depends on proper hemodynamic coupling with the compliant pulmonary circulation. The RV and pulmonary circulation exhibit structural and functional differences with the more extensively investigated left ventricle (LV) and systemic circulation. In light of these differences, metrics of LV function and efficiency of coupling to the systemic circulation cannot be used without modification to characterize RV function and efficiency of coupling to the pulmonary circulation. In this article, we review RV physiology and mechanics, established and novel methods for measuring RV function and hemodynamic coupling, and findings from application of these methods to RV function and coupling changes with pulmonary hypertension. We especially focus on non-invasive measurements, as these may represent the future for clinical monitoring of disease progression and the effect of drug therapies.

Exercise in Pulmonary Hypertension

In healthy subjects, exercise causes a complex cardiovascular and ventilatory response that allows for a 20-fold increase of oxygen consumption as compared to rest. In pulmonary hypertension (PH) this response is very much limited by a restriction of the maximum cardiac output (CO). This restriction is caused by a massively increased afterload of the right ventricle (RV) despite an adaptation that doubles right ventricular contractility as compared to normal controls.1