Advanced hemodynamic and cluster analysis for identifying novel RV function subphenotypes in patients with pulmonary hypertension

BACKGROUND

Quantifying right ventricular (RV) function is important to describe the pathophysiology of in pulmonary hypertension (PH). Current phenotyping strategies in PH rely on few invasive hemodynamic parameters to quantify RV dysfunction severity. The aim of this study was to identify novel RV phenotypes using unsupervised clustering methods on advanced hemodynamic features of RV function.

METHODS

Participants were identified from the University of Arizona Pulmonary Hypertension Registry (n = 190). RV-pulmonary artery coupling (Ees/Ea), RV systolic (Ees), and diastolic function (Eed) were quantified from stored RV pressure waveforms. Consensus clustering analysis with bootstrapping was used to identify the optimal clustering method. Pearson correlation analysis was used to reduce collinearity between variables. RV cluster subphenotypes were characterized using clinical data and compared to pulmonary vascular resistance (PVR) quintiles.

RESULTS

Five distinct RV clusters (C1-C5) with distinct RV subphenotypes were identified using k-medoids with a Pearson distance matrix. Clusters 1 and 2 both have low diastolic stiffness (Eed) and afterload (Ea) but RV-PA coupling (Ees/Ea) is decreased in C2. Intermediate cluster (C3) has a similar Ees/Ea as C2 but with higher PA pressure and afterload. Clusters C4 and C5 have increased Eed and Ea but C5 has a significant decrease in Ees/Ea. Cardiac output was high in C3 distinct from the other clusters. In the PVR quintiles, contractility increased and stroke volume decreased as a function of increased afterload. World Symposium PH classifications were distributed across clusters and PVR quintiles.

CONCLUSIONS

RV-centric phenotyping offers an opportunity for a more precise-medicine-based management approach.

Right Ventricular Contractility and Pulmonary Arterial Coupling After Less Invasive Left Ventricular Assist Device Implantation

Right ventricular failure contributes significantly to morbidity and mortality after left ventricular assist device implantation. Recent data suggest a less invasive strategy (LIS) via thoracotomy may be associated with less right ventricular failure than conventional median sternotomy (CMS). However, the impact of these approaches on load-independent right ventricular (RV) contractility and RV-pulmonary arterial (RV-PA) coupling remains uncertain. We hypothesized that the LIS approach would be associated with preserved RV contractility and improved RV-PA coupling compared with CMS. We performed a retrospective study of patients who underwent durable, centrifugal left ventricular assist device implantation and had paired hemodynamic assessments before and after implantation. RV contractility (end-systolic elastance [Ees]), RV afterload (pulmonary effective arterial elastance [Ea]), and RV-PA coupling (Ees/Ea) were determined using digitized RV pressure waveforms. Forty-two CMS and 21 LIS patients were identified. Preimplant measures of Ees, Ea, and Ees/Ea were similar between groups. After implantation, Ees declined significantly in the CMS group (0.60-0.40, p  = 0.008) but not in the LIS group (0.67-0.58, p  = 0.28). Coupling (Ees/Ea) was unchanged in CMS group (0.54-0.59, p  = 0.80) but improved significantly in the LIS group (0.58-0.71, p  = 0.008). LIS implantation techniques may better preserve RV contractility and improve RV-PA coupling compared with CMS.

iCPET Calculator: A Web-Based Application to Standardize the Calculation of Alpha Distensibility in Patients With Pulmonary Arterial Hypertension

Background Pulmonary vascular distensibility associates with right ventricular function and clinical outcomes in patients with unexplained dyspnea and pulmonary hypertension. Alpha distensibility coefficient is determined from a nonlinear fit to multipoint pressure-flow plots. Study aims were to (1) create and test a user-friendly tool to standardize analysis of exercise hemodynamics including distensibility, and (2) investigate changes in distensibility following treatment in patients with pulmonary arterial hypertension. Methods and Results Participants with an exercise right heart catherization were retrospectively identified from the University of Arizona Pulmonary Hypertension (UA PH) registry and split into a pulmonary arterial hypertension group, a comparator group, and a control group. Right ventricular function was quantified using the coupling ratio and diastolic stiffness. Prototypes of the invasive cardiopulmonary exercise testing (iCPET) calculator were developed using Matlab, Python, and RShiny to analyze exercise hemodynamics and alpha distensibility coefficient, α (%/mm Hg) from multipoint pressure flow plots. Interclass correlation coefficients were calculated for interplatform and interobserver variability in alpha. No significant bias in the intraplatform (Matlab versus RShiny; intraclass correlation coefficient: 0.996) or interobserver (intraclass correlation coefficient: 0.982) comparison of alpha values. Afterload significantly decreased (P<0.05) with no change in alpha distensibility in the pulmonary arterial hypertension group at follow-up. The comparator group had no change in pressure, resistance or alpha distensibility. There were no significant changes in RV diastolic stiffness at follow-up. Conclusions The interactive user interface in the iCPET calculator allows exploration of alpha distensibility using standardized methods. No significant change in alpha distensibility at follow-up suggests that alpha may be less modifiable in patients with long-standing pulmonary arterial hypertension.

Classification and Predictors of Right Ventricular Functional Recovery in Pulmonary Arterial Hypertension

BACKGROUND

Normative changes in right ventricular (RV) structure and function have not been characterized in the context of treatment-associated functional recovery (RV functional recovery [RVFnRec]). The aim of this study is to assess the clinical relevance of a proposed RVFnRec definition.

METHODS

We evaluated 63 incident patients with pulmonary arterial hypertension by right heart catheterization and cardiac magnetic resonance imaging at diagnosis and cardiac magnetic resonance imaging and invasive cardiopulmonary exercise testing following treatment (≈11 months). Sex, age, ethnicity matched healthy control subjects (n=62) with 1-time cardiac magnetic resonance imaging and noninvasive cardiopulmonary exercise testing were recruited from the PVDOMICS (Redefining Pulmonary Hypertension through Pulmonary Vascular Disease Phenomics) project. We examined therapeutic cardiac magnetic resonance imaging changes relative to the evidence-based peak oxygen consumption (VO2peak)>15 mL/(kg·min) to define RVFnRec by receiver operating curve analysis. Afterload was measured as mean pulmonary artery pressure, resistance, compliance, and elastance.

RESULTS

A drop in RV end-diastolic volume of -15 mL best defined RVFnRec (area under the curve, 0.87; P=0.0001) and neared upper 95% CI RV end-diastolic volume of controls. This cutoff was met by 22 out of 63 (35%) patients which was reinforced by freedom from clinical worsening, RVFnRec 1 out of 21 (5%) versus no RVFnRec 17 out of 42, 40% (log-rank P=0.006). A therapy-associated increase of 0.8 mL/mm Hg in compliance had the best predictive value of RVFnRec (area under the curve, 0.76; [95% CI, 0.64-0.88]; P=0.001). RVFnRec patients had greater increases in stroke volume, and cardiac output at exercise.

CONCLUSIONS

RVFnRec defined by RV end-diastolic volume therapeutic decrease of -15 mL predicts exercise capacity, freedom from clinical worsening, and nears normalization. A therapeutic improvement of compliance is superior to other measures of afterload in predicting RVFnRec. RVFnRec is also associated with increased RV output reserve at exercise.

Real-world evidence to advance knowledge in pulmonary hypertension: Status, challenges, and opportunities. A consensus statement from the Pulmonary Vascular Research Institute's Innovative Drug Development Initiative's Real-world Evidence Working Group

This manuscript on real-world evidence (RWE) in pulmonary hypertension (PH) incorporates the broad experience of members of the Pulmonary Vascular Research Institute's Innovative Drug Development Initiative Real-World Evidence Working Group. We aim to strengthen the research community's understanding of RWE in PH to facilitate clinical research advances and ultimately improve patient care. Herein, we review real-world data (RWD) sources, discuss challenges and opportunities when using RWD sources to study PH populations, and identify resources needed to support the generation of meaningful RWE for the global PH community.

Loss of DNA repair mechanisms in cardiac myocytes induce dilated cardiomyopathy

Cardiomyopathy is a progressive disease of the myocardium leading to impaired contractility. Genotoxic cancer therapies are known to be potent drivers of cardiomyopathy, whereas causes of spontaneous disease remain unclear. To test the hypothesis that endogenous genotoxic stress contributes to cardiomyopathy, we deleted the DNA repair gene Ercc1 specifically in striated muscle using a floxed allele of Ercc1 and mice expressing Cre under control of the muscle-specific creatinine kinase (Ckmm) promoter or depleted systemically (Ercc1-/D mice). Ckmm-Cre+/- ;Ercc1-/fl mice expired suddenly of heart disease by 7 months of age. As young adults, the hearts of Ckmm-Cre+/- ;Ercc1-/fl mice were structurally and functionally normal, but by 6-months-of-age, there was significant ventricular dilation, wall thinning, interstitial fibrosis, and systolic dysfunction indicative of dilated cardiomyopathy. Cardiac tissue from the tissue-specific or systemic model showed increased apoptosis and cardiac myocytes from Ckmm-Cre+/- ;Ercc1-/fl mice were hypersensitive to genotoxins, resulting in apoptosis. p53 levels and target gene expression, including several antioxidants, were increased in cardiac tissue from Ckmm-Cre+/- ;Ercc1-/fl and Ercc1-/D mice. Despite this, cardiac tissue from older mutant mice showed evidence of increased oxidative stress. Genetic or pharmacologic inhibition of p53 attenuated apoptosis and improved disease markers. Similarly, overexpression of mitochondrial-targeted catalase improved disease markers. Together, these data support the conclusion that DNA damage produced endogenously can drive cardiac disease and does so mechanistically via chronic activation of p53 and increased oxidative stress, driving cardiac myocyte apoptosis, dilated cardiomyopathy, and sudden death.

Classification and Predictors of Right Ventricular Functional Recovery in Pulmonary Arterial Hypertension

Background

Normative changes in right ventricular (RV) structure and function have not been characterized in the context of treatment-associated functional recovery (RVFnRec). The aim of this study is to assess the clinical relevance of a proposed RVFnRec definition.

Methods

We evaluated 63 incident patients with PAH by right heart catheterization and cardiac MRI (CMR) at diagnosis and CMR and invasive cardiopulmonary exercise (CPET) following treatment (∼11 months). Sex, age, race/ethnicity matched healthy control subjects (n=62) with one-time CMR and non-invasive CPET were recruited from the PVDOMICS project. We examined therapeutic CMR changes relative to the evidence-based peak oxygen consumption (VO2 peak )>15mL/kg/min to define RVFnRec by receiver operating curve analysis. Afterload was measured in the as mean pulmonary artery pressure, resistance, compliance, and elastance.

Results

A drop in RV end-diastolic volume of -15 mL best defined RVFnRec (AUC 0.87, P=0.0001) and neared upper 95% CI RVEDV of controls. 22/63 (35%) of subjects met this cutoff which was reinforced by freedom from clinical worsening, RVFnRec 1/21 (5%) versus no RVFnRec 17/42, 40%, (log rank P=0.006). A therapy-associated increase of 0.8 mL/mmHg in compliance had the best predictive value of RVFnRec (AUC 0.76, CI 0.64-0.88, P=0.001). RVFnRec subjects had greater increases in stroke volume, and cardiac output at exercise.

Conclusions

RVFnRec defined by RVEDV therapeutic decrease of -15mL predicts exercise capacity, freedom from clinical worsening, and nears normalization. A therapeutic improvement of compliance is superior to other measures of afterload in predicting RVFnRec. RVFnRec is also associated with increased RV output reserve at exercise.

Clinical Perspective

What is new?: Right ventricular functional recovery (RVFnRec) represents a novel endpoint of therapeutic success in PAH. We define RVFnRec as treatment associated normative RV changes related to function (peak oxygen consumption). Normative RV imaging changes are compared to a well phenotyped age, sex, and race/ethnicity matched healthy control cohort from the PVDOMICS project. Previous studies have focused on RV ejection fraction improvements. However, we show that changes in RVEDV are perhaps more important in that improvements in LV function also occur. Lastly, RVFnRec is best predicted by improvements in pulmonary artery compliance versus pulmonary vascular resistance, a more often cited metric of RV afterload.What are the clinical implications?: RVFnRec represents a potential non-invasive assessment of clinical improvement and therapeutic response. Clinicians with access to cardiac MRI can obtain a limited scan (i.e., ventricular volumes) before and after treatment. Future study should examine echocardiographic correlates of RVFnRec.

Clinical Characteristics and Transplant-Free Survival Across the Spectrum of Pulmonary Vascular Disease

BACKGROUND

PVDOMICS (Pulmonary Vascular Disease Phenomics) is a precision medicine initiative to characterize pulmonary vascular disease (PVD) using deep phenotyping. PVDOMICS tests the hypothesis that integration of clinical metrics with omic measures will enhance understanding of PVD and facilitate an updated PVD classification.

OBJECTIVES

The purpose of this study was to describe clinical characteristics and transplant-free survival in the PVDOMICS cohort.

METHODS

Subjects with World Symposium Pulmonary Hypertension (WSPH) group 1-5 PH, disease comparators with similar underlying diseases and mild or no PH and healthy control subjects enrolled in a cross-sectional study. PH groups, comparators were compared using standard statistical tests including log-rank tests for comparing time to transplant or death.

RESULTS

A total of 1,193 subjects were included. Multiple WSPH groups were identified in 38.9% of PH subjects. Nocturnal desaturation was more frequently observed in groups 1, 3, and 4 PH vs comparators. A total of 50.2% of group 1 PH subjects had ground glass opacities on chest computed tomography. Diffusing capacity for carbon monoxide was significantly lower in groups 1-3 PH than their respective comparators. Right atrial volume index was higher in WSPH groups 1-4 than comparators. A total of 110 participants had a mean pulmonary artery pressure of 21-24 mm Hg. Transplant-free survival was poorest in group 3 PH.

CONCLUSIONS

PVDOMICS enrolled subjects across the spectrum of PVD, including mild and mixed etiology PH. Novel findings include low diffusing capacity for carbon monoxide and enlarged right atrial volume index as shared features of groups 1-3 and 1-4 PH, respectively; unexpected, frequent presence of ground glass opacities on computed tomography; and sleep alterations in group 1 PH, and poorest survival in group 3 PH. PVDOMICS will facilitate a new understanding of PVD and refine the current PVD classification. (Pulmonary Vascular Disease Phenomics Program PVDOMICS [PVDOMICS]; NCT02980887).

Increased RV:LV ratio on chest CT-angiogram in COVID-19 is a marker of adverse outcomes

BACKGROUND

Right ventricular (RV) dilation has been used to predict adverse outcomes in acute pulmonary conditions. It has been used to categorize the severity of novel coronavirus infection (COVID-19) infection. Our study aimed to use chest CT-angiogram (CTA) to assess if increased RV dilation, quantified as an increased RV:LV (left ventricle) ratio, is associated with adverse outcomes in the COVID-19 infection, and if it occurs out of proportion to lung parenchymal disease.

RESULTS

We reviewed clinical, laboratory, and chest CTA findings in COVID-19 patients (n = 100), and two control groups: normal subjects (n = 10) and subjects with organizing pneumonia (n = 10). On a chest CTA, we measured basal dimensions of the RV and LV in a focused 4-chamber view, and dimensions of pulmonary artery (PA) and aorta (AO) at the PA bifurcation level. Among the COVID-19 cohort, a higher RV:LV ratio was correlated with adverse outcomes, defined as ICU admission, intubation, or death. In patients with adverse outcomes, the RV:LV ratio was 1.06 ± 0.10, versus 0.95 ± 0.15 in patients without adverse outcomes. Among the adverse outcomes group, compared to the control subjects with organizing pneumonia, the lung parenchymal damage was lower (22.6 ± 9.0 vs. 32.7 ± 6.6), yet the RV:LV ratio was higher (1.06 ± 0.14 vs. 0.89 ± 0.07). In ROC analysis, RV:LV ratio had an AUC = 0.707 with an optimal cutoff of RV:LV ≥ 1.1 as a predictor of adverse outcomes. In a validation cohort (n = 25), an RV:LV ≥ 1.1 as a cutoff predicted adverse outcomes with an odds ratio of 76:1.

CONCLUSIONS

In COVID-19 patients, RV:LV ratio ≥ 1.1 on CTA chest is correlated with adverse outcomes. RV dilation in COVID-19 is out of proportion to parenchymal lung damage, pointing toward a vascular and/or thrombotic injury in the lungs.

Mineralocorticoid receptor antagonist treatment of established pulmonary arterial hypertension improves interventricular dependence in the SU5416-hypoxia rat model

Treatment with mineralocorticoid receptor (MR) antagonists beginning at the outset of disease, or early thereafter, prevents pulmonary vascular remodeling in preclinical models of pulmonary arterial hypertension (PAH). However, the efficacy of MR blockade in established disease, a more clinically relevant condition, remains unknown. Therefore, we investigated the effectiveness of two MR antagonists, eplerenone (EPL) and spironolactone (SPL), after the development of severe right ventricular (RV) dysfunction in the rat SU5416-hypoxia (SuHx) PAH model. Cardiac magnetic resonance imaging (MRI) in SuHx rats at the end of week 5, before study treatment, confirmed features of established disease including reduced RV ejection fraction and RV hypertrophy, pronounced septal flattening with impaired left ventricular filling and reduced cardiac index. Five weeks of treatment with either EPL or SPL improved left ventricular filling and prevented the further decline in cardiac index compared with placebo. Interventricular septal displacement was reduced by EPL whereas SPL effects were similar, but not significant. Although MR antagonists did not significantly reduce pulmonary artery pressure or vessel remodeling in SuHx rats with established disease, animals with higher drug levels had lower pulmonary pressures. Consistent with effects on cardiac function, EPL treatment tended to suppress MR and proinflammatory gene induction in the RV. In conclusion, MR antagonist treatment led to modest, but consistent beneficial effects on interventricular dependence after the onset of significant RV dysfunction in the SuHx PAH model. These results suggest that measures of RV structure and/or function may be useful endpoints in clinical trials of MR antagonists in patients with PAH.

The Right Ventricular-Pulmonary Arterial Coupling and Diastolic Function Response to Therapy in Pulmonary Arterial Hypertension

BACKGROUND

Multiparametric risk assessment is used in pulmonary arterial hypertension (PAH) to target therapy. However, this strategy is imperfect as most patients remain in intermediate or high risk after initial treatment with low risk being the goal. Metrics of right ventricular (RV) adaptation are promising tools that may help refine our therapeutic strategy.

RESEARCH QUESTION

Does RV adaptation predict therapeutic response over time?

STUDY DESIGN AND METHODS

We evaluated 52 incident treatment naïve patients with advanced PAH by catheterization and cardiac imaging longitudinally at baseline, follow-up 1 (∼3 mo.) and follow-up 2 (∼18 mo.). All patients were placed on goal-directed therapy with parenteral treprostinil and/or combination therapy with treatment escalation if functional class I-II was not achieved. Therapeutic response was evaluated at follow-up 1 as non-responders (died) or responders and again at follow-up 2 as super-responders (low risk) or partial-responders (high/intermediate risk). Multiparametric risk was based on a simplified ERS/ESC guideline score. RV adaptation was evaluated with the single-beat coupling ratio (Ees/Ea) and diastolic function with diastolic elastance (Eed). Data are expressed as mean±SD or odds ratio [95%CI].

RESULTS

Nine patients (17%) were non-responders. PAH-directed therapy improved ERS low risk from 1 (2%) at baseline to 23 (55%) at follow-up 2. Ees/Ea at presentation was non-significantly higher in responders (0.9±0.4) versus non-responders (0.6±0.4, p=0.09) but was unable to predict super-responder status at follow-up 2 (odds ratio 1.40 [0.28-7.0], p=0.84). Baseline RVEF and change in Eed successfully predicted super-responder status at follow-up 2 (odds ratio 1.15 [1.0-1.27], p=0.009 and 0.29 [0.86-0.96], p=0.04, respectively).

INTERPRETATION

In patients with advanced PAH, RV-PA coupling could not discriminate irreversible RV failure (non-responders) at presentation but showed a late trend to improvement by follow-up 2. Early change in Eed and baseline RVEF were the best predictors of therapeutic response.

Relaxin Inhibits Ventricular Arrhythmia and Asystole in Rats With Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) leads to right ventricular cardiomyopathy and cardiac dysfunctions where in the clinical setting, cardiac arrest is the likely cause of death, in ~70% of PAH patients. We investigated the cardiac phenotype of PAH hearts and tested the hypothesis that the insulin-like hormone, Relaxin could prevent maladaptive cardiac remodeling and protect against cardiac dysfunctions in a PAH animal model. PAH was induced in rats with sugen (20 mg/kg), hypoxia then normoxia (3-weeks/each); relaxin (RLX = 0, 30 or 400 μg/kg/day, n ≥ 6/group) was delivered subcutaneously (6-weeks) with implanted osmotic mini-pumps. Right ventricle (RV) hemodynamics and Doppler-flow measurements were followed by cardiac isolation, optical mapping, and arrhythmia phenotype. Sugen-hypoxia (SuHx) treated rats developed PAH characterized by higher RV systolic pressures (50 ± 19 vs. 22 ± 5 mmHg), hypertrophy, reduced stroke volume, ventricular fibrillation (VF) (n = 6/11) and bradycardia/arrest (n = 5/11); both cardiac phenotypes were suppressed with dithiothreitol (DTT = 1 mM) (n = 0/2/group) or RLX (low or high dose, n = 0/6/group). PAH hearts developed increased fibrosis that was reversed by RLX-HD, but not RLX-LD. Relaxin decreased Nrf2 and glutathione transferases but not glutathione-reductase. High-dose RLX improved pulmonary arterial compliance (measured by Doppler flow), suppressed VF even after burst-pacing, n = 2/6). Relaxin suppressed VF and asystole through electrical remodeling and by reversing thiol oxidative stress. For the first time, we showed two cardiac phenotypes in PAH animals and their prevention by RLX. Relaxin may modulate maladaptive cardiac remodeling in PAH and protect against arrhythmia and cardiac arrest.

Recent advancements in pulmonary arterial hypertension and right heart failure research: overview of selected abstracts from ATS2020 and emerging COVID-19 research

Each year the American Thoracic Society (ATS) Conference brings together scientists who conduct basic, translational and clinical research to present on the recent advances in the field of respirology. Due to the Coronavirus Disease of 2019 (COVID-19) pandemic, the ATS2020 Conference was held online in a series of virtual meetings. In this review, we focus on the breakthroughs in pulmonary hypertension research. We have selected 11 of the best basic science abstracts which were presented at the ATS2020 Assembly on Pulmonary Circulation mini-symposium "What's New in Pulmonary Arterial Hypertension (PAH) and Right Ventricular (RV) Signaling: Lessons from the Best Abstracts," reflecting the current state of the art and associated challenges in PH. Particular emphasis is placed on understanding the mechanisms underlying RV failure, the regulation of inflammation, and the novel therapeutic targets that emerged from preclinical research. The pathologic interactions between pulmonary hypertension, right ventricular function and COVID-19 are also discussed.

NHLBI-CMREF Workshop Report on Pulmonary Vascular Disease Classification: JACC State-of-the-Art Review

The National Heart, Lung, and Blood Institute and the Cardiovascular Medical Research and Education Fund held a workshop on the application of pulmonary vascular disease omics data to the understanding, prevention, and treatment of pulmonary vascular disease. Experts in pulmonary vascular disease, omics, and data analytics met to identify knowledge gaps and formulate ideas for future research priorities in pulmonary vascular disease in line with National Heart, Lung, and Blood Institute Strategic Vision goals. The group identified opportunities to develop analytic approaches to multiomic datasets, to identify molecular pathways in pulmonary vascular disease pathobiology, and to link novel phenotypes to meaningful clinical outcomes. The committee suggested support for interdisciplinary research teams to develop and validate analytic methods, a national effort to coordinate biosamples and data, a consortium of preclinical investigators to expedite target evaluation and drug development, longitudinal assessment of molecular biomarkers in clinical trials, and a task force to develop a master clinical trials protocol for pulmonary vascular disease.

Right ventricular load and contractility in HIV-associated pulmonary hypertension

Background

People living with human immunodeficiency virus (PLWH) are at risk of developing pulmonary hypertension (PH) and right ventricular (RV) dysfunction, but understanding of the relationship of RV function to afterload (RV-PA coupling) is limited. We evaluated the clinical and hemodynamic characteristics of human immunodeficiency virus (HIV)-associated PH.

Methods

We performed a retrospective review of patients with a diagnosis of HIV undergoing right heart catheterization (RHC) from 2000–2016 in a tertiary care center. Inclusion criteria were diagnosis of HIV, age ≥ 18 years and availability of RHC data. PH was classified as either pulmonary arterial hypertension (PAH; mean pulmonary arterial pressure [mPAP] ≥ 25mmHg with pulmonary artery wedge pressure [PAWP] ≤ 15mmHg) or pulmonary venous hypertension (PVH; mPAP ≥ 25mmHg with PAWP > 15). We collected demographics, CD4 cell count, HIV viral load, RHC and echocardiographic data. The single beat method was used to calculate RV-PA coupling from RHC.

Results

Sixty-two PLWH with a clinical likelihood for PH underwent RHC. Thirty-two (52%) met PH criteria (15 with PAH, 17 with PVH). Average time from diagnosis of HIV to diagnosis of PH was 11 years. Eleven of 15 individuals with PAH were on antiretroviral therapy (ART) while all 17 patients with PVH were on ART. Compared to PLWH without PH, those with PH had an increased likelihood of having a detectable HIV viral load and lower CD4 cell counts. PLWH with PAH or PVH had increased RV afterload with normal RV contractility, and preserved RV-PA coupling.

Conclusion

PLWH with PH (PAH or PVH) were more likely to have a detectable HIV viral load and lower CD4 count at the time of RHC. PLWH with PAH or PVH had increased RV afterload, normal RV contractility, with preserved RV-PA coupling suggestive of an early onset, mild, and compensated form of PH. These results should be confirmed in larger studies.

Transcriptomic profiles in pulmonary arterial hypertension associate with disease severity and identify novel candidate genes

Using RNAseq, we identified a 61 gene-based circulating transcriptomic profile most correlated with four indices of pulmonary arterial hypertension severity. In an independent dataset, 13/61 (21%) genes were differentially expressed in lung tissues of pulmonary arterial hypertension cases versus controls, highlighting potentially novel candidate genes involved in pulmonary arterial hypertension development.

Treatment With Treprostinil and Metformin Normalizes Hyperglycemia and Improves Cardiac Function in Pulmonary Hypertension Associated With Heart Failure With Preserved Ejection Fraction

OBJECTIVE

Pulmonary hypertension (PH) due to left heart disease (group 2), especially in the setting of heart failure with preserved ejection fraction (HFpEF), is the most common cause of PH worldwide; however, at present, there is no proven effective therapy available for its treatment. PH-HFpEF is associated with insulin resistance and features of metabolic syndrome. The stable prostacyclin analog, treprostinil, is an effective and widely used Food and Drug Administration-approved drug for the treatment of pulmonary arterial hypertension. While the effect of treprostinil on metabolic syndrome is unknown, a recent study suggests that the prostacyclin analog beraprost can improve glucose intolerance and insulin sensitivity. We sought to evaluate the effectiveness of treprostinil in the treatment of metabolic syndrome-associated PH-HFpEF. Approach and Results: Treprostinil treatment was given to mice with mild metabolic syndrome-associated PH-HFpEF induced by high-fat diet and to SU5416/obese ZSF1 rats, a model created by the treatment of rats with a more profound metabolic syndrome due to double leptin receptor defect (obese ZSF1) with a vascular endothelial growth factor receptor blocker SU5416. In high-fat diet-exposed mice, chronic treatment with treprostinil reduced hyperglycemia and pulmonary hypertension. In SU5416/Obese ZSF1 rats, treprostinil improved hyperglycemia with similar efficacy to that of metformin (a first-line drug for type 2 diabetes mellitus); the glucose-lowering effect of treprostinil was further potentiated by the combined treatment with metformin. Early treatment with treprostinil in SU5416/Obese ZSF1 rats lowered pulmonary pressures, and a late treatment with treprostinil together with metformin improved pulmonary artery acceleration time to ejection time ratio and tricuspid annular plane systolic excursion with AMPK (AMP-activated protein kinase) activation in skeletal muscle and the right ventricle.

CONCLUSIONS

Our data suggest a potential use of treprostinil as an early treatment for mild metabolic syndrome-associated PH-HFpEF and that combined treatment with treprostinil and metformin may improve hyperglycemia and cardiac function in a more severe disease.

Tetramethylpyrazine: A promising drug for the treatment of pulmonary hypertension

BACKGROUND AND PURPOSE

Tetramethylpyrazine (TMP) was originally isolated from the traditional Chinese herb ligusticum and the fermented Japanese food natto and has since been synthesized. TMP has a long history of beneficial effects in the treatment of many cardiovascular diseases. Here we have evaluated the therapeutic effects of TMP on pulmonary hypertension (PH) in animal models and in patients with pulmonary arterial hypertension (PAH) or chronic thromboembolic pulmonary hypertension (CTEPH).

EXPERIMENTAL APPROACH

Three well-defined models of PH -chronic hypoxia (10% O₂ )-induced PH (HPH), monocrotaline-induced PH (MCT-PH) and Sugen 5416/hypoxia-induced PH (SuHx-PH) - were used in Sprague-Dawley rats, and assessed by echocardiography, along with haemodynamic and histological techniques. Primary cultures of rat distal pulmonary arterial smooth muscle cells (PASMCs) were used to study intracellular calcium levels. Western blots and RT-qPCR assays were also used. In the clinical cohort, patients with PAH or CTEPH were recruited. The effects of TMP were evaluated in all systems.

KEY RESULTS

TMP (100 mg·kg^-1 ·day^-1 ) prevented rats from developing experimental PH and ameliorated three models of established PH: HPH, MCT-PH and SuHx-PH. The therapeutic effects of TMP were accompanied by inhibition of intracellular calcium homeostasis in PASMCs. In a small cohort of patients with PAH or CTEPH, oral administration of TMP (100 mg, t.i.d. for 16 weeks) increased the 6-min walk distance and improved the 1-min heart rate recovery.

CONCLUSION AND IMPLICATIONS

Our results suggest that TMP is a novel and inexpensive medication for treatment of PH. Clinical trial is registered with www.chictr.org.cn (ChiCTR-IPR-14005379).

Comprehensive Diagnostic Evaluation of Cardiovascular Physiology in Patients With Pulmonary Vascular Disease: Insights From the PVDOMICS Program

BACKGROUND

Invasive hemodynamic evaluation through right heart catheterization plays an essential role in the diagnosis, categorization, and risk stratification of patients with pulmonary hypertension.

METHODS

Subjects enrolled in the PVDOMICS (Redefining Pulmonary Hypertension through Pulmonary Vascular Disease Phenomics) program undergo an extensive invasive hemodynamic evaluation that includes repeated measurements at rest and during several provocative physiological challenges. It is a National Institutes of Health/National Heart, Lung, and Blood Institute initiative to reclassify pulmonary hypertension groups based on clustered phenotypic and phenomic characteristics. At a subset of centers, participants also undergo an invasive cardiopulmonary exercise test to assess changes in hemodynamics and gas exchange during exercise.

CONCLUSIONS

When coupled with other physiological testing and blood -omic analyses involved in the PVDOMICS study, the comprehensive right heart catheterization protocol described here holds promise to clarify the diagnosis and clustering of pulmonary hypertension patients into cohorts beyond the traditional 5 World Symposium on Pulmonary Hypertension groups. This article will describe the methods applied for invasive hemodynamic characterization in the PVDOMICS program. Registration: URL: https://www.clinicaltrials.gov. Unique identifier: NCT02980887.

MicroRNA-mediated downregulation of K+ channels in pulmonary arterial hypertension

Downregulated expression of K+ channels and decreased K+ currents in pulmonary artery smooth muscle cells (PASMC) have been implicated in the development of sustained pulmonary vasoconstriction and vascular remodeling in patients with idiopathic pulmonary arterial hypertension (IPAH). However, it is unclear exactly how K+ channels are downregulated in IPAH-PASMC. MicroRNAs (miRNAs) are small non-coding RNAs that are capable of posttranscriptionally regulating gene expression by binding to the 3'-untranslated regions of their targeted mRNAs. Here, we report that specific miRNAs are responsible for the decreased K+ channel expression and function in IPAH-PASMC. We identified 3 miRNAs (miR-29b, miR-138, and miR-222) that were highly expressed in IPAH-PASMC in comparison to normal PASMC (>2.5-fold difference). Selectively upregulated miRNAs are correlated with the decreased expression and attenuated activity of K+ channels. Overexpression of miR-29b, miR-138, or miR-222 in normal PASMC significantly decreased whole cell K+ currents and downregulated voltage-gated K+ channel 1.5 (KV1.5/KCNA5) in normal PASMC. Inhibition of miR-29b in IPAH-PASMC completely recovered K+ channel function and KV1.5 expression, while miR-138 and miR-222 had a partial or no effect. Luciferase assays further revealed that KV1.5 is a direct target of miR-29b. Additionally, overexpression of miR-29b in normal PASMC decreased large-conductance Ca2+-activated K+ (BKCa) channel currents and downregulated BKCa channel β1 subunit (BKCaβ1 or KCNMB1) expression, while inhibition of miR-29b in IPAH-PASMC increased BKCa channel activity and BKCaβ1 levels. These data indicate upregulated miR-29b contributes at least partially to the attenuated function and expression of KV and BKCa channels in PASMC from patients with IPAH.

Association Between Hemodynamic Markers of Pulmonary Hypertension and Outcomes in Heart Failure With Preserved Ejection Fraction

Importance

Heart failure with preserved ejection fraction (HFpEF) is highly prevalent, yet there are no specific therapies, possibly due to phenotypic heterogeneity. The development of pulmonary hypertension (PH) in patients with HFpEF is considered a high-risk phenotype in need of targeted therapies, but there have been limited hemodynamic and outcomes data.

Objective

To identify the hemodynamic characteristics and outcomes of PH-HFpEF.

Design, Setting, and Participants

Cohort study of participants who had a right heart catheterization from January 2005 to September 2012 (median [interquartile range] follow-up time, 1578 [554-2513] days) were analyzed. Hemodynamic catheterization data was linked to the clinical data repository of all inpatient and outpatient encounters across a health system. Single tertiary referral center for heart failure and PH within a large health care network using a common clinical data repository was studied. There were 19 262 procedures in 10 023 participants.

Exposures

Participants were classified as having no PH, precapillary PH, or PH in the setting of left heart disease (reduced or preserved ejection fraction). Pulmonary hypertension associated with HFpEF was defined as mean pulmonary artery pressure of 25 mm Hg or more, pulmonary artery wedge pressure of 15 mm Hg or more, and left ventricular ejection fraction of 45% or more. Pulmonary hypertension severity was quantified by the hemodynamic parameters transpulmonary gradient, pulmonary vascular resistance, and diastolic pulmonary gradient.

Main Outcomes and Measures

The primary outcome was time to all-cause mortality. Secondary outcomes were time to acute hospitalization and cardiovascular hospitalization.

Results

The mean (SD) of all study individuals was 65 (38) years. Of 10 023 individuals, 2587 (25.8%) had PH-HFpEF. Mortality was 23.6% at 1 year and 48.2% at 5 years. Cardiac hospitalizations occurred in 28.1% at 1 year and 47.4% at 5 years. The frequency of precapillary PH using clinically defined cut-offs for transpulmonary gradient (>12 mm Hg), pulmonary vascular resistance (3 Woods units), and diastolic pulmonary gradient (≥7 mm Hg) were 12.6%, 8.8%, and 3.5%, respectively. Transpulmonary gradient, pulmonary vascular resistance, and diastolic pressure gradient were predictive of mortality and cardiac hospitalizations.

Conclusions and Relevance

In a large cohort referred for invasive hemodynamic assessment, PH-HFpEF was common. Transpulmonary gradient, pulmonary vascular resistance, and diastolic pulmonary gradient are all associated with mortality and cardiac hospitalizations.

Dynamic right ventricular-pulmonary arterial uncoupling during maximum incremental exercise in exercise pulmonary hypertension and pulmonary arterial hypertension

Despite recent advances, the prognosis of pulmonary hypertension (PH) remains poor. While the initial insult in PH implicates the pulmonary vasculature, the functional state, exercise capacity, and survival of such patients are closely linked to right ventricular (RV) function. In the current study, we sought to investigate the effects of maximum incremental exercise on the matching of RV contractility and afterload (i.e. right ventricular-pulmonary arterial [RV-PA] coupling) in patients with exercise PH (ePH) and pulmonary arterial hypertension (PAH). End-systolic elastance (Ees), pulmonary arterial elastance (Ea), and RV-PA coupling (Ees/Ea) were determined using single-beat pressure-volume loop analysis in 40 patients that underwent maximum invasive cardiopulmonary exercise testing. Eleven patients had ePH, nine had PAH, and 20 were age-matched controls. During exercise, the impaired exertional contractile reserve in PAH was associated with blunted stroke volume index (SVI) augmentation and reduced peak oxygen consumption (peak VO₂ %predicted). Compared to PAH, ePH demonstrated increased RV contractility in response to increasing RV afterload during exercise; however, this was insufficient and resulted in reduced peak RV-PA coupling. The dynamic RV-PA uncoupling in ePH was associated with similarly blunted SVI augmentation and peak VO₂ as PAH. In conclusion, dynamic rest-to-peak exercise RV-PA uncoupling during maximum exercise blunts SV increase and reduces exercise capacity in exercise PH and PAH. In ePH, the insufficient increase in RV contractility to compensate for increasing RV afterload during maximum exercise leads to deterioration of RV-PA coupling. These data provide evidence that even in the early stages of PH, RV function is compromised.

Nitric Oxide-Independent Soluble Guanylate Cyclase Activation Improves Vascular Function and Cardiac Remodeling in Sickle Cell Disease

Sickle cell disease (SCD) is associated with intravascular hemolysis and oxidative inhibition of nitric oxide (NO) signaling. BAY 54-6544 is a small-molecule activator of oxidized soluble guanylate cyclase (sGC), which, unlike endogenous NO and the sGC stimulator, BAY 41-8543, preferentially binds and activates heme-free, NO-insensitive sGC to restore enzymatic cGMP production. We tested orally delivered sGC activator, BAY 54-6544 (17 mg/kg/d), sGC stimulator, BAY 41-8543, sildenafil, and placebo for 4-12 weeks in the Berkeley transgenic mouse model of SCD (BERK-SCD) and their hemizygous (Hemi) littermate controls (BERK-Hemi). Right ventricular (RV) maximum systolic pressure (RVmaxSP) was measured using micro right-heart catheterization. RV hypertrophy (RVH) was determined using Fulton's index and RV corrected weight (ratio of RV to tibia). Pulmonary artery vasoreactivity was tested for endothelium-dependent and -independent vessel relaxation. Right-heart catheterization revealed higher RVmaxSP and RVH in BERK-SCD versus BERK-Hemi, which worsened with age. Treatment with the sGC activator more effectively lowered RVmaxSP and RVH, with 90-day treatment delivering superior results, when compared with other treatments and placebo groups. In myography experiments, acetylcholine-induced (endothelium-dependent) and sodium-nitroprusside-induced (endothelium-independent NO donor) relaxation of the pulmonary artery harvested from placebo-treated BERK-SCD was impaired relative to BERK-Hemi but improved after therapy with sGC activator. By contrast, no significant effect for sGC stimulator or sildenafil was observed in BERK-SCD. These findings suggest that sGC is oxidized in the pulmonary arteries of transgenic SCD mice, leading to blunted responses to NO, and that the sGC activator, BAY 54-6544, may represent a novel therapy for SCD-associated pulmonary arterial hypertension and cardiac remodeling.

EXPRESS: Surfing the Right Ventricular Pressure Waveform: Methods to assess Global, Systolic and Diastolic RV Function from a Clinical Right Heart Catheterization

Right ventricular (RV) function strongly associates with mortality in patients with pulmonary arterial hypertension (PAH). Current methods to determine RV function require temporal measurements of pressure and volume. The aim of the study was to investigate the feasibility of using right heart catheterization (RHC) measurements to estimate systolic and diastolic RV function. RV pressure and volume points were fit to P = α(eβV-1) to assess diastolic stiffness coefficient (β) and end-diastolic elastance (Eed). Single-beat methods were used to assess RV contractility (Ees). The effects of a non-zero unstressed RV volume (V0), RHC-derived stroke volume (SVRHC), and normalization of the end-diastolic volume (EDV) on estimates of β, Eed, and Ees were tested using Bland–Altman analysis in an incident PAH cohort (n = 32) that had both a RHC and cardiac magnetic resonance (CMR) test. RHC-derived measures of RV function were used to detect the effect of prostacyclin therapy in an incident PAH cohort and the severity of PAH in prevalent PAH (n = 21). A non-zero V0 had a minimal effect on β with a small bias and limits of agreement (LOA). Stroke volume (SV) significantly influenced estimates of β and Ees with a large LOA. Normalization of EDV had minimal effect on both β and Eed. RHC-derived β and Eed increased due to the severity of PAH and decreased due to three months of prostacyclin therapy. It is feasible to detect therapeutic changes in specific stiffness and elastic properties of the RV from signal-beat pressure-volume loops by using RHC-derived SV and normalizing RV EDV.

Longitudinal Evaluation of Pulmonary Arterial Hypertension in a Rhesus Macaque (Macaca mulatta) Model of HIV Infection

Pulmonary arterial hypertension (PAH) is a life-threatening disease with higher incidence in HIV-infected compared with noninfected patients. SIV-infected NHP develop clinical manifestations of HIV infection, including PAH. To understand the pathogenesis of PAH and determine the relationship between hemodynamic changes and clinical characteristics associated with SIV infection, we performed right heart catheterization and echocardiographic imaging of 21 rhesus macaques before and after SIV infection. Between 6 and 12 mo after infection, 11 of the 21 animals had elevated mean pulmonary arterial pressure (mPAP; greater than 25 mm Hg). RV involvement was evident as increased RV glucose uptake in PAH+ macaques on positron emission tomography-coupled CT compared with uninfected animals. RV and pulmonary vascular collagen deposition were elevated in PAH+ animals. At 12 mo after infection, 6 of the 21 macaques (28.6%) exhibited continued increase in mPAP (progressive PAH), whereas 5 animals (23.8%) had reduced pressure (transient PAH). SIV infection of rhesus macaques led to 3 distinct outcomes with regard to hemodynamic function. Hemodynamic alterations correlated with specific inflammatory profiles and increased RV and pulmonary arterial fibrosis but not with viral load, sex, or CD4+ T-cell levels. This model of a natural cause of PAH provides insight into disease pathways that are important for the development of novel therapeutic targets.

Right ventricular afterload predicts long-term transition from parenteral to oral treprostinil in pulmonary arterial hypertension

Despite the increasing trends, reports on long-term follow-up are limited on transitioning from parenteral to oral treprostinil therapy in patients with pulmonary arterial hypertension (PAH). We investigated both the effectiveness of parenteral to oral treprostinil transition and the characteristics associated with transition failure over a duration of two years. The study included 37 Group I functional class I and II patients with PAH on combination therapy. Patients were excluded if cardiac index ≤2.2 L/min/m², right atrial pressure ≥11 mmHg, or 6-min walk distance ≤250 m. Patients were categorized as successful (_STransition) or unsuccessful (_UTransition) transition based on clinical stability, or a parenteral comparator (_CParenteral) if they remained on parenteral therapy (no transition). All patients underwent two right heart catheterizations, one at enrollment and a second post transition. Of 24 total transition patients, 46% were classified as _UTransition. _UTransition occurred on average 577 days post transition. Both _UTransition and _STransition had similar hemodynamics at diagnosis and treprostinil dose before and after transition. Before transition, the pulmonary vascular resistance (PVR) was significantly higher in the _UTransition (6.7 ± 2 WU) vs. _STransition group (3.5 ± 1.5 WU). At follow-up catheterization, the _UTransition group demonstrated further increases in PVR, greater than the _CParenteral group, without recovery despite “rescue” therapy in the _UTransition group. A pre-transition PVR of 4.16 WU discriminated the _UTransition from the _STransition group. While a subset of PAH patients on combination therapy may be safely transitioned from parenteral to oral treprostinil, caution should be exercised in patients with elevated baseline PVR to avoid irreversible destabilization.

Diabetes Mellitus Associates with Increased Right Ventricular Afterload and Remodeling in Pulmonary Arterial Hypertension

BACKGROUND

Diabetes mellitus is associated with left ventricular hypertrophy and dysfunction. Parallel studies have also reported associations between diabetes mellitus and right ventricular dysfunction and reduced survival in patients with pulmonary arterial hypertension. However, the impact of diabetes mellitus on the pulmonary vasculature has not been well characterized. We hypothesized that diabetes mellitus and hyperglycemia could specifically influence right ventricular afterload and remodeling in patients with Group I pulmonary arterial hypertension, providing a link to their known susceptibility to right ventricular dysfunction.

METHODS

Using an adjusted model for age, sex, pulmonary vascular resistance, and medication use, associations of fasting blood glucose, glycated hemoglobin, and the presence of diabetes mellitus were evaluated with markers of disease severity in 162 patients with pulmonary arterial hypertension.

RESULTS

A surrogate measure of increased pulmonary artery stiffness, elevated pulmonary arterial elastance (P = .012), along with reduced log(pulmonary artery capacitance) (P = .006) were significantly associated with the presence of diabetes mellitus in patients with pulmonary arterial hypertension in a fully adjusted model. Similar associations between pulmonary arterial elastance and capacitance were noted with both fasting blood glucose and glycated hemoglobin. Furthermore, right ventricular wall thickness on echocardiography was greater in pulmonary arterial hypertension patients with diabetes, supporting the link between right ventricular remodeling and diabetes.

CONCLUSION

Cumulatively, these data demonstrate that an increase in right ventricular afterload, beyond pulmonary vascular resistance alone, may influence right ventricular remodeling and provide a mechanistic link between the susceptibility to right ventricular dysfunction in patients with both diabetes mellitus and pulmonary arterial hypertension.

Biomechanical and Hemodynamic Measures of Right Ventricular Diastolic Function: Translating Tissue Biomechanics to Clinical Relevance

Background

Right ventricular (RV) diastolic function has been associated with outcomes for patients with pulmonary hypertension; however, the relationship between biomechanics and hemodynamics in the right ventricle has not been studied.

Methods and Results

Rat models of RV pressure overload were obtained via pulmonary artery banding (PAB; control, n=7; PAB, n=5). At 3 weeks after banding, RV hemodynamics were measured using a conductance catheter. Biaxial mechanical properties of the RV free wall myocardium were obtained to extrapolate longitudinal and circumferential elastic modulus in low and high strain regions (E₁ and E₂, respectively). Hemodynamic analysis revealed significantly increased end‐diastolic elastance (E_ed) in PAB (control: 55.1 mm Hg/mL [interquartile range: 44.7–85.4 mm Hg/mL]; PAB: 146.6 mm Hg/mL [interquartile range: 105.8–155.0 mm Hg/mL]; P=0.010). Longitudinal E₁ was increased in PAB (control: 7.2 kPa [interquartile range: 6.7–18.1 kPa]; PAB: 34.2 kPa [interquartile range: 18.1–44.6 kPa]; P=0.018), whereas there were no significant changes in longitudinal E₂ or circumferential E₁ and E₂. Last, wall stress was calculated from hemodynamic data by modeling the right ventricle as a sphere: stress=Pressure×radius2×thickness.

Conclusions

RV pressure overload in PAB rats resulted in an increase in diastolic myocardial stiffness reflected both hemodynamically, by an increase in E_ed, and biomechanically, by an increase in longitudinal E₁. Modest increases in tissue biomechanical stiffness are associated with large increases in E_ed. Hemodynamic measurements of RV diastolic function can be used to predict biomechanical changes in the myocardium.

Mouse Genome-Wide Association Study of Preclinical Group II Pulmonary Hypertension Identifies Epidermal Growth Factor Receptor

Pulmonary hypertension (PH) is associated with features of obesity and metabolic syndrome that translate to the induction of PH by chronic high-fat diet (HFD) in some inbred mouse strains. We conducted a genome-wide association study (GWAS) to identify candidate genes associated with susceptibility to HFD-induced PH. Mice from 36 inbred and wild-derived strains were fed with regular diet or HFD for 20 weeks beginning at 6-12 weeks of age, after which right ventricular (RV) and left ventricular (LV) end-systolic pressure (ESP) and maximum pressure (MaxP) were measured by cardiac catheterization. We tested for association of RV MaxP and RV ESP and identified genomic regions enriched with nominal associations to both of these phenotypes. We excluded genomic regions if they were also associated with LV MaxP, LV ESP, or body weight. Genes within significant regions were scored based on the shortest-path betweenness centrality, a measure of network connectivity, of their human orthologs in a gene interaction network of human PH-related genes. WSB/EiJ, NON/ShiLtJ, and AKR/J mice had the largest increases in RV MaxP after high-fat feeding. Network-based scoring of GWAS candidates identified epidermal growth factor receptor (Egfr) as having the highest shortest-path betweenness centrality of GWAS candidates. Expression studies of lung homogenate showed that EGFR expression is increased in the AKR/J strain, which developed a significant increase in RV MaxP after high-fat feeding as compared with C57BL/6J, which did not. Our combined GWAS and network-based approach adds evidence for a role for Egfr in murine PH.

Development of a Mouse Model of Metabolic Syndrome, Pulmonary Hypertension, and Heart Failure with Preserved Ejection Fraction

Pulmonary hypertension (PH) associated with heart failure with preserved ejection fraction (PH-HFpEF; World Health Organization Group II) secondary to left ventricular (LV) diastolic dysfunction is the most frequent cause of PH. It is an increasingly recognized clinical complication of the metabolic syndrome. To date, no effective treatment has been identified, and no genetically modifiable mouse model is available for advancing our understanding for PH-HFpEF. To develop a mouse model of PH-HFpEF, we exposed 36 mouse strains to 20 weeks of high-fat diet (HFD), followed by systematic evaluation of right ventricular (RV) and LV pressure-volume analysis. The HFD induces obesity, glucose intolerance, insulin resistance, hyperlipidemia, as well as PH, in susceptible strains. We observed that certain mouse strains, such as AKR/J, NON/shiLtJ, and WSB/EiJ, developed hemodynamic signs of PH-HFpEF. Of the strains that develop PH-HFpEF, we selected AKR/J for further model validation, as it is known to be prone to HFD-induced metabolic syndrome and had low variability in hemodynamics. HFD-treated AKR/J mice demonstrate reproducibly higher RV systolic pressure compared with mice fed with regular diet, along with increased LV end-diastolic pressure, both RV and LV hypertrophy, glucose intolerance, and elevated HbA1c levels. Time course assessments showed that HFD significantly increased body weight, RV systolic pressure, LV end-diastolic pressure, biventricular hypertrophy, and HbA1c throughout the treatment period. Moreover, we also identified and validated 129S1/SvlmJ as a resistant mouse strain to HFD-induced PH-HFpEF. These studies validate an HFD/AKR/J mouse model of PH-HFpEF, which may offer a new avenue for testing potential mechanisms and treatments for this disease.

TSP1-CD47 signaling is upregulated in clinical pulmonary hypertension and contributes to pulmonary arterial vasculopathy and dysfunction

AIMS

Thrombospondin-1 (TSP1) is a ligand for CD47 and TSP1-/- mice are protected from pulmonary hypertension (PH). We hypothesized the TSP1-CD47 axis is upregulated in human PH and promotes pulmonary arterial vasculopathy.

METHODS AND RESULTS

We analyzed the molecular signature and functional response of lung tissue and distal pulmonary arteries (PAs) from individuals with (n = 23) and without (n = 16) PH. Compared with controls, lungs and distal PAs from PH patients showed induction of TSP1-CD47 and endothelin-1/endothelin A receptor (ET-1/ETA) protein and mRNA. In control PAs, treatment with exogenous TSP1 inhibited vasodilation and potentiated vasoconstriction to ET-1. Treatment of diseased PAs from PH patients with a CD47 blocking antibody improved sensitivity to vasodilators. Hypoxic wild type (WT) mice developed PH and displayed upregulation of pulmonary TSP1, CD47, and ET-1/ETA concurrent with down regulation of the transcription factor cell homolog of the v-myc oncogene (cMyc). In contrast, PH was attenuated in hypoxic CD47-/- mice while pulmonary TSP1 and ET-1/ETA were unchanged and cMyc was overexpressed. In CD47-/- pulmonary endothelial cells cMyc was increased and ET-1 decreased. In CD47+/+ cells, forced induction of cMyc suppressed ET-1 transcript, whereas suppression of cMyc increased ET-1 signaling. Furthermore, disrupting TSP1-CD47 signaling in pulmonary smooth muscle cells abrogated ET-1-stimulated hypertrophy. Finally, a CD47 antibody given 2 weeks after monocrotaline challenge in rats upregulated pulmonary cMyc and improved aberrations in PH-associated cardiopulmonary parameters.

CONCLUSIONS

In pre-clinical models of PH CD47 targets cMyc to increase ET-1 signaling. In clinical PH TSP1-CD47 is upregulated, and in both, contributes to pulmonary arterial vasculopathy and dysfunction.

Acute hemodynamic effects of inhaled sodium nitrite in pulmonary hypertension associated with heart failure with preserved ejection fraction

BACKGROUND

Pulmonary hypertension (PH) is associated with poor outcomes, yet specific treatments only exist for a small subset of patients. The most common form of PH is that associated with left heart disease (Group 2), for which there is no approved therapy. Nitrite has shown efficacy in preclinical animal models of Group 1 and 2 PH, as well as in patients with left heart failure with preserved ejection fraction (HFpEF). We evaluated the safety and efficacy of a potentially novel inhaled formulation of nitrite in PH-HFpEF patients as compared with Group 1 and 3 PH.

METHODS

Cardiopulmonary hemodynamics were recorded after acute administration of inhaled nitrite at 2 doses, 45 and 90 mg. Safety endpoints included change in systemic blood pressure and methemoglobin levels. Responses were also compared with those administered inhaled nitric oxide.

RESULTS

Thirty-six patients were enrolled (10 PH-HFpEF, 20 Group 1 pulmonary arterial hypertension patients on background PH-specific therapy, and 6 Group 3 PH). Drug administration was well tolerated. Nitrite inhalation significantly lowered pulmonary, right atrial, and pulmonary capillary wedge pressures, most pronounced in patients with PH-HFpEF. There was a modest decrease in cardiac output and systemic blood pressure. Pulmonary vascular resistance decreased only in Group 3 PH patients. There was substantial increase in pulmonary artery compliance, most pronounced in patients with PH-HFpEF.

CONCLUSIONS

Inhaled nitrite is safe in PH patients and may be efficacious in PH-HFpEF and Group 3 PH primarily via improvements in left and right ventricular filling pressures and pulmonary artery compliance. The lack of change in pulmonary vascular resistance likely may limit efficacy for Group 1 patients.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01431313 FUNDING. This work was supported in part by the NIH grants P01HL103455 (to MAS and MTG), R01HL098032 (to MTG), and R01HL096973 (to MTG), and Mast Therapeutics, Inc.

Vascular stiffness mechanoactivates YAP/TAZ-dependent glutaminolysis to drive pulmonary hypertension

Dysregulation of vascular stiffness and cellular metabolism occurs early in pulmonary hypertension (PH). However, the mechanisms by which biophysical properties of the vascular extracellular matrix (ECM) relate to metabolic processes important in PH remain undefined. In this work, we examined cultured pulmonary vascular cells and various types of PH-diseased lung tissue and determined that ECM stiffening resulted in mechanoactivation of the transcriptional coactivators YAP and TAZ (WWTR1). YAP/TAZ activation modulated metabolic enzymes, including glutaminase (GLS1), to coordinate glutaminolysis and glycolysis. Glutaminolysis, an anaplerotic pathway, replenished aspartate for anabolic biosynthesis, which was critical for sustaining proliferation and migration within stiff ECM. In vitro, GLS1 inhibition blocked aspartate production and reprogrammed cellular proliferation pathways, while application of aspartate restored proliferation. In the monocrotaline rat model of PH, pharmacologic modulation of pulmonary vascular stiffness and YAP-dependent mechanotransduction altered glutaminolysis, pulmonary vascular proliferation, and manifestations of PH. Additionally, pharmacologic targeting of GLS1 in this model ameliorated disease progression. Notably, evaluation of simian immunodeficiency virus-infected nonhuman primates and HIV-infected subjects revealed a correlation between YAP/TAZ-GLS activation and PH. These results indicate that ECM stiffening sustains vascular cell growth and migration through YAP/TAZ-dependent glutaminolysis and anaplerosis, and thereby link mechanical stimuli to dysregulated vascular metabolism. Furthermore, this study identifies potential metabolic drug targets for therapeutic development in PH.

SIRT3-AMP-Activated Protein Kinase Activation by Nitrite and Metformin Improves Hyperglycemia and Normalizes Pulmonary Hypertension Associated With Heart Failure With Preserved Ejection Fraction

BACKGROUND

Pulmonary hypertension associated with heart failure with preserved ejection fraction (PH-HFpEF) is an increasingly recognized clinical complication of metabolic syndrome. No adequate animal model of PH-HFpEF is available, and no effective therapies have been identified to date. A recent study suggested that dietary nitrate improves insulin resistance in endothelial nitric oxide synthase null mice, and multiple studies have reported that both nitrate and its active metabolite, nitrite, have therapeutic activity in preclinical models of pulmonary hypertension.

METHODS AND RESULTS

To evaluate the efficacy and mechanism of nitrite in metabolic syndrome associated with PH-HFpEF, we developed a 2-hit PH-HFpEF model in rats with multiple features of metabolic syndrome attributable to double-leptin receptor defect (obese ZSF1) with the combined treatment of vascular endothelial growth factor receptor blocker SU5416. Chronic oral nitrite treatment improved hyperglycemia in obese ZSF1 rats by a process that requires skeletal muscle SIRT3-AMPK-GLUT4 signaling. The glucose-lowering effect of nitrite was abolished in SIRT3-deficient human skeletal muscle cells, and in SIRT3 knockout mice fed a high-fat diet, as well. Skeletal muscle biopsies from humans with metabolic syndrome after 12 weeks of oral sodium nitrite and nitrate treatment (IND#115926) displayed increased activation of SIRT3 and AMP-activated protein kinase. Finally, early treatments with nitrite and metformin at the time of SU5416 injection reduced pulmonary pressures and vascular remodeling in the PH-HFpEF model with robust activation of skeletal muscle SIRT3 and AMP-activated protein kinase.

CONCLUSIONS

These studies validate a rodent model of metabolic syndrome and PH-HFpEF, suggesting a potential role of nitrite and metformin as a preventative treatment for this disease.

RV-pulmonary arterial coupling predicts outcome in patients referred for pulmonary hypertension

OBJECTIVE

Prognosis in pulmonary hypertension (PH) is largely determined by RV function. However, uncertainty remains about what metrics of RV function might be most clinically relevant. The purpose of this study was to assess the clinical relevance of metrics of RV functional adaptation to increased afterload.

METHODS

Patients referred for PH underwent right heart catheterisation and RV volumetric assessment within 48 h. A RV maximum pressure (Pmax) was calculated from the RV pressure curve. The adequacy of RV systolic functional adaptation to increased afterload was estimated either by a stroke volume (SV)/end-systolic volume (ESV) ratio, a Pmax/mean pulmonary artery pressure (mPAP) ratio, or by EF (RVEF). Diastolic function of the RV was estimated by a diastolic elastance coefficient β. Survival analysis was via Cox proportional HR, and Kaplan-Meier with the primary outcome of time to death or lung transplant.

RESULTS

Patients (n=50; age 58±13 yrs) covered a range of mPAP (13-79 mm Hg) with an average RVEF of 39±17% and ESV of 143±89 mL. Average estimates of the ratio of end-systolic ventricular to arterial elastance were 0.79±0.67 (SV/ESV) and 2.3±0.65 (Pmax/mPAP-1). Transplantation-free survival was predicted by right atrial pressure, mPAP, pulmonary vascular resistance, β, SV, ESV, SV/ESV and RVEF, but after controlling for right atrial pressure, mPAP, and SV, SV/ESV was the only independent predictor.

CONCLUSIONS

The adequacy of RV functional adaptation to afterload predicts survival in patients referred for PH. Whether this can simply be evaluated using RV volumetric imaging will require additional confirmation.

Patchy deletion of Bmpr1a potentiates proximal pulmonary artery remodeling in mice exposed to chronic hypoxia

Reduced vascular expression of bone morphogenetic protein type IA receptor (Bmpr1a) has been found in patients with pulmonary arterial hypertension. Our previous studies in mice with patchy deletion of Bmpr1a in vascular smooth muscle cells and cardiac myocytes showed decreased distal vascular remodeling despite a similar severity of hypoxic pulmonary hypertension (HPH). We speculate increased stiffness from ectopic deposition of collagen in proximal pulmonary arteries might account for HPH. Pulsatile pressure-flow relationships were measured in isolated, ventilated, perfused lungs of SM22α;TRE-Cre;R26R;Bmpr1a(flox/flox) (KO) mice and wild-type littermates, following 21 days (hypoxia) and 0 days (control) of chronic hypoxia. Pulmonary vascular impedance, which yields insight into proximal and distal arterial remodeling, was calculated. Reduced Bmpr1a expression had no effect on input impedance Z(0) (P = 0.52) or characteristic impedance Z(C) (P = 0.18) under control conditions; it also had no effect on the decrease in Z(0) via acute rho kinase inhibition. However, following chronic hypoxia, reduced Bmpr1a expression increased Z(C) (P < 0.001) without affecting Z(0) (P = 0.72). These results demonstrate that Bmpr1a deficiency does not significantly alter the hemodynamic function of the distal vasculature or its response to chronic hypoxia but larger, more proximal arteries are affected. In particular, reduced Bmpr1a expression likely decreased dilatation and increased stiffening in response to hypoxia, probably by collagen accumulation. Increased PA stiffness can have a significant impact on right ventricular function. This study illustrates for the first time how proximal pulmonary artery changes in the absence of distal pulmonary artery changes contribute to pulmonary arterial hypertension.

Exercise stress echocardiography of the pulmonary circulation: limits of normal and sex differences

BACKGROUND

Exercise stress echocardiography has not been recommended in the diagnostic workup of pulmonary hypertension because of insufficient certainty about feasibility and limits of normal.

METHODS

Doppler echocardiography pulmonary hemodynamic measurements were performed at a progressively increased workload in 56 healthy male and 57 healthy female volunteers aged 19 to 63 years. Mean pulmonary artery pressure (mPAP) was estimated from the maximal tricuspid regurgitation jet velocity. Cardiac index was calculated from the left ventricular outflow velocity-time integral. Pulmonary vascular distensibility a index, the percentage change of vessel diameter permm Hg of mPAP, was calculated from multipoint mPAP-cardiac output (CO) plots.

RESULTS

Peak exercise at 175 ±50 W was associated with an mPAP of 33±7 mm Hg and a CO of 18 ±5 L/min. The slope of mPAP-CO relationships was 1.5 ± 0.5 mm Hg/L/min, and the distensibility coefficient ( α ) was 1.3%± 1.0%/mm Hg. Maximal workload and cardiac index were higher in men than in women ( P , .05), but mPAP-cardiac index relationships were not different. However,women had a higher a (1.6%± 1.3%/mm Hg vs 1.1%± 0.6%/mm Hg, P < .05). The average mPAP-cardiac index slope was higher and a lower in subjects ≥50 years old. Upper limits of normal of mPAP at exercise were 34 mm Hg at a CO , 10 L/min, 45 mm Hg at a CO <20 L/min, and 52 mm Hg at a CO<30 L/min. These values are in keeping with previously reported invasive measurements.

CONCLUSIONS

Exercise stress echocardiography of the pulmonary circulation is feasible and allows for fl ow-corrected definition of upper limits of normal. Women have a more distensible pulmonary circulation.