How prostacyclin therapy improves right ventricular function in pulmonary arterial hypertension

SPECTRA Phase 2b Study: Impact of Sotatercept on Exercise Tolerance and Right Ventricular Function in Pulmonary Arterial Hypertension

BACKGROUND

This study aims to assess the impact of sotatercept on exercise tolerance, exercise capacity, and right ventricular function in pulmonary arterial hypertension.

METHODS

SPECTRA (Sotatercept Phase 2 Exploratory Clinical Trial in PAH) was a phase 2a, single-arm, open-label, multicenter exploratory study that evaluated the effects of sotatercept by invasive cardiopulmonary exercise testing in participants with pulmonary arterial hypertension and World Health Organization functional class III on combination background therapy. The primary end point was the change in peak oxygen uptake from baseline to week 24. Cardiac magnetic resonance imaging was performed to assess right ventricular function.

RESULTS

Among the 21 participants completing 24 weeks of treatment, there was a significant improvement from baseline in peak oxygen uptake, with a mean change of 102.74 mL/min ([95% CIs, 27.72-177.76]; P=0.0097). Sotatercept demonstrated improvements in secondary end points, including resting and peak exercise hemodynamics, and 6-minute walk distance versus baseline measures. Cardiac magnetic resonance imaging showed improvements from baseline at week 24 in right ventricular function.

CONCLUSIONS

The clinical efficacy and safety of sotatercept demonstrated in the SPECTRA study emphasize the potential of this therapy as a new treatment option for patients with pulmonary arterial hypertension. Improvements in right ventricular structure and function underscore the potential for sotatercept as a disease-modifying agent with reverse-remodeling capabilities.

REGISTRATION

URL: https://www.clinicaltrials.gov; Unique identifier: NCT03738150.

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.

Pathophysiology of the right ventricle in health and disease: an update

The contribution of the right ventricle (RV) to cardiac output is negligible in normal resting conditions when pressures in the pulmonary circulation are low. However, the RV becomes relevant in healthy subjects during exercise and definitely so in patients with increased pulmonary artery pressures both at rest and during exercise. The adaptation of RV function to loading rests basically on an increased contractility. This is assessed by RV end-systolic elastance (Ees) to match afterload assessed by arterial elastance (Ea). The system has reserve as the Ees/Ea ratio or its imaging surrogate ejection fraction has to decrease by more than half, before the RV undergoes an increase in dimensions with eventual increase in filling pressures and systemic congestion. RV-arterial uncoupling is accompanied by an increase in diastolic elastance. Measurements of RV systolic function but also of diastolic function predict outcome in any cause pulmonary hypertension and heart failure with or without preserved left ventricular ejection fraction. Pathobiological changes in the overloaded RV include a combination of myocardial fibre hypertrophy, fibrosis and capillary rarefaction, a titin phosphorylation-related displacement of myofibril tension-length relationships to higher pressures, a metabolic shift from mitochondrial free fatty acid oxidation to cytoplasmic glycolysis, toxic lipid accumulation, and activation of apoptotic and inflammatory signalling pathways. Treatment of RV failure rests on the relief of excessive loading.

Factors leading to supranormal cardiac index in pediatric pulmonary hypertension patients treated with parenteral prostanoid therapy

Parenteral prostanoid therapy (PPT) can result in supranormal cardiac index (SCI; >4 L/min/m²) in pediatric pulmonary hypertension (PPH) patients. We evaluated the incidence, hemodynamic factors, and outcomes associated with SCI in PPH. This retrospective cohort study included 22 PPH patients on PPT from 2005 to 2020. Hemodynamic profiles were compared between the baseline and 3-6 month follow-up catheterization in the SCI and non-SCI cohorts. Cox regression analysis examined time to composite adverse outcome (CAO; Potts shunt, lung transplant, or death) controlling for initial disease severity. SCI developed in 17 (77%) patients, of whom 11 (65%) developed SCI within 6 months. The SCI cohort was characterized by significant augmentation of cardiac index (CI) and stroke volume (SV) as well as reductions in systemic vascular resistance (SVR) and pulmonary vascular resistance (PVR). Conversely, the non-SCI cohort had unchanged SV despite a modest rise in CI as well as persistent vasoconstriction. After median follow-up of 4.3 years (range 0.2-13 years), non-SCI patients were at significantly increased risk for the CAO (5/5: three deaths, two Potts shunts) compared with SCI patients (5/17: two deaths, three lung transplants; adjusted hazard ratio 14.0 [95% confidence interval: 2.1-91.3], p < 0.001). A majority of PPH patients developed SCI within 6-12 months of starting PPT and demonstrated lower risk of adverse outcomes compared with non-SCI patients. These data suggest that change in SVR and SV after 3-6 months of PPT may be early markers of therapeutic response and prognosis.

Pathophysiology and pathogenic mechanisms of pulmonary hypertension: role of membrane receptors, ion channels, and Ca2+ signaling

The pulmonary circulation is a low-resistance, low-pressure, and high-compliance system that allows the lungs to receive the entire cardiac output. Pulmonary arterial pressure is a function of cardiac output and pulmonary vascular resistance, and pulmonary vascular resistance is inversely proportional to the fourth power of the intraluminal radius of the pulmonary artery. Therefore, a very small decrease of the pulmonary vascular lumen diameter results in a significant increase in pulmonary vascular resistance and pulmonary arterial pressure. Pulmonary arterial hypertension is a fatal and progressive disease with poor prognosis. Regardless of the initial pathogenic triggers, sustained pulmonary vasoconstriction, concentric vascular remodeling, occlusive intimal lesions, in situ thrombosis, and vascular wall stiffening are the major and direct causes for elevated pulmonary vascular resistance in patients with pulmonary arterial hypertension and other forms of precapillary pulmonary hypertension. In this review, we aim to discuss the basic principles and physiological mechanisms involved in the regulation of lung vascular hemodynamics and pulmonary vascular function, the changes in the pulmonary vasculature that contribute to the increased vascular resistance and arterial pressure, and the pathogenic mechanisms involved in the development and progression of pulmonary hypertension. We focus on reviewing the pathogenic roles of membrane receptors, ion channels, and intracellular Ca2+ signaling in pulmonary vascular smooth muscle cells in the development and progression of pulmonary hypertension.

Clinical Applications of Pressure-Volume Assessment in Congenital Heart Disease

Ventricular pressure-volume (PV) loops offer unique insights into cardiovascular mechanics. PV loops can be instrumental in improving our understanding of various congenital heart diseases, including single ventricular physiology, heart failure, and pulmonary hypertension, as well as guiding therapeutic interventions. This review focuses on the theoretical and practical foundations for the acquisition and interpretation of PV loops in congenital heart disease and discusses their clinical applications.

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.

Reversal of Right Ventricular Hypertrophy and Dysfunction by Prostacyclin in a Rat Model of Severe Pulmonary Arterial Hypertension

Prostacyclin analogs are among the most effective and widely used therapies for pulmonary arterial hypertension (PAH). However, it is unknown whether they also confer protection through right ventricle (RV) myocardio-specific mechanisms. Moreover, the use of prostacyclin analogs in severe models of PAH has not been adequately tested. To further identify underlying responses to prostacyclin, a prostacyclin analogue, treprostinil, was used in a preclinical rat Sugen-chronic hypoxia (SuCH) model of severe PAH that closely resembles the human disease. Male Sprague–Dawley rats were implanted with osmotic pumps containing vehicle or treprostinil, injected concurrently with a bolus of Sugen (SU5416) and exposed to 3-week hypoxia followed by 3-week normoxia. RV function was assessed using pressure–volume loops and hypertrophy by weight assessed. To identify altered mechanisms within the RV, tissue samples were used to perform a custom RNA array analysis, histological staining, and protein and transcript level confirmatory analyses. Treprostinil significantly reduced SuCH-associated RV hypertrophy and decreased the rise in RV systolic pressure, mean pulmonary arterial (mPAP), and right atrial (RAP) pressure. Prostacyclin treatment was associated with improvements in RV stroke work, maximum rate of ventricular pressure change (max dP/dt) and the contractile index, and almost a complete reversal of SuCH-associated increase in RV end-systolic elastance, suggesting the involvement of load-independent improvements in intrinsic RV systolic contractility by prostacyclin treatment. An analysis of the RV tissues showed no changes in cardiac mitochondrial respiration and ATP generation. However, custom RNA array analysis revealed amelioration of SuCH-associated increases in newly identified TBX20 as well as the fibrotic markers collagen1α1 and collagen 3α1 upon treprostinil treatment. Taken together, our data support decreased afterload and load-independent improvements in RV function following prostacyclin administration in severe PAH, and these changes appear to associate with improvements in RV fibrotic responses.

The physiologic basis of pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a rare dyspnea-fatigue syndrome caused by a progressive increase in pulmonary vascular resistance (PVR) and eventual right ventricular (RV) failure. In spite of extensive pulmonary vascular remodeling, lung function in PAH is generally well preserved, with hyperventilation and increased physiologic dead space, but minimal changes in lung mechanics and only mild to moderate hypoxemia and hypocapnia. Hypoxemia is mainly caused by a low mixed venous PO₂ from a decreased cardiac output. Hypocapnia is mainly caused by an increased chemosensitivity. Exercise limitation in PAH is cardiovascular rather than ventilatory or muscular. The extent of pulmonary vascular disease in PAH is defined by multipoint pulmonary vascular pressure-flow relationships with a correction for hematocrit. Pulsatile pulmonary vascular pressure-flow relationships in PAH allow for the assessment of RV hydraulic load. This analysis is possible either in the frequency-domain or in the time-domain. The RV in PAH adapts to increased afterload by an increased contractility to preserve its coupling to the pulmonary circulation. When this homeometric mechanism is exhausted, the RV dilates to preserve flow output by an additional heterometric mechanism. Right heart failure is then diagnosed by imaging of increased right heart dimensions and clinical systemic congestion signs and symptoms. The coupling of the RV to the pulmonary circulation is assessed by the ratio of end-systolic to arterial elastances, but these measurements are difficult. Simplified estimates of RV-PA coupling can be obtained by magnetic resonance or echocardiographic imaging of ejection fraction.

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.

Effect of riociguat on right ventricular function in patients with pulmonary arterial hypertension and chronic thromboembolic pulmonary hypertension

BACKGROUND

In the Phase III PATENT-1 (NCT00810693) and CHEST-1 (NCT00855465) studies, riociguat demonstrated efficacy vs placebo in patients with pulmonary arterial hypertension (PAH) and chronic thromboembolic pulmonary hypertension (CTEPH). Clinical effects were maintained at 2 years in the long-term extension studies PATENT-2 (NCT00863681) and CHEST-2 (NCT00910429).

METHODS

This post hoc analysis of hemodynamic data from PATENT-1 and CHEST-1 assessed whether riociguat improved right ventricular (RV) function parameters including stroke volume index (SVI), stroke volume, RV work index, and cardiac efficiency. REVEAL Risk Score (RRS) was calculated for patients stratified by SVI and right atrial pressure (RAP) at baseline and follow-up. The association between RV function parameters and SVI and RAP stratification with long-term outcomes was assessed.

RESULTS

In PATENT-1 (n = 341) and CHEST-1 (n = 238), riociguat improved RV function parameters vs placebo (p < 0.05). At follow-up, there were significant differences in RRS between patients with favorable and unfavorable SVI and RAP, irrespective of treatment arm (p < 0.0001). Multiple RV function parameters at baseline and follow-up were associated with survival and clinical worsening-free survival (CWFS) in PATENT-2 (n = 396; p < 0.05) and CHEST-2 (n = 237). In PATENT-2, favorable SVI and RAP at follow-up only was associated with survival and CWFS (p < 0.05), while in CHEST-2, favorable SVI and RAP at baseline and follow-up were associated with survival and CWFS (p < 0.05).

CONCLUSION

This post hoc analysis of PATENT and CHEST suggests that riociguat improves RV function in patients with PAH and CTEPH.

Right Heart Size and Right Ventricular Reserve in Pulmonary Hypertension: Impact on Management and Prognosis

Various parameters reflecting right heart size, right ventricular function and capacitance have been shown to be prognostically important in patients with pulmonary hypertension (PH). In the advanced disease, patients suffer from right heart failure, which is a main reason for an impaired prognosis. Right heart size has shown to be associated with right ventricular function and reserve and is correlated with prognosis in patients with PH. Right ventricular reserve, defined as the ability of the ventricle to adjust to exercise or pharmacologic stress, is expressed by various parameters, which may be determined invasively by right heart catheterization or by stress-Doppler-echocardiography as a noninvasive approach. As the term "right ventricular contractile reserve" may be misleading, "right ventricular output reserve" seems desirable as a preferred term of increase in cardiac output during exercise. Both right heart size and right ventricular reserve have been shown to be of prognostic importance and may therefore be useful for risk assessment in patients with pulmonary hypertension. In this article we aim to display different aspects of right heart size and right ventricular reserve and their prognostic role in PH.

Acute Unloading Effects of Sildenafil Enhance Right Ventricular-Pulmonary Artery Coupling in Heart Failure

BACKGROUND

Phosphodiesterase-5A inhibitors (PDE5i) are sometimes used in patients with advanced heart failure with reduced ejection fraction before heart transplant or left ventricular assist device implantation to decrease right ventricular (RV) afterload and mitigate the risk of right heart failure. Conflicting evidence exists regarding the impact of these drugs on RV contractility. The aim of this study was to explore the acute effects of PDE5i on ventricular-vascular coupling and load-independent RV contractility.

METHODS

Twenty-two patients underwent right heart catheterization and gated equilibrium blood pool single photon emission computed tomography, before and after 20 mg intravenous sildenafil. Single photon emission computed tomography and right heart catheterization-derived data were used to calculate RV loading and contractility.

RESULTS

PDE5i induced a decrease in the right atrial pressure (-43%), pulmonary artery (PA) mean pressure (-26%), and PA wedge pressure (PAWP; -23%), with favorable reductions in pulmonary vascular resistance (-41%) and PA elastance (-40%), and increased cardiac output (+13%) (all P < 0.01). The RV ejection fraction increased with sildenafil (+20%), with no change of RV contractility (P = 0.74), indicating that the improvement in the RV ejection fraction was related to enhanced RV-PA coupling (r = 0.59, P = 0.004) by a decrease in the ventricular load. RV diastolic compliance increased with sildenafil. The decrease in the PAWP correlated with RV end-diastolic volume decrease; no relationship was observed with the change in LV transmural pressure, suggesting decreased pericardial constraint.

CONCLUSIONS

Acute PDE5i administration has profound RV afterload-reducing effects, improves the RVEF, decreases RV volumes, and decreases the PAWP, predominantly through relief of pericardial constraint, without effects on RV chamber contractility. These findings support further study of PDE5i in protection of RV function in advanced heart failure with reduced ejection fraction who are at risk of RV failure.

Mechanics of right ventricular dysfunction in pulmonary arterial hypertension and heart failure with preserved ejection fraction

Right ventricular (RV) dysfunction is the most important determinant of survival in patients with pulmonary hypertension (PH). The manifestations of RV dysfunction not only include changes in global RV systolic function but also abnormalities in the pattern of contraction and synchrony. The effects of PH on the right ventricle have been mainly studied in patients with pulmonary arterial hypertension (PAH). However, with the demographic shift towards an aging population, heart failure with preserved ejection fraction (HFpEF) has become an important etiology of PH in recent years. There are significant differences in RV mechanics, function and adaptation between patients with PAH and HFpEF (with or without PH), which are related to different patterns of remodeling and dysfunction. Due to the unique features of the RV chamber, its connection with the main pulmonary artery and the pulmonary circulation, an understanding of the mechanics of RV function and its clinical significance is mandatory for both entities. In this review, we describe the mechanics of the pressure overloaded right ventricle. We review the different mechanical components of RV dysfunction and ventricular dyssynchrony, followed by insights via analysis of pressure-volume loop, energetics and novel blood flow patterns, such as vortex imaging. We conduct an in-depth comparison of prevalence and characteristics of RV dysfunction in HFpEF and PAH, and summarize key outcome studies. Finally, we provide a perspective on needed and expected future work in the field of RV mechanics.

Novel dose-response analyses of treprostinil in pulmonary arterial hypertension and its effects on six-minute walk distance and hospitalizations

Treprostinil is a prostacyclin analogue approved for the treatment of pulmonary arterial hypertension. Apart from the inhaled formulation, there is neither a target dose nor a ceiling dose to guide clinicians using treprostinil; doses are individualized for each patient based upon tolerability and clinical improvement. Using combined data from the pivotal subcutaneous and oral treprostinil studies, we evaluated the effect of treprostinil dose on hospitalization and exercise capacity to better define the treprostinil dose–response relationship. Data from the pivotal subcutaneous and oral treprostinil studies were combined by converting oral doses to weight-based continuous doses (ng/kg/min) accounting for patient weight and bioavailability. Patients were divided into dose tertiles (lowest, middle, highest 33%) and retrospectively analyzed. Analysis 1 assessed the effect of dose on pulmonary arterial hypertension-related and all-cause hospitalizations. Analysis 2 evaluated the effects of dose on six-minute walk distance, Borg dyspnea score, and World Health Organization functional class. Results showed that, in Analysis 1, higher doses of treprostinil were associated with significantly longer times to first pulmonary arterial hypertension-related and all-cause hospitalization. In Analysis 2, there was a trend toward improvements in six-minute walk distance with higher doses. In patients with pulmonary arterial hypertension on systemic treprostinil therapy, higher doses were associated with significantly longer time to first pulmonary arterial hypertension-related and all-cause hospitalization. There was a trend toward improvements in six-minute walk distance. Collectively, these results underscore the importance of managing prostacyclin adverse events in order to achieve appropriate dose titration. Further studies are required to confirm these findings and to better characterize the dose–response relationship of treprostinil.

Right heart failure in pulmonary hypertension: Diagnosis and new perspectives on vascular and direct right ventricular treatment

Adaptation of right ventricular (RV) function to increased afterload-known as RV-arterial coupling-is a key determinant of prognosis in pulmonary hypertension. However, measurement of RV-arterial coupling is a complex, invasive process involving analysis of the RV pressure-volume relationship during preload reduction over multiple cardiac cycles. Simplified methods have therefore been proposed, including echocardiographic and cardiac MRI approaches. This review describes the available methods for assessment of RV function and RV-arterial coupling and the effects of pharmacotherapy on these variables. Overall, pharmacotherapies for pulmonary hypertension have shown beneficial effects on various measures of RV function, but it is often unclear if these are direct RV effects or indirect results of afterload reduction. Studies of the effects of pharmacotherapies on RV-arterial coupling are limited and mostly restricted to experimental models. Simplified methods to assess RV-arterial coupling should be validated and incorporated into routine clinical follow-up and future clinical trials. LINKED ARTICLES: This article is part of a themed issue on Risk factors, comorbidities, and comedications in cardioprotection. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v178.1/issuetoc.

Right ventricular function in pulmonary (arterial) hypertension

The right ventricle (RV) is the main determinant of prognosis in pulmonary hypertension. Adaptation and maladaptation of the RV are of crucial importance. In the course of disease, RV contractility increases through changes in muscle properties and muscle hypertrophy. At a certain point, the point of "uncoupling," the afterload exceeds contractility, and maladaptation as well as dilation occurs to maintain stroke volume (SV). To understand the adaptational processes and to further develop targeted medication directly affecting load-independent contractility, an accurate and precise assessment of contractility and RV-pulmonary artery (PA) coupling should be performed. In this review, we shed light on existing methods to assess RV function, including the gold standard measurement of contractility and RV-PA coupling, and we evaluate existing surrogates of RV-PA coupling.

Acute response to rapid iloprost inhalation using the Breelib™ nebulizer in pulmonary arterial hypertension: the Breelib™ acute study

The Breelib™ nebulizer was designed to reduce iloprost inhalation times for patients with pulmonary arterial hypertension (PAH). In 30 patients with PAH, rapid inhalation of iloprost 2.5 µg using Breelib™ caused significant improvements in invasively measured afterload and cardiac index but not echocardiographic right ventricular strain during 30 min post-inhalation.

Validation of the Tricuspid Annular Plane Systolic Excursion/Systolic Pulmonary Artery Pressure Ratio for the Assessment of Right Ventricular-Arterial Coupling in Severe Pulmonary Hypertension

BACKGROUND

The ratios of tricuspid annular plane systolic excursion (TAPSE)/echocardiographically measured systolic pulmonary artery pressure (PASP), fractional area change/invasively measured mean pulmonary artery pressure, right ventricular (RV) area change/end-systolic area, TAPSE/pulmonary artery acceleration time, and stroke volume/end-systolic area have been proposed as surrogates of RV-arterial coupling. The relationship of these surrogates with the gold standard measure of RV-arterial coupling (invasive pressure-volume loop-derived end-systolic/arterial elastance [Ees/Ea] ratio) and RV diastolic stiffness (end-diastolic elastance) in pulmonary hypertension remains incompletely understood. We evaluated the relationship of these surrogates with invasive pressure-volume loop-derived Ees/Ea and end-diastolic elastance in pulmonary hypertension.

METHODS

We performed right heart echocardiography and cardiac magnetic resonance imaging 1 day before invasive measurement of pulmonary hemodynamics and single-beat RV pressure-volume loops in 52 patients with pulmonary arterial hypertension or chronic thromboembolic pulmonary hypertension. The relationships of the proposed surrogates with Ees/Ea and end-diastolic elastance were evaluated by Spearman correlation, multivariate logistic regression, and receiver operating characteristic analyses. Associations with prognosis were evaluated by Kaplan-Meier analysis.

RESULTS

TAPSE/PASP, fractional area change/mean pulmonary artery pressure, RV area change/end-systolic area, and stroke volume/end-systolic area but not TAPSE/pulmonary artery acceleration time were correlated with Ees/Ea and end-diastolic elastance. Of the surrogates, only TAPSE/PASP emerged as an independent predictor of Ees/Ea (multivariate odds ratio: 18.6; 95% CI, 0.8-96.1; P=0.08). In receiver operating characteristic analysis, a TAPSE/PASP cutoff of 0.31 mm/mm Hg (sensitivity: 87.5% and specificity: 75.9%) discriminated RV-arterial uncoupling (Ees/Ea <0.805). Patients with TAPSE/PASP <0.31 mm/mm Hg had a significantly worse prognosis than those with higher TAPSE/PASP.

CONCLUSIONS

Echocardiographically determined TAPSE/PASP is a straightforward noninvasive measure of RV-arterial coupling and is affected by RV diastolic stiffness in severe pulmonary hypertension.

CLINICAL TRIAL REGISTRATION

URL: https://www.clinicaltrials.gov. Unique identifier: NCT03403868.

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.

The right ventricular response to lung resection

OBJECTIVES

Lung cancer is a leading cause of cancer death and in suitable cases the best chance of cure is offered by surgery. Lung resection is associated with significant postoperative cardiorespiratory morbidity, with dyspnea and reduced functional capacity as dominant features. These changes are poorly associated with deterioration in pulmonary function and a potential role of right ventricular (RV) dysfunction has been hypothesized. Cardiovascular magnetic resonance imaging is a reference method for noninvasive assessment of RV function and has not previously been applied to this population.

METHODS

We used cardiovascular magnetic resonance imaging to assess the RV response to lung resection. Cardiovascular magnetic resonance imaging with volume and flow analysis was performed on 27 patients preoperatively, on postoperative day 2 and at 2 months. Left ventricular ejection fraction and RV ejection fraction, the ratio of stroke volume to end systolic volume, pulmonary artery acceleration time, and distensibility of main and branch pulmonary arteries were studied.

RESULTS

Mean ± standard deviation RV ejection fraction deteriorated from 50.5% ± 6.9% preoperatively to 45.6% ± 4.5% on postoperative day 2 and remained depressed at 44.9% ± 7.7% by 2 months (P = .003). The ratio of stroke volume to end systolic volume deteriorated from median 1.0 (quartile 1, quartile 3: 0.9, 1.2) preoperatively to median 0.8 (quartile 1, quartile 3: 0.7, 1.0) on postoperative day 2 (P = .011). On postoperative day 2 there was a decrease in pulmonary artery acceleration time and operative pulmonary artery distensibility (P < .030 for both). There were no changes in left ventricular ejection fraction during the study period (P = .621).

CONCLUSIONS

These findings suggest RV dysfunction occurs following lung resection and persists 2 months after surgery. The deterioration in the ratio of stroke volume to end systolic volume suggests a mismatch between afterload and contractility. There is an increase in indices of pulsatile afterload resulting from the operative pulmonary artery.

The Role of G Protein-Coupled Receptors in the Right Ventricle in Pulmonary Hypertension

Pressure overload of the right ventricle (RV) in pulmonary arterial hypertension (PAH) leads to RV remodeling and failure, an important determinant of outcome in patients with PAH. Several G protein-coupled receptors (GPCRs) are differentially regulated in the RV myocardium, contributing to the pathogenesis of RV adverse remodeling and dysfunction. Many pharmacological agents that target GPCRs have been demonstrated to result in beneficial effects on left ventricular (LV) failure, such as beta-adrenergic receptor and angiotensin receptor antagonists. However, the role of such drugs on RV remodeling and performance is not known at this time. Moreover, many of these same receptors are also expressed in the pulmonary vasculature, which could result in complex effects in PAH. This manuscript reviews the role of GPCRs in the RV remodeling and dysfunction and discusses activating and blocking GPCR signaling to potentially attenuate remodeling while promoting improvements of RV function in PAH.

Right heart size and function significantly correlate in patients with pulmonary arterial hypertension - a cross-sectional study

BACKGROUND

The objective of this study was to assess, whether right atrial (RA) and ventricular (RV) size is related to RV pump function at rest and during exercise in patients with pulmonary arterial hypertension (PAH).

METHODS

We included 54 patients with invasively diagnosed PAH that had been stable on targeted medication. All patients underwent clinical assessments including right heart catheterization and echocardiography at rest and during exercise. RV output reserve was defined as increase of cardiac index (CI) from rest to peak exercise (∆CI_exercise). Patients were classified according to the median of RA and RV-area. RV pump function and further clinical parameters were compared between groups by student's t-test. Uni- and multivariate Pearson correlation analyses were performed.

RESULTS

Patients with larger RA and/or RV-areas (above a median of 16 and 20cm², respectively) showed significantly lower ∆CI_exercise, higher mean pulmonary arterial pressure, pulmonary vascular resistance at rest and NT-proBNP levels. Furthermore, patients with higher RV-areas presented with a significantly lower RV stroke volume and pulmonary arterial compliance at peak exercise than patients with smaller RV-size. RV area was identified as the only independent predictor of RV output reserve.

CONCLUSION

RV and RA areas represent valuable and easily accessible indicators of RV pump function at rest and during exercise. Cardiac output reserve should be considered as an important clinical parameter. Prospective studies are needed for further evaluation.

The Right Heart-Pulmonary Circulation Unit: Physiopathology

The most common cause of right heart failure is increased afterload caused by pulmonary hypertension. Right ventricular function adaptation to increased afterload is basically systolic, with secondary increase in dimensions and systemic congestion. Increased right ventricular dimensions and decreased ejection fraction are associated with a decreased survival in severe pulmonary hypertension. Targeted therapies titrated to reverse the right ventricular remodeling dimensions improve survival in severe pulmonary hypertension.