The Biological Bases of Group 2 Pulmonary Hypertension

Pulmonary hypertension associated to left heart disease: Phenotypes and treatment

Pulmonary hypertension associated to left heart disease (PH-LHD) refers to a clinical and haemodynamic condition of pulmonary hypertension associated with a heterogeneous group of diseases affecting any of the compartments that form the left ventricle and left atrium. PH-LHD is the most common cause of PH, accounting for 65-80 % of diagnoses. Based on the haemodynamic phase of the disease, PH-LDH is classified into three subgroups: postcapillary PH, isolated postcapillary PH and combined pre-postcapillary PH (CpcPH). Several signaling pathways involved in the regulation of vascular tone are dysfunctional in PH-LHD, including nitric oxide, MAP kinase and endothelin-1 pathways. These pathways are the same as those altered in PH group 1, however PH-LHD can heardly be treated by specific drugs that act on the pulmonary circulation. In this manuscript we provide a state of the art of the available clinical trials investigating the safety and efficacy of PAH-specific drugs, as well as drugs active in patients with heart failure and PH-LHD. We also discuss the different phenotypes of PH-LHD, as well as molecular targets and signaling pathways potentially involved in the pathophysiology of the disease. Finally we will mention some new emerging therapies that can be used to treat this form of PH.

Pulmonary Vasodilator and Inodilator Drugs in Cardiac Surgery: A Systematic Review With Bayesian Network Meta-Analysis

OBJECTIVE

The authors performed a systematic review to evaluate the effect of pharmacologic therapy on pulmonary hypertension in the perioperative setting of elective cardiac surgery (PROSPERO CRD42023321041).

DESIGN

Systematic review of randomized controlled trials with a Bayesian network meta-analysis.

SETTING

The authors searched biomedical databases for randomized controlled trials on the perioperative use of inodilators and pulmonary vasodilators in adult cardiac surgery, with in-hospital mortality as the primary outcome and duration of ventilation, length of stay in the intensive care unit, stage 3 acute kidney injury, cardiogenic shock requiring mechanical support, and change in mean pulmonary artery pressure as secondary outcomes.

PARTICIPANTS

Twenty-eight studies randomizing 1,879 patients were included.

INTERVENTIONS

Catecholamines and noncatecholamine inodilators, arterial pulmonary vasodilators, vasodilators, or their combination were considered eligible interventions compared with placebo or standard care.

MEASUREMENTS AND MAIN RESULTS

Ten studies reported in-hospital mortality and assigned 855 patients to 12 interventions. Only inhaled prostacyclin use was supported by a statistically discernible improvement in mortality, with a number-needed-to-treat estimate of at least 3.3, but a wide credible interval (relative risk 1.26 × 10-17 - 0.7). Inhaled prostacyclin and nitric oxide were associated with a reduction in intensive care unit stay, and none of the included interventions reached a statistically evident difference compared to usual care or placebo in the other secondary clinical outcomes.

CONCLUSIONS

Inhaled prostacyclin was the only pharmacologic intervention whose use is supported by a statistically discernible improvement in mortality in the perioperative cardiac surgery setting as treatment of pulmonary hypertension. However, available evidence has significant limitations, mainly the low number of events and imprecision.

Pulmonary Hypertension in Left Heart Diseases: Pathophysiology, Hemodynamic Assessment and Therapeutic Management

Pulmonary hypertension (PH) associated with left heart diseases (PH-LHD), also termed group 2 PH, represents the most common form of PH. It develops through the passive backward transmission of elevated left heart pressures in the setting of heart failure, either with preserved (HFpEF) or reduced (HFrEF) ejection fraction, which increases the pulsatile afterload of the right ventricle (RV) by reducing pulmonary artery (PA) compliance. In a subset of patients, progressive remodeling of the pulmonary circulation resulted in a pre-capillary phenotype of PH, with elevated pulmonary vascular resistance (PVR) further increasing the RV afterload, eventually leading to RV-PA uncoupling and RV failure. The primary therapeutic objective in PH-LHD is to reduce left-sided pressures through the appropriate use of diuretics and guideline-directed medical therapies for heart failure. When pulmonary vascular remodeling is established, targeted therapies aiming to reduce PVR are theoretically appealing. So far, such targeted therapies have mostly failed to show significant positive effects in patients with PH-LHD, in contrast to their proven efficacy in other forms of pre-capillary PH. Whether such therapies may benefit some specific subgroups of patients (HFrEF, HFpEF) with specific hemodynamic phenotypes (post- or pre-capillary PH) and various degrees of RV dysfunction still needs to be addressed.

Optical coherence tomography assessment of pulmonary vascular remodeling in advanced heart failure. The OCTOPUS-CHF study

INTRODUCTION AND OBJECTIVES

Pulmonary vascular remodeling is common among patients with advanced heart failure. Right heart catheterization is the gold standard to assess pulmonary hypertension, but is limited by indirect measurement assumptions, a steady-flow view, load-dependency, and interpretation variability. We aimed to assess pulmonary vascular remodeling with intravascular optical coherence tomography (OCT) and to study its correlation with hemodynamic data.

METHODS

This observational, prospective, multicenter study recruited 100 patients with advanced heart failure referred for heart transplant evaluation. All patients underwent right heart catheterization together with OCT evaluation of a subsegmentary pulmonary artery.

RESULTS

OCT could be performed and properly analyzed in 90 patients. Median age was 57.50 [interquartile range, 48.75-63.25] years and 71 (78.88%) were men. The most frequent underlying heart condition was nonischemic dilated cardiomyopathy (33 patients [36.66%]). Vascular wall thickness significantly correlated with mean pulmonary artery pressure, pulmonary vascular resistance, and transpulmonary gradient (R coefficient=0.42, 0.27 and 0.32 respectively). Noninvasive estimation of pulmonary artery systolic pressure, acceleration time, and right ventricle-pulmonary artery coupling also correlated with wall thickness (R coefficient of 0.42, 0.27 and 0.49, respectively). Patients with a wall thickness over 0.25mm had significantly higher mean pulmonary pressures (37.00 vs 25.00mmHg; P=.004) and pulmonary vascular resistance (3.44 vs 2.08 WU; P=.017).

CONCLUSIONS

Direct morphological assessment of pulmonary vascular remodeling with OCT is feasible and is significantly associated with classic hemodynamic parameters. This weak association suggests that structural remodeling does not fully explain pulmonary hypertension.

Pathogenesis of pulmonary hypertension caused by left heart disease

Pulmonary hypertension has high disability and mortality rates. Among them, pulmonary hypertension caused by left heart disease (PH-LHD) is the most common type. According to the 2022 ESC/ERS Guidelines for the diagnosis and treatment of pulmonary hypertension, PH-LHD is classified as group 2 pulmonary hypertension. PH-LHD belongs to postcapillary pulmonary hypertension, which is distinguished from other types of pulmonary hypertension because of its elevated pulmonary artery wedge pressure. PH-LHD includes PH due to systolic or diastolic left ventricular dysfunction, mitral or aortic valve disease and congenital left heart disease. The primary strategy in managing PH-LHD is optimizing treatment of the underlying cardiac disease. Recent clinical studies have found that mechanical unloading of left ventricle by an implantable non-pulsatile left ventricular assist device with continuous flow properties can reverse pulmonary hypertension in patients with heart failure. However, the specific therapies for PH in LHD have not yet been identified. Treatments that specifically target PH in LHD could slow its progression and potentially improve disease severity, leading to far better clinical outcomes. Therefore, exploring the current research on the pathogenesis of PH-LHD is important. This paper summarizes and classifies the research articles on the pathogenesis of PH-LHD to provide references for the mechanism research and clinical treatment of PH-LHD, particularly molecular targeted therapy.

The Evolving Management and Treatment Options for Patients with Pulmonary Hypertension: Current Evidence and Challenges

Pulmonary hypertension may develop as a disease process specific to pulmonary arteries with no identifiable cause or may occur in relation to other cardiopulmonary and systemic illnesses. The World Health Organization (WHO) classifies pulmonary hypertensive diseases on the basis of primary mechanisms causing increased pulmonary vascular resistance. Effective management of pulmonary hypertension begins with accurately diagnosing and classifying the disease in order to determine appropriate treatment. Pulmonary arterial hypertension (PAH) is a particularly challenging form of pulmonary hypertension as it involves a progressive, hyperproliferative arterial process that leads to right heart failure and death if untreated. Over the last two decades, our understanding of the pathobiology and genetics behind PAH has evolved and led to the development of several targeted disease modifiers that ameliorate hemodynamics and quality of life. Effective risk management strategies and more aggressive treatment protocols have also allowed better outcomes for patients with PAH. For those patients who experience progressive PAH with medical therapy, lung transplantation remains a life-saving option. More recent work has been directed at developing effective treatment strategies for other forms of pulmonary hypertension, such as chronic thromboembolic pulmonary hypertension (CTEPH) and pulmonary hypertension due to other lung or heart diseases. The discovery of new disease pathways and modifiers affecting the pulmonary circulation is an ongoing area of intense investigation.

Therapeutic augmentation of NO-sGC-cGMP signalling: lessons learned from pulmonary arterial hypertension and heart failure

The nitric oxide (NO)-guanylate cyclase (GC)-cyclic guanosine monophosphate (cGMP) pathway plays an important role in cardiovascular, pulmonary and renal function. Phosphodiesterase-5 inhibitors (PDE-5i) inhibit cGMP degradation, whereas both soluble guanylate cyclase (sGC) stimulators and sGC activators directly increase sGC. PDE-5i (e.g. sildenafil, tadalafil) and sGC stimulators (e.g. riociguat, vericiguat) have been extensively used in pulmonary artery hypertension (PAH) and heart failure (HF). PDE-5i have also been used in end-stage HF before and after left ventricular (LV) assist device (LVAD) implantation. Augmentation of NO-GC-cGMP signalling with PDE-5i causes selective pulmonary vasodilation, which is highly effective in PAH but may have controversial, potentially adverse effects in HF, including pre-LVAD implant due to device unmasking of PDE-5i-induced RV dysfunction. In contrast, retrospective analyses have demonstrated that PDE-5i have beneficial effects when initiated post LVAD implant due to the improved haemodynamics of the supported LV and the pleiotropic actions of these compounds. sGC stimulators, in turn, are effective both in PAH and in HF due to their balanced pulmonary and systemic vasodilation, and as such they are preferable to PDE-5i if the use of a pulmonary vasodilator is needed in HF patients, including those listed for LVAD implantation. Regarding the effectiveness of PDE-5i and sGC stimulators when initiated post LVAD implant, these two groups of compounds should be tested in a randomized control trial.

Kcnk3 dysfunction exaggerates the development of pulmonary hypertension induced by left ventricular pressure overload

AIMS

Pulmonary hypertension (PH) is a common complication of left heart disease (LHD, Group 2 PH) leading to right ventricular (RV) failure and death. Several loss-of-function (LOF) mutations in KCNK3 were identified in pulmonary arterial hypertension (PAH, Group 1 PH). Additionally, we found that KCNK3 dysfunction is a hallmark of PAH at pulmonary vascular and RV levels. However, the role of KCNK3 in the pathobiology of PH due to LHD is unknown.

METHODS AND RESULTS

We evaluated the role of KCNK3 on PH induced by ascending aortic constriction (AAC), in WT and Kcnk3-LOF-mutated rats, by echocardiography, RV catheterization, histology analyses, and molecular biology experiments. We found that Kcnk3-LOF-mutation had no consequence on the development of left ventricular (LV) compensated concentric hypertrophy in AAC, while left atrial emptying fraction was impaired in AAC-Kcnk3-mutated rats. AAC-animals (WT and Kcnk3-mutated rats) developed PH secondary to AAC and Kcnk3-mutated rats developed more severe PH than WT. AAC-Kcnk3-mutated rats developed RV and LV fibrosis in association with an increase of Col1a1 mRNA in right ventricle and left ventricle. AAC-Kcnk3-mutated rats developed severe pulmonary vascular (pulmonary artery as well as pulmonary veins) remodelling with intense peri-vascular and peri-bronchial inflammation, perivascular oedema, alveolar wall thickening, and exaggerated lung vascular cell proliferation compared to AAC-WT-rats. Finally, in lung, right ventricle, left ventricle, and left atrium of AAC-Kcnk3-mutated rats, we found a strong increased expression of Il-6 and periostin expression and a reduction of lung Ctnnd1 mRNA (coding for p120 catenin), contributing to the exaggerated pulmonary and heart remodelling and pulmonary vascular oedema in AAC-Kcnk3-mutated rats.

CONCLUSIONS

Our results indicate that Kcnk3-LOF is a key event in the pathobiology of PH due to AAC, suggesting that Kcnk3 channel dysfunction could play a potential key role in the development of PH due to LHD.

Vanderpool R, Al Ghouleh I, Lai YC. 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.

Pulmonary Hypertension in Heart Failure

Pulmonary hypertension (PH) is traditionally defined as a mean pulmonary arterial pressure (mPAP) ≥25 mmHg. Although various factors cause PH, the most common etiology is PH due to left heart disease (PH-LHD). The underlying LHD is characterized by heart failure (HF) with reduced ejection fraction (HFrEF), HF with preserved ejection fraction (HFpEF), valvular heart disease, cardiomyopathies, or arrhythmic diseases. Regardless of its underlying cause, elevated left atrial (LA) filling pressure is a manifestation of advanced heart disease. High LA pressure then causes persistent backflow to the pulmonary veins, which increases mPAP. PH-LHD at this stage is named isolated postcapillary PH (IpcPH). Further progression of IpcPH is associated with pulmonary vasculature remodeling and hypertrophy, which consists of adding the precapillary component of PH to the pre-existing postcapillary PH. This form of PH-LHD is called combined precapillary and postcapillary PH (CpcPH). To date, therapeutic strategies for PH-LHD have been investigated in the context of HFrEF or HFpEF. Pulmonary arterial hypertension (PAH)-specific drugs have been tested in HFrEF and HFpEF populations, although encouraging results have not been demonstrated. As PAH-specific drugs target the precapillary component of PH-LHD, future studies utilizing such therapeutics in PH-LHD patients with CpcPH appear to have a more robust pathobiological basis. This article reviews the diagnosis, pathophysiology, treatment, and future direction of PH in HF.

Endothelial Dysfunction in Pulmonary Hypertension: Cause or Consequence?

Pulmonary arterial hypertension (PAH) is a rare, complex, and progressive disease that is characterized by the abnormal remodeling of the pulmonary arteries that leads to right ventricular failure and death. Although our understanding of the causes for abnormal vascular remodeling in PAH is limited, accumulating evidence indicates that endothelial cell (EC) dysfunction is one of the first triggers initiating this process. EC dysfunction leads to the activation of several cellular signalling pathways in the endothelium, resulting in the uncontrolled proliferation of ECs, pulmonary artery smooth muscle cells, and fibroblasts, and eventually leads to vascular remodelling and the occlusion of the pulmonary blood vessels. Other factors that are related to EC dysfunction in PAH are an increase in endothelial to mesenchymal transition, inflammation, apoptosis, and thrombus formation. In this review, we outline the latest advances on the role of EC dysfunction in PAH and other forms of pulmonary hypertension. We also elaborate on the molecular signals that orchestrate EC dysfunction in PAH. Understanding the role and mechanisms of EC dysfunction will unravel the therapeutic potential of targeting this process in PAH.

Persistent Pulmonary Hypertension in Corrected Valvular Heart Disease: Hemodynamic Insights and Long-Term Survival

Background The determinants and consequences of pulmonary hypertension after successfully corrected valvular heart disease remain poorly understood. We aim to clarify the hemodynamic bases and risk factors for mortality in patients with this condition. Methods and Results We analyzed long-term follow-up data of 222 patients with pulmonary hypertension and valvular heart disease successfully corrected at least 1 year before enrollment who had undergone comprehensive hemodynamic and imaging characterization as per the SIOVAC (Sildenafil for Improving Outcomes After Valvular Correction) clinical trial. Median (interquartile range) mean pulmonary pressure was 37 mm Hg (32-44 mm Hg) and pulmonary artery wedge pressure was 23 mm Hg (18-26 mm Hg). Most patients were classified either as having combined precapillary and postcapillary or isolated postcapillary pulmonary hypertension. After a median follow-up of 4.5 years, 91 deaths accounted for 4.21 higher-than-expected mortality in the age-matched population. Risk factors for mortality were male sex, older age, diabetes mellitus, World Health Organization functional class III and higher pulmonary vascular resistance-either measured by catheterization or approximated from ultrasound data. Higher pulmonary vascular resistance was related to diabetes mellitus and smaller residual aortic and mitral valve areas. In turn, the latter correlated with prosthetic nominal size. Six-month changes in the composite clinical score and in the 6-minute walk test distance were related to survival. Conclusions Persistent valvular heart disease-pulmonary hypertension is an ominous disease that is almost universally associated with elevated pulmonary artery wedge pressure. Pulmonary vascular resistance is a major determinant of mortality in this condition and is related to diabetes mellitus and the residual effective area of the corrected valve. These findings have important implications for individualizing valve correction procedures. Registration URL: https://www.clinicaltrials.gov; Unique identifier: NCT00862043.

Pulmonary arterial hypertension-associated genetic variants in combined post-capillary and pre-capillary pulmonary hypertension: a case report

Predisposing factors for the development of a pre-capillary component in pulmonary hypertension associated with left heart disease remain elusive. We report the case of a patient with persistent combined post-capillary and pre-capillary pulmonary hypertension after cardiac transplantation, in whom a rare BMPR2 variant was found.

Current Understanding of Circulating Biomarkers in Pulmonary Hypertension Due to Left Heart Disease

Pulmonary hypertension due to left heart disease (PH-LHD; Group 2), especially in the setting of heart failure with preserved ejection fraction (HFpEF), is the most frequent cause of PH. Despite its prevalence, no effective therapies for PH-LHD are available at present. This is largely due to the lack of a concise definition for hemodynamic phenotyping, existence of significant gaps in the understanding of the underlying pathology and the impact of associated comorbidities, as well as the absence of specific biomarkers that can aid in the early diagnosis and management of this challenging syndrome. Currently, B-type natriuretic peptide (BNP) and N-terminal proBNP (NT-proBNP) are guideline-recommended biomarkers for the diagnosis and prognosis of heart failure (HF) and PH. Endothelin-1 (ET-1), vascular endothelial growth factor-D (VEGF-D), and microRNA-206 have also been recently identified as new potential circulating biomarkers for patients with PH-LHD. In this review, we aim to present the current state of knowledge of circulating biomarkers that can be used to guide future research toward diagnosis, refine specific patient phenotype, and develop therapeutic approaches for PH-LHD, with a particular focus on PH-HFpEF. Potential circulating biomarkers identified in pre-clinical models of PH-LHD are also summarized here.

Cancer and pulmonary hypertension: Learning lessons and real-life interplay

This article reviews the scientific reasons that support the intriguing vision of pulmonary hypertension (PH) as a disease with a cancer-like nature and to understand whether this point of view may have fruitful consequences for the overall management of PH. This review compares cancer and PH in view of Hanahan and Weinberg’s principles (i.e., hallmarks of cancer) with an emphasis on hyperproliferative, metabolic, and immune/inflammatory aspects of the disease. In addition, this review provides a perspective on the role of transcription factors and chromatin and epigenetic aberrations, besides genetics, as “common driving mechanisms” of PH hallmarks and the foreseeable use of transcription factor/epigenome targeting as multitarget approach against the hallmarks of PH. Thus, recognition of the widespread applicability and analogy of these concepts will increasingly affect the development of new means of PH treatment.