Pathophysiology of Pulmonary Hypertension in Chronic Parenchymal Lung Disease

Review of the Diagnosis and Management of Pulmonary Hypertension Associated with Interstitial Lung Disease (ILD-PH)

Pulmonary hypertension associated with interstitial lung disease (ILD-PH) frequently complicates the course of patients with fibrotic ILD. In this narrative review, the authors assess current diagnostic tools and management considerations in ILD-PH patients. ILD-PH is associated with increased morbidity and mortality and may be suggested by the presence of symptoms out of proportion to the extent of the ILD. There are other clues to the presence of PH in the context of ILD including the need for supplemental oxygen, a reduced DLCO especially if accompanied by a disproportionately higher forced vital capacity, imaging demonstrating an enlarged pulmonary artery or a dilated right ventricle, or objective evidence of a reduced exercise capacity. While echocardiography is one screening tool, right heart catheterization remains the gold standard for the diagnosis of PH. When appropriate, treatment with inhaled treprostinil, or possibly other pulmonary vasodilators, may be indicated.

Right Heart Failure in the Intensive Care Unit: Etiology, Pathogenesis, Diagnosis, and Treatment

Right heart (RH) failure carries a high rate of morbidity and mortality. Patients who present with RH failure often exhibit complex aberrant cardio-pulmonary physiology with varying presentations. The treatment of RH failure almost always requires care and management from an intensivist. Treatment options for RH failure patients continue to evolve rapidly with multiple options available, including different pharmacotherapies and mechanical circulatory support devices that target various components of the RH circulatory system. An understanding of the normal RH circulatory physiology, treatment, and support options for the RH failure patients is necessary for all intensivists to improve outcomes. The purpose of this review is to provide clinical guidance on the diagnosis and management of RH failure within the intensive care unit setting, and to highlight the different pathophysiological manifestations of RH failure, its hemodynamics, and treatment options available at the disposal of the intensivist.

Converging Pathways: A Review of Pulmonary Hypertension in Interstitial Lung Disease

Pulmonary hypertension (PH) in interstitial lung disease (ILD) is relatively common, affecting up to 50% of patients with idiopathic pulmonary fibrosis (IPF). It occurs more frequently in advanced fibrotic ILD, although it may also complicate milder disease and carries significant clinical implications in terms of morbidity and mortality. Key pathological processes driving ILD-PH include hypoxic pulmonary vasoconstriction and pulmonary vascular remodelling. While current understanding of the complex cell signalling pathways and molecular mechanisms underlying ILD-PH remains incomplete, there is evidence for an interplay between the disease pathogenesis of fibrotic ILD and PH, with interest in the role of the pulmonary endothelium in driving pulmonary fibrogenesis more recently. This review examines key clinical trials in ILD-PH therapeutics, including recent research showing promise for the treatment of both ILD-PH and the underlying pulmonary fibrotic process, further supporting the hypothesis of interrelated pathogenesis. Other important management considerations are discussed, including the value of accurate phenotyping in ILD-PH and the success of the "pulmonary vascular" phenotype. This article highlights the close and interconnected nature of fibrotic ILD and PH disease pathogenesis, a perspective likely to improve our understanding and therapeutic approach to this complex condition in the future.

Noninvasive determinants of pulmonary hypertension in interstitial lung disease

Pulmonary hypertension (PH) in interstitial lung disease (ILD) is associated with increased mortality and impaired exertional capacity. Right heart catheterization is the diagnostic standard for PH but is invasive and not readily available. Noninvasive physiologic evaluation may predict PH in ILD. Forty-four patients with PH and ILD (PH-ILD) were compared with 22 with ILD alone (non-PH ILD). Six-min walk distance (6MWD, 223 ± 131 vs. 331 ± 125 m, p = 0.02) and diffusing capacity for carbon monoxide (DLCO, 33 ± 14% vs. 55 ± 21%, p < 0.001) were lower in patients with PH-ILD. PH-ILD patients exhibited a lower gas-exchange derived pulmonary vascular capacitance (GXCAP, 251 ± 132 vs. 465 ± 282 mL × mmHg, p < 0.0001) and extrapolated maximum oxygen uptake (VO2max) (56 ± 32% vs. 84 ± 37%, p = 0.003). Multivariate analysis was performed to determine predictors of VO2 max. GXCAP was the only variable that predicted extrapolated VO2 max among PH-ILD and non-PH ILD patients. Receiver operating characteristic curve analysis assessed the ability of individual noninvasive variables to distinguish between PH-ILD and non-PH ILD patients. GXCAP (area under the curve [AUC] 0.85 ± 0.04, p < 0.0001) and delta ETCO2 (AUC 0.84 ± 0.04, p < 0.0001) were the strongest predictors of PH-ILD. A CART analysis selected GXCAP, estimated right ventricular systolic pressure (eRVSP) by echocardiogram, and FVC/DLCO ratio as predictive variables for PH-ILD. With this analysis, the AUC improved to 0.94 (sensitivity of 0.86 and sensitivity of 0.93). Patients with a GXCAP ≤ 416 mL × mmHg had an 82% probability of PH-ILD. Patients with GXCAP ≤ 416 mL × mmHg and high FVC/DLCO ratio >1.7 had an 80% probability of PH-ILD. Patients with GXCAP ≤ 416 mL × mmHg and an elevated eRVSP by echocardiogram >43 mmHg had 100% probability of PH-ILD. The incorporation of GXCAP with either eRVSP or FVC/DLCO ratio distinguishes between PH-ILD and non-PH-ILD with high probability and may therefore assist in determining the need to proceed with a diagnostic right heart catheterization and potential initiation of pulmonary arterial hypertension-directed therapy in PH-ILD patients.

Diagnosis and management of pulmonary hypertension related to chronic respiratory disease

Pulmonary hypertension (PH) is a recognised and significant complication of chronic lung disease (CLD) and hypoxia (referred to as group 3 PH) that is associated with increased morbidity, decreased quality of life and worse survival. The prevalence and severity of group 3 PH varies within the current literature, with the majority of CLD-PH patients tending to have non-severe disease. The aetiology of this condition is multifactorial and complex, while the prevailing pathogenetic mechanisms include hypoxic vasoconstriction, parenchymal lung (and vascular bed) destruction, vascular remodelling and inflammation. Comorbidities such as left heart dysfunction and thromboembolic disease can further confound the clinical picture. Noninvasive assessment is initially undertaken in suspected cases (e.g. cardiac biomarkers, lung function, echocardiogram), while haemodynamic evaluation with right heart catheterisation remains the diagnostic gold standard. For patients with suspected severe PH, those with a pulmonary vascular phenotype or when there is uncertainty regarding further management, referral to specialist PH centres for further investigation and definitive management is mandated. No disease-specific therapy is currently available for group 3 PH and the focus of management remains optimisation of the underlying lung therapy, along with treating hypoventilation syndromes as indicated.

Comorbidity in idiopathic pulmonary fibrosis - what can biomarkers tell us?

Idiopathic pulmonary fibrosis (IPF) is characterized by progressive parenchymal scarring, leading to dyspnoea, respiratory failure and premature death. Although IPF is confined to the lungs, the importance of IPF comorbidities such as pulmonary hypertension and ischaemic heart disease, lung cancer, emphysema/chronic obstructive pulmonary disease, gastroesophageal reflux, sleep apnoea and depression has been increasingly recognized. These comorbidities may be associated with increased mortality and significant loss of quality of life, so their identification and management are vital. The development of good-quality biomarkers could lead to numerous gains in the management of these patients. Biomarkers can be used for the identification of predisposed individuals, early diagnosis, assessment of prognosis, selection of best treatment and assessment of response to treatment. However, the role of biomarkers for IPF comorbidities is still quite limited, and mostly based on evidence coming from populations without IPF. The future development of new biomarker studies could be informed by those that have been studied independently for each of these conditions. For now, clinicians should be mostly attentive to clinical manifestations of IPF comorbidities, and use validated diagnostic methods for diagnosis. As research on biomarkers of most common diseases continues, it is expected that useful biomarkers are developed for these diseases and then validated for IPF populations. The reviews of this paper are available via the supplemental material section.

Severe asthma is associated with a remodeling of the pulmonary arteries in horses

Pulmonary hypertension and cor pulmonale are complications of severe equine asthma, as a consequence of pulmonary hypoxic vasoconstriction. However, as pulmonary hypertension is only partially reversible by oxygen administration, other etiological factors are likely involved. In human chronic obstructive pulmonary disease, pulmonary artery remodeling contributes to the development of pulmonary hypertension. In rodent models, pulmonary vascular remodeling is present as a consequence of allergic airway inflammation. The present study investigated the presence of remodeling of the pulmonary arteries in severe equine asthma, its distribution throughout the lungs, and its reversibility following long-term antigen avoidance strategies and inhaled corticosteroid administration. Using histomorphometry, the total wall area of pulmonary arteries from different regions of the lungs of asthmatic horses and controls was measured. The smooth muscle mass of pulmonary arteries was also estimated on lung sections stained for α-smooth muscle actin. Reversibility of vascular changes in asthmatic horses was assessed after 1 year of antigen avoidance alone or treatment with inhaled fluticasone. Pulmonary arteries showed increased wall area in apical and caudodorsal lung regions of asthmatic horses in both exacerbation and remission. The pulmonary arteries smooth muscle mass was similarly increased. Both treatments reversed the increase in wall area. However, a trend for normalization of the vascular smooth muscle mass was observed only after treatment with antigen avoidance, but not with fluticasone. In conclusion, severe equine asthma is associated with remodeling of the pulmonary arteries consisting in an increased smooth muscle mass. The resulting narrowing of the artery lumen could enhance hypoxic vasoconstriction, contributing to pulmonary hypertension. In our study population, the antigen avoidance strategy appeared more promising than inhaled corticosteroids in controlling vascular remodeling. However, further studies are needed to support the reversibility of vascular smooth muscle mass remodeling after asthma treatment.

Healthcare utilization, medical expenditure, and mortality in Korean patients with pulmonary hypertension

Background

Limited data exists regarding healthcare utilization, medical expenses, and prognosis of pulmonary hypertension (PH) according to the World Health Organization (WHO) classification. We aimed to investigate mortality risk, healthcare utilization and medical expenditure in patients with PH across the five diagnostic subgroups.

Methods

We identified 2185 patients with PH, defined as peak tricuspid regurgitation velocity > 3.4 m/sec, among the consecutive patients referred for echocardiography between 2009 and 2015. Using diagnostic codes, medical records, and echocardiographic findings, the enrolled patients were classified according to the five subgroups by WHO classification. Healthcare utilization, costs, and all-cause mortality were assessed.

Results

Diagnostic subgroups of PH demonstrated significantly different clinical features. During a median of 32.4 months (interquartile range, 16.2–57.8), 749 patients (34.3%) died. Mortality risk was the lowest in group II (left heart disease) and highest in group III (chronic lung disease). The etiologies of pulmonary arterial hypertension (PAH) had significant influence on the mortality risk in group I, showing the worst prognosis in PAH associated with connective tissue disease. Medical expenditure and healthcare utilization were different between the PH subgroups: groups II and V had more hospitalizations and medical expenses than other groups. Regardless of PH subgroups, the severity of PH was associated with higher mortality risk, more healthcare utilization and medical expenditure.

Conclusions

Significant differences in clinical features and prognostic profiles between PH subgroups reflect the differences in pathophysiology and clinical consequences. Our findings highlight the importance of comprehensive understanding of PH according to the etiology and its severity.

Pulmonary hypertension due to interstitial lung disease

PURPOSE OF REVIEW

Pulmonary hypertension has been reported to complicate the course of a number of fibrotic lung diseases, including idiopathic pulmonary fibrosis, chronic hypersensitivity pneumonitis and nonspecific interstitial pneumonitis. Most commonly, mild elevations in the mean pulmonary artery pressure are seen in patients with advanced pulmonary fibrosis. However, some patients may develop severe pulmonary hypertension, which appears out of proportion to the degree of their restrictive lung disease.

RECENT FINDINGS

The benefits of pulmonary vasodilator therapy have yet to be established in pulmonary hypertension complicating fibrotic lung disease. In fact, one recent clinical trial examining riociguat in patients with pulmonary hypertension complicating idiopathic interstitial pneumonias was terminated early for an increased risk of death or hospitalization. Multiple clinical trials on this topic are currently ongoing, including studies examining inhaled pulmonary vasodilator therapies.

SUMMARY

The development of pulmonary hypertension is associated with increased exertional oxygen requirements, worsened functional capacity and attenuated life expectancy. It is hoped that continued research will find an effective therapy for this condition, which will improve quality of life and extend life expectancy in patients with this condition.

Multimodal noninvasive prediction of pulmonary hypertension in IPF

INTRODUCTION AND OBJECTIVE

Pulmonary hypertension (PH) complicating idiopathic pulmonary fibrosis (IPF) is challenging to diagnose given inaccuracy of transthoracic echocardiogram (TTE) measurements. However, it has significant prognostic implications and is therefore important to accurately identify.

METHODS

We conducted a cross-sectional study of patients with IPF who underwent RHC as part of their evaluation. A variety of commonly available noninvasive variables were evaluated for their ability to predict pulmonary arterial pressure in a linear regression model, including the traditionally used right ventricular systolic pressure (RVSP) estimated from TTE.

RESULTS

There were 105 eligible patients identified from January 2006 to July 2016. The average age was 62.7 ± 7.7 years, 35 had RHC proven PH and 43% ultimately underwent lung transplantation. A linear model including three terms: RVSP (ANOVA P < .01), the ratio of FVC/DLCO from PFTs (P = .05) and pulmonary artery to aorta diameter ratio from CT (P < .01) was found to predict the mean pulmonary artery pressure more reliably than RVSP alone (R² .39 vs .29, P < .05), with a lower rate of incorrect classification of PH status in these individuals (27.6 vs 35.2%, P = .05) and high negative predictive value (87.2%).

CONCLUSION

If used in conjunction with RVSP from TTE, parameters from PFTs and the CT scan more accurately predict the presence or absence of PH than any of the variables in isolation. Using these in concert may allow greater discrimination in deciding which patients to subject to diagnostic right heart catheterization.

Outcomes of lung disease-associated pulmonary hypertension and impact of elevated pulmonary vascular resistance

BACKGROUND

The clinical characteristics, hemodynamic changes and outcomes of lung disease-associated pulmonary hypertension (LD-PH) are poorly defined.

METHODS

A prospective cohort of PH patients undergoing initial hemodynamic assessment was collected, from which 51 patients with LD-PH were identified. Baseline characteristics and long-term survival were compared with 83 patients with idiopathic pulmonary arterial hypertension (iPAH).

RESULTS

Mean age (±standard deviation) of LD-PH patients was 64 ± 10 years, 30% were female and 78% were New York Heart Association class III-IV. The LD-PH group was older than the iPAH group (64 ± 10 vs 56 ± 18 years, respectively, P = 0.003) with a lower percentage of women (30% vs 70%, P = 0.007). LD-PH patients had smaller right ventricular sizes (P = 0.02) and less tricuspid regurgitation (P = 0.03) by echocardiogram, and lower mean pulmonary arterial pressures (mPAP) (P = 0.01) and pulmonary vascular resistance (PVR) (P = 0.001) at catheterization. Despite these findings, mortality was equally high in both groups (P = 0.16). 5-year survival was lower in patients with interstitial lung disease compared to those with obstructive pulmonary disease (P = 0.05). Among the LD-PH population, those with mild to moderately elevated mPAP and those with PVR <7 Wood units demonstrated significantly improved survival (P = 0.04 and P = 0.001, respectively). Vasoreactivity was not associated with improved survival (P = 0.64). A PVR ≥7 Wood units was associated with increased risk of mortality (hazard ratio (95% confidence interval), 3.59 (1.27-10.19), P = 0.02).

CONCLUSIONS

Despite less severe PH and less right heart sequelae, LD-PH has an equally poor clinical outcome when compared to iPAH. A PVR ≥7 Wood units in LD-PH patients was associated with 3-fold higher mortality.

Hypertension, diabetes, atherosclerosis and NASH: Cause or consequence?

Non-alcoholic fatty liver disease (NAFLD) has become one of the most common forms of chronic liver disease worldwide and its prevalence is expected to continue rising. NAFLD has traditionally been considered a consequence of metabolic syndrome (MetS). However, the link between NAFLD and MetS components, especially type 2 diabetes mellitus (T2DM), hypertension (HTN), and cardiovascular disease (CVD) is more complex than previously thought. Indeed, the adverse effects of NAFLD extend far beyond the liver, with a large body of clinical evidence now suggesting that NAFLD may precede and/or promote the development of T2DM, HTN and atherosclerosis/CVD. The risk of developing these cardiometabolic diseases parallels the underlying severity of NAFLD. Accumulating evidence suggests that the presence and severity of NAFLD is associated with an increased risk of incident T2DM and HTN. Moreover, long-term prospective studies indicate that the presence and severity of NAFLD independently predicts fatal and nonfatal CVD events. In this review, we critically discuss the rapidly expanding body of clinical evidence that supports the existence of a bi-directional relationship between NAFLD and various components of MetS, particularly T2DM and HTN, as well as the current knowledge regarding a strong association between NAFLD and CVD morbidity and mortality. Finally, we discuss the most updated putative biological mechanisms through which NAFLD may contribute to the development of HTN, T2DM and CVD.

Pulmonary Hypertension Associated with Pulmonary Veno-occlusive Disease in Patients with Polycythemia Vera

A 65-year-old man was diagnosed with polycythemia vera (PV) and treated with hydroxyurea. Three years later, he was admitted to our institution for severe hypoxia. Right heart catheterization revealed that the patient had pulmonary hypertension (PH). In addition, radiographic findings and resistance to pulmonary vasodilators led to the diagnosis of PH associated with pulmonary veno-occlusive disease. The administration of ruxolitinib improved his hematopoiesis and respiratory failure. While the disease is relatively common in Europe and the United States, limited data exist regarding myeloproliferative neoplasm complicated with PH in Japan. PH should be considered a potential complication and screened during the clinical care of patients with myeloproliferative neoplasms.

Idiopathic pulmonary fibrosis: Clinical behavior and aging associated comorbidities

Idiopathic pulmonary fibrosis (IPF) is a progressive, irreversible and usually lethal lung disease of unknown etiology. Once considered as a relatively homogeneous, slowly progressive disease, is now recognized that the clinical behavior shows substantial heterogeneity, including an accelerated variant, and the presence of acute exacerbations. In addition, since IPF largely affects individuals over 60 years of age, the patients are at increased risk of several comorbidities that in turn have a remarkable clinical impact on the disease and increases mortality rate. Among others, combined pulmonary fibrosis and emphysema, secondary pulmonary arterial hypertension, lung cancer, and cardiovascular diseases are frequently associated with IPF and impact survival. For these reasons clinical phenotypes and comorbidities should be timely identified and managed. The aim of this review is to describe the common pulmonary and extra-pulmonary comorbidities in IPF, as well as the putative mechanisms involved.

The NLRP3 inflammasome in pathogenic particle and fibre-associated lung inflammation and diseases

The concept of the inflammasome, a macromolecular complex sensing cell stress or danger signals and initiating inflammation, was first introduced approximately a decade ago. Priming and activation of these intracellular protein platforms trigger the maturation of pro-inflammatory chemokines and cytokines, most notably, interleukin-1β (IL-1β) and IL-18, to promulgate innate immune defenses. Although classically studied in models of gout, Type II diabetes, Alzheimer's disease, and multiple sclerosis, the importance and mechanisms of action of inflammasome priming and activation have recently been elucidated in cells of the respiratory tract where they modulate the responses to a number of inhaled pathogenic particles and fibres. Most notably, inflammasome activation appears to regulate the balance between tissue repair and inflammation after inhalation of pathogenic pollutants such as asbestos, crystalline silica (CS), and airborne particulate matter (PM). Different types of fibres and particles may have distinct mechanisms of inflammasome interaction and outcome. This review summarizes the structure and function of inflammasomes, the interplay between various chemokines and cytokines and cell types of the lung and pleura after inflammasome activation, and the events leading to the development of non-malignant (allergic airway disease and chronic obstructive pulmonary disease (COPD), asbestosis, silicosis) and malignant (mesothelioma, lung cancer) diseases by pathogenic particulates. In addition, it emphasizes the importance of communication between cells of the immune system, target cells of these diseases, and components of the extracellular matrix (ECM) in regulation of inflammasome-mediated events.

Transforming growth factor beta 1 induced endothelin-1 release is peroxisome proliferator-activated receptor gamma dependent in A549 cells

Background

Endothelin-1 (ET-1) is involved in pulmonary vascular remodeling. The aim of this study was to investigate the biochemical interactions between PPAR-γ, TGF-β1 and ET-1 in vitro.

Methods

A549 cells were pre-treated with S2505 (10 μM), S2871 (10 μM) with/without SB203580 (10 μM) for 60 min following 2 h treatment with 10 ng/mL TGF-β1. A549 cells were also transfected with positive or negative PPAR-γ plasmids for comparison. RT-PCR, ELISA, western blotting and confocal laser scanning microscopy (CLSM) were used to measure the relevant expression of mRNA, protein, mediators of pathways and nuclear factor translocation.

Results

SB203580 inhibited TGF-β1 induced ET-1 expression in A549 cells. S2871 decreased PPAR-γ mRNA and increase TGF-β1-induced ET-1 expression. S2871 increased phosphorylation of p38 MAPK and Smad2. Cells transfected with PPAR-γ negative plasmid increased TGF-β1 induced ET-1 expression, and increased the expression of phospho-p38 MAPK and phospho-Smad2. S2505 increased PPAR-γ mRNA expression, suppressed the increased TGF-β1-induced expression of ET-1. S2505 inhibited TGF-β1 induced phosphorylation of p38 MAPK and Smad2, also the nuclear translocation of Smad2. Cells transfected with PPAR-γ positive plasmid reduced TGF-β1-induced ET-1 expression, and inhibited the expression of phospho-p38 MAPK and phospho-Smad2.

Conclusions

TGF-β1 induced release of endothelin-1 is PPAR-γ dependent in cultured A549 cells.