Pulmonary microvascular permeability. Responses to high vascular pressure after induction of pacing-induced heart failure in dogs

Transcriptional signatures of endothelial cells shape immune responses in cardiopulmonary health and disease

The cardiopulmonary vasculature and its associated endothelial cells (ECs) play an essential role in sustaining life by ensuring the delivery of oxygen and nutrients. Beyond these foundational functions, ECs serve as key regulators of immune responses. Recent advances in single-cell RNA sequencing have revealed that the cardiopulmonary vasculature is composed of diverse EC subpopulations, some of which exhibit specialized immunomodulatory properties. Evidence for immunomodulation includes distinct expression profiles associated with antigen presentation, cytokine secretion, immune cell recruitment, translocation, and clearance - functions critical for maintaining homeostasis in the heart and lungs. In cardiopulmonary diseases, ECs undergo substantial transcriptional reprogramming, leading to a shift from homeostasis to an activated state marked by heightened immunomodulatory activity. This transformation has highlighted the critical role for ECs in disease pathogenesis and their potential as future therapy targets. This Review emphasizes the diverse functions of ECs in the heart and lungs, particularly adaptive and maladaptive immunoregulatory roles in cardiopulmonary health and disease.

Epidemiology and Prognostic Significance of Acute Noncardiac Organ Dysfunction Across Cardiogenic Shock Subtypes

BACKGROUND

The epidemiology and prognostic significance of acute noncardiac organ dysfunction across cardiogenic shock (CS) subtypes are not well-defined.

METHODS

CS admissions from 2017 to 2022 in the Critical Care Cardiology Trials Network Registry were classified as acute myocardial infarction-related CS (AMI-CS), acute-on-chronic heart failure-related CS (AoC HF-CS), or de novo HF-CS, and categorized as having at least moderate respiratory, kidney, liver, and/or neurological dysfunction using established criteria. Burden of organ dysfunction was defined as no noncardiac organ dysfunction (NOD), single organ dysfunction, or multiorgan dysfunction (≥2) (MOD). Multivariable models were used to evaluate associations of burden and type of noncardiac organ dysfunction with in-hospital death.

RESULTS

Among 3904 CS admissions, 29.4% had AMI-CS, 50.9% had AoC HF-CS, and 19.7% had de novo HF-CS. AMI-CS and de novo HF-CS had greater prevalence of MOD (35.0% and 33.9%, respectively) compared with AoC HF-CS (23.1%; P < .01). In-hospital mortality was higher with a greater burden of organ dysfunction in the overall CS cohort (single organ dysfunction vs NOD, adjusted odds ratio [aOR] for in-hospital death 2.5, 95% confidence interval [CI] 2.0-3.2; MOD vs NOD: aOR 6.5, 95% CI 5.1-8.2) and across each CS subtype. Kidney dysfunction was the most prognostically important form of organ dysfunction in the overall cohort (aOR 4.1, 95% CI 3.4-5.0) and for each CS subtype.

CONCLUSIONS

Admissions for AoC HF-CS had a lower burden of acute noncardiac organ dysfunction compared with admissions for de novo HF-CS and AMI-CS. However, acute noncardiac organ dysfunction burden was similarly adversely prognostic across all CS subtypes.

Novel insights into the pathobiology of pulmonary hypertension in heart failure with preserved ejection fraction

Heart failure (HF) with preserved ejection fraction (HFpEF) is the most common cause of pulmonary hypertension (PH) worldwide and is strongly associated with adverse clinical outcomes. The American Heart Association recently highlighted a call to action regarding the distinct lack of evidence-based treatments for PH due to poorly understood pathophysiology of PH attributable to HFpEF (PH-HFpEF). Prior studies have described cardiophysiological mechanisms to explain the development of isolated postcapillary PH (ipc-PH); however, the consequent increase in pulmonary vascular (PV) resistance (PVR) may lead to the less understood and more fatal combined pre- and postcapillary PH (cpc-PH). Metabolic disease and inflammatory dysregulation have been suggested to predispose PH, yet the molecular mechanisms are unknown. Although PH-HFpEF has been studied to partly share vasoactive neurohormonal mediators with primary pulmonary arterial hypertension (PAH), clinical trials that have targeted these pathways have been unsuccessful. The increased mortality of patients with PH-HFpEF necessitates further study into viable mechanistic targets involved in disease progression. We aim to summarize the current pathophysiological and clinical understanding of PH-HFpEF, highlight the role of known molecular mechanisms in the progression of PV disease, and introduce a novel concept that lipid metabolism may be attenuating and propagating PH-HFpEF.NEW & NOTEWORTHY Our review addresses pulmonary hypertension (PH) attributable to heart failure (HF) with preserved ejection fraction (HFpEF; PH-HFpEF). Current knowledge gaps in PH-HFpEF pathophysiology have led to a lack of therapeutic targets. Thus, we address identified knowledge gaps in a comprehensive review, focusing on current clinical epidemiology, known pathophysiology, and previously studied molecular mechanisms. We also introduce a comprehensive review of polyunsaturated fatty acid (PUFA) lipid inflammatory mediators in PH-HFpEF.

Monocyte chemotactic protein (MCP)-1 (CCL2) and its receptor (CCR2) are elevated in chronic heart failure facilitating lung monocyte infiltration and differentiation which may contribute to lung fibrosis

BACKGROUND

Dyspnea, the cardinal manifestation of chronic heart failure (CHF), may reflect both pulmonary oedema and pulmonary remodeling resulting in tissue stiffening. Emerging evidence suggests that predominance of distinct phenotypes of alveolar and recruited macrophages, designated M1 and M2, may regulate the course of inflammatory tissue repair and remodeling in the lung.

METHODS

In a CHF rat model, we found fibrotic reinforcement of the extracellular matrix with an increase in monocyte chemotactic protein (MCP)-1/CCL2 in bronchoalveolar lavage (BAL), corresponding to a 3-fold increase in recruited macrophages. In this clinical cross sectional study, we aimed to examine potential mediators of leukocyte activation and lung infiltration in parallel BAL and blood from CHF patients compared to non-CHF controls.

RESULTS

Mini-BAL and peripheral blood samples were obtained from hospitalized CHF, acute decompensated CHF and non-CHF patients. CHF patients and decompensated CHF patients demonstrated increases from non-CHF patients in BAL MCP-1, as well as the M2 macrophage cytokines interleukin-10 and transforming growth factor-β. BAL and plasma MCP-1 were significantly correlated; however, MCP-1 was 20-fold higher in epithelial lining fluid in BAL, indicative of an alveolar chemotactic gradient. An increase in transglutaminase 2 positive M2 macrophages in parallel with a decrease in the MCP-1 receptor, CC chemokine receptor 2 (CCR2), was apparent in BAL cells of CHF patients compared to non-CHF.

CONCLUSION

These data suggest a pathway of MCP-1 mediated M2 macrophage prevalence in the lungs of CHF patients which may contribute to pulmonary fibrotic remodeling and consequent increased severity of dyspnea.

Ten conditions where lung ultrasonography may fail: limits, pitfalls and lessons learned from a computer-aided algorithmic approach

Lung ultrasonography provides relevant information on morphological and functional changes occurring in the lungs. However, it correlates weakly with pulmonary congestion and extra vascular lung water. Moreover, there is lack of consensus on scoring systems and acquisition protocols. The automation of this technique may provide promising easy-to-use clinical tools to reduce inter- and intra-observer variability and to standardize scores, allowing faster data collection without increased costs and patients risks.

Pulmonary artery pressure response to percutaneous mitral valvuloplasty: Associated factors and clinical implications

BACKGROUND

Pulmonary hypertension (PH) is a marker of poor outcome in mitral stenosis (MS), which improves after percutaneous mitral valvuloplasty (PMV). However, mechanical interventions for relief of valve obstruction often but not always reduce pulmonary pressures. This study aimed to assess the parameters associated with abnormal pulmonary artery pressure (PAP) response immediately after a successful PMV, and also its impact on long-term outcome.

METHODS

A total of 181 patients undergoing PMV for rheumatic MS were prospectively enrolled. Invasive hemodynamic and echocardiographic measures were examined in all patients. Abnormal PAP response was defined as the mean PAP (mPAP) values unchanged at the end of the procedure. Long-term outcome was a composite endpoint of death, mitral valve replacement, repeat PMV, new onset of atrial fibrillation (AF), or stroke.

RESULTS

The mean age was 44.1 ± 12.6 years, and 157 patients were women (86.7%). In the overall population, mPAP decreased from 33.4 ± 13.1 mmHg pre to 27.6 ± 9.8 mmHg post (p < 0.001). Following PMV, 52 patients (28.7%) did not have any reduction of mPAP immediately after the PMV. Multivariable analysis adjusting for baseline values of PAP and mitral valve area revealed that AF (Odds ratio [OR] 2.7, 95% [confidence interval] CI 1.3 to 6.7), maximum mitral valve leaflets displacement (OR 0.8, 95% CI 0.7 to 0.9), and post-procedural left ventricular compliance (OR 0.7, 95% CI 0.5 to 0.9) were predictors of a lack of improvement in mPAP. During a median follow-up of 4.4 years, the endpoint was reached in 56 patients (31%). The pulmonary pressure response to PMV was not an independent predictor of long-term events.

CONCLUSIONS

In patients with MS undergoing PMV, pulmonary pressures may not reduce immediately after the procedure, despite adequate opening of the valve. Abnormal PAP response can be predicted from baseline clinical and valvular characteristics as well as post-procedural left ventricular compliance. The lack of any immediate reduction in mPAP is not associated with long-term adverse outcomes.

Association of lung diffusion capacity with cardiac remodeling and risk of heart failure: The Framingham heart study

Background

Lung function abnormalities are ubiquitous in heart failure (HF). It is unclear, however, if abnormal lung diffusion capacity is associated with cardiac remodeling and antedates HF. We hypothesized that lower lung diffusion capacity for carbon monoxide (DLCO) is associated with worse left ventricular (LV) systolic and diastolic function cross-sectionally, and with higher risk of HF prospectively.

Methods

We evaluated 2423 Framingham Study participants (mean age 66 years, 55% women) free of HF who underwent routine echocardiography and pulmonary function tests. We used multivariable regression models to relate DLCO, forced vital capacity (FVC), and forced expiratory volume in 1 second (FEV1) to left ventricular ejection fraction (LVEF), left atrial (LA) emptying fraction (LAEF), E/e’, E/A, LV mass, and LA diameter (LAD). Multivariable-adjusted Cox proportional hazards regression was used to relate DLCO, FEV1, and FVC to incident HF.

Results

In multivariable-adjusted cross-sectional analyses, DLCO, FEV1, and FVC (dependent variables) were associated positively with LVEF (β_DLCO = 0.208, β_FEV1 = 0.021, and β_FVC = 0.025 per 5% increment in LVEF; p<0.005 for all), and LAEF (β_DLCO = 0.707, β_FEV1 = 0.058 and β_FVC = 0.058 per 5% increment in LAEF; p<0.002 for all). DLCO and FVC were inversely related to E/A (β_DLCO = -0.289, β_FVC = -0.047 per SD increment in E/A; p<0.001 for all). Additionally, DLCO, FEV1 and FVC were inversely related to HF risk (108 events, median follow-up 9.7 years; multivariable-adjusted hazard ratios per SD increment 0.90, 95% CI 0.86–0.95; 0.42, 95% CI 0.28–0.65, and 0.51, 95% CI 0.36–0.73, respectively). These results remained robust in analyses restricted to non-smokers.

Conclusions

Our large community-based observations are consistent with the concept that lower lung diffusion capacity and expiratory flow rates are associated with cardiac remodeling and may antedate HF. Additional studies are needed to confirm our findings and to evaluate the prognostic utility of pulmonary function testing for predicting HF.

The haemodynamic basis of lung congestion during exercise in heart failure with preserved ejection fraction

AIMS

Increases in extravascular lung water (EVLW) during exercise contribute to symptoms, morbidity, and mortality in patients with heart failure and preserved ejection fraction (HFpEF), but the mechanisms leading to pulmonary congestion during exercise are not well-understood.

METHODS AND RESULTS

Compensated, ambulatory patients with HFpEF (n = 61) underwent invasive haemodynamic exercise testing using high-fidelity micromanometers with simultaneous lung ultrasound, echocardiography, and expired gas analysis at rest and during submaximal exercise. The presence or absence of EVLW was determined by lung ultrasound to evaluate for sonographic B-line artefacts. An increase in EVLW during exercise was observed in 33 patients (HFpEFLW+, 54%), while 28 (46%) did not develop EVLW (HFpEFLW-). Resting left ventricular function was similar in the groups, but right ventricular (RV) dysfunction was two-fold more common in HFpEFLW+ (64 vs. 31%), with lower RV systolic velocity and RV fractional area change. As compared to HFpEFLW-, the HFpEFLW+ group displayed higher pulmonary capillary wedge pressure (PCWP), higher pulmonary artery (PA) pressures, worse RV-PA coupling, and higher right atrial (RA) pressures during exercise, with increased haemoconcentration indicating greater loss of water from the vascular space. The development of lung congestion during exercise was significantly associated with elevations in PCWP and RA pressure as well as impairments in RV-PA coupling (area under the curve values 0.76-0.84).

CONCLUSION

Over half of stable outpatients with HFpEF develop increases in interstitial lung water, even during submaximal exercise. The acute development of lung congestion is correlated with increases in pulmonary capillary hydrostatic pressure that favours fluid filtration, and systemic venous hypertension due to altered RV-PA coupling, which may interfere with fluid clearance.

CLINICAL TRIAL REGISTRATION

NCT02885636.

Multimodality imaging in chronic heart failure

The prevalence of heart failure (HF) is approximately 1-2% of the adult population in developed countries, rising to  ≥ 10% among people over 70. The common symptoms of HF include shortness of breath, ankle swelling and fatigue, determined by a reduced cardiac output. Multimodality imaging is crucial to define HF etiology, determine prognosis and guiding tailored treatments. Echocardiography is the most widely used imaging modality and maintains a pivotal role in the initial diagnostic work-up and in the follow-up of HF patients. Cardiac magnetic resonance (CMR) may support the morpho-functional assessment provided by echocardiography when the acoustic window is limited or a gold standard evaluation is required. Furthermore, CMR is frequently used due to the unmatched capability to characterize myocardial structure. Coronary computed tomography angiography has become the non-invasive imaging of choice to diagnose or rule-out coronary artery disease, acquiring remarkable importance in the management of HF patients. Moreover, emerging capabilities of CT-based tissue characterization may be useful, especially when CMR is contraindicated. Finally, chest CT may contribute to precisely define the framework of HF patients, revealing new insight about cardiopulmonary pathophysiological interactions with potential high prognostic value.

Systemic Markers of Monocyte Activation in Acute Pulmonary Oedema

BACKGROUND

Hydrostatic lung injury followed by pulmonary remodelling variably complicates cardiogenic acute pulmonary oedema (APO). Pulmonary remodelling may be regulated by the balance between distinct phenotypes of pulmonary macrophages; activated/inflammatory (M1), and reparative/anti-inflammatory (M2), derived from circulating monocyte populations. The aim of this study was to identify biomarkers in peripheral blood that are consistent with hydrostatic lung injury and pulmonary remodelling in APO and which follow the variable clinical course.

METHODS

To examine peripheral markers of lung inflammation, resolution and remodelling, 18 patients, admitted to the intensive care unit (ICU) with a clinical diagnosis of APO, were enrolled. Admission, 12- and 24-hour post-admission bloods were assayed for cytokines by ELISA (R&D Systems, Minneapolis, MN, USA) and leukocyte surface markers by flow cytometry.

RESULTS

Admission PaO₂ to FiO₂ ratio was positively correlated with Mon 2 (intermediate) monocyte prevalence, through increasing ratio of CD16⁺ monocytes to CD11b⁺ and CD40⁺ monocytes, and negatively correlated with Mon 1 (classical) monocyte prevalence, through decreasing ratio of CD16⁺ monocytes to CD62L⁺. Secondary cohort analysis compared 10 APO patients with established chronic heart failure (CHF) to eight without CHF. An increase in monocyte chemotactic peptide (MCP)-1, monocyte prevalence, and CD16^-CD62L⁺ monocytes with CHF, all characteristic of monocyte activation to a Mon 1 phenotype, were found in the CHF APO patients.

CONCLUSIONS

Increased systemic monocyte prevalence and expression of cell surface markers suggest a Mon 1 profile in CHF patients during episodes of APO. Future studies should define the role of systemic monocyte prevalence and activation in decompensated CHF.

Relationship Between Noninvasive Assessment of Lung Fluid Volume and Invasively Measured Cardiac Hemodynamics

Background

Right heart catheterization is the gold standard in clinical practice for the assessment of cardiovascular hemodynamics, but it is an invasive procedure requiring expertise in both insertion and reading. Remote dielectric sensing (ReDS) is a noninvasive electromagnetic‐based technology intended to quantify lung fluid content.

Methods and Results

In this prospective single‐center study, ReDS readings were obtained in supine position just before right heart catheterization procedure in patients with heart failure. Agreement between ReDS and pulmonary artery wedge pressure (PAWP) was analyzed. Of all, 139 patients with heart failure received hemodynamic assessment and ReDS measurement. A good correlation was found between ReDS and PAWP measurement (r=0.492, P<0.001). Receiver operating characteristic analysis of the ability to identify a PAWP ≥18 mm Hg resulted in a ReDS cutoff value of 34%, with an area under the curve of 0.848, a sensitivity of 90.7%, and a specificity of 77.1%. Overall, ReDS <34% carries a high negative predictive value of 94.9%.

Conclusions

Lung fluid content, as measured by ReDS, correlates well with PAWP. The high sensitivity and specificity and especially the high negative predictive value make ReDS a reliable noninvasive tool at the point of care, to rule out elevated PAWP in patients with heart failure and to help with medical management of patients with heart failure. Further studies are warranted to compare this tool with existing tests and to relate the findings to the clinical outcomes.

Challenges in pulmonary hypertension associated with left heart disease

Introduction: Pulmonary hypertension (PH) secondary to left-sided heart disease (Group 2 PH) is a frequent complication of heart failure (HF) and is a heterogeneous phenotypic disorder that worsens exercise capacity, increases risk for hospitalization and survival independent of left ventricular ejection fraction (LVEF) or stage of HF. Areas covered: In this review, an update of the current knowledge and some potential challenges about the pathophysiology and treatments of group 2 PH in patients with HF of either preserved or reduced ejection fraction are provided. Also, this review discusses the epidemiology and provides hints for the optimal evaluation and diagnosis of these patients to prevent misclassification of their pulmonary hypertension. Expert opinion: There are many of areas lacking knowledge and understanding in the field of pulmonary hypertension associated to left heart disease (PH-LHD) that should be addressed in the future. Further research should be performed, in terms of pathobiology, and understanding the predisposition (genetic susceptibility and contributing factors) of the different phenotypes of this disorder. More clinical trials targeting new therapeutic options and specific PH therapies are warranted to help this increasing important patient group as the current guidelines recommend to only treat the underlying left-sided heart disease.

Bao Yuan decoction and Tao Hong Si Wu decoction improve lung structural remodeling in a rat model of myocardial infarction: Possible involvement of suppression of inflammation and fibrosis and regulation of the TGF-β1/Smad3 and NF-κB pathways

Chronic heart failure (CHF) leads to pulmonary structural remodeling, which may be a key factor for poor clinical outcomes in patients with end-stage heart failure, and few effective therapeutic options are presently available. The aim of the current study was to explore the mechanism of action and pulmonary-protective effects of treatment with Bao Yuan decoction combined with Tao Hong Si Wu decoction (BYTH) on lung structural remodeling in rats with ischemic heart failure. In a model of myocardial infarction (MI) induced by ligation of the left anterior descending (LAD) artery, rats were treated with BYTH. Heart function and morphometry were measured followed by echocardiography, histological staining, and immunohistochemical analysis of lung sections. The levels of transforming growth factor-β1 (TGF-β1), type I collagen, phosphorylated-Smad3 (p-Smad3), tumor necrosis factor-α (TNF-α), toll-like receptor 4 (TLR4), active nuclear factor κB (NF-κB) and alpha smooth muscle actin (α-SMA) were detected using Western blotting. Lung weight increased after an infarct with no evidence of pulmonary edema and returned to normal as a result of BYTH. In addition, BYTH treatment reduced levels of type I collagen, TGF-β1, and α-SMA expression and decreased the phosphorylation of Smad3 in the lungs of rats after MI. BYTH treatment also reduced the elevated levels of lung inflammatory mediators such as TNF-α, TLR4, and NF-κB. Results suggested that BYTH could effectively improve lung structural remodeling after MI because of its anti-inflammatory and anti-fibrotic action, which may be mediated by suppression of the TGF-β1/Smad3 and NF-κB signaling pathways.

Preliminary evidence that hydrostatic edema may contribute to the formation of diffuse alveolar damage in a Holstein calf model

Background: Two notable findings of clinically healthy feedlot cattle suggest they may have pulmonary hydrostatic edema during the finishing phase of production: increased pulmonary arterial wedge pressures and pulmonary venous hypertrophy. The goal of this study was to determine if increased pulmonary arterial wedge pressure (PAWP) in a Holstein calf could lead to diffuse alveolar damage consistent with the early, exudative phase of acute interstitial pneumonia of feedlot cattle.

Methods: Six male Holstein dairy calves were given daily subcutaneous injections of the nonspecific ß-adrenergic agonist isoprenaline (10 mg/kg/d), to induce left ventricular diastolic dysfunction, or sterile water for 14 days. On Day 14, pulmonary arterial pressures and wedge pressures were measured, echocardiography performed, and the ratio of mitral valve flow velocity (E) to septal lengthening velocity (e’) calculated. Calves were euthanized on Day 15 and lung lesions semi-quantitatively scored.

Results: Mean PAWP was 12 ± 1 mm Hg in calves that received isoprenaline and 7 ± 1 mm Hg in controls ( P = 0.01). Calves that received isoprenaline tended to have greater relative wall thickness than control calves ( P = 0.15) and greater E/e’ ratios ( P = 0.16), suggestive of concentric hypertrophy and diastolic dysfunction, respectively. Calves that received isoprenaline also tended to have a left ventricle and interventricular septum that was 29 ± 10 g heavier than control calves ( P = 0.10) when controlling for body mass. Hyaline membranes, the hallmark feature of diffuse alveolar damage, were evident in lung sections from all calves that received isoprenaline but none of the controls.

Conclusions: Consistent with prior pathological and physiological studies of feedlot cattle, this study provides preliminary evidence that cattle presenting with clinical signs and pathology consistent with early stage acute interstitial pneumonia could be attributable to hydrostatic edema associated with left ventricular failure.

Wedge Pressure Rather Than Left Ventricular End-Diastolic Pressure Predicts Outcome in Heart Failure With Preserved Ejection Fraction

OBJECTIVES

This study sought to compare the prognostic power of left ventricular end-diastolic pressure (LVEDP) and pulmonary arterial wedge pressure (PAWP) in heart failure with preserved ejection fraction (HFpEF).

BACKGROUND

It is broadly accepted that direct measurement of LVEDP in HFpEF more robustly reflects left ventricular hemodynamics than PAWP.

METHODS

A total of 173 consecutive HFpEF patients were prospectively enrolled. Of these, 152 patients fulfilled registry inclusion criteria. Study participants underwent clinical evaluation, lung function tests, echocardiography, cardiac magnetic resonance, coronary angiography, and invasive hemodynamic assessments with PAWP and LVEDP measurements in 1 procedure. The study endpoint was defined as hospitalization for heart failure or cardiac death.

RESULTS

A modest pressure difference (2.0 ± 4.4 mm Hg) was observed between PAWP (21.5 ± 5.6 mm Hg) and LVEDP (19.5 ± 5.2 mm Hg) at baseline. After a mean follow-up of 23.5 ± 21.3 months, PAWP was predictive of outcome (p = 0.010), whereas LVEDP was not (p = 0.261) by Kaplan-Meier curves. By multivariate regression analysis, diffusion capacity of carbon monoxide (DLCO) was the only parameter that was independently related to the pressure difference between PAWP and LVEDP. When patients were stratified according to DLCO between ≤45% and >45%, those in the low DLCO group were found to have a more pronounced pressure drop between PAWP and LVEDP (3.1 ± 4.8 mm Hg vs. 0.8 ± 3.8 mm Hg, respectively; p = 0.031) and to be in more advanced disease stages.

CONCLUSIONS

Our data indicate that PAWP but not LVEDP is associated with outcome in HFpEF. A more pronounced difference between PAWP and LVEDP and more advanced disease is found in patients with low DLCO.

Implication of pulmonary hypertension in patients undergoing MitraClip therapy: results from the German transcatheter mitral valve interventions (TRAMI) registry

AIMS

We sought to evaluate the impact of pulmonary hypertension on outcomes following MitraClip therapy.

METHODS AND RESULTS

The 643 patients in the TRAnscatheter Mitral valve Interventions (TRAMI) registry were divided into three groups according to echocardiographically graded systolic pulmonary artery pressure (sPAP) (Group 1: patients with sPAP of ≤36 mmHg; Group 2: patients with sPAP of 37-50 mmHg; Group 3: patients with sPAP of >50 mmHg) and followed for 1 year. Recent cardiac decompensation, aortic valve disease and tricuspid valve insufficiency were observed more frequently in patients with higher sPAP. Furthermore, logEuroSCORE, Society of Thoracic Surgeons score and age were higher with rising sPAP values. No differences were observed in mitral regurgitation (MR) severity, co-morbidities or clinical findings (New York Heart Association class, 6-min walking distance). Reduction to MR of grade 1 or lower was achieved more often in patients with lower sPAP levels (P = 0.01). In Groups 2 and 3, sPAP was reduced significantly. Major adverse cardiac or cardiovascular events (MACCEs) occurring in hospital (death, myocardial infarction, stroke; <4% in each group), as well as 30-day rates of MACCEs (6.1% in Group 1, 11.9% in Group 2, 12.4% in Group 3) and rehospitalization (18.9% in Group 1, 24.8% in Group 2, 24.8% in Group 3) did not differ significantly. At 1 year, differences in rates of mortality and MACCEs (20.3% in Group 1, 33.1% in Group 2, 34.7% in Group 3; P < 0.01) were significant. Both Groups 2 [hazard ratio (HR) 1.81, P = 0.0122] and 3 (HR 1.85, P = 0.0092) were independently predictive of death. Rehospitalization rates did not differ during follow-up.

CONCLUSIONS

Despite higher mortality in patients with elevated sPAP, these data suggest the safety, feasibility and benefit of MitraClip therapy even in advanced stages of disease. An early approach might prevent the progress of pulmonary hypertension and improve outcomes.

Lung fluid clearance in chronic heart failure patients

Chronic elevation of pulmonary microvascular pressure (Pmv) consistently leads to alveolocapillary barrier thickening and reduction in the filtration coefficient. In animal models of chronic heart failure (CHF) the lung remains dry despite hydrostatic forces. As fluid flux is bi-directional, it has been postulated that an increase in alveolar fluid clearance may facilitate the dry lung when Pmv is chronically elevated. In this study we aimed to examine alveolar fluid clearance in ambulatory patients with CHF secondary to left ventricular (LV) systolic dysfunction compared against non-CHF controls. Lung clearance following aerosol delivery of ^99mtechnetium (Tc)-diethyl triaminepentaacetic acid (DTPA) was measured non-invasively by scintigraphy and half time of ^99mTc-DTPA clearance (T (1/2)) was calculated by mono-exponential curve fit. Alveolar fluid clearance measured as half time DTPA clearance was significantly faster in CHF patients than controls (P=0.001). This was further defined by NYHA classification. No correlation was found between DTPA clearance and plasma epinephrine, norepinephrine or aldosterone hormone (P>0.05). Our results support an association between increasing alveolar fluid clearance and disease severity in CHF, and the concept of controlled bi-directional fluid flux in CHF associated with increasing Pmv, and represents another defence mechanism of the lung against pulmonary oedema.

Impaired Pulmonary Diffusion in Heart Failure With Preserved Ejection Fraction

OBJECTIVES

The purpose of this study was to compare measures of gas exchange at rest and during exercise in patients with heart failure and preserved ejection fraction (HFpEF) with age- and sex-matched control subjects.

BACKGROUND

Patients with HFpEF display elevation in left heart pressures, but it is unclear how this affects pulmonary gas transfer or its determinants at rest and during exercise.

METHODS

Patients with HFpEF (n = 20) and control subjects (n = 26) completed a recumbent cycle ergometry exercise test with simultaneous measurement of ventilation and gas exchange. Diffusion of the lungs for carbon monoxide (DLCO) and its subcomponents, pulmonary capillary blood volume (VC) and alveolar-capillary membrane conductance (DM), were measured at rest, and matched for low-intensity (20 W) and peak exercise. Stroke volume was measured by transthoracic echocardiography to calculate cardiac output.

RESULTS

Compared with control subjects, patients with HFpEF displayed impaired diastolic function and reduced exercise capacity. Patients with HFpEF demonstrated a 24% lower DLCO at rest (11.0 ± 2.3 ml/mm Hg/min vs. 14.4 ± 3.3 ml/mm Hg/min; p < 0.01) related to reductions in both DM (18.1 ± 4.9 ml/mm Hg/min vs. 23.1 ± 9.1 ml/mm Hg/min; p = 0.04), and VC (45.9 ± 15.2. ml vs. 58.9 ± 16.2 ml; p = 0.01). DLCO was lower in patients with HFpEF compared with control subjects in all stages of exercise, yet its determinants showed variable responses. With low-level exercise, patients with HFpEF demonstrated greater relative increases in VC, coupled with heightened ventilatory drive and more severe symptoms of dyspnea compared with control subjects. At 20-W exercise, DM was markedly reduced in patients with HFpEF compared with control subjects. From 20 W to peak exercise, there was no further increase in VC in patients with HFpEF, which in tandem with reduced DM, led to a 30% reduction in DLCO at peak exercise (17.3 ± 4.2 ml/mm Hg/min vs. 24.7 ± 7.1 ml/mm Hg/min; p < 0.01).

CONCLUSIONS

Subjects with HFpEF display altered pulmonary function and gas exchange at rest and especially during exercise, which contributes to exercise intolerance. Novel therapies that improve gas diffusion may be effective to improve exercise tolerance in patients with HFpEF.

Lung Capillary Stress Failure and Arteriolar Remodelling in Pulmonary Hypertension Associated with Left Heart Disease (Group 2 PH)

Left heart diseases (LHD) represent the most prevalent cause of pulmonary hypertension (PH), yet there are still no approved therapies that selectively target the pulmonary circulation in LHD. The increase in pulmonary capillary pressure due to LHD is a triggering event leading to physical and biological alterations of the pulmonary circulation. Acutely, mechanosensitive endothelial dysfunction and increased capillary permeability combined with reduced fluid resorption lead to the development of interstitial and alveolar oedema. From repeated cycles of such capillary stress failure originate more profound changes with pulmonary endothelial dysfunction causing increased basal and reactive pulmonary vascular tone. This contributes to pulmonary vascular remodelling with increased arterial wall thickness, but most prominently, to alveolar wall remodelling characterized by myofibroblasts proliferation with collagen and interstitial matrix deposition. Although protective against acute pulmonary oedema, alveolar wall thickening becomes maladaptive and is responsible for the development of a restrictive lung syndrome and impaired gas exchanges contributing to shortness of breath and PH. Increasing awareness of these processes is unraveling novel pathophysiologic processes that could represent selective therapeutic targets. Thus, the roles of caveolins, of the intermediate myofilament nestin and of endothelial calcium dyshomeostasis were recently evaluated in pre-clinical models. The pathophysiology of PH due to LHD (group II PH) is distinctive from other groups of PH. Therefore, therapies targeting PH due to LHD must be evaluated in that context.

Perfusion-related stimuli for compensatory lung growth following pneumonectomy

Following pneumonectomy (PNX), two separate mechanical forces act on the remaining lung: parenchymal stress caused by lung expansion, and microvascular distension and shear caused by increased perfusion. We previously showed that parenchymal stress and strain explain approximately one-half of overall compensation; the remainder was presumptively attributed to perfusion-related factors. In this study, we directly tested the hypothesis that perturbation of regional pulmonary perfusion modulates post-PNX lung growth. Adult canines underwent banding of the pulmonary artery (PAB) to the left caudal (LCa) lobe, which caused a reduction in basal perfusion to LCa lobe without preventing the subsequent increase in its perfusion following right PNX while simultaneously exaggerating the post-PNX increase in perfusion to the unbanded lobes, thereby creating differential perfusion changes between banded and unbanded lobes. Control animals underwent sham pulmonary artery banding followed by right PNX. Pulmonary function, regional pulmonary perfusion, and high-resolution computed tomography of the chest were analyzed pre-PNX and 3-mo post-PNX. Terminally, the remaining lobes were fixed for detailed morphometric analysis. Results were compared with corresponding lobes in two control (Sham banding and normal unoperated) groups. PAB impaired the indices of post-PNX extravascular alveolar tissue growth by up to 50% in all remaining lobes. PAB enhanced the expected post-PNX increase in alveolar capillary formation, measured by the prevalence of double-capillary profiles, in both unbanded and banded lobes. We conclude that perfusion distribution provides major stimuli for post-PNX compensatory lung growth independent of the stimuli provided by lung expansion and parenchymal stress and strain.

Pulmonary Hypertension in Heart Failure Patients Presenting at OAUTHC, Ile-Ife, Nigeria

Background

Pulmonary hypertension (PH) is common in heart failure patients. Literature on PH in heart failure is sparse in Nigeria. This study was carried out to determine the prevalence of PH in heart failure patients and ascertain the relationship between left ventricular systolic and diastolic function and the degree of PH.

Methods

A total of 125 heart failure patients had echocardiography done. PH was diagnosed using tricuspid regurgitation jet and pulmonary ejection jet profile.

Results

PH was present in 70.4% of heart failure patients. Estimated mean pulmonary arterial pressure increased with increasing severity of systolic and diastolic dysfunction and had significantly negative correlation with ejection fraction, fractional shortening, and early mitral annular tissue diastolic velocity ( E′), but positive correlation with left ventricular end-systolic volume, right ventricular dimension, transmitral E to A ratio, and E/E′ ratio.

Conclusion

PH is very common in heart failure and has significant relationship with left ventricular function.

The pathophysiology of pulmonary hypertension in left heart disease

Pulmonary hypertension (PH) is characterized by elevated pulmonary arterial pressure leading to right-sided heart failure and can arise from a wide range of etiologies. The most common cause of PH, termed Group 2 PH, is left-sided heart failure and is commonly known as pulmonary hypertension with left heart disease (PH-LHD). Importantly, while sharing many clinical features with pulmonary arterial hypertension (PAH), PH-LHD differs significantly at the cellular and physiological levels. These fundamental pathophysiological differences largely account for the poor response to PAH therapies experienced by PH-LHD patients. The relatively high prevalence of this disease, coupled with its unique features compared with PAH, signal the importance of an in-depth understanding of the mechanistic details of PH-LHD. The present review will focus on the current state of knowledge regarding the pathomechanisms of PH-LHD, highlighting work carried out both in human trials and in preclinical animal models. Adaptive processes at the alveolocapillary barrier and in the pulmonary circulation, including alterations in alveolar fluid transport, endothelial junctional integrity, and vasoactive mediator secretion will be discussed in detail, highlighting the aspects that impact the response to, and development of, novel therapeutics.

Plasma immature form of surfactant protein type B correlates with prognosis in patients with chronic heart failure. A pilot single-center prospective study

BACKGROUND

Gas exchange abnormalities are part of the heart failure (HF) syndrome and growing interest raised on possible biomarkers of alveolar-capillary unit damage. The present pilot single-center study sought to investigate the prognostic values of circulating surfactant protein type B (SP-B) in a cohort of systolic HF patients.

METHODS

One hundred and fifty-one HF stable outpatients and 37 healthy subjects underwent a full clinical assessment, including pulmonary function and lung diffusion for carbon monoxide (DLco), maximal cardiopulmonary exercise test and measurements for both circulating immature and mature forms of SP-B. Study end-points were hospitalization due to HF worsening and cardiovascular mortality.

RESULTS

Immature SP-B, but not the mature form, was significantly higher in HF patients than in controls and was independently related to DLco, peak oxygen uptake and ventilatory efficiency. During the follow-up (median: 995 days; interquartile range: 739-1247 days), 97 patients experimented at least one HF hospitalization and 9 died for cardiovascular causes. At univariate analysis immature SP-B levels were significantly related to both cardiovascular death (p=0.033) and HF hospitalization (p<0.001). At multivariate analysis, immature SP-B levels remained independently associated to HF hospitalization (hazard ratio: 2.304; 95% confidence interval 1.858-3.019; p<0.001).

CONCLUSIONS

Present data confirm a strong relationship between circulating immature SP-B levels, gas exchange abnormalities and exercise limitations in stable HF as well as they are consistent with the use of immature SP-B in HF clinical risk assessment. Larger prospective studies are needed to confirm its prognostic role as well as to evaluate whether immature SP-B plasma concentration varies in response to specific treatment.

Endothelial dysfunction and lung capillary injury in cardiovascular diseases

Cardiac dysfunction of both systolic and diastolic origins leads to increased left atrial pressure, lung capillary injury and increased resistance to gas transfer. Acutely, pressure-induced trauma disrupts the endothelial and alveolar anatomical configuration and definitively causes an impairment of cellular pathways involved in fluid-flux regulation and gas exchange efficiency, a process well identified as stress failure of the alveolar-capillary membrane. In chronic heart failure (HF), additional stimuli other than pressure may trigger the true remodeling process of capillaries and small arteries characterized by endothelial dysfunction, proliferation of myofibroblasts, fibrosis and extracellular matrix deposition. In parallel there is a loss of alveolar gas diffusion properties due to the increased path from air to blood (thickening of extracellular matrix) and loss of fine molecular mechanism involved in fluid reabsorption and clearance. Deleterious changes in gas transfer not only reflect the underlying lung tissue damage but also portend independent prognostic information and may play a role in the pathogenesis of exercise limitation and ventilatory abnormalities observed in these patients. Few currently approved treatments for chronic HF have the potential to positively affect structural remodeling of the lung capillary network; angiotensin-converting enzyme inhibitors are one of the few currently established options. Recently, more attention has been paid to novel therapies specifically targeting the nitric oxide pathway as a suitable target to improve endothelial function and permeability as well as alveolar gas exchange properties.

Pulmonary effects of chronic elevation in microvascular pressure differ between hypertension and myocardial infarct induced heart failure

BACKGROUND

Chronic heart failure (CHF) following coronary artery ligation and myocardial infarction in the rat leads to a homeostatic reduction in surface tension with associated alveolar type II cell hyperplasia and increased surfactant content, which functionally compensates for pulmonary collagen deposition and increased tissue stiffness. To differentiate the effects on lung remodelling of the sudden rise in pulmonary microvascular pressure (Pmv) with myocardial infarction from its consequent chronic elevation, we examined a hypertensive model of CHF.

METHODS

Cardiopulmonary outcomes due to chronic pulmonary capillary hypertension were assessed at six and 15 weeks following abdominal aortic banding (AAB) in the rat.

RESULTS

At six weeks post-surgery, despite significantly elevated left ventricular end-diastolic pressure, myocardial hypertrophy and increased left ventricular internal circumference in AAB rats compared with sham operated controls (p≤0.003), lung weights and tissue composition remained unchanged, and lung compliance was normal. At 15 weeks post-surgery increased lung oedema was evident in AAB rats (p=0.002) without decreased lung compliance or evidence of tissue remodelling.

CONCLUSION

Despite chronically elevated Pmv, comparable to that resulting from past myocardial infarction (LVEDP>19mmHg), there is no evidence of pulmonary remodelling in the AAB model of CHF.

Functional adaptation of bovine mesenteric lymphatic vessels to mesenteric venous hypertension

Lymph flow is the primary mechanism for returning interstitial fluid to the blood circulation. Currently, the adaptive response of lymphatic vessels to mesenteric venous hypertension is not known. This study sought to determine the functional responses of postnodal mesenteric lymphatic vessels. We surgically occluded bovine mesenteric veins to create mesenteric venous hypertension to elevate mesenteric lymph flow. Three days after surgery, postnodal mesenteric lymphatic vessels from mesenteric venous hypertension (MVH; n = 7) and sham surgery (Sham; n = 6) group animals were evaluated and compared. Contraction frequency (MVH: 2.98 ± 0.75 min(-1); Sham: 5.42 ± 0.81 min(-1)) and fractional pump flow (MVH: 1.14 ± 0.30 min(-1); Sham: 2.39 ± 0.32 min(-1)) were significantly lower in the venous occlusion group. These results indicate that postnodal mesenteric lymphatic vessels adapt to mesenteric venous hypertension by reducing intrinsic contractile activity.

Lung capillary injury and repair in left heart disease: a new target for therapy?

The lungs are the primary organs affected in LHD (left heart disease). Increased left atrial pressure leads to pulmonary alveolar–capillary stress failure, resulting in cycles of alveolar wall injury and repair. The reparative process causes the proliferation of MYFs (myofibroblasts) with fibrosis and extracellular matrix deposition, resulting in thickening of the alveolar wall. Although the resultant reduction in vascular permeability is initially protective against pulmonary oedema, the process becomes maladaptive causing a restrictive lung syndrome with impaired gas exchange. This pathological process may also contribute to PH (pulmonary hypertension) due to LHD. Few clinical trials have specifically evaluated lung structural remodelling and the effect of related therapies in LHD. Currently approved treatment for chronic HF (heart failure) may have direct beneficial effects on lung structural remodelling. In the future, novel therapies specifically targeting the remodelling processes may potentially be utilized. In the present review, we summarize data supporting the clinical importance and pathophysiological mechanisms of lung structural remodelling in LHD and propose that this pathophysiological process should be explored further in pre-clinical studies and future therapeutic trials.

Gas exchange consequences of left heart failure

This review explores the pathophysiology of gas exchange abnormalities arising consequent to either acute or chronic elevation of pulmonary venous pressures. The initial experimental studies of acute pulmonary edema outlined the sequence of events from lymphatic congestion with edema fluid to frank alveolar flooding and its resultant hypoxemia. Clinical studies of acute heart failure (HF) suggested that hypoxemia was associated only with the final stage of alveolar flooding. However, in patients with chronic heart failure and normal oxygenation, hypoxemia could be produced by the administration of potent pulmonary vasodilators, suggesting that hypoxic pulmonary vasoconstriction is an important reflex for these patients. Patients with chronic left HF commonly manifest a reduced diffusing capacity, an abnormality that appears to be a consequence of chronic elevation of left atrial pressure. That reduction in diffusing capacity does not appear to be primarily attributable to increases in lung water but is improved by any sustained treatment that improves overall cardiac function. Patients with heart failure may also manifest an abnormally elevated VE/VCO2 during exercise, and that exercise ventilation abnormality arises as a consequence of both alveolar hyperventilation and elevated physiologic dead space. That elevated exercise VE/VCO2 in an HF patient has proven to be a powerful predictor of an adverse outcome and hence it has received sustained attention in the HF literature. At least three of the classes of drugs used to treat HF will normalize the exercise VE/VCO2, suggesting that the excessive ventilation response may be linked to elevated sympathetic activity.

Acute lung injury and pulmonary vascular permeability: use of transgenic models

Acute lung injury is a general term that describes injurious conditions that can range from mild interstitial edema to massive inflammatory tissue destruction. This review will cover theoretical considerations and quantitative and semi-quantitative methods for assessing edema formation and increased vascular permeability during lung injury. Pulmonary edema can be quantitated directly using gravimetric methods, or indirectly by descriptive microscopy, quantitative morphometric microscopy, altered lung mechanics, high-resolution computed tomography, magnetic resonance imaging, positron emission tomography, or x-ray films. Lung vascular permeability to fluid can be evaluated by measuring the filtration coefficient (Kf) and permeability to solutes evaluated from their blood to lung clearances. Albumin clearances can then be used to calculate specific permeability-surface area products (PS) and reflection coefficients (σ). These methods as applied to a wide variety of transgenic mice subjected to acute lung injury by hyperoxic exposure, sepsis, ischemia-reperfusion, acid aspiration, oleic acid infusion, repeated lung lavage, and bleomycin are reviewed. These commonly used animal models simulate features of the acute respiratory distress syndrome, and the preparation of genetically modified mice and their use for defining specific pathways in these disease models are outlined. Although the initiating events differ widely, many of the subsequent inflammatory processes causing lung injury and increased vascular permeability are surprisingly similar for many etiologies.

Structure and composition of pulmonary arteries, capillaries, and veins

The pulmonary vasculature comprises three anatomic compartments connected in series: the arterial tree, an extensive capillary bed, and the venular tree. Although, in general, this vasculature is thin-walled, structure is nonetheless complex. Contributions to structure (and thus potentially to function) from cells other than endothelial and smooth muscle cells as well as those from the extracellular matrix should be considered. This review is multifaceted, bringing together information regarding (i) classification of pulmonary vessels, (ii) branching geometry in the pulmonary vascular tree, (iii) a quantitative view of structure based on morphometry of the vascular wall, (iv) the relationship of nerves, a variety of interstitial cells, matrix proteins, and striated myocytes to smooth muscle and endothelium in the vascular wall, (v) heterogeneity within cell populations and between vascular compartments, (vi) homo- and heterotypic cell-cell junctional complexes, and (vii) the relation of the pulmonary vasculature to that of airways. These issues for pulmonary vascular structure are compared, when data is available, across species from human to mouse and shrew. Data from studies utilizing vascular casting, light and electron microscopy, as well as models developed from those data, are discussed. Finally, the need for rigorous quantitative approaches to study of vascular structure in lung is highlighted.

An orally active TRPV4 channel blocker prevents and resolves pulmonary edema induced by heart failure

Pulmonary edema resulting from high pulmonary venous pressure (PVP) is a major cause of morbidity and mortality in heart failure (HF) patients, but current treatment options demonstrate substantial limitations. Recent evidence from rodent lungs suggests that PVP-induced edema is driven by activation of pulmonary capillary endothelial transient receptor potential vanilloid 4 (TRPV4) channels. To examine the therapeutic potential of this mechanism, we evaluated TRPV4 expression in human congestive HF lungs and developed small-molecule TRPV4 channel blockers for testing in animal models of HF. TRPV4 immunolabeling of human lung sections demonstrated expression of TRPV4 in the pulmonary vasculature that was enhanced in sections from HF patients compared to controls. GSK2193874 was identified as a selective, orally active TRPV4 blocker that inhibits Ca(2+) influx through recombinant TRPV4 channels and native endothelial TRPV4 currents. In isolated rodent and canine lungs, TRPV4 blockade prevented the increased vascular permeability and resultant pulmonary edema associated with elevated PVP. Furthermore, in both acute and chronic HF models, GSK2193874 pretreatment inhibited the formation of pulmonary edema and enhanced arterial oxygenation. Finally, GSK2193874 treatment resolved pulmonary edema already established by myocardial infarction in mice. These findings identify a crucial role for TRPV4 in the formation of HF-induced pulmonary edema and suggest that TRPV4 blockade is a potential therapeutic strategy for HF patients.

Chronic elevation of pulmonary microvascular pressure in chronic heart failure reduces bi-directional pulmonary fluid flux

AIMS

Chronic heart failure leads to pulmonary vascular remodelling and thickening of the alveolar-capillary barrier. We examined whether this protective effect may slow resolution of pulmonary oedema consistent with decreased bi-directional fluid flux.

METHODS AND RESULTS

Seven weeks following left coronary artery ligation, we measured both fluid flux during an acute rise in left atrial pressure (n = 29) and intrinsic alveolar fluid clearance (n = 45) in the isolated rat lung. Chronic elevation of pulmonary microvascular pressure prevented pulmonary oedema and decreased lung compliance when left atrial pressure was raised to 20 cmH2O, and was associated with reduced expression of endothelial aquaporin 1 (P = 0.03). However, no other changes were found in mediators of fluid flux or cellular fluid channels. In isolated rat lungs, chronic LV dysfunction (LV end-diastolic pressure and infarct circumference) was also inversely related to alveolar fluid clearance (P ≤ 0.001). The rate of pulmonary oedema reabsorption was estimated by plasma volume expansion in eight patients with a previous clinical history of chronic heart failure and eight without, who presented with acute pulmonary oedema. Plasma volume expansion was reduced at 24 h in those with chronic heart failure (P = 0.03).

CONCLUSIONS

Chronic elevation of pulmonary microvascular pressure in CHF leads to decreased intrinsic bi-directional fluid flux at the alveolar-capillary barrier. This adaptive response defends against alveolar flooding, but may delay resolution of alveolar oedema.

Separating in vivo mechanical stimuli for postpneumonectomy compensation: physiological assessment

Following right pneumonectomy (PNX), the remaining lung expands and its perfusion doubles. Tissue and microvascular mechanical stresses are putative stimuli for initiating compensatory lung growth and remodeling, but their relative contributions to overall compensation remain uncertain. To temporally isolate the stimuli related to post-PNX lung expansion (parenchyma deformation) from those related to the sustained increase in perfusion (microvascular distention and shear), we replaced the right lung of adult dogs with a custom-shaped inflated prosthesis. Following stabilization of perfusion and wound healing 4 mo later, the prosthesis was either acutely deflated (DEF group) or kept inflated (INF group). Physiological studies were performed pre-PNX, 4 mo post-PNX (inflated prosthesis, INF1), and again 4 mo postdeflation (DEF) compared with controls with simultaneous INF prosthesis (INF2). Perfusion to the remaining lung increased ~76-113% post-PNX (INF1 and INF2) and did not change postdeflation. Post-PNX (INF prosthesis) end-expiratory lung volume (EELV) and lung and membrane diffusing capacities (DL(CO) and DM(CO)) at a given perfusion were 25-40% below pre-PNX baseline. In the INF group EELV, DL(CO) and DM(CO) remained stable or declined slightly with time. In contrast, all of these parameters increased significantly after deflation and were 157%, 26%, and 47%, respectively, above the corresponding control values (INF2). Following delayed deflation, lung expansion accounted for 44%-48% of total post-PNX compensatory increase in exercise DL(CO) and peak O(2) uptake; the remainder fraction is likely attributable to the increase in perfusion. Results suggest that expansion-related parenchyma mechanical stress and perfusion-related microvascular stress contribute in equal proportions to post-PNX alveolar growth and remodeling.

Bone morphogenetic protein receptor II regulates pulmonary artery endothelial cell barrier function

Mutations in bone morphogenetic protein receptor II (BMPR-II) underlie most heritable cases of pulmonary arterial hypertension (PAH). However, less than half the individuals who harbor mutations develop the disease. Interestingly, heterozygous null BMPR-II mice fail to develop PAH unless an additional inflammatory insult is applied, suggesting that BMPR-II plays a fundamental role in dampening inflammatory signals in the pulmonary vasculature. Using static- and flow-based in vitro systems, we demonstrate that BMPR-II maintains the barrier function of the pulmonary artery endothelial monolayer suppressing leukocyte transmigration. Similar findings were also observed in vivo using a murine model with loss of endothelial BMPR-II expression. In vitro, the enhanced transmigration of leukocytes after tumor necrosis factor α or transforming growth factor β1 stimulation was CXCR2 dependent. Our data define how loss of BMPR-II in the endothelial layer of the pulmonary vasculature could lead to a heightened susceptibility to inflammation by promoting the extravasation of leukocytes into the pulmonary artery wall. We speculate that this may be a key mechanism involved in the initiation of the disease in heritable PAH that results from defects in BMPR-II expression.

Heart failure and the lung

Heart failure (HF) is a highly prevalent disease that leads to significant morbidity and mortality. There is increasing evidence that the symptoms of HF are exacerbated by its deleterious effects on lung function. HF appears to cause airway obstruction acutely and leads to impaired gas diffusing capacity and pulmonary hypertension in the longer term. It is postulated that this is the result of recurrent episodes of elevated pulmonary capillary pressure leading to pulmonary oedema and pulmonary capillary stress fracture, which produces lung fibrosis. It is likely that impaired lung function impairs the functional status of HF patients and makes them more prone to central sleep apnoea.

Pulmonary hypertension with left-sided heart disease

Pulmonary hypertension (PH) with left-sided heart disease is defined, according to the latest Venice classification, as a Group 2 PH, which includes left-sided ventricular or atrial disease, and left-sided valvular diseases. These conditions are all associated with increased left ventricular filling pressure. Although PH with left-sided heart disease is a common entity, and long-term follow-up trials have provided firm recognition that development of left-sided PH carries a poor outcome, available data on incidence, pathophysiology, and therapy are sparse. Mitral stenosis was reported as the most frequent cause of PH several decades ago, but PH with left-sided heart disease is now usually caused by systemic hypertension and ischemic heart disease. In patients with these conditions, PH develops as a consequence of impaired left ventricular relaxation and distensibility. Chronic sustained elevation of cardiogenic blood pressure in pulmonary capillaries leads to a cascade of untoward retrograde anatomical and functional effects that represent specific targets for therapeutic intervention. The pathophysiological and clinical importance of the hemodynamic consequences of left-sided heart disease, starting with lung capillary injury and leading to right ventricular overload and failure, are discussed in this Review, focusing on PH as an evolving contributor to heart failure that may be amenable to novel interventions.

Beta-adrenoceptor stimulation of alveolar fluid clearance is increased in rats with heart failure

The alveolar epithelium plays a critical role in resolving pulmonary edema. We thus hypothesized that its function might be upregulated in rats with heart failure, a condition that severely challenges the lung's ability to maintain fluid balance. Heart failure was induced by left coronary artery ligation. Echocardiographic and cardiovascular hemodynamics confirmed its development at 16 wk postligation. At that time, alveolar fluid clearance was measured by an increase in protein concentration over 1 h of a 5% albumin solution instilled into the lungs. Baseline alveolar fluid clearance was similar in heart failure and age-matched control rats. Terbutaline was added to the instillate to determine whether heart failure rats responded to beta-adrenoceptor stimulation. Alveolar fluid clearance in heart failure rats was increased by 194% after terbutaline stimulation compared with a 153% increase by terbutaline in control rats. To determine the mechanisms responsible for this accelerated alveolar fluid clearance, we measured ion transporter expression (ENaC, Na-K- ATPase, CFTR). No significant upregulation was observed for these ion transporters in the heart failure rats. Lung morphology showed significant alveolar epithelial type II cell hyperplasia in heart failure rats. Thus, alveolar epithelial type II cell hyperplasia is the likely explanation for the increased terbutaline-stimulated alveolar fluid clearance in heart failure rats. These data provide evidence for previously unrecognized mechanisms that can protect against or hasten resolution of alveolar edema in heart failure.

Reduced surface tension normalizes static lung mechanics in a rodent chronic heart failure model

RATIONALE

Chronic elevation of pulmonary microvascular pressure in chronic heart failure results in compensatory changes in the lung that reduce alveolar fluid filtration and protect against pulmonary microvascular rupture.

OBJECTIVES

To determine whether these compensatory responses may have maladaptive effects on lung function.

METHODS

Six weeks after myocardial infarction (chronic heart failure model) rat lung composition, both gross and histologic; air and saline mechanics; surfactant production; and immunological mediators were examined.

MEASUREMENTS AND MAIN RESULTS

An increase in dry lung weight, due to increased insoluble protein, lipid and cellular infiltrate, without pulmonary edema was found. Despite this, both forced impedance and air pressure-volume mechanics were normal. However, there was increased tissue stiffness in the absence of surface tension (saline pressure-volume curve) with a concurrent increase in both surfactant content and alveolar type II cell numbers, suggesting a novel homeostatic phenomenon.

CONCLUSIONS

These studies suggest a compensatory reduction in pulmonary surface tension that attenuates the effect of lung parenchymal remodeling on lung mechanics, hence work of breathing.

Alveolar gas diffusion abnormalities in heart failure

In heart failure (HF), development of pressure or volume overload of the lung microcirculation elicits a series of structural adaptations, whose functional correlate is an increased resistance to gas transfer across the alveolar-capillary membrane. Acutely, hydrostatic mechanical injury causes endothelial and alveolar cell breaks, impairment of the cellular pathways involved in fluid filtration and reabsorption, and resistance to gas transfer. This process, which is reminiscent of the so-called alveolar-capillary stress failure, is generally reversible. When the alveolar membrane is chronically challenged, tissue alterations are sustained and a typical remodeling process may take place that is characterized by fixed extracellular matrix collagen proliferation and reexpression of fetal genes. Remodeling leads to a persistent reduction in alveolar-capillary membrane conductance and lung diffusion capacity. Changes in gas transfer not only reflect the underlying lung tissue damage but also bring independent prognostic information and may play a role in the pathogenesis of exercise limitation and ventilatory abnormalities. They are not responsive to fluid withdrawal by ultrafiltration and tend to be refractory even to heart transplantation. Some drugs can be effective that modulate lung remodeling (eg, angiotensin-converting enzyme inhibitors, whose impact on the natural course of cardiac remodeling is well known) or that increase nitric oxide availability and nitric oxide-mediated pulmonary vasodilation (eg, type 5 phosphodiesterase inhibitors). This review focuses on the current knowledge of these topics.

Patterns of alveolar fluid clearance in heart failure

Alveolar fluid clearance (AFC) is important in keeping the airspaces free of edema. This process is accomplished via passive and active transport of Na(+) across the alveolo-capillary barrier mostly by apical Na(+) channels and basolateral Na,K-ATPases, respectively. Patterns of alveolar fluid clearance were found to be decreased in acutely elevated left atrial pressures, possibly due to the inhibition of alveolar epithelial active sodium transport. On the other hand, chronic elevation of pulmonary capillary pressure, such as seen in experimental and clinical congestive heart failure, increases alveolar fluid clearance most likely secondary to upregulation of active sodium transport.