Pulmonary pulse wave transit time is associated with right ventricular-pulmonary artery coupling in pulmonary arterial hypertension

Pulmonary Arterial Hemodynamic Assessment by Pulmonary Pulse Transit Time before and after Balloon Mitral Valvuloplasty

Background

Transthoracic echocardiography remains a crucial diagnostic tool for the identification of pulmonary arterial hypertension (PAH). We eagerly await the novel noninvasive techniques development that significantly advances our knowledge of the pulmonary circulation and right ventricle.

Objective

The objective of this study was to assess pulmonary arterial hemodynamics using pulmonary pulse transit time (pPTT) following balloon mitral valvuloplasty (BMV).

Patients and Methods

Thirty-three patients with moderate-to-severe mitral stenosis (MS) with varying pulmonary hypertension degree who were presented to the National Heart Institute to do percutaneous mitral balloon valvuloplasty. Participants were evaluated for their echocardiographic variables including the pPTT, and they were followed up immediately, 1 week, 1 month, and 6 months after BMV.

Results

The study demonstrated a significant and progressive improvement in the right ventricular fractional area change and the tricuspid annular plane systolic excursion (TAPSE) following BMV; on the other hand, the pulmonary artery systolic pressure demonstrated a significant decrease postprocedure and during the follow-up period. On analysis, we found a significant change observed in pPTT values postprocedure (P < 0.001). This value showed a significant reduction immediately following the procedure and the decline continued over the subsequent follow-up periods. Each of these postprocedure measurements showed a significant decrease from the baseline (P < 0.001).

Conclusion

The pPTT was high in postcapillary pulmonary hypertension (in MS patients) and reduced after correction of causative pathology; the pPTT is a valid measure to assess the improvement in PAH after BMV.

Evaluation of right ventricular function in patients with Behcet's disease by four-dimensional echocardiography

AIM

Behcet's disease (BD) is a systemic disorder characterized by vasculitis, resulting in thickened vascular walls that reduce elasticity and impair function. BD can involve the cardiovascular system in three ways: cardiac, arterial, and venous. In this study, our objective was to evaluate the efficacy of pulmonary arterial stiffness (PAS) and pulmonary pulse transit time (PPTT) measures in demonstrating right ventricular functions in asymptomatic BD patients. We aimed to objectively evaluate right ventricular function in patients with BD using four-dimensional echocardiography (4DE).

METHOD

This study included 40 patients diagnosed with BD and 40 healthy subjects. Demographic, clinical, laboratory, and echocardiographic parameters were compared. In addition to standard transthoracic echocardiographic evaluation, right ventricle quantification (RVQ) by using the 4DE and 2D-speckle tracking echocardiography were performed.

RESULTS

The sPAP, 4D RVQ, and right ventricular strain values exhibited significant differences between the BD and control groups. Right ventricular end-diastolic diameter (RVDD), right ventricular end-systolic diameter (RVSD), right atrium (RA) area, right ventricular myocardial performance index (RVMPI), and PAS were increased in BD patients compared to the control group. Right ventricular ejection fraction (RVEF), right ventricular fractional area change (RVFAC), tricuspid annular plane systolic excursion (TAPSE), Tricuspid S', and PPTT were decreased in BD patients compared to control subjects. PPTT correlated with right ventricular free wall strain (RV-FWS) and PAS. In a multivariate linear regression analysis, PAS and RVFAC were found to be independent predictors of RVFWS. In addition, RVFAC and TAPSE are independent predictors for PPTT.

CONCLUSION

Patients with BD may have elevated pulmonary arterial stiffness (PAS) in correlation with decreased PPTT. To ascertain the prognosis for these individuals, right ventricular (RV) functions must be evaluated. Measurements of RVFAC and RVEF via 4DE and deformation imaging techniques may be more useful in identifying subclinical impairment of RV. Individuals with BD, PAS, and PPTT may suggest a link between early pulmonary vascular remodeling and RV subclinical impairment.

Doppler-derived pulmonary pulse transit time measurements in chronic obstructive pulmonary disease: Reproducibility and cardiopulmonary function

INTRODUCTION

Doppler-derived pulmonary pulse transit time (pPTT) is an auspicious hemodynamic marker in chronic pulmonary diseases. The aim is to compare four distinct pPTT measurements and its relation to right cardiac and pulmonary function.

METHODS

Prospectively, 25 chronic obstructive pulmonary disease (COPD) patients (four patients excluded) and 32 healthy subjects underwent repeated distinct pPTT measurements, standard echocardiography, and pulmonary function testing on the same day. pPTT was defined as the interval from the R or Q-wave in the electrocardiogram to the corresponding pulse wave Doppler peak late systolic (S) 2 or diastolic (D) pulmonary vein flow velocity (pPTT R-S, Q-S, R-D, Q-D). Reproducibility was assessed using Bland-Altman analysis, coefficient of variation (COV), intraclass correlation coefficient (ICC), and power calculations. Associations with right ventricular RV tissue and pulse wave Doppler velocities (RV E', RV S', RV A', RV E, RV A, RV E/E', RV E/A), TAPSE, right ventricular fractional area change, left ventricular systolic and diastolic function (LV ejection fraction, E, A, E/A, E/E', septal E', lateral E'), LA diameters, as well as forced expiratory volume in 1 s, forced vital capacity (FVC) predicted (%), and in liters were analyzed.

RESULTS

There was no significant difference and no bias between pPTT measures (p range: .1-.9). COV was in COPD 1.2%-2.3%, in healthy subjects 1.0%-3.1%. ICC ranged from .92 (COPD) to .96 (healthy subjects). In COPD significant correlations were found for pPTT R-S, Q-S and R-D with RV E`, (all > ρ: .49, < p = .0364), pPTT R-S, Q-S with RV E/E` (both > ρ: .49, < p = .0291), pPTT Q-S with RV S´ (ρ: .58, p = .0134), RV A (ρ: .59, p = .0339) and heart rate > ρ: -.39, < p = .0297). pPTT R-S, R-D showed significant correlations with FVC predicted (%) (ρ: .48 p = .0224) and FVC (l) (ρ:.47 p = .0347).

CONCLUSIONS

All pPTT measures exhibited high reproducibility. In COPD patients pPTT measures correlate with diastolic right ventricular function. Defining Q as starting point seems clinically advantageous considering electromechanical desynchrony in patients with conduction disorders.

The relationship of systemic and pulmonary arterial parameters with HFpEF scores (H2 FPEF, HFA-PEFF) and diastolic dysfunction parameters in heart failure patients with preserved ejection fraction

OBJECTIVE

We aimed to show the relationship between pulmonary pulse wave transit time (pPTT), pulmonary artery stiffness (PAS), and aortic stiffness parameters measured by non-invasive methods, HFpEF patients, and HFpEF scores (H2 FPEF, HFA-PEFF).

METHOD

A total of 101 patients were included in our study, 52 of whom were HFpEF patients and 49 were control groups without heart failure. Echocardiographic parameters for PAS and pPTT were calculated, along with diastolic parameters that support the diagnosis of HFpEF. Aortic stiffness was assessed using a PWA monitor. Demographic features, laboratory findings, aortic stiffness parameters, and echocardiographic findings including pulmonary artery parameters were compared with the control group.

RESULTS

PAS, pPTT, PWV were significantly higher in the HFpEF group than in the control group (p < 0.001). PAS and pPTT correlated positively with HFpEF scores. In linear regression analysis for PAS, a directly positive correlation was found between E/e' and PAS, independent of aortic stiffness.

CONCLUSION

These parameters can be used as a predictive value in the diagnosis process of patients with suspected HFpEF. A significant relationship between PAS and ventricular stiffness (E/e') was shown independently of aortic stiffness.

A Simple Echocardiographic Approach in Assessing the Prognosis of Comatose Patients with Acute Intracerebral Hemorrhage by Using Right Ventricle-Pulmonary Artery Coupling

BACKGROUND

It remains a challenge to judge whether comatose patients with acute intracerebral hemorrhage (ICH) can wake up. Here, we aimed to investigate the changes in right ventricle-pulmonary artery (RV-PA) coupling over time in these patients and to evaluate its performance for discriminating between those who woke up within 60 days and those who did not.

METHODS

Thirty-five comatose patients with acute spontaneous ICH underwent bedside echocardiography on days 1, 3, and 5 after onset with the measurement of tricuspid annular plane systolic excursion and mean pulmonary artery pressure. The RV-PA coupling (the ratio of tricuspid annular plane systolic excursion to mean pulmonary artery pressure) was calculated.

RESULTS

Within 60 days of the onset of coma, 11 individuals awakened and survived, and 24 individuals died. In awakened patients, RV-PA couplings did not differ among days 1, 3, and 5 (1.62 ± 0.38 vs. 1.61 ± 0.32 vs. 1.64 ± 0.25 mm/mm Hg, P > 0.05), whereas in unawakened patients, they decreased drastically from day 1 to day 3 and then to day 5 (1.26 ± 0.32 vs. 0.63 ± 0.05 vs. 0.43 ± 0.06 mm/mm Hg, P < 0.05). The area under receiver operating characteristic curve of 0.992 for the ratio of RV-PA coupling on day 5 to day 1 of the coma was superior to that for the Glasgow Coma Scale (area under receiver operating characteristic curve of 0.606) in the discrimination of comatose patients with ICH who woke up within 60 days from those who did not. The optimal cutoff value was 0.536, with a sensitivity of 100.00%, a specificity of 96.24%, and an accuracy of 97.13%.

CONCLUSIONS

Right ventricle-pulmonary artery coupling demonstrated a high performance for discriminating comatose patients with ICH who woke up within 60 days from those who did not.

A multiscale framework for defining homeostasis in distal vascular trees: applications to the pulmonary circulation

Pulmonary arteries constitute a low-pressure network of vessels, often characterized as a bifurcating tree with heterogeneous vessel mechanics. Understanding the vascular complexity and establishing homeostasis is important to study diseases such as pulmonary arterial hypertension (PAH). The onset and early progression of PAH can be traced to changes in the morphometry and structure of the distal vasculature. Coupling hemodynamics with vessel wall growth and remodeling (G&R) is crucial for understanding pathology at distal vasculature. Accordingly, the goal of this study is to provide a multiscale modeling framework that embeds the essential features of arterial wall constituents coupled with the hemodynamics within an arterial network characterized by an extension of Murray's law. This framework will be used to establish the homeostatic baseline characteristics of a pulmonary arterial tree, including important parameters such as vessel radius, wall thickness and shear stress. To define the vascular homeostasis and hemodynamics in the tree, we consider two timescales: a cardiac cycle and a longer period of vascular adaptations. An iterative homeostatic optimization, which integrates a metabolic cost function minimization, the stress equilibrium, and hemodynamics, is performed at the slow timescale. In the fast timescale, the pulsatile blood flow dynamics is described by a Womersley's deformable wall analytical solution. Illustrative examples for symmetric and asymmetric trees are presented that provide baseline characteristics for the normal pulmonary arterial vasculature. The results are compared with diverse literature data on morphometry, structure, and mechanics of pulmonary arteries. The developed framework demonstrates a potential for advanced parametric studies and future G&R and hemodynamics modeling of PAH.

Pulmonary transit time has close relation with pulmonary pulse wave transit time in normal subjects

BACKGROUND

Pulmonary transit time (PTT) and pulmonary pulse wave transit time (pPTT) are useful parameters for the evaluation of cardiopulmonary circulation and vascular alterations, but their relationship remains unknown. The aim of this study was to investigate the correlation between PTT and pPTT.

METHODS

A total of 60 healthy volunteers were involved in this study. They were divided into two groups (30 participants per group): <50 years and >50 years. They all underwent Doppler echocardiography of pulmonary vein flow and contrast echocardiography with the measurement of pPTT and PTT, respectively. The correlation between PTT and pPTT was deduced.

RESULTS

Compared with Group of <50 years, there was a significant increment in left atrial volume index, left atrial pressure and pulmonary artery stiffness but a significant reduction in acceleration times of pulmonary artery flow in Group of >50 years (p < 0.05). Group >50 years had longer PTT and but reduced normalized PTT by R-R interval (NPTT), reduced normalized pPTT by R-R interval (NpPTT) than Group <50 years (p < 0.05), while there was no significant difference in pPTT between the two groups (p > 0.05). PTT and NPTT were all negatively correlated with pPTT and NpPTT. The statistically significant strongest correlation was observed between PTT and NpPTT (r = -0.886, p < 0.0001). The regression equation for them was y = 7.4396-13.095x (R²  = 0.785; p < 0.001), where x and y represent NpPTT and PTT, respectively.

CONCLUSION

PTT had close relation with pPTT in normal subjects. From the regression equation for them, we can get the value of PTT simply and easily by non-invasively measured pPTT.

Imaging in Pulmonary Vascular Disease-Understanding Right Ventricle-Pulmonary Artery Coupling

The right ventricle (RV) and pulmonary arterial (PA) tree are inextricably linked, continually transferring energy back and forth in a process known as RV-PA coupling. Healthy organisms maintain this relationship in optimal balance by modulating RV contractility, pulmonary vascular resistance, and compliance to sustain RV-PA coupling through life's many physiologic challenges. Early in states of adaptation to cardiovascular disease-for example, in diastolic heart failure-RV-PA coupling is maintained via a multitude of cellular and mechanical transformations. However, with disease progression, these compensatory mechanisms fail and become maladaptive, leading to the often-fatal state of "uncoupling." Noninvasive imaging modalities, including echocardiography, magnetic resonance imaging, and computed tomography, allow us deeper insight into the state of coupling for an individual patient, providing for prognostication and potential intervention before uncoupling occurs. In this review, we discuss the physiologic foundations of RV-PA coupling, elaborate on the imaging techniques to qualify and quantify it, and correlate these fundamental principles with clinical scenarios in health and disease. © 2022 American Physiological Society. Compr Physiol 12: 1-26, 2022.

Compromised Cardiopulmonary Function in Fibulin-5 Deficient Mice

Competent elastic fibers are critical to the function of the lung and right circulation. Murine models of elastopathies can aid in understanding the functional roles of the elastin and elastin-associated glycoproteins that constitute elastic fibers. Here, we quantify together lung and pulmonary arterial structure, function, and mechanics with right heart function in a mouse model deficient in the elastin-associated glycoprotein fibulin-5. Differences emerged as a function of genotype, sex, and arterial region. Specifically, functional studies revealed increased lung compliance in fibulin-5 deficiency consistent with a histologically observed increased alveolar disruption. Biaxial mechanical tests revealed that the primary branch pulmonary arteries exhibit decreased elastic energy storage capacity and wall stress despite only modest differences in circumferential and axial material stiffness in the fibulin-5 deficient mice. Histological quantifications confirm a lower elastic fiber content in the fibulin-5 deficient pulmonary arteries, with fragmented elastic laminae in the outer part of the wall - likely the reason for reduced energy storage. Ultrasound measurements confirm sex differences in compromised right ventricular function in the fibulin-5 deficient mice. These results reveal compromised right heart function, but opposite effects of elastic fiber dysfunction on the lung parenchyma (significantly increased compliance) and pulmonary arteries (trend toward decreased distensibility), and call for further probing of ventilation-perfusion relationships in pulmonary pathologies. Amongst many other models, fibulin-5 deficient mice can contribute to our understanding of the complex roles of elastin in pulmonary health and disease.

Assessment of Pulmonary Pulse Transit Time with Respect to Diastolic and Left Atrial Functions

Background and Aim

Pulmonary pulse transit time (pPTT) is a new marker of pulmonary hypertension (PH), which shows the time needed for the pulse wave to propagate from the right ventricular outflow tract to the left atrium (LA), but the relationship between pPTT and diastolic-LA function is almost unknown. In this study, we investigated the relationship between pPTT and LA-diastolic functions without PH.

Materials and Methods

One hundred and fifty-six patients were included in this prospectively designed study. Comprehensive echocardiographic evaluation was performed and pPTT was recorded as the time from the beginning of the R-wave on the electrocardiogram to the peak of the S-wave in the pulmonary veins.

Results

We found a statistically significant correlation between LA total stroke volume, passive stroke volume, LA max area, LA volume (LAV) max and LA volume index (LAVi) max, and pPTT (r = 0.263** P = 0.003, r = 0.240** P = 0.007, (r = 0.339** P < 0.001, r = 0.307** P < 0.001 r = 0.199*, P = 0.024, LA total stroke volume, passive stroke volume, LA max area, LAV max, LAVi max respectively). Heart rate (HRt) and LAVi were detected as independent predictors of pPTT (hazard ratio: -2.290 P < 0.001, 95% confidence interval (CI): -3.274-1.306, HR: 0.461, P = 0.028, 95% CI: 0.050-0.873, HRt and LAVi, respectively).

Conclusion

LAVi and HRt also affected pPTT. The dominant effect of HRt on pPTT should be considered in future studies. Larger studies are needed to determine the change and clinical significance of pPTT in left heart disease.

Inflammatory Glycoprotein 130 Signaling Links Changes in Microtubules and Junctophilin-2 to Altered Mitochondrial Metabolism and Right Ventricular Contractility

BACKGROUND

Right ventricular dysfunction (RVD) is the leading cause of death in pulmonary arterial hypertension (PAH), but no RV-specific therapy exists. We showed microtubule-mediated junctophilin-2 dysregulation (MT-JPH2 pathway) causes t-tubule disruption and RVD in rodent PAH, but the druggable regulators of this critical pathway are unknown. GP130 (glycoprotein 130) activation induces cardiomyocyte microtubule remodeling in vitro; however, the effects of GP130 signaling on the MT-JPH2 pathway and RVD resulting from PAH are undefined.

METHODS

Immunoblots quantified protein abundance, quantitative proteomics defined RV microtubule-interacting proteins (MT-interactome), metabolomics evaluated the RV metabolic signature, and transmission electron microscopy assessed RV cardiomyocyte mitochondrial morphology in control, monocrotaline, and monocrotaline-SC-144 (GP130 antagonist) rats. Echocardiography and pressure-volume loops defined the effects of SC-144 on RV-pulmonary artery coupling in monocrotaline rats (8-16 rats per group). In 73 patients with PAH, the relationship between interleukin-6, a GP130 ligand, and RVD was evaluated.

RESULTS

SC-144 decreased GP130 activation, which normalized MT-JPH2 protein expression and t-tubule structure in the monocrotaline RV. Proteomics analysis revealed SC-144 restored RV MT-interactome regulation. Ingenuity pathway analysis of dysregulated MT-interacting proteins identified a link between microtubules and mitochondrial function. Specifically, SC-144 prevented dysregulation of electron transport chain, Krebs cycle, and the fatty acid oxidation pathway proteins. Metabolomics profiling suggested SC-144 reduced glycolytic dependence, glutaminolysis induction, and enhanced fatty acid metabolism. Transmission electron microscopy and immunoblots indicated increased mitochondrial fission in the monocrotaline RV, which SC-144 mitigated. GP130 antagonism reduced RV hypertrophy and fibrosis and augmented RV-pulmonary artery coupling without altering PAH severity. In patients with PAH, higher interleukin-6 levels were associated with more severe RVD (RV fractional area change 23±12% versus 30±10%, P=0.002).

CONCLUSIONS

GP130 antagonism reduces MT-JPH2 dysregulation, corrects metabolic derangements in the RV, and improves RVD in monocrotaline rats.

Validation of Phase-Resolved Functional Lung (PREFUL) Magnetic Resonance Imaging Pulse Wave Transit Time Compared to Echocardiography in Chronic Obstructive Pulmonary Disease

BACKGROUND

Phase-resolved functional lung (PREFUL) magnetic resonance imaging (MRI) pulmonary pulse wave transit time (pPTT) is a contrast agent free, vascular imaging biomarker, but has not been validated in chronic obstructive pulmonary disease (COPD).

PURPOSE

To validate PREFUL with echocardiographic pPTT as a reference standard and to compare arterial/venous pPTT mapping with spirometry and clinical parameters.

STUDY TYPE

Prospective.

POPULATION

Twenty-one patients (62% female) with COPD and 44 healthy participants (50% female).

FIELD STRENGTH/SEQUENCE

1.5 T; 2D-spoiled gradient-echo sequence.

ASSESSMENT

Three coronal PREFUL MRI slices, echocardiography, and spirometry including forced expiratory volume in 1 second (FEV1, liter) and predicted defined as FEV1 in% divided by the population average FEV1%, were performed. Pulmonary pulse transit time from the main artery to the microvasculature (PREFUL pPTT), to the right upper lobe vein (PREFUL pPTT_av , echo pPTT_av ), from microvasculature to right upper lobe vein (PREFUL_vein ) and the ratio of PREFUL pPTT to PREFUL pPTT_vein were calculated. Body mass index (BMI), Global Initiative for COPD (GOLD) stage 1-4, disease duration, and cigarette packs smoked per day multiplied by the smoked years (pack years) were computed.

STATISTICAL TESTS

Shapiro-Wilk-test, paired-two-sided-t-tests, Bland-Altman-analysis, coefficient of variation, Pearson ρ were applied, pPTT data were compared between 21 subjects from the 44 healthy subjects who were age- and sex-matched to the COPD cohort, P < 0.05 was considered statistically significant.

RESULTS

PREFUL pPTT_av significantly correlated with echo pPTT_av (ρ = 0.95) with 1.85 msec bias, 95% limits of agreement: 55.94 msec, -52.23 msec in all participants (P = 0.59). In the healthy participants, PREFUL and echo pPTT_av significantly correlated with age (ρ = 0.81, ρ = 0.78), FEV1 (ρ = -0.47, ρ = -0.34) and BMI (ρ = 0.56, ρ = 0.51). In COPD patients, PREFUL pPTT significantly correlated with FEV1 predicted (ρ = -0.59), GOLD (ρ = 0.53), disease duration (ρ = 0.54), and pack years (ρ = 0.49).

DATA CONCLUSION

Arteriovenous PTT measured by PREFUL MRI corresponds precisely to echocardiography and appears to be feasible even in severe COPD.

EVIDENCE LEVEL

1 TECHNICAL EFFICACY: Stage 2.

Echocardiography in Pulmonary Arterial Hypertension: Is It Time to Reconsider Its Prognostic Utility?

Pulmonary arterial hypertension (PAH) is characterized by an insult in the pulmonary vasculature, with subsequent right ventricular (RV) adaptation to the increased afterload that ultimately leads to RV failure. The awareness of the importance of RV function in PAH has increased considerably because right heart failure is the predominant cause of death in PAH patients. Given its wide availability and reduced cost, echocardiography is of paramount importance in the evaluation of the right heart in PAH. Several echocardiographic parameters have been shown to have prognostic implications in PAH; however, the role of echocardiography in the risk assessment of the PAH patient is limited under the current guidelines. This review discusses the echocardiographic evaluation of the RV in PAH and during therapy, and its prognostic implications, as well as the potential significant role of repeated echocardiographic assessment in the follow-up of patients with PAH.

Increased Pulmonary Arterial Stiffness and Impaired Right Ventricle-Pulmonary Artery Coupling In PCOS

BACKGROUND

Polycystic ovary syndrome (PCOS) is the most common endocrine-metabolic disease in women in reproductive age, and occurs in one of 10 women. The disease includes menstrual irregularity and excess of male hormones and is the most common cause of female infertility. Dyspnea is a frequent symptom and is often thought to be due to obesity, and whether it is due to cardiac dysfunction is unknown.

OBJECTIVE

To evaluate right ventricle-pulmonary artery (RV-PA) coupling and pulmonary arterial stiffness in patients with PCOS.

METHODS

44 PCOS patients and 60 controls were included; venous blood samples were taken for laboratory tests and 2-D, m-mode and tissue doppler transthoracic echocardiography were performed for all the participants. P<0,05 was considered as statistically significant.

RESULTS

When compared to the control group, PCOS patients had higher pulmonary artery stiffness values (p=0,001), which were positively correlated with HOMA-IR (r=0,545 and p<0,001). RV-PA coupling was also impaired in 34% of the study patients.

CONCLUSION

Pulmonary artery stiffness is increased and RV-PA coupling is impaired in patients with PCOS. (Arq Bras Cardiol. 2021; 116(4):806-811).

Patient-Specific Computational Analysis of Hemodynamics and Wall Mechanics and Their Interactions in Pulmonary Arterial Hypertension

Vascular wall stiffness and hemodynamic parameters are potential biomechanical markers for detecting pulmonary arterial hypertension (PAH). Previous computational analyses, however, have not considered the interaction between blood flow and wall deformation. Here, we applied an established computational framework that utilizes patient-specific measurements of hemodynamics and wall deformation to analyze the coupled fluid-vessel wall interaction in the proximal pulmonary arteries (PA) of six PAH patients and five control subjects. Specifically, we quantified the linearized stiffness (E), relative area change (RAC), diastolic diameter (D), regurgitant flow, and time-averaged wall shear stress (TAWSS) of the proximal PA, as well as the total arterial resistance (R t ) and compliance (C t ) at the distal pulmonary vasculature. Results found that the average proximal PA was stiffer [median: 297 kPa, interquartile range (IQR): 202 kPa vs. median: 75 kPa, IQR: 5 kPa; P = 0.007] with a larger diameter (median: 32 mm, IQR: 5.25 mm vs. median: 25 mm, IQR: 2 mm; P = 0.015) and a reduced RAC (median: 0.22, IQR: 0.10 vs. median: 0.42, IQR: 0.04; P = 0.004) in PAH compared to our control group. Also, higher total resistance (R t ; median: 6.89 mmHg × min/l, IQR: 2.16 mmHg × min/l vs. median: 3.99 mmHg × min/l, IQR: 1.15 mmHg × min/l; P = 0.002) and lower total compliance (C t ; median: 0.13 ml/mmHg, IQR: 0.15 ml/mmHg vs. median: 0.85 ml/mmHg, IQR: 0.51 ml/mmHg; P = 0.041) were observed in the PAH group. Furthermore, lower TAWSS values were seen at the main PA arteries (MPAs) of PAH patients (median: 0.81 Pa, IQR: 0.47 Pa vs. median: 1.56 Pa, IQR: 0.89 Pa; P = 0.026) compared to controls. Correlation analysis within the PAH group found that E was directly correlated to the PA regurgitant flow (r = 0.84, P = 0.018) and inversely related to TAWSS (r = -0.72, P = 0.051). Results suggest that the estimated elastic modulus E may be closely related to PAH hemodynamic changes in pulmonary arteries.

Echocardiographic evaluation of right ventricular-arterial coupling in pulmonary hypertension

Pulmonary hypertension (PH) is a hemodynamic condition characterized by chronically elevated mean pulmonary artery pressure (m-PAP ≥ 25 mmHg) measured at rest by right heart catheterization (RHC). It includes a pre-capillary and a post-capillary form. Pulmonary artery hypertension (PAH) is a pre-capillary form of PH potentially generated by several heterogeneous systemic disorders, whose main hemodynamic change is represented by severely increased pulmonary vascular resistance (PVR). In order to preserve an efficient right ventricular-arterial (RV-PA) coupling, the right ventricle (RV) adapts to this chronic increase of its afterload, with a compensatory hypertrophy, until RV dilatation and dysfunction occur. Right ventricular (RV) function and especially RV-PA coupling assessment showed to be very important prognostic markers in this subset of patients, especially for those with pre-capillary PH. The aim of this review is to provide a pathophysiological insight into the spectrum of RV adaptive changes occurring in response to chronic increase of RV afterload and to present the role of echocardiographic parameters as possible tools for early non-invasive evaluation of RV-PA coupling, before overt heart failure ensues.

Excess Protein O-GlcNAcylation Links Metabolic Derangements to Right Ventricular Dysfunction in Pulmonary Arterial Hypertension

The hexosamine biosynthetic pathway (HBP) converts glucose to uridine-diphosphate-N-acetylglucosamine, which, when added to serines or threonines, modulates protein function through protein O-GlcNAcylation. Glutamine-fructose-6-phosphate amidotransferase (GFAT) regulates HBP flux, and AMP-kinase phosphorylation of GFAT blunts GFAT activity and O-GlcNAcylation. While numerous studies demonstrate increased right ventricle (RV) glucose uptake in pulmonary arterial hypertension (PAH), the relationship between O-GlcNAcylation and RV function in PAH is unexplored. Therefore, we examined how colchicine-mediated AMP-kinase activation altered HBP intermediates, O-GlcNAcylation, mitochondrial function, and RV function in pulmonary artery-banded (PAB) and monocrotaline (MCT) rats. AMPK activation induced GFAT phosphorylation and reduced HBP intermediates and O-GlcNAcylation in MCT but not PAB rats. Reduced O-GlcNAcylation partially restored the RV metabolic signature and improved RV function in MCT rats. Proteomics revealed elevated expression of O-GlcNAcylated mitochondrial proteins in MCT RVs, which fractionation studies corroborated. Seahorse micropolarimetry analysis of H9c2 cardiomyocytes demonstrated colchicine improved mitochondrial function and reduced O-GlcNAcylation. Presence of diabetes in PAH, a condition of excess O-GlcNAcylation, reduced RV contractility when compared to nondiabetics. Furthermore, there was an inverse relationship between RV contractility and HgbA1C. Finally, RV biopsy specimens from PAH patients displayed increased O-GlcNAcylation. Thus, excess O-GlcNAcylation may contribute to metabolic derangements and RV dysfunction in PAH.

Epigenetic Metabolic Reprogramming of Right Ventricular Fibroblasts in Pulmonary Arterial Hypertension: A Pyruvate Dehydrogenase Kinase-Dependent Shift in Mitochondrial Metabolism Promotes Right Ventricular Fibrosis

RATIONALE

Right ventricular (RV) fibrosis in pulmonary arterial hypertension contributes to RV failure. While RV fibrosis reflects changes in the function of resident RV fibroblasts (RVfib), these cells are understudied.

OBJECTIVE

Examine the role of mitochondrial metabolism of RVfib in RV fibrosis in human and experimental pulmonary arterial hypertension.

METHODS AND RESULTS

Male Sprague-Dawley rats received monocrotaline (MCT; 60 mg/kg) or saline. Drinking water containing no supplement or the PDK (pyruvate dehydrogenase kinase) inhibitor dichloroacetate was started 7 days post-MCT. At week 4, treadmill testing, echocardiography, and right heart catheterization were performed. The effects of PDK activation on mitochondrial dynamics and metabolism, RVfib proliferation, and collagen production were studied in RVfib in cell culture. Epigenetic mechanisms for persistence of the profibrotic RVfib phenotype in culture were evaluated. PDK expression was also studied in the RVfib of patients with decompensated RV failure (n=11) versus control (n=7). MCT rats developed pulmonary arterial hypertension, RV fibrosis, and RV failure. MCT-RVfib (but not left ventricular fibroblasts) displayed excess mitochondrial fission and had increased expression of PDK isoforms 1 and 3 that persisted for >5 passages in culture. PDK-mediated decreases in pyruvate dehydrogenase activity and oxygen consumption rate were reversed by dichloroacetate (in RVfib and in vivo) or siRNA targeting PDK 1 and 3 (in RVfib). These interventions restored mitochondrial superoxide and hydrogen peroxide production and inactivated HIF (hypoxia-inducible factor)-1α, which was pathologically activated in normoxic MCT-RVfib. Redox-mediated HIF-1α inactivation also decreased the expression of TGF-β1 (transforming growth factor-beta-1) and CTGF (connective tissue growth factor), reduced fibroblast proliferation, and decreased collagen production. HIF-1α activation in MCT-RVfib reflected increased DNMT (DNA methyltransferase) 1 expression, which was associated with a decrease in its regulatory microRNA, miR-148b-3p. In MCT rats, dichloroacetate, at therapeutic levels in the RV, reduced phospho-pyruvate dehydrogenase expression, RV fibrosis, and hypertrophy and improved RV function. In patients with pulmonary arterial hypertension and RV failure, RVfib had increased PDK1 expression.

CONCLUSIONS

MCT-RVfib manifest a DNMT1-HIF-1α-PDK-mediated, chamber-specific, metabolic memory that promotes collagen production and RV fibrosis. This epigenetic mitochondrial-metabolic pathway is a potential antifibrotic therapeutic target.

Hypochloremia Is a Noninvasive Predictor of Mortality in Pulmonary Arterial Hypertension

Background

Pulmonary arterial hypertension (PAH) is a lethal disease. In resource‐limited countries PAH outcomes are worse because therapy costs are prohibitive. To improve global outcomes, noninvasive and widely available biomarkers that identify high‐risk patients should be defined. Serum chloride is widely available and predicts mortality in left heart failure, but its prognostic utility in PAH requires further investigation.

Methods and Results

In this study 475 consecutive PAH patients evaluated at the University of Minnesota and Vanderbilt University PAH clinics were examined. Clinical characteristics were compared by tertiles of serum chloride. Both the Kaplan‐Meier method and Cox regression analysis were used to assess survival and predictors of mortality, respectively. Categorical net reclassification improvement and relative integrated discrimination improvement compared prediction models. PAH patients in the lowest serum chloride tertile (≤101 mmol/L: hypochloremia) had the lowest 6‐minute walk distance and highest right atrial pressure despite exhibiting no differences in pulmonary vascular disease severity. The 1‐, 3‐, and 5‐year survival was reduced in hypochloremic patients when compared with the middle‐ and highest‐tertile patients (86%/64%/44%, 95%/78%/59%, and, 91%/79%/66%). After adjustment for age, sex, diuretic use, serum sodium, bicarbonate, and creatinine, the hypochloremic patients had increased mortality when compared with the middle‐tertile and highest‐tertile patients. The Minnesota noninvasive model (functional class, 6‐minute walk distance, and hypochloremia) was as effective as the French noninvasive model (functional class, 6‐minute walk distance, and elevated brain natriuretic peptide or N‐terminal pro–brain natriuretic peptide) for predicting mortality.

Conclusions

Hypochloremia (≤101 mmol/L) identifies high‐risk PAH patients independent of serum sodium, renal function, and diuretic use.

Clinical Determinants and Prognostic Implications of Right Ventricular Dysfunction in Pulmonary Hypertension Caused by Chronic Lung Disease

Background

Patients with pulmonary hypertension caused by chronic lung disease (Group 3 PH) have disproportionate right ventricle (RV) dysfunction, but the correlates and clinical implications of RV dysfunction in Group 3 PH are not well defined.

Methods and Results

We performed a cohort study of 147 Group 3 PH patients evaluated at the University of Minnesota. RV systolic function was quantified using right ventricular fractional area change (RVFAC) and ⁺dP/dt_max/instantaneous pressure. Tau and RV diastolic stiffness characterized RV diastolic function. Multivariate linear regression was used to define correlates of RVFAC. Kaplan‐Meier and Cox proportional hazards analyses were used to examine freedom from heart failure hospitalization and death. Positive correlates of RVFAC on univariate analysis were pulmonary arterial compliance, cardiac index, and left ventricular diastolic dimension. Conversely, male sex, N‐terminal pro‐brain natriuretic peptide, heart rate, right atrial enlargement, mean pulmonary arterial pressure, and pulmonary vascular resistance were negative correlates. Male sex was the strongest predictor of lower RVFAC, after adjusting for pulmonary vascular resistance and pulmonary arterial compliance. When comparing sexes, males had lower RVFAC (26% versus 31%, P=0.03) both overall and for any given mean pulmonary arterial pressure and pulmonary vascular resistance value. Males exhibited a reduction in ⁺dP/dt_max/instantaneous pressure as pulmonary vascular resistance increased, whereas females did not. There were no sex differences in RV diastolic function. RV dysfunction (RVFAC <28%) was associated with increased risk of heart failure hospitalization or death (hazard ratio: 1.84, 95% CI: 1.04–3.10, P=0.035).

Conclusions

Male sex is associated with RV dysfunction in Group 3 PH, even after adjusting for RV afterload. RV dysfunction (RVFAC <28%) identifies Group 3 PH patients at risk for poor outcomes.

Prolonged pulmonary pulse transit time is associated with symptoms in patients with significant mitral stenosis and sinus rhythm

INTRODUCTION

Pulmonary pulse transit time (pPTT) is a novel noninvasive echocardiographic measure to assess pulmonary arterial hemodynamics. It has been shown to be shorter in precapillary pulmonary hypertension (PHT). Mitral stenosis (MS) is one of the causes of postcapillary PHT. We aimed to investigate pPTT in patients with MS and its relationship with symptoms.

METHODS

We included 51 patients with MS (25 were asymptomatic, NYHA I, and 26 were symptomatic, NHYA II or III), and 50 controls, and evaluated their demographic characteristics and echocardiographic variables, including pPTT.

RESULTS

Baseline characteristics, including age, sex, body mass index, and cardiovascular risk factors, were similar between the MS and the control group. The pPTT was longer in the MS group than in the control group (0.21 ± 0.08 vs 0.15 ± 0.05, P < .001). Patients with symptomatic MS had longer pPTT than asymptomatic patients (P = .005). The pPTT was positively correlated with left atrial volume index and systolic pulmonary artery pressure, and negatively with tricuspid annular plane systolic excursion (r = .432; P < .001, r = .319; P = .001, r = -.293; and P = .003, respectively).

CONCLUSION

The measurement of pPTT appears clinically relevant in patients with PHT. Further studies evaluating whether it is useful in distinguishing precapillary from postcapillary PHT are required.

Right ventricular function in pulmonary (arterial) hypertension

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

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

CLINICAL TRIAL REGISTRATION

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

Survival in pulmonary hypertension due to chronic lung disease: Influence of low diffusion capacity of the lungs for carbon monoxide

BACKGROUND

Patients with pulmonary hypertension (PH) due to chronic lung disease (Group 3 PH) have poor long-term outcomes. However, predictors of survival in Group 3 PH are not well described.

METHODS

We performed a cohort study of Group 3 PH patients (n = 143; mean age 65 ± 12 years, 52% female) evaluated at the University of Minnesota. The Kaplan-Meier method and Cox regression analysis were used to assess survival and predictors of mortality, respectively. The clinical characteristics and survival were compared in patients categorized by PH severity based on the World Health Organization (WHO) classification and lung disease etiology.

RESULTS

After a median follow-up of 1.4 years, there were 69 (48%) deaths. The 1-, 3-, and 5-year survival rates were 79%, 48%, and 31%. Age, coronary artery disease, atrial fibrillation, Charlson comorbidity index, serum N-terminal pro‒brain natriuretic peptide (NT-proBNP), creatinine, diffusion capacity of carbon monoxide (DLCO), total lung capacity, left ventricular ejection fraction, right atrial and right ventricular enlargement on echocardiography, cardiac index, and pulmonary vascular resistance (PVR) were univariate predictors of survival. On multivariable analysis, DLCO was the only predictor of mortality (adjusted hazard ratio [HR] for every 10% decrease in predicted value: 1.31 [95% confidence interval 1.12 to 1.47]; p = 0.003). The 1-/5-year survival by tertiles of DLCO was 84%/56%, 82%/44%, and 63%/14% (p = 0.01), respectively. On receiver-operating characteristic curve analysis, DLCO <32% of predicted had the highest sensitivity and specificity for predicting survival. The 1- and 5-year survival in patients with a DLCO ≥32% predicted was 84% and 60% vs 68% and 13% in patients with a DLCO <32% predicted (adjusted HR: 2.5 [95% confidence interval 1.3 to 5.0]; p = 0.007). Lung volumes and DLCO were not related, but higher PVR was strongly associated with reduced DLCO. There was increased mortality in interstitial lung disease‒PH as compared with chronic obstructive pulmonary disease‒PH, but PH severity based on the WHO classification did not alter survival.

CONCLUSIONS

Low DLCO is a predictor of mortality and should be used to risk-stratify Group 3 PH patients.

Interleukin-6 is independently associated with right ventricular function in pulmonary arterial hypertension

BACKGROUND

An elevated serum level of interleukin-6 (IL-6) in pulmonary arterial hypertension (PAH) patients results in a greater symptom burden and increased mortality; however, the mechanisms underlying these observations remain unclear. Because both pre-clinical and clinical data associate elevated IL-6 levels with impaired cardiac function, we hypothesized that the adverse effects of IL-6 in PAH result, in part, from right ventricular (RV) dysfunction.

METHODS

We analyzed the relationship between IL-6 and RV function in 40 patients with PAH identified in our institutional PAH registry. Serum IL-6 levels was quantified by enzyme-linked immunoassay.

RESULTS

PAH patients had higher IL-6 levels than age- and gender-matched controls. Circulating IL-6 levels correlated inversely with echocardiography-based measures of RV function and RV-pulmonary artery (RV-PA) coupling. When dividing PAH patients by median IL-6 level, patients with higher IL-6 had significantly worse RV function (fractional area change [FAC] 23 ± 12% vs 38 ± 11%, tricuspid annular plane systolic excursion [TAPSE] 1.3 ± 0.3 cm vs 2.1 ± 0.5 cm), impaired RV-PA coupling (0.6 ± 0.5%/mm Hg vs 0.9 ± 0.5%/mm Hg), higher right atrial pressure (13 ± 7 mm Hg vs 9 ± 5 mm Hg), reduced cardiac index (2.0 ± 0.5 liters/min/m² vs 2.8 ± 1.0 liters/min/m²) and lower stroke volume (48 ± 20 ml vs 70 ± 28 ml). In contrast, the relationships between IL-6 and mean pulmonary artery pressure (mPAP), pulmonary vascular resistance (PVR) and pulmonary arterial compliance (PAC) were not significant. Finally, IL-6 was independently associated with RV function and RV-PA coupling after adjusting for static (PVR) and pulsatile (PAC) after-load on the RV.

CONCLUSIONS

Serum IL-6 levels are independently associated with RV function and RV-PA coupling in PAH. Patients with higher IL-6 levels have more severe RV dysfunction and diminished RV-PA coupling despite a comparable severity of pulmonary vascular disease.

Colchicine Depolymerizes Microtubules, Increases Junctophilin-2, and Improves Right Ventricular Function in Experimental Pulmonary Arterial Hypertension

BACKGROUND

Pulmonary arterial hypertension (PAH) is a lethal disease characterized by obstructive pulmonary vascular remodeling and right ventricular (RV) dysfunction. Although RV function predicts outcomes in PAH, mechanisms of RV dysfunction are poorly understood, and RV-targeted therapies are lacking. We hypothesized that in PAH, abnormal microtubular structure in RV cardiomyocytes impairs RV function by reducing junctophilin-2 (JPH2) expression, resulting in t-tubule derangements. Conversely, we assessed whether colchicine, a microtubule-depolymerizing agent, could increase JPH2 expression and enhance RV function in monocrotaline-induced PAH.

METHODS AND RESULTS

Immunoblots, confocal microscopy, echocardiography, cardiac catheterization, and treadmill testing were used to examine colchicine's (0.5 mg/kg 3 times/week) effects on pulmonary hemodynamics, RV function, and functional capacity. Rats were treated with saline (n=28) or colchicine (n=24) for 3 weeks, beginning 1 week after monocrotaline (60 mg/kg, subcutaneous). In the monocrotaline RV, but not the left ventricle, microtubule density is increased, and JPH2 expression is reduced, with loss of t-tubule localization and t-tubule disarray. Colchicine reduces microtubule density, increases JPH2 expression, and improves t-tubule morphology in RV cardiomyocytes. Colchicine therapy diminishes RV hypertrophy, improves RV function, and enhances RV-pulmonary artery coupling. Colchicine reduces small pulmonary arteriolar thickness and improves pulmonary hemodynamics. Finally, colchicine increases exercise capacity.

CONCLUSIONS

Monocrotaline-induced PAH causes RV-specific derangement of microtubules marked by reduction in JPH2 and t-tubule disarray. Colchicine reduces microtubule density, increases JPH2 expression, and improves both t-tubule architecture and RV function. Colchicine also reduces adverse pulmonary vascular remodeling. These results provide biological plausibility for a clinical trial to repurpose colchicine as a RV-directed therapy for PAH.