Prognostic significance of sympathetic nervous system activation in pulmonary arterial hypertension

Sleep-related disorders in patients with precapillary pulmonary hypertension

Precapillary pulmonary hypertension (PcPH) is associated with the development of sleep-related disorders and impairment of sleep quality. With growing recognition of the clinical relevance of sleep-related conditions in PcPH, this narrative review seeks to discuss the spectrum of disorders encountered in clinical practice, pathophysiological mechanisms linking PcPH with sleep-related disorders, and potential therapeutic considerations. Current evidence demonstrates a higher prevalence of impaired sleep quality, sleep-disordered breathing, sleep-related hypoxia, and restless leg syndrome in patients with PcPH. These sleep-related disorders could further lead to impairment of quality of life in a patient population with already a high symptom burden. Recent data suggest that sleep-related hypoxia is strongly linked to worse right ventricular function and higher risk of transplantation or death. However, limited studies have investigated the role of oxygen therapy or positive airway pressure therapy improving symptoms or outcomes. Abnormal iron homeostasis is highly prevalent in PcPH and may contribute to the development of restless legs syndrome/periodic limb movement of sleep. To improve sleep management in PcPH, we highlight future research agenda and advocate close collaboration between pulmonary hypertension specialists and sleep physicians.

Assessing the role of tracheostomy placement in bronchopulmonary dysplasia with pulmonary hypertension

OBJECTIVE

Bronchopulmonary dysplasia (BPD) is a common complication of preterm birth and is associated with abnormal vasculature that contributes to pulmonary hypertension (PH). We evaluated how a tracheostomy may alter PH in these patients.

METHODS

A retrospective chart review over 15-years identified 17 patients with BPD and PH who underwent tracheostomy. Each patient had four echocardiograms re-reviewed and scored for tricuspid valve regurgitation velocity (TR), tricuspid annular plane systolic excursion (TAPSE), right atrial cross-sectional area (RACA), and left ventricle eccentricity indices (EI).

RESULT

There was improvement in TR, TAPSE, RACA, and left ventricle EI indicating reduction in PH after tracheostomy.

CONCLUSION

PH improves over time though role of tracheostomy in PH needs to be further defined. The EI may be a sensitive marker to follow over time in these patients.

Atrial Arrhythmias in Patients With Pulmonary Hypertension

TOPIC IMPORTANCE

Atrial arrhythmias (AA) are common in patients with pulmonary hypertension (PH) and contribute to morbidity and mortality. Given the growing PH population, understanding the pathophysiology, clinical impact, and management of AA in PH is important.

REVIEW FINDINGS

AA occurs in PH with a 5-year incidence of 10% to 25%. AA confers a higher morbidity and mortality, and restoration of normal sinus rhythm improves survival and functionality. AA is thought to develop because of structural alterations of the right atrium caused by changes to the right ventricle (RV) due to elevated pulmonary artery pressures. AA can subsequently worsen RV function. Current guidelines do not provide comprehensive recommendations for the management of AA in PH. Robust evidence to favor a specific treatment approach is lacking. Although the role of medical rate or rhythm control, and the use of cardioversion and ablation, can be inferred from other populations, evidence is lacking in the PH population. Much remains to be determined regarding the optimal management strategy. We present here our institutional approach and discuss areas for future research.

SUMMARY

This review highlights the epidemiology and pathophysiology of AA in patients with PH, describes the relationship between AA and RV dysfunction, and discusses current management practices. We outline our institutional approach and offer directions for future investigation.

Respiratory, cardiovascular and musculoskeletal mechanisms involved in the pathophysiology of pulmonary hypertension: An updated systematic review of preclinical and clinical studies

BACKGROUND

Progressive exercise intolerance is a hallmark of pulmonary hypertension (pH), severely impacting patients' independence and quality of life (QoL). Accumulating evidence over the last decade shows that combined abnormalities in peripheral reflexes and target organs contribute to disease progression and exercise intolerance.

OBJECTIVE

The aim of this study was to review the literature of the last decade on the contribution of the cardiovascular, respiratory, and musculoskeletal systems to pathophysiology and exercise intolerance in pH.

METHODS

A systematic literature search was conducted using specific terms in PubMed, SciELO, and the Cochrane Library databases for original pre-clinical or clinical studies published between 2013 and 2023. Studies followed randomized controlled/non-randomized controlled and pre-post designs.

RESULTS

The systematic review identified 25 articles reporting functional or structural changes in the respiratory, cardiovascular, and musculoskeletal systems in pH. Moreover, altered biomarkers in these systems, lower cardiac baroreflex, and heightened peripheral chemoreflex activity seemed to contribute to functional changes associated with poor prognosis and exercise intolerance in pH. Potential therapeutic strategies acutely explored involved manipulating the baroreflex and peripheral chemoreflex, improving cardiovascular autonomic control via cardiac vagal control, and targeting specific pathways such as GPER1, GDF-15, miR-126, and the JMJD1C gene.

CONCLUSION

Information published in the last 10 years advances the notion that pH pathophysiology involves functional and structural changes in the respiratory, cardiovascular, and musculoskeletal systems and their integration with peripheral reflexes. These findings suggest potential therapeutic targets, yet unexplored in clinical trials, that could assist in improving exercise tolerance and QoL in patients with pH.

The role of serum sodium in poor prognosis evaluation of pulmonary hypertension associated with left heart disease

BACKGROUND

Previous studies have shown that hyponatremia was strongly associated with a poor prognosis of type 1 pulmonary hypertension, and our team's antecedent studies found that low serum sodium was associated with the severity and the length of hospitalization of pulmonary hypertension associated with left ventricular disease (PH-LHD). However, the relationship between serum sodium and the prognosis of PH-LHD remains unclear. This study aims to determine the clinical value of serum sodium in evaluating poor prognosis in patients with PH-LHD.

METHODS

We successfully followed 716 patients with PH-LHD. Kaplan-Meier was used to plot survival in PH-LHD patients with different serum sodium levels. The effect of serum sodium on poor prognosis was analyzed using a Cox proportional risk model. The trends between patients serum sodium and survival were visualized by restricted cubic spline (RCS).

RESULTS

The survival rates at 1, 2, 3 and 4 years were 52%, 41%, 31% and 31% for the patients with hyponatremia associated with PH-LHD and 71%, 71%, 71% and 54% for the patients with hypernatremia, respectively. The observed mortality rate in the hyponatremia and hypernatremia groups surpassed that of the normonatremic group. The adjusted risks of death (risk ratio) for patients with hyponatremia and hypernatremia were found to be 2.044 and 1.877. Furthermore, the restricted cubic spline demonstrated an L-shaped correlation between serum sodium and all-cause mortality in patients with PH-LHD.

CONCLUSIONS

Abnormal serum sodium level is strongly associated with poor prognosis in PH-LHD. Serum sodium may play an important pathogenic role in PH-LHD occurrence and could be used as a marker to assess the survival in patients.

Ultrasound Neuromodulation of an Anti-Inflammatory Pathway at the Spleen Improves Experimental Pulmonary Hypertension

BACKGROUND

Inflammation is pathogenically implicated in pulmonary arterial hypertension; however, it has not been adequately targeted therapeutically. We investigated whether neuromodulation of an anti-inflammatory neuroimmune pathway involving the splenic nerve using noninvasive, focused ultrasound stimulation of the spleen (sFUS) can improve experimental pulmonary hypertension.

METHODS

Pulmonary hypertension was induced in rats either by Sugen 5416 (20 mg/kg SQ) injection, followed by 21 (or 35) days of hypoxia (sugen/hypoxia model), or by monocrotaline (60 mg/kg IP) injection (monocrotaline model). Animals were randomized to receive either 12-minute-long sessions of sFUS daily or sham stimulation for 14 days. Catheterizations, echocardiography, indices of autonomic function, lung and heart histology and immunohistochemistry, spleen flow cytometry, and lung single-cell RNA sequencing were performed after treatment to assess the effects of sFUS.

RESULTS

Splenic denervation right before induction of pulmonary hypertension results in a more severe disease phenotype. In both sugen/hypoxia and monocrotaline models, sFUS treatment reduces right ventricular systolic pressure by 25% to 30% compared with sham treatment, without affecting systemic pressure, and improves right ventricular function and autonomic indices. sFUS reduces wall thickness, apoptosis, and proliferation in small pulmonary arterioles, suppresses CD3+ and CD68+ cell infiltration in lungs and right ventricular fibrosis and hypertrophy and lowers BNP (brain natriuretic peptide). Beneficial effects persist for weeks after sFUS discontinuation and are more robust with early and longer treatment. Splenic denervation abolishes sFUS therapeutic benefits. sFUS partially normalizes CD68+ and CD8+ T-cell counts in the spleen and downregulates several inflammatory genes and pathways in nonclassical and classical monocytes and macrophages in the lung. Differentially expressed genes in those cell types are significantly enriched for human pulmonary arterial hypertension-associated genes.

CONCLUSIONS

sFUS causes dose-dependent, sustained improvement of hemodynamic, autonomic, laboratory, and pathological manifestations in 2 models of experimental pulmonary hypertension. Mechanistically, sFUS normalizes immune cell populations in the spleen and downregulates inflammatory genes and pathways in the lung, many of which are relevant in human disease.

The effect of hyperoxia on muscle sympathetic nerve activity: a systematic review and meta-analysis

PURPOSE

We conducted a meta-analysis to determine the effect of hyperoxia on muscle sympathetic nerve activity in healthy individuals and those with cardio-metabolic diseases.

METHODS

A comprehensive search of electronic databases was performed until August 2022. All study designs (except reviews) were included: population (humans; apparently healthy or with at least one chronic disease); exposures (muscle sympathetic nerve activity during hyperoxia or hyperbaria); comparators (hyperoxia or hyperbaria vs. normoxia); and outcomes (muscle sympathetic nerve activity, heart rate, blood pressure, minute ventilation). Forty-nine studies were ultimately included in the meta-analysis.

RESULTS

In healthy individuals, hyperoxia had no effect on sympathetic burst frequency (mean difference [MD] - 1.07 bursts/min; 95% confidence interval [CI] - 2.17, 0.04bursts/min; P = 0.06), burst incidence (MD 0.27 bursts/100 heartbeats [hb]; 95% CI - 2.10, 2.64 bursts/100 hb; P = 0.82), burst amplitude (P = 0.85), or total activity (P = 0.31). In those with chronic diseases, hyperoxia decreased burst frequency (MD - 5.57 bursts/min; 95% CI - 7.48, - 3.67 bursts/min; P < 0.001) and burst incidence (MD - 4.44 bursts/100 hb; 95% CI - 7.94, - 0.94 bursts/100 hb; P = 0.01), but had no effect on burst amplitude (P = 0.36) or total activity (P = 0.90). Our meta-regression analyses identified an inverse relationship between normoxic burst frequency and change in burst frequency with hyperoxia. In both groups, hyperoxia decreased heart rate but had no effect on any measure of blood pressure.

CONCLUSION

Hyperoxia does not change sympathetic activity in healthy humans. Conversely, in those with chronic diseases, hyperoxia decreases sympathetic activity. Regardless of disease status, resting sympathetic burst frequency predicts the degree of change in burst frequency, with larger decreases for those with higher resting activity.

Noninvasive Stereotactic Radiotherapy for PADN in an Acute Canine Model of Pulmonary Arterial Hypertension

This study assesses the feasibility, safety, and effectiveness of noninvasive stereotactic body radiotherapy (SBRT) as an approach for pulmonary artery denervation in canine models. SBRT with CyberKnife resulted in reduced mean pulmonary artery pressure, pulmonary capillary wedge pressure, and pulmonary vascular resistance, and insignificantly increased cardiac output. In comparison to the control group, serum norepinephrine levels at 1 month and 6 months were significantly lower in the CyberKnife group. Computed tomography, pulmonary angiography, and histology analysis revealed that SBRT was associated with minimal collateral damage.

Role of Oxygen Starvation in Right Ventricular Decompensation and Failure in Pulmonary Arterial Hypertension

Right ventricular (RV) function and eventually failure determine outcome in patients with pulmonary arterial hypertension (PAH). Initially, RV responds to an increased load caused by PAH with adaptive hypertrophy; however, eventually RV failure ensues. Unfortunately, it is unclear what causes the transition from compensated RV hypertrophy to decompensated RV failure. Moreover, at present, there are no therapies for RV failure; those for left ventricular (LV) failure are ineffective, and no therapies specifically targeting RV are available. Thus there is a clear need for understanding the biology of RV failure and differences in physiology and pathophysiology between RV and LV that can ultimately lead to development of such therapies. In this paper, we discuss RV adaptation and maladaptation in PAH, with a particular focus of oxygen delivery and hypoxia as the principal drivers of RV hypertrophy and failure, and attempt to pinpoint potential sites for therapy.

Sleep-disordered breathing patterns and prognosis in pulmonary arterial hypertension: A cluster analysis of nocturnal cardiorespiratory signals

BACKGROUND

Sleep-disordered breathing (SDB) is common among pulmonary arterial hypertension (PAH) patients and has been associated with unfavorable outcomes. This study aims to cluster overnight cardiorespiratory signals to investigate PAH phenotypes and examining their prognostic implications.

METHODS

In this retrospective cohort study, we recruited consecutive PAH patients who underwent right heart catheterization and nocturnal cardiorespiratory polygraphy to evaluate SDB. Cluster analysis was employed to classify patients based on their SDB patterns. Cox regression analysis and Kaplan-Meier curves were utilized to assess the association between cluster membership and clinical outcomes. Logistic regression was used to identify risk factors associated with the cluster at higher risk of adverse outcomes.

RESULTS

The study comprised 386 PAH patients, with a mean age of 44.7 ± 17.0 years, of which 46.6 % were male. Three distinct clusters of PAH patients were identified: Cluster 1 (N = 182) presented with minimal SDB, Cluster 2 (N = 125) displayed obstructive sleep apnea (OSA) without significant hypoxemia, and Cluster 3 (N = 79) exhibited predominantly severe hypoxemic burden along with comorbid OSA. Notably, patients in Cluster 3 had an independent association with an increased risk of clinical worsening (hazard ratio 1.96, 95 % confidence interval [CI] 1.08-3.56, P = 0.027) compared to those in Clusters 1, even after adjusting for common confounders. The rate of clinical worsening for PAH-related events and mortality was higher in Cluster 3 than in Clusters 1 and 2 (26.6 % vs. 12.6 % and 19.2 %, respectively, log-rank P = 0.024). Moreover, the left ventricular mass index was identified as an independent risk factor for Cluster 3 (odds ratios 1.01, 95 % CI 1.00-1.02, P = 0.004).

CONCLUSIONS

Patients with PAH who have nocturnal hypoxemia and OSA had worse clinical outcomes compared to those with only minimal SDB. Tailored management strategies that address both PAH and nocturnal hypoxemia may be effective in improving clinical outcomes.

Effect of balloon pulmonary angioplasty on cardio-ankle vascular index and biventricular remodeling in patients with chronic thromboembolic pulmonary hypertension

Background

Chronic thromboembolic pulmonary hypertension (CTEPH) is caused by organized pulmonary thrombi, and pulmonary endarterectomy is the only curative treatment. Since balloon pulmonary angioplasty (BPA) has become an established therapeutic option for inoperable CTEPH, prognosis has improved. Recent reports suggest that arterial stiffness evaluated using the cardio-ankle vascular index (CAVI) may play an important role in the cardio-vascular interaction in CTEPH; however, the details remain unclear. This study aimed to clarify the role of CAVI in CTEPH through hemodynamic changes and ventricular remodeling after BPA.

Methods and results

A total of 23 patients with CTEPH who had undergone BPA were enrolled in this study. The mean pulmonary artery pressure (mPAP) and CAVI significantly decreased after BPA [mPAP, 34 (26-45) mmHg to 20 (19-24) mmHg, p < 0.0001; CAVI, 9.4 (8.0-10.3) to 8.3 (7.5-9.6), p = 0.004]. The echocardiographic right ventricle was significantly decreased, and the left ventricular volume was significantly increased after BPA, indicating significant biventricular remodeling after BPA. Changes in CAVI (ΔCAVI) significantly correlated with changes in mPAP (r = 0.45, p = 0.03). Additionally, ΔCAVI was significantly correlated with changes in both right ventricular area and left ventricular volume.

Conclusions

Arterial stiffness, evaluated using the CAVI, improved after BPA. Changes in CAVI were significantly correlated with changes in pulmonary arterial pressure and biventricular remodeling. CAVI may play an important role in cardiovascular interactions in patients with CTEPH.

Pulmonary Artery Denervation as a New Therapeutic Option for Pulmonary Hypertension: A Systematic Review and Meta-Analysis

Pulmonary hypertension (PH) is a progressive disease with a high morbidity and mortality. The treatment is based on the type of PH. Prognosis still remains poor despite the use of different medications. Pulmonary artery denervation (PADN) has been studied as a novel therapeutic option in these patients. PUBMED, EMBASE and COCHRANE databases were searched by 2 investigators until January 2023. Information was analyzed for the following outcomes: 6-minute walk distance (6MWD), mean pulmonary artery pressure, pulmonary vascular resistance and cardiac output. Subgroup analysis comparing pre and post PADN in different PH groups was done. Statistical analysis was performed with the Review Manager version 5.4. This meta- analysis included 6 controlled trials and 6 single-arm prospective studies with a total of 616 patients. Our pooled analysis showed a significant reduction in mean pulmonary artery pressure [WMD -6.51, 95% CI (-9.87, -3.15), p = 0.0001], pulmonary vascular resistance [WMD -3.69, 95% CI (-6.74, -0.64), p = 0.02] and increased cardiac output [WMD -0.37, 95% CI (0.08, 0.65), p = 0.01]. Subgroup analysis pre and post PADN demonstrated a significant improvement in 6MWD in the WHO group 1 [WMD 99.53, 95% CI (19.60, 179.47), p = 0.01], group 2 [WMD: 69.96, 95% CI (36.40, 103.51), p = < 0.0001] and group 4 [WMD: 99.54, 95% CI (21.80, 177.28), p = 0.01]. This meta-analysis supports PADN as a therapeutic option for patients with PH, regardless of group class. Further randomized trials are still needed to evaluate safety and efficacy.

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

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

Clinical Diagnostic Value of Serum GABA, NE, ET-1, and VEGF in Chronic Obstructive Pulmonary Disease with Pulmonary Hypertension

Background

Pulmonary hypertension (PH) is the one of the most common complications of chronic obstructive pulmonary disease (COPD). Whereas, the associated diagnostic factors are uncertain. The present study aims to investigate useful diagnostic factors in patients with COPD and PH (COPD-PH).

Patients and Methods

A total of 111 patients with COPD in Shanxi Bethune Hospital from December 2019 to December 2020 were divided into COPD (PASP≤50 mmHg) and COPD-PH groups (PASP>50 mmHg). Pulmonary function and chest CT results were collected. Routine blood, biochemical, and blood coagulation function indices were examined for all patients. Arterial blood gas analysis and serum cytokines were also measured. Differences in the distribution of the above indicators between the two groups were analyzed using binary logistic regression analysis to identify the risk factors of COPD-PH, and multiple linear regression analysis to determine the factors affecting PASP. The influencing factors and joint predictive factors of the above linear regression analysis were analyzed using the ROC curve. The area under the curve and the best cut-off value were calculated, and their predictive value and clinical significance in disease diagnosis were discussed.

Results

A total of 27 indexes with statistically significant differences between the two groups were identified (P < 0.05). Binary Logistic regression analysis showed that the factors influencing the diagnosis of pulmonary hypertension were serum GABA, NE, VEGF, BUN, and LYM% levels (P < 0.05). Multiple linear regression showed that the factors influencing PASP were serum NE, ET-1, GABA, and VEGF levels, and the goodness of fit of the model was 0.748 (P < 0.001). ROC curve showed that the AUC of the combined diagnosis of serum NE, ET-1, GABA, and VEGF levels was 0.966 (sensitivity, 87.5%; specificity, 93.65%).

Conclusion

Serum NE and ET-1 are risk factors for COPD-PH, whereas serum GABA and VEGF are protective factors against COPD-PH. The combined diagnostic value of serum NE, ET-1, GABA, and VEGF levels was the highest.

ACE2 overexpression in corticotropin-releasing-hormone cells offers protection against pulmonary hypertension

Background

Pulmonary hypertension (PH), characterized by elevated pulmonary pressure and right heart failure, is a systemic disease involving inappropriate sympathetic activation and an impaired gut-brain-lung axis. Global overexpression of angiotensin converting enzyme 2 (ACE2), a cardiopulmonary protective enzyme of the renin-angiotensin system, attenuates PH induced by chronic hypoxia. Neurons within the paraventricular nucleus of the hypothalamus (PVN) that synthesize corticotropin-releasing hormone (CRH) are activated by stressors, like hypoxia, and this activation augments sympathetic outflow to cardiovascular tissues. These data coupled with our observations that ACE2 overexpression in CRH cells (CRH-ACE2KI mice) decreases anxiety-like behavior via suppression of hypothalamic-pituitary-adrenal (HPA) axis activity by decreasing CRH synthesis, led us to hypothesize that selective ACE2 overexpression in CRH neurons would protect against hypoxia-induced PH.

Methods

CRH-ACE2KI and WT male and female mice were exposed to chronic hypoxia (10%O2) or normoxia (21%O2) for 4 weeks in a ventilated chamber with continuous monitoring of oxygen and carbon dioxide concentrations (n = 7-10/group). Pulmonary hemodynamics were measured with Millar pressure catheters then tissues were collected for histological analyses.

Results

Chronic hypoxia induced a significant increase (36.4%) in right ventricular (RV) systolic pressure (RVSP) in WT mice, which was not observed in CRH-ACE2KI mice. No significant differences in RVSP were observed between male and female mice in any of the groups.

Conclusion

Overexpression of ACE2 in CRH cells was protective against hypoxia-induced PH. Since the majority of expression of CRH is in brain nuclei such as paraventricular nucleus of the hypothalamus (PVN) and/or central nucleus of the amygdala (CeA) these data indicate that the protective effects of ACE2 are, at least in part, centrally mediated. This contributes to the systemic nature of PH disease and that CRH neurons may play an important role in PH.

Treatment effects of pulmonary artery denervation for pulmonary arterial hypertension stratified by REVEAL risk score: Results from PADN-CFDA trial

BACKGROUND

The differential treatment effect of pulmonary artery denervation (PADN) in pulmonary arterial hypertension (PAH) patients with different risk burdens remains unclear. This study aimed to determine the effectiveness of PADN in low vs intermediate-high-risk PAH patients.

METHODS

In total, 128 patients with treatment naive PAH included in the PADN-CFDA trial were categorized into low-risk and intermediate-high-risk patients. The primary endpoint was the between-group difference in the change in 6-min walk distance (6 MWD) from baseline to 6 months.

RESULTS

In the intermediate-high-risk group, those treated with PADN and PDE-5i had a greater improvement in 6 MWD from baseline to 6 months as compared to those treated with sham plus PDE-5i. From baseline to 6 months, pulmonary vascular resistance (PVR) was reduced by -6.1 ± 0.6 and -2.0 ± 0.7 Wood units following PADN plus PDE-5i and sham plus PDE-5i, respectively, along with the significant reduction of NT-proBNP in the intermediate-high-risk group. However, there were no significant differences in 6 MWD, PVR, and NT-proBNP between the PADN plus PDE-5i and sham plus PDE-5i groups among low-risk patients. Moreover, the right ventricular function was equally improved by PADN treatment across the low-, intermediate-, and high-risk groups. Clinical worsening was less with PADN plus PDE-5i treatment during the 6-month follow-up.

CONCLUSIONS

In patients with pulmonary arterial hypertension, pulmonary artery denervation plus PDE-5i improved exercise capacity, NT-proBNP, hemodynamic, and clinical outcomes during the 6-month follow-up among intermediate-high risk patients.

The Evolution of Pulmonary Artery Denervation for Treatment of Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a progressive, life-limiting disease. Despite significant medical progress over the last three decades, the prognosis of PAH remains poor. PAH is associated with sympathetic nervous system over-stimulation and baroreceptor-mediated vasoconstriction, leading to pathologic pulmonary artery (PA) and right ventricular remodeling. PA denervation is a minimally-invasive intervention that ablates local sympathetic nerve fibers and baroreceptors to modulate pathologic vasoconstriction. Preliminary animal and clinical studies have shown improvements in short-term pulmonary hemodynamics and PA remodeling. However, future studies are needed to elucidate appropriate patient selection, timing of intervention, and long-term efficacy before integration into standard of care.

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

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

Thoracic Spinal Cord Neuroinflammation as a Novel Therapeutic Target in Pulmonary Hypertension

BACKGROUND

Pulmonary hypertension (PH) is associated with aberrant sympathoexcitation leading to right ventricular failure (RVF), arrhythmias, and death. Microglial activation and neuroinflammation have been implicated in sympathoexcitation in experimental PH. We recently reported the first evidence of thoracic spinal cord (TSC) neuroinflammation in PH rats. Here, we hypothesize that PH is associated with increased cardiopulmonary afferent signaling leading to TSC-specific neuroinflammation and sympathoexcitation. Furthermore, inhibition of TSC neuroinflammation rescues experimental PH and RVF.

METHODS

We performed transcriptomic analysis and its validation on the TSC of monocrotaline (n=8) and Sugen hypoxia (n=8) rat models of severe PH-RVF. A group of monocrotaline rats received either daily intrathecal microglial activation inhibitor minocycline (200 μg/kg per day, n=5) or PBS (n=5) from day 14 through 28. Echocardiography and right ventricle-catheterization were performed terminally. Real-time quantitative reverse transcription PCR, immunolocalization, microglia+astrocyte quantification, and terminal deoxynucleotidyl transferase dUTP nick end labeling were assessed. Plasma catecholamines were measured by ELISA. Human spinal cord autopsy samples (Control n=3; pulmonary arterial hypertension n=3) were assessed to validate preclinical findings.

RESULTS

Increased cardiopulmonary afferent signaling was demonstrated in preclinical and clinical PH. Our findings delineated common dysregulated genes and pathways highlighting neuroinflammation and apoptosis in the remodeled TSC and highlighted increased sympathoexcitation in both rat models. Moreover, we validated significantly increased microglial and astrocytic activation and CX3CL1 expression in TSC of human pulmonary arterial hypertension. Finally, amelioration of TSC neuroinflammation by minocycline in monocrotaline rats inhibited microglial activation, decreased proinflammatory cytokines, sympathetic nervous system activation and significantly attenuated PH and RVF.

CONCLUSIONS

Targeting neuroinflammation and associated molecular pathways and genes in the TSC may yield novel therapeutic strategies for PH and RVF.

New Drugs and Therapies in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension is a chronic, progressive disorder of the pulmonary vasculature with associated pulmonary and cardiac remodeling. PAH was a uniformly fatal disease until the late 1970s, but with the advent of targeted therapies, the life expectancy of patients with PAH has now considerably improved. Despite these advances, PAH inevitably remains a progressive disease with significant morbidity and mortality. Thus, there is still an unmet need for the development of new drugs and other interventional therapies for the treatment of PAH. One shortcoming of currently approved vasodilator therapies is that they do not target or reverse the underlying pathogenesis of the disease process itself. A large body of evidence has evolved in the past two decades clarifying the role of genetics, dysregulation of growth factors, inflammatory pathways, mitochondrial dysfunction, DNA damage, sex hormones, neurohormonal pathways, and iron deficiency in the pathogenesis of PAH. This review focuses on newer targets and drugs that modify these pathways as well as novel interventional therapies in PAH.

Effects of Acute Hypoxia on Heart Rate Variability in Patients with Pulmonary Vascular Disease

Pulmonary vascular diseases (PVDs), defined as arterial or chronic thromboembolic pulmonary hypertension, are associated with autonomic cardiovascular dysregulation. Resting heart rate variability (HRV) is commonly used to assess autonomic function. Hypoxia is associated with sympathetic overactivation and patients with PVD might be particularly vulnerable to hypoxia-induced autonomic dysregulation. In a randomised crossover trial, 17 stable patients with PVD (resting PaO₂ ≥ 7.3 kPa) were exposed to ambient air (FiO₂ = 21%) and normobaric hypoxia (FiO₂ = 15%) in random order. Indices of resting HRV were derived from two nonoverlapping 5-10-min three-lead electrocardiography segments. We found a significant increase in all time- and frequency-domain HRV measures in response to normobaric hypoxia. There was a significant increase in root mean squared sum difference of RR intervals (RMSSD; 33.49 (27.14) vs. 20.76 (25.19) ms; p < 0.01) and RR50 count divided by the total number of all RR intervals (pRR50; 2.75 (7.81) vs. 2.24 (3.39) ms; p = 0.03) values in normobaric hypoxia compared to ambient air. Both high-frequency (HF; 431.40 (661.56) vs. 183.70 (251.25) ms²; p < 0.01) and low-frequency (LF; 558.60 (746.10) vs. 203.90 (425.63) ms²; p = 0.02) values were significantly higher in normobaric hypoxia compared to normoxia. These results suggest a parasympathetic dominance during acute exposure to normobaric hypoxia in PVD.

Pulmonary Artery Denervation for Pulmonary Arterial Hypertension: A Sham-Controlled Randomized PADN-CFDA Trial

BACKGROUND

World Health Organization (WHO) group 1 pulmonary arterial hypertension (PAH) is a progressive, debilitating disease. Previous observational studies have demonstrated that pulmonary artery denervation (PADN) reduces pulmonary artery pressures in PAH. However, the safety and effectiveness of PADN have not been established in a randomized trial.

OBJECTIVES

The aim of this study was to determine the treatment effects of PADN in patients with group 1 PAH.

METHODS

Patients with WHO group 1 PAH not taking PAH-specific drugs for at least 30 days were enrolled in a multicenter, sham-controlled, single-blind, randomized trial. Patients were assigned to receive PADN plus a phosphodiesterase-5 inhibitor or a sham procedure plus a phosphodiesterase-5 inhibitor. The primary endpoint was the between-group difference in the change in 6-minute walk distance from baseline to 6 months.

RESULTS

Among 128 randomized patients, those treated with PADN compared with sham had a greater improvement in 6-minute walk distance from baseline to 6 months (mean adjusted between-group difference 33.8 m; 95% CI: 16.7-50.9 m; P < 0.001). From baseline to 6 months, pulmonary vascular resistance was reduced by -3.0 ± 0.3 WU after PADN and -1.9 ± 0.3 WU after sham (adjusted difference -1.4; 95% CI: -2.6 to -0.2). PADN also improved right ventricular function, reduced tricuspid regurgitation, and decreased N-terminal pro-brain natriuretic peptide. Clinical worsening was less (1.6% vs 13.8%; OR: 0.11; 95% CI: 0.01-0.87), and a satisfactory clinical response was greater (57.1% vs 32.3%; OR: 2.79; 95% CI: 1.37-5.82) with PADN treatment during 6-month follow-up.

CONCLUSIONS

In patients with WHO group 1 PAH, PADN improved exercise capacity, hemodynamic status, and clinical outcomes during 6-month follow-up. (Safety and Efficacy of Pulmonary Artery Denervation in Patients With Pulmonary Arterial Hypertension [PADN-CFDA]; NCT03282266).

Current status of pulmonary artery denervation

Pulmonary hypertension is a progressive disease with a poor long-term prognosis and high mortality. Pulmonary artery denervation (PADN) is emerging as a potential novel therapy for this condition. The basis of pursuing a sympathetic denervation strategy has its origins in a body of experimental translation work that has demonstrated that denervation can reduce sympathetic nerve activity in various animal models. This reduction in pulmonary sympathetic nerve activity is associated with a reduction in pathological pulmonary hemodynamics in response to mechanical, pharmacological, and toxicologically induced pulmonary hypertension. The most common method of PADN is catheter-directed thermal ablation. Since 2014, there have been 12 reports on the role of PADN in 490 humans with pulmonary hypertension (311:179; treated: control). Of these, six are case series, three are randomized trials, and three are case reports. Ten studies used percutaneous PADN techniques, and two combined PADN with mitral and/or left atrial surgery. PADN treatment has low mortality and morbidity and is associated with an improved 6-minute walking distance, a reduction in both mean pulmonary artery pressure and pulmonary vascular resistance, and an improvement in cardiac output. These improved outcomes were seen over a median follow-up of 12 months (range 2–46 months). A recent meta-analysis of human trials also supports the effectiveness of PADN in carefully selected patients. Based on the current literature, PADN can be effective in select patients with pulmonary hypertension. Additional randomized clinical trials against best medical therapy are required.

Symptom phenotypes in Pulmonary Arterial Hypertension: The PAH “Symptome”

Women with pulmonary arterial hypertension (PAH) experience multiple symptoms, including dyspnea, fatigue, and sleep disturbance, that impair their health‐related quality of life (HRQOL). However, we know little about phenotypic subgroups of patients with PAH with similar, concurrent, multiple symptoms. The objectives of this study were to define the “symptome” by symptom cluster phenotypes and compare characteristics such as biomarkers, cardiac structure and function (echocardiography), functional capacity (6‐min walk distance), and HRQOL between the groups. This cross‐sectional study included 60 women with PAH. Subjects completed an assessment battery: Pulmonary Arterial Hypertension Symptom Scale, Pittsburgh Sleep Quality Index, Multidimensional Dyspnea Profile, Patient‐Reported Outcomes Measurement Information System (PROMIS®) Physical Function, PROMIS® Sleep‐Related Impairment, and the emPHasis‐10. Subjects also underwent transthoracic echocardiography, phlebotomy, 6‐min walk distance, and actigraphy. The three symptoms of dyspnea, fatigue, and sleep disturbance were used to define the symptom clusters. Other PAH symptoms, plasma and serum biomarkers, cardiac structure and function (echocardiography), exercise capacity (6‐min walk distance), sleep (actigraphy), and HRQOL were compared across phenotypes. The mean age was 50 ± 18 years, 51% were non‐Hispanic white, 32% were non‐Hispanic Black and 40% had idiopathic PAH. Cluster analysis identified Mild (n = 28, 47%), Moderate (n = 20, 33%), and Severe Symptom Cluster Phenotypes (n = 12, 20%). There were no differences for age, race, or PAH etiology between the phenotypes. WHO functional class (p < 0.001), norepinephrine levels (p = 0.029), right atrial pressure (p = 0.001), physical function (p < 0.001), sleep onset latency (p = 0.040), and HRQOL (p < 0.001) all differed significantly across phenotypes. We identified three distinctive symptom cluster phenotypes (Mild, Moderate, and Severe) for women with PAH that also differed by PAH‐related symptoms, physical function, right atrial pressure, norepinephrine levels, and HRQOL. These phenotypes could suggest targeted interventions to improve symptoms and HRQOL in those most severely affected.

Percutaneous Treatments for Pulmonary Hypertension: Reviewing the Growing Procedural Role for Interventional Cardiology

Pulmonary arterial hypertension is a common and highly morbid medical problem resulting in elevated pulmonary arterial pressures and pulmonary vascular resistance. Medical therapies are costly, and not always well-tolerated. Surgical therapies such as pulmonary endarterectomy and lung transplantation are limited to a small subset of patients due to various patient, disease, or institutional factors. Over the past decade, there has been growing investigation into endovascular interventional therapies for patients with pulmonary hypertension such as balloon pulmonary angioplasty and pulmonary denervation. In this review, we describe the current status, future directions, and our recommendations on technical considerations with these therapies.

Development and Validation of a Nomogram for Predicting Obstructive Sleep Apnea in Patients with Pulmonary Arterial Hypertension

PURPOSE

Patients with pulmonary arterial hypertension (PAH) are at high risk for obstructive sleep apnea (OSA), which may adversely affect pulmonary hemodynamics and long-term prognosis. However, there is no clinical prediction model to evaluate the probability of OSA among patients with PAH. Our study aimed to develop and validate a nomogram for predicting OSA in the setting of PAH.

PATIENTS AND METHODS

From May 2020 to November 2021, we retrospectively analyzed the medical records of 258 patients diagnosed with PAH via right-heart catheterization. All participants underwent overnight cardiorespiratory polygraphy for OSA assessment. General clinical materials and biochemical measurements were collected and compared between PAH patients with or without OSA. Lasso regression was performed to screen potential predictors. Multivariable logistic regression analysis was conducted to establish the nomogram. Concordance index, calibration curve, and decision curve analysis were used to determine the discrimination, calibration, and clinical usefulness of the nomogram.

RESULTS

OSA was present in 26.7% of the PAH patients, and the prevalence did not differ significantly between male (29.7%) and female (24.3%) patients. Six variables were selected to construct the nomogram, including age, body mass index, hypertension, uric acid, glycated hemoglobin, and interleukin-6 levels. Based on receiver operating characteristic analysis, the nomogram demonstrated favorable discrimination accuracy with an area under the curve (AUC) of 0.760 for predicting OSA, exhibiting a better predictive value in contrast to ESS (AUC = 0.528) (P < 0.001). Decision curve analysis and clinical impact curve analysis also indicated the clinical utility of the nomogram.

CONCLUSION

By establishing a comprehensive and practical nomogram, we were able to predict the presence of OSA in patients with PAH, which may facilitate the early identification of patients that benefit from further diagnostic confirmation and intervention.

The physiologic basis of pulmonary arterial hypertension

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

Ventilatory efficiency in pulmonary vascular diseases

Cardiopulmonary exercise testing (CPET) is a frequently used tool in the differential diagnosis of dyspnoea. Ventilatory inefficiency, defined as high minute ventilation (V′_E) relative to carbon dioxide output (V′_CO2), is a hallmark characteristic of pulmonary vascular diseases, which contributes to exercise intolerance and disability in these patients. The mechanisms of ventilatory inefficiency are multiple and include high physiologic dead space, abnormal chemosensitivity and an altered carbon dioxide (CO₂) set-point. A normal V′_E/V′_CO2 makes a pulmonary vascular disease such as pulmonary arterial hypertension (PAH) or chronic thromboembolic pulmonary hypertension (CTEPH) unlikely. The finding of high V′_E/V′_CO2 without an alternative explanation should prompt further diagnostic testing to exclude PAH or CTEPH, particularly in patients with risk factors, such as prior venous thromboembolism, systemic sclerosis or a family history of PAH. In patients with established PAH or CTEPH, the V′_E/V′_CO2 may improve with interventions and is a prognostic marker. However, further studies are needed to clarify the added value of assessing ventilatory inefficiency in the longitudinal follow-up of patients.

Ventilatory inefficiency is a hallmark feature of PH that reflects abnormal ventilation/perfusion matching, chemosensitivity and an altered CO₂ set-point. Minute ventilation/CO₂ production is useful in the diagnosis, management and prognostication of PH.https://bit.ly/3jnNdUG

Prognostic biomarkers in pediatric pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a progressive life-threatening disease of the pulmonary vasculature. Despite the introduction of targeted therapies, prognosis remains poor. In pediatric PAH, reliable prognostic biomarkers are needed to inform clinicians on disease progression and risk of mortality, in order to be able to assess the need for escalation of medical therapy, consider surgical options such as Pott's shunt and listing for (heart)-lung transplantation. This review provides an overview of prognostic biomarkers that are considered to carry potential for the clinical management of pediatric PAH. These include conventional physiological biomarkers [resting heart rate, heart rate variability (HRV), a child's growth], biomarkers of functional status [World Health Organization functional class, 6-minute walk distance (6MWD), parameters derived from cardiopulmonary exercise testing (CPET), daily physical activity level], electrocardiographic biomarkers, circulating serum biomarkers (natriuretic peptides, uric acid, neurohormones, inflammatory markers, and novel circulating biomarkers), and multiple hemodynamic biomarkers and imaging biomarkers [echocardiography and cardiac magnetic resonance (CMR)]. In recent years, many potential prognostic biomarkers have become available for the management of PAH in children. As the available prognostic biomarkers reflect different aspects of the disease process and functional implications, a multi-marker approach appears the most useful for guiding therapy decisions and improve outcome in pediatric PAH.

BKCa Channel Activation Attenuates the Pathophysiological Progression of Monocrotaline-Induced Pulmonary Arterial Hypertension in Wistar Rats

PURPOSE

In the present study, the therapeutic efficacy of a selective BK_Ca channel opener (compound X) in the treatment of monocrotaline (MCT)-induced pulmonary arterial hypertension (PAH) was investigated.

METHODS

PAH was induced in male Wistar rats by a single injection of MCT. After two weeks, the MCT-treated group was divided into two groups that were either treated with compound X or vehicle. Compound X was administered daily at 28 mg/kg. Electrocardiographic, echocardiographic, and haemodynamic analyses were performed; ex vivo evaluations of pulmonary artery reactivity, right ventricle (RV) and lung histology as well as expression levels of α and β myosin heavy chain, brain natriuretic peptide, and cytokines (TNFα and IL10) in heart tissue were performed.

RESULTS

Pulmonary artery rings of the PAH group showed a lower vasodilatation response to acetylcholine, suggesting endothelial dysfunction. Compound X promoted strong vasodilation in pulmonary artery rings of both control and MCT-induced PAH rats. The untreated hypertensive rats presented remodelling of pulmonary arterioles associated with increased resistance to pulmonary flow; increased systolic pressure, hypertrophy and fibrosis of the RV; prolongation of the QT and T_peak-T_end intervals (evaluated during electrocardiogram); increased lung and liver weights; and autonomic imbalance with predominance of sympathetic activity. On the other hand, treatment with compound X reduced pulmonary vascular remodelling, pulmonary flow resistance and RV hypertrophy and afterload.

CONCLUSION

The use of a selective and potent opener to activate the BK_Ca channels promoted improvement of haemodynamic parameters and consequent prevention of RV maladaptive remodelling in rats with MCT-induced PAH.

The Role of Exercise Testing in Pulmonary Vascular Disease: Diagnosis and Management

Exercise intolerance is the dominant symptom of pulmonary hypertension (PH). The gold standard for the estimation of exercise capacity is a cycle ergometer incremental cardiopulmonary exercise test (CPET). The main clinical variables generated by a CPET are peak oxygen uptake (Vo2peak), ventilatory equivalents for carbon dioxide (VE/Vco₂), systolic blood pressure, oxygen (O2) pulse, and chronotropic responses. PH is associated with hyperventilation at rest and at exercise, and an increase in physiologic dead space. Maximal cardiac output depends on right ventricular function and critically determines a PH patient's exercise capacity. Dynamic arterial O2 desaturation can also depress the Vo2peak.

The Value of Heart Rhythm Complexity in Identifying High-Risk Pulmonary Hypertension Patients

Pulmonary hypertension (PH) is a fatal disease—even with state-of-the-art medical treatment. Non-invasive clinical tools for risk stratification are still lacking. The aim of this study was to investigate the clinical utility of heart rhythm complexity in risk stratification for PH patients. We prospectively enrolled 54 PH patients, including 20 high-risk patients (group A; defined as WHO functional class IV or class III with severely compromised hemodynamics), and 34 low-risk patients (group B). Both linear and non-linear heart rate variability (HRV) variables, including detrended fluctuation analysis (DFA) and multiscale entropy (MSE), were analyzed. In linear and non-linear HRV analysis, low frequency and high frequency ratio, DFAα1, MSE slope 5, scale 5, and area 6–20 were significantly lower in group A. Among all HRV variables, MSE scale 5 (AUC: 0.758) had the best predictive power to discriminate the two groups. In multivariable analysis, MSE scale 5 (p = 0.010) was the only significantly predictor of severe PH in all HRV variables. In conclusion, the patients with severe PH had worse heart rhythm complexity. MSE parameters, especially scale 5, can help to identify high-risk PH patients.

Sympathetic innervation of canine pulmonary artery and morphometric and functional analysis in dehydromonocrotaline-induced models after pulmonary artery denervation

OBJECTIVES

We aimed to describe the anatomic distribution of periarterial pulmonary sympathetic nerves and to observe the long-term morphometric and functional changes after pulmonary artery denervation (PADN), a novel therapy for pulmonary arterial hypertension (PAH).

METHODS

A total of 45 beagles were divided into a sympathetic innervation group (n = 3, 33.3% were females), a PAH group (n = 35, 34.3% were females) and a control group (n = 7, 28.5% were females). The PAH group was randomly divided into no-PADN (n = 7), instant-PADN (n = 7), 1M-PADN (n = 7), 2M-PADN (n = 7) and 3M-PADN (n = 7) subgroups. The sympathetic innervation group was sacrificed to reveal the sympathetic innervation of pulmonary arteries. PAH was induced by injecting dehydromonocrotaline (DHMCT) through the right atrium. The pulmonary capillary wedge pressure, right ventricular systolic pressure, right ventricular mean pressure, pulmonary artery systolic pressure and pulmonary artery mean pressure of each group were continuously measured. The cardiac output was detected to calculate the pulmonary vascular resistance. PAH and control groups were subjected to immunofluorescence assay, sympathetic nerve conduction velocity measurement and transmission electron microscopy.

RESULTS

The no-PADN group had significantly higher PVSP, PVMP, pulmonary artery systolic pressure, pulmonary artery mean pressure and pulmonary vascular resistance but lower cardiac output than those of the control group (P < 0.05). Instant-PADN, 1M-PADN, 2M-PADN and 3M-PADN groups had significantly lower PVSP, PVMP, pulmonary artery systolic pressure, pulmonary artery mean pressure and pulmonary vascular resistance but higher cardiac output than those of the no-PADN group (P < 0.05). Most sympathetic nerves were located within 2.5 mm of the intimae of the bifurcation and proximal trunk, mainly in the left trunk. The diameter and cross-sectional area of myelinated fibres in the PAH group were significantly larger than those of the control group. Sympathetic nerve conduction velocity of the PAH group gradually decreased, and nerve fibres were almost demyelinated 3 months after PADN.

CONCLUSIONS

PADN effectively relieved dehydromonocrotaline-induced canine PAH and decreased sympathetic nerve conduction velocity.

A randomized placebo-control trial of the acute effects of oxygen supplementation on exercise hemodynamics, autonomic modulation, and brain oxygenation in patients with pulmonary hypertension

BACKGROUND

The integrative physiological effects of O₂ treatment on patients with pulmonary hypertension (PH) during exercise, have not been fully investigated. We simultaneously evaluated, for the first time, the effect of oxygen supplementation on hemodynamic responses, autonomic modulation, tissue oxygenation, and exercise performance in patients with pulmonary arterial hypertension (PAH)/Chronic Thromboembolic PH(CTEPH).

MATERIAL-METHODS

In this randomized, cross-over, placebo-controlled trial, stable outpatients with PAH/CTEPH underwent maximal cardiopulmonary exercise testing, followed by two submaximal trials, during which they received supplementary oxygen (O₂) or medical-air. Continuous, non-invasive hemodynamics were monitored via photophlythesmography. Cerebral and quadriceps muscle oxygenation were recorded via near-infrared spectroscopy. Autonomic function was assessed by heart rate variability; root mean square of successive differences (RMSSD) and standard-deviation-Poincare-plot (SD1) were used as indices of parasympathetic output. Baroreceptor sensitivity (BRS) was assessed throughout the protocols.

RESULTS

Nine patients (51.4 ± 9.4 years) were included. With O₂-supplementation patients exercised for longer (p = 0.01), maintained higher cerebral oxygenated hemoglobin (O₂Hb;p = 0.02) levels, exhibited an amelioration in cortical deoxygenation (HHb;p = 0.02), and had higher average cardiac output (CO) during exercise (p < 0.05), compared to medical air; with no differences in muscle oxygenation. With O₂-supplementation patients exhibited higher BRS and sample-entropy throughout the protocol (p < 0.05) vs. medical air, and improved the blunted RMSSD, SD1 responses during exercise (p = 0.024).

CONCLUSION

We show that O₂ administration improves BRS and autonomic function during submaximal exercise in PAH/CTEPH, without significantly affecting muscle oxygenation. The improved autonomic function, along with enhancements in cardiovascular function and cerebral oxygenation, probably contributes to increased exercise tolerance with O₂-supplementation in PH patients.

Chronic Thromboembolic Pulmonary Hypertension - What Have We Learned From Large Animal Models

Chronic thrombo-embolic pulmonary hypertension (CTEPH) develops in a subset of patients after acute pulmonary embolism. In CTEPH, pulmonary vascular resistance, which is initially elevated due to the obstructions in the larger pulmonary arteries, is further increased by pulmonary microvascular remodeling. The increased afterload of the right ventricle (RV) leads to RV dilation and hypertrophy. This RV remodeling predisposes to arrhythmogenesis and RV failure. Yet, mechanisms involved in pulmonary microvascular remodeling, processes underlying the RV structural and functional adaptability in CTEPH as well as determinants of the susceptibility to arrhythmias such as atrial fibrillation in the context of CTEPH remain incompletely understood. Several large animal models with critical clinical features of human CTEPH and subsequent RV remodeling have relatively recently been developed in swine, sheep, and dogs. In this review we will discuss the current knowledge on the processes underlying development and progression of CTEPH, and on how animal models can help enlarge understanding of these processes.

[11C]meta-hydroxyephedrine PET evaluation in experimental pulmonary arterial hypertension: Effects of carvedilol of right ventricular sympathetic function

BACKGROUND

Little is known about the sequelae of chronic sympathetic nervous system (SNS) activation in patients with pulmonary arterial hypertension (PAH) and right heart failure (RHF). We aimed to, (1) validate the use of [11C]-meta-hydroxyephedrine (HED) for assessing right ventricular (RV) SNS integrity, and (2) determine the effects of β-receptor blockade on ventricular function and myocardial SNS activity in a PAH rat model.

METHODS

PAH was induced in male Sprague-Dawley rats (N = 36) using the Sugen+chronic hypoxia model. At week 5 post-injection, PAH rats were randomized to carvedilol (15 mg·kg-1·day-1 oral; N = 16) or vehicle (N = 16) for 4 weeks. Myocardial SNS function was assessed with HED positron emission tomography(PET).

RESULTS

With increasing PAH disease severity, immunohistochemistry confirmed selective sympathetic denervation within the RV and sparing of parasympathetic nerves. These findings were confirmed on PET with a significant negative relationship between HED volume of distribution(DV) and right ventricular systolic pressure (RVSP) in the RV (r = -0.90, p = 0.0003). Carvedilol did not reduce hemodynamic severity compared to vehicle. RV ejection fraction (EF) was lower in both PAH groups compared to control (p < 0.05), and was not further reduced by carvedilol. Carvedilol improved SNS function in the LV with significant increases in the HED DV, and decreased tracer washout in the LV (p < 0.05) but not RV.

CONCLUSIONS

PAH disease severity correlated with a reduction in HED DV in the RV. This was associated with selective sympathetic denervation. Late carvedilol treatment did not lead to recovery of RV function. These results support the role of HED imaging in assessing SNS innervation in a failing right ventricle.

Increased Arterial Stiffness in Chronic Thromboembolic Pulmonary Hypertension Was Improved with Riociguat and Balloon Pulmonary Angioplasty: A Case Report

BACKGROUND

The role of arterial stiffness in the pathophysiology of chronic thromboembolic pulmonary hypertension (CTEPH) is unclear. The cardio-ankle vascular index (CAVI) is a novel arterial stiffness index reflecting stiffness of the arterial tree from the origin of the aorta to the ankle, independent from blood pressure at the time of measurement. CAVI reflects functional stiffness, due to smooth muscle cell contraction or relaxation, and organic stiffness, due to atherosclerosis. Here, we report the case of a patient with an increased CAVI due to CTEPH and the improvement after riociguat administration and balloon pulmonary angioplasty (BPA).

CASE PRESENTATION

A 65-year-old man suffered from dyspnea on exertion, and he was diagnosed with distal CTEPH. The mean pulmonary artery pressure (mPAP) was 51 mmHg, and the initial CAVI was 10.0, which is high for patient's age. In addition to right ventricular dysfunction, left ventricular dysfunction was observed as reduced global longitudinal strain (GLS-LV). After riociguat administration, CAVI decreased to 9.1 and GLS-LV improved from -10.3% to -17.3%, although pulmonary hypertension remained (mPAP 41 mmHg). Subsequently, a total of five BPA sessions were performed. Six months after the final BPA, mPAP decreased to 19 mmHg and GLS-LV improved to 19.3%. The patient was symptom free and his 6-minute walk distance improved from 322 m to 510 m. CAVI markedly decreased to 5.8, which is extremely low for his age.

CONCLUSION

These observations suggested that arterial stiffness as measured by CAVI was increased in CTEPH, potentially deteriorating cardiac function because of enhanced afterload. The mechanism of the increase of CAVI in this case of CTEPH was obscure; however, riociguat administration and BPA might improve the pathophysiology of CTEPH partly by decreasing CAVI.

Neurohormonal modulation in pulmonary arterial hypertension

Pulmonary hypertension is a fatal condition of elevated pulmonary pressures, complicated by right heart failure. Pulmonary hypertension appears in various forms; one of those is pulmonary arterial hypertension (PAH) and is particularly characterised by progressive remodelling and obstruction of the smaller pulmonary vessels. Neurohormonal imbalance in PAH patients is associated with worse prognosis and survival. In this back-to-basics article on neurohormonal modulation in PAH, we provide an overview of the pharmacological and nonpharmacological strategies that have been tested pre-clinically and clinically. The benefit of neurohormonal modulation strategies in PAH patients has been limited by lack of insight into how the neurohormonal system is changed throughout the disease and difficulties in translation from animal models to human trials. We propose that longitudinal and individual assessments of neurohormonal status are required to improve the timing and specificity of neurohormonal modulation strategies. Ongoing developments in imaging techniques such as positron emission tomography may become helpful to determine neurohormonal status in PAH patients in different disease stages and optimise individual treatment responses.

Increased MAO-A Activity Promotes Progression of Pulmonary Arterial Hypertension

Monoamine oxidases (MAOs), a class of enzymes bound to the outer mitochondrial membrane, are important sources of reactive oxygen species. Increased MAO-A activity in endothelial cells and cardiomyocytes contributes to vascular dysfunction and progression of left heart failure. We hypothesized that inhibition of MAO-A can be used to treat pulmonary arterial hypertension (PAH) and right ventricular (RV) failure. MAO-A levels in lung and RV samples from patients with PAH were compared with levels in samples from donors without PAH. Experimental PAH was induced in male Sprague-Dawley rats by using Sugen 5416 and hypoxia (SuHx), and RV failure was induced in male Wistar rats by using pulmonary trunk banding (PTB). Animals were randomized to receive either saline or the MAO-A inhibitor clorgyline at 10 mg/kg. Echocardiography and RV catheterization were performed, and heart and lung tissues were collected for further analysis. We found increased MAO-A expression in the pulmonary vasculature of patients with PAH and in experimental experimental PAH induced by SuHx. Cardiac MAO-A expression and activity was increased in SuHx- and PTB-induced RV failure. Clorgyline treatment reduced RV afterload and pulmonary vascular remodeling in SuHx rats through reduced pulmonary vascular proliferation and oxidative stress. Moreover, clorgyline improved RV stiffness and relaxation and reversed RV hypertrophy in SuHx rats. In PTB rats, clorgyline had no direct clorgyline had no direct effect on the right ventricle effect. Our study reveals the role of MAO-A in the progression of PAH. Collectively, these findings indicated that MAO-A may be involved in pulmonary vascular remodeling and consecutive RV failure.

Adipokines and Metabolic Regulators in Human and Experimental Pulmonary Arterial Hypertension

Pulmonary hypertension (PH) is associated with meta-inflammation related to obesity but the role of adipose tissue in PH pathogenesis is unknown. We hypothesized that adipose tissue-derived metabolic regulators are altered in human and experimental PH. We measured circulating levels of fatty acid binding protein 4 (FABP-4), fibroblast growth factor -21 (FGF-21), adiponectin, and the mRNA levels of FABP-4, FGF-21, and peroxisome proliferator-activated receptor γ (PPARγ) in lung tissue of patients with idiopathic PH and healthy controls. We also evaluated lung and adipose tissue expression of these mediators in the three most commonly used experimental rodent models of pulmonary hypertension. Circulating levels of FABP-4, FGF-21, and adiponectin were significantly elevated in PH patients compared to controls and the mRNA levels of these regulators and PPARγ were also significantly increased in human PH lungs and in the lungs of rats with experimental PH compared to controls. These findings were coupled with increased levels of adipose tissue mRNA of genes related to glucose uptake, glycolysis, tricarboxylic acid cycle, and fatty acid oxidation in experimental PH. Our results support that metabolic alterations in human PH are recapitulated in rodent models of the disease and suggest that adipose tissue may contribute to PH pathogenesis.

Parasympathetic modulation withdrawal improves functional capacity in pulmonary arterial hypertension

In 15 pulmonary arterial hypertension patients, the relation of functional capacity to their peripheral endothelial function and sympathaovagal modulation was studied by carrying out brachial artery ultrasound and electrocardiogram spectral analysis, respectively. The functional capacity was assessed by cardiopulmonary exercise testing and six-minute walking test. The sympathovagal modulation was correlated with the predicted peak oxygen consumption (peak VO₂ %; r = 0.692, P < 0.05), peak O₂ pulse (mL/beat; r = 0.661, P < 0.05), VE, minute ventilation, VCO₂ carbon dioxide production (VE/VCO₂ slope; r=-0.806, P < 0.01) and distance walked predicted (%6MWT; r = 0.694, P < 0.05). Moreover, there were negative correlations between parasympathetic modulation with peak VO₂ (r = 0.755, P < 0.01), peak VO₂% (r=-0.727, P < 0.01) and peak O₂ pulse (r = 0.615, P < 0.05), %6MWT (r=-0.834, P < 0.01). Collectively these correlations indicate that parasympathetic withdrawal is crucial for improving functional capacity. This conclusion is supported by both positive and negative correlations of parasympathetic modulation with the functional capacity parameters. The sympathetic modulation predominance, although increases the cardiovascular risk, is probably crucial to facilitate the bronchodilation and the oxygen uptake.

Pulmonary Vascular Disease as a Systemic and Multisystem Disease

Pulmonary arterial hypertension (PAH) is a disease of progressive pulmonary vascular remodeling due to abnormal proliferation of pulmonary vascular endothelial and smooth muscle cells and endothelial dysfunction. PAH is a multisystem disease with systemic manifestations and complications. This article covers the chronic heart failure syndrome, including the systemic consequences of right ventricle-pulmonary artery uncoupling and neurohormonal activation, skeletal and respiratory muscle effects, systemic endothelial dysfunction and coronary artery disease, systemic inflammation and infection, endocrine and metabolic changes, the liver and gut axis, sleep, neurologic complications, and skin and iron metabolic changes.

Neurohormonal Modulation as a Therapeutic Target in Pulmonary Hypertension

The autonomic nervous system (ANS) and renin-angiotensin-aldosterone system (RAAS) are involved in many cardiovascular disorders, including pulmonary hypertension (PH). The current review focuses on the role of the ANS and RAAS activation in PH and updated evidence of potential therapies targeting both systems in this condition, particularly in Groups 1 and 2. State of the art knowledge in preclinical and clinical use of pharmacologic drugs (beta-blockers, beta-three adrenoceptor agonists, or renin-angiotensin-aldosterone signaling drugs) and invasive procedures, such as pulmonary artery denervation, is provided.

Treatment of right ventricular dysfunction and heart failure in pulmonary arterial hypertension

Right heart dysfunction and failure is the principal determinant of adverse outcomes in patients with pulmonary arterial hypertension (PAH). In addition to right ventricular (RV) dysfunction, systemic congestion, increased afterload and impaired myocardial contractility play an important role in the pathophysiology of RV failure. The behavior of the RV in response to the hemodynamic overload is primarily modulated by the ventricular interaction and its coupling to the pulmonary circulation. The presentation can be acute with hemodynamic instability and shock or chronic producing symptoms of systemic venous congestion and low cardiac output. The prognostic factors associated with poor outcomes in hospitalized patients include systemic hypotension, hyponatremia, severe tricuspid insufficiency, inotropic support use and the presence of pericardial effusion. Effective therapeutic management strategies involve identification and effective treatment of the triggering factors, improving cardiopulmonary hemodynamics by optimization of volume to improve diastolic ventricular interactions, improving contractility by use of inotropes, and reducing afterload by use of drugs targeting pulmonary circulation. The medical therapies approved for PAH act primarily on the pulmonary vasculature with secondary effects on the right ventricle. Mechanical circulatory support as a bridge to transplantation has also gained traction in medically refractory cases. The current review was undertaken to summarize recent insights into the evaluation and treatment of RV dysfunction and failure attributable to PAH.

Emerging therapies for right ventricular dysfunction and failure

Therapeutic options for right ventricular (RV) dysfunction and failure are strongly limited. Right heart failure (RHF) has been mostly addressed in the context of pulmonary arterial hypertension (PAH), where it is not possible to discern pulmonary vascular- and RV-directed effects of therapeutic approaches. In part, opposing pathomechanisms in RV and pulmonary vasculature, i.e., regarding apoptosis, angiogenesis and proliferation, complicate addressing RHF in PAH. Therapy effective for left heart failure is not applicable to RHF, e.g., inhibition of adrenoceptor signaling and of the renin-angiotensin system had no or only limited success. A number of experimental studies employing animal models for PAH or RV dysfunction or failure have identified beneficial effects of novel pharmacological agents, with most promising results obtained with modulators of metabolism and reactive oxygen species or inflammation, respectively. In addition, established PAH agents, in particular phosphodiesterase-5 inhibitors and soluble guanylate cyclase stimulators, may directly address RV integrity. Promising results are furthermore derived with microRNA (miRNA) and long non-coding RNA (lncRNA) blocking or mimetic strategies, which can target microvascular rarefaction, inflammation, metabolism or fibrotic and hypertrophic remodeling in the dysfunctional RV. Likewise, pre-clinical data demonstrate that cell-based therapies using stem or progenitor cells have beneficial effects on the RV, mainly by improving the microvascular system, however clinical success will largely depend on delivery routes. A particular option for PAH is targeted denervation of the pulmonary vasculature, given the sympathetic overdrive in PAH patients. Finally, acute and durable mechanical circulatory support are available for the right heart, which however has been tested mostly in RHF with concomitant left heart disease. Here, we aim to review current pharmacological, RNA- and cell-based therapeutic options and their potential to directly target the RV and to review available data for pulmonary artery denervation and mechanical circulatory support.