Atrial Septostomy Decreases Sympathetic Overactivity in Pulmonary Arterial Hypertension

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.

Outcomes of atrial septostomy and effect on long-term survival in patients with idiopathic pulmonary arterial hypertension: A single-center cohort

OBJECTIVE

Pulmonary arterial hypertension (PAH) is a chronic progressive disease that may lead to right heart failure (RHF) and early death. Balloon atrial septostomy (BAS) may be used for the palliative treatment of RHF from PAH. We present our contemporary institutional experience of utilizing BAS in idiopathic PAH (IPAH) patients with refractory RHF to investigate the effect on the safety, efficacy and long-term survival.

METHODS

This retrospective analysis included 12 IPAH patients with severe RHF from March 2017 to May 2019 who were assessed as high risk. All patients received standard treatment including combination of PAH-specific drugs. Graded BAS was performed on these patients due to unsatisfactory clinical response. Clinical, functional and hemodynamic variables before and immediately after the procedure were collected. 1-year follow-up outcomes and 3-year survival rate were further analyzed.

RESULTS

Successful septostomy was achieved in cases with no procedure-related complications. All patients obtained hemodynamic improvement immediately after the procedure. The WHO functional class and exercise endurance improved at 1-year follow-up, 7 of 12 patients achieved intermediate-low risk status, while the rest remained at intermediate-high risk. 2 patients died at 18 and 20 months due to malignant arrhythmia and advanced heart failure, respectively. Survival at 1 year and 3 years was 100% and 83.3%.

CONCLUSIONS

In selected IPAH patients with refractory RHF, BAS is an additional therapeutic strategy, especially when PAH-specific drugs could not achieve the treatment target. BAS can improve hemodynamic variables, bring clinical and cardiac functional benefits and increase the 3-year survival.

Is combined use of radiofrequency ablation and balloon dilation the future of interatrial communications?

INTRODUCTION

Personalized and stable interatrial communication is an important palliative therapy for patients with heart failure. However, this remains a technically challenging task.

AREAS COVERED

In the past decades, substantial advancements in atrial septostomy for the creation of controllable and durable interatrial communication have been made, and numerous novel devices and techniques are in various stages of development. In this review, we discuss the evolving indications for atrial septostomy, current approaches with or without device implantation, and indicators for optimal interatrial communication. The combined use of radiofrequency ablation and balloon dilation (CURB) is an individualized management approach based on underlying hemodynamics, which demonstrates unique advantages in creating a sufficient interatrial communication with satisfactory stability. The advantages and disadvantages of this implant-free procedure are analyzed and its clinical prospects are assessed.

EXPERT OPINION

With ready availability, high safety, and efficacy, CURB is a promising procedure for creating personalized and stable interatrial communication without device implantation. Further research is required to simplify the procedure, screen optimal reference parameters for personalized therapy, and evaluate the long-term outcome in a large population of patients.

Excess ventilation and exertional dyspnoea in heart failure and pulmonary hypertension

Increased ventilation relative to metabolic demands, indicating alveolar hyperventilation and/or increased physiological dead space (excess ventilation), is a key cause of exertional dyspnoea. Excess ventilation has assumed a prominent role in the functional assessment of patients with heart failure (HF) with reduced (HFrEF) or preserved (HFpEF) ejection fraction, pulmonary arterial hypertension (PAH) and chronic thromboembolic pulmonary hypertension (CTEPH). We herein provide the key pieces of information to the caring physician to 1) gain unique insights into the seeds of patients' shortness of breath and 2) develop a rationale for therapeutically lessening excess ventilation to mitigate this distressing symptom. Reduced bulk oxygen transfer induced by cardiac output limitation and/or right ventricle-pulmonary arterial uncoupling increase neurochemical afferent stimulation and (largely chemo-) receptor sensitivity, leading to alveolar hyperventilation in HFrEF, PAH and small-vessel, distal CTEPH. As such, interventions geared to improve central haemodynamics and/or reduce chemosensitivity have been particularly effective in lessening their excess ventilation. In contrast, 1) high filling pressures in HFpEF and 2) impaired lung perfusion leading to ventilation/perfusion mismatch in proximal CTEPH conspire to increase physiological dead space. Accordingly, 1) decreasing pulmonary capillary pressures and 2) mechanically unclogging larger pulmonary vessels (pulmonary endarterectomy and balloon pulmonary angioplasty) have been associated with larger decrements in excess ventilation. Exercise training has a strong beneficial effect across diseases. Addressing some major unanswered questions on the link of excess ventilation with exertional dyspnoea under the modulating influence of pharmacological and nonpharmacological interventions might prove instrumental to alleviate the devastating consequences of these prevalent diseases.

Interventionelle Behandlungsverfahren der pulmonalen Hypertension im Kindesalter

Die pulmonale Hypertension (PH) ist eine progressive Gefäßerkrankung und führt über eine Widerstands- und/oder Druckerhöhung im kleinen Kreislauf zu einem fortschreitenden Rechtsherzversagen. Auch wenn mithilfe aktueller medikamentöser Therapien eine deutliche Verbesserung der Lebensqualität und des Überlebens der Betroffenen erreicht werden konnte, bleibt die PH eine zumeist nichtheilbare Erkrankung, die im fortgeschrittenen Stadium eine Lungentransplantation notwendig macht. Interventionelle Verfahren, wie die Anlage eines interatrialen Shunts (z. B. durch atriale Septostomie oder den Atrial Flow Regulator) oder eines Reversed Potts Shunt, verbessern die RV-Funktion und die ventrikuläre Interaktion durch Schaffung einer prä- oder posttrikuspidalen „Eisenmenger-Physiologie“ und stellen eine Überbrückung oder sogar Alternative zur Lungentransplantation dar. Bei Patienten mit segmentaler PH oder chronisch thrombembolischer pulmonaler Hypertension (CTEPH) stellt die Ballonangioplastie eine bereits etablierte Intervention zur Verbesserung der pulmonalen Perfusion und damit rechtsventrikulären (RV-)Funktion dar. Dagegen ist die pulmonalarterielle Denervation ein neuartiges Verfahren, mit dem Ziel, die neurohumorale Dysregulation bei PH positiv zu beeinflussen. Der individuelle Einsatz solcher Interventionen, additiv zu den bereits etablierten medikamentösen Therapien, erweitert die Behandlungsmöglichkeiten und kann die Prognose betroffener Patienten noch weiter verbessern.

Sympathetic and Vagal Nerve Activity in COPD: Pathophysiology, Presumed Determinants and Underappreciated Therapeutic Potential

This article explains the comprehensive state of the art assessment of sympathetic (SNA) and vagal nerve activity recordings in humans and highlights the precise mechanisms mediating increased SNA and its corresponding presumed clinical determinants and therapeutic potential in the context of chronic obstructive pulmonary disease (COPD). It is known that patients with COPD exhibit increased muscle sympathetic nerve activity (MSNA), as measured directly using intraneural microelectrodes—the gold standard for evaluation of sympathetic outflow. However, the underlying physiological mechanisms responsible for the sympathoexcitation in COPD and its clinical relevance are less well understood. This may be related to the absence of a systematic approach to measure the increase in sympathetic activity and the lack of a comprehensive approach to assess the underlying mechanisms by which MSNA increases. The nature of sympathoexcitation can be dissected by distinguishing the heart rate increasing properties (heart rate and blood pressure variability) from the vasoconstrictive drive to the peripheral vasculature (measurement of catecholamines and MSNA) (Graphical Abstract Figure 1). Invasive assessment of MSNA to the point of single unit recordings with analysis of single postganglionic sympathetic firing, and hence SNA drive to the peripheral vasculature, is the gold standard for quantification of SNA in humans but is only available in a few centres worldwide because it is costly, time consuming and requires a high level of training. A broad picture of the underlying pathophysiological determinants of the increase in sympathetic outflow in COPD can only be determined if a combination of these tools are used. Various factors potentially determine SNA in COPD (Graphical Abstract Figure 1): Obstructive sleep apnoea (OSA) is highly prevalent in COPD, and leads to repeated bouts of upper airway obstructions with hypoxemia, causing repetitive arousals. This probably produces ongoing sympathoexcitation in the awake state, likely in the “blue bloater” phenotype, resulting in persistent vasoconstriction. Other variables likely describe a subset of COPD patients with increase of sympathetic drive to the heart, clinically likely in the “pink puffer” phenotype. Pharmacological treatment options of increased SNA in COPD could comprise beta blocker therapy. However, as opposed to systolic heart failure a similar beneficial effect of beta blocker therapy in COPD patients has not been shown. The point is made that although MSNA is undoubtedly increased in COPD (probably independently from concomitant cardiovascular disease), studies designed to determine clinical improvements during specific treatment will only be successful if they include adequate patient selection and translational state of the art assessment of SNA. This would ideally include intraneural recordings of MSNA and—as a future perspective—vagal nerve activity all of which should ideally be assessed both in the upright and in the supine position to also determine baroreflex function.

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

Advanced Surgical and Percutaneous Approaches to Pulmonary Vascular Disease

Despite progress in modern medical therapy, pulmonary hypertension remains an unremitting disease. Once severe or refractory to medical therapy, advanced percutaneous and surgical interventions can palliate right ventricular overload, bridge to transplantation, and overall extend a patient's course. These approaches include atrial septostomy, Potts shunt, and extracorporeal life support. Bilateral lung transplantation is the ultimate treatment for eligible patients, although the need for suitable lungs continues to outpace availability. Measures such as ex vivo lung perfusion are ongoing to expand donor lung availability, increase rates of transplant, and decrease waitlist mortality.

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.

Study of the effect of Occlutech Atrial Flow Regulator on symptoms, hemodynamics, and echocardiographic parameters in advanced pulmonary arterial hypertension

Optimal sized balloon atrial septostomy improves hemodynamics in advanced pulmonary arterial hypertension. Occlutech Atrial Flow Regulator is designed to provide an atrial septal fenestration diameter titrated according to the age and right atrial pressures. This observational study analyzed symptoms, exercise distance, oxygen saturations, hemodynamics and echocardiographic parameters after Atrial Flow Regulator implantation in patients with syncope or right-heart failure. Patients with high-risk predictors of mortality during septostomy were scrutinized. Thirty-nine patients (9 children) with syncope (34/39) or right-heart failure (27/39) underwent Atrial Flow Regulator implantation without procedural complications. Six-minute walk distance increased from 310 ± 158.2 to 376.4 ± 182.6 m, none developed syncope. Oxygen saturations reduced from 96.4 ± 6.4% to 92 ± 4.9% at rest and further to 80.3 ± 5.9% on exercise. Right atrial pressures reduced from 9.4 ± 5 (2-27) mmHg to 6.9 ± 2.6 (1-12) mmHg, while cardiac index increased from 2.4 ± 0.8 (0.98-4.3) to 3 ± 1 (1.1-5.3) L/min/m² and systemic oxygen transport increased from 546.1 ± 157.9 (256.2-910.5) to 637.2 ± 191.1 (301.3-1020.2) ml/min. Echocardiographic improvement included significant reduction of pericardial effusion and inferior caval congestion at a median follow-up of 37 months. Overall survival improved except two early and one late deaths in high-risk patients. Five of seven patients with advanced disease and key hemodynamic predictors of mortality survived. Acute hemodynamic benefits in pulmonary arterial hypertension after Atrial Flow Regulator were improved cardiac output, systemic oxygen transport, and reduced right atrial pressures. Improvement of symptoms especially syncope, exercise duration, and right ventricular systolic function as well as device patency were sustained on mid-term follow-up. Implantation was safe in all including young children without procedural complications. Mortality was noted only in patients who had high-risk predictors and patients at advanced stage of the disease.

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.

The evolving role of interventional cardiology in the treatment of pulmonary hypertension

Pulmonary hypertension (PH) is a heterogeneous group of diseases defined by a mean pulmonary arterial pressure greater than 20 mmHg. Clinically, PH is classified into five groups and the group of PH generally defines the cause of PH and the therapeutic options. Currently, medical therapies that target the prostacyclin, endothelin, and nitric oxide pathways are used in pulmonary arterial hypertension and chronic thromboembolic PH (CTEPH) patients. Moreover, surgery can improve outcomes in PH as pulmonary thromboendarterectomy can be curative for CTEPH and lung transplantation is used for end-stage PH. Despite these diverse treatment options, PH patients continue to have high symptom burden and poor long-term outcomes. However, advances in percutaneous technology are opening new avenues for the management of PH. In this review, we discuss the available data supporting the use of four interventional procedures: balloon atrial septostomy, transcatheter Potts shunt, balloon pulmonary angioplasty, and pulmonary artery denervation for the treatment of PH. These procedures provide hemodynamic and functional improvements in PH patients, but they come with their own unique risk profiles. Hopefully, these procedures will continue to be refined and thereby provide a venue for interventional cardiology to safely and effectively improve outcomes for PH moving forward.

Pulmonary artery denervation for pulmonary arterial hypertension

Pulmonary arterial hypertension remains a progressive, life-limiting disease despite optimal medical therapy. Pulmonary artery denervation has arisen as a novel intervention in the treatment of pulmonary arterial hypertension, and other forms of pulmonary hypertension, with the aim of reducing the sympathetic activity of the pulmonary circulation. Pre-clinical studies and initial clinical trials have demonstrated that the technique can be performed safely with some positive effects on clinical, haemodynamic and echocardiographic markers of disease. The scope of the technique in current practice remains limited given the absence of well-designed, large-scale, international randomised controlled clinical trials. This review provides an overview of this exciting new treatment modality, including pathophysiology, technical innovations and recent trial results.

Impaired right ventricular lusitropy is associated with ventilatory inefficiency in pulmonary arterial hypertension

Cardiopulmonary exercise testing (CPET) is an important tool for assessing functional capacity and prognosis in pulmonary arterial hypertension (PAH). However, the associations of CPET parameters with the adaptation of right ventricular (RV) function to afterload remain incompletely understood.In this study, 37 patients with PAH (idiopathic in 31 cases) underwent single-beat pressure-volume loop measurements of RV end-systolic elastance (Ees), arterial elastance (Ea) and diastolic elastance (Eed). Pulmonary arterial stiffness was assessed by magnetic resonance imaging. The results were correlated to CPET variables. The predictive relevance of RV function parameters for clinically relevant ventilatory inefficiency, defined as minute ventilation/carbon dioxide production (V' _E/V' _CO2 ) slope >48, was evaluated using logistic regression analysis.The median (interquartile range) of the V' _E/V' _CO2 slope was 42 (32-52) and the V' _E/V' _CO2 nadir was 40 (31-44). The mean±sd of peak end-tidal carbon dioxide tension (P _ETCO2 ) was 23±8 mmHg. Ea, Eed and parameters reflecting pulmonary arterial stiffness (capacitance and distensibility) correlated with the V' _E/V' _CO2 slope, V' _E/V' _CO2 nadir, P _ETCO2 and peak oxygen pulse. RV Ees and RV-arterial coupling as assessed by the Ees/Ea ratio showed no correlations with CPET parameters. Ea (univariate OR 7.28, 95% CI 1.20-44.04) and Eed (univariate OR 2.21, 95% CI 0.93-5.26) were significantly associated with ventilatory inefficiency (p<0.10).Our data suggest that impaired RV lusitropy and increased afterload are associated with ventilatory inefficiency in PAH.

Use of Balloon Atrial Septostomy in Patients With Advanced Pulmonary Arterial Hypertension: A Systematic Review and Meta-Analysis

BACKGROUND

Despite the use and purported benefits of balloon atrial septostomy (BAS), its safety, efficacy, and therapeutic role in the setting of advanced pulmonary arterial hypertension (PAH) are not well defined.

OBJECTIVE

The goal of this study was to conduct a systematic review and meta-analysis to better determine the evidence supporting the use of BAS in PAH.

METHODS

MEDLINE, Scopus, Cochrane Library, and Clinicaltrials.gov were searched from inception through May 2018 for original studies reporting outcomes with PAH prior to and following BAS. Studies comparing BAS vs other septostomy procedures were excluded. Weighted mean differences and 95% CIs were pooled by using a random effects model.

RESULTS

Sixteen studies comprising 204 patients (mean age, 35.8 years; 73.1% women) were included. Meta-analysis revealed significant reductions in right atrial pressure (-2.77 mm Hg [95% CI, -3.50, -2.04]; P < .001) and increases in cardiac index (0.62 L/min/m² [95% CI, 0.48, 0.75]; P < .001) and left atrial pressure (1.86 mm Hg [95% CI, 1.24, 2.49]; P < .001) following BAS, along with a significant reduction in arterial oxygen saturation (-8.45% [95% CI, -9.93, -6.97]; P < .001). The pooled incidence of procedure-related (48 h), short-term (≤ 30 day), and long-term (> 30 days up to a mean follow-up of 46.5 months) mortality was 4.8% (95% CI, 1.7%, 9.0%), 14.6% (95% CI, 8.6%, 21.5%), and 37.7% (95% CI, 27.9%, 47.9%), respectively.

CONCLUSIONS

The present analysis suggests that BAS is relatively safe in advanced PAH, with beneficial hemodynamic effects. The relatively high postprocedural and short-term survival with less impressive long-term survival suggest a bridging role for BAS; its contribution to this change needs to be verified by using a comparator group.

Treatment strategies for the right heart in pulmonary hypertension

The function of the right ventricle (RV) determines the prognosis of patients with pulmonary hypertension. While much progress has been made in the treatment of pulmonary hypertension, therapies for the RV are less well established. In this review of treatment strategies for the RV, first we focus on ways to reduce wall stress since this is the main determinant of changes to the ventricle. Secondly, we discuss treatment strategies targeting the detrimental consequences of increased RV wall stress. To reduce wall stress, afterload reduction is the essential. Additionally, preload to the ventricle can be reduced by diuretics, by atrial septostomy, and potentially by mechanical ventricular support. Secondary to ventricular wall stress, left-to-right asynchrony, altered myocardial energy metabolism, and neurohumoral activation will occur. These may be targeted by optimising RV contraction with pacing, by iron supplement, by angiogenesis and improving mitochondrial function, and by neurohumoral modulation, respectively. We conclude that several treatment strategies for the right heart are available; however, evidence is still limited and further research is needed before clinical application can be recommended.

Interventional Therapies in Pulmonary Hypertension

Despite advances in drug therapy, pulmonary hypertension-particularly arterial hypertension (PAH)-remains a fatal disease. Untreatable right heart failure (RHF) from PAH eventually ensues and remains a significant cause of death in these patients. Lowering pulmonary input impedance with different PAH-specific drugs is the obvious therapeutic target in RHF due to chronically increased afterload. However, potential clinical gain can also be expected from attempts to unload the right heart and increase systemic output. Atrial septostomy, Potts anastomosis, and pulmonary artery denervation are interventional procedures serving this purpose. Percutaneous balloon pulmonary angioplasty, another interventional therapy, has re-emerged in the last few years as a clear alternative for the management of patients with distal, inoperable, chronic thromboembolic pulmonary hypertension. The current review discusses the physiological background, experimental evidence, and potential clinical and hemodynamic benefits of all these interventional therapies regarding their use in the setting of RHF due to severe pulmonary hypertension.

Ventilatory response to exercise in cardiopulmonary disease: the role of chemosensitivity and dead space

The lungs and heart are irrevocably linked in their oxygen (O₂) and carbon dioxide (CO₂) transport functions. Functional impairment of the lungs often affects heart function and vice versa The steepness with which ventilation (V'_E) rises with respect to CO₂ production (V'_CO2 ) (i.e. the V'_E/V'_CO2 slope) is a measure of ventilatory efficiency and can be used to identify an abnormal ventilatory response to exercise. The V'_E/V'_CO2 slope is a prognostic marker in several chronic cardiopulmonary diseases independent of other exercise-related variables such as peak O₂ uptake (V'_O2 ). The V'_E/V'_CO2 slope is determined by two factors: 1) the arterial CO₂ partial pressure (P_aCO2 ) during exercise and 2) the fraction of the tidal volume (V_T) that goes to dead space (V_D) (i.e. the physiological dead space ratio (V_D/V_T)). An altered P_aCO2 set-point and chemosensitivity are present in many cardiopulmonary diseases, which influence V'_E/V'_CO2 by affecting P_aCO2 Increased ventilation-perfusion heterogeneity, causing inefficient gas exchange, also contributes to the abnormal V'_E/V'_CO2 observed in cardiopulmonary diseases by increasing V_D/V_T During cardiopulmonary exercise testing, the P_aCO2 during exercise is often not measured and V_D/V_T is only estimated by taking into account the end-tidal CO₂ partial pressure (P_ETCO2 ); however, P_aCO2 is not accurately estimated from P_ETCO2 in patients with cardiopulmonary disease. Measuring arterial gases (P_aO2 and P_aCO2 ) before and during exercise provides information on the real (and not "estimated") V_D/V_T coupled with a true measure of gas exchange efficiency such as the difference between alveolar and arterial O₂ partial pressure and the difference between arterial and end-tidal CO₂ partial pressure during exercise.

Excess Ventilation in Chronic Obstructive Pulmonary Disease-Heart Failure Overlap. Implications for Dyspnea and Exercise Intolerance

RATIONALE

An increased ventilatory response to exertional metabolic demand (high [Formula: see text]e/[Formula: see text]co₂ relationship) is a common finding in patients with coexistent chronic obstructive pulmonary disease and heart failure.

OBJECTIVES

We aimed to determine the mechanisms underlying high [Formula: see text]e/[Formula: see text]co₂ and its impact on operating lung volumes, dyspnea, and exercise tolerance in these patients.

METHODS

Twenty-two ex-smokers with combined chronic obstructive pulmonary disease and heart failure with reduced left ventricular ejection fraction undertook, after careful treatment optimization, a progressive cycle exercise test with capillary (c) blood gas collection.

MEASUREMENTS AND MAIN RESULTS

Regardless of the chosen metric (increased [Formula: see text]e-[Formula: see text]co₂ slope, [Formula: see text]e/[Formula: see text]co₂ nadir, or end-exercise [Formula: see text]e/[Formula: see text]co₂), ventilatory inefficiency was closely related to Pc_CO2 (r values from -0.80 to -0.84; P < 0.001) but not dead space/tidal volume ratio. Ten patients consistently maintained exercise Pc_CO2 less than or equal to 35 mm Hg (hypocapnia). These patients had particularly poor ventilatory efficiency compared with patients without hypocapnia (P < 0.05). Despite the lack of between-group differences in spirometry, lung volumes, and left ventricular ejection fraction, patients with hypocapnia had lower resting Pa_CO2 and lung diffusing capacity (P < 0.01). Excessive ventilatory response in this group was associated with higher exertional Pc_O2. The group with hypocapnia, however, had worse mechanical inspiratory constraints and higher dyspnea scores for a given work rate leading to poorer exercise tolerance compared with their counterparts (P < 0.05).

CONCLUSIONS

Heightened neural drive promoting a ventilatory response beyond that required to overcome an increased "wasted" ventilation led to hypocapnia and poor exercise ventilatory efficiency in chronic obstructive pulmonary disease-heart failure overlap. Excessive ventilation led to better arterial oxygenation but at the expense of earlier critical mechanical constraints and intolerable dyspnea.

Cardiopulmonary rehabilitation program impact on prognostic markers in selected patients with resting and exercise-induced ventilatory inefficiency: a clinical trial

[Purpose] Ventilatory limitation is a common problem in patients with chronic heart failure and pulmonary hypertension. Excess ventilation may arise from augmented ventilatory drive, over activity of chemoreceptors and muscle ergoreceptors, or premature onset of lactic acidosis. Exertional dyspnea can cause limitations in the activities of daily living and as a result, reduced quality of life for these patients. The aim of the present study was to evaluate the effect of cardiopulmonary rehabilitation program on ventilatory efficiency for these patients. [Subjects and Methods] Twenty five patients with chronic heart failure and twenty five patients with pulmonary hypertension and only forty of them completed the study. The training program consisted of interval aerobic training program, based on the results of cardiopulmonary exercise testing. Training period was about five months. Outcomes were ventilatory equivalent for CO2, (VE/VCO2 at anaerobic threshold), VO2 at anaerobic threshold, VO2 max and peak work load. Echocardiography parameters were also measured; right ventricular systolic pressure for patients with pulmonary hypertension and ejection fraction for patients with chronic heart failure. [Results] Both groups showed an improvement in ventilation during exercise in favor of patients with pulmonary hypertension. VE/VCO2 decreased by 6.65 in pulmonary hypertension and by 2.9 in chronic heart failure. Right ventricular systolic pressure decreased by 12.05 mmHg in pulmonary hypertension and ejection fraction increased by 17.74% in chronic heart failure. [Conclusion] Physical therapy cardiopulmonary rehabilitation should be considered in managing patients with ventilatory limitation such as pulmonary hypertension and chronic heart failure.

Incremental shuttle walk test distance and autonomic dysfunction predict survival in pulmonary arterial hypertension

BACKGROUND

To ensure effective monitoring of pulmonary arterial hypertension (PAH), a simple, reliable assessment of exercise capacity applicable over a range of disease severity is needed. The aim of this study was to assess the ability of the incremental shuttle walk test (ISWT) to correlate with disease severity, measure sensitivity to change, and predict survival in PAH.

METHODS

We enrolled 418 treatment-naïve patients with PAH with baseline ISWT within 3 months of cardiac catheterization. Clinical validity and prognostic value of ISWT distance were assessed at baseline and 1 year.

RESULTS

ISWT distance was found to correlate at baseline with World Health Organization functional class, Borg score, and hemodynamics without a ceiling effect (all p < 0.001). Walking distance at baseline and after treatment predicted survival; the area under the receiver operating characteristic curve for ability of ISWT distance to predict mortality was 0.655 (95% confidence interval 0.553-0.757; p = 0.004) at baseline and 0.737 (95% confidence interval 0.643-0.827; p < 0.001) at 1 year after initiation of treatment. Change in ISWT distance also predicted survival (p = 0.04). Heart rate (HR) and systolic blood pressure (SBP) parameters reflecting autonomic response to exercise (highest HR, change in HR, HR recovery at 1 minute >18 beats/min, highest SBP, change in SBP, and 3-minute SBP ratio) were significant predictors of survival (all p < 0.05).

CONCLUSIONS

In patients with PAH, the ISWT is simple to perform, allows assessment of maximal exercise capacity, is sensitive to treatment effect, predicts outcome, and has no ceiling effect. Also, measures of autonomic function made post-exercise predict survival in PAH.

Kidney dysfunction in patients with pulmonary arterial hypertension

Pulmonary arterial hypertension (PH) and chronic kidney disease (CKD) both profoundly impact patient outcomes, whether as primary disease states or as co-morbid conditions. PH is a common co-morbidity in CKD and vice versa. A growing body of literature describes the epidemiology of PH secondary to chronic kidney disease and end-stage renal disease (ESRD) (WHO group 5 PH). But, there are only limited data on the epidemiology of kidney disease in group 1 PH (pulmonary arterial hypertension [PAH]). The purpose of this review is to summarize the current data on epidemiology and discuss potential disease mechanisms and management implications of kidney dysfunction in PAH. Kidney dysfunction, determined by serum creatinine or estimated glomerular filtration rate, is a frequent co-morbidity in PAH and impaired kidney function is a strong and independent predictor of mortality. Potential mechanisms of PAH affecting the kidneys are increased venous congestion, decreased cardiac output, and neurohormonal activation. On a molecular level, increased TGF-β signaling and increased levels of circulating cytokines could have the potential to worsen kidney function. Nephrotoxicity does not seem to be a common side effect of PAH-targeted therapy. Treatment implications for kidney disease in PAH include glycemic control, lifestyle modification, and potentially Renin-Angiotensin-Aldosterone System (RAAS) blockade.

Pulmonary hypertension and ventilation during exercise: Role of the pre-capillary component

BACKGROUND

Excessive exercise-induced hyperventilation and high prevalence of exercise oscillatory breathing (EOB) are present in patients with post-capillary pulmonary hypertension (PH) complicating left heart disease (LHD). Patients with pre-capillary PH have even higher hyperventilation but no EOB. We sought to determine the impact of a pre-capillary component of PH on ventilatory response to exercise in patients with PH and left heart disease.

METHODS

We retrospectively compared patients with idiopathic or heritable pulmonary arterial hypertension (PAH, n = 29), isolated post-capillary PH (IpcPH, n = 29), and combined post- and pre-capillary PH (CpcPH, n = 12). Diastolic pressure gradient (DPG = diastolic pulmonary artery pressure - pulmonary wedge pressure) was used to distinguish IpcPH (DPG <7 mm Hg) from CpcPH (DPG ≥7 mm Hg).

RESULTS

Pulmonary vascular resistance (PVR) was higher in PAH, intermediate in CpcPH, and low in IpcPH. All patients with CpcPH but 1 had PVR >3 Wood unit. Exercise-induced hyperventilation (high minute ventilation over carbon dioxide production, low end-tidal carbon dioxide) was marked in PAH, intermediate in CpcPH, and low in IpcPH (p < 0.001) and correlated with DPG and PVR. Prevalence of EOB decreased from IpcPH to CpcPH to PAH (p < 0.001).

CONCLUSIONS

Patients with CpcPH may have worse hemodynamics than patients with IpcPH and distinct alterations of ventilatory control, consistent with more exercise-induced hyperventilation and less EOB. This might be explained at least in part by the presence and extent of pulmonary vascular disease.

Pericardial effusion is correlated with clinical outcome after pulmonary artery denervation for pulmonary arterial hypertension

Objectives

Pericardial effusion (PE) is correlated with outcomes in patients with pulmonary arterial hypertension (PAH). Pulmonary artery denervation (PADN) was used for treatment of PAH. The present study aimed to analyze the prognostic value of PE for outcomes after PADN in patients with WHO Group I, Group II and Group IV PAH.

Results

PE, frequently seen in patients with connective tissue disease, was featured by fast heart rate, decreased exercise capacity, more syncope, worsening pulmonary arterial hemodynamic and right atrium size. PADN procedure resulted in dramatic reduction of PE. After a median of 376 days follow-up, the rate of PAH-related event, all-cause death and rehospitalization increased over the PE amount and occurred in 29.8%, 19.7% and 25.2% of patients with PE, different to 3.4%, 3.4% and 6.8% of patients without PE (p = 0.034, p = 0.041 and p = 0.039, respectively). The reduction of PE during follow-up was similar among three groups.

Materials and methods

Between March 2012 and July 2014, a total of 66 consecutive patients (52 ± 16 years) who underwent PADN were stratified by no PE (n = 20), PE < 10 mm (n = 29) and PE ≥ 10 mm (n = 17) according to baseline echocardiograph. Dynamic change of PE and its correlation with PAH-related event after PADN were measured.

Conclusions

PE is associated with increased PAH-related event after PADN. PADN results in significant similar reduction of PE among patients with Group I, Group II and Group IV PAH.

Obstructive Ventilatory Disorder in Heart Failure-Caused by the Heart or the Lung?

Heart failure (HF) is a clinical syndrome frequently associated with airway obstruction, either as a respiratory comorbidity or as a direct consequence of HF pathophysiology. Recognizing the relative contribution of an underlying airway disease as opposed to airway obstruction due to volume overload and left atrial pressure elevation is of importance for the appropriate management of patients affected by HF. This review focuses on "les liaisons dangereuses" between the heart and the lungs, outlying recent advances linking in a vicious circle of chronic obstructive lung disease (COPD) and obstructive sleep apnea (OSA) on one side and HF on the other side. It also discusses the role of pivotal diagnostic tools such as pulmonary function tests and cardiopulmonary exercise test to determine the contribution of HF and COPD to symptoms and clinical status. Treatment implications are discussed as well.

The von Hippel-Lindau Chuvash mutation in mice alters cardiac substrate and high-energy phosphate metabolism

This is the first integrative metabolic and functional study of the effects of modest hypoxia-inducible factor manipulation within the heart. Of particular note, the combination (and correlation) of perfused heart metabolic flux measurements with the new technique of real-time in vivo magnetic resonance spectroscopy using hyperpolarized pyruvate is a novel development.

Hypoxia-inducible factor (HIF) appears to function as a global master regulator of cellular and systemic responses to hypoxia. HIF pathway manipulation is of therapeutic interest; however, global systemic upregulation of HIF may have as yet unknown effects on multiple processes. We used a mouse model of Chuvash polycythemia (CP), a rare genetic disorder that modestly increases expression of HIF target genes in normoxia, to understand what these effects might be within the heart. An integrated in and ex vivo approach was employed. Compared with wild-type controls, CP mice had evidence (using in vivo magnetic resonance imaging) of pulmonary hypertension, right ventricular hypertrophy, and increased left ventricular ejection fraction. Glycolytic flux (measured using [³H]glucose) in the isolated contracting perfused CP heart was 1.8-fold higher. Net lactate efflux was 1.5-fold higher. Furthermore, in vivo ¹³C-magnetic resonance spectroscopy (MRS) of hyperpolarized [¹³C₁]pyruvate revealed a twofold increase in real-time flux through lactate dehydrogenase in the CP hearts and a 1.6-fold increase through pyruvate dehydrogenase. ³¹P-MRS of perfused CP hearts under increased workload (isoproterenol infusion) demonstrated increased depletion of phosphocreatine relative to ATP. Intriguingly, no changes in cardiac gene expression were detected. In summary, a modest systemic dysregulation of the HIF pathway resulted in clear alterations in cardiac metabolism and energetics. However, in contrast to studies generating high HIF levels within the heart, the CP mice showed neither the predicted changes in gene expression nor any degree of LV impairment. We conclude that the effects of manipulating HIF on the heart are dose dependent.

Novel Therapeutic Strategies for Reducing Right Heart Failure Associated Mortality in Fibrotic Lung Diseases

Fibrotic lung diseases carry a significant mortality burden worldwide. A large proportion of these deaths are due to right heart failure and pulmonary hypertension. Underlying contributory factors which appear to play a role in the mechanism of progression of right heart dysfunction include chronic hypoxia, defective calcium handling, hyperaldosteronism, pulmonary vascular alterations, cyclic strain of pressure and volume changes, elevation of circulating TGF-β, and elevated systemic NO levels. Specific therapies targeting pulmonary hypertension include calcium channel blockers, endothelin (ET-1) receptor antagonists, prostacyclin analogs, phosphodiesterase type 5 (PDE5) inhibitors, and rho-kinase (ROCK) inhibitors. Newer antifibrotic and anti-inflammatory agents may exert beneficial effects on heart failure in idiopathic pulmonary fibrosis. Furthermore, right ventricle-targeted therapies, aimed at mitigating the effects of functional right ventricular failure, include β-adrenoceptor (β-AR) blockers, angiotensin-converting enzyme (ACE) inhibitors, antioxidants, modulators of metabolism, and 5-hydroxytryptamine-2B (5-HT2B) receptor antagonists. Newer nonpharmacologic modalities for right ventricular support are increasingly being implemented. Early, effective, and individualized therapy may prevent overt right heart failure in fibrotic lung disease leading to improved outcomes and quality of life.

Treatment for pulmonary arterial hypertension-associated right ventricular dysfunction

Pulmonary arterial hypertension (PAH) includes a heterogeneous group of diseases characterized by pulmonary vasoconstriction and remodeling of the lung circulation. Although PAH is a disease of the lungs, patients with PAH frequently die of right heart failure. Indeed, survival of patients with PAH depends on the adaptive response of the right ventricle (RV) to the changes in the lung circulation. PAH-specific drugs affect the function of the RV through afterload reduction and perhaps also through direct effects on the myocardium. Prostacyclins, type 5 phosphodiesterase inhibitors, and guanylyl cyclase stimulators may directly enhance myocardial contractility through increased cyclic adenosine and guanosine monophosphate availability. Although this may initially improve cardiac performance, the long-term effects on myocardial oxygen consumption and function are unclear. Cardiac effects of endothelin receptor antagonists may be opposite, as endothelin-1 is known to suppress cardiac contractility. Because PAH is increasingly considered as a disease with quasimalignant growth of cells in the pulmonary vascular wall, therapies are being developed that inhibit hypertrophy and angiogenesis, and promote apoptosis. The inherent danger of these therapies is a further compromise to the already ischemic, fibrotic, and dysfunctional RV. More recently, the right heart has been identified as a direct treatment target in PAH. The effects of well established therapies for left heart failure, such as β-adrenergic receptor blockers, inhibitors of the renin-angiotensin system, exercise training, and assist devices, are currently being investigated in PAH. Future treatment of patients with PAH will likely consist of a multifaceted approaches aiming to reduce the pressure in the lung circulation and improving right heart adaptation simultaneously.

Interventional and surgical therapeutic strategies for pulmonary arterial hypertension: Beyond palliative treatments

Despite significant advances in pharmacological treatments, pulmonary arterial hypertension remains an incurable disease with an unreasonably high morbidity and mortality. Although specific pharmacotherapies have shifted the survival curves of patients and improved exercise endurance as well as quality of life, it is also true that these pharmacological interventions are not always accessible (particularly in developing countries) and, perhaps most importantly, not all patients respond similarly to these drugs. Furthermore, many patients will continue to deteriorate and will eventually require an additional, non-pharmacological, intervention. In this review we analyze the role of atrial septostomy and Potts anastomosis in the management of patients with pulmonary arterial hypertension, we summarize the current worldwide clinical experience (case reports and case series), and discuss why these interventional/surgical strategies might have a therapeutic role beyond that of a "bridge" to transplantation.

Novel technologies and devices for monitoring and treating pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a progressive disease of the pulmonary vasculature associated with significant morbidity and mortality. Despite significant advances in the past 2 decades with the development of pharmacological therapies to target key molecular pathways of PAH, there remains an ongoing need for novel technologies and devices for diagnosis, monitoring, and treatment to improve PAH outcomes. The advent of sophisticated imaging tools, including cardiac magnetic resonance imaging, positron emission tomography, and speckle tracking echocardiography, offer novel opportunities for advanced, noninvasive assessment of right ventricular function, the most powerful predictor of death in patients with PAH. Noninvasive cardiac output monitors and implantable hemodynamic sensors are among the additional promising novel technologies that might offer daily access to hemodynamic data to influence clinical decision-making and potentially improve outcomes. Percutaneous interventional therapeutics might offer a nonpharmacological treatment option in select patients with PAH, ranging from the percutaneous creation of right to left shunts, pulmonary artery denervation, and right ventricular pacing. Finally, mechanical circulatory support with durable ventricular assist devices offers hope to one day provide a realistic strategy to treat life-threatening right ventricular failure in PAH. Future clinical trials and carefully designed prospective observational studies will be needed to evaluate the full potential of many of these novel devices and technologies for monitoring and treating PAH.

Pulmonary vascular diseases

Diseases of the pulmonary vasculature are a cause of increased pulmonary vascular resistance (PVR) in pulmonary embolism, chronic thromboembolic pulmonary hypertension (CTEPH), and pulmonary arterial hypertension or decreased PVR in pulmonary arteriovenous malformations on hereditary hemorrhagic telangiectasia, portal hypertension, or cavopulmonary anastomosis. All these conditions are associated with a decrease in both arterial PO2 and PCO2. Gas exchange in pulmonary vascular diseases with increased PVR is characterized by a shift of ventilation and perfusion to high ventilation-perfusion ratios, a mild to moderate increase in perfusion to low ventilation-perfusion ratios, and an increased physiologic dead space. Hypoxemia in these patients is essentially explained by altered ventilation-perfusion matching amplified by a decreased mixed venous PO2 caused by a low cardiac output. Hypocapnia is accounted for by hyperventilation, which is essentially related to an increased chemosensitivity. A cardiac shunt on a patent foramen ovale may be a cause of severe hypoxemia in a proportion of patients with pulmonary hypertension and an increase in right atrial pressure. Gas exchange in pulmonary arteriovenous malformations is characterized by variable degree of pulmonary shunting and/or diffusion-perfusion imbalance. Hypocapnia is caused by an increased ventilation in relation to an increased pulmonary blood flow with direct peripheral chemoreceptor stimulation by shunted mixed venous blood flow.

Diminazene aceturate improves autonomic modulation in pulmonary hypertension

We have previously demonstrated that diminazene aceturate (DIZE), a putative angiotensin 1-7 converting enzyme activator, protects rats from monocrotaline (MCT)-induced pulmonary hypertension (PH). The present study was conducted to determine if the beneficial effects of DIZE are associated with improvements in autonomic nervous system (ANS) modulation. PH was induced in male rats by a single subcutaneous injection of MCT (50 mg/kg). A subset of MCT rats were treated with DIZE (15 mg/kg/day) for a period of 21 days, after which the ANS modulation was evaluated by spectral and symbolic analysis of heart rate variability (HRV). MCT administration resulted in a significant (P<0.001) increase in the right ventricular systolic pressure (62 ± 14 mmHg) when compared with other experimental groups (Control: 26 ± 6; MCT + DIZE: 31 ± 7 mmHg), while DIZE treatment was able to decrease this pressure. Furthermore MCT-treated rats had significantly reduced total power of HRV than the controls. On the other hand, although not significant, a trend towards increased HRV was observed in the MCT + DIZE group (Control: 108 ± 47; MCT: 12 ± 8.86 and MCT + DIZE: 40 ± 14), suggesting an improvement of the cardiac autonomic modulation. This observation was further confirmed by the low-frequency/high-frequency index of spectral analysis (Control: 0.74 ± 0.62; MCT: 1.45 ± 0.78 and MCT + DIZE: 0.34 ± 0.49) which showed that DIZE treatment was able to recover the ANS imbalance observed in the MCT-induced pulmonary hypertensive rats. Collectively, our results demonstrate that MCT-induced PH is associated with a significant increase in sympathetic modulation and a decrease in HRV, which are markedly improved by DIZE treatment.

Impact of differential right-to-left shunting on systemic perfusion in pulmonary arterial hypertension

OBJECTIVES

This study aimed at identifying the ideal right-to-left shunt-fraction to improve cardiac output (CO) and systemic perfusion in pulmonary arterial hypertension (PHT).

BACKGROUND

Atrial septostomy (AS) has been a high-risk therapeutic option for symptomatic drug-refractory patients with PHT. Results have been unpredictable due to limited knowledge of the optimal shunt-quantity.

METHODS

In nine dogs, an 8-mm shunt-prosthesis was inserted between the superior vena cava (SVC) and the left atrium. With pulmonary artery (PA) banding, mean (± SEM) systolic right ventricular pressure increased from 37 ± 1 mm Hg at baseline to 44 ± 1 mm Hg (moderate PHT, P = 0.005) and 50 ± 2 mm Hg (severe PHT, P < 0.001). Shunt-flow was adjusted by total (forcing all flow through the shunt) or partial occlusion of the SVC and partial or total clamping of the shunt. Caval-, shunt-, and aortic-flow were measured by ultrasonic flow-probes. Blood gases were drawn from the aortic root and PA.

RESULTS

At severe PHT, a shunt-flow of 11 ± 1% of CO (253 ± 90 mL/min) increased CO significantly by 25% (1.8 ± 0.1 to 2.4 ± 0.2 L/min, P = 0.005) causing an increase of systemic oxygen delivery index (DO2 I) by 23% (309 ± 23 to 399 ± 32 mL/min/m(2), P = 0.035). Arterial O2 -saturation did not change significantly until a shunt-flow of 18 ± 2% was exceeded, causing a drop from 96 ± 1% to 84 ± 4% (P = 0.013). At moderate PHT, CO or DO2 I did not improve significantly at any shunt-flow.

CONCLUSIONS

In severe PHT, a shunt-flow of 11% of CO represented the ideal shunt-fraction. Augmentation of CO compensated for declined O2 -saturation due to right-to-left shunting and improved DO2 I. In moderate PHT, AS is less promising.

Cardiac autonomic nerve abnormalities in chronic heart failure are associated with presynaptic vagal nerve degeneration

BACKGROUND

Understanding of the functional and structural disturbances of cardiac autonomic nerves in ventricular hypertrophy and eventual chronic heart failure (CHF) remains unclear.

METHODS AND RESULTS

ECG signals were obtained by a radio transmitter from male Wistar rats that received monocrotaline (MCT) via subcutaneous injection. Heart rate (HR) and HR variability (HRV) were analyzed. The RR interval, total power (TP), low frequency (LF) power, high frequency (HF) power, and LF/HF (L/H) power ratio were measured. Ultrastructural changes in cardiac autonomic nerves at the sinoatrial (SA) node region were studied using an electron microscope. TP and HF powers in MCT-induced right ventricular hypertrophy (RVH) and eventual CHF were significantly decreased, and HR was significantly increased at week 5 or later after the MCT injection. The electron microscopic findings indicated the depletion of neurotransmitter vesicles and degradation of parasympathetic but not sympathetic nerve endings in the SA node region of the heart.

CONCLUSION

MCT-induced RVH and CHF rats showed presynaptic vagal nerve degradation prior to sympathetic nerve derangement in the heart.

Exercise intolerance in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is associated with symptoms of dyspnea and fatigue, which contribute to exercise limitation. The origins and significance of dyspnea and fatigue in PAH are not completely understood. This has created uncertainly among healthcare professionals regarding acceptable levels of these symptoms, on exertion, for patients with PAH. Dysfunction of the right ventricle (RV) contributes to functional limitation and mortality in PAH; however, the role of the RV in eliciting dyspnea and fatigue has not been thoroughly examined. This paper explores the contribution of the RV and systemic and peripheral abnormalities to exercise limitation and symptoms in PAH. Further, it explores the relationship between exercise abnormalities and symptoms, the utility of the cardiopulmonary exercise test in identifying RV dysfunction, and offers suggestions for further research.

Cardiac sympathetic activation in patients with pulmonary arterial hypertension

Patients with congestive heart failure (CHF) due to left ventricular (LV) dysfunction have sympathetic activation specifically directed to the myocardium. Although pulmonary arterial hypertension (PAH) is associated with increased systemic sympathetic activity, its impact on sympathetic drive to ventricular myocardium is unknown. Fifteen patients with PAH (9 women; 54 ± 12 years) were studied: 10 with idiopathic PAH and 5 with a connective tissue disorder. We measured hemodynamics, as well as radiolabeled and endogenous concentrations of arterial and coronary sinus norepinephrine (NE). These measures were repeated after inhaled nitric oxide (NO). Measurement of transcardiac NE concentrations and the cardiac extraction of radiolabeled NE allowed calculation of the corrected transcardiac gradient of NE (CTCG of NE). Comparative data were collected from 15 patients (9 women: 55 ± 12 yr) with normal LV function and 15 patients with CHF (10 women; 53 ± 12 yr). PAH patients had elevated arterial NE concentrations compared with those with normal LV function but were similar to those with CHF. The CTCG of NE was higher in those with PAH than in the normal LV group (3.6 ± 2.2 vs. 1.5 ± 0.9 pmol/ml; P < 0.01) but similar to that seen in those with CHF (3.3 ± 1.4; P = NS). Inhaled NO, which reduced pulmonary artery pressure and increased cardiac output, had no effect on cardiac sympathetic activity. Therefore, cardiac sympathetic activation occurs in PAH. The mechanism of this activation remains uncertain but does not involve elevations in left heart filling pressure.

Atrial septostomy in patients with pulmonary hypertension: should it be recommended?

Treatment options for patients with advanced pulmonary hypertension (PH) are limited. Iatrogenic creation of an interatrial communication (i.e., atrial septostomy [AS]) has been suggested as a possible treatment option or as a bridge to transplantation in selected patients and has been incorporated into current PH guidelines. Uptake of the procedure has been slow and the worldwide experience with AS is limited to approximately 280 published cases, over a period of more than 25 years. The rationale for creating an AS has been provided by the observation that patients with congenital heart disease, shunt lesions and PH have a better survival compared with patients with idiopathic PH. We review pathophysiologic data and the published clinical experience and discuss the rationale, indication and potential pitfalls of AS in patients with severe PH.

Prognostic significance of sympathetic nervous system activation in pulmonary arterial hypertension

RATIONALE

The sympathetic nervous system has been reported to be activated in pulmonary arterial hypertension (PAH).

OBJECTIVES

We investigated the prognostic significance of muscle sympathetic nervous system activity (MSNA) in PAH.

METHODS

Thirty-two patients with PAH were included in the study and underwent a measurement of MSNA over a 6-year period of time. They had undergone a concomitant evaluation of New York Heart Association (NYHA) functional class, a 6-minute walk distance (6MWD), an echocardiographic examination, and a right heart catheterization for diagnostic or reevaluation purposes. The median follow-up time was 20.6 months (interquartile range, 45.8 mo). Clinical deterioration was defined by listing for transplantation or death.

MEASUREMENTS AND MAIN RESULTS

Seventeen patients presented with clinical deterioration. As compared with the 15 others, they had an increased MSNA (80 +/- 12 vs. 52 +/- 18 bursts/min; P < 0.001) and heart rate (88 +/- 17 vs. 74 +/- 12 bpm; P = 0.01), a lower 6MWD (324 +/- 119 vs. 434 +/- 88 m; P < 0.01) and a deteriorated NYHA functional class (3.6 +/- 0.5 vs. 2.9 +/- 0.8; P < 0.001). The hemodynamic variables were not different. MSNA was directly related to heart rate and inversely to 6MWD. A univariate analysis revealed that increased MSNA and heart rate, NYHA class IV, lower 6MWD, and pericardial effusion were associated with subsequent clinical deterioration. A multivariate analysis showed that MSNA was an independent predictor of clinical deterioration. For every increase of 1 burst/minute, the risk of clinical deterioration during follow-up increased by 6%.

CONCLUSIONS

Sympathetic nervous system activation is an independent predictor of clinical deterioration in pulmonary arterial hypertension.