Usefulness of beta-blocker therapy and outcomes in patients with pulmonary arterial hypertension

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.

Treatment of pulmonary arterial hypertension: recent progress and a look to the future

Pulmonary arterial hypertension (PAH) is a severe but treatable form of pre-capillary pulmonary hypertension caused by pulmonary vascular remodelling. As a result of basic science discoveries, randomised controlled trials, studies of real-world data, and the development of clinical practice guidelines, considerable progress has been made in the treatment options and outcomes for patients with PAH, underscoring the importance of seamless translation of information from bench to bedside and, ultimately, to patients. However, PAH still carries a high mortality rate, which emphasises the urgent need for transformative innovations in the field. In this Series paper, written by a group of clinicians, researchers, and a patient with PAH, we review therapeutic approaches and treatment options for PAH. We summarise current knowledge of the cellular and molecular mechanisms of PAH, with an emphasis on emerging treatable pathways and optimisation of current management strategies. In considering future directions for the field, our ambition is to identify therapies with the potential to stall or reverse pulmonary vascular remodelling. We highlight novel therapeutic approaches, the important role of patients as partners in research, and innovative approaches to PAH clinical trials.

Optimal Heart Rate May Improve Systolic and Diastolic Function in Patients with Fontan Circulation

(1) Background: The optimal heart rate, at which the E-wave and A-wave stand adjacent without any overlaps in the Doppler transmitral flow echocardiography, is associated with maximum cardiac output and favorable clinical outcomes in adult patients with systolic heart failure. However, the clinical implication of the echocardiographic overlap length in patients with Fontan circulation remains unknown. We investigated the relationship between heart rate (HR) and hemodynamics in Fontan surgery patients with and without beta-blockers. (2) Methods and Results: A total of 26 patients (median age 1.8 years, 13 males) were enrolled. At baseline, the plasma N-terminal pro-B-type natriuretic peptide was 2439 ± 3483 pg/mL, the fraction area change was 33.5 ± 11.4%, the cardiac index was 3.55 ± 0.90 L/min/m², and the overlap length was 45.2 ± 59.0 msec. Overlap length was importantly decreased after the one-year follow-up (7.60 ± 78.57 msec, p = 0.0069). Positive correlations were noted between the overlap length and A-wave and E/A ratio (p = 0.0021 and p = 0.0046, respectively). Ventricular end-diastolic pressure was significantly correlated with the overlap length in non-beta-blocker patients (p = 0.0483). (3) Conclusion: Overlap length may reflect the status of ventricular dysfunction. Hemodynamic preservation at lower HR could be critical for cardiac reverse remodeling.

Exercise Program Improves Functional Capacity and Quality of Life in Uncorrected Atrial Septal Defect-Associated Pulmonary Arterial Hypertension: A Randomized-Control Pilot Study

OBJECTIVE

To assess the effect of combined hospital and home-based exercise programs on functional capacity and quality of life (QoL) among uncorrected atrial septal defect-associated pulmonary arterial hypertension (ASD-PAH) patients.

METHODS

This study was a randomized controlled trial with uncorrected ASD-PAH patients as the subjects. They were allocated randomly into control and exercise groups. Exercise group subjects performed hospital and home-based exercise programs, completing baseline 6-minute walking test (6MWT) and EQ-5D-3L QoL test (Utility Index and EQ-VAS scores), and were followed up for 12 weeks. The primary outcomes were 6MWT distance and EQ-5D-3L score at week 12. The N-terminal pro B-type natriuretic peptide (NT-proBNP) level was also assessed. A repeated-measure ANOVA was performed to detect endpoint differences over time.

RESULTS

The exercise group contained 20 subjects and control group contained 19. In total, 19 exercise group subjects and 16 control group subjects completed the protocol. The 6MWT distance, Utility Index score, and EQ-VAS score incrementally improved significantly in the exercise group from baseline until week 12, with mean differences of 76.7 m (p<0.001), 0.137 (p<0.001) and 15.5 (p<0.001), respectively. Compared with the control group, the exercise group had significantly increased 6MWT distance and utility index score at week 12. The EQ-VAS score increased in the exercise group at week 12. The NT-proBNP level decreased at week 12 in the exercise group.

CONCLUSION

Combined hospital and home-based exercise program added to PAH-targeted therapy, improving functional capacity and QoL in uncorrected ASD-PAH patients.

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.

Impact of β-blocker therapy on right ventricular function in heart failure patients with reduced ejection fraction. A prospective evaluation

BACKGROUND

Beta-blocker (β-blocker) therapy has been shown to improve mortality and reduce hospitalizations in patients with heart failure (HF) with reduced ejection fraction (HFrEF). Although the physiological action mechanisms of β-blockers are well described, their effects on right ventricular (RV) function have not been prospectively studied.

OBJECTIVE

This prospective study aimed to (a) evaluate whether β-blocker therapy impacts RV remodeling based on echo parameters and (b) determine the predictive echo factors of β-blocker therapy response.

METHODS

From September 2017 to September 2018, HF patients were prospectively enrolled using CIBIS criteria: Class II, III, or IV HF; left ventricular ejection fraction (LVEF) of ≤40%; hospitalized for HF within the previous 12 months. Echo evaluation was performed before initiating β-blocker therapy and 3 months after optimal dose adjustment. Based on previous studies, patients with (absolute) LVEF ≥ 5% improvement were considered significant β-blocker therapy responders.

RESULTS

Overall, 40 patients (pts) completed the study, characterized as follows by age: 70 ± 10 years; gender: 10 women; cardiomyopathy etiology: idiopathic in 24 and ischemic in 16; NYHA Class: II in 22 and III in 10; LVEF: 32 ± 5%; and NTProBNP: 2665 ± 2400 pg/mL. The final population comprised 32 pts (79%), with eight (21%) excluded: two because of β-blocker therapy intolerance, one lost to follow-up, and five withdrew from the study. Under β-blocker therapy, several echo parameters significantly improved: LVEF from 31.7 ± 9 to 40.5 ± 9 (P < .0001); LV end-diastolic volume (EDV) from 154 ± 54 to 143 ± 45 mL (P = .06); LV end-systolic volume (ESV) from 107 ± 49 to 88 ± 37 mL (P = .0006); LV ES from 46 ± 11 to 64 ± 13 mL (P = .008); LV end-diastolic diameter (EDD) from 57 ± 9 to 54 ± 6 mm (P = .04); LV end-systolic diameter (ESD) from 48 ± 10 to 44 ± 7 mm (P = .007); and right ventricular systolic pressure (RV SP) from 39 ± 10 to 32 ± 8 mm Hg (P = .0001). Significant modifications were observed in terms of RV echo parameters: right ventricular (RV) size decreased from 30 ± 4 to 27 ± 5 mm (P = .03), while RV systolic function significantly improved based on tricuspid annular plane systolic excursion (TAPSE) (16.5 ± 4 vs. 19 ± 4 mm; 0.0006); DTI-derived tricuspid lateral annular systolic velocity wave (S') (10 ± 2 vs. 11.3 ± 3 cm/s; P = .03); and RIMP (Tei index) (0.5 ± 0.1 vs 0.46 ± 0.1; P = .04). RV 2D fractional area change (%) did not significantly differ despite a clear improvement tendency (35 ± 6 vs. 37 ± 4%; P = .1). No significant modifications were observed concerning LV diastolic parameters. Overall, β-blocker echo responders (n = 23/32; 72%) exhibited the same left and right echo parameters. No echo variables predicted the β-blocker response.

CONCLUSIONS

In HFrEF pts, β-blocker therapy significantly improves LV and RV systolic remodeling. Accordingly, β-blocker therapy could be applied as soon as possible in HFrEF patients with right ventricular dysfunction so as to limit RV remodeling.

Atrial arrhythmias in chronic lung disease-associated pulmonary hypertension

Atrial arrhythmias are common during episodes of acute respiratory failure in patients with chronic lung disease-associated pulmonary hypertension. Expert opinion suggests that management of atrial arrhythmias in patients with pulmonary hypertension should aim to restore sinus rhythm. This is clinically challenging in pulmonary hypertension patients with coexisting chronic lung disease, as there is controversy on the use of rhythm control agents; generally, in regard to either their pulmonary toxicity profile or the lack of evidence supporting their use. Rate control methods are largely focused on the use of beta blockers and calcium channel blockers. Concerns regarding their use involve their negative inotropic properties in cor pulmonale, the risk of bronchospasm associated with beta blockers, and the potential for ventilation/perfusion mismatching associated with calcium channel blockers. While digoxin has been associated with promising outcomes during acute right ventricular failure, there is limited evidence to suggest its routine use. Electrical cardioversion is associated with a high failure rate and it frequently requires multiple attempts. Radiofrequency catheter ablation is a more definitive approach, but concerns surrounding mechanical ventilation and sedation limit its applicability in decompensated pulmonary hypertension. Individual approaches are needed to address atrial arrhythmia management during acute episodes of respiratory failure.

Trends in the off-label use of β-blockers in pediatric patients

The use of US Food and Drug Administration (FDA)-approved drugs for the treatment of an unapproved indication or in an unapproved age group, or at doses or route of administration not indicated on the label is known as off-label use. Off-label use may be beneficial in circumstances when the standard-of-care treatment has failed, and/or no other FDA-approved medications are available for a particular condition. In pediatric patients, off-label use may increase the risk of adverse events as pharmacokinetic and pharmacodynamic data are limited in children. Approximately 73% of off-label drugs currently prescribed for various conditions do not have sufficient scientific evidence for safety and efficacy. For example, β-blockers are a class of drugs with FDA-approval for very few indications in pediatrics but are commonly used for various off-label indications. Interestingly, the proportion of off-label use of β-blockers in adults is at about 52% (66.2 million) of the total number of β-blockers prescribed. The frequency of off-label use of β-blockers in children is also high with limited data on the indications as well as safety and efficacy. We present trends in off-label use of β-blockers in children to discuss drug safety and efficacy and include recommendations for pediatric providers.

EXPRESS: Cardiac Sympathetic Dysfunction in Pulmonary Arterial Hypertension: Lesson from Left-sided Heart Failure

Sympathetic nervous system hyperactivity has a well-recognized role in the pathophysiology of heart failure with reduced left ventricular ejection fraction. Alterations in sympathetic nervous system have been related to the pathophysiology of pulmonary arterial hypertension, but it is unclear whether cardiac sympathetic nervous system is impaired and how sympathetic dysfunction correlates with hemodynamics and clinical status in pulmonary arterial hypertension patients. The aim of this study was to evaluate the cardiac sympathetic nervous system activity by means of 123Iodine-metaiodobenzylguanidine nuclear imaging in pulmonary arterial hypertension patients and to explore its possible correlation with markers of disease severity. Twelve consecutive pulmonary arterial hypertension patients (nine women, median age 56.5 (17.8), eight idiopathic and four connective tissue-associated pulmonary arterial hypertension) underwent cardiac 123Iodine-metaiodobenzylguanidine scintigraphy. The results were compared with those of 12 subjects with a negative history of cardiovascular or pulmonary disease who underwent the same nuclear imaging test because of a suspected paraganglioma or pheochromocytoma, with a negative result (controls), and 12 patients with heart failure with reduced left ventricular ejection fraction. Hemodynamics, echocardiography, six-minute walking distance, cardiopulmonary exercise testing, and N-terminal pro brain natriuretic peptide were collected in pulmonary arterial hypertension patients within one week from 123Iodine-metaiodobenzylguanidine scintigraphy. Cardiac 123Iodine-metaiodobenzylguanidine uptake, assessed as early and late heart-to-mediastinum ratio, was significantly lower in pulmonary arterial hypertension compared to controls (p = 0.001), but similar to heart failure with reduced left ventricular ejection fraction. Myocardial 123Iodine-metaiodobenzylguanidine turnover, expressed as washout rate, was similar in pulmonary arterial hypertension and heart failure with reduced left ventricular ejection fraction and significantly higher compared to controls (p = 0.016). In the pulmonary arterial hypertension group, both early and late heart-to-mediastinum ratios and washout rate correlated with parameters of pulmonary arterial hypertension severity including pulmonary vascular resistance, right atrial pressure, tricuspid annular plane systolic excursion, N-terminal pro brain natriuretic peptide, and peak VO2. Although we evaluated a small number of subjects, our study showed a significant impairment in cardiac sympathetic nervous system in pulmonary arterial hypertension, similarly to that observed in heart failure with reduced left ventricular ejection fraction. This impairment correlated with indices of pulmonary arterial hypertension severity. Cardiac sympathetic dysfunction may be a contributing factor to the development of right-sided heart failure in pulmonary arterial hypertension.

Energy Metabolism in the Failing Right Ventricle: Limitations of Oxygen Delivery and the Creatine Kinase System

Pulmonary arterial hypertension (PAH) results in hypertrophic remodeling of the right ventricle (RV) to overcome increased pulmonary pressure. This increases the O2 consumption of the myocardium, and without a concomitant increase in energy generation, a mismatch with demand may occur. Eventually, RV function can no longer be sustained, and RV failure occurs. Beta-adrenergic blockers (BB) are thought to improve survival in left heart failure, in part by reducing energy expenditure and hypertrophy, however they are not currently a therapy for PAH. The monocrotaline (MCT) rat model of PAH was used to investigate the consequence of RV failure on myocardial oxygenation and mitochondrial function. A second group of MCT rats was treated daily with the beta-1 blocker metoprolol (MCT + BB). Histology confirmed reduced capillary density and increased capillary supply area without indications of capillary rarefaction in MCT rats. A computer model of O2 flux was applied to the experimentally recorded capillary locations and predicted a reduction in mean tissue PO2 in MCT rats. The fraction of hypoxic tissue (defined as PO2 < 0.5 mmHg) was reduced following beta-1 blocker (BB) treatment. The functionality of the creatine kinase (CK) energy shuttle was measured in permeabilized RV myocytes by sequential ADP titrations in the presence and absence of creatine. Creatine significantly decreased the KmADP in cells from saline-injected control (CON) rats, but not MCT rats. The difference in KmADP with or without creatine was not different in MCT + BB cells compared to CON or MCT cells. Improved myocardial energetics could contribute to improved survival of PAH with chronic BB treatment.

Endothelial Phenotype Evoked by Low Dose Carvedilol in Pulmonary Hypertension

Background: The therapeutic benefits of β-blockers are well established in left heart failure. The Pulmonary Arterial Hypertension Treatment with Carvedilol for Heart Failure [PAHTCH] study showed safety and possible benefit of carvedilol in pulmonary arterial hypertension (PAH) associated right heart failure over 6 months. This study aims at evaluating the short-term cardiovascular effects and early mechanistic biomarkers of carvedilol therapy.

Methods: Thirty patients with pulmonary hypertension (PH) received low dose carvedilol (3.125 mg twice daily) for 1 week prior to randomization to placebo, low-dose, or dose-escalating carvedilol therapy. Echocardiography was performed at baseline and 1 week. Exercise capacity was assessed by 6 min walk distance (6MWD). The L-arginine/nitric oxide pathway and other biological markers of endothelial function were measured.

Results: All participants tolerated 1 week of carvedilol without adverse effects. After 1 week of carvedilol, 6MWD and heart rate at peak exercise did not vary (both p > 0.1). Heart rate at rest and 1 min post walk dropped significantly (both p < 0.05) with a trend for increase in heart rate recovery (p = 0.08). Right ventricular systolic pressure (RVSP) decreased by an average of 13 mmHg (p = 0.002). Patients who had a decrease in RVSP of more than 10 mm Hg were defined as responders (n = 17), and those with a lesser drop as non-responders (n = 13). Responders had a significant drop in pulmonary vascular resistance (PVR) after 1 week of carvedilol (p = 0.004). In addition, responders had a greater decrease in heart rate at rest and 1 min post walk compared to non-responders (both p < 0.05). Responders had higher plasma arginine and global bioavailability of arginine at baseline compared to non-responders (p = 0.03 and p = 0.05, respectively). After 1 week of carvedilol, responders had greater increase in urinary nitrate (p = 0.04). Responders treated with carvedilol had a sustained drop in RVSP and PVR after 6 months of carvedilol with no change in cardiac output.

Conclusions: Low-dose carvedilol for 1 week can potentially identify a PH responder phenotype that may benefit from β-blockers that is associated with less endothelial dysfunction.

Clinical Trial Registration:http://www.clinicaltrials.gov. identifier: NCT01586156.

Neurohormonal modulation as therapeutic avenue for right ventricular dysfunction in pulmonary artery hypertension: till the dawn, waiting

Neuro-hormonal activation may lead to or be associated with pulmonary arterial hypertension (PAH) and right ventricular dysfunction. Notwithstanding whether it is the cause or the consequence of PAH-related right ventricle (RV) dysfunction neurohormonal activation contributes to significant morbidity and mortality in patients with PAH and the progression of RV dysfunction. Experimental data regarding the use of beta adrenergic blockade and renin-angiotensin aldosterone system modulation are encouraging. However, clinical studies have largely been negative or neutral; and, neuro-hormonal modulation is discouraged in patients with PAH related RV dysfunction for fear of systemic hypotension. Herein, we summarize the pathophysiological background that supports the potential role of neuro-hormonal modulation in the management of PAH related RV dysfunction; also present current clinical experience; and, discuss the need for controlled studies to move forward. Lastly, we review potential non- pharmacological modalities for neuro-hormonal modulations in PAH patients with RV dysfunction.

Beta1-adrenoceptor antagonist, metoprolol attenuates cardiac myocyte Ca2+ handling dysfunction in rats with pulmonary artery hypertension

Right heart failure is the major cause of death in Pulmonary Artery Hypertension (PAH) patients but is not a current, specific therapeutic target. Pre-clinical studies have shown that adrenoceptor blockade can improve cardiac function but the mechanisms of action within right ventricular (RV) myocytes are unknown. We tested whether the β1-adrenoceptor blocker metoprolol could improve RV myocyte function in an animal model of PAH, by attenuating adverse excitation-contraction coupling remodeling. PAH with RV failure was induced in rats by monocrotaline injection. When PAH was established, animals were given 10 mg/kg/day metoprolol (MCT + BB) or vehicle (MCT). The median time to the onset of heart failure signs was delayed from 23 days (MCT), to 31 days (MCT + BB). At 23 ± 1 days post-injection, MCT + BB showed improved in vivo cardiac function, measured by echocardiography. RV hypertrophy was reduced despite persistent elevated afterload. RV myocyte contractility during field stimulation was improved at higher pacing frequencies in MCT + BB. Preserved t-tubule structure, more uniform evoked Ca2+ release, increased SERCA2a expression and faster ventricular repolarization (measured in vivo by telemetry) may account for the improved contractile function. Sarcoplasmic reticulum Ca2+ overload was prevented in MCT + BB myocytes resulting in fewer spontaneous Ca2+ waves, with a lower pro-arrhythmic potential. Our novel finding of attenuation of defects in excitation contraction coupling by β1-adrenoceptor blockade with delays in the onset of HF, identifies the RV as a promising therapeutic target in PAH. Moreover, our data suggest existing therapies for left ventricular failure may also be beneficial in PAH induced RV failure.

Evaluation and Management of Right-Sided Heart Failure: A Scientific Statement From the American Heart Association

Background and Purpose:

The diverse causes of right-sided heart failure (RHF) include, among others, primary cardiomyopathies with right ventricular (RV) involvement, RV ischemia and infarction, volume loading caused by cardiac lesions associated with congenital heart disease and valvular pathologies, and pressure loading resulting from pulmonic stenosis or pulmonary hypertension from a variety of causes, including left-sided heart disease. Progressive RV dysfunction in these disease states is associated with increased morbidity and mortality. The purpose of this scientific statement is to provide guidance on the assessment and management of RHF.

Methods:

The writing group used systematic literature reviews, published translational and clinical studies, clinical practice guidelines, and expert opinion/statements to summarize existing evidence and to identify areas of inadequacy requiring future research. The panel reviewed the most relevant adult medical literature excluding routine laboratory tests using MEDLINE, EMBASE, and Web of Science through September 2017. The document is organized and classified according to the American Heart Association to provide specific suggestions, considerations, or reference to contemporary clinical practice recommendations.

Results:

Chronic RHF is associated with decreased exercise tolerance, poor functional capacity, decreased cardiac output and progressive end-organ damage (caused by a combination of end-organ venous congestion and underperfusion), and cachexia resulting from poor absorption of nutrients, as well as a systemic proinflammatory state. It is the principal cause of death in patients with pulmonary arterial hypertension. Similarly, acute RHF is associated with hemodynamic instability and is the primary cause of death in patients presenting with massive pulmonary embolism, RV myocardial infarction, and postcardiotomy shock associated with cardiac surgery. Functional assessment of the right side of the heart can be hindered by its complex geometry. Multiple hemodynamic and biochemical markers are associated with worsening RHF and can serve to guide clinical assessment and therapeutic decision making. Pharmacological and mechanical interventions targeting isolated acute and chronic RHF have not been well investigated. Specific therapies promoting stabilization and recovery of RV function are lacking.

Conclusions:

RHF is a complex syndrome including diverse causes, pathways, and pathological processes. In this scientific statement, we review the causes and epidemiology of RV dysfunction and the pathophysiology of acute and chronic RHF and provide guidance for the management of the associated conditions leading to and caused by RHF.

Stage‑dependent changes of β2‑adrenergic receptor signaling in right ventricular remodeling in monocrotaline‑induced pulmonary arterial hypertension

Right ventricular (RV) remodeling coupled with extensive apoptosis in response to unrestrained biomechanical stress may lead to RV failure (RVF), which is the immediate cause of death in the majority of patients with pulmonary arterial hypertension (PAH). Overexpression of β₂-adrenergic receptor (β₂-AR) signaling has been reported to induce myocardiotoxicity in patients with left heart failure. However, the role of β₂-AR signaling in the pathophysiology of PAH development has remained elusive. To address this issue, the present study investigated the changes in cardiopulmonary function and structure, as well as the expression of regulators of fibrosis and apoptosis in RVF following monocrotaline (MCT; 60 mg/kg, i.p.)-induced PAH in rats. Cardiopulmonary function and structure, remodeling and apoptosis, as well as G protein-coupled receptor (GPCR) and β₂-AR signaling, were documented over a period of 6 weeks. In the early stages, elevated pulmonary arterial pressure, pulmonary lesions, RV hypertrophy, evidence of left ventricular (LV) hyperfunction and accelerated heart rate were observed in animals with MCT-induced PAH. The levels of angiotensin II receptor type 1b (Agtr1b), Agtr2 and Agt were markedly upregulated and the expression of β₂-AR phospho-Ser(355,356) steadily decreased in the right heart. As the disease progressed, LV dysfunction was observed, as evidenced by decreased LV systolic pressure and increased LV end-diastolic pressure, which was accompanied by a sustained increase in circulating brain natriuretic peptide levels. Of note, increased levels of cardiomyocyte apoptosis and concomitant RV remodeling, including hypertrophy, dilatation, inflammation and fibrosis, were observed, despite the enhanced RV contractility. Furthermore, alterations in GPCR signaling and activation in β₂-AR-G_s-protein kinase A/Ca²⁺/calmodulin-dependent kinase II signaling were observed in the late stages of PAH. These results suggested that treatment with MCT results in adaptive and maladaptive RV remodeling and apoptosis during the progression of PAH, which is accompanied by distinct changes in the β₂-AR signaling. Therefore, these results enable researchers to better understand of pathophysiology of MCT-induced PAH, as well as to determine the effects of novel therapies.

Autonomic nervous system involvement in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a chronic pulmonary vascular disease characterized by increased pulmonary vascular resistance (PVR) leading to right ventricular (RV) failure. Autonomic nervous system involvement in the pathogenesis of PAH has been demonstrated several years ago, however the extent of this involvement is not fully understood. PAH is associated with increased sympathetic nervous system (SNS) activation, decreased heart rate variability, and presence of cardiac arrhythmias. There is also evidence for increased renin-angiotensin-aldosterone system (RAAS) activation in PAH patients associated with clinical worsening. Reduction of neurohormonal activation could be an effective therapeutic strategy for PAH. Although therapies targeting adrenergic receptors or RAAS signaling pathways have been shown to reverse cardiac remodeling and improve outcomes in experimental pulmonary hypertension (PH)-models, the effectiveness and safety of such treatments in clinical settings have been uncertain. Recently, novel direct methods such as cervical ganglion block, pulmonary artery denervation (PADN), and renal denervation have been employed to attenuate SNS activation in PAH. In this review, we intend to summarize the multiple aspects of autonomic nervous system involvement in PAH and overview the different pharmacological and invasive strategies used to target autonomic nervous system for the treatment of PAH.

Pulmonary arterial hypertension treatment with carvedilol for heart failure: a randomized controlled trial

BACKGROUND

Right-sided heart failure is the leading cause of death in pulmonary arterial hypertension (PAH). Similar to left heart failure, sympathetic overactivation and β-adrenoreceptor (βAR) abnormalities are found in PAH. Based on successful therapy of left heart failure with β-blockade, the safety and benefits of the nonselective β-blocker/vasodilator carvedilol were evaluated in PAH.

METHODS

PAH Treatment with Carvedilol for Heart Failure (PAHTCH) is a single-center, double-blind, randomized, controlled trial. Following 1-week run-in, 30 participants were randomized to 1 of 3 arms for 24 weeks: placebo, low-fixed-dose, or dose-escalating carvedilol. Outcomes included clinical measures and mechanistic biomarkers.

RESULTS

Decreases in heart rate and blood pressure with carvedilol were well tolerated; heart rate correlated with carvedilol dose. Carvedilol-treated groups had no decrease in exercise capacity measured by 6-minute walk, but had lower heart rates at peak and after exercise, and faster heart rate recovery. Dose-escalating carvedilol was associated with reduction in right ventricular (RV) glycolytic rate and increase in βAR levels. There was no evidence of RV functional deterioration; rather, cardiac output was maintained.

CONCLUSIONS

Carvedilol is likely safe in PAH over 6 months of therapy and has clinical and mechanistic benefits associated with improved outcomes. The data provide support for longer and larger studies to establish guidelines for use of β-blockers in PAH.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01586156FUNDING. This project was supported by NIH R01HL115008 and R01HL60917 and in part by the National Center for Advancing Translational Sciences, UL1TR000439.

Use of β-Blockers in Pulmonary Hypertension

Contrasting with the major attention that left heart failure has received, right heart failure remains understudied both at the preclinical and clinical levels. However, right ventricle failure is a major predictor of outcomes in patients with precapillary pulmonary hypertension because of pulmonary arterial hypertension, and in patients with postcapillary pulmonary hypertension because of left heart disease. In pulmonary hypertension, the status of the right ventricle is one of the most important predictors of both morbidity and mortality. Paradoxically, there are currently no approved therapies targeting the right ventricle in pulmonary hypertension. By analogy with the key role of β-blockers in the management of left heart failure, some authors have proposed to use these agents to support the right ventricle function in pulmonary hypertension. In this review, we summarize the current knowledge on the use of β-blockers in pulmonary hypertension.

Challenges in the Management of Patients with Chronic Obstructive Pulmonary Disease and Heart Failure With Reduced Ejection Fraction

Chronic obstructive pulmonary disease (COPD) and heart failure with reduced ejection fraction (HFrEF) commonly coexist in clinical practice. The prevalence of COPD among HFrEF patients ranges from 20 to 32 %. On the other hand; HFrEF is prevalent in more than 20 % of COPD patients. With an aging population, the number of patients with coexisting COPD and HFrEF is on rise. Coexisting COPD and HFrEF presents a unique diagnostic and therapeutic clinical conundrum. Common symptoms shared by both conditions mask the early referral and detection of the other. Beta blockers (BB), angiotensin-converting enzyme inhibitors, and aldosterone antagonists have been shown to reduce hospitalizations, morbidity, and mortality in HFrEF while long-acting inhaled bronchodilators (beta-2-agonists and anticholinergics) and corticosteroids have been endorsed for COPD treatment. The opposing pharmacotherapy of BBs and beta-2-agonists highlight the conflict in prescribing BBs in COPD and beta-2-agonists in HFrEF. This has resulted in underutilization of evidence-based therapy for HFrEF in COPD patients owing to fear of adverse effects. This review aims to provide an update and current perspective on diagnostic and therapeutic management of patients with coexisting COPD and HFrEF.

Bisoprolol in idiopathic pulmonary arterial hypertension: an explorative study

While beta-blockers are considered contraindicated in pulmonary arterial hypertension (PAH), the prognostic significance of sympathetic nervous system over-activity suggests a potential benefit of beta-blocker therapy. The aim of this randomised, placebo-controlled, crossover, single centre study was to determine the effects of bisoprolol on right ventricular ejection fraction (RVEF) in idiopathic PAH (iPAH) patients. Additional efficacy and safety parameters were explored.Patients with optimally treated, stable iPAH (New York Heart Association functional class II/III) were randomised to placebo or bisoprolol. Imaging and functional measurements were performed at baseline, crossover and end of study.18 iPAH patients were included, because inclusion faltered before enrolment of the targeted 25 patients. 17 patients completed 6 months of bisoprolol, 15 tolerated bisoprolol, one patient required intravenous diuretics. Bisoprolol was associated with a lower heart rate (17 beats per minute, p=0.0001) but RVEF remained unchanged. A drop in cardiac index (0.5 L·min(-1)·m(-2), p=0.015) was observed, along with a trend towards a decreased 6-min walking distance (6MWD).Although careful up-titration of bisoprolol was tolerated by most patients and resulted in a decreased heart rate, no benefit of bisoprolol in iPAH was demonstrated. Decreases in cardiac index and 6MWD suggest a deteriorated cardiac function. The results do not favour the use of bisoprolol in iPAH patients.

The right ventricle and pulmonary hypertension

In patients with pulmonary hypertension (PH), the primary cause of death is right ventricular (RV) failure. Improvement in RV function is therefore one of the most important treatment goals. In order to be able to reverse RV dysfunction and also prevent RV failure, a detailed understanding of the pathobiology of RV failure and the underlying mechanisms concerning the transition from a pressure-overloaded adapted right ventricle to a dilated and failing right ventricle is required. Here, we propose that insufficient RV contractility, myocardial fibrosis, capillary rarefaction, and a disturbed metabolism are important features of a failing right ventricle. Furthermore, an overview is provided about the potential direct RV effects of PH-targeted therapies and the effects of RV-directed medical treatments.

The adrenergic system in pulmonary arterial hypertension: bench to bedside (2013 Grover Conference series)

In heart failure with reduced left ventricular ejection fraction (HFrEF), adrenergic activation is a key compensatory mechanism that is a major contributor to progressive ventricular remodeling and worsening of heart failure. Targeting the increased adrenergic activation with β-adrenergic receptor blocking agents has led to the development of arguably the single most effective drug therapy for HFrEF. The pressure-overloaded and ultimately remodeled/failing right ventricle (RV) in pulmonary arterial hypertension (PAH) is also adrenergically activated, which raises the issue of whether an antiadrenergic strategy could be effectively employed in this setting. Anecdotal experience suggests that it will be challenging to administer an antiadrenergic treatment such as a β-blocking agent to patients with established moderate-severe PAH. However, the same types of data and commentary were prevalent early in the development of β-blockade for HFrEF treatment. In addition, in HFrEF approaches have been developed for delivering β-blocker therapy to patients who have extremely advanced heart failure, and these general principles could be applied to RV failure in PAH. This review examines the role played by adrenergic activation in the RV faced with PAH, contrasts PAH-RV remodeling with left ventricle remodeling in settings of sustained increases in afterload, and suggests a possible approach for safely delivering an antiadrenergic treatment to patients with RV dysfunction due to moderate-severe PAH.

Use of outcome measures in pulmonary hypertension clinical trials

OBJECTIVES

To evaluate the use of surrogate measures in pulmonary hypertension (PH) clinical trials and how it relates to clinical practice.

BACKGROUND

Studies of pulmonary arterial hypertension (PAH) employ a variety of surrogate measures in addition to clinical events because of a small patient population, participant burden, and costs. The use of these measures in PH drug trials is poorly defined.

METHODS

We searched PubMed/MEDLINE/Embase for randomized or prospective cohort PAH clinical treatment trials from 1985 to 2013. Extracted data included intervention, trial duration, study design, patient characteristics, and primary and secondary outcome measures. To compare with clinical practice, we assessed the use of surrogate measures in a clinical sample of patients on PH medications at Duke University Medical Center between 2003 and 2014.

RESULTS

Between 1985 and 2013, 126 PAH trials were identified and analyzed. Surrogate measures served as primary endpoints in 119 trials (94.0%). Inclusion of invasive hemodynamics decreased over time (78.6%, 75.0%, 52.2%; P for trend = .02), while functional testing (7.1%, 60.0%, 81.5%; P for trend < .0001) and functional status or quality of life (0%, 47.6%, 62.8%; P for trend < .0001) increased in PAH trials over the same time periods. Echocardiography data were reported as a primary or secondary outcome in 32 trials (25.4%) with increased use from 1985-1994 to 1995-2004 (7.1% vs 35.0%, P = .04), but the trend did not continue to 2005-2013 (25.0%). In comparison, among 450 patients on PAH therapies at our institution between 2003 and 2013, clinical assessments regularly incorporated serial echocardiography and 6-minute walk distance tests (92% and 95% of patients, respectively) and repeat measurement of invasive hemodynamics (46% of patients).

CONCLUSIONS

The majority of PAH trials have utilized surrogate measures as primary endpoints. The use of these surrogate endpoints has evolved significantly over time with increasing use of patient-centered endpoints and decreasing or stable use of imaging and invasive measures. In contrast, imaging and invasive measures are commonly used in contemporary clinical practice. Further research is needed to validate and standardize currently used measures.

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.

Existing drugs and agents under investigation for pulmonary arterial hypertension

Pulmonary arterial hypertension is a progressive and debilitating disorder with an associated high morbidity and mortality rate. Significant advances in our understanding of the epidemiology, pathogenesis, and pathophysiology of pulmonary hypertension have occurred over the past several decades. This has allowed the development of new therapeutic options in this disease. Today, our selection of therapeutic modalities is broader, including calcium channel blockers, prostanoids, endothelin receptor antagonists, phosphodiesterase inhibitors, and soluble guanylate cyclase stimulators, but the disease remains fatal. This underscores the need for a continued search for novel therapies. Several potential pharmacologic agents for the treatment of pulmonary arterial hypertension are under clinical development and some promising results with these treatments have been reported. These agents include rho-kinase inhibitors, long-acting nonprostanoid prostacyclin receptor agonists, tyrosine protein kinase inhibitors, endothelial nitric oxide synthase couplers, synthetically produced vasoactive intestinal peptide, antagonists of the 5-HT2 receptors, and others. This article will review several of these promising new therapies and will discuss the current evidence regarding their potential benefit in pulmonary arterial hypertension.

Ventricular tachycardias in patients with pulmonary hypertension: an underestimated prevalence? A prospective clinical study

BACKGROUND

Sudden cardiac death (SCD) accounts for approximately 30 % in patients with pulmonary arterial hypertension (PAH). The exact circumference for SCD in this patient population is still unclear. Malignant cardiac arrhythmias are reported to be rarely present. There are no systematic data concerning long-term electrocardiographic (ECG) recording in patients with PAH.

OBJECTIVES

We sought to investigate the rate of potentially relevant arrhythmias in patients with pulmonary hypertension (PH).

METHODS

Consecutive patients without diagnosis of known cardiac arrhythmias followed in our outpatient clinic for PH were enrolled in the study. All patients underwent a 72-h Holter ECG. Clinical data, 6-min walk distance, laboratory values, and echocardiography were collected/performed.

RESULTS

Ninety-two consecutive patients (New York Heart Association class (NYHA) III/IV: 65.2 %/5.4 %, PH Group 1: 35.9 %, Group 3: 10.9 %, Group 4: 28.3 %, Group 5: 2.2 %) were investigated. Relevant arrhythmias were newly detected in 17 patients: non-sustained ventricular tachycardia (n = 12), intermittent second-degree heart block (n = 1), intermittent third-degree heart block (n= 3), and atrial flutter (n = 1). Echocardiographic systolic pulmonary pressure and diameter of the right heart were elevated in patients with relevant arrhythmias. Right heart catheterization revealed higher pulmonary vascular resistance (672 vs. 542 dyn · s · cm(-5), p = 0.247) and lower cardiac index (2.46 vs. 2.82 l/min/m(2), p = 0.184).

CONCLUSIONS

Ventricular tachycardias occur more often in PH patients than previously reported. However, the prognostic relevance of non-sustained ventricular tachycardias in this cohort remains unclear. As a large number of PH patients die from SCD, closer monitoring, e.g., using implantable event recorders, might be useful to identify patients at high risk.

Outcomes of β-blocker use in pulmonary arterial hypertension: a propensity-matched analysis

The utility and safety of β-blockers in pulmonary hypertension is controversial. Anecdotal reports suggest that β-blockers may be harmful in these patients. The aim of our study was to evaluate outcomes of β-blocker use in pulmonary hypertension.We reviewed patients from our pulmonary hypertension registry between 2000 and 2011. Patients who continued to use β-blockers were compared to those who never used β-blockers for all-cause mortality, time to clinical worsening events, defined as death, lung transplantation and hospitalisation due to pulmonary hypertension. We also evaluated the effect of β-blockers on 6-min walking distance and New York Heart Association (NYHA) functional class.133 patients used β-blockers and 375 patients never used β-blockers. Mean±sd age was 57±16 years and the median follow-up period was 78 months. Propensity-matched analysis showed that the adjusted odds ratio (95% CI) for mortality with β-blocker use was 1.13 (0.69-1.82) and for clinical worsening events was 0.96 (0.55-1.68). No significant difference was noted in probability of survival and time to clinical worsening events. Patients on β-blockers walked a shorter distance on follow-up 6 min walk test; follow-up NYHA class was similar between groups.Pulmonary hypertension patients receiving β-blockers had a similar survival and time to clinical worsening events compared to patients not receiving them. Functional outcomes were similar, although β-blocker use was associated with a tendency towards shorter walking distance.

Sympathetic nervous system activation and β-adrenoceptor blockade in right heart failure

Right heart failure may develop from pulmonary arterial hypertension or various forms of congenital heart disease. Right ventricular adaptation to the increased afterload is the most important prognostic factor in pulmonary hypertension and congenital heart disease, which share important pathophysiological mechanisms, despite having different aetiologies. There is substantial evidence of increased sympathetic nervous system activation in right heart failure related to both pulmonary hypertension and congenital heart disease. It is unknown to which degree this activation is an adaptive response, a maladaptive response, or if it mainly reflects disease progression. Several experimental studies and clinical trials have been conducted to answer these questions. Here, we review the existing knowledge on sympathetic nervous system activation and the effects of β-adrenoceptor blockade in experimental and clinical right heart failure. This review identifies important gaps in our understanding of the right ventricle and discusses the potential of β-blockers in the treatment of right heart failure.

Vascular stiffening in pulmonary hypertension: cause or consequence? (2013 Grover Conference series)

Recent studies have indicated that systemic arterial stiffening is a precursor to hypertension and that hypertension, in turn, can perpetuate arterial stiffening. Pulmonary artery (PA) stiffening is also well documented to occur in pulmonary hypertension (PH), and there is evidence that pulmonary vascular stiffness (PVS) may be a better predictor of outcome than pulmonary vascular resistance (PVR). We have hypothesized that the decreased flow-damping function of elastic PAs in PH likely initiates and/or perpetuates dysfunction of pulmonary microvasculature. Recent studies have shown that large-vessel stiffening increases flow pulsatility in the distal pulmonary vasculature, leading to endothelial dysfunction within a proinflammatory, vasoconstricting, and profibrogenic environment. The intricate role of stiffening-stimulated high pulsatile flow in endothelial cell dysfunction includes stepwise molecular events underlying PA hypertrophy, inflammation, endothelial-mesenchymal transition, and fibrosis. In addition to contributing to microenvironmental alterations of the distal vasculature, disordered proximal-distal PA coupling likely also plays a role in increasing ventricular afterload, ultimately causing right ventricle (RV) dysfunction and death. Current therapeutic treatments do not provide a realistic approach to destiffening arteries and, thus, to potentially abrogating the effects of high pulsatile flow on the distal pulmonary vasculature or the increased work imposed by stiffening on the RV. Scrutinizing the effect of PA stiffening on high pulsatile flow-induced cellular and molecular changes, and vice versa, might lead to important new therapeutic options that abrogate PA remodeling and PH development. With a clear understanding that PA stiffening may contribute to the progression of PH to an irreversible state by contributing to chronic microvascular damage in lungs, future studies should be aimed first at defining the underlying mechanisms leading to PA stiffening and then at improved treatment approaches based on these findings.

β-Blocker Therapy Is Not Associated With Adverse Outcomes in Patients With Pulmonary Arterial Hypertension

Background—

The safety of β-blockers in patients with isolated right ventricular failure because of pulmonary arterial hypertension (PAH) is unclear.

Methods and Results—

We studied 564 PAH patients (total cohort) referred to our center from 1982 to 2013. Propensity score-matching was used to match pairs of PAH patients with and without β-blocker use (matched cohort). We compared all-cause mortality between the groups in the total cohort and the matched cohort using bootstrap validation, Kaplan–Meier, and Cox proportional hazard analyses. Seventy-one of the 564 patients in the total cohort were on β-blockers. They were older, had higher prevalence of comorbidities, and were more often on diuretics, digoxin, and angiotensin converting enzyme inhibitors. The severity of PAH and right ventricular failure was similar between those with and without β-blocker use. After propensity matching, 63 patients with β-blocker use were compared with 51 patients without β-blocker use. During a median follow-up time of 4.8 years, there were 339 (60%) deaths in the total cohort and 70 deaths (61%) in the matched cohort. There was no difference in absolute mortality between those with and without β-blockers ( P =0.71). β-Blocker use was not associated with increased all-cause mortality in the total cohort after adjusting for propensity score (adjusted hazard ratio, 1.0; 95% confidence interval, 0.7–1.5) and in the matched cohort (hazard ratio, 1.2; 95% confidence interval, 0.8–2.0).

Conclusions—

There was no statistically significant difference in long-term mortality between propensity score-matched pairs of PAH patients with and without β-blocker use. These findings need further validation in prospective clinical trials.

Current clinical management of pulmonary arterial hypertension

During the past 2 decades, there has been a tremendous evolution in the evaluation and care of patients with pulmonary arterial hypertension (PAH). The introduction of targeted PAH therapy consisting of prostacyclin and its analogs, endothelin antagonists, phosphodiesterase-5 inhibitors, and now a soluble guanylate cyclase activator have increased therapeutic options and potentially reduced morbidity and mortality; yet, none of the current therapies have been curative. Current clinical management of PAH has become more complex given the focus on early diagnosis, an increased number of available therapeutics within each mechanistic class, and the emergence of clinically challenging scenarios such as perioperative care. Efforts to standardize the clinical care of patients with PAH have led to the formation of multidisciplinary PAH tertiary care programs that strive to offer medical care based on peer-reviewed evidence-based, and expert consensus guidelines. Furthermore, these tertiary PAH centers often support clinical and basic science research programs to gain novel insights into the pathogenesis of PAH with the goal to improve the clinical management of this devastating disease. In this article, we discuss the clinical approach and management of PAH from the perspective of a single US-based academic institution. We provide an overview of currently available clinical guidelines and offer some insight into how we approach current controversies in clinical management of certain patient subsets. We conclude with an overview of our program structure and a perspective on research and the role of a tertiary PAH center in contributing new knowledge to the field.

Acute right ventricular failure caused by concomitant coronary and pulmonary embolism: successful treatment with endovascular coronary and pulmonary thrombectomy

Patent foramen ovale (PFO) is present in approximately 25% of the general population. PFO is characterized by intermittent shunting of blood from the right to the left atrium, especially in the context of increased right-sided filling pressures, with risk of paradoxical embolism. We describe a 69-year-old woman presenting with acute chest pain, severe dyspnoea, and acute inferolateral ST-segment elevation on the electrocardiogram. The patient was diagnosed with myocardial infarction and failure of the right cardiac ventricle, which was considered to be secondary to extensive pulmonary embolism leading to increased filling pressures and paradoxical coronary embolism. The patient underwent emergent percutaneous interventions with coronary thrombus extraction and pulmonary thrombus fragmentation and local thrombolysis. The patient was free of symptoms at follow up 6 months later and echocardiography showed substantially improved right ventricular function. We discuss issues related to the diagnosis, treatment, and secondary prevention for patients with concomitant pulmonary and coronary arterial thrombosis.

"Denervation" of autonomous nervous system in idiopathic pulmonary arterial hypertension by low-dose radiation: a case report with an unexpected outcome

Vasointestinal peptide metabolism plays a key physiological role in multimodular levels of vasodilatory, smooth muscle cell proliferative, parenchymal, and inflammatory lung reactions. In animal studies, vasointestinal peptide relaxes isolated pulmonary arterial segments from several mammalian species in vitro and neutralizes the pulmonary vasoconstrictor effect of endothelin. In some animal models, it reduces pulmonary vascular resistance in vivo and in monocrotaline-induced pulmonary hypertension. A 58-year-old woman presented with dyspnea and mild edema of the lower extremities. A bronchoscopy was performed without any suspicious findings suggesting a central tumor or other infiltrative disease. Endobronchial ultrasound revealed enlarged pulmonary arteries containing thrombi, a few enlarged lymph nodes, and enlarged mediastinal tissue anatomy with suspicion for mediastinal infiltration of a malignant process. We estimated that less than 10% of the peripheral vascular bed of the lung was involved in direct consolidated fibrosis as demonstrated in the left upper lobe apex. Further, direct involvement of fibrosis around the main stems of the pulmonary arteries was assumed to be low from positron emission tomography and magnetic resonance imaging scans. Assuming a positive influence of low-dose radiation, it was not expected that this could have reduced pulmonary vascular resistance by over two thirds of the initial result. However; it was noted that this patient had idiopathic pulmonary arterial hypertension mixed with “acute” (mediastinal) fibrosis which could have contributed to the unexpected success of reduction of pulmonary vascular resistance. To the best of our knowledge, this is the first report of successful treatment of idiopathic pulmonary arterial hypertension, probably as a result of low-dose radiation to the pulmonary arterial main stems. The patient continues to have no specific complaints concerning her idiopathic pulmonary arterial hypertension.