Management of Pulmonary Vascular Disease Associated with Congenital Left to Right Shunts: A Single Center Experience

OBJECTIVE

To describe the course and outcomes of children under 18 with left-to-right (LR) shunts and pulmonary arterial hypertension (PAH) undergoing one of two management approaches: PAH treatment prior to LR shunt repair (Treat First) and LR shunt repair first, with or without subsequent PAH treatment (Repair First).

METHODS

Retrospective single center study, conducted from September 2015 to September 2021, of children LR shunts and PAH (defined as indexed pulmonary vascular resistance (PVRi) ≥ 4WU*m2) but without Eisenmenger physiology. Patient characteristics, longitudinal hemodynamics data, PAH management, LR shunt repair, and outcomes were reviewed.

RESULTS

Of 768 patients evaluated for LR shunt closure, 51 (6.8%) had LR shunt associated PAH [median age 1.1 (0.37,5) years, median PVRi 6 (5.2,8.7) WU*m2]. Of the "Treat First" group (n=33, 65%), 27 (82%) underwent LR shunt closure and 6 (18%) did not respond to PAH therapy and did not undergo LR shunt closure. In the "Repair First" group (n=18, 35%), 12 (67%) received PAH therapy and 6 (33%) did not. Mortality rates were 6% in "Treat First" and 11% in "Repair First", follow-up of 3.4 and 2.5 years, respectively. After LR shunt closure, there was no significant change in PVRi over a median follow-up of 2 years after surgery (p=0.77).

CONCLUSIONS

In children with LR shunts and associated PAH, treatment with PAH-targeted therapy before defect repair does not appear to endanger the subjects and may have some benefit. The response to PAH-targeted therapy before shunt closure persists 2-3 years post-closure, providing valuable insights into the long-term management of these patients.

A novel interaction between aquaporin 1 and caspase-3 in pulmonary arterial smooth muscle cells

Pulmonary hypertension (PH) is a condition in which remodeling of the pulmonary vasculature leads to hypertrophy of the muscular vascular wall and extension of muscle into nonmuscular arteries. These pathological changes are predominantly due to the abnormal proliferation and migration of pulmonary arterial smooth muscle cells (PASMCs), enhanced cellular functions that have been linked to increases in the cell membrane protein aquaporin 1 (AQP1). However, the mechanisms underlying the increased AQP1 abundance have not been fully elucidated. Here we present data that establishes a novel interaction between AQP1 and the proteolytic enzyme caspase-3. In silico analysis of the AQP1 protein reveals two caspase-3 cleavage sites on its C-terminal tail, proximal to known ubiquitin sites. Using biotin proximity ligase techniques, we establish that AQP1 and caspase-3 interact in both human embryonic kidney (HEK) 293A cells and rat PASMCs. Furthermore, we demonstrate that AQP1 levels increase and decrease with enhanced caspase-3 activity and inhibition, respectively. Ultimately, further work characterizing this interaction could provide the foundation for novel PH therapeutics.NEW & NOTEWORTHY Pulmonary arterial smooth muscle cells (PASMCs) are integral to pulmonary vascular remodeling, a characteristic of pulmonary arterial hypertension (PAH). PASMCs isolated from robust animal models of disease demonstrate enhanced proliferation and migration, pathological functions associated with increased abundance of the membrane protein aquaporin 1 (AQP1). We present evidence of a novel interaction between the proteolytic enzyme caspase-3 and AQP1, which may control AQP1 abundance. These data suggest a potential new target for novel PAH therapies.

Pulmonary blood volume measured by 82Rb-PET in patients with chronic obstructive pulmonary disease: a retrospective cohort study

In patients with chronic obstructive pulmonary disease (COPD), pulmonary vascular dysfunction and destruction are observable before the onset of detectable emphysema, but it is unknown whether this is associated with central hypovolemia. We investigated if patients with COPD have reduced pulmonary blood volume (PBV) evaluated by 82Rb-positron emission tomography (PET) at rest and during adenosine-induced hyperemia. This single-center retrospective cohort study assessed 6,301 82Rb-PET myocardial perfusion imaging (MPI) examinations performed over a 6-yr period. We compared 77 patients with COPD with 44 healthy kidney donors (controls). Cardiac output ([Formula: see text]) and mean 82Rb bolus transit time (MBTT) were used to calculate PBV. [Formula: see text] was similar at rest (COPD: 3,649 ± 120 mL vs. control: 3,891 ± 160 mL, P = 0.368) but lower in patients with COPD compared with controls during adenosine infusion (COPD: 5,432 ± 124 mL vs. control: 6,185 ± 161 mL, P < 0.050). MBTT was shorter in patients with COPD compared with controls at rest (COPD: 8.7 ± 0.28 s vs. control: 11.4 ± 0.37 s, P < 0.001) and during adenosine infusion (COPD: 9.2 ± 0.28 s vs. control: 10.2 ± 0.37 s, P < 0.014). PBV was lower in patients with COPD, even after adjustment for body surface area, sex, and age at rest [COPD: 530 (29) mL vs. 708 (38) mL, P < 0.001] and during adenosine infusion [COPD: 826 (29) mL vs. 1,044 (38) mL, P < 0.001]. In conclusion, patients with COPD show evidence of central hypovolemia, but it remains to be determined whether this has any diagnostic or prognostic impact.NEW & NOTEWORTHY The present study demonstrated that patients with chronic obstructive pulmonary disease (COPD) exhibit central hypovolemia compared with healthy controls. Pulmonary blood volume may thus be a relevant physiological and/or clinical outcome measure in future COPD studies.

Pulmonary vascular disease and optical coherence tomography imaging in patients with Fontan palliation

INTRODUCTION

The Fontan procedure is the palliative procedure of choice for patients with single ventricle physiology. Pulmonary vascular disease (PVD) is an important contributor to Fontan circulatory failure.

AREAS COVERED

We review the pathophysiology of PVD in patients with Fontan palliation and share our initial experience with optical coherence tomography (OCT) in supplementing standard hemodynamics in characterizing Fontan-associated PVD. In the absence of a sub-pulmonary ventricle, low pulmonary vascular resistance (PVR; ≤2 WU/m2) is required to sustain optimal pulmonary blood flow. PVD is associated with adverse pulmonary artery (PA) remodeling resulting from the non-pulsatile low-shear low-flow circulation. Predisposing factors to PVD include impaired PA growth, endothelial dysfunction, hypercoagulable state, and increased ventricular end-diastolic pressure. OCT parameters that show promise in characterizing Fontan-associated PVD include the PA intima-to-media ratio and wall area ratio (i.e. difference between the whole-vessel area and the luminal area divided by the whole-vessel area).

EXPERT OPINION

OCT carries potential in characterizing PVD in patients with Fontan palliation. PA remodeling is marked by intimal hyperplasia, with medial regression. Further studies are required to determine the role of OCT in informing management decisions and assessing therapeutic responses.

Direct prostacyclin transition in pediatric patients with pulmonary hypertension

Pediatric patients with pulmonary arterial hypertension (PAH) are commonly treated with the prostacyclin analog treprostinil in IV, SQ, inhaled or oral form, or the prostacyclin receptor agonist selexipag. Patients who transition between these medications often follow recommendations for gradual up- and down-titrations that take place over several days in the hospital or several weeks as an outpatient. However, hospital resources are limited, and long transitions are inconvenient for patients and families. We report a case series of eight pediatric patients with PAH transitioned directly between prostacyclins with no overlapping doses. Direct medication transitions occurred in the cardiac intensive care unit (CICU), at home and in cardiology clinic. Equivalent doses for selexipag were estimated using information extrapolated from experience, published materials and selexipag study guidelines. All patients completed direct transition as planned and remained on transition dose for at least 1 week. In most cases selexipag was up-titrated at home after establishing initial transition dose. In select patients, direct prostacyclin transition in pediatric patients with PAH is safe, effective, convenient for families and reduces the use of hospital resources.

Exercise-Induced Pulmonary Hypertension in Long-Term Survivors of Congenital Diaphragmatic Hernia

OBJECTIVE

To determine the prevalence of exercise-induced pulmonary hypertension (PH) among long-survivors of congenital diaphragmatic hernia repair.

STUDY DESIGN

This is a single-center, retrospective cohort study of CDH survivors who underwent exercise stress echocardiography (ESE) at Boston Children's Hospital from January 2006 to June 2020. PH severity was assessed by echocardiogram at baseline and after exercise. Patients were categorized by right ventricular systolic pressure (RVSP) after exercise: Group 1 - no or mild PH; and Group 2 - moderate or severe PH (RVSP ≥ 60 mmHg or ≥ ½ systemic blood pressure).

RESULTS

Eighty-four patients with CDH underwent 173 ESE with median age 8.1 (4.8 - 19.1) years at first ESE. Sixty-four patients were classified as Group 1, 11 as Group 2, and 9 had indeterminate RVSP with ESE. Moderate to severe PH after exercise was found in 8 (10%) patients with no or mild PH at rest. Exercise-induced PH was associated with larger CDH defect size, patch repair, use of ECMO, supplemental oxygen at discharge, and higher WHO functional class. Higher VE/VCO2 slope, lower peak oxygen saturation, and lower percent predicted FEV1, and FEV1/FVC ratio were associated with Group 2 classification. ESE changed management in 9/11 Group 2 patients. PH was confirmed in all 5 Group 2 patients undergoing cardiac catheterization after ESE.

CONCLUSIONS

Among long-term CDH survivors, 10% had moderate-severe exercise-induced PH on ESE, indicating ongoing pulmonary vascular abnormalities. Further studies are needed to optimally define PH screening and treatment for patients with repaired CDH.

Escalating Oral Treprostinil Dose With Intravenous Treprostinil Bridging Therapy

Oral treprostinil, approved for the treatment of pulmonary arterial hypertension, remains an attractive option in combination with other medications to delay disease progression and improve exercise capacity. However, patients are often challenged with the ability to overcome adverse effects as outpatients and reach effective doses in a timely manner. We describe a case of a 47-year-old female on oral treprostinil who presented to the clinic with worsening symptoms of disease, necessitating higher dosing. This patient was previously uptitrated outpatient with oral treprostinil, which had allowed her to remain stable for years. Once uptitrated with additional intravenous therapy, the oral treprostinil dose was gradually further increased to the new goal dosage, resulting in improvements in symptoms and right ventricular function. This case highlights the versatility of dose optimization of oral treprostinil with rapid bridging through intravenous therapy.

Thoracic Applications of Spectral CT Scan

TOPIC IMPORTANCE

Thoracic imaging with CT scan has become an essential component in the evaluation of respiratory and thoracic diseases. Providers have historically used conventional single-energy CT; however, prevalence of dual-energy CT (DECT) is increasing, and as such, it is important for thoracic physicians to recognize the utility and limitations of this technology.

REVIEW FINDINGS

The technical aspects of DECT are presented, and practical approaches to using DECT are provided. Imaging at multiple energy spectra allows for postprocessing of the data and the possibility of creating multiple distinct image reconstructions based on the clinical question being asked. The data regarding utility of DECT in pulmonary vascular disorders, ventilatory defects, and thoracic oncology are presented. A pictorial essay is provided to give examples of the strengths associated with DECT.

SUMMARY

DECT has been most heavily studied in chronic thromboembolic pulmonary hypertension; however, it is increasingly being used across a wide spectrum of thoracic diseases. DECT combines morphologic and functional assessments in a single imaging acquisition, providing clinicians with a powerful diagnostic tool. Its role in the evaluation and treatment of thoracic diseases will likely continue to expand in the coming years as clinicians become more experienced with the technology.

Younger age at initiation of subcutaneous treprostinil is associated with better response in pediatric Group 1 pulmonary arterial hypertension

Children with severe Group 1 pulmonary arterial hypertension (PAH) have an unpredictable response to subcutaneous treprostinil (TRE) therapy, which may be influenced by age, disease severity, or other unknown variables at time of initiation. In this retrospective single-center cohort study, we hypothesized that younger age at TRE initiation, early hemodynamic response (a decrease in pulmonary vascular resistance by ≥30% at follow-up catheterization), and less severe baseline hemodynamics (Rp:Rs < 1.1) would each be associated with better clinical outcomes. In 40 pediatric patients with Group I PAH aged 17 days-18 years treated with subcutaneous TRE, younger age (cut-off of 6-years of age, AUC 0.824) at TRE initiation was associated with superior 5-year freedom from adverse events (94% vs. 39%, p = 0.002), better WHO functional class (I or II: 88% vs. 39% p = 0.003), and better echocardiographic indices of right ventricular function at most recent follow-up. Neither early hemodynamic response nor less severe baseline hemodynamics were associated with better outcomes. Patients who did not have a significant early hemodynamic response to TRE by first follow-up catheterization were unlikely to show subsequent improvement in PVRi (1/8, 13%). These findings may help clinicians counsel families and guide clinical decision making regarding the timing of advanced therapies.

Pulmonary hypertension in the setting of interstitial lung disease: Approach to management and treatment. A consensus statement from the Pulmonary Vascular Research Institute's Innovative Drug Development Initiative-Group 3 Pulmonary Hypertension

Pulmonary hypertension (PH) due to interstitial lung disease (ILD), a commonly encountered complication of fibrotic ILDs, is associated with significant morbidity and mortality. Until recently, the studies of pulmonary vasodilator therapy in PH-ILD have been largely disappointing, with some even demonstrating the potential for harm. This paper is part of a series of Consensus Statements from the Pulmonary Vascular Research Institute's Innovative Drug Development Initiative for Group 3 Pulmonary Hypertension, with prior publications covering pathogenesis, prevalence, clinical features, phenotyping, clinical trials, and impact of PH-ILD. It offers a comprehensive review of and a holistic approach to treatment of PH-ILD, including the management of underlying interstitial lung diseases, importance of treating the comorbidities, emphasis on importance of exercise and palliation of dyspnea, and review of the most up-to-date guidelines for referral for potential lung transplant work up. It also summarizes the prior, ongoing, and possibly future studies in treatment of the vascular derangement of this morbid condition.

Awareness Regarding Venous Thromboembolism and Pulmonary Embolism After Pregnancy and Cesarean Section in Female Population in the Aseer Region, Saudi Arabia

Introduction A pulmonary embolism (PE) occurs when an embolus that has traveled through the venous system from another part of the body obstructs an artery in the lungs. Chest pain, especially while breathing in, coughing up blood, and shortness of breath are all possible signs of PE. There could also be signs of a blood clot in the leg, like a painful, swollen, red, and warm leg. As a high-risk group, particularly during childbearing age, the aim of this study is to evaluate the general awareness of females regarding PE and identify areas of knowledge deficit and factors contributing to their awareness level. Methods A cross-sectional descriptive survey of Saudi women in general over the age of 18 was carried out. Participants were asked to respond to a structured questionnaire that was used to gather data. The questionnaire was formulated in Google Forms with an Arabic translation of the form and the link generated and was sent to each participant for completion. In total, 827 respondents filled out the survey with accurate and complete information. Results The study comprised 827 female volunteers, with a mean age of 33.2 ± 9.4 years, ranging in age from 15 to 60. Additionally, 52.8% of the female sample had graduated from college, compared to about 4% who were illiterate. In general, 40.2% of the girls knew everything there was to know about PE. Conclusions According to the study's findings, the public female population knew less about PE overall - that is, about risk factors, symptoms, and preventive measures. As more knowledge about the dangers, causes, prevention, diagnosis, and treatment of PE becomes available, it is imperative that healthcare professionals translate and actively distribute this information to the public, particularly to women.

Regional Variation in Pulmonary Arterial Hypertension in the United States: The Pulmonary Hypertension Association Registry

Rationale: Pulmonary arterial hypertension (PAH) is a heterogeneous disease within a complex diagnostic and treatment environment. Other complex heart and lung diseases have substantial regional variation in characteristics and outcomes; however, this has not been previously described in PAH. Objectives: To identify baseline differences between U.S. census regions in the characteristics and outcomes for participants in the Pulmonary Hypertension Association Registry (PHAR). Methods: Adults with PAH were divided into regional groups (Northeast, South, Midwest, and West), and baseline differences between census regions were presented. Kaplan-Meier survival analyses and Cox proportional hazards were used to estimate the association between region and mortality in unadjusted and adjusted models. Results: Substantial differences by census regions were seen in age, race, ethnicity, marital status, employment, insurance payor breakdown, active smoking, and current alcohol use. Differences were also seen in PAH etiology and baseline 6-minute walk distance test results. Treatment characteristics varied by census region, and mortality appeared to be lower in PHAR participants in the West (hazard ratio, 0.60; 95% confidence interval, 0.43-0.83, P = 0.005). This difference was not readily explained by differences in demographic characteristics, PAH etiology, baseline severity, baseline medication regimen, or disease prevalence. Conclusions: The present study suggests significant regional variation among participants at accredited pulmonary vascular disease centers in multiple baseline characteristics and mortality. This variation may have implications for clinical research planning and represent an important focus for further study to better understand whether there are remediable care aspects that can be addressed in the pursuit of providing equitable care in the United States.

Is low-risk status a surrogate outcome in pulmonary arterial hypertension? An analysis of three randomised trials

BACKGROUND

Targeting short-term improvements in multicomponent risk scores for mortality in patients with pulmonary arterial hypertension (PAH) could result in improved long-term outcomes. We aimed to determine whether PAH risk scores were adequate surrogates for clinical worsening or mortality outcomes in PAH randomised clinical trials (RCTs).

METHODS

We performed an individual participant data meta-analysis of RCTs selected from PAH trials provided by the US Food and Drug Administration (FDA). We calculated predicted risk using the COMPERA, COMPERA 2.0, non-invasive FPHR, REVEAL 2.0, and REVEAL Lite 2 risk scores. The primary outcome of interest was time to clinical worsening, a composite endpoint composed of any of the following events: all-cause death, hospitalisation for worsening PAH, lung transplantation, atrial septostomy, discontinuation of study treatment (or study withdrawal) for worsening PAH, initiation of parenteral prostacyclin analogue therapy, or decrease of at least 15% in 6-min walk distance from baseline, combined with either worsening of WHO functional class from baseline or the addition of an approved PAH treatment. The secondary outcome of interest was time to all-cause mortality. We assessed the surrogacy of these risk scores, parameterised as attainment of low-risk status by 16 weeks, for improvement in long-term clinical worsening and survival using mediation and meta-analysis frameworks.

FINDINGS

Of 28 trials received from the FDA, three RCTs (AMBITION, GRIPHON, and SERAPHIN; n=2508) had the data necessary to assess long-term surrogacy. The mean age was 49 years (SD 16), 1956 (78%) participants were women, 1704 (68%) were classified as White, and 280 (11%) were Hispanic or Latino. 1388 (55%) of 2503 participants with available data had idiopathic PAH and 776 (31%) of 2503 had PAH associated with connective tissue disease. In a mediation analysis, the proportions of treatment effects explained by attainment of low-risk status ranged only from 7% to 13%. In a meta-analysis of trial-regions, the treatment effects on low-risk status were not predictive of the treatment effects on time to clinical worsening (R2 values 0·01-0·19) nor the treatment effects on time to all-cause mortality (R2 values 0-0·2). A leave-one-out analysis suggested that the use of these risk scores as surrogates might lead to biased inferences regarding the effect of therapies on clinical outcomes in PAH RCTs. Results were similar when using absolute risk scores at 16 weeks as the potential surrogates.

INTERPRETATION

Multicomponent risk scores have utility for the prediction of outcomes in patients with PAH. Clinical surrogacy for long-term outcomes cannot be inferred from observational studies of outcomes. Our analyses of three PAH trials with long-term follow-up suggest that further study is necessary before using these or other scores as surrogate outcomes in PAH RCTs or clinical care.

FUNDING

Cardiovascular Medical Research and Education Fund, US National Institutes of Health.

Effects of inhaled nitric oxide on Fontan hemodynamics in adults

The pulmonary vasculature plays a pivotal role in the nonpulsatile systemic venous return post-Fontan palliation. Elevated pulmonary vascular resistance index (PVRi) carries a worse prognosis post-Fontan, but the benefits of pulmonary vasodilators remain controversial. Moreover, the potential for worsening ventricular filling pressures with pulmonary vasodilation has been highlighted. We reviewed our experience with inhaled nitric oxide (iNO) administration during cardiac catheterization in 30 adults (age 32.7 ± 8.5 years) post-Fontan. The main findings of the study are: (1) iNO decreased pulmonary artery pressures, transpulmonary gradient, and PVRi without increasing pulmonary artery wedge pressure, (2) cardiac index was unchanged with iNO, and (3) different from acquired left heart disease, iNO did not result in further elevations in pulmonary artery wedge pressure in those with elevated ventricular filling pressures. iNO administration in adults post-Fontan was safe; whether baseline PVRi and response to iNO could be used to predict response to pulmonary vasodilators post-Fontan requires further investigation.

Clinical features of pulmonary arterial hypertension associated with systemic sclerosis

Systemic sclerosis is an autoimmune disorder of the connective tissue characterized by disordered inflammation and fibrosis leading to skin thickening and visceral organ complications. Pulmonary involvement, in the form of pulmonary arterial hypertension and/or interstitial lung disease, is the leading cause of morbidity and mortality among individuals with scleroderma. There are no disease-specific therapies for pulmonary involvement of scleroderma, and pulmonary arterial hypertension in this cohort has typically been associated with worse outcomes and less clinical response to modern therapy compared to other forms of Group I pulmonary hypertension in the classification from the World Symposium on Pulmonary Hypertension. Ongoing research aims to delineate how pathologic microvascular remodeling and fibrosis contribute to this poor response and offer a window into future therapeutic targets.

Pulmonary Hypertension: A Contemporary Review

Major advances in pulmonary arterial hypertension, pulmonary hypertension (PH) associated with lung disease, and chronic thromboembolic PH cast new light on the pathogenetic mechanisms, epidemiology, diagnostic approach, and therapeutic armamentarium for pulmonary vascular disease. Here, we summarize key basic, translational, and clinical PH reports, emphasizing findings that build on current state-of-the-art research. This review includes cutting-edge progress in translational pulmonary vascular biology, with a guide to the diagnosis of patients in clinical practice, incorporating recent PH definition revisions that continue emphasis on early detection of disease. PH management is reviewed including an overview of the evolving considerations for the approach to treatment of PH in patients with cardiopulmonary comorbidities, as well as a discussion of the groundbreaking sotatercept data for the treatment of pulmonary arterial hypertension.

Severity of preterm birth and the risk of pulmonary hypertension in childhood: A population-based cohort study in Sweden

BACKGROUND

Preterm birth (<37 completed gestational weeks) has been linked to pulmonary hypertension (PH), but the relationship to severity of preterm birth has not been studied.

OBJECTIVES

We investigated associations between extremely (<28 weeks), very (28-31 weeks), moderately (32-36 weeks) preterm birth, early-term birth (37-38 weeks) and later PH. Additionally, we explored associations between birthweight for gestational age and PH.

METHODS

This registry-based cohort study followed 3.1 million individuals born in Sweden (1987-2016) from 1 up to a maximum of 30 years of age. The outcome was diagnosis or death from PH in national health registers. Adjusted hazard ratios (HR) were estimated using Cox regression analysis. Unadjusted and confounder-adjusted incidence rate differences were also calculated.

RESULTS

Of 3,142,812 individuals, there were 543 cases of PH (1.2 per 100,000 person-years), 153 of which in individuals without malformations. Compared with individuals born at 39 weeks, adjusted HRs with 95% confidence interval (CI) for PH for extremely, moderately, and very preterm birth were 68.78 (95% CI 49.49, 95.57), 13.86 (95% CI 9.27, 20.72) and 3.42 (95% CI 2.46, 4.74), respectively, and for early-term birth 1.74 (1.31, 2.32). HRs were higher in subjects without malformations. There were 90 additional cases of PH per 100,000 person-years in the extremely preterm group (50 after excluding malformations). Very small for gestational age (below 2 SD from estimated birthweight for gestational age and sex) was also associated with increased risk of PH (adjusted HR 2.02, 95% CI 1.14, 3.57).

CONCLUSIONS

We found an inverse association between gestational age and later PH, but the incidence and absolute risks are low. The severity of preterm birth adds clinically relevant information to the assessment of cardiovascular risks in childhood.

Natural history of chronic thromboembolic pulmonary disease with no or mild pulmonary hypertension

BACKGROUND

We describe baseline characteristics, disease progression and mortality in chronic thromboembolic pulmonary disease patients as a function of mean pulmonary artery pressure (mPAP) according to new and previous definitions of pulmonary hypertension.

METHODS

All patients diagnosed with chronic thromboembolic pulmonary disease between January, 2015 and December, 2019 were dichotomized according to initial mPAP: ≤ 20 mmHg ('normal') vs 21-24 mmHg ('mildly-elevated'). Baseline features were compared between the groups, and pairwise analysis performed to determine changes in clinical endpoints at 1-year, excluding those who underwent pulmonary endarterectomy or did not attend follow-up. Mortality was assessed for the whole cohort over the entire study period.

RESULTS

One hundred thirteen patients were included; 57 had mPAP ≤ 20 mmHg and 56 had mPAP 21-24 mmHg. Normal mPAP patients had lower pulmonary vascular resistance (1.6 vs 2.5WU, p < 0.01) and right ventricular end-diastolic pressure (5.9 vs 7.8 mmHg, p < 0.01) at presentation. At 3 years, no major deterioration was seen in either group. No patients were treated with pulmonary artery vasodilators. Eight had undergone pulmonary endarterectomy. Over 37 months median follow-up, mortality was 7.0% in the normal mPAP group and 8.9% in the mildly-elevated mPAP group. Cause of death was malignancy in 62.5% of cases.

CONCLUSIONS

Chronic thromboembolic pulmonary disease patients with mild pulmonary hypertension have statistically higher right ventricular end-diastolic pressure and pulmonary vascular resistance than those with mPAP ≤ 20 mmHg. Baseline characteristics were otherwise similar. Neither group displayed disease progression on non-invasive tests up to 3 years. Mortality over 37 months follow-up is 8%, and mainly attributable to malignancy. Further prospective study is required to validate these findings.

Pulmonary Hypertension in Infants and Children with Vein of Galen Malformation and Association with Clinical Outcomes

OBJECTIVE

To assess the extent and resolution of pulmonary hypertension (PH), cardiovascular factors, and echocardiographic findings associated with mortality in infants and children with vein of Galen malformation (VOGM).

STUDY DESIGN

We performed a retrospective review of 49 consecutive children with VOGM admitted to Boston Children's Hospital from 2007 to 2020. Patient characteristics, echocardiographic data, and hospital course were analyzed for 2 cohorts based on age at presentation to Boston Children's Hospital: group 1 (age ≤60 days) or group 2 (age >60 days).

RESULTS

Overall hospital survival was 35 of 49 (71.4%); 13 of 26 (50%) in group 1 and 22 of 23 (96%) in group 2 (P < .001). High-output PH (P = .01), cardiomegaly (P = .011), intubation (P = .019), and dopamine use (P = .01) were significantly more common in group 1 than group 2. Among patients in group 1, congestive heart failure (P = .015), intubation (P < .001), use of inhaled nitric oxide (P = .015) or prostaglandin E1 (P = .030), suprasystemic PH (P = .003), and right-sided dilation were significantly associated with mortality; in contrast, left ventricular volume and function, structural congenital heart disease, and supraventricular tachycardia were not associated. Inhaled nitric oxide achieved no clinical benefit in 9 of 11 treated patients. Resolution of PH was associated with overall survival (P < .001).

CONCLUSIONS

VOGM remains associated with substantial mortality among infants presenting at ≤60 days of life owing to factors associated with high output PH. Resolution of PH is an indicator associated with survival and a surrogate end point for benchmarking outcomes.

Safety and tolerability of continuous inhaled iloprost in critically ill pediatric pulmonary hypertension patients: A retrospective case series

Inhaled iloprost (iILO) has shown efficacy in treating patients with hypoxic lung disease and pulmonary hypertension, inducing selective pulmonary vasodilation and improvement in oxygenation. However, its short elimination half-life of 20-30 min necessitates frequent intermittent dosing (6-9 times per day). Thus, the administration of iILO via continuous nebulization represents an appealing method of drug delivery in the hospital setting. The objectives are: (1) describe our continuous iILO delivery methodology and safety profile in mechanically ventilated pediatric pulmonary hypertension patients; and (2) characterize the initial response of iILO in these pediatric patients currently receiving iNO. Continuous iILO was delivered and well tolerated (median 6 days; range 1-94) via tracheostomy or endotracheal tube using the Aerogen® mesh nebulizer system coupled with a Medfusion® 400 syringe pump. No adverse events or delivery malfunctions were reported. Initiation of iILO resulted in an increase in oxygen saturation from 81.4 ± 8.6 to 90.8 ± 4.1%, p < 0.05. Interestingly, prior iNO therapy for >1 day resulted in a higher response rate to iILO (as defined as a ≥ 4% increase in saturations) compared to those receiving iNO <1 day (85% vs. 50%, p = 0.06). When the use of iILO is considered, continuous delivery represents a safe, less laborious alternative and concurrent treatment with iNO should not be considered a contraindication. However, given the retrospective design and small sample size, this study does not allow the evaluation of the efficacy of continuous iILO on outcomes beyond the initial response. Thus, a prospective study designed to evaluate the efficacy of continuous iILO is necessary.

Vascular pathobiology of pulmonary hypertension

Pulmonary hypertension (PH), increased blood pressure in the pulmonary arteries, is a morbid and lethal disease. PH is classified into several groups based on etiology, but pathological remodeling of the pulmonary vasculature is a common feature. Endothelial cell dysfunction and excess smooth muscle cell proliferation and migration are central to the vascular pathogenesis. In addition, other cell types, including fibroblasts, pericytes, inflammatory cells and platelets contribute as well. Herein, we briefly note most of the main cell types active in PH and for each cell type, highlight select signaling pathway(s) highly implicated in that cell type in this disease. Among others, the role of hypoxia-inducible factors, growth factors (e.g., vascular endothelial growth factor, platelet-derived growth factor, transforming growth factor-β and bone morphogenetic protein), vasoactive molecules, NOTCH3, Kruppel-like factor 4 and forkhead box proteins are discussed. Additionally, deregulated processes of endothelial-to-mesenchymal transition, extracellular matrix remodeling and intercellular crosstalk are noted. This brief review touches upon select critical facets of PH pathobiology and aims to incite further investigation that will result in discoveries with much-needed clinical impact for this devastating disease.

Pathogenesis, clinical features, and phenotypes of pulmonary hypertension associated with interstitial lung disease: A consensus statement from the Pulmonary Vascular Research Institute's Innovative Drug Development Initiative - Group 3 Pulmonary Hypertension

Pulmonary hypertension (PH) is a frequent complication of interstitial lung disease (ILD). Although PH has mostly been described in idiopathic pulmonary fibrosis, it can manifest in association with many other forms of ILD. Associated pathogenetic mechanisms are complex and incompletely understood but there is evidence of disruption of molecular and genetic pathways, with panvascular histopathologic changes, multiple pathophysiologic sequelae, and profound clinical ramifications. While there are some recognized clinical phenotypes such as combined pulmonary fibrosis and emphysema and some possible phenotypes such as connective tissue disease associated with ILD and PH, the identification of further phenotypes of PH in ILD has thus far proven elusive. This statement reviews the current evidence on the pathogenesis, recognized patterns, and useful diagnostic tools to detect phenotypes of PH in ILD. Distinct phenotypes warrant recognition if they are characterized through either a distinct presentation, clinical course, or treatment response. Furthermore, we propose a set of recommendations for future studies that might enable the recognition of new phenotypes.

Is iron deficiency caused by BMPR2 mutations or dysfunction in pulmonary arterial hypertension patients?

Iron deficiency is common in idiopathic and heritable pulmonary arterial hypertension patients (I/HPAH). A previous report suggested a dysregulation of the iron hormone hepcidin, which is controlled by BMP/SMAD signaling involving the bone morphogenetic protein receptor 2 (BMPR-II). Pathogenic variants in the BMPR2 gene are the most common cause of HPAH. Their effect on patients' hepcidin levels has not been investigated. The aim of this study was to assess whether iron metabolism and regulation of the iron regulatory hormone hepcidin was disturbed in I/HPAH patients with and without a pathogenic variant in the gene BMPR2 compared to healthy controls. In this explorative, cross-sectional study hepcidin serum levels were quantified by enzyme-linked immunosorbent assay. We measured iron status, inflammatory parameters and hepcidin modifying proteins such as IL6, erythropoietin, and BMP2, BMP6 in addition to BMPR-II protein and mRNA levels. Clinical routine parameters were correlated with hepcidin levels. In total 109 I/HPAH patients and controls, separated into three groups, 23 BMPR2 variant-carriers, 56 BMPR2 noncarriers and 30 healthy controls were enrolled. Of these, 84% had iron deficiency requiring iron supplementation. Hepcidin levels were not different between groups and corresponded to the degree of iron deficiency. The levels of IL6, erythropoietin, BMP2, or BMP6 showed no correlation with hepcidin expression. Hence, iron homeostasis and hepcidin regulation was largely independent from these parameters. I/HPAH patients had a physiologically normal iron regulation and no false elevation of hepcidin levels. Iron deficiency was prevalent albeit independent of pathogenic variants in the BMPR2 gene.

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

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

Utility of Conventional but Late Pulmonary Artery Banding in Complex Cyanotic Congenital Heart Disease in a Toddler - A Single Case Scenario

Newborns with untreated single ventricles develop pulmonary vascular diseases early in their lives. At that age, during the first eight weeks after birth, clinicians perform pulmonary artery (PA) banding to reduce the blood flow to the lung, decreasing the likelihood of future high vascular resistance or pressure. PA banding is also considered an initial stage in the process of single ventricle palliation procedures. We report a case of a 16-month-old toddler (7 kg) with room air saturation of 82%, diagnosed with tricuspid valve atresia, large atrial and ventricular septal defect, and hypoplastic right ventricle with severe pulmonary arterial hypertension. The baby underwent a successful surgical procedure of PA banding and was discharged after 13 days of hospital stay with a room air saturation of 89%. This case highlighted the benefit of PA banding beyond the stipulated period.

Pulmonary Hypertension in Children with Down Syndrome: Results from the Pediatric Pulmonary Hypertension Network Registry

OBJECTIVE

To characterize distinct comorbidities, outcomes, and treatment patterns in children with Down syndrome and pulmonary hypertension in a large, multicenter pediatric pulmonary hypertension registry.

STUDY DESIGN

We analyzed data from the Pediatric Pulmonary Hypertension Network (PPHNet) Registry, comparing demographic and clinical characteristics of children with Down syndrome and children without Down syndrome. We examined factors associated with pulmonary hypertension resolution and a composite outcome of pulmonary hypertension severity in the cohort with Down syndrome.

RESULTS

Of 1475 pediatric patients with pulmonary hypertension, 158 (11%) had Down syndrome. The median age at diagnosis of pulmonary hypertension in patients with Down syndrome was 0.49 year (IQR, 0.21-1.77 years), similar to that in patients without Down syndrome. There was no difference in rates of cardiac catheterization and prescribed pulmonary hypertension medications in children with Down syndrome and those without Down syndrome. Comorbidities in Down syndrome included congenital heart disease (95%; repaired in 68%), sleep apnea (56%), prematurity (49%), recurrent respiratory exacerbations (35%), gastroesophageal reflux (38%), and aspiration (31%). Pulmonary hypertension resolved in 43% after 3 years, associated with a diagnosis of pulmonary hypertension at age <6 months (54% vs 29%; P = .002) and a pretricuspid shunt (65% vs 38%; P = .02). Five-year transplantation-free survival was 88% (95% CI, 80%-97%). Tracheostomy (hazard ratio [HR], 3.29; 95% CI, 1.61-6.69) and reflux medication use (HR, 2.08; 95% CI, 1.11-3.90) were independently associated with a composite outcome of severe pulmonary hypertension.

CONCLUSIONS

Despite high rates of cardiac and respiratory comorbidities that influence the severity of pulmonary hypertension, children with Down syndrome-associated pulmonary hypertension generally have a survival rate similar to that of children with non-Down syndrome-associated pulmonary hypertension. Resolution of pulmonary hypertension is common but reduced in children with complicated respiratory comorbidities.

Hemodynamic assessment of transitioning from parenteral prostacyclin to selexipag in pediatric pulmonary hypertension

Despite the increase in therapeutic options, parenteral prostacyclins remain the cornerstone in the medical management of pulmonary arterial hypertension (PAH). While the use of parenteral prostacyclins in pediatric patients is well documented, less is known about alternative drug delivery methods such as enteral administration. Given that parenteral routes of prostacyclin administration (IV or SC) are invariably accompanied by complicated logistics and lifestyle compromises, enteral prostacyclin administration represents an attractive treatment option. Selexipag (Uptravi®) was approved for adults PAH in 2015. There is limited data on the hemodynamic efficacy of transitioning from parenteral prostacyclins to selexipag, particularly in the pediatric population. We report 11 pediatric PAH patients who underwent this transition, in which 10 had complete cardiac catheterization data before and following the transition to selexipag. All patients/families reported an improvement in quality of life, and the transitions occurred without adverse effects. However, 3 of the 11 (27%) did not tolerate the transition; two for worsening hemodynamics, and one for acute right ventricular failure in the setting of an intercurrent illness. In addition, the transition to selexipag was associated with a modest increase in pulmonary vascular resistance index (6/10) and decrease in cardiac index (6/10) in some patients. Selexipag use in pediatric PAH represents a significant addition to our therapeutic arsenal, and its use provides a meaningful improvement in quality of life compared with other prostacyclin formulations. However, when goals of care include aggressive disease management, a decision between improved quality of life and possible adverse outcomes must be considered, and its substitution should include cautious, close, long-term follow-up.

Exercise and hypoxia unmask pulmonary vascular disease and right ventricular dysfunction in a 10-12 week old swine model of neonatal oxidative injury

Abstract

Prematurely born young adults who experienced neonatal oxidative injury (NOI) of the lungs have increased incidence of cardiovascular disease. Here, we investigated the long‐term effects of NOI on cardiopulmonary function in piglets at the age of 10–12 weeks. To induce NOI, term‐born piglets (1.81 ± 0.06 kg) were exposed to hypoxia (10–12% FiO2), within 2 days after birth, and maintained for 4 weeks or until symptoms of heart failure developed (range 16–28 days), while SHAM piglets were normoxia raised. Following recovery (>5 weeks), NOI piglets were surgically instrumented to measure haemodynamics during hypoxic challenge testing (HCT) and exercise with modulation of the nitric‐oxide system. During exercise, NOI piglets showed a normal increase in cardiac index, but an exaggerated increase in pulmonary artery pressure and a blunted increase in left atrial pressure – suggesting left atrial under‐filling – consistent with an elevated pulmonary vascular resistance (PVR), which correlated with the duration of hypoxia exposure. Moreover, hypoxia duration correlated inversely with stroke volume (SV) during exercise. Nitric oxide synthase inhibition and HCT resulted in an exaggerated increase in PVR, while the PVR reduction by phosphodiesterase‐5 inhibition was enhanced in NOI compared to SHAM piglets. Finally, within the NOI piglet group, prolonged duration of hypoxia was associated with a better maintenance of SV during HCT, likely due to the increase in RV mass. In conclusion, duration of neonatal hypoxia appears an important determinant of alterations in cardiopulmonary function that persist further into life. These changes encompass both pulmonary vascular and cardiac responses to hypoxia and exercise.

Key points

Children who suffered from neonatal oxidative injury, such as very preterm born infants, have increased risk of cardiopulmonary disease later in life.

Risk stratification requires knowledge of the mechanistic underpinning and the time course of progression into cardiopulmonary disease.

Exercise and hypoxic challenge testing showed that 10‐ to 12‐week‐old swine that previously experienced neonatal oxidative injury had increased pulmonary vascular resistance and nitric oxide dependency.

Duration of neonatal oxidative injury was a determinant of structural and functional cardiopulmonary remodelling later in life.

Remodelling of the right ventricle, as a result of prolonged neonatal oxidative injury, resulted in worse performance during exercise, but enabled better performance during the hypoxic challenge test.

Increased nitric oxide dependency together with age‐ or comorbidity‐related endothelial dysfunction may contribute to predisposition to pulmonary hypertension later in life.

Distinguishing exercise intolerance in early-stage pulmonary hypertension with invasive exercise hemodynamics: Rest VE /VCO2 and ETCO2 identify pulmonary vascular disease

BACKGROUND

Among subjects with exercise intolerance and suspected early-stage pulmonary hypertension (PH), early identification of pulmonary vascular disease (PVD) with noninvasive methods is essential for prompt PH management.

HYPOTHESIS

Rest gas exchange parameters (minute ventilation to carbon dioxide production ratio: VE /VCO2 and end-tidal carbon dioxide: ETCO2 ) can identify PVD in early-stage PH.

METHODS

We conducted a retrospective review of 55 subjects with early-stage PH (per echocardiogram), undergoing invasive exercise hemodynamics with cardiopulmonary exercise test to distinguish exercise intolerance mechanisms. Based on the rest and exercise hemodynamics, three distinct phenotypes were defined: (1) PVD, (2) pulmonary venous hypertension, and (3) noncardiac dyspnea (no rest or exercise PH). For all tests, *p < .05 was considered statistically significant.

RESULTS

The mean age was 63.3 ± 13.4 years (53% female). In the overall cohort, higher rest VE /VCO2 and lower rest ETCO2 (mm Hg) correlated with high rest and exercise pulmonary vascular resistance (PVR) (r ~ 0.5-0.6*). On receiver-operating characteristic analysis to predict PVD (vs. non-PVD) subjects with noninvasive metrics, area under the curve for pulmonary artery systolic pressure (echocardiogram) = 0.53, rest VE /VCO2  = 0.70* and ETCO2  = 0.73*. Based on this, optimal thresholds of rest VE /VCO2  > 40 mm Hg and rest ETCO2  < 30 mm Hg were applied to the overall cohort. Subjects with both abnormal gas exchange parameters (n = 12, vs. both normal parameters, n = 19) had an exercise PVR 5.2 ± 2.6* (vs. 1.9 ± 1.2), mPAP/CO slope with exercise 10.2 ± 6.0* (vs. 2.9 ± 2.0), and none included subjects from the noncardiac dyspnea group.

CONCLUSIONS

In a broad cohort of subjects with suspected early-stage PH, referred for invasive exercise testing to distinguish mechanisms of exercise intolerance, rest gas exchange parameters (VE /VCO2  > 40 mm Hg and ETCO2  < 30 mm Hg) identify PVD.

Pulmonary artery acceleration time in young children is determined by heart rate and transpulmonary gradient but not by pulmonary blood flow: A simultaneous echocardiography-cardiac catheterization study

INTRODUCTION

Pulmonary artery acceleration time (PAAT) is considered useful for the non-invasive evaluation of pulmonary artery pressure (PAP) and pulmonary vascular resistance (PVR). PAAT is dependent on PAP, PVR, pulmonary artery compliance, stroke volume, and heart rate. Its relative dependency on these determinants may differ between young and older children, raising uncertainty regarding its utility in young children. We aim to identify the primary determinants of the PAAT in children less than 36 months undergoing cardiac catheterization and its utility for the diagnosis of elevated PVR.

METHODS

We prospectively studied 42 children undergoing cardiac catheterization and simultaneous echocardiography. We determined the correlations of PAAT to the above-mentioned determinants and evaluated receiver operator characteristic (ROC) curves for diagnosis of PVR indexed to body surface area (PVRi) ≥3 Wu*m² .

RESULTS

Median age was 11.5 (IQR 5.2, 21.2) months. Moderate correlations were found between PAAT and mean PAP (R = -.66, p < .001), PVRi (R = -.54, p = .004), pulmonary artery compliance (R = .65, p < .001), transpulmonary gradient (R = -.67, p < .001), stroke volume (R = .61, p = .002), and heart rate (R = -.63, p < .001). In multivariate regression modeling, only transpulmonary gradient and heart rate were independent determinants of PAAT. PAAT ≤77 msec had acceptable utility for diagnosing PVRi ≥ 3 Wu*m² (AUC .8 [.64, .95], n = 36), low sensitivity (59%), and excellent specificity (94%).

CONCLUSION

Transpulmonary gradient and heart rate, but not pulmonary blood flow, are important determinants of PAAT in children <36 months undergoing cardiac catheterization. PAAT has low sensitivity for diagnosing elevated PVRi, therefore, should not be solely relied upon in screening for elevated PVRi in young children.

Pulmonary thromboendarterectomy: The Marie Lannelongue Hospital experience

BACKGROUND

Targeted medical therapy and balloon pulmonary angioplasty (BPA) entered the field of chronic thromboembolic pulmonary hypertension (CTEPH) treatment in the early 2010's. Multimodal therapy is emerging as the new gold standard for CTEPH management. Whether this change of paradigm impacted early outcomes of pulmonary endarterectomy (PEA) remains unknown. Our aim is to report our surgical experience in the era of CTEPH multimodal management.

METHODS

Patients who underwent PEA between 2016 and 2020 were included in the study. Early outcomes were described and compared between three groups of patients: PEA alone, PEA after targeted medical therapy induction and PEA after BPA.

RESULTS

A total of 418 patients, 225 males and 193 females, with a mean age of 59±14 years were included in the study. 336 patients underwent PEA alone, 69 after medical targeted therapy induction and 13 after unilateral BPA. Baseline preoperative pulmonary vascular resistance [4.99 (IQR, 1.71-8.48), 6.21 (IQR, 4.37-8.1), 5.03 (IQR, 4.44-7.19) wood units (WU), P=0.230, respectively] and PEA effectiveness [% decrease mean pulmonary artery pressure (mPAP), 24 (IQR, 7-42), 25 (IQR, 7-35), 23 (IQR, 3-29), P=0.580] did not differ between groups. Compared to PEA alone and PEA+BPA, the medical therapy induction group represented the most challenging group with higher baseline mPAP (45±10 vs. 42±11 and 43±11 mmHg, P=0.047), longer circulatory arrest time (30.1±15 vs. 26.6±10 and 19.6±6 min, P=0.005), higher post-PEA extracorporeal membrane oxygenation use (20.6% vs. 8.7 and 9.1%, P=0.004), higher duration on mechanical ventilation [4 (IQR, 1-12) vs. 1 (IQR, 0.5-5) and 2 (IQR, 1-3) days, P=0.005], higher complication rate (85.5% vs. 74.6% and 76.9%, P=0.052) and higher 90-day mortality (13% vs. 3.9% and 0%, P=0.002). Compared to PEA and PEA+ medical therapy induction groups, patients in the BPA induction group were older [72 (IQR, 62-76) vs. 60 (IQR, 48-69) and 62 (IQR, 52-72) years, P=0.005], and underwent shorter cardiopulmonary bypass (191.9±47.9 vs. 222±107.2 and 236.8±46.4 min, P<0.001), aortic cross clamping (54.8±21 vs. 82.7±31.4 and 80.1±32.9 min, P=0.002) and circulatory arrest time (19.6±6.2 vs. 26.6±10.8 and 30.1±15.1 min, P=0.008).

CONCLUSIONS

Multimodal therapy approach to CTEPH patients did not affect effectiveness of PEA. Medical therapy and BPA could act in synergy with surgery to treat more challenging patients.

Interplay of Low-Density Lipoprotein Receptors, LRPs, and Lipoproteins in Pulmonary Hypertension

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LDLR regulates oxidized LDL level, which is increased in lung and blood from PAH patients.

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LRP1 preserving vascular homeostasis is decreased in PAH patients.

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LRP5/6 regulating Wnt signaling is upregulated in PH.

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The LRP8 (aka ApoER2) ligand ApoE protects from PAH.

The low-density lipoprotein receptor (LDLR) gene family includes LDLR, very LDLR, and LDL receptor–related proteins (LRPs) such as LRP1, LRP1b (aka LRP-DIT), LRP2 (aka megalin), LRP4, and LRP5/6, and LRP8 (aka ApoER2). LDLR family members constitute a class of closely related multifunctional, transmembrane receptors, with diverse functions, from embryonic development to cancer, lipid metabolism, and cardiovascular homeostasis. While LDLR family members have been studied extensively in the systemic circulation in the context of atherosclerosis, their roles in pulmonary arterial hypertension (PAH) are understudied and largely unknown. Endothelial dysfunction, tissue infiltration of monocytes, and proliferation of pulmonary artery smooth muscle cells are hallmarks of PAH, leading to vascular remodeling, obliteration, increased pulmonary vascular resistance, heart failure, and death. LDLR family members are entangled with the aforementioned detrimental processes by controlling many pathways that are dysregulated in PAH; these include lipid metabolism and oxidation, but also platelet-derived growth factor, transforming growth factor β1, Wnt, apolipoprotein E, bone morpohogenetic proteins, and peroxisome proliferator-activated receptor gamma. In this paper, we discuss the current knowledge on LDLR family members in PAH. We also review mechanisms and drugs discovered in biological contexts and diseases other than PAH that are likely very relevant in the hypertensive pulmonary vasculature and the future care of patients with PAH or other chronic, progressive, debilitating cardiovascular diseases.

Comparison of forehead and finger oximetry sensors during the six minute walk test

BACKGROUND

Measurement of oxygen saturation (S_pO₂) during the 6 minute walk test (6MWT) could be impacted by the measurement site.

AIMS

To compare S_pO₂ and heart rate (HR) between forehead and finger sensors during the 6MWT. Sensor readings were also to be compared for signal quality and with capillary blood gas (CBG) pre and post 6MWT.

METHOD

80 subjects with pulmonary vascular disease (PVD) and/or interstitial lung disease (ILD) performed the 6MWT. Pulse oximetry was recorded at 30 s intervals. CBG was taken pre and post 6MWT to determine capillary oxygen saturation (S_CO₂).

RESULTS

The forehead sensor recorded higher values for S_pO₂ (p < 0.001) and HR (p < 0.01) compared with the finger sensor during the 6MWT. For both sensors, the demonstrated bias compared to CBG post 6MWT was higher and more variable in subjects who desaturated. During the 6MWT there was a higher occurrence (p < 0.001) of poor signal quality in the finger sensor compared with the forehead sensor.

CONCLUSION

This study suggests that the sensor site can impact pulse oximetry readings. The variance in bias suggests pulse oximetry may not accurately reflect S_CO₂ measurements particularly in subjects who desaturate during 6MWT.

Tadalafil for veterans with chronic obstructive pulmonary disease-pulmonary hypertension: A multicenter, placebo-controlled randomized trial

Treating Veterans with chronic obstructive pulmonary disease complicated by pulmonary hypertension (COPD-PH) using phosphodiesterase type-5 inhibitor pharmacotherapy is common, but efficacy data are lacking. To address this further, patients with COPD-PH from five Department of Veterans Affairs hospitals were randomized (1∶1) to receive placebo or oral tadalafil (40 mg/day) for 12 months. The primary endpoint was changed from baseline in 6-min walk distance at 12 months. Secondary endpoints included change from baseline in pulmonary vascular resistance, mean pulmonary artery pressure, and symptom burden by the University of California San Diego shortness of breath questionnaire scale at 6 months. A total of 42 subjects (all male; 68 ± 7.6 years old) were randomized to placebo (N = 14) or tadalafil (N = 28). The group imbalance was related to under-enrollment. Compared to placebo, no significant difference was observed in the tadalafil group for change from the primary endpoint or change in mean pulmonary artery pressure or pulmonary vascular resistance from baseline at 6 months. A clinically meaningful improvement was observed in the secondary endpoint of shortness of breath questionnaire score in the tadalafil versus placebo group at 6 months. There was no significant difference in major adverse events between treatment groups, and tadalafil was well tolerated overall. For Veterans with COPD-PH enrolled in this study, once-daily treatment with tadalafil did not improve 6-min walk distance or cardiopulmonary hemodynamics although a decrease in shortness of breath was observed. Under-enrollment and imbalanced randomization confound interpreting conclusions from this clinical trial and limit the generalization of our findings.

Murine models of sickle cell disease and beta-thalassemia demonstrate pulmonary hypertension with distinctive features

Sickle cell anemia and β-thalassemia intermedia are very different genetically determined hemoglobinopathies predisposing to pulmonary hypertension. The etiologies responsible for the associated development of pulmonary hypertension in both diseases are multi-factorial with extensive mechanistic contributors described. Both sickle cell anemia and β-thalassemia intermedia present with intra and extravascular hemolysis. And because sickle cell anemia and β-thalassemia intermedia share features of extravascular hemolysis, macrophage iron excess and anemia we sought to characterize the common features of the pulmonary hypertension phenotype, cardiac mechanics, and function as well as lung and right ventricular metabolism. Within the concept of iron, we have defined a unique pulmonary vascular iron accumulation in lungs of sickle cell anemia pulmonary hypertension patients at autopsy. This observation is unlike findings in idiopathic or other forms of pulmonary arterial hypertension. In this study, we hypothesized that a common pathophysiology would characterize the pulmonary hypertension phenotype in sickle cell anemia and β-thalassemia intermedia murine models. However, unlike sickle cell anemia, β-thalassemia is also a disease of dyserythropoiesis, with increased iron absorption and cellular iron extrusion. This process is mediated by high erythroferrone and low hepcidin levels as well as dysregulated iron transport due transferrin saturation, so there may be differences as well. Herein we describe common and divergent features of pulmonary hypertension in aged Berk-ss (sickle cell anemia) and Hbb^th/3+ (intermediate β-thalassemia) mice and suggest translational utility as proof-of-concept models to study pulmonary hypertension therapeutics specific to genetic anemias.

Pulmonary hypertension in the child with bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is the most common chronic lung disease of prematurity resulting from complex interactions of perinatal factors that often lead to prolonged respiratory support and increased pulmonary morbidity. There is also growing appreciation for the dysmorphic pulmonary bed characterized by vascular growth arrest and remodeling, resulting in pulmonary vascular disease and its most severe form, pulmonary hypertension (PH) in children with BPD. In this review, we comprehensively discuss the pathophysiology of PH in children with BPD, evaluate the current recommendations for screening and diagnosis of PH, discern associated comorbid conditions, and outline the current treatment options.

Angiostatic Peptide, Endostatin, Predicts Severity in Pediatric Congenital Heart Disease-Associated Pulmonary Hypertension

Background Endostatin, an angiogenic inhibitor, is associated with worse pulmonary arterial hypertension (PAH) outcomes in adults and poor lung growth in children. This study sought to assess whether endostatin is associated with disease severity and outcomes in pediatric PAH. Methods and Results Serum endostatin was measured in cross-sectional (N=160) and longitudinal cohorts (N=64) of pediatric subjects with PAH, healthy pediatric controls and pediatric controls with congenital heart disease (CHD) (N=54, N=15), and adults with CHD associated PAH (APAH-CHD, N=185). Outcomes, assessed by regression and Kaplan-Meier analysis, included hemodynamics, change in endostatin over time, and transplant-free survival. Endostatin secretion was evaluated in pulmonary artery endothelial and smooth muscle cells. Endostatin was higher in those with PAH compared with healthy controls and controls with CHD and was highest in those with APAH-CHD. In APAH-CHD, endostatin was associated with a shorter 6-minute walk distance and increased mean right atrial pressure. Over time, endostatin was associated with higher pulmonary artery pressure and pulmonary vascular resistance index, right ventricular dilation, and dysfunction. Endostatin decreased with improved hemodynamics over time. Endostatin was associated with worse transplant-free survival. Addition of endostatin to an NT-proBNP (N-terminal pro-B-type natriuretic peptide) based survival analysis improved risk stratification, reclassifying subjects with adverse outcomes. Endostatin was secreted primarily by pulmonary artery endothelial cells. Conclusions Endostatin is associated with disease severity, disease improvement, and worse survival in APAH-CHD. Endostatin with NT-proBNP improves risk stratification, better predicting adverse outcomes. The association of elevated endostatin with shunt lesions suggests that endostatin could be driven by both pulmonary artery flow and pressure. Endostatin could be studied as a noninvasive prognostic marker, particularly in APAH-CHD.

Evidence supporting a role for circulating macrophages in the regression of vascular remodeling following sub-chronic exposure to hemoglobin plus hypoxia

Macrophages are a heterogeneous population with both pro- and anti-inflammatory functions play an essential role in maintaining tissue homeostasis, promoting inflammation under pathological conditions, and tissue repair after injury. In pulmonary hypertension, the M1 phenotype is more pro-inflammatory compared to the M2 phenotype, which is involved in tissue repair. The role of macrophages in the initiation and progression of pulmonary hypertension is well studied. However, their role in the regression of established pulmonary hypertension is not well known. Rats chronically exposed to hemoglobin (Hb) plus hypoxia (HX) share similarities to humans with pulmonary hypertension associated with hemolytic disease, including the presence of a unique macrophage phenotype surrounding distal vessels that are associated with vascular remodeling. These lung macrophages are characterized by high iron content, HO-1, ET-1, and IL-6, and are recruited from the circulation. Depletion of macrophages in this model prevents the development of pulmonary hypertension and vascular remodeling. In this study, we specifically investigate the regression of pulmonary hypertension over a four-week duration after rats were removed from Hb + HX exposure with and without gadolinium chloride administration. Withdrawal of Hb + HX reversed systolic pressures and right ventricular function after Hb + Hx exposure in four weeks. Our data show that depleting circulating monocytes/macrophages during reversal prevents complete recovery of right ventricular systolic pressure and vascular remodeling in this rat model of pulmonary hypertension at four weeks post exposure. The data presented offer a novel insight into the role of macrophages in the processes of pulmonary hypertension regression in a rodent model of Hb + Hx-driven disease.

Pulmonary arterial hypertension in adults with congenital heart disease: markers of disease severity, management of advanced heart failure and transplantation

INTRODUCTION

Pulmonary arterial hypertension associated with congenital heart disease (PAH-CHD) is a progressive, life-limiting disease.

AREAS COVERED

In this paper, we review the classification and pathophysiology of PAH-CHD, including the mechanisms of disease progression and multisystem effects of disease. We evaluate current strategies of risk stratification and the use of biological markers of disease severity, and review principles of management of PAH-CHD. The indications, timing, and the content of advanced heart failure assessment and transplant listing are discussed, along with a review of the types of transplant and other forms of available circulatory support in this group of patients. Finally, the integral role of advance care planning and palliative care is discussed.

EXPERT OPINION/COMMENTARY

All patients with PAH-CHD should be followed up in expert centers, where they can receive appropriate risk assessment, PAH therapy, and supportive care. Referral for transplant assessment should be considered if there continue to be clinical high-risk features, persistent symptoms, or acute heart failure decompensation despite appropriate PAH specific therapy. Expert management of PAH-CHD patients, therefore, requires vigilance for these features, along with a close relationship with local advanced heart failure services and a working knowledge of listing criteria, which may disadvantage congenital heart disease patients.

At a crossroads: coronavirus disease 2019 recovery and the risk of pulmonary vascular disease

PURPOSE OF REVIEW

The coronavirus disease 2019 (COVID-19) pandemic has led to almost 3,000,000 deaths across 139 million people infected worldwide. Involvement of the pulmonary vasculature is considered a major driving force for morbidity and mortality. We set out to summarize current knowledge on the acute manifestations of pulmonary vascular disease (PVD) resulting from COVID-19 and prioritize long-term complications that may result in pulmonary hypertension (PH).

RECENT FINDINGS

Acute COVID-19 infection can result in widespread involvement of the pulmonary vasculature, myocardial injury, evidence of persistent lung disease, and venous thromboembolism. Post COVID-19 survivors frequently report ongoing symptoms and may be at risk for the spectrum of PH, including group 1 pulmonary arterial hypertension, group 2 PH due to left heart disease, group 3 PH due to lung disease and/or hypoxia, and group 4 chronic thromboembolic PH.

SUMMARY

The impact of COVID-19 on the pulmonary vasculature is central to determining disease severity. Although the long-term PVD manifestations of COVID-19 are currently uncertain, optimizing the care of risk factors for PH and monitoring for the development of PVD will be critical to reducing long-term morbidity and improving the health of survivors.

Secundum Type Atrial Septal Defect in Patients with Trisomy 21-Therapeutic Strategies, Outcome, and Survival: A Nationwide Study of the German National Registry for Congenital Heart Defects

(1) Secundum type atrial septal defect (ASD II) is usually considered a relatively benign cardiac lesion amenable to elective closure at preschool age. Patients with trisomy 21 (T21), however, are known to have a higher susceptibility for pulmonary vascular disease (PVD). Therefore, T21 children may present with clinical symptoms earlier than those without associated anomalies. In addition, early PVD may even preclude closure in selected T21 patients. (2) We performed a retrospective analysis of the German National Register for Congenital Heart Defects including T21 patients with associated isolated ASD II. We report incidence, demographics, therapeutic strategy, outcome, and survival of this cohort. (3) Of 46,628 patients included in the registry, 1549 (3.3%) had T21. Of these, 156 (49.4% female) had an isolated ASD II. Fifty-four patients (34.6%) underwent closure at 6.4 ± 9.9 years of age. Over a cumulative follow-up (FU) of 1148 patient-years, (median 7.4 years), only one patient developed Eisenmenger syndrome and five patients died. Survival of T21 patients without PVD was not statistically different to age- and gender-matched controls from the normal population (p = 0.62), whereas children with uncorrected T21/ASD II (including patients with severe PVD, in whom ASD-closure was considered contraindicated) showed a significantly higher mortality. (4) The outcome of T21-patients with ASD II and without PVD is excellent. However, PVD, either precluding ASD-closure or development of progressive PVD after ASD-closure, is associated with significant mortality in this cohort. Thus T21 patients with ASD II who fulfill general criteria for closure and without PVD should be offered defect closure analogous to patients without T21.

Mortality from Pulmonary Hypertension in the Pediatric Cardiac ICU

Rationale: Patients with pulmonary hypertension (PH) admitted to pediatric cardiac ICUs are at high risk of mortality. Objectives: To identify factors associated with mortality in cardiac critical care admissions with PH. Methods: We evaluated medical admissions with PH to Pediatric Cardiac Critical Care Consortium institutions over 5 years. PH was standardly defined in the clinical registry by diagnosis and/or receipt of intensive care-level pulmonary vasodilator therapy. Multivariable logistic regression identified independent associations with mortality. Measurements and Main Results: We analyzed 2,602 admissions; mortality was 10% versus 3.9% for all other medical admissions. Covariates most strongly associated with mortality included invasive ventilation (adjusted odds ratio, 44.8; 95% confidence interval, 6.2-323), noninvasive ventilation (19.7; 2.8-140), cardiopulmonary resuscitation (8.9; 5.6-14.1), and vasoactive infusions (4.8; 2.6-8.8). Patients receiving both invasive ventilation and vasoactive infusions on admission Days 1 and 2 had an observed mortality rate of 29.2% and 28.6%, respectively, compared with <5% for those not receiving either. Vasoactive infusions emerged as the dominant early risk factor for mortality, increasing the absolute risk of mortality on average by 6.4% when present on admission Day 2. Conclusions: Patients with PH admitted to pediatric cardiac critical care units have high mortality rates. Those receiving invasive ventilation and vasoactive infusions on Day 1 or Day 2 had an observed mortality rate that was more than fivefold greater than that of those who did not. These data highlight the illness severity of patients with PH in this setting and could help inform conversations with families regarding the prognosis.

Systemic sclerosis-associated pulmonary arterial hypertension in children

Systemic sclerosis (SSc) is a rare disease in childhood and is characterized by a combination of vasculopathy, inflammation, autoimmunity, and fibrogenesis with individually varying expression pattern. Pulmonary arterial hypertension (PAH) is a serious complication of SSc and affects approximately 10% of SSc patients. SSc-PAH is complex and difficult to diagnose, as symptoms are non-specific and may be complicated by other SSc-associated diseases such as interstitial lung disease or left heart disease. SSc-PAH patients can deteriorate rapidly, and disease progression can occur even in patients with mild PAH symptoms at diagnosis. Therefore, interdisciplinary care of SSc patients is essential, and treating physicians must be aware of the association between SSc and PAH. In order to detect PAH early, children with SSc should be regularly screened for PAH by pediatric cardiologists. If PAH is detected, a systematic diagnostic approach by trained PH specialists including careful phenotyping of PAH is required. Relevant interstitial lung disease and left heart disease should be ruled out in the differential diagnosis of SSc-PAH before starting any targeted therapy. Due to the progressive character of SSc-PAH known from adult studies, it appears appropriate to initiate targeted PAH-therapy in juvenile SSc-PAH early. Adapted from adult treatment algorithms, combination therapy regimens (addressing at least two pathophysiological pathways) are increasingly used for pediatric PAH patients, and there is growing evidence to support this approach also in SSc-PAH patients.

Pulmonary vascular involvement in COVID-19 pneumonitis: Is this the first and final insult?

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Acute Hemodynamic Effect of Acetazolamide in Patients With Pulmonary Hypertension Whilst Breathing Normoxic and Hypoxic Gas: A Randomized Cross-Over Trial

Aims: To test the acute hemodynamic effect of acetazolamide in patients with pulmonary hypertension (PH) under ambient air and hypoxia.

Methods: Patients with pulmonary arterial or chronic thromboembolic PH (PAH/CTEPH) undergoing right heart catheterization were included in this randomized, placebo-controlled, double-blinded, crossover trial. The main outcome, pulmonary vascular resistance (PVR), further hemodynamics, blood- and cerebral oxygenation were measured 1 h after intravenous administration of 500 mg acetazolamide or placebo-saline on ambient air (normoxia) and at the end of breathing hypoxic gas (F_IO₂ 0.15, hypoxia) for 15 min.

Results: 24 PH-patients, 71% men, mean ± SD age 59 ± 14 years, BMI 28 ± 5 kg/m², PVR 4.7 ± 2.1 WU participated. Mean PVR after acetazolamide vs. placebo was 5.5 ± 3.0 vs. 5.3 ± 3.0 WU; mean difference (95% CI) 0.2 (−0.2–0.6, p = 0.341). Heart rate was higher after acetazolamide (79 ± 12 vs. 77 ± 11 bpm, p = 0.026), pH was lower (7.40 ± 0.02 vs. 7.42 ± 0.03, p = 0.002) but PaCO₂ and PaO₂ remained unchanged while cerebral tissue oxygenation increased (71 ± 6 vs. 69 ± 6%, p = 0.017). In acute hypoxia, acetazolamide decreased PVR by 0.4 WU (0.0–0.9, p = 0.046) while PaO₂ and PaCO₂ were not changed. No adverse effects occurred.

Conclusions: In patients with PAH/CTEPH, i.v. acetazolamide did not change pulmonary hemodynamics compared to placebo after 1 hour in normoxia but it reduced PVR after subsequent acute exposure to hypoxia. Our findings in normoxia do not suggest a direct acute pulmonary vasodilator effect of acetazolamide. The reduction of PVR during hypoxia requires further corroboration. Whether acetazolamide improves PH when given over a prolonged period by stimulating ventilation, increasing oxygenation, and/or altering vascular inflammation and remodeling remains to be investigated.

Pulmonary Vascular Alterations on Computed Tomography Imaging and Outcomes in Heart Failure With Preserved Ejection Fraction: a Preliminary Data

BACKGROUND

Pulmonary vascular disease may play an important role in the pathophysiology of heart failure (HF) with preserved ejection fraction (HFpEF). However, no study has demonstrated noninvasive quantification of pulmonary vascular alterations in HFpEF. This study sought to determine the association between pulmonary vascular alterations quantified by chest computed tomography scan and clinical outcomes in HFpEF.

METHODS AND RESULTS

Pulmonary vascular alterations were quantified in 151 patients with HFpEF who underwent noncontrast chest computed tomography scan by measuring the percentage of total cross-sectional area (CSA) of pulmonary vessels less than 5 mm² to the total lung area (%CSA_<5). We divided the patients by the median value of %CSA_<5 (=1.45%) and examined the association between %CSA_<5 and a composite outcome of all-cause mortality or HF hospitalization. During a median follow-up of 17.3 months, there were 44 (29%) composite outcomes. Event rates were significantly higher in patients with higher %CSA_<5 than those with lower %CSA_<5 (log-rank P = .02). %CSA_<5 was associated with an increased risk of the outcome (hazard ratio per 1.0% increment, 1.46; 95% confidence interval 1.06-1.98; P = .02) in an unadjusted Cox model, and was independently and incrementally associated with the outcome over age, the presence of atrial fibrillation, E/e' ratio, and estimated pulmonary artery systolic pressure (global χ² 17.3 vs 11.5, P = .02).

CONCLUSIONS

A higher %CSA_<5 was associated with an increased risk of all-cause mortality or HF hospitalization in patients with HFpEF, with an incremental prognostic value over age, atrial fibrillation, E/e' ratio, and pulmonary artery systolic pressure.

Preventing disease progression in Eisenmenger syndrome

Introduction: Eisenmenger syndrome describes a condition in which a congenital heart defect has caused severe pulmonary vascular disease, resulting in reversed (right-left) or bidirectional shunting and chronic cyanosis.Areas covered: In this paper, the progression of congenital heart defects to Eisenmenger syndrome, including early screening, diagnosis and operability are covered. The mechanisms of disease progression in Eisenmenger syndrome and management strategies to combat this, including the role of pulmonary arterial hypertension therapies, are also discussed.Expert opinion/commentary: Patients with congenital heart disease (CHD) are at increased risk of developing pulmonary arterial hypertension with Eisenmenger syndrome being its extreme manifestation. All CHD patients should be regularly assessed for pulmonary hypertension. Once Eisenmenger syndrome develops, shunt closure should be avoided. The clinical manifestations of Eisenmenger syndrome are driven by the systemic effects of the pulmonary hypertension, congenital defect and long-standing cyanosis. Expert care is essential for avoiding pitfalls and preventing disease progression in this severe chronic condition, which is associated with significant morbidity and mortality. Pulmonary arterial hypertension therapies have been used alongside supportive care to improve the quality of life, exercise tolerance and the outcome of these patients, although the optimal timing for their introduction and escalation remains uncertain.

Impact of the new definition for pulmonary hypertension in patients with lung disease: an analysis of the United Network for Organ Sharing database

The implications of the recent change in the definition of pulmonary hypertension on epidemiology and outcomes are not known. We sought to determine the percentage of patients with the two most common lung diseases that would be reclassified regarding the presence/absence of pulmonary hypertension with the revised definition. A query of the United Network for Organ Sharing database was performed. The percentage of patients meeting the current and previous definition of pulmonary hypertension was described. Outcomes of patients stratified by the current and previous definitions were compared. There were 15,563 patients with right heart catheterization data analyzed. Pulmonary hypertension was more prevalent in both chronic obstructive pulmonary disease and idiopathic pulmonary fibrosis under the new definition at 52.4% versus 82.4%, and 47.6% versus 73.6%, respectively. “Pre-capillary” pulmonary hypertension by the new definition was lower at 28.1% for chronic obstructive pulmonary disease and 36.8% for idiopathic pulmonary fibrosis. Of the patients with pulmonary hypertension by the old definition, 23.9% of chronic obstructive pulmonary disease patients and 18.7% of idiopathic pulmonary fibrosis patients were not classified as pulmonary hypertension by the new definition. Conversely, 15.9% of chronic obstructive pulmonary disease patients and 15.1% of idiopathic pulmonary fibrosis patients who did not meet diagnostic criteria for pulmonary hypertension by the old definition did have pulmonary hypertension by the new definition. Patients in both disease categories had shorter transplant-free waitlist survival in the presence of pulmonary hypertension by both the new and old definitions. There was a trend toward the new definition of pre-capillary pulmonary hypertension better discerning outcomes compared to the old definition of pulmonary hypertension in idiopathic pulmonary fibrosis patients. Most patients with advanced lung disease who are listed for lung transplantation have pulmonary hypertension, but fewer have pre-capillary pulmonary hypertension than pulmonary hypertension by the old definition. Both the old and new definition of precapillary pulmonary hypertension appear to discern outcomes among the two groups of lung disease analyzed, with some evidence to suggest that the new definition performs slightly better in the idiopathic pulmonary fibrosis population.

Pulmonary Vascular Complications in Hereditary Hemorrhagic Telangiectasia and the Underlying Pathophysiology

In this review, we discuss the role of transforming growth factor-beta (TGF-β) in the development of pulmonary vascular disease (PVD), both pulmonary arteriovenous malformations (AVM) and pulmonary hypertension (PH), in hereditary hemorrhagic telangiectasia (HHT). HHT or Rendu-Osler-Weber disease is an autosomal dominant genetic disorder with an estimated prevalence of 1 in 5000 persons and characterized by epistaxis, telangiectasia and AVMs in more than 80% of cases, HHT is caused by a mutation in the ENG gene on chromosome 9 encoding for the protein endoglin or activin receptor-like kinase 1 (ACVRL1) gene on chromosome 12 encoding for the protein ALK-1, resulting in HHT type 1 or HHT type 2, respectively. A third disease-causing mutation has been found in the SMAD-4 gene, causing a combination of HHT and juvenile polyposis coli. All three genes play a role in the TGF-β signaling pathway that is essential in angiogenesis where it plays a pivotal role in neoangiogenesis, vessel maturation and stabilization. PH is characterized by elevated mean pulmonary arterial pressure caused by a variety of different underlying pathologies. HHT carries an additional increased risk of PH because of high cardiac output as a result of anemia and shunting through hepatic AVMs, or development of pulmonary arterial hypertension due to interference of the TGF-β pathway. HHT in combination with PH is associated with a worse prognosis due to right-sided cardiac failure. The treatment of PVD in HHT includes medical or interventional therapy.

Hemodynamic and Clinical Implications of Impaired Pulmonary Vascular Reserve in the Fontan Circulation

BACKGROUND

Pulmonary vascular disease, pulmonary endothelial dysfunction, liver fibrosis, renal disease, and exercise intolerance are common in adults with Fontan physiology. Although the pathophysiologic mechanisms linking these phenomena have been studied, certain aspects are not well understood.

OBJECTIVES

This study hypothesized that impaired pulmonary vascular reserve (VR) plays a central role linking these abnormalities, and that patients with abnormal pulmonary VR with exercise, compared with patients with normal VR, would display poorer pulmonary endothelial function, greater liver stiffness, more renal dysfunction, and poorer exercise capacity.

METHODS

Symptomatic adults with the Fontan palliation (n = 29) underwent invasive cardiopulmonary exercise testing, echocardiography, and assessment of microvascular function. Abnormal pulmonary VR was defined by the slope of increase in pulmonary pressure relative to cardiac output with exercise >3 mm Hg/l/min. Pulmonary endothelial function was assessed using reactive hyperemia index. End-organ function was assessed using magnetic resonance elastography-derived liver stiffness, glomerular filtration rate, N-terminal pro-B-type natriuretic peptide, and peak oxygen consumption (Vo₂).

RESULTS

Compared with individuals with normal VR (n = 8), those with abnormal VR (n = 21) displayed higher central and pulmonary venous pressures, and more severely impaired cardiac output and stroke volume responses to exertion, but similar pulmonary vascular resistance at rest. Patients with abnormal VR displayed more severely impaired reactive hyperemia index, increased liver stiffness, lower glomerular filtration rate, higher N-terminal pro-B-type natriuretic peptide, and lower peak Vo₂. As compared to pulmonary vascular resistance at rest, slope of increase in pulmonary pressure relative to cardiac output displayed stronger correlations with reactive hyperemia index (r = -0.63 vs. r = -0.31; Meng test p = 0.009), magnetic resonance elastography-derived liver stiffness (r = 0.47 vs. r = 0.29; Meng test p = 0.07), glomerular filtration rate (r = -0.52 vs. r = -0.24; Meng test p = 0.03), N-terminal pro-B-type natriuretic peptide (r = 0.56 vs. r = 0.17; Meng test p = 0.02), and peak Vo₂ (r = -0.63 vs. r = -0.26; Meng test p = 0.02).

CONCLUSIONS

Pulmonary vascular limitations in Fontan physiology are related to pulmonary endothelial and end-organ dysfunction, suggesting a mechanistic link between these commonly observed findings, and these abnormalities are more apparent during exercise testing, with little relationship at rest.