Pulmonary Hypertension and Anastrozole (PHANTOM): A Randomized, Double-Blind, Placebo-Controlled Trial.

RATIONALE: Inhibition of aromatase with anastrozole reduces pulmonary hypertension in experimental models. OBJECTIVES: We aimed to determine whether anastrozole improved six-minute walk distance (6MWD) at six months in pulmonary arterial hypertension (PAH). METHODS: We performed a randomized, double-blind, placebo-controlled Phase II clinical trial of anastrozole in subjects with PAH at seven centers. Eighty-four post-menopausal women and men with PAH were randomized in a 1:1 ratio to receive anastrozole 1 mg or placebo by mouth daily, stratified by sex using permuted blocks of variable sizes. All subjects and study staff were masked. The primary outcome was the change from baseline in 6MWD at six months. Using intent-to-treat analysis, we estimated the treatment effect of anastrozole using linear regression models adjusted for sex and baseline 6MWD. Assuming 10% loss to follow-up, we anticipated having 80% power to detect a difference in the change in 6MWD of 22 meters. MEASUREMENTS AND MAIN RESULTS: Forty-one subjects were randomized to placebo and 43 to anastrozole and all received the allocated treatment. Three subjects in the placebo group and two in the anastrozole group discontinued study drug. There was no significant difference in the change in 6MWD at six months (placebo-corrected treatment effect -7.9 m, 95%CI -32.7 - 16.9, p = 0.53). There was no difference in adverse events between the groups. CONCLUSIONS: Anastrozole did not show a significant effect on 6MWD compared to placebo in post-menopausal women and men with PAH. Anastrozole was safe and did not show adverse effects. Clinical trial registration available at www. CLINICALTRIALS: gov, ID: NCT03229499.

Novel Liver Injury Phenotypes and Outcomes in Clinical Trial Participants with Pulmonary Hypertension.

RATIONALE: Pulmonary arterial hypertension (PAH) and chronic thromboembolic pulmonary hypertension (CTEPH) cause right ventricular dysfunction which can impact other solid organs. However, the profiles and consequences of hepatic injury due to PAH and CTEPH have not been well-studied. OBJECTIVES: We aimed to identify underlying patterns of liver injury in a cohort of PAH and CTEPH patients enrolled in 15 randomized clinical trials conducted between 1998 and 2014. METHODS: We used unsupervised machine learning to identify liver injury clusters in 13 trials and validated the findings in two additional trials. We then determined whether these liver injury clusters were associated with clinical outcomes or treatment effect heterogeneity. MEASUREMENTS AND MAIN RESULTS: Our training dataset included 4,219 patients and our validation dataset included 1,756 patients with serum total bilirubin, alkaline phosphatase, aspartate aminotransferase, alanine aminotransferase, and albumin data. Using k-means clustering, we identified phenotypes with no liver injury, hepatocellular injury, cholestatic injury, and combined injury patterns. Patients in the cholestatic injury liver cluster had the shortest time to clinical worsening and the highest risk of mortality. The cholestatic injury group also experienced the greatest placebo-corrected treatment effect on six-minute walk distance. Randomization to the experimental arm transitioned patients to a healthier liver status. CONCLUSIONS: Liver injury was associated with adverse outcomes in patients with PAH and CTEPH. Randomization to active treatment had beneficial effects on liver health compared to placebo. The role of liver disease (often subclinical) in determining outcomes warrants prospective studies.

Pulmonary arterial hypertension treatment: an individual participant data network meta-analysis.

BACKGROUND AND AIMS: Effective therapies that target three main signalling pathways are approved to treat pulmonary arterial hypertension (PAH). However, there are few large patient-level studies that compare the effectiveness of these pathways. The aim of this analysis was to compare the effectiveness of the treatment pathways in PAH and to assess treatment heterogeneity. METHODS: A network meta-analysis was performed using individual participant data of 6811 PAH patients from 20 Phase III randomized clinical trials of therapy for PAH that were submitted to the US Food and Drug Administration. Individual drugs were grouped by the following treatment pathways: endothelin, nitric oxide, and prostacyclin pathways. RESULTS: The mean (±standard deviation) age of the sample was 49.2 (±15.4) years; 78.4% were female, 59.7% had idiopathic PAH, and 36.5% were on background PAH therapy. After covariate adjustment, targeting the endothelin + nitric oxide pathway {ß: 43.7 m [95% confidence interval (CI): 32.9, 54.4]}, nitric oxide pathway [ß: 29.4 m (95% CI: 22.6, 36.3)], endothelin pathway [ß: 25.3 m (95% CI: 19.8, 30.8)], and prostacyclin pathway [oral/inhaled ß: 19.1 m (95% CI: 14.2, 24.0), intravenous/subcutaneous ß: 24.4 m (95% CI: 15.1, 33.7)] significantly increased 6 min walk distance at 12 or 16 weeks compared with placebo. Treatments also significantly reduced the likelihood of having clinical worsening events. There was significant heterogeneity of treatment effects by age, body mass index, hypertension, diabetes, and coronary artery disease. CONCLUSIONS: Drugs targeting the three traditional treatment pathways significantly improve outcomes in PAH, with significant treatment heterogeneity in patients with some comorbidities. Randomized clinical trials are warranted to identify the most effective treatment strategies in a personalized approach.

Electrocardiographic Abnormalities and Their Association with Outcomes in Randomized Clinical Trials of Pulmonary Arterial Hypertension.

Rationale: Pulmonary arterial hypertension (PAH) is a progressive disease with manifestations including right atrial enlargement, right ventricular dysfunction, dilation, and hypertrophy. Electrocardiography (ECG) is a noninvasive, inexpensive test that is routinely performed in clinical settings. Prior studies have described separate abnormal findings in the electrocardiograms of patients with PAH. However, the role of composite ECG findings reflective of right heart disease (RHD) for risk stratification, clinical trial enrichment, and management of patients with PAH has not been explored. Objectives: To describe a pattern of RHD on ECG in patients with PAH and to investigate the association of this pattern with clinical measures of disease severity and outcomes. Methods: We harmonized individual participant data from 18 phase III randomized clinical trials of therapies for PAH (1998-2013) submitted to the U.S. Food and Drug Administration. RHD was defined as the presence of right ventricular hypertrophy, right axis deviation, right atrial enlargement, or right bundle branch block on ECG. Random effects linear regression, multilevel ordinal regression (cumulative link model), and Cox proportional hazards models were used to assess the association of RHD by ECG with 6-minute walk distance (6MWD), World Health Organization (WHO) functional class, and clinical worsening after a priori adjustment for age, sex, body mass index, and PAH etiology. Effect modification of treatment and ECG abnormalities was assessed by including an interaction term. Results: A total of 4,439 patients had baseline ECG, and 68% of patients had evidence of RHD. RHD on ECG was associated with higher pulmonary vascular resistance (P < 0.001) and higher mean pulmonary artery pressures (P < 0.001). Patients with RHD on ECG had 10 meters shorter 6MWD (P = 0.005) and worse WHO functional class (P < 0.001) at baseline. RHD on baseline ECG was associated with increased risk of clinical worsening (hazard ratio, 1.42; 95% confidence interval; 1.21, 1.67; P < 0.001). Patients with RHD had greater treatment effect in terms of 6MWD, WHO functional class, and time to clinical worsening than those without (P for interaction = 0.03, 0.001, and 0.03, respectively). Conclusions: RHD by ECG may be associated with worse outcomes and potentially greater treatment effect. Electrocardiograms could be an inexpensive, widely available noninvasive method to enrich clinical trial populations in PAH.

Novel Liver Injury Phenotypes and Outcomes in Pulmonary Arterial Hypertension.

Background: Pulmonary arterial hypertension (PAH) and chronic thromboembolic pulmonary hypertension (CTEPH) are disorders of the pulmonary vasculature that cause right ventricular dysfunction. Systemic consequences of right ventricular dysfunction include damage to other solid organs, such as the liver. However, the profiles and consequences of hepatic injury due to PAH and CTEPH have not been well-studied. Methods: We aimed to identify underlying patterns of liver injury in a cohort of PAH and CTEPH patients enrolled in 15 randomized clinical trials conducted between 1998 and 2012. We used unsupervised machine learning to identify liver injury clusters in 13 trials and validated the findings in two additional trials. We then determined whether these liver injury clusters were associated with clinical outcomes or treatment effect heterogeneity. Results: Our training dataset included 4,219 patients and our validation dataset included 1,756 patients with complete liver laboratory panels (serum total bilirubin, alkaline phosphatase, aspartate aminotransferase, alanine aminotransferase, and albumin). Using k-means clustering paired with factor analysis, we identified four unique liver phenotypes (no liver injury, hepatocellular injury, cholestatic injury, and combined injury patterns). Patients in the cholestatic injury liver cluster had the shortest time to clinical worsening and highest chance of worsening World Health Organization functional class. Randomization to the experimental arm was associated with a transition to healthier liver clusters compared to randomization to the control arm. The cholestatic injury group experienced the greatest placebo-corrected treatment benefit in terms of six-minute walk distance. Conclusions: Liver injury patterns were associated with adverse outcomes in patients with PAH and CTEPH. Randomization to active treatment of pulmonary hypertension in these clinical trials had beneficial effects on liver health compared to placebo. The independent role of liver disease (often subclinical) in determining outcomes warrants prospective studies of the clinical utility of liver phenotyping for PAH prognosis and contribution to clinical disease.

Associations between eGFR and albuminuria with right ventricular measures: the MESA-Right Ventricle study.

Background: Chronic kidney disease (CKD) is associated with an increased risk of pulmonary hypertension, which may lead to right ventricular (RV) pressure overload and RV dysfunction. However, the presence of subclinical changes in RV structure or function in early CKD and the influence of these changes on mortality are not well studied. We hypothesized that early CKD, as indicated by elevated albuminuria or mild reductions in estimated glomerular filtration rate (eGFR), is associated with greater RV dilation and RV mass. Methods: We included 4063 participants (age 45-84 years) without baseline clinical cardiovascular disease from the Multi-Ethnic Study of Atherosclerosis. The associations of baseline creatinine-cystatin C-based eGFR and albuminuria with cardiac magnetic resonance-derived RV measures (2000-02) were examined cross-sectionally with linear regression models. Cox regression models were used to examine whether RV parameters modified the associations of eGFR and albuminuria with all-cause mortality. Results: Participants with reductions in eGFR primarily within the 60-89 mL/min/1.73 m2 category had smaller RV end-diastolic and end-systolic volumes and stroke volume (all adjusted P-trends <.001) than those with eGFR ≥90 mL/min/1.73 m2, an association that was predominantly seen in participants with albuminuria below 30 mg/g creatinine. Albuminuria was more strongly associated with death among those with lower RV volumes (P-values for interaction <.03). Conclusions: Among community-dwelling adults, reductions in eGFR primarily within the normal range were associated with smaller RV volumes and the association of albuminuria with worse survival was stronger among those with smaller RV volumes. Further studies are needed to elucidate the underlying mechanistic pathways that link kidney measures and RV morphology.

Human liver single nuclear RNA sequencing implicates BMPR2, GDF15, arginine, and estrogen in portopulmonary hypertension.

Portopulmonary hypertension (PoPH) is a type of pulmonary vascular disease due to portal hypertension that exhibits high morbidity and mortality. The mechanisms driving disease are unknown, and transcriptional characteristics unique to the PoPH liver remain unexplored. Here, we apply single nuclear RNA sequencing to compare cirrhotic livers from patients with and without PoPH. We identify characteristics unique to PoPH in cells surrounding the central hepatic vein, including increased growth differentiation factor signaling, enrichment of the arginine biosynthesis pathway, and differential expression of the bone morphogenic protein type II receptor and estrogen receptor type I genes. These results provide insight into the transcriptomic characteristics of the PoPH liver and mechanisms by which PoPH cellular dysfunction might contribute to pulmonary vascular remodeling.

Poor functional status at the time of waitlist for pediatric lung transplant is associated with worse pretransplant outcomes.

BACKGROUND: Whether functional status is associated with survival to pediatric lung transplant is unknown. We hypothesized that completely dependent functional status at waitlist registration, defined using Lansky Play Performance Scale (LPPS), would be associated with worse outcomes. METHODS: Retrospective cohort study of pediatric lung transplant registrants utilizing United Network for Organ Sharing's Standard Transplant Analysis and Research files (2005-2020). Primary exposure was completely dependent functional status, defined as LPPS score of 10-40. Primary outcome was waitlist removal for death/deterioration with cause-specific hazard ratio (CSHR) regression. Subdistribution hazard regression (SHR, Fine and Gray) was used for the secondary outcome of waitlist removal due to transplant/improvement with a competing risk of death/deterioration. Confounders included: sex, age, race, diagnosis, ventilator dependence, extracorporeal membrane oxygenation, year, and listing center volume. RESULTS: A total of 964 patients were included (63.5% ≥ 12 years, 50.2% cystic fibrosis [CF]). Median waitlist days were 95; 20.1% were removed for death/deterioration and 68.2% for transplant/improvement. Completely dependent functional status was associated with removal due to death/deterioration (adjusted CSHR 5.30 [95% CI 2.86-9.80]). This association was modified by age (interaction p = 0.0102), with a larger effect for age ≥12 years, and particularly strong for CF. In the Fine and Gray model, completely dependent functional status did not affect the risk of removal due to transplant/improvement with a competing risk of death/deterioration (adjusted SHR 1.08 [95% CI 0.77-1.49]). CONCLUSIONS: Pediatric lung transplant registrants with the worst functional status had worse pretransplant outcomes, especially for adolescents and CF patients. Functional status at waitlist registration may be a modifiable risk factor to improve survival to lung transplant.

"It's that invisible illness": Patient and clinician perspectives on outcomes in pulmonary arterial hypertension treatment.

Knowledge of what outcomes are most meaningful to pulmonary arterial hypertension (PAH) stakeholders is limited. In this qualitative study, patients and clinicians endorsed personalized physical activity, symptoms, and psychosocial well-being as key outcomes to assess PAH treatment response, yet few are routinely measured in PAH clinical trials.

Heterogeneity of treatment effects by risk in pulmonary arterial hypertension.

BACKGROUND: It is currently unknown if disease severity modifies response to therapy in pulmonary arterial hypertension (PAH). We aimed to explore if disease severity, as defined by established risk-prediction algorithms, modified response to therapy in randomised clinical trials in PAH. METHODS: We performed a meta-analysis using individual participant data from 18 randomised clinical trials of therapy for PAH submitted to the United States Food and Drug Administration to determine if predicted risk of 1-year mortality at randomisation modified the treatment effect on three outcomes: change in 6-min walk distance (6MWD), clinical worsening at 12 weeks and time to clinical worsening. RESULTS: Of 6561 patients with a baseline US Registry to Evaluate Early and Long-Term PAH Disease Management (REVEAL 2.0) score, we found that individuals with higher baseline risk had higher probabilities of clinical worsening but no difference in change in 6MWD. We detected a significant interaction of REVEAL 2.0 risk and treatment assignment on change in 6MWD. For every 3-point increase in REVEAL 2.0 score, there was a 12.49 m (95% CI 5.86-19.12 m; p=0.001) greater treatment effect in change in 6MWD. We did not detect a significant risk by treatment interaction on clinical worsening with most of the risk-prediction algorithms. CONCLUSIONS: We found that predicted risk of 1-year mortality in PAH modified treatment effect as measured by 6MWD, but not clinical worsening. Our findings highlight the importance of identifying sources of treatment heterogeneity by predicted risk to tailor studies to patients most likely to have the greatest treatment response.

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.

Cardiac index and hepatopulmonary syndrome in liver transplantation candidates: The pulmonary vascular complications of liver disease study.

BACKGROUND AND AIMS: Hepatopulmonary syndrome (HPS) and a hyperdynamic circulation are common complications of advanced liver disease, but the relationship between HPS and cardiac index (CI) is poorly understood. We sought to compare CI in patients with and without HPS and to assess the relationship between CI and symptoms, quality of life, gas exchange, and exercise capacity among liver transplantation (LT) candidates. We performed a cross-sectional analysis within the Pulmonary Vascular Complications of Liver Disease 2 study, a multicenter prospective cohort study of patients being evaluated for LT. We excluded patients with obstructive or restrictive lung disease, intracardiac shunting, and portopulmonary hypertension. We included 214 patients (81 with HPS and 133 controls without HPS). Compared with controls, patients with HPS had a higher CI (least square mean 3.2 L/min/m 2 , 95% CI 3.1-3.4 vs. 2.8 L/min/m 2 , 95% CI 2.7-3.0, p < 0.001) after adjustment for age, sex, Model for End-stage Liver Disease-Sodium (MELD-Na) score and beta-blocker use, and a lower systemic vascular resistance. Among all LT candidates, CI was correlated with oxygenation (Alveolar-arterial oxygen gradient r =0.27, p < 0.001), intrapulmonary vasodilatation severity ( p < 0.001), and biomarkers of angiogenesis. Higher CI was independently associated with dyspnea and worse functional class and physical quality of life after adjusting for age, sex, MELD-Na, beta-blocker use, and HPS status. HPS was associated with a higher CI among LT candidates. Independent of HPS, higher CI was associated with increased dyspnea and worse functional class, quality of life, and arterial oxygenation.

Distinct community structures of the fungal microbiome and respiratory health in adults with cystic fibrosis.

BACKGROUND: The respiratory tract fungal microbiome in cystic fibrosis (CF) has been understudied despite increasing recognition of fungal pathogens in CF lung disease. We sought to better understand the fungal communities in adults with CF, and to define relationships between fungal profiles and clinical characteristics. METHODS: We enrolled 66 adults with CF and collected expectorated sputum, spirometry, Cystic Fibrosis Questionnaire-revised, and clinical data. Fungi were molecularly profiled by sequencing of the internal transcribed spacer (ITS) region. Total fungal abundance was measured by quantitative PCR. Relative abundance and qPCR-corrected abundances were determined. Selective fungus culture identified cultivable fungi. Alpha diversity and beta diversity were measured and relationships with clinical parameters were interrogated. RESULTS: Median age was 29 years and median FEV1 percent predicted 58%. Members of the Candida genus were the most frequent dominant taxa in CF sputum. Apiotrichum, Trichosporon, Saccharomyces cerevisiae, and Scedosporium were present in high relative abundance in few samples; whereas, Aspergillus species were detected at low levels. Higher FEV1% predicted and CFTR modulator use were associated with greater alpha-diversity. Chronic azithromycin use was associated with lower alpha-diversity. Patients with acute pulmonary had distinct fungal community composition compared to clinically stable subjects. Differing yeast species were mainly responsible for the community differences. CONCLUSION: The respiratory tract fungal microbiome in adults with CF is associated with lung function, pulmonary exacerbation status, macrolide use, and CFTR modulator use. Future work to better understand fungal diversity in the CF airway and its impact on lung health is necessary.

Obstructive Sleep Apnea and Longitudinal Changes in Interstitial Lung Imaging and Lung Function: The MESA Study.

Rationale: Obstructive sleep apnea (OSA) has been hypothesized to be a risk factor in interstitial lung disease (ILD) and is associated with radiological markers that may represent the earlier stages of ILD. Prior studies have been limited by their cross-sectional design and potential confounding by body habitus. Objectives: To test the hypothesis that OSA severity is associated with more high-attenuation areas (HAAs) on computed tomography and worse lung function over time among older community-dwelling adults. Methods: We used data from participants in the MESA (Multi-Ethnic Study of Atherosclerosis) who had apnea-hypopnea index (AHI) measured from polysomnography (2010-2013), high attenuation areas (HAAs, -600 to -250 Hounsfield units, n = 784), assessments from exams 5 (2010-2012) and 6 (2016-2018) full-lung computed tomography scans, and spirometry assessments (n = 677). Linear mixed-effects models with random intercept were used to examine associations of OSA severity (i.e., AHI and hypoxic burden) with changes in HAAs, total lung volumes, and forced vital capacity (FVC) between exams 5 and 6. Potential confounders were adjusted for in the model, including age, sex, smoking history, height, and weight. Results: Among those with a higher AHI there were more men and a higher body mass index. Participants with AHI ⩾ 15 events/h and in the highest hypoxic burden quartile each had increases in HAAs of 11.30% (95% confidence interval [CI], 3.74-19.35%) and 9.85% (95% CI, 1.40-19.01%) per 10 years, respectively. There was a more rapid decline in total lung volumes imaged and FVC among those with AHI ⩾ 15 events/h of 220.2 ml (95% CI, 47.8-392.5 ml) and 3.63% (95% CI, 0.43-6.83%) per 10 years, respectively. Conclusions: A greater burden of hypoxia related to obstructive events during sleep was associated with increased lung densities over time and a more rapid decline in lung volumes regardless of body habitus. Our findings suggest OSA may be a contributing factor in the early stages of ILD.

The Clinical Association between Aspergillus fumigatus and Respiratory Outcomes in Adolescents and Adults with Cystic Fibrosis.

Rationale: The clinical significance of Aspergillus fumigatus (Af) detection in the absence of allergic bronchopulmonary aspergillosis in cystic fibrosis (CF) airways remains unclear. Yet, some clinicians initiate antifungal therapy for Af-positive respiratory cultures out of concern for infection in people with CF. Objectives: To determine the association between the presence of Af and respiratory outcomes in individuals with CF. Methods: We conducted a prospective longitudinal cohort study of 206 adults and adolescents (age 14 yr and older) with CF and collected sputum for selective fungus culture. We assessed clinical outcome measurements, including patient-reported outcomes (measured by the Cystic Fibrosis Questionnaire-Revised), spirometry, and number of pulmonary exacerbations (PEx) for a 1-year period. We used mixed-effects linear models to determine the association between positive Af culture results, defined as Af detection in sputum culture at the study visit, with both respiratory domain score and forced expiratory volume in 1 second (FEV1) percent predicted, adjusted for confounders. Mixed-effects Poisson regression models were employed to examine the association between positive Af culture results and PEx events. We explored the association between Af history, defined as Af detection at baseline or within 2 years of enrollment, and respiratory outcomes. Results: Af prevalence was 10.3% (95% confidence interval [CI], 6.8, 15.7) at baseline. Forty-eight (23.3%; 95% CI, 17.7, 29.7) participants had at least one Af-positive culture result during the study period. Positive Af culture result was not associated with lower respiratory domain score. However, Af history was associated with a 6.48-point lower respiratory domain score, reflective of worse respiratory quality of life (95% CI, -11.96, -0.99; P = 0.02). Positive Af culture result was associated with a 2.54% lower FEV1 percent predicted (95% CI, -4.64, -0.44; P = 0.02) and a 1.71-fold increase in severe PEx incidence (95% CI, 1.05, 2.76; P = 0.03). Conclusions: Positive Af culture result was not associated with lower patient-reported, respiratory-related quality of life. Yet, positive Af culture result was associated with both lower FEV1 percent predicted and increased frequency of severe PEx warranting intravenous antibiotics in adolescents and adults with CF. Future studies are required to better understand the direct role of Af in lung disease progression in CF.

Primary graft dysfunction grade 3 following pediatric lung transplantation is associated with chronic lung allograft dysfunction.

BACKGROUND: Severe primary graft dysfunction (PGD) is associated with the development of bronchiolitis obliterans syndrome (BOS), the most common form of chronic lung allograft dysfunction (CLAD), in adults. However, PGD associations with long-term outcomes following pediatric lung transplantation are unknown. We hypothesized that PGD grade 3 (PGD 3) at 48- or 72-hours would be associated with shorter CLAD-free survival following pediatric lung transplantation. METHODS: This was a single center retrospective cohort study of patients ≤ 21 years of age who underwent bilateral lung transplantation between 2005 and 2019 with ≥ 1 year of follow-up. PGD and CLAD were defined by published criteria. We evaluated the association of PGD 3 at 48- or 72-hours with CLAD-free survival by using time-to-event analyses. RESULTS: Fifty-one patients were included (median age 12.7 years; 51% female). The most common transplant indications were cystic fibrosis (29%) and pulmonary hypertension (20%). Seventeen patients (33%) had PGD 3 at either 48- or 72-hours. In unadjusted analysis, PGD 3 was associated with an increased risk of CLAD or mortality (HR 2.10, 95% CI 1.01-4.37, p=0.047). This association remained when adjusting individually for multiple potential confounders. There was evidence of effect modification by sex (interaction p = 0.055) with the association of PGD 3 and shorter CLAD-free survival driven predominantly by males (HR 4.73, 95% CI 1.44-15.6) rather than females (HR 1.23, 95% CI 0.47-3.20). CONCLUSIONS: PGD 3 at 48- or 72-hours following pediatric lung transplantation was associated with shorter CLAD-free survival. Sex may be a modifier of this association.

Minimal Clinically Important Difference in the 6-minute-walk Distance for Patients with Pulmonary Arterial Hypertension.

Rationale: The 6-minute-walk distance (6MWD) is an important clinical and research metric in pulmonary arterial hypertension (PAH); however, there is no consensus about what minimal change in 6MWD is clinically significant. Objectives: We aimed to determine the minimal clinically important difference in the 6MWD. Methods: We performed a meta-analysis using individual participant data from eight randomized clinical trials of therapy for PAH submitted to the U.S. Food and Drug Administration to derive minimal clinically important differences in the 6MWD. The estimates were externally validated using the Pulmonary Hypertension Association Registry. We anchored the change in 6MWD to the change in the Medical Outcomes Survey Short Form physical component score. Measurements and Main Results: The derivation (clinical trial) and validation (Pulmonary Hypertension Association Registry) samples were comprised of 2,404 and 537 adult patients with PAH, respectively. The mean ± standard deviation age of the derivation sample was 50.5 ± 15.2 years, and 1,849 (77%) were female, similar to the validation sample. The minimal clinically important difference in the derivation sample was 33 meters (95% confidence interval, 27-38), which was almost identical to that in the validation sample (36 m [95% confidence interval, 29-43]). The minimal clinically important difference did not differ by age, sex, race, pulmonary hypertension etiology, body mass index, use of background therapy, or World Health Organization functional class. Conclusions: We estimated a 6MWD minimal clinically important difference of approximately 33 meters for adults with PAH. Our findings can be applied to the design of clinical trials of therapies for PAH.