SPECTRA Phase 2b Study: Impact of Sotatercept on Exercise Tolerance and Right Ventricular Function in Pulmonary Arterial Hypertension.

BACKGROUND: This study aims to assess the impact of sotatercept on exercise tolerance, exercise capacity, and right ventricular function in pulmonary arterial hypertension. METHODS: SPECTRA (Sotatercept Phase 2 Exploratory Clinical Trial in PAH) was a phase 2a, single-arm, open-label, multicenter exploratory study that evaluated the effects of sotatercept by invasive cardiopulmonary exercise testing in participants with pulmonary arterial hypertension and World Health Organization functional class III on combination background therapy. The primary end point was the change in peak oxygen uptake from baseline to week 24. Cardiac magnetic resonance imaging was performed to assess right ventricular function. RESULTS: Among the 21 participants completing 24 weeks of treatment, there was a significant improvement from baseline in peak oxygen uptake, with a mean change of 102.74 mL/min ([95% CIs, 27.72-177.76]; P=0.0097). Sotatercept demonstrated improvements in secondary end points, including resting and peak exercise hemodynamics, and 6-minute walk distance versus baseline measures. Cardiac magnetic resonance imaging showed improvements from baseline at week 24 in right ventricular function. CONCLUSIONS: The clinical efficacy and safety of sotatercept demonstrated in the SPECTRA study emphasize the potential of this therapy as a new treatment option for patients with pulmonary arterial hypertension. Improvements in right ventricular structure and function underscore the potential for sotatercept as a disease-modifying agent with reverse-remodeling capabilities. REGISTRATION: URL: https://www.clinicaltrials.gov; Unique identifier: NCT03738150.

Inhaled treprostinil in patients with pulmonary hypertension associated with interstitial lung disease with less severe haemodynamics: a post hoc analysis of the INCREASE study.

BACKGROUND: Inhaled treprostinil (iTre) is the only treatment approved for pulmonary hypertension due to interstitial lung disease (PH-ILD) to improve exercise capacity. This post hoc analysis evaluated clinical worsening and PH-ILD exacerbations from the 16-week INCREASE study and change in 6-minute walking distance (6MWD) in the INCREASE open-label extension (OLE) in patients with less severe haemodynamics. METHODS: Patients were stratified by baseline pulmonary vascular resistance (PVR) of <4 Wood units (WU) versus ≥4 WU and <5 WU versus ≥5 WU. Exacerbations of underlying lung disease, clinical worsening and change in N-terminal prohormone of brain natriuretic peptide (NT-proBNP) in INCREASE were evaluated. For the OLE, patients previously assigned to placebo were considered to have a 16-week treatment delay. 6MWD and clinical events in the OLE were evaluated by PVR subgroup. RESULTS: Of the 326 patients enrolled in INCREASE, patients with less severe haemodynamics receiving iTre had fewer exacerbations of underlying lung disease and clinical worsening events. This was supported by the Bayesian analysis of the risk of disease progression (HR<1), and significant decreases in NT-proBNP levels. In the OLE, patients without a treatment delay had improved exercise capacity after 1-year compared with those with a 16-week treatment delay (22.1 m vs -10.3 m). Patients with a PVR of ≤5 WU without a treatment delay had a change of 5.5 m compared with -8.2 m for those with a treatment delay. Patients without a treatment delay had a prolonged time to hospitalisation, lung disease exacerbation and death. CONCLUSION: Treatment with iTre led to consistent benefits in clinical outcomes in patients with PH-ILD and less severe haemodynamics. Earlier treatment in less severe PH-ILD may lead to better exercise capacity long-term, however, the subgroup analyses in this post hoc study were underpowered and confirmation of these findings is needed.

Implications of Mean Pulmonary Arterial Wedge Pressure Trajectories in Pulmonary Arterial Hypertension.

Rationale: The mean pulmonary arterial wedge pressure (mPAWP) is the critical hemodynamic factor differentiating group 1 pulmonary arterial hypertension (PAH) from group 2 pulmonary hypertension associated with left heart disease. Despite the discrepancy between the mPAWP upper physiologic normal and current PAH definitions, the implications of the initial mPAWP for PAH clinical trajectory are poorly understood. Objectives: To model longitudinal mPAWP trajectories in PAH over 10 years and examine the clinical and hemodynamic factors associated with trajectory membership. Methods: Adult patients with PAH with two or more right heart catheterizations were identified from a multiinstitution healthcare system in eastern Massachusetts. mPAWP trajectories were constructed via group-based trajectory modeling. Feature selection was performed in least absolute shrinkage and selection operator regression. Logistic regression was used to assess associations between trajectory membership, baseline characteristics, and transplant-free survival. Measurements and Main Results: Among 301 patients with PAH, there were two distinct mPAWP trajectories, termed "mPAWP-high" (n = 71; 23.6%) and "mPAWP-low" (n = 230; 76.4%), based on the ultimate mPAWP value. Initial mPAWP clustered around median 12 mm Hg (interquartile range [IQR], 8-14 mm Hg) in the mPAWP-high and 9 mm Hg (IQR, 6-11 mm Hg) in the mPAWP-low trajectories (P < 0.001). After feature selection, initial mPAWP ⩾12 mm Hg predicted an mPAWP-high trajectory (odds ratio, 3.2; 95% confidence interval, 1.4-6.1; P = 0.0006). An mPAWP-high trajectory was associated with shorter transplant-free survival (vs. mPAWP-low, median, 7.8 vs. 11.3 yr; log-rank P = 0.017; age-adjusted P = 0.217). Conclusions: Over 10 years, the mPAWP followed two distinct trajectories, with 25% evolving into group 2 pulmonary hypertension physiology. Using routine baseline data, longitudinal mPAWP trajectory could be predicted accurately, with initial mPAWP ⩾12 mm Hg as one of the strongest predictors.

Survival analysis from the INCREASE study in PH-ILD: evaluating the impact of treatment crossover on overall mortality.

OBJECTIVE: A post-hoc analysis of the INCREASE trial and its open-label extension (OLE) was performed to evaluate whether inhaled treprostinil has a long-term survival benefit in patients with pulmonary hypertension associated with interstitial lung disease (PH-ILD). METHODS: Two different models of survival were employed; the inverse probability of censoring weighting (IPCW) and the rank-preserving structural failure time (RPSFT) models both allow construction of a pseudo-placebo group, thereby allowing for long-term survival evaluation of patients with PH-ILD receiving inhaled treprostinil. Time-varying stabilised weights were calculated by fitting Cox proportional hazards models based on the baseline and time-varying prognostic factors to generate weighted Cox regression models with associated adjusted HRs. RESULTS: In the INCREASE trial, there were 10 and 12 deaths in the inhaled treprostinil and placebo arms, respectively, during the 16-week randomised trial. During the OLE, all patients received inhaled treprostinil and there were 29 and 33 deaths in the prior inhaled treprostinil arm and prior placebo arm, respectively. With a conventional analysis, the HR for death was 0.71 (95% CI 0.46 to 1.10; p=0.1227). Both models demonstrated significant reductions in death associated with inhaled treprostinil treatment with HRs of 0.62 (95% CI 0.39 to 0.99; p=0.0483) and 0.26 (95% CI 0.07 to 0.98; p=0.0473) for the IPCW and RPSFT methods, respectively. CONCLUSION: Two independent modelling techniques that have been employed in the oncology literature both suggest a long-term survival benefit associated with inhaled treprostinil treatment in patients with PH-ILD.

Effects of sotatercept on haemodynamics and right heart function: analysis of the STELLAR trial.

BACKGROUND: In the phase 3 STELLAR trial, sotatercept, an investigational first-in-class activin signalling inhibitor, demonstrated beneficial effects on 6-min walk distance and additional efficacy endpoints in pre-treated participants with pulmonary arterial hypertension (PAH). METHODS: This post hoc analysis evaluated data from right heart catheterisation (RHC) and echocardiography (ECHO) obtained from the STELLAR trial. Changes from baseline in RHC and ECHO parameters were assessed at 24 weeks. An analysis of covariance (ANCOVA) model was used to estimate differences in least squares means with treatment and randomisation stratification (mono/double versus triple therapy; World Health Organization functional class II versus III) as fixed factors, and baseline value as covariate. RESULTS: Relative to placebo, treatment with sotatercept led to significant (all p<0.0001 except where noted) improvements from baseline in mean pulmonary artery (PA) pressure (-13.9 mmHg), pulmonary vascular resistance (-254.8 dyn·s·cm-5), mean right atrial pressure (-2.7 mmHg), mixed venous oxygen saturation (3.84%), PA elastance (-0.42 mmHg·mL-1·beat-1), PA compliance (0.58 mL·mmHg-1), cardiac efficiency (0.48 mL·beat-1·mmHg-1), right ventricular (RV) work (-0.85 g·m) and RV power (-32.70 mmHg·L·min-1). ECHO showed improvements in tricuspid annular plane systolic excursion (TAPSE) to systolic pulmonary artery pressure ratio (0.12 mm·mmHg-1), end-systolic and end-diastolic RV areas (-4.39 cm2 and -5.31 cm2, respectively), tricuspid regurgitation and RV fractional area change (2.04% p<0.050). No significant between-group changes from baseline were seen for TAPSE, heart rate, cardiac output, stroke volume or their indices. CONCLUSION: In pre-treated patients with PAH, sotatercept demonstrated substantial improvements in PA pressures, PA compliance, PA-RV coupling and right heart function.

Effects of ranolazine on right ventricular function, fluid dynamics, and metabolism in patients with precapillary pulmonary hypertension: insights from a longitudinal, randomized, double-blinded, placebo controlled, multicenter study.

Introduction: Right ventricular (RV) function is a major determinant of outcome in patients with precapillary pulmonary hypertension (PH). We studied the effect of ranolazine on RV function over 6 months using multi-modality imaging and biochemical markers in patients with precapillary PH (groups I, III, and IV) and RV dysfunction [CMR imaging ejection fraction (EF) < 45%] in a longitudinal, randomized, double-blinded, placebo-controlled, multicenter study of ranolazine treatment. Methods: Enrolled patients were assessed using cardiac magnetic resonance (CMR) imaging, 11C-acetate and 18-F-FDG positron emission tomography (PET), and plasma metabolomic profiling, at baseline and at the end of treatment. Results: Twenty-two patients were enrolled, and 15 patients completed all follow-up studies with 9 in the ranolazine arm and 6 in the placebo arm. RVEF and RV/Left ventricle (LV) mean glucose uptake were significantly improved after 6 months of treatment in the ranolazine arm. Metabolomic changes in aromatic amino acid metabolism, redox homeostasis, and bile acid metabolism were observed after ranolazine treatment, and several changes significantly correlated with changes in PET and CMR-derived fluid dynamic measurements. Discussion: Ranolazine may improve RV function by altering RV metabolism in patients with precapillary PH. Larger studies are needed to confirm the beneficial effects of ranolazine.

Exercise Pathophysiology in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome and Postacute Sequelae of SARS-CoV-2: More in Common Than Not?

TOPIC IMPORTANCE: Postacute sequelae of SARS-CoV-2 (PASC) is a long-term consequence of acute infection from COVID-19. Clinical overlap between PASC and myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) has been observed, with shared symptoms including intractable fatigue, postexertional malaise, and orthostatic intolerance. The mechanistic underpinnings of such symptoms are poorly understood. REVIEW FINDINGS: Early studies suggest deconditioning as the primary explanation for exertional intolerance in PASC. Cardiopulmonary exercise testing reveals perturbations related to systemic blood flow and ventilatory control associated with acute exercise intolerance in PASC, which are not typical of simple detraining. Hemodynamic and gas exchange derangements in PASC have substantial overlap with those observed with ME/CFS, suggestive of shared mechanisms. SUMMARY: This review illustrates exercise pathophysiologic commonalities between PASC and ME/CFS that will help guide future diagnostics and treatment.

Phase 3 Trial of Sotatercept for Treatment of Pulmonary Arterial Hypertension.

BACKGROUND: Pulmonary arterial hypertension is a progressive disease involving proliferative remodeling of the pulmonary vessels. Despite therapeutic advances, the disease-associated morbidity and mortality remain high. Sotatercept is a fusion protein that traps activins and growth differentiation factors involved in pulmonary arterial hypertension. METHODS: We conducted a multicenter, double-blind, phase 3 trial in which adults with pulmonary arterial hypertension (World Health Organization [WHO] functional class II or III) who were receiving stable background therapy were randomly assigned in a 1:1 ratio to receive subcutaneous sotatercept (starting dose, 0.3 mg per kilogram of body weight; target dose, 0.7 mg per kilogram) or placebo every 3 weeks. The primary end point was the change from baseline at week 24 in the 6-minute walk distance. Nine secondary end points, tested hierarchically in the following order, were multicomponent improvement, change in pulmonary vascular resistance, change in N-terminal pro-B-type natriuretic peptide level, improvement in WHO functional class, time to death or clinical worsening, French risk score, and changes in the Pulmonary Arterial Hypertension-Symptoms and Impact (PAH-SYMPACT) Physical Impacts, Cardiopulmonary Symptoms, and Cognitive/Emotional Impacts domain scores; all were assessed at week 24 except time to death or clinical worsening, which was assessed when the last patient completed the week 24 visit. RESULTS: A total of 163 patients were assigned to receive sotatercept and 160 to receive placebo. The median change from baseline at week 24 in the 6-minute walk distance was 34.4 m (95% confidence interval [CI], 33.0 to 35.5) in the sotatercept group and 1.0 m (95% CI, -0.3 to 3.5) in the placebo group. The Hodges-Lehmann estimate of the difference between the sotatercept and placebo groups in the change from baseline at week 24 in the 6-minute walk distance was 40.8 m (95% CI, 27.5 to 54.1; P<0.001). The first eight secondary end points were significantly improved with sotatercept as compared with placebo, whereas the PAH-SYMPACT Cognitive/Emotional Impacts domain score was not. Adverse events that occurred more frequently with sotatercept than with placebo included epistaxis, dizziness, telangiectasia, increased hemoglobin levels, thrombocytopenia, and increased blood pressure. CONCLUSIONS: In patients with pulmonary arterial hypertension who were receiving stable background therapy, sotatercept resulted in a greater improvement in exercise capacity (as assessed by the 6-minute walk test) than placebo. (Funded by Acceleron Pharma, a subsidiary of MSD; STELLAR ClinicalTrials.gov number, NCT04576988.).

Sotatercept for the treatment of pulmonary arterial hypertension: PULSAR open-label extension.

BACKGROUND: In participants with pulmonary arterial hypertension, 24 weeks of sotatercept resulted in a significantly greater reduction from baseline in pulmonary vascular resistance than placebo. This report characterises the longer-term safety and efficacy of sotatercept in the PULSAR open-label extension. We report cumulative safety, and efficacy at months 18-24, for all participants treated with sotatercept. METHODS: PULSAR was a phase 2, randomised, double-blind, placebo-controlled study followed by an open-label extension, which evaluated sotatercept on top of background pulmonary arterial hypertension therapy in adults. Participants originally randomised to placebo were re-randomised 1:1 to sotatercept 0.3 or 0.7 mg·kg-1 (placebo-crossed group); those initially randomised to sotatercept continued the same sotatercept dose (continued-sotatercept group). Safety was evaluated in all participants who received ≥1 dose of sotatercept. The primary efficacy endpoint was change from baseline to months 18-24 in pulmonary vascular resistance. Secondary endpoints included 6-min walk distance and functional class. Two prespecified analyses, placebo-crossed and delayed-start, evaluated efficacy irrespective of dose. RESULTS: Of 106 participants enrolled in the PULSAR study, 97 continued into the extension period. Serious treatment-emergent adverse events were reported in 32 (30.8%) participants; 10 (9.6%) reported treatment-emergent adverse events leading to study discontinuation. Three (2.9%) participants died, none considered related to study drug. The placebo-crossed group demonstrated significant improvement across primary and secondary endpoints and clinical efficacy was maintained in the continued-sotatercept group. CONCLUSION: These results support the longer-term safety and durability of clinical benefit of sotatercept for pulmonary arterial hypertension.

Inhaled Treprostinil Dosage in Pulmonary Hypertension Associated With Interstitial Lung Disease and Its Effects on Clinical Outcomes.

BACKGROUND: Pulmonary hypertension (PH) complicates the course of many patients with fibrotic interstitial lung disease (ILD). Inhaled treprostinil (iTre) has been shown to improve functional ability and to delay clinical worsening in patients with PH resulting from ILD. RESEARCH QUESTION: Do higher dosages of iTre have greater benefits in preventing clinical worsening and achieving clinical improvement? STUDY DESIGN AND METHODS: Post hoc analysis of the INCREASE study, a 16-week double-blind, randomized, placebo-controlled trial of iTre in patients with PH resulting from ILD. Four groups were identified based on the number of breaths per session (bps; < 9 and ≥ 9 bps) of active drug or placebo attained at 4 weeks. Patients were evaluated for clinical worsening (15% decrease in 6-min walkdistance, cardiopulmonary hospitalization, lung transplantation, or death) or clinical improvement (15% increase in the six-minute walk distance with a concomitant 30% reduction in N-terminal prohormone of brain natriuretic peptide without any clinical worsening event). RESULTS: At 4 weeks, 70 patients were at a dose of ≥ 9 bps (high-dosage group) and 79 patients were at a dose of < 9 bps (low-dosage group) in the iTre arm vs 86 patients in the high-dose group and 67 patients in the low-dose group in the placebo arm. Between weeks 4 and 16, 17.1% of patients in the high-dose treprostinil group and 22.8% in the low-dose treatment group experienced a clinical worsening event vs 33.7% and 34.3% of patients in the two placebo arms, respectively (P = .006). By week 16, 15.7% and 12.7% of patients in the high- and low-dose iTre groups, respectively, demonstrated clinical improvement vs 7% and 1.5% patients in the placebo arms (P = .003) INTERPRETATION: Higher dosages of iTre overall show greater benefit in terms of preventing clinical worsening and achieving clinical improvement. These data support the early initiation and uptitration of therapy to a dosage of at least 9 bps four times daily in patients with PH resulting from ILD. TRIAL REGISTRY: ClinicalTrials.gov; No.: NCT02630316; URL: www. CLINICALTRIALS: gov.

Perfusion imaging heterogeneity during NO inhalation distinguishes pulmonary arterial hypertension (PAH) from healthy subjects and has potential as an imaging biomarker.

BACKGROUND: Without aggressive treatment, pulmonary arterial hypertension (PAH) has a 5-year mortality of approximately 40%. A patient's response to vasodilators at diagnosis impacts the therapeutic options and prognosis. We hypothesized that analyzing perfusion images acquired before and during vasodilation could identify characteristic differences between PAH and control subjects. METHODS: We studied 5 controls and 4 subjects with PAH using HRCT and 13NN PET imaging of pulmonary perfusion and ventilation. The total spatial heterogeneity of perfusion (CV2Qtotal) and its components in the vertical (CV2Qvgrad) and cranio-caudal (CV2Qzgrad) directions, and the residual heterogeneity (CV2Qr), were assessed at baseline and while breathing oxygen and nitric oxide (O2 + iNO). The length scale spectrum of CV2Qr was determined from 10 to 110 mm, and the response of regional perfusion to O2 + iNO was calculated as the mean of absolute differences. Vertical gradients in perfusion (Qvgrad) were derived from perfusion images, and ventilation-perfusion distributions from images of 13NN washout kinetics. RESULTS: O2 + iNO significantly enhanced perfusion distribution differences between PAH and controls, allowing differentiation of PAH subjects from controls. During O2 + iNO, CV2Qvgrad was significantly higher in controls than in PAH (0.08 (0.055-0.10) vs. 6.7 × 10-3 (2 × 10-4-0.02), p < 0.001) with a considerable gap between groups. Qvgrad and CV2Qtotal showed smaller differences: - 7.3 vs. - 2.5, p = 0.002, and 0.12 vs. 0.06, p = 0.01. CV2Qvgrad had the largest effect size among the primary parameters during O2 + iNO. CV2Qr, and its length scale spectrum were similar in PAH and controls. Ventilation-perfusion distributions showed a trend towards a difference between PAH and controls at baseline, but it was not statistically significant. CONCLUSIONS: Perfusion imaging during O2 + iNO showed a significant difference in the heterogeneity associated with the vertical gradient in perfusion, distinguishing in this small cohort study PAH subjects from controls.

Trends in management and outcomes of pulmonary embolism with a multidisciplinary response team.

Multidisciplinary pulmonary embolism (PE) response teams have garnered widespread adoption given the complexities of managing acute PE and provide a platform for assessment of trends in therapy and outcomes. We describe temporal trends in PE management and outcomes following the deployment of such a team. All consecutive patients managed by our multidisciplinary PE response team activated by the Emergency Department were included over a 5-year calendar period. We examined temporal trends in management and rates of a composite primary endpoint (all-cause-death, major bleeding, recurrent venous thromboembolism, and readmission) at 30 days and 6 months. We assessed 425 patients between 2015 and 2019. We observed an increase in PE acuity and use of systemic thrombolysis. The primary endpoint at 30 days decreased from 16.3% in 2015 to 7.1% in 2019 (adjusted rate ratio per period, 0.63; 95%CI, 0.47-0.84), driven by a decrease in the adjusted rate of major bleeding. Among 406 patients with complete follow-up, the adjusted rate ratio per year for the primary outcome at 6 months was 0.37 (95%CI, 0.19-0.71), driven by a decrease in all-cause mortality. We observed evidence of temporal changes in clinical presentation, therapeutic strategies, and outcomes for acute PE, in parallel to, but not necessarily because of, the implementation of a multidisciplinary response team. Over time, major bleeding, mortality and readmission rates decreased, despite an increase in PE risk category.

Clinical Characteristics and Transplant-Free Survival Across the Spectrum of Pulmonary Vascular Disease.

BACKGROUND: PVDOMICS (Pulmonary Vascular Disease Phenomics) is a precision medicine initiative to characterize pulmonary vascular disease (PVD) using deep phenotyping. PVDOMICS tests the hypothesis that integration of clinical metrics with omic measures will enhance understanding of PVD and facilitate an updated PVD classification. OBJECTIVES: The purpose of this study was to describe clinical characteristics and transplant-free survival in the PVDOMICS cohort. METHODS: Subjects with World Symposium Pulmonary Hypertension (WSPH) group 1-5 PH, disease comparators with similar underlying diseases and mild or no PH and healthy control subjects enrolled in a cross-sectional study. PH groups, comparators were compared using standard statistical tests including log-rank tests for comparing time to transplant or death. RESULTS: A total of 1,193 subjects were included. Multiple WSPH groups were identified in 38.9% of PH subjects. Nocturnal desaturation was more frequently observed in groups 1, 3, and 4 PH vs comparators. A total of 50.2% of group 1 PH subjects had ground glass opacities on chest computed tomography. Diffusing capacity for carbon monoxide was significantly lower in groups 1-3 PH than their respective comparators. Right atrial volume index was higher in WSPH groups 1-4 than comparators. A total of 110 participants had a mean pulmonary artery pressure of 21-24 mm Hg. Transplant-free survival was poorest in group 3 PH. CONCLUSIONS: PVDOMICS enrolled subjects across the spectrum of PVD, including mild and mixed etiology PH. Novel findings include low diffusing capacity for carbon monoxide and enlarged right atrial volume index as shared features of groups 1-3 and 1-4 PH, respectively; unexpected, frequent presence of ground glass opacities on computed tomography; and sleep alterations in group 1 PH, and poorest survival in group 3 PH. PVDOMICS will facilitate a new understanding of PVD and refine the current PVD classification. (Pulmonary Vascular Disease Phenomics Program PVDOMICS [PVDOMICS]; NCT02980887).

Recent advances in the management of pulmonary hypertension with interstitial lung disease.

Pulmonary hypertension (PH) is known to complicate various forms of interstitial lung disease (ILD), including idiopathic pulmonary fibrosis, the interstitial pneumonias and chronic hypersensitivity pneumonitis. Pathogenesis of PH-ILD remains incompletely understood, and probably has overlap with other forms of pre-capillary pulmonary hypertension. PH-ILD carries a poor prognosis, and is associated with increased oxygen requirements, and a decline in functional capacity and exercise tolerance. Despite most patients having mild-moderate pulmonary hypertension, more severe pulmonary hypertension and signs of right heart failure are observed in a subset of cases. Clinical suspicion and findings on pulmonary function, computed tomography and echocardiography are often the initial steps towards diagnosis. Definitive diagnosis is obtained by right heart catheterisation demonstrating pre-capillary pulmonary hypertension. Drugs approved for pulmonary arterial hypertension have been investigated in several randomised controlled trials in PH-ILD patients, leading to discouraging results until the recent INCREASE study. This review provides an overview of the current understanding, approach to diagnosis and recent advances in treatment.

Neurovascular Dysregulation and Acute Exercise Intolerance in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: A Randomized, Placebo-Controlled Trial of Pyridostigmine.

BACKGROUND: Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is characterized by intractable fatigue, postexertional malaise, and orthostatic intolerance, but its pathophysiology is poorly understood. Pharmacologic cholinergic stimulation was used to test the hypothesis that neurovascular dysregulation underlies exercise intolerance in ME/CFS. RESEARCH QUESTION: Does neurovascular dysregulation contribute to exercise intolerance in ME/CFS, and can its treatment improve exercise capacity? STUDY DESIGN AND METHODS: Forty-five subjects with ME/CFS were enrolled in a single-center, randomized, double-blind, placebo-controlled trial. Subjects were assigned in a 1:1 ratio to receive a 60-mg dose of oral pyridostigmine or placebo after an invasive cardiopulmonary exercise test (iCPET). A second iCPET was performed 50 min later. The primary end point was the difference in peak exercise oxygen uptake (Vo2). Secondary end points included exercise pulmonary and systemic hemodynamics and gas exchange. RESULTS: Twenty-three subjects were assigned to receive pyridostigmine and 22 to receive placebo. The peak Vo2 increased after pyridostigmine but decreased after placebo (13.3 ± 13.4 mL/min vs -40.2 ± 21.3 mL/min; P < .05). The treatment effect of pyridostigmine was 53.6 mL/min (95% CI, -105.2 to -2.0). Peak vs rest Vo2 (25.9 ± 15.3 mL/min vs -60.8 ± 25.6 mL/min; P < .01), cardiac output (-0.2 ± 0.6 L/min vs -1.9 ± 0.6 L/min; P < .05), and right atrial pressure (1.0 ± 0.5 mm Hg vs -0.6 ± 0.5 mm Hg; P < .05) were greater in the pyridostigmine group compared with placebo. INTERPRETATION: Pyridostigmine improves peak Vo2 in ME/CFS by increasing cardiac output and right ventricular filling pressures. Worsening peak exercise Vo2, cardiac output, and right atrial pressure following placebo may signal the onset of postexertional malaise. We suggest that treatable neurovascular dysregulation underlies acute exercise intolerance in ME/CFS. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov; No.: NCT03674541; URL: www. CLINICALTRIALS: gov.