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Background: The European Chronic Thromboembolic Pulmonary Hypertension (CTEPH) registry, conducted between 2007 and 2012, reported the major impact of pulmonary endarterectomy (PEA) on the long-term survival of patients with CTEPH. Since then, 2 additional treatments for inoperable CTEPH have become available: balloon pulmonary angioplasty (BPA), and an approved oral drug therapy with the guanylate cyclase stimulator riociguat. The current registry aimed to evaluate the effect of these new therapeutic approaches in a worldwide context., Methods: Participation in this international global registry included 34 centers in 20 countries. Between February 2015 and September 2016, 1009 newly diagnosed, consecutive patients were included and followed until September 2019., Results: Overall, 605 patients (60%) underwent PEA and 185 (18%) underwent BPA; 76% of the 219 remaining patients not receiving mechanical intervention (ie, neither PEA nor BPA) were treated with pulmonary hypertension drugs. Of patients undergoing PEA and BPA, 38% and 78% also received drugs for pulmonary hypertension, respectively. Median age at diagnosis was higher in the BPA and No PEA/BPA groups than in the PEA group: 66 and 69, respectively, versus 60 years. Pulmonary vascular resistance (PVR) was similar in all groups, with an average of 643 dynes.s.cm -5 . During the observation period (>3 years; ≤5.6 years), death was reported in 7%, 11%, and 27% of patients treated by PEA and BPA, and those receiving no mechanical intervention ( P <0.001). In Kaplan-Meier analysis, 3-year survival was 94%, 92%, and 71% in the 3 groups, respectively. PEA 3-year survival improved by 5% from that observed between 2007 and 2012. There was no survival difference in patients receiving vitamin K antagonists and non-vitamin K oral anticoagulants ( P =0.756). In Cox regression, reduced mortality was associated with: PEA and BPA in the global cohort; history of venous thromboembolism and lower PVR in the PEA group; lower right atrial pressure in the BPA group; and use of pulmonary hypertension drugs, oxygen therapy, and lower right atrial pressure, as well as functional class in the group receiving no mechanical intervention., Conclusions: This second international CTEPH registry reveals important improvement in patient survival since the introduction of BPA and an approved drug for pulmonary hypertension. The type of anticoagulation regimen did not influence survival., Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT02656238., Competing Interests: M.D. reports research grants from Janssen, speaker and consultant fees from Altavant, Acceleron, AOP, Bayer, Ferrer, Gossamer, INARI, Janssen, United Therapeutics, and MSD outside the submitted work, and all paid to her institution. She was holder of a Janssen chair for pulmonary hypertension at the KU Leuven. J.P.Z. reports research grants from MSD and consultant fees from Ferrer, Gossamer, Janssen outside submitted work. S.G. reports speaker fees or consultant honoraria from Actelion/Janssen, Bayer AG, MSD, and Pfizer. D.P.J. reports speaker fees and consultancy fees from Janssen outside this submitted work. D.G.K. reports speaker fees, consultancy fees, or funding to attend meetings from Acceleron, Altavant, Ferrer, Janssen, Gossamer, MSD and United Therapeutics and research support from Ferrer and Janssen, all outside of the submitted work. N.H.K. reports receiving speaker fees from Bayer and Janssen; consultancy fees from Bayer, Janssen, Merck, Polarean, Pulnovo, and United Therapeutics; and research support from Altavant and Gossamer Bio. All disclosed fees and support are outside the submitted work. M.M.M. reports consultancy fees and royalties from Wexler Surgical and consultancy fees from Actelion/Janssen and Johnson & Johnson. H.M. reports research grants from Nippon Shinyaku; speaker and consultant fees from Bayer, Janssen, and MSD; speaker fees from Kaneka Medix, Mochida, Nippon Shinyaku, and Nipro, all outside of the submitted work. J.S.O.A. reports personal fees from Bayer and MSD. R.S.K. reports having received speaker fees from AOP Health, Actelion/Janssen, and MSD, all outside of the submitted work. GS reports receiving advisory board and speaker fees from Acceleron, Bayer, Janssen, MSD, and Merck. C.B.W. reports speaker fees or consultant honoraria from Actelion/Janssen, AOP Orphan Pharmaceuticals AG, Bayer AG, BTG, MSD, OrphaCare, and Pfizer. E.M. reports receiving consultancy or speaker fees from Actelion/Janssen, Bayer, and MSD. I.M.L. has relationships with drug companies including AOP Health, Actelion/Janssen, MSD, United Therapeutics, Pulnovo, Medtronic, Neutrolis, and Sanofi; in addition to being investigator in trials involving these companies, relationships include consultancy services, research grants, and membership of scientific advisory boards. The other authors report no conflicts.

Background: NT-proBNP (N-terminal pro brain natriuretic peptide) levels are included in the multiparametric risk assessment approach for pulmonary arterial hypertension (PAH) outlined in PAH guidelines. However, data supporting the use of NT-proBNP risk thresholds in assessing prognosis in PAH are limited. The GRIPHON trial (Prostacyclin [PGI 2 ] Receptor Agonist In Pulmonary Arterial Hypertension) provides an opportunity to assess the prognostic value of NT-proBNP thresholds in a controlled clinical trial and to evaluate the response to selexipag according to these thresholds., Methods: The event-driven GRIPHON trial randomly assigned patients to selexipag or placebo. NT-proBNP was measured at regular intervals in GRIPHON. Here, patients were categorized post hoc into low, medium, and high NT-proBNP subgroups according to 2 independent sets of thresholds: (1) baseline tertiles: <271 ng/L; 271 to 1165 ng/L; >1165 ng/L; and (2) 2015 European Society of Cardiology/European Respiratory Society guidelines cutoffs: <300 ng/L; 300 to 1400 ng/L; >1400 ng/L. Hazard ratios (selexipag versus placebo) with 95% CIs were calculated for the primary end point (composite morbidity/mortality events) by NT-proBNP category at baseline using Cox proportional-hazards models, and at any time during the exposure period using a time-dependent Cox model., Results: With both thresholds, baseline and follow-up NT-proBNP categories were highly prognostic for future morbidity/mortality events during the study ( P<0.0001). In the time-dependent analysis, the risk of experiencing a morbidity/mortality event was 92% and 83% lower in selexipag-treated patients with a low and medium NT-proBNP level, and 90% and 56% lower in placebo-treated patients with a low and medium NT-proBNP level, in comparison with patients with a high NT-proBNP level. Selexipag reduced the risk of morbidity/mortality events across all 3 NT-proBNP categories in both the baseline and time-dependent analyses, with a more pronounced treatment benefit of selexipag seen in the medium and low NT-proBNP subgroups (interaction P values 0.20 and 0.007 in the baseline and time-dependent analyses)., Conclusions: These analyses further establish the prognostic relevance of NT-proBNP levels in PAH and provide first evidence for the association of NT-proBNP level and treatment response. Using 2 similar sets of thresholds, these analyses support the relevance of the low, medium, and high NT-proBNP categories as part of the multiparametric risk assessment approach outlined in the European Society of Cardiology/European Respiratory Society guidelines for the management of PAH patients., Clinical Trial Registration: URL: https://www.clinicaltrials.gov . Unique identifier: NCT01106014.

Background Conducting randomized controlled trials to investigate survival in a rare disease like pulmonary arterial hypertension has considerable ethical and logistical constraints. In many studies, such as the Study with an Endothelin Receptor Antagonist in Pulmonary Arterial Hypertension to Improve Clinical Outcome (SERAPHIN) randomized controlled trial, evaluating survival is further complicated by bias introduced by allowing active therapy among placebo-treated patients who clinically deteriorate. Methods and Results SERAPHIN enrolled and followed patients in the same time frame as the US Registry to Evaluate Early And Long-term PAH Disease Management, providing an opportunity to compare observed survival for SERAPHIN patients with predicted survival had they received real-world treatment as in the Registry to Evaluate Early And Long-term PAH Disease Management. From the Registry to Evaluate Early And Long-term PAH Disease Management (N=3515), 734 patients who met SERAPHIN eligibility criteria were selected and their data used to build a prediction model for time to death up to 3 years based on 10 baseline prognostic variables. The model was used to predict a survival curve for each of the 742 SERAPHIN patients via their baseline variables. The average of these predicted survival curves was compared with observed survival of the placebo (n=250) and macitentan 10 mg (n=242) groups using a log-rank test and Cox proportional hazard model. Observed mortality risk for patients randomized to placebo, 62% of whom were taking background pulmonary arterial hypertension therapy, tended to be lower than that predicted for all SERAPHIN patients (16% lower; P=0.259). The observed placebo survival curve closely approximated the predicted survival curve for the first 15 months. Beyond that time, observed risk of mortality decreased compared with predicted mortality, potentially reflecting the impact of crossover of patients in the placebo group to active therapy. Over 3 years, risk of mortality observed with macitentan 10 mg was 35% lower than predicted mortality ( P=0.010). Conclusions These analyses show that, in a rare disease, real-world observational data can complement randomized controlled trial data to overcome some challenges associated with assessing survival in the setting of a randomized controlled trial. Clinical Trial Registration https://www.clinicaltrials.gov . Unique identifiers: NCT00660179 and NCT00370214.

Background: Hemodynamic variables such as cardiac index and right atrial pressure have consistently been associated with survival in pulmonary arterial hypertension (PAH) at the time of diagnosis. Recent studies have suggested that pulmonary arterial compliance may also predict prognosis in PAH. The prognostic importance of hemodynamic values achieved after treatment initiation is less well established., Methods: Our objective was to evaluate the prognostic importance of clinical and hemodynamic variables during follow-up, including pulmonary arterial compliance, after initial management in PAH. We evaluated incident patients with idiopathic, drug- and toxin-induced, or heritable PAH enrolled in the French pulmonary hypertension registry between 2006 and 2016 who had a follow-up right-sided heart catheterization (RHC). The primary outcome was death or lung transplantation. We used stepwise Cox regression and the Kaplan-Meier method to assess variables obtained at baseline and at first follow-up RHC., Results: Of 981 patients, a primary outcome occurred in 331 patients (33.7%) over a median follow-up duration of 2.8 years (interquartile range, 1.1-4.6 years). In a multivariable model considering only baseline variables, no hemodynamic variables independently predicted prognosis. Median time to first follow-up RHC was 4.6 months (interquartile range, 3.7-7.8 months). At first follow-up RHC (n=763), New York Heart Association functional class, 6-minute walk distance, stroke volume index (SVI), and right atrial pressure were independently associated with death or lung transplantation, adjusted for age, sex, and type of PAH. Pulmonary arterial compliance did not independently predict outcomes at baseline or during follow-up. The adjusted hazard ratio for SVI was 1.28 (95% confidence interval, 1.11-1.49; P <0.01) per 10-mL/m 2 decrease and for right atrial pressure was 1.05 (95% confidence interval, 1.02-1.09; P <0.01) per 1-mm Hg increase. Among patients who had 2 (n=355) or 3 (n=193) low-risk prognostic features at follow-up, including a cardiac index ≥2.5 L·min -1 ·m -2 , 6-minute walk distance >440 m, and New York Heart Association class I or II functional class, lower SVI was still associated with higher rates of death or lung transplantation ( P <0.01)., Conclusions: SVI and right atrial pressure were the hemodynamic variables that were independently associated with death or lung transplantation at first follow-up RHC after initial PAH treatment. These findings suggest that the SVI could be a more appropriate treatment target than cardiac index in PAH., (© 2017 American Heart Association, Inc.)

Contrasting with the major attention that left heart failure has received, right heart failure remains understudied both at the preclinical and clinical levels. However, right ventricle failure is a major predictor of outcomes in patients with precapillary pulmonary hypertension because of pulmonary arterial hypertension, and in patients with postcapillary pulmonary hypertension because of left heart disease. In pulmonary hypertension, the status of the right ventricle is one of the most important predictors of both morbidity and mortality. Paradoxically, there are currently no approved therapies targeting the right ventricle in pulmonary hypertension. By analogy with the key role of β-blockers in the management of left heart failure, some authors have proposed to use these agents to support the right ventricle function in pulmonary hypertension. In this review, we summarize the current knowledge on the use of β-blockers in pulmonary hypertension., (© 2017 American Heart Association, Inc.)

Background: Mutations in the KCNK3 gene have been identified in some patients suffering from heritable pulmonary arterial hypertension (PAH). KCNK3 encodes an outward rectifier K(+) channel, and each identified mutation leads to a loss of function. However, the pathophysiological role of potassium channel subfamily K member 3 (KCNK3) in PAH is unclear. We hypothesized that loss of function of KCNK3 is a hallmark of idiopathic and heritable PAH and contributes to dysfunction of pulmonary artery smooth muscle cells and pulmonary artery endothelial cells, leading to pulmonary artery remodeling: consequently, restoring KCNK3 function could alleviate experimental pulmonary hypertension (PH)., Methods and Results: We demonstrated that KCNK3 expression and function were reduced in human PAH and in monocrotaline-induced PH in rats. Using a patch-clamp technique in freshly isolated (not cultured) pulmonary artery smooth muscle cells and pulmonary artery endothelial cells, we found that KCNK3 current decreased progressively during the development of monocrotaline-induced PH and correlated with plasma-membrane depolarization. We demonstrated that KCNK3 modulated pulmonary arterial tone. Long-term inhibition of KCNK3 in rats induced distal neomuscularization and early hemodynamic signs of PH, which were related to exaggerated proliferation of pulmonary artery endothelial cells, pulmonary artery smooth muscle cell, adventitial fibroblasts, and pulmonary and systemic inflammation. Lastly, in vivo pharmacological activation of KCNK3 significantly reversed monocrotaline-induced PH in rats., Conclusions: In PAH and experimental PH, KCNK3 expression and activity are strongly reduced in pulmonary artery smooth muscle cells and endothelial cells. KCNK3 inhibition promoted increased proliferation, vasoconstriction, and inflammation. In vivo pharmacological activation of KCNK3 alleviated monocrotaline-induced PH, thus demonstrating that loss of KCNK3 is a key event in PAH pathogenesis and thus could be therapeutically targeted., (© 2016 American Heart Association, Inc.)

Background: Chronic thromboembolic pulmonary hypertension, a rare complication of acute pulmonary embolism, is characterized by fibrothrombotic obstructions of large pulmonary arteries combined with small-vessel arteriopathy. It can be cured by pulmonary endarterectomy, and can be clinically improved by medical therapy in inoperable patients. A European registry was set up in 27 centers to evaluate long-term outcome and outcome correlates in 2 distinct populations of operated and not-operated patients who have chronic thromboembolic pulmonary hypertension., Methods and Results: A total of 679 patients newly diagnosed with chronic thromboembolic pulmonary hypertension were prospectively included over a 24-month period. Estimated survival at 1, 2, and 3 years was 93% (95% confidence interval [CI], 90-95), 91% (95% CI, 87-93), and 89% (95% CI, 86-92) in operated patients (n=404), and only 88% (95% CI, 83-91), 79% (95% CI, 74-83), and 70% (95% CI, 64-76) in not-operated patients (n=275). In both operated and not-operated patients, pulmonary arterial hypertension-targeted therapy did not affect survival estimates significantly. Mortality was associated with New York Heart Association functional class IV (hazard ratio [HR], 4.16; 95% CI, 1.49-11.62; P=0.0065 and HR, 4.76; 95% CI, 1.76-12.88; P=0.0021), increased right atrial pressure (HR, 1.34; 95% CI, 0.95-1.90; P=0.0992 and HR, 1.50; 95% CI, 1.20-1.88; P=0.0004), and a history of cancer (HR, 3.02; 95% CI, 1.36-6.69; P=0.0065 and HR, 2.15; 95% CI, 1.18-3.94; P=0.0129) in operated and not-operated patients, respectively. Additional correlates of mortality were bridging therapy with pulmonary arterial hypertension-targeted drugs, postoperative pulmonary hypertension, surgical complications, and additional cardiac procedures in operated patients, and comorbidities such as coronary disease, left heart failure, and chronic obstructive pulmonary disease in not-operated patients., Conclusions: The long-term prognosis of operated patients currently is excellent and better than the outcome of not-operated patients., (© 2016 American Heart Association, Inc.)

Fibrosing mediastinitis is caused by a proliferation of fibrous tissue in the mediastinum with encasement of mediastinal viscera and compression of mediastinal bronchovascular structures. Pulmonary hypertension (PH) is a severe complication of fibrosing mediastinitis caused by extrinsic compression of the pulmonary arteries and/or veins.We have conducted a retrospective observational study reviewing clinical, functional, hemodynamic, radiological characteristics, and outcome of 27 consecutive cases of PH associated with fibrosing mediastinitis diagnosed between 2003 and 2014 at the French Referral Centre for PH.Fourteen men and 13 women with a median age of 60 years (range 18-84) had PH confirmed on right heart catheterization. The causes of fibrosing mediastinitis were sarcoidosis (n = 13), tuberculosis-infection confirmed or suspected (n = 9), mediastinal irradiation (n = 2), and idiopathic (n = 3). Sixteen patients (59%) were in NYHA functional class III and IV. Right heart catheterization confirmed moderate to severe PH with a median mean pulmonary artery pressure of 42 mm Hg (range 27-90) and a median cardiac index of 2.8 L/min/m (range 1.6-4.3). Precapillary PH was found in 22 patients, postcapillary PH in 2, and combined postcapillary and precapillary PH in 3. Severe extrinsic compression of pulmonary arteries (>60% reduction in diameter) was evidenced in 2, 8, and 12 patients at the main, lobar, or segmental levels, respectively. Fourteen patients had at least one severe pulmonary venous compression with associated pleural effusion in 6 of them. PAH therapy was initiated in 7 patients and corticosteroid therapy (0.5-1 mg/kg/day) was initiated in 3 patients with sarcoidosis, with 9 other being already on low-dose corticosteroids. At 1-year follow-up, 3 patients had died and among the 21 patients evaluated, 3 deteriorated, 14 were stable, and only 4 patients with sarcoidosis improved (4 receiving corticosteroids and 1 receiving corticosteroids and PAH therapy). Survival was 88%, 73%, and 56% at 1, 3, and 5 years, respectively.We found no clear clinical improvement with the use of specific PAH therapy. Corticosteroid therapy may be associated with clinical improvement, in some patients with fibrosing mediastinitis due to sarcoidosis. Although never performed for this indication, lung transplantation may be proposed in eligible patients with severe PH and fibrosing mediastinitis.

Background: Pulmonary veno-occlusive disease (PVOD) is an uncommon form of pulmonary hypertension characterized by the obstruction of small pulmonary veins and a dismal prognosis. PVOD may be sporadic or heritable because of biallelic mutations of the EIF2AK4 gene coding for GCN2. Isolated case reports suggest that chemotherapy may be a risk factor for PVOD., Methods and Results: We reported on the clinical, functional, and hemodynamic characteristics and outcomes of 7 cases of PVOD induced by mitomycin-C (MMC) therapy from the French Pulmonary Hypertension Registry. All patients displayed squamous anal cancer and were treated with MMC alone or MMC plus 5-fluoruracil. The estimated annual incidence of PVOD in the French population that have anal cancer is 3.9 of 1000 patients, which is much higher than the incidence of PVOD in the general population (0.5/million per year). In rats, intraperitoneal administration of MMC induced PVOD, as demonstrated by pulmonary hypertension at right-heart catheterization at days 21 to 35 and major remodeling of small pulmonary veins associated with foci of intense microvascular endothelial-cell proliferation of the capillary bed. In rats, MMC administration was associated with dose-dependent depletion of pulmonary GCN2 content and decreased smad1/5/8 signaling. Amifostine prevented the development of MMC-induced PVOD in rats., Conclusions: MMC therapy is a potent inducer of PVOD in humans and rats. Amifostine prevents MMC-induced PVOD in rats and should be tested as a preventive therapy for MMC-induced PVOD in humans. MMC-induced PVOD in rats represents a unique model to test novel therapies in this devastating orphan disease., (© 2015 American Heart Association, Inc.)

Background: The vascular remodeling responsible for pulmonary arterial hypertension (PAH) involves predominantly the accumulation of α-smooth muscle actin-expressing mesenchymal-like cells in obstructive pulmonary vascular lesions. Endothelial-to-mesenchymal transition (EndoMT) may be a source of those α-smooth muscle actin-expressing cells., Methods and Results: In situ evidence of EndoMT in human PAH was obtained by using confocal microscopy of multiple fluorescent stainings at the arterial level, and by using transmission electron microscopy and correlative light and electron microscopy at the ultrastructural level. Findings were confirmed by in vitro analyses of human PAH and control cultured pulmonary artery endothelial cells. In addition, the mRNA and protein signature of EndoMT was recognized at the arterial and lung level by quantitative real-time polymerase chain reaction and Western blot analyses. We confirmed our human observations in established animal models of pulmonary hypertension (monocrotaline and SuHx). After establishing the first genetically modified rat model linked to BMPR2 mutations (BMPR2(Δ140Ex1/+) rats), we demonstrated that EndoMT is linked to alterations in signaling of BMPR2, a gene that is mutated in 70% of cases of familial PAH and in 10% to 40% of cases of idiopathic PAH. We identified molecular actors of this pathological transition, including twist overexpression and vimentin phosphorylation. We demonstrated that rapamycin partially reversed the protein expression patterns of EndoMT, improved experimental PAH, and decreased the migration of human pulmonary artery endothelial cells, providing the proof of concept that EndoMT is druggable., Conclusions: EndoMT is linked to alterations in BPMR2 signaling and is involved in the occlusive vas cular remodeling of PAH, findings that may have therapeutic implications., (© 2015 American Heart Association, Inc.)

Background: By its inhibitory effect on platelet-derived growth factor signaling, imatinib could be efficacious in treating patients with pulmonary arterial hypertension (PAH)., Methods and Results: Imatinib in Pulmonary Arterial Hypertension, a Randomized, Efficacy Study (IMPRES), a randomized, double-blind, placebo-controlled 24-week trial, evaluated imatinib in patients with pulmonary vascular resistance ≥ 800 dyne·s·cm(-5) symptomatic on ≥ 2 PAH therapies. The primary outcome was change in 6-minute walk distance. Secondary outcomes included changes in hemodynamics, functional class, serum levels of N-terminal brain natriuretic peptide, and time to clinical worsening. After completion of the core study, patients could enter an open-label long-term extension study. Of 202 patients enrolled, 41% patients received 3 PAH therapies, with the remainder on 2 therapies. After 24 weeks, the mean placebo-corrected treatment effect on 6-minute walk distance was 32 m (95% confidence interval, 12-52; P=0.002), an effect maintained in the extension study in patients remaining on imatinib. Pulmonary vascular resistance decreased by 379 dyne·s·cm(-5) (95% confidence interval, -502 to - 255; P<0.001, between-group difference). Functional class, time to clinical worsening, and mortality did not differ between treatments. Serious adverse events and discontinuations were more frequent with imatinib than placebo (44% versus 30% and 33% versus 18%, respectively). Subdural hematoma occurred in 8 patients (2 in the core study, 6 in the extension) receiving imatinib and anticoagulation., Conclusions: Imatinib improved exercise capacity and hemodynamics in patients with advanced PAH, but serious adverse events and study drug discontinuations were common. Further studies are needed to investigate the long-term safety and efficacy of imatinib in patients with PAH., Clinical Trial Registration: URL: http://www.clinicaltrials.gov. Unique identifier: NCT00902174 (core study); NCT01392495 (extension).

Background: The French pulmonary hypertension (PH) registry allows the survey of epidemiological trends. Isolated cases of precapillary PH have been reported in patients who have chronic myelogenous leukemia treated with the tyrosine kinase inhibitor dasatinib., Methods and Results: This study was designed to describe incident cases of dasatinib-associated PH reported in the French PH registry. From the approval of dasatinib (November 2006) to September 30, 2010, 9 incident cases treated by dasatinib at the time of PH diagnosis were identified. At diagnosis, patients had moderate to severe precapillary PH with functional and hemodynamic impairment. No other incident PH cases were exposed to other tyrosine kinase inhibitors at the time of PH diagnosis. Clinical, functional, or hemodynamic improvements were observed within 4 months of dasatinib discontinuation in all but 1 patient. Three patients required PH treatment with endothelin receptor antagonist (n=2) or calcium channel blocker (n=1). After a median follow-up of 9 months (min-max 3-36), the majority of patients did not demonstrate complete clinical and hemodynamic recovery, and no patients reached a normal value of mean pulmonary artery pressure (≤20 mm Hg). Two patients (22%) died at follow-up (1 of unexplained sudden death and 1 of cardiac failure in the context of septicemia, respectively, 8 and 12 months after dasatinib withdrawal). The lowest estimate of incident PH occurring in patients exposed to dasatinib in France was 0.45%., Conclusions: Dasatinib may induce severe precapillary PH fulfilling the criteria of pulmonary arterial hypertension, thus suggesting a direct and specific effect of dasatinib on pulmonary vessels. Improvement is usually observed after withdrawal of dasatinib.

Background: Chronic thromboembolic pulmonary hypertension (CTEPH) is often a sequel of venous thromboembolism with fatal natural history; however, many cases can be cured by pulmonary endarterectomy. The clinical characteristics and current management of patients enrolled in an international CTEPH registry was investigated., Methods and Results: The international registry included 679 newly diagnosed (≤6 months) consecutive patients with CTEPH, from February 2007 until January 2009. Diagnosis was confirmed by right heart catheterization, ventilation-perfusion lung scintigraphy, computerized tomography, and/or pulmonary angiography. At diagnosis, a median of 14.1 months had passed since first symptoms; 427 patients (62.9%) were considered operable, 247 (36.4%) nonoperable, and 5 (0.7%) had no operability data; 386 patients (56.8%, ranging from 12.0%- 60.9% across countries) underwent surgery. Operable patients did not differ from nonoperable patients relative to symptoms, New York Heart Association class, and hemodynamics. A history of acute pulmonary embolism was reported for 74.8% of patients (77.5% operable, 70.0% nonoperable). Associated conditions included thrombophilic disorder in 31.9% (37.1% operable, 23.5% nonoperable) and splenectomy in 3.4% of patients (1.9% operable, 5.7% nonoperable). At the time of CTEPH diagnosis, 37.7% of patients initiated at least 1 pulmonary arterial hypertension-targeted therapy (28.3% operable, 53.8% nonoperable). Pulmonary endarterectomy was performed with a 4.7% documented mortality rate., Conclusions: Despite similarities in clinical presentation, operable and nonoperable CTEPH patients may have distinct associated medical conditions. Operability rates vary considerably across countries, and a substantial number of patients (operable and nonoperable) receive off-label pulmonary arterial hypertension-targeted treatments.

Neurofibromatosis type I (NF1) is a rare genetic disease caused by mutations in the NF1 gene, which codes for tumor suppressor neurofibromin. NF1 is transmitted as an autosomal dominant and fully penetrant trait with no sex predominance. Precapillary pulmonary hypertension (PH) is a severe complication of NF1, initially described in patients with advanced parenchymal lung disease, which may complicate the course of NF1. We conducted this study to describe clinical, functional, radiologic, and hemodynamic characteristics and outcome of patients with NF1-associated PH. We identified 8 new cases of NF1-associated PH in patients carrying a NF1 gene mutation. No bone morphogenic protein receptor 2 (BMPR2) point mutation or large size rearrangements were identified. Seven female patients and 1 male patient were reported, suggesting a possible female predominance. PH occurred late in the course of the disease (median age, 62 yr; range, 53-68 yr). Dyspnea and signs of right heart failure were the major symptoms leading to the diagnosis of PH. At diagnosis, patients had severe hemodynamic impairment with low cardiac index (median, 2.3 L/min per m2; range, 1.9-4.7) and elevated indexed pulmonary vascular resistance (median, 15.1 mm Hg/L/min per m2; range, 4.5-25.9). All patients were in New York Heart Association functional class III with severe exercise limitation (median 6-min walk distance, 180 m; range, 60-375 m). Most patients had associated parenchymal lung disease, but some had no or mild lung involvement with disproportionate pulmonary vascular disease. Overall, the impact of PH therapy was limited and outcomes were poor. In conclusion, PH represents a rare but severe complication of NF1, characterized by female predominance, late onset in the course of NF1, and severe functional and hemodynamic impairment. Because of poor outcome and limited impact of specific PH therapy, eligible patients require early referral for lung transplantation. Further studies are needed to better understand the pathophysiology and the role, if any, of neurofibromin in NF1-associated PH.

Background: Novel therapies have recently become available for pulmonary arterial hypertension. We conducted a study to characterize mortality in a multicenter prospective cohort of patients diagnosed with idiopathic, familial, or anorexigen-associated pulmonary arterial hypertension in the modern management era., Methods and Results: Between October 2002 and October 2003, 354 consecutive adult patients with idiopathic, familial, or anorexigen-associated pulmonary arterial hypertension (56 incident and 298 prevalent cases) were prospectively enrolled. Patients were followed up for 3 years, and survival rates were analyzed. For incident cases, estimated survival (95% confidence intervals [CIs]) at 1, 2, and 3 years was 85.7% (95% CI, 76.5 to 94.9), 69.6% (95% CI, 57.6 to 81.6), and 54.9% (95% CI, 41.8 to 68.0), respectively. In a combined analysis population (incident patients and prevalent patients diagnosed within 3 years before study entry; n=190), 1-, 2-, and 3-year survival estimates were 82.9% (95% CI, 72.4 to 95.0), 67.1% (95% CI, 57.1 to 78.8), and 58.2% (95% CI, 49.0 to 69.3), respectively. Individual survival analysis identified the following as significantly and positively associated with survival: female gender, New York Heart Association functional class I/II, greater 6-minute walk distance, lower right atrial pressure, and higher cardiac output. Multivariable analysis showed that being female, having a greater 6-minute walk distance, and exhibiting higher cardiac output were jointly significantly associated with improved survival., Conclusions: In the modern management era, idiopathic, familial, and anorexigen-associated pulmonary arterial hypertension remains a progressive, fatal disease. Mortality is most closely associated with male gender, right ventricular hemodynamic function, and exercise limitation.

Objectives: To examine baseline characteristics and outcome, and to determine variables affecting survival in patients with pulmonary arterial hypertension (PAH) associated with HIV infection (PAH-HIV) in the modern era of highly-active antiretroviral therapy (HAART) and specific PAH therapy., Design: Retrospective review of data from PAH-HIV patients without other associated risk factors for PAH, and comparison with previous series., Methods: Data were reviewed for 77 consecutive patients treated at the French Reference Centre for Pulmonary Hypertension between October 2000 and January 2008. Results were expressed as median [1st-3rd quartile] values., Results: At diagnosis of PAH, 81% patients were on HAART, 79% had a CD4+ count more than 200 cells/microl and 49% had undetectable HIV load. New York Heart Association functional class assessment was II (22%), III (69%), and IV (9%). Six-minute walk distance (6MWD) was 375 [288-421] m, and pulmonary vascular resistance was 689 [524-852] dyn s/cm(5). All patients received HAART irrespective of HIV disease stage. Specific PAH therapy was started in 50 patients and led to improvements in 6MWD and haemodynamic parameters. In patients who did not receive specific PAH therapy, 6MWD improved but haemodynamics did not change. Overall survival rate was 88% at 1 year and 72% at 3 years. On multivariate analysis, cardiac index more than 2.8 l/min per m(2) and CD4+ lymphocyte count more than 200 cells/microl were independent predictors of survival., Conclusion: In patients with PAH-HIV, HAART seems unable to improve haemodynamic parameters. Prognosis in PAH-HIV is mainly related to CD4+ lymphocyte count and cardiac function.

Background: This large, prospective, multicentric study was performed to analyze the distribution of tricuspid regurgitation velocity (TRV) values during exercise and hypoxia in relatives of patients with idiopathic and familial pulmonary arterial hypertension (PAH) and in healthy control subjects. We tested the hypothesis that relatives of idiopathic/familial PAH patients display an enhanced frequency of hypertensive TRV response to stress and that this response is associated with mutations in the bone morphogenetic protein receptor II (BMPR2) gene., Methods and Results: TRV was estimated by Doppler echocardiography during supine bicycle exercise in normoxia and during 120 minutes of normobaric hypoxia (FIO(2)=12%; approximately 4500 m) in 291 relatives of 109 PAH patients and in 191 age-matched control subjects. Mean maximal TRVs were significantly higher in PAH relatives during both exercise and hypoxia. During exercise, 10% of control subjects but 31.6% of relatives (P<0.0001) exceeded the 90% quantile of mean maximal TRV seen in control subjects. Hypoxia revealed hypertensive TRV in 26% of relatives (P=0.0029). Among control subjects, TRV at rest was not related to age, sex, body mass index, systemic blood pressure, smoking status, or heart rate. Within kindreds identified as harboring deleterious mutations of the BMPR2 gene, a hypertensive TRV response occurred significantly more often compared with those without detected mutations., Conclusions: Pulmonary hypertensive response to exercise and hypoxia in idiopathic/familial PAH relatives appears as a genetic trait with familial clustering, being correlated to but not caused by a BMPR2 mutation. The suitability of this trait to predict manifest PAH development should be addressed in long-term follow-up studies.

There has been substantial progress in our understanding of the pathogenesis and clinical consequences of infection with HIV since the virus was first identified more than 20 years ago. The details of the viral replication cycle are increasingly better understood as are the identification of host elements that both regulate viral replication and are necessary for it. Greater understanding of these events has resulted in the development of therapies for HIV infection and as a consequence there has been a dramatic improvement in overall survival in the era of HAART. With this improvement in survival has come an increasing recognition of the importance of many long-term sequelae of subclinical immune deficiency and the attendant immune activation that characterize HIV infection. One complication of chronic HIV infection for which the pathogenesis is obscure is pulmonary arterial hypertension (PAH). Cases of HIV-related PAH (PAH-HIV) have been recognized with increasing frequency in recent years. Although it is likely that PAH-HIV has an underlying etiology specifically related to HIV infection, it shares several key clinical and pathological similarities with other forms of PAH. This article outlines the features, classification and treatment of PAH, and recent theories about the underlying etiology of the disease. We will also discuss the occurrence of PAH in HIV infection and propose some hypotheses regarding pathogenesis that will be covered in more detail in the accompanying articles in this supplement.

Intravenous epoprostenol improves exercise capacity and survival in patients with pulmonary arterial hypertension (PAH); however, chemical instability and a short half-life have caused limitations in its use. The chemically stable prostacyclin analogue treprostinil has a longer half-life, and improves hemodynamics and signs/symptoms of PAH. This study investigated the feasibility of transitioning patients with PAH from intravenous epoprostenol to intravenous treprostinil using a rapid switch protocol. Twelve PAH patients were enrolled in a 12 week prospective open label study. Patients were switched from intravenous epoprostenol to intravenous treprostinil (1:1 ng/kg/min) by a direct switch of the medication reservoir from epoprostenol to treprostinil. The dose of treprostinil was adjusted throughout the study to achieve a 2-fold increase of treprostinil compared with the baseline epoprostenol dose. Rapid transition to treprostinil was achieved without serious adverse events and, baseline clinical status was maintained over 12 weeks. The mean baseline epoprostenol dose was 28 +/- 14 ng/kg/min. At week 12, the mean treprostinil dose was 62 +/- 30 ng/kg/min. All patients reported less prostacyclin-related side effects with treprostinil and remained on treprostinil after study completion. Selected patients with PAH can be safely transitioned from intravenous epoprostenol to intravenous treprostinil using a rapid switch protocol.

Hyperplasia of pulmonary artery smooth muscle cells (PA-SMCs) is a hallmark pathological feature of pulmonary hypertension (PH). Serotonin (5-HT) is involved in the hyperplasia through its interactions with specific receptors and internalization by a specific plasma membrane transporter. We investigated the expression and role of the 5-HT transporter (5-HTT) and 5-HT1B, 5-HT2A, and 5-HT2B receptors in lungs and isolated PA-SMCs from patients with primary PH (n=14), pulmonary veno-occlusive disease (n=4), or secondary PH (SPH, n=8) and nonpulmonary hypertensive control subjects. Whereas strong immunostaining for the three receptor types and 5-HTT was seen in remodeled pulmonary vessels from patients in all PH categories, only 5-HTT expression was increased in lungs and cultured PA-SMCs from patients versus controls. The increased growth response of PA-SMCs from patients with primary PH, pulmonary veno-occlusive disease, or SPH to 5-HT or serum was entirely attributable to 5-HTT overexpression, because 5-HTT inhibitors but not 5-HT receptor antagonists abolished 5-HT mitogenic activity and reduced the serum-induced growth response to similar levels in patients as in controls. The L-allelic variant of the 5-HTT gene promoter, which is associated with 5-HTT overexpression, was present homozygously in 14 of 25 (56%) lung transplantation patients with SPH but in only 27% of controls. Polymorphism of the 5-HTT gene promoter was only partly responsible for the increased 5-HTT expression in PH, because PA-SMCs from patients exhibited higher 5-HTT levels than same-genotype cells from controls and no additional promoter sequence alterations were found. We conclude that 5-HTT overexpression is a common pathogenic mechanism in various forms of PH.

Background: The presence of dysfunctional von Willebrand factor (vWF) in pulmonary arterial hypertension (PAH) was suggested to be related to increased proteolysis., Methods and Results: In 10 patients with severe PAH, we studied the proteolysis of plasma vWF (vWF levels, multimeric distribution, proteolytic pattern, and cleaving protease activity) and hemodynamic variables (mean pulmonary artery pressure, cardiac index, and total pulmonary vascular resistance) at baseline and 30 days after initiation of continuous prostacyclin infusion. At baseline, vWF levels were significantly increased, vWF proteolysis was excessive, and vWF-cleaving protease activity remained normal. These biological abnormalities were reversible and paralleled the improvement of hemodynamics under vasodilator treatment with prostacyclin., Conclusions: The excessive proteolysis of vWF in PAH is likely to be related to an increased susceptibility of vWF to proteases induced by high shear rates rather than to an enhanced release of enzymes.

Elevated plasma serotonin is associated with primary pulmonary hypertension (PPH). To test whether this elevation could be related to platelet activation, the 2 pools of blood serotonin (platelets and plasma) and plasma 5-hydroxyindoleacetic acid (5-HIAA) as well as markers of platelet activation (alpha(IIb)beta(3), CD36, P-selectin, and CD63 membrane epitopes) were measured in 16 patients with severe PPH (group 1) before and at days 10 and 40 of treatment with a continuous infusion of epoprostenol (prostacyclin). The same biological parameters were also measured in 19 healthy subjects (group 2) and in 10 patients after cardiovascular surgery with extracorporeal circulation (group 3), a condition known to profoundly activate the platelets. Twelve PPH patients showed hemodynamic and clinical improvement, 3 remained stable, and 1 had the treatment stopped because of clinical aggravation. At day 0, mean plasma serotonin (5-hydroxytryptamine [5-HT]) concentration was much higher in PPH patients than in normal subjects (34.4+/-21.2 versus 9.1+/-6.0 nmol/L, respectively; P:<0.001) and positively correlated with total pulmonary resistance. The mean platelet 5-HT content was not significantly different in PPH compared with normal individuals. Mean plasma 5-HIAA concentrations were much higher in PPH than in normal patients (162+/-57 versus 61+/-7 nmol/L, respectively; P<0.001). These parameters did not significantly change during epoprostenol treatment. There was no correlation between the changes in plasma 5-HT during treatment and clinical or hemodynamic improvement. In PPH patients, the mean platelet volume significantly decreased (ANOVA, P<0.01) during treatment. Positive correlations were evidenced between the size of platelets and the number of alpha(IIb)beta(3) and CD36 epitopes. When compared with control platelets, the number of alpha(IIb)beta(3) epitopes detected on PPH platelets at day 0 tended to be higher, but this difference did not reach a statistical significance (41 300+/-7140 for PPH patients versus 36 010+/-3930 for control subjects, P=0.069). The number of CD36 epitopes, in the range of controls at day 0 (11 590+/-5080 for PPH patients versus 11 900+/-1790 for control subjects), decreased during treatment (ANOVA, P=0.038) and became significantly low at day 40 (8660+/-3520, P<0.001). The number of CD63 epitopes was not elevated, and P-selectin was never detected at any time point on PPH platelets. This glycoprotein profile indicates that the platelets of PPH patients were not highly activated but had an accelerated turnover and returned to normal under epoprostenol treatment without change of the elevated plasma serotonin, characteristic of PPH. In conclusion, neither platelet activation nor a significant alteration of the 5-HT endothelial metabolism explains the high level of plasma 5-HT in PPH patients. The 5-HT plasma concentration is not a predictive marker of the severity of PPH, and its evolution is independent of the clinical and hemodynamic status. Treatment by a potent antiaggregating agent, epoprostenol, does not affect the increase of plasma 5-HT, despite a therapeutic benefit.

RANTES (regulated upon activation, normally T expressed and secreted) is a chemoattractant for macrophages, memory T lymphocytes, and eosinophils. We investigated whether intrapulmonary production of the chemokine RANTES contributes to the recruitment of immune cells during lung transplantation complications. RANTES concentration was measured in bronchoalveolar lavage (BAL) fluids using an ELISA assay. It was significantly higher during CMV pneumonitis (36.2 +/- l6 pg/ml, n=12, P=0.031) and allograft rejection (31.1 +/- 8.5 pg/ml, n=27, P=0.013) than in patients without complications (9.1 +/- 2.3 pg/ml, n=22). At least some of the RANTES was produced by lung macrophages: BAL macrophages cultured for 24 hr spontaneously released larger amount of RANTES during CMV pneumonitis (140 +/- 53 pg/ml, n=8, P=0.002) and allograft rejection (84 +/- 44 pg/ml, n=11, P=0.037) than in control patients (15.2 +/- 6.5 pg/ml, n=21). Moreover, macrophages in transbronchial biopsies were labeled by an anti-RANTES mAb. RANTES production by BAL macrophages was followed in 2 patients with CMV pneumonitis. It remained high as long as CMV-induced cytopathic effects or clinical symptoms were present, but it returned to baseline as the infection was controlled. These results suggest that the intrapulmonary production of the chemokine RANTES by activated macrophages contributes to the intrapulmonary accumulation of immune cells during complications of lung transplantation.

Background: The short-term vasodilator response to prostacyclin (PGI2) in patients with primary pulmonary hypertension (PPH) is not only unpredictable but also extremely variable in magnitude. In this retrospective study, we attempted to evaluate in a nonselected population of patients with PPH the degree of vasodilatation achieved during short-term infusion of PGI2 and to investigate whether patients with PPH differed in terms of baseline characteristics and prognoses, according to the level of vasodilatation achieved during initial testing with PGI2., Methods and Results: Between 1984 and 1992, 91 consecutive patients with PPH underwent catheterization of the right side of the heart with a short-term vasodilator trial with PGI2 (5 to 10 ng.kg-1.min-1). According to the level of vasodilatation achieved during PGI2 infusion, patients were divided into three groups: nonresponding (NR, n = 40), moderately responding (MR, n = 42), and highly responding (HR, n = 9) patients. All three groups were defined by a decrease in total pulmonary resistance index (TPRi) of < 20%, between 20% and 50%, and > 50%, respectively, relative to control values. Prolonged oral vasodilator therapy was subsequently started only in MR and HR patients. All patients had long-term oral anticoagulant therapy. The survival rate at 2 years (transplant recipients excluded) was significantly higher in HR patients compared with NR and MR patients (62% versus 38% and 47% survivors, respectively; P < .05). Comparisons between groups showed no significant differences in baseline hemodynamics or clinical characteristics except for a longer time between onset of symptoms and diagnosis (ie, first catheterization) of PPH in HR patients than in NR and MR patients (71 +/- 61 versus 35 +/- 34 and 21 +/- 21 months, respectively; P < .05)., Conclusions: In this study, patients with PPH exhibiting a decrease in TPRi > 50% during short-term PGI2 challenge at the time of diagnosis had longer disease evolutions and better prognoses than patients with a lower vasodilator response.

Background: Previously reported cases of patients with pulmonary hypertension (PH) and human immunodeficiency virus (HIV) infection are poorly documented regarding baseline hemodynamics and potential for pulmonary vasodilatation. The purpose of this report was to compare HIV-infected patients who had PH with non-HIV-infected patients who had primary pulmonary hypertension (PPH) in terms of (1) clinical characteristics, (2) hemodynamics in baseline conditions and during a short-term vasodilator trial with epoprostenol, and (3) survival., Methods and Results: Between April 1987 and August 1992, 20 HIV-infected patients with PH and 93 non-HIV-infected patients with PPH were referred to our department. At the time of referral, baseline right-side heart hemodynamics were obtained in addition to demographic variables and medical history. A short-term vasodilator trial with epoprostenol was performed in 19 of 20 HIV-infected and 86 of 93 non-HIV-infected patients. Outcome and survival were analyzed and compared for both groups (22 transplant recipients were excluded from the group of patients with PPH). At the time of diagnosis of PH, HIV-infected patients significantly differed from non-HIV-infected patients in age (32 +/- 5 versus 42 +/- 13 years; P < .05) and degree of disability (New York Heart Association functional class III or IV, 50% versus 75%; P < .01). The proportion of disease states known to be associated with PPH (Raynaud's phenomenon, migraine, collagen disease without overt symptoms and signs, or a positive family history of PPH) was similar in the two groups. HIV-infected patients had a severe but significantly lower level of PH than patients with PPH. The percentage of responders to epoprostenol and the level achieved in pulmonary vasodilatation were similar in the two groups. PH was the cause of death in 8 of the 10 HIV-infected patients who died within 1 year after the diagnosis of PH. Overall survival was poor and not significantly different between the two groups. Pathological findings in lung tissue obtained from 3 HIV-infected patients were close to those seen in most of the lung specimens available from 27 patients with PPH and resembled plexogenic pulmonary arteriopathy., Conclusions: These results support the view that HIV infection may now be regarded as another common disease state that can be associated with PPH development. The lower initial severity in HIV-infected patients may be due to the close medical attention usually devoted to such patients, who may account for an earlier diagnosis. However, the overall survival rate of HIV-infected patients with PH appeared to be as poor as in non-HIV-infected patients with PPH.

Interleukin-6 (IL-6) is a pleiotropic cytokine that is a regulator of inflammation and immunity. As production of IL-6 may be an important mechanism by which local and systemic inflammatory processes are regulated during lung transplantation, we measured this cytokine concentration in the serum and bronchoalveolar lavage fluid (BALF) collected in 27 lung recipients. IL-6 bioactivity was analyzed using a B cell hybridoma proliferation assay (B9 cell line). Three groups of clinical situations were analyzed: control lung recipients, rejections, and CMV pneumonia. Serum IL-6 concentrations (mean +/- SEM) were 24.2 +/- 3.3 U/ml in the 26 control samples. In 20 allograft rejection episodes, the serum IL-6 concentration was higher than in control samples but the difference was not significant (59.3 +/- 20.5 U/ml, P > 0.05). IL-6 serum levels were significantly increased during the 14 CMV pneumonias (61.2 +/- 11.5 U/ml, P < 0.01). In BALF, IL-6 levels were increased during CMV pneumonia (52.4 +/- 21.9 U/ml BALF), and to a lesser extent during rejection events (14.1 +/- 3.7 U/ml BALF), as compared with controls (5.6 +/- 1.6 U/ml BALF, P < 0.005, and P < 0.05, respectively). Similar results were observed when IL-6/albumin and IL-6/urea ratios were determined so as to compensate for possible dilution effects in BALF. IL-6 in BALF was produced in situ during CMV pneumonia as shown by in situ hybridization experiments that revealed a significant number of IL-6 gene-expressing alveolar cells in this condition. IL-6 concentrations in the serum and in the BALF were compared. There was no correlation between serum and BALF IL-6 concentrations, showing that serum IL-6 levels do not accurately reflect intrapulmonary IL-6 levels do not accurately reflect intrapulmonary IL-6 production. Thus IL-6 is produced within lung transplants during CMV pneumonia, and to a lesser extent during allograft rejection.

To assess the value of CT in chronic pulmonary embolism (CPE), CT scans and pulmonary angiograms of 21 consecutive patients were reviewed. Computed tomography was better than angiography in assessing proximal clots (three thrombi not seen by angiography, three angiographic false-positives confirmed by surgery). Furthermore, CT was able to analyze pulmonary arteries distal to angiographic amputations. Computed tomography was less sensitive than angiography for vascular distortions (38 vs. 50%) and stenosis (35 vs. 71.8%). Pulmonary infarctions were better detected and characterized by CT than by angiography. Isolated parenchymal ground-glass opacities were seen by CT in 18 patients, especially in those with right cardiomegaly. High resolution CT delineated them better than did standard CT. Computed tomography may be a useful adjunct to angiography in the assessment of CPE.

Background: We compared the efficacy and safety of different dosages of a low-molecular-weight heparin, CY 216 D (Fraxiparine), in the treatment of submassive pulmonary embolism with unfractionated heparin in a prospective, randomized, dose-finding study., Methods and Results: The primary outcome was the evolution of pulmonary vascular obstruction. We enrolled 101 patients. Four patient groups were formed: standard heparin by continuous intravenous infusion (group 1) and Fraxiparine subcutaneously 400, 600, and 900 anti-Xa Institute Choay units/kg, respectively (groups 2, 3, and 4). Inclusions were stopped prematurely in groups 3 and 4 because of the incidence of major bleedings. At day 8, the improvement of the pulmonary vascular obstruction and the major bleedings were similar in groups 1 and 2., Conclusions: The Fraxiparine dosage of 400 anti-Xa Institute Choay units/kg is as effective and safe as unfractionated heparin in the treatment of submassive pulmonary embolism.

Total parenteral nutrition (TPN) increases CO2 production (VCO2) in patients on intermittent positive-pressure ventilation who cannot match their CO2 excretion to the CO2 load, leading to an increase in PaCO2. We studied gas exchange and blood gas values in six patients with chronic respiratory failure, who were ventilated at low (6 +/- .7 L/min) and high (10 +/- 2 L/min) minute ventilation during three randomized nutritional regimens: control (255 kcal/day), glucose TPN (2550 kcal/day), and lipid TPN (3000 kcal/day). At the two levels of ventilation, TPN compared to control increased VCO2 and PaCO2 (p less than .01) and decreased pH (p less than .001). At low minute ventilation, the increase in VCO2 and the hypercapnic acidosis were less with lipid than with glucose TPN (p less than .05 and p less than .01, respectively). These results indicate that the risk of TPN-induced CO2 retention is lower if minute ventilation is increased before beginning TPN. Conversely, in patients with compromised ventilatory function, this risk could be higher during intermittent mandatory ventilation or weaning from the ventilator.