Pulmonary Veno-occlusive Disease Patients Research Articles

Outcomes and risk assessment in pulmonary veno-occlusive disease.

Pulmonary veno-occlusive disease (PVOD) is a rare and severe subtype of pulmonary arterial hypertension (PAH). Although European Society of Cardiology/European Respiratory Society (ESC/ERS) guidelines advise assessing PAH severity at baseline and during follow-up, no existing risk assessment methods have been validated for PVOD. This study aimed to identify prognostic factors, examine the impact of treatment strategies and evaluate risk assessment methods for PVOD patients. The study analysed all incident PVOD patients included in the French Pulmonary Hypertension Registry between 2006 and 2021. Survival was assessed based on initial treatment strategy and risk status and compared to a matched (age, sex, pulmonary vascular resistance) PAH group. Six risk assessment methods (number of four low-risk and three noninvasive low-risk variables, ESC/ERS guidelines three-strata and four-strata models, REVEAL 2.0 and Lite 2) were applied at baseline and early follow-up, and their accuracy was compared using Harrell's c-statistic. Among the 327 included PVOD patients, survival rates at 1, 3 and 5 years were 86%, 50% and 27%, respectively. Multivariate analysis showed that only 6-min walk distance was associated with survival, with no significant difference based on initial treatment strategy. All six risk assessment methods could discriminate mortality risk, and the ESC/ERS four-strata model was the most accurate at both baseline and follow-up (C-index 0.64 and 0.74). PVOD survival rates were consistently lower than PAH when comparing baseline risk status using the ESC/ERS four-strata model. PVOD is associated with poor outcomes, and initial treatment strategies do not significantly affect survival. Risk assessment methods can be useful in predicting survival for PVOD patients.

Applicability of the 3-Strata ESC/ERS risk model at baseline in pulmonary veno-occlusive disease

Abstract Introduction The risk of death or lung transplantation in Pulmonary Arterial Hypertension (PAH) is influenced by many factors. The recently published European Society of Cardiology/ European Respiratory Society (ESC/ERC) Guidelines for the study and management of PAH recommend the use of a multiparametric 3-strata model for risk stratification at diagnosis [1]. Heritable pulmonary veno-occlusive disease (PVOD) is an especially infrequent form of PAH caused by homozygous variants in the gene encoding the Eukaryotic Translation Initiation Factor 2 Alpha Kinase 4 (EIF2AK4). PVOD has a dramatically low long-term survival. There is no evidence confirming the applicability of the risk scores in PVOD. Our aim was to evaluate the usefulness of the 3-strata ESC/ERC score at diagnosis in patients with heritable PVOD. Methods We considered patients with the diagnosis of heritable PVOD included in the Spanish registry of PAH (REHAP) between 2011 and 2022. The diagnosis required a homozygous variant in EIF2AK4, and a diagnostic right heart catheterization (RHC). The other group was composed of patients with PAH and pathogenic or likely pathogenic variants in the gene BMPR2. The prognostic evaluation was done when these patients were included in the registry. All participants signed informed consent. Results In the 2011-2022 period up to 32 cases of PVOD in 23 unrelated families and 28 cases in 23 families were collected. 10 patients were excluded due to incomplete RHC at diagnosis. The baseline characteristics of the population can be seen in the Table. After a median follow-up of 16.9 months, up to 15 patients with PVOD needed lung transplantation (46.9%), and 6 patients died (18.7%). On the contrary, only 4 patients needed lung transplantation and one died in the BMPR2 group after a median follow-up of 97.1 months. Most of the included PVOD patients had an intermediate risk of mortality after the application of the 3-strata European model (62.5%), and only one case (3.1%) was categorized as high-risk. There was a non-significant tendency for patients with BMPR2 variants to have lower risk levels. The application of the 3-strata model at diagnosis in patients with PVOD demonstrated a good global prognostic capacity (C Index of 0.707). In our PVOD population, those patients at intermediate risk had a hazard ratio of 9.53 (2.15-42.17, p=0.003) when compared with patients at low risk. Similarly, those patients at high risk at diagnosis had a hazard ratio of 9.49 (0.86-104.69, p=0.066) when compared with patients at intermediate risk (Figure). Conclusions The application of the ESC/ERC three-strata risk tool in patients with PVOD demonstrates a good global prognostic capacity. Nevertheless, the risk of death or lung transplantation can be higher than predicted in this population, enhancing the need for an early evaluation for lung transplantation.Figure

Lipidomic Profile Analysis of Lung Tissues Revealed Lipointoxication in Pulmonary Veno-Occlusive Disease.

Pulmonary veno-occlusive disease (PVOD) is a rare form of pulmonary arterial hypertension (PAH) occurring in a heritable form (hPVOD) due to biallelic inactivating mutations of EIF2AK4 (encoding GCN2, general control nonderepressible 2) or in a sporadic form in older age (sPVOD), following exposure to chemotherapy or organic solvents. In contrast to PAH, PVOD is characterized by a particular remodeling of the pulmonary venous system and the obliteration of small pulmonary veins by fibrous intimal thickening and patchy capillary proliferation. The pathobiological knowledge of PVOD is poor, explaining the absence of medical therapy for PVOD. Lung transplantation remains the only therapy for eligible PVOD patients. As we recently demonstrated, respiratory diseases, chronic obstructive pulmonary disease, or cystic fibrosis exhibit lipointoxication signatures characterized by excessive levels of saturated phospholipids contributing to the pathological features of these diseases, including endoplasmic reticulum stress, pro-inflammatory cytokines production, and bronchoconstriction. In this study, we investigated and compared the clinical data and lung lipid signature of control (10 patients), idiopathic PAH (7 patients), heritable PAH (9 BMPR2 mutations carriers), hPVOD (10 EIF2AK4 mutation carriers), and sPVOD (6 non-carriers) subjects. Mass spectrometry analyses demonstrated lung lipointoxication only in hPVOD patients, characterized by an increased abundance of saturated phosphatidylcholine (PC) at the expense of the polyunsaturated species in the lungs of hPVOD patients. The present data suggest that lipointoxication could be a potential player in the etiology of PVOD.

Patient-specific and gene-corrected induced pluripotent stem cell-derived endothelial cells elucidate single-cell phenotype of pulmonary veno-occlusive disease.

Pulmonary veno-occlusive disease (PVOD) is a rare form of pulmonary hypertension characterized by the preferential remodeling of the pulmonary venules. Hereditary PVOD is caused by biallelic variants of the EIF2AK4 gene. Three PVOD patients who carried the compound heterozygous variants of EIF2AK4 and two healthy controls were recruited and induced pluripotent stem cells (iPSCs) were generated from human peripheral blood mononuclear cells (PBMCs). The EIF2AK4 c.2965C>T variant (PVOD#1), c.3460A>T variant (PVOD#2), and c.4832_4833insAAAG variant (PVOD#3) were corrected by CRISPR-Cas9 in PVOD-iPSCs to generate isogenic controls and gene-corrected-iPSCs (GC-iPSCs). PVOD-iPSC-endothelial cells (ECs) exhibited a decrease in GCN2 protein and mRNA expression when compared with control and GC-ECs. PVOD-ECs exhibited an abnormal EC phenotype featured by excessive proliferation and angiogenesis. The abnormal phenotype of PVOD-ECs was normalized by protein kinase B inhibitors AZD5363 and MK2206. These findings help elucidate the underlying molecular mechanism of PVOD in humans and to identify promising therapeutic drugs for treating the disease.

Lung Transplant Outcomes in Patients with Pulmonary Veno-Occlusive Disease

<h3>Purpose</h3> Pulmonary veno-occlusive disease (PVOD) is a rare cause of pulmonary hypertension. Prognosis of PVOD is worse than PAH. Most patients need lung transplantation. Previous study showed that PVOD patients had higher waitlist mortality compared to PAH patients. To date, there are no study report outcomes of lung transplant in this population. We would like to study the outcome and compare with IPAH patients. <h3>Methods</h3> This is a retrospective observational study. Patients with a diagnosis of PVOD and PAH underwent lung transplant between 2005 and 2018 were identified from SRTR database. Numerical data were reported in mean and standard deviation. Categorical data were reported in count and percent. T-test and Chi-square test were performed to compare variables between 2 groups. Survival was compared using Kaplan-Meier (K-M) method. <h3>Results</h3> 61 PVOD patients and 970 PAH patients underwent lung transplant were identified. There was no significant difference in age and BMI. Patients with PVOD had significant lower post-transplant systolic, diastolic and mean PA pressure and higher cardiac output. LAS at matching were not significantly different. PVOD patients had shorter time on waiting list (152.7±263.34 vs 337.56±511.14, p<0.01). Proportion of patients requiring ECMO post lung transplant were higher in PVOD group (13.11% vs 4.23%, p<0.01). Proportion of patients developing primary graft dysfunction (PGD) were lower in PVOD group (37.5% vs 61.93%, p=0.056). There was no difference of length of stay, FEV1, FVC, PCO2 post lung transplant and acute rejection between 2 groups. Survivals were not different between 2 groups using K-M method (p=0.33). <h3>Conclusion</h3> We found that PVOD patients who underwent lung transplant had shorter waiting time compared to PAH patients which suggest that disease severity of PVOD is higher than PAH. Despite that more PVOD patients required ECMO support post-operative, patient survival and other long-term outcomes such as lung function or rejection were not different between from PAH patients.

Unique wreath-like smooth muscle proliferation of the pulmonary vasculature in pulmonary veno-occlusive disease versus pulmonary arterial hypertension

Pulmonary veno-occlusive disease (PVOD) is a rare but fatal cause of pulmonary hypertension reported to be linked to mutations of eukaryotic initiation factor 2 alpha kinase 4 (EIF2AK4), also known as general control nonderepressible 2 kinase (GCN2). PVOD is difficult to diagnose and often initially misdiagnosed as other types of idiopathic pulmonary arterial hypertension (IPAH). To rapidly and correctly identify PVOD patients and explore the possible pathogenesis, we thoroughly investigated histopathological features and GCN2 protein levels in non-PAH, PVOD and PAH patients. Lung specimens were examined for histopathological changes, including those of pulmonary arteries and veins, by Masson's trichrome, modified Verhoeff's and α-SMA staining in the PVOD, IPAH, and non-PAH groups. GCN2 and α-SMA expression in lung tissue was examined by immunohistochemistry and western blotting. PVOD and IPAH patients showed significant intimal and medial thickening of muscular pulmonary arteries compared with non-PAH patients. PVOD patients had more prominent intimal and medial thickening of muscular pulmonary veins than the other two groups. Interestingly, specialized muscle bundles surrounding the tunica adventitia of the pulmonary artery and vein were observed in PVOD patients. A significant decrease in GCN2 expression in the PVOD group was confirmed by immunohistochemistry and western blotting. Our study is the first to show remarkable histological structures, including the wreath-like arrangement of a hyperplastic muscle bundle in the adventitia of pulmonary arteries, in PVOD patients as a diagnostic clue and to disclose the biological difference between PAH and PVOD in a Taiwanese population.

A NOVEL MUTATION IN A PATIENT WITH PULMONARY VENO-OCCLUSIVE DISEASE MASQUERADING AS PULMONARY ARTERIAL HYPERTENSION

A NOVEL MUTATION IN A PATIENT WITH PULMONARY VENO-OCCLUSIVE DISEASE MASQUERADING AS PULMONARY ARTERIAL HYPERTENSION

Pulmonary vascular remodeling patterns and expression of general control nonderepressible 2 (GCN2) in pulmonary veno-occlusive disease

Heritable pulmonary veno-occlusive disease (PVOD) is linked to mutations in the eukaryotic initiation factor 2 alpha kinase 4 (EIF2AK4) gene, leading to a loss of general control nonderepressible 2 (GCN2). The role of GCN2 expression in pulmonary vascular remodeling remains obscure. We sought to identify specific histologic and biologic features in heritable PVOD. Clinical data and lung histology of 24 PVOD patients (12 EIF2AK4 mutation carriers, 12 non-carriers) were submitted to systematic histologic analysis and semiautomated morphometry. GCN2 expression was quantified by Western blotting in 24 PVOD patients, 44 patients with pulmonary arterial hypertension (PAH; 23 bone morphogenetic protein receptor type II [BMPR2] mutation carriers, 21 non-carriers), and 3 experimental pulmonary hypertension models. PVOD patients showed a significant decrease of pulmonary arterial patency (p < 0.0001) compared with healthy controls. Histology of EIF2AK4 mutation carriers was distinctive from non-carriers regarding (1) arterial remodeling, with significantly more severe intimal fibrosis (p = 0.001), less severe medial hypertrophy (p = 0.001), and (2) stronger muscular hyperplasia of interlobular septal veins (p = 0.002). GCN2 expression was abolished in heritable PVOD (p < 0.0001), but also importantly decreased in sporadic PVOD (p = 0.03) as well as in heritable (p = 0.002) and idiopathic PAH (p = 0.003); moreover, GCN2 was abolished in 2 experimental pulmonary hypertension models and importantly decreased in 1 model (p < 0.0001 for all models). Pulmonary arterial remodeling in PVOD is present to an important extent. A significant decrease of GCN2 expression is a common denominator of all tested groups of PVOD and PAH, including their respective experimental models. Our results underline specific morphologic and biologic similarities between PAH and PVOD and let us consider both conditions rather in one large spectrum of disease than as two distinct and clear-cut entities.

Lung capillary blood volume and membrane diffusion in precapillary pulmonary hypertension

Combined diffusion capacity of the lung for carbon monoxide (DLco) and nitric oxide (DLno) measurements allow for the estimation of pulmonary capillary blood volume (Vc) and alveolar membrane diffusion (Dm). The clinical usefulness of these measurements in pulmonary hypertension (PH) is unclear. Combined DLco and DLno were measured in 290 consecutive patients with precapillary PH (pulmonary arterial hypertension (PAH), n = 153; pulmonary veno-occlusive disease (PVOD), n = 33; and chronic thromboembolic pulmonary hypertension (CTEPH), n = 104). Clinical correlates of Vc and Dm were assessed in a sub-group of PAH patients without comorbidities. PVOD patients compared with PAH and CTEPH patients displayed the lowest values of Vc (29.4 ± 16.8 ml vs 56.3 ± 26.5 ml vs 56.9 ± 26.2 ml, p < 0.01, respectively) and Dm (27.7 ± 11.6 ml/mm Hg/min vs 43.4 ± 14.8 ml/mm Hg/min vs 44.7 ± 17.7 ml/mm Hg/min, p < 0.01, respectively). The DLno/DLco ratio was highest in the PVOD group (5.82 ± 2.04 vs 4.95 ± 1.31 vs 5.16 ± 1.58, p < 0.05). In a sub-set of 69 PAH patients without comorbidities, Vc and Dm correlated significantly with functional capacity (6-minute walking distance, oxygen consumption) and New York Heart Association Functional Classification but not with invasive hemodynamics. Only Dm was significantly associated with survival. On receiver operating characteristic curve analysis, Vc, Dm, and DLno/DLco were not superior to DLco for discriminating PVOD from PAH or CTEPH. PVOD patients display higher values of the DLno/DLco ratio compared with PAH and CTEPH, suggesting proportionally greater reduction in Vc relative to Dm. However, partitioning of diffusion failed to be more clinically relevant than conventional DLco for detection of PVOD.

Genetic counselling in a national referral centre for pulmonary hypertension.

Genetic causes of pulmonary arterial hypertension (PAH) and pulmonary veno-occlusive disease (PVOD) have been identified, leading to a growing need for genetic counselling.Between 2003 and 2014, genetic counselling was offered to 529 PAH and 100 PVOD patients at the French Referral Centre for Pulmonary Hypertension.Mutations in PAH-predisposing genes were identified in 72 patients presenting as sporadic PAH (17% of cases; 62 mutations in BMPR2, nine in ACVRL1 (ALK1) and one in ENG) and in 94 patients with a PAH family history (89% of cases; 89 mutations in BMPR2, three in ACVRL1 (ALK1) and two in KCNK3). Bi-allelic mutations in EIF2AK4 were identified in all patients with a family history of PVOD (n=19) and in seven patients (8.6%) presenting as sporadic PVOD. Pre-symptomatic genetic diagnosis was offered to 272 relatives of heritable PAH patients, identifying mutations in 36.4% of them. A screening programme is now offered to asymptomatic mutation carriers to detect PAH in an early phase and to identify predictors of outcomes in asymptomatic BMPR2 mutation carriers. BMPR2 screening allowed us to offer pre-implantation diagnosis to two couples with a BMPR2 mutation.Genetic counselling can be implemented in pulmonary hypertension centres.

Occupational exposure to organic solvents: a risk factor for pulmonary veno-occlusive disease.

Pulmonary veno-occlusive disease (PVOD) is a rare form of pulmonary hypertension characterised by predominant remodelling of pulmonary venules. Bi-allelic mutations in the eukaryotic translation initiation factor 2α kinase 4 (EIF2AK4) gene were recently described as the major cause of heritable PVOD, but risk factors associated with PVOD remain poorly understood. Occupational exposures have been proposed as a potential risk factor for PVOD, but epidemiological studies are lacking.A case-control study was conducted in consecutive PVOD (cases, n=33) and pulmonary arterial hypertension patients (controls, n=65). Occupational exposure was evaluated via questionnaire interview with blinded assessments using an expert consensus approach and a job exposure matrix (JEM).Using the expert consensus approach, PVOD was significantly associated with occupational exposure to organic solvents (adjusted OR 12.8, 95% CI 2.7-60.8), with trichloroethylene being the main agent implicated (adjusted OR 8.2, 95% CI 1.4-49.4). JEM analysis independently confirmed the association between PVOD and trichloroethylene exposure. Absence of significant trichloroethylene exposure was associated with a younger age of disease (54.8±21.4 years, p=0.037) and a high prevalence of harbouring bi-allelic EIF2AK4 mutations (41.7% versus 0%, p=0.015).Occupational exposure to organic solvents may represent a novel risk factor for PVOD. Genetic background and environmental exposure appear to influence the phenotypic expression of the disease.

Haemosiderin-laden sputum macrophages for diagnosis in pulmonary veno-occlusive disease.

AimsPulmonary veno-occlusive disease (PVOD) is a rare condition of pulmonary arterial hypertension (PAH), in which post-capillary veins are affected. Since the therapeutic approach in PVOD differs from other forms of PAH, it is crucial to establish the diagnosis. Due to the fact that affected patients are often hemodynamically unstable, minimal invasive procedures are necessary for the diagnostic work-up. Chronic alveolar haemorrhage has been observed during bronchoalveolar lavage in PVOD cases. This study therefore investigates whether signs of alveolar haemorrhage can also be found in the sputum of these patients.Methods and ResultsSix patients suffering from PVOD were included in this analysis. As controls, patients with idiopathic PAH (n = 11), chronic thromboembolic PH (n = 9) and with sclerodermia-associated PH (n = 10) were assessed. Sputum from every patient was obtained by a non-invasive manner. The amount of haemosiderin-laden macrophages was determined using the Golde score. There were statistically significant more haemosiderin-laden macrophages in the sputum of patients suffering from PVOD as compared to the other groups (P<0.05). Assuming a cut-off of 200 on the Golde score, all of the 6 PVOD patients surpassed this value compared with only 1 out of the 30 cases with precapillary PH. Thus, sensitivity and specificity with respect to the diagnosis of PVOD was 100% and 97%, respectively.ConclusionThe content of haemosiderin-laden macrophages in the sputum of patients suffering from PVOD is significantly higher as compared to other forms of PH and may be useful in the non-invasive diagnostic work-up of these patients.

Ventilation/perfusion lung scan in pulmonary veno-occlusive disease

Pulmonary veno-occlusive disease (PVOD), a rare form of pulmonary arterial hypertension (PAH), requires histological proof for definitive diagnosis; however, lung biopsy is not recommended in PAH. Recent conjoint European Respiratory Society/European Society of Cardiology guidelines suggest that nonmatched perfusion defects on ventilation/perfusion (V'/Q') lung scanning in PAH patients may suggest PVOD. The aim of our study was to evaluate V'/Q' lung scans in a large cohort of PVOD and idiopathic or heritable PAH patients. V'/Q' lung scans from 70 patients with idiopathic or heritable PAH and 56 patients with confirmed or highly probable PVOD were reviewed in a double-blind manner. The vast majority of V'/Q' lung scans were normal or without significant abnormalities in both groups. No differences in ventilation or perfusion lung scans were observed between PAH and PVOD patients (all p>0.05). Furthermore, no differences were observed between confirmed (n=31) or highly probable PVOD (n=25). Nonmatched perfusion defects were found in seven (10%) idiopathic PAH patients and four (7.1%) PVOD patients (p>0.05). Nonmatched perfusion defects were rarely seen in a large cohort of idiopathic or heritable PAH and PVOD patients. Future recommendations should be amended according to these results suggesting that V'/Q' lung scanning is not useful in discriminating PVOD from idiopathic PAH.

Platelet-derived growth factor receptor-β and epidermal growth factor receptor in pulmonary vasculature of systemic sclerosis-associated pulmonary arterial hypertension versus idiopathic pulmonary arterial hypertension and pulmonary veno-occlusive disease: a case-control study

IntroductionSystemic sclerosis (SSc) complicated by pulmonary arterial hypertension (PAH) carries a poor prognosis, despite pulmonary vascular dilating therapy. Platelet-derived growth factor receptor-β (PDGFR-β) and epidermal growth factor receptor (EGFR) are potential therapeutic targets for PAH because of their proliferative effects on vessel remodelling. To explore their role in SScPAH, we compared PDGFR- and EGFR-mmunoreactivity in lung tissue specimens from SScPAH. We compared staining patterns with idiopathic PAH (IPAH) and pulmonary veno-occlusive disease (PVOD), as SScPAH vasculopathy differs from IPAH and sometimes displays features of PVOD. Immunoreactivity patterns of phosphorylated PDGFR-β (pPDGFR-β) and the ligand PDGF-B were evaluated to provide more insight into the patterns of PDGFR-b activation.MethodsLung tissue specimens from five SScPAH, nine IPAH, six PVOD patients and five controls were examined. Immunoreactivity was scored for presence, distribution and intensity.ResultsAll SScPAH and three of nine IPAH cases (P = 0.03) showed PDGFR-β-immunoreactivity in small vessels (arterioles/venules); of five SScPAH vs. two of nine IPAH cases (P = 0.02) showed venous immunoreactivity. In small vessels, intensity was stronger in SScPAH vs. IPAH. No differences were found between SScPAH and PVOD. One of five normal controls demonstrated focally mild immunoreactivity. There were no differences in PDGF-ligand and pPDGFR-b-immunoreactivity between patient groups; however, pPDGFR-b-immunoreactivity tended to be more prevalent in SScPAH small vasculature compared to IPAH. Vascular EGFR-immunoreactivity was limited to arterial and arteriolar walls, without differences between groups. No immunoreactivity was observed in vasculature of normals.ConclusionsPDGFR-β-immunoreactivity in SScPAH is more common and intense in small- and post-capillary vessels than in IPAH and does not differ from PVOD, fitting in with histomorphological distribution of vasculopathy. PDGFR-β immunoreactivity pattern is not paralleled by pPDGFR-β or PDGF-B patterns. PDGFR-β- and EGFR-immunoreactivity of pulmonary vessels distinguishes PAH patients from controls.

Goal-oriented therapy in pulmonary veno-occlusive disease: a word of caution

To the Editors : The evidence for using pulmonary arterial hypertension (PAH) therapies such as prostacyclin derivatives, endothelin receptor antagonists and type-5 phosphodiesterase inhibitors in pulmonary veno-occlusive disease (PVOD) is modest and conflicting 1, 2. Indeed, despite several reports of clinical deterioration and life-threatening pulmonary oedema in PVOD patients receiving PAH therapies, we have recently shown in the European Respiratory Journal that cautious use of continuous intravenous epoprostenol alone or in combination with endothelin receptor antagonists may be useful as a bridge therapy to lung transplantation 2. The term “goal-oriented therapy” describes a relatively novel therapeutic approach in the field of PAH, which focuses on the question of when a response to therapy can be considered sufficient and when it cannot 3. This question is of fundamental importance in guiding therapeutic decisions: that is, when to maintain a therapy, when to switch from one medication to another and when to combine several medications. As an inadequate response to first-line PAH medical treatments is frequently observed in PVOD patients 1, it is likely that a significant proportion of patients showing insufficient response to first-line PAH therapy could be candidates for sequential add-on combination therapy and that such a strategy might increase the risk of developing pulmonary oedema. This eventuality may be more likely in scleroderma patients, who are prone to present with significant pulmonary venous involvement 4. We report a case of …

Cautious epoprostenol therapy is a safe bridge to lung transplantation in pulmonary veno-occlusive disease

Pulmonary veno-occlusive disease (PVOD) carries a poor prognosis and lung transplantation is the only curative treatment. In PVOD, epoprostenol therapy is controversial, as this condition may be refractory to specific therapy with an increased risk of pulmonary oedema. We retrospectively reviewed clinical, functional and haemodynamic data of 12 patients with PVOD (10 with histological confirmation) treated with continuous intravenous epoprostenol and priority listed for lung transplantation after January 1, 2003. All PVOD patients had severe clinical, functional and haemodynamic impairment at presentation. Epoprostenol was used at low dose ranges with slow dose increases and high dose diuretics. Only one patient developed mild reversible pulmonary oedema. After 3-4 months, improvements were seen in the New York Heart Association functional class (class IV to III in seven patients), cardiac index (1.99+/-0.68 to 2.94+/-0.89 L x min(-1) x m(-2)) and indexed pulmonary vascular resistance (28.4+/-8.4 to 17+/-5.2 Wood units x m(-2); all p<0.01). A nonsignificant improvement in the 6-min walk distance was also observed (+41 m, p = 0.11). Two patients died, one patient was alive on the transplantation waiting list on December 1, 2008 and nine patients were transplanted. Cautious use of continuous intravenous epoprostenol improved clinical and haemodynamic parameters in PVOD patients at 3-4 months without commonly causing pulmonary oedema, and may be a useful bridge to urgent lung transplantation.

Failure of Medical Therapy in Pulmonary Arterial Hypertension: Is There an Alternative Diagnosis?

Despite the development of targeted therapies for pulmonary arterial hypertension (PAH), some patients fail to respond to medical therapy. There are a number of types of PAH, one of which is pulmonary venoocclusive disease (PVOD). Unlike other PAH types, the hallmark pathology of PVOD is fibrous occlusion of the small venules, potentially with arterial involvement. It was hypothesized that a lack of response to medical therapy in clinically diagnosed PAH can be explained by misdiagnosed PVOD. This study reviewed cases of 14 patients with clinically diagnosed PAH who had failed to respond to medical therapy and had lung tissue available from autopsy or explant. Control samples (n = 6) were obtained from lungs explanted for other causes, and a previous transthoracic echocardiogram excluded pulmonary hypertension. Comprehensive vessel morphometry was performed, and the clinical data reviewed. Vessel analysis confirmed 86% of case patients had PVOD and 14% had arterial-only PAH (artPAH). In the PVOD case patients, significant pathology was present in all vessel types with similar obstructive, intimal fibrosis in the venules (p < 0.0001) and arterioles (p < 0.0001). This was considerably different from the intimal concentric laminar smooth muscle proliferation in the artPAH cases. There were no significant differences in clinical presentation between PVOD and artPAH case patients. Pulmonary edema was not observed in the PVOD cases. PVOD is an underdiagnosed and commonly misdiagnosed cause of pulmonary hypertension, which may present with a failure to respond to medical therapy. Further studies on PVOD may help confirm whether a change in its classification as a type of PAH is necessary.

Pulmonary veno-occlusive disease

Pulmonary veno-occlusive disease (PVOD) is currently classified as a subgroup of pulmonary arterial hypertension (PAH) and accounts for 5-10% of cases initially considered to be idiopathic PAH. PVOD has been described as idiopathic or complicating other conditions, including connective tissue diseases, HIV infection, bone marrow transplantation, sarcoidosis and pulmonary Langerhans cell granulomatosis. PVOD shares broadly similar clinical presentation, genetic background and haemodynamic characteristics with PAH. Compared to PAH, PVOD is characterised by a higher male/female ratio, higher tobacco exposure, lower arterial oxygen tension at rest, lower diffusing capacity of the lung for carbon monoxide, and lower oxygen saturation nadir during the 6-min walk test. High-resolution computed tomography (HRCT) of the chest can be suggestive of PVOD in the presence of centrilobular ground-glass opacities, septal lines and lymph node enlargement. Similarly, occult alveolar haemorrhage is associated with PVOD. A noninvasive diagnostic approach using HRCT of the chest, arterial blood gases, pulmonary function tests and bronchoalveolar lavage could be helpful for the detection of PVOD patients and in avoiding high-risk surgical lung biopsy for histological confirmation. PVOD is characterised by a poor prognosis and the possibility of developing severe pulmonary oedema with specific PAH therapy. Lung transplantation is the treatment of choice. Cautious use of specific PAH therapy can, however, be helpful in some patients.

Pulmonary Veno-Occlusive Disease

Pulmonary veno-occlusive disease (PVOD) is defined by specific pathologic changes of the pulmonary veins. A definite diagnosis of PVOD thus requires a lung biopsy or pathologic examination of pulmonary explants or postmortem lung samples. However, lung biopsy is hazardous in patients with severe pulmonary hypertension, and there is a need for noninvasive diagnostic tools in this patient population. Patients with PVOD may be refractory to pulmonary arterial hypertension (PAH)-specific therapy and may even deteriorate with it. It is important to identify such patients as soon as possible, because they should be treated cautiously and considered for lung transplantation if eligible. High-resolution computed tomography of the chest can suggest PVOD in the setting of pulmonary hypertension when it shows nodular ground-glass opacities, septal lines, lymph node enlargement, and pleural effusion. Similarly, occult alveolar hemorrhage found on bronchoalveolar lavage in patients with pulmonary hypertension is associated with PVOD. We conducted the current study to identify additional clinical, functional, and hemodynamic characteristics of PVOD. We retrospectively reviewed 48 cases of severe pulmonary hypertension: 24 patients with histologic evidence of PVOD and 24 randomly selected patients with idiopathic, familial, or anorexigen-associated PAH and no evidence of PVOD after meticulous lung pathologic evaluation. We compared clinical and radiologic findings, pulmonary function, and hemodynamics at presentation, as well as outcomes after the initiation of PAH therapy in both groups. Compared to PAH, PVOD was characterized by a higher male:female ratio and higher tobacco exposure (p < 0.01). Clinical presentation was similar except for a lower body mass index (p < 0.02) in patients with PVOD. At baseline, PVOD patients had significantly lower partial pressure of arterial oxygen (PaO2), diffusing lung capacity of carbon monoxide/alveolar volume (DLCO/VA), and oxygen saturation nadir during the 6-minute walk test (all p < 0.01). Hemodynamic parameters showed a lower mean systemic arterial pressure (p < 0.01) and right atrial pressure (p < 0.05), but no difference in pulmonary capillary wedge pressure. Four bone morphogenetic protein receptor II (BMPR2) mutations have been previously described in PVOD patients; in the current study we describe 2 additional cases of BMPR2 mutation in PVOD. Computed tomography of the chest revealed nodular and ground-glass opacities, septal lines, and lymph node enlargement more frequently in patients with PVOD compared with patients with PAH (all p < 0.05). Among the 16 PVOD patients who received PAH-specific therapy, 7 (43.8%) developed pulmonary edema (mostly with continuous intravenous epoprostenol, but also with oral bosentan and oral calcium channel blockers) at a median of 9 days after treatment initiation. Acute vasodilator testing with nitric oxide and clinical, functional, or hemodynamic characteristics were not predictive of the subsequent occurrence of pulmonary edema on treatment. Clinical outcomes of PVOD patients were worse than those of PAH patients.