Outcomes of hospitalisation for right heart failure in pulmonary arterial hypertension.

The aim of this study was to examine the causes and outcomes of hospitalisation in patients with pulmonary arterial hypertension (PAH). 205 consecutive hospitalisations occurring between 2000 and 2009 in 90 PAH patients were studied. The leading causes for hospitalisation were right heart failure (RHF; 56%), infection (16%) and bleeding disorders (8%). For patients with RHF, in-hospital mortality was 14% overall, 46% for patients receiving inotropes and 48% for those admitted to the intensive care unit. The predictors for in-hospital mortality were the presence of connective tissue disease (CTD) (OR 4.92), systolic blood pressure <100 mmHg (OR 4.32) and Na ≤ 136 mEq · L(-1) (OR 4.29). Mortality after discharge was 13, 26 and 35% at 3, 6 and 12 months, respectively. World Health Organization functional class prior to admission, renal dysfunction, Charlson comorbidity index, and the presence of CTD were all predictors of mortality after discharge. Hyponatraemia and low systolic blood pressure upon admission and underlying CTD are the main prognostic factors for in-hospital mortality in patients with PAH admitted for RHF. The short-term outcomes after discharge are poor and remarkably worse in patients with underlying CTD or renal impairment. Early recognition of these factors may guide decisions regarding more aggressive therapy, including consideration for lung transplantation.

Disproportionate elevation of N-terminal pro-brain natriuretic peptide in scleroderma-related pulmonary hypertension.

N-terminal pro-brain natriuretic peptide (NT-proBNP) is a marker of neurohormonal activation that is useful in the diagnosis and prognosis of various forms of pulmonary arterial hypertension (PAH). We sought to characterise and compare NT-proBNP in a cohort of PAH related to systemic sclerosis (PAH-SSc) and idiopathic PAH (IPAH) patients. NT-proBNP levels, collected from PAH-SSc and IPAH patients followed prospectively, were compared and correlated with haemodynamic variables. Cox proportional hazard models were created to assess the predictive value of NT-proBNP. 98 patients (55 PAH-SSc, 43 IPAH) were included. Haemodynamics were similar, except for lower mean pulmonary arterial pressure in PAH-SSc. NT-proBNP levels were significantly higher in PAH-SSc (3,419+/-3,784 versus 1,393+/-1,633 pg x mL(-1); p<0.01) and were more closely related to haemodynamics in PAH-SSc than IPAH. 28 patients died. NT-proBNP predicted survival (hazard ratio (HR) 3.18; p<0.01) in the overall cohort; however, when stratified by group, predicted survival only in PAH-SSc (HR 3.07, p<0.01 versus 2.02, p = 0.29 in IPAH). This is the first description showing NT-proBNP levels are 1) significantly higher in PAH-SSc than IPAH despite less severe haemodynamic perturbations, and 2) stronger predictors of survival in PAH-SSc, suggesting that neurohormonal regulation may differ between PAH-SSc and IPAH. Future studies to define pertinent mechanisms are warranted.

Regulation of bovine endothelial constitutive nitric oxide synthase by oxygen.

Oxygen (O2) may regulate pulmonary vascular resistance through changes in endothelial nitric oxide (NO) production. To determine whether constitutive NO synthase (cNOS) is regulated by O2, we assessed cNOS expression and activity in bovine pulmonary artery endothelial cells exposed to different concentrations of O2. In a time-dependent manner, changes in O2 concentration from 95 to 3% produced a progressive decrease in cNOS mRNA and protein levels resulting in 4.8- and 4.3-fold reductions after 24h, respectively. This correlated with changes in cNOS activity as determined by nitrite measurements. Compared with 20% O2, cNOS activity was increased 1.5-fold in 95% O2 and decreased 1.9-fold in 3% O2. A decrease in O2 concentration from 94 to 3% shortened cNOS mRNA half-life from 46 to 24 h and caused a 20-fold repression of cNOS gene transcription. Treatment with cycloheximide produced a threefold increase in cNOS mRNA at all O2 concentrations, suggesting that cNOS mRNA expression is negatively regulated under basal condition. We conclude that O2 upregulates cNOS expression through transcriptional and post-transcriptional mechanisms. A decrease in cNOS activity in the presence of low O2 levels, therefore, may contribute to hypoxia-induced vasoconstriction in the pulmonary circulation.

Erythema induratum and active pulmonary tuberculosis.

The etiology of erythema induratum, a rare disease of the skin in the United States but occasionally seen in natives of Asian countries, remains a source of debate. Its association with tuberculosis, although strongly suspected for more than one century, has not been clearly defined. We report a case of erythema induratum occurring in a young Chinese woman in the setting of active pulmonary tuberculosis. Both diseases promptly responded to antituberculous therapy. The diagnosis of erythema induratum should urge the clinician to search for a source of active tuberculosis, and treatment should be initiated accordingly.

Bilateral diaphragm paralysis secondary to central von Recklinghausen's disease.

Bilateral paralysis of the diaphragm is either idiopathic or associated with several medical conditions, including trauma or thoracic surgery, viral infections, and neurologic congenital or degenerative disorders. We describe the case of a 36-year-old man with a history of neurofibromatosis who developed severe bilateral diaphragmatic paralysis from involvement of the phrenic nerve roots with neurofibromas. The patient manifested progressive exertional dyspnea and debilitating orthopnea requiring the use of noninvasive mechanical ventilation at night. A review of the literature reveals that neurofibromatosis is an unrecognized cause of diaphragmatic paralysis.

Acute and chronic hypoxic pulmonary hypertension in guinea pigs.

To determine whether the strength of acute hypoxic vasoconstriction predicts the magnitude of chronic hypoxic pulmonary hypertension, we performed serial studies on guinea pigs. Unanesthetized, chronically catheterized guinea pigs increased mean pulmonary arterial pressure (PAP) from 11 +/- 0.5 to 13 +/- 0.7 Torr in acute hypoxia (10% O2 for 65 min). The response was maximal at 5 min, remained stable for 1 h, and was reversible on return to room air. Cardiac index did not change with acute hypoxia or recovery. Guinea pigs exposed to chronic hypoxia increased PAP, measured in room air 1 h after removal from the hypoxic chamber, to 18 +/- 1 Torr by 5 days with little further increase in PAP to 20 +/- 1 Torr after 21 days. Cardiac index fell from 273 +/- 12 to 206 +/- 7 ml.kg-1.min-1 (P less than 0.05) after 21 days of hypoxia. Medial thickness of pulmonary arteries adjacent to terminal bronchioles and alveolar ducts increased significantly by 10 days. The magnitude of the pulmonary vasoconstriction to acute hypoxia persisted and was unabated during the development and apparent stabilization of chronic hypoxic pulmonary hypertension, suggesting that if vasoconstriction is the stimulus for remodeling, then the importance of the stimulus lessens with duration of hypoxia. In individual animals followed serially, we found no correlation between the magnitude of the acute vasoconstrictor response before chronic hypoxia and the severity of chronic pulmonary hypertension that subsequently developed either because the initial response was small and variable or because vasoconstriction may not be the sole stimulus for vascular remodeling in the guinea pig.

Management of venous thromboembolic disease in the chronically critically ill patient.

Although PE is the most common preventable cause of death among U.S. hospital patients, proper treatment of thromboembolism and adequate prophylaxis in high-risk patients have been shown to be effective in saving lives. Because clinical symptoms and signs of thromboembolic disease are often nonspecific, early diagnosis and treatment rely on the capacity of physicians to adequately identify a patient at risk, choose the appropriate diagnostic modalities in a cost-effective fashion, and promptly initiate treatment. The diagnosis of VTE is particularly challenging in patients who are in the post acute period of a complex medical or surgical illness. Avenues that need to be further explored include various diagnostic tests such as spiral CT, MR imaging, and transesophageal echocardiography, which are less invasive than the present gold standard of pulmonary angiography. Also needed are better clinical data regarding the optimal choice of preventive therapy (e.g., unfragmented heparin or LMWH or mechanical devices) and clinical outcome of such therapy in patients with prolonged illness.

Estimating pulmonary artery pressures by echocardiography in patients with emphysema.

In patients with emphysema being evaluated for lung volume reduction surgery, Doppler echocardiography has been used to screen for pulmonary hypertension as an indicator of increased peri-operative risk. To determine the accuracy of this test, the present authors compared the results of right heart catheterisations and Doppler echocardiograms in 163 patients participating in the cardiovascular substudy of the National Emphysema Treatment Trial. Substudy patients had both catheterisation and Doppler echocardiography performed before and after randomisation. In 74 paired catheterisations and echocardiograms carried out on 63 patients, the mean values of invasively measured pulmonary artery systolic pressures and the estimated right ventricular systolic pressures were similar. However, using the World Health Organization's definitions of pulmonary hypertension, echocardiography had a sensitivity of 60%, specificity of 74%, positive predictive value of 68% and a negative predictive value of 67% compared with the invasive measurement. Bland-Altman analysis revealed a bias of 0.37 kPa with 95% limits of agreement from -2.5-3.2 kPa. In patients with severe emphysema, echocardiographic estimates of pulmonary artery pressures correlate very weakly with right heart catheterisations, and the test characteristics (e.g. sensitivity, specificity, etc.) of echocardiographic assessments are poor.

Addition of sildenafil to bosentan monotherapy in pulmonary arterial hypertension.

Combination therapy has been recommended for the treatment of pulmonary arterial hypertension (PAH). However, there is scant information on combination therapy after failure of monotherapy, particularly in patients with scleroderma-associated PAH (PAH-SSD). From a group of 82 consecutive patients with PAH who received initial bosentan monotherapy, a total of 13 idiopathic PAH (IPAH) and 12 PAH-SSD patients requiring additional therapy with sildenafil were studied. Sildenafil was added for clinical deterioration based upon symptoms, New York Heart Association (NYHA) classification or 6-min walk distance (6MWD). Clinical data and haemodynamics were collected at baseline. Assessments were made at 1-3-month intervals. At baseline, there were no differences in demographics, NYHA classification, haemodynamics or 6MWD between the two groups. After initiation of bosentan, both groups experienced clinical improvement but ultimately deteriorated (median time to monotherapy failure 792 versus 458 days for IPAH and PAH-SSD patients, respectively). After addition of sildenafil, more IPAH patients tended to improve in NYHA class (five out of 13 versus two out of 12) and walked further (mean difference in 6MWD 47+/-77 m versus -7+/-40 m) compared with PAH-SSD patients. In conclusion, addition of sildenafil after bosentan monotherapy failure improved New York Heart Association class and 6-min walk distance in idiopathic pulmonary arterial hypertension patients but failed to improve either parameter in scleroderma-associated pulmonary arterial hypertension patients. Additional studies are needed to assess the tolerability and efficacy of this combination in patients with scleroderma-associated pulmonary arterial hypertension.

Partial reversal of hypoxic pulmonary hypertension by heparin.

Chronic hypoxia produces pulmonary hypertension and an increase in medial thickness of pulmonary arteries that reach maximal values after 10 days of hypoxia. We previously showed that heparin given during the first 10 days of hypoxia reduced the development of both pulmonary hypertension and vascular remodeling in the guinea pig. To determine if heparin could reverse established hypoxic pulmonary hypertension and vascular remodeling, we administered heparin by continuous subcutaneous infusion (20 U/kg/h) for the last 7 days of a 21-day exposure to hypoxia (10% O2, balance N2) and compared these animals with normal saline-infused hypoxic control and room air-exposed animals. Hypoxia increased pulmonary artery pressure from 11 +/- 1 mm Hg (mean +/- SEM) in room air animals to 20 +/- 2 mm Hg (p less than 0.05) in saline-treated hypoxic control animals. Heparin reduced pulmonary artery pressure to 16 +/- 1 mm Hg (p less than 0.05 versus hypoxic control and room air control animals). Total pulmonary resistance (TPR) increased with hypoxia from 0.043 +/- 0.003 mm Hg x min x kg-1 x ml-1 in room air to 0.090 +/- 0.004 in hypoxia (p less than 0.05), and in the rise in TPR was also partially reversed by heparin to 0.068 +/- 0.0003 (p less than 0.05). The percentage of medial thickness of alveolar duct arteries increased from 5.8 +/- 0.6% in room air to 9.5 +/- 0.1% (p less than 0.05) after 3 wk of hypoxia, and heparin therapy partially reversed the increase in medial thickness to 7.2 +/- 0.7% (p less than 0.05 versus both hypoxia control and room air).(ABSTRACT TRUNCATED AT 250 WORDS)

Hypoxia stimulates the release by bovine pulmonary artery endothelial cells of an inhibitor of pulmonary artery smooth muscle cell growth.

The proliferation of smooth muscle cells (SMC) seen in hypoxic pulmonary hypertension is a poorly understood phenomenon but may involve endothelial cell (EC)-SMC interaction. Using bovine pulmonary artery cells, we examined the effect of O2 tension and the role of EC or media conditioned by EC (ECCM) on SMC proliferation. We found no difference in SMC proliferation under 3%, 10%, and 20% O2. EC, co-cultured with SMC in 3% O2, inhibited SMC proliferation consistently by about 40% (versus SMC exposed to hypoxia but not to EC). In normoxia, the degree of inhibition was dependent on EC:SMC ratio. In separate experiments, media from EC exposed to 3% or 20% O2 had a mitogenic activity of 24% and 42%, respectively (compared to 100% mitogenic activity with 5% FCS), on serum-deprived SMC. On the other hand, when SMC were stimulated to grow with FCS, an inhibitory activity (IA) from ECCM on SMC proliferation was observed and was significantly greater in hypoxic versus normoxic ECCM (40% versus 21%, respectively). Amicon concentration showed that the IA was contained in the less than 10 kD fraction of ECCM. Preliminary characterization of this IA indicates that it is unlike any of the known inhibitors of SMC growth, such as lactic acid, prostaglandin derivatives, or heparan sulfate. We conclude that hypoxia causes pulmonary artery EC to release a unique inhibitor of SMC growth.

Effect of heparin and warfarin on chronic hypoxic pulmonary hypertension and vascular remodeling in the guinea pig.

Chronic hypoxia produces pulmonary hypertension and pulmonary vascular remodeling. Heparin partially prevents the rise in right ventricular pressure and vascular remodeling in chronically hypoxic mice. To determine if this is due to the anticoagulant property of heparin or another property, we compared the effect of oral warfarin given at an anticoagulating dose (0.5 mg/kg/day) to heparin given by continuous infusion at a dose that does not prolong the partial thromboplastin time (PTT) (20 units/kg/h) on hypoxic pulmonary hypertension and vascular remodeling in the guinea pig. Normoxic control animals either untreated or treated with heparin or Coumadin were all alike in blood gases, pulmonary vascular resistance, right heart weights, and pulmonary histology. Hypoxia (10% 0(2) for 10 days) induced similar and significant increases in mean pulmonary artery (PA) pressure in both the hypoxic control and warfarin groups (19 +/- 1 mm Hg (mean +/- SEM) in both groups versus 11 +/- 0.1 mm Hg in the normoxic control group; p less than 0.05). Total pulmonary vascular resistance (TPR) was also increased from 0.041 +/- 0.002 in the normoxic control group to 0.087 +/- 0.007 and 0.071 +/- 0.003 mm Hg/ml/min/kg in the hypoxic control and warfarin groups, respectively (p less than 0.05). Whereas anticoagulation with warfarin did not protect the guinea pig from developing pulmonary hypertension, heparin markedly reduced PA and TPR (15 +/- 1 mm Hg and 0.052 +/- 0.002 mm Hg/ml/min/kg, respectively; p less than 0.05 versus hypoxic control or warfarin).(ABSTRACT TRUNCATED AT 250 WORDS)

Prostaglandins E1 and E2 stimulate the proliferation of pulmonary artery smooth muscle cells.

Prostaglandins E1 and E2 are thought to be inhibitors of the growth of systemic vascular smooth muscle cells (SMC). However, their effect on the proliferation of SMC from the pulmonary artery (PA) has not been described and was the subject of this investigation. Cultures of bovine PA SMC were exposed to PGE1 and PGE2 under various conditions and their growth was assessed. PGE1 and PGE2 did not inhibit the growth of PA SMC in 10% fetal calf serum (FCS), but instead caused a dose dependent (10 ng - 1 microgram/ml) increase in [3H]-thymidine incorporation when added to cultures containing 0.5% FCS; the highest doses resulted in 95% and 75% increases in [3H]-thymidine uptake at 24 hours with PGE1 and PGE2 respectively. This was accompanied by a modest increase in actual cell numbers (e.g., 20% with 1 microgram/ml PGE1). Furthermore, PGE1 could mimic insulin-like growth factor (IGF-1) by potentiating the stimulation of SMC growth by fibroblast growth factor, suggesting that PGE1 may act as a progression factor in the growth cycle of these cells. There was, however, no effect of PGE1 on the proliferation of bovine aortic SMC. We conclude that, contrary to most reported effects on systemic SMC, PGE1 and PGE2 do not inhibit the proliferation of PA SMC but rather stimulate it.

Determination of xanthine dehydrogenase mRNA by a reverse transcription-coupled competitive quantitative polymerase chain reaction assay: regulation in rat endothelial cells by hypoxia and hyperoxia.

The enzyme system xanthine dehydrogenase (XD):xanthine oxidase, which generates the superoxide anion as a by-product of action on endogenous substrates, is believed to play a role in mediating pathophysiological changes through its contribution to total superoxide production. To aid with analysis of factors that regulate XD, we have developed a reverse transcription (RT)-coupled competitive quantitative polymerase chain reaction (PCR) assay which enables XD mRNA to be determined from small amounts of cultured cells where constitutive XD levels are low. A homologous insertion mutant of wild-type XD cDNA was prepared and used as an internal standard to normalize intersample PCR efficiency differences. XD mRNA levels determined by RT-PCR also were normalized to tubulin mRNA to compensate for RT differences and loading effects among samples. We report that XD mRNA levels, determined by RT-PCR, were increased twofold in hypoxic (3% oxygen) rat pulmonary microvascular endothelial cells relative to normoxic controls (20% oxygen). Conversely, XD mRNA was decreased threefold within 24 h under hyperoxic (95% oxygen) conditions. These data support the hypothesis that XD is regulated by oxygen tension in the pulmonary vasculature.

Intracellular generation of reactive oxygen species in endothelial cells exposed to anoxia-reoxygenation.

Reactive oxygen species (ROS) play an important role in the pathogenesis of ischemia-reperfusion injury. Extracellular H2O2 generation from bovine pulmonary artery endothelial cells (EC) is known to increase in response to anoxia-reoxygenation (A-R). To determine potential sources of intracellular ROS formation in EC in response to A-R, a fluorometric assay based on the oxidation of 2',7'-dichlorofluorescin was used. Intracellular ROS production declined 40% during 6 h of anoxia (P < 0.05). After A-R, the rates of intracellular ROS formation increased to 148 +/- 9% (P < 0.001) that of normoxic EC (100 +/- 3%). In EC exposed to A-R, allopurinol and NG-methyl-L-arginine (L-NMMA), inhibitors of xanthine oxidase (XO) and nitric oxide synthase (NOS), respectively, reduced intracellular ROS formation by 25 +/- 1% (P < 0.001) and 36 +/- 4% (P < 0.01). Furthermore, at low doses (i.e., 20 microM), deferoxamine and diethylenetriaminepentaacetic acid (DTPA) significantly inhibited intracellular ROS formation. However, at 100 microM, only deferoxamine caused further reduction in DCF fluorescence. In summary, EC respond to A-R by generating increased amounts of XO- and NOS-derived intracellular ROS. The inhibition, to a similar extent, caused by allopurinol and L-NMMA, as well as the effect of deferoxamine and DTPA suggest that the ROS detected is peroxynitrite. Based on these findings and previous work, we conclude that EC generate ROS in response to A-R from at least two different sources: a plasma membrane-bound NADPH oxidase-like enzyme that releases H2O2 extracellularly and XO, which generates intracellular O2-, which in turn may react with nitric oxide to form peroxynitrite.

Phosphorylation of xanthine dehydrogenase/oxidase in hypoxia.

The enzyme xanthine oxidase (XO) has been implicated in the pathogenesis of several disease processes, such as ischemia-reperfusion injury, because of its ability to generate reactive oxygen species. The expression of XO and its precursor xanthine dehydrogenase (XDH) is regulated at pre- and posttranslational levels by agents such as lipopolysaccharide and hypoxia. Posttranslational modification of the protein, for example through thiol oxidation or proteolysis, has been shown to be important in converting XDH to XO. The possibility of posttranslational modification of XDH/XO through phosphorylation has not been adequately investigated in mammalian cells, and studies have reported conflicting results. The present report demonstrates that XDH/XO is phosphorylated in rat pulmonary microvascular endothelial cells (RPMEC) and that phosphorylation is greatly increased ( approximately 50-fold) in response to acute hypoxia (4 h). XDH/XO phosphorylation appears to be mediated, at least in part, by casein kinase II and p38 kinase as inhibitors of these kinases partially prevent XDH/XO phosphorylation. In addition, the results indicate that p38 kinase, a stress-activated kinase, becomes activated in response to hypoxia (an approximately 4-fold increase after 1 h of exposure of RPMEC to hypoxia) further supporting a role for this kinase in hypoxia-stimulated XDH/XO phosphorylation. Finally, hypoxia-induced XDH/XO phosphorylation is accompanied by a 2-fold increase in XDH/XO activity, which is prevented by inhibitors of phosphorylation. In summary, this study shows that XDH/XO is phosphorylated in hypoxic RPMEC through a mechanism involving p38 kinase and casein kinase II and that phosphorylation is necessary for hypoxia-induced enzymatic activation.

Acute respiratory distress syndrome complicating Plasmodium vivax malaria.

Malaria is one of the most common infectious diseases in the world, and severe respiratory complications have been described mainly in association with Plasmodium falciparum. We describe a case of acute respiratory distress syndrome complicating infection with P. vivax in the setting of relatively low parasitemia in a 47-yr-old woman after a brief trip to Papua New Guinea. A review of the literature shows that pulmonary complications of P. vivax are rare but occur more frequently than generally acknowledged. Pathogenic mechanisms of these complications are discussed.

Enhanced rate of H2O2 release from bovine pulmonary artery endothelial cells induced by TGF-beta 1.

We have previously reported that transforming growth factor-beta 1 (TGF-beta 1) produces a "prooxidant" effect on cultured bovine pulmonary artery endothelial cells (BPAEC) [S. K. Das and B. L. Fanburg. Am. J. Physiol. 261 (Lung Cell. Mol. Physiol. 5): L249-L254, 1991]. This effect was found to be associated with a lowering of total cellular GSH (A.C. White, S. K. Das, and B.L. Fanburg. Am. J. Respir. Cell Mol. Biol. 6: 364-368, 1992). In this study, we demonstrate a twofold increase in the rate of extracellular H2O2 release from BPAEC after a 72-h exposure to TGF-beta 1 (2 ng/ml, added at times 0 and 48 h). Increasing and decreasing the levels of cellular GSH with diethylmaleate (DEM, 0.05 mM) and buthionine sulfoximine (BSO, 0.01 mM), respectively, did not affect the rate of TGF-beta 1-induced increase in H2O2 release when compared with the individual effects of these reagents on control cells. The addition of BSO (0.01 mM) to control cells failed to demonstrate an increase in the rate of H2O2 release, despite a more profound decrease in cellular GSH by these cells than detected in cells treated with TGF-beta 1 alone. Moreover, a single dose of TGF-beta 1 (2 ng/ml) induced a 63-85% increase in the rate of H2O2 release within 16 h of exposure, well before the previously demonstrated lowering of cellular GSH. These results indicate that the increase in H2O2 production by TGF-beta 1-stimulated BPAEC is associated with, but does not appear to be the result of, a lowering of cellular GSH. This study further suggests that the TGF-beta 1-induced H2O2 production occurs at a site inaccessible to detoxification by GSH.