Pulmonary vascular complications of liver disease

Hepatopulmonary syndrome and portopulmonary hypertension are two pulmonary vascular complications of liver disease. The pathophysiology underlying each disorder is distinct, but patients with either condition may be limited by dyspnea. A careful evaluation of concomitant symptoms, the physical examination, pulmonary function testing and arterial blood gas analysis, and echocardiographic, imaging, and hemodynamic studies is crucial to establishing (and distinguishing) these diagnoses. Our understanding of the pathobiology, natural history, and treatment of these disorders has advanced considerably over the past decade; however, the presence of either still increases the risk of morbidity and mortality in patients with underlying liver disease. There is no effective medical treatment for hepatopulmonary syndrome. Although liver transplantation can resolve hepatopulmonary syndrome, there appears to be worse survival even with transplantation. Liver transplantation poses a very high risk of death in those with significant portopulmonary hypertension, where targeted medical therapies may improve functional status and allow successful transplantation in a small number of select patients.

The role of CX₃CL1/CX₃CR1 in pulmonary angiogenesis and intravascular monocyte accumulation in rat experimental hepatopulmonary syndrome

BACKGROUND & AIMS

Hepatopulmonary syndrome (HPS), classically attributed to intrapulmonary vascular dilatation, occurs in 15-30% of cirrhotics and causes hypoxemia and increases mortality. In experimental HPS after common bile duct ligation (CBDL), monocytes adhere in the lung vasculature and produce vascular endothelial growth factor (VEGF)-A and angiogenesis ensues and contribute to abnormal gas exchange. However, the mechanisms for these events are unknown. The chemokine fractalkine (CX(3)CL1) can directly mediate monocyte adhesion and activate VEGF-A and angiogenesis via its receptor CX(3)CR1 on monocytes and endothelium during inflammatory angiogenesis. We explored whether pulmonary CX(3)CL1/CX(3)CR1 alterations occur after CBDL and influence pulmonary angiogenesis and HPS.

METHODS

Pulmonary CX(3)CL1/CX(3)CR1 expression and localization, CX(3)CL1 signaling pathway activation, monocyte accumulation, and development of angiogenesis and HPS were assessed in 2- and 4-week CBDL animals. The effects of a neutralizing antibody to CX(3)CR1 (anti-CX(3)CR1 Ab) on HPS after CBDL were evaluated.

RESULTS

Circulating CX(3)CL1 levels and lung expression of CX(3)CL1 and CX(3)CR1 in intravascular monocytes and microvascular endothelium increased in 2- and 4-week CBDL animals as HPS developed. These events were accompanied by pulmonary angiogenesis, monocyte accumulation, activation of CX(3)CL1 mediated signaling pathways (Akt, ERK) and increased VEGF-A expression and signaling. Anti-CX(3)CR1 Ab treatment reduced monocyte accumulation, decreased lung angiogenesis and improved HPS. These events were accompanied by inhibition of CX(3)CL1 signaling pathways and a reduction in VEGF-A expression and signaling.

CONCLUSIONS

Circulating CX(3)CL1 levels and pulmonary CX(3)CL1/CX(3)CR1 expression and signaling increase after CBDL and contribute to pulmonary intravascular monocyte accumulation, angiogenesis and development of experimental HPS.

Population-based risk factors for elevated alanine aminotransferase in a South Texas Mexican-American population

BACKGROUND AND AIMS

Elevated alanine aminotransferase (ALT >40 IU/mL) is a marker of liver injury but provides little insight into etiology. We aimed to identify and stratify risk factors associated with elevated ALT in a randomly selected population with a high prevalence of elevated ALT (39%), obesity (49%) and diabetes (30%).

METHODS

Two machine learning methods, the support vector machine (SVM) and Bayesian logistic regression (BLR), were used to capture risk factors in a community cohort of 1532 adults from the Cameron County Hispanic Cohort (CCHC). A total of 28 predictor variables were used in the prediction models. The recently identified genetic marker rs738409 on the PNPLA3 gene was genotyped using the Sequenom iPLEX assay.

RESULTS

The four major risk factors for elevated ALT were fasting plasma insulin level and insulin resistance, increased BMI and total body weight, plasma triglycerides and non-HDL cholesterol, and diastolic hypertension. In spite of the highly significant association of rs738409 in females, the role of rs738409 in the prediction model is minimal, compared to other epidemiological risk factors. Age and drug and alcohol consumption were not independent determinants of elevated ALT in this analysis.

CONCLUSIONS

The risk factors most strongly associated with elevated ALT in this population are components of the metabolic syndrome and point to nonalcoholic fatty liver disease (NAFLD). This population-based model identifies the likely cause of liver disease without the requirement of individual pathological diagnosis of liver diseases. Use of such a model can greatly contribute to a population-based approach to prevention of liver disease.

Hepatopulmonary syndrome: update on pathogenesis and clinical features

Hepatopulmonary syndrome (HPS) is a serious vascular complication of liver disease that occurs in 5-32% of patients with cirrhosis. The presence of HPS markedly increases mortality. No effective medical therapies are currently available and liver transplantation is the only established treatment option for HPS. The definition and diagnosis of HPS are established by the presence of a triad of liver disease with intrapulmonary vascular dilation that causes abnormal arterial gas exchange. Experimental biliary cirrhosis induced by common bile duct ligation in the rat reproduces the pulmonary vascular and gas exchange abnormalities of human HPS and serves as a pertinent animal model. Pulmonary microvascular dilation and angiogenesis are two central pathogenic features that drive abnormal pulmonary gas exchange in experimental HPS, and thus might underlie HPS in humans. Defining the mechanisms involved in the microvascular alterations of HPS has the potential to lead to effective medical therapies. This Review focuses on the current understanding of the pathogenesis, clinical features and management of HPS.

PNPLA3 polymorphisms and liver aminotransferase levels in a Mexican American population

PURPOSE

This study examined genetic associations of patatin-like phospholipase domain containing 3 gene (PNPLA3) polymorphisms and liver aminotransferases in an extensively documented, randomly recruited Mexican American population at high risk of liver disease.

METHODS

Two single nucleotide polymorphisms (SNP) in the PNPLA3 gene (i.e., rs738409 and rs2281135) were genotyped in 1532 individuals. Population stratification was corrected by the genotyping of 103 ancestry informative markers (AIMs) for Mexican Americans.

RESULTS

Both PNPLA3 SNPs showed highly significant association with alanine aminotransferase (ALT) levels, but was also, in males, associated with aspartate aminotransferase (AST) levels. Haplotypic association test of the two SNPs suggested stronger genetic association with rs738409 than rs2281135. Obvious sex effects were observed: rs738409-sex interaction in ALT levels P = 8.37 x 10(-4); rs738409-sex interaction in AST levels P = 5.03 x 10(-3).

CONCLUSIONS

This population study highlights a sex-specific association of PNPLA3 polymorphisms and elevated liver enzymes in a population-based study, independent of common pathological factors of the metabolic syndrome. The strong genetic association found in women ≤ 50 years old, but not in women > 50 years old, suggests that sex hormones may mediate the sex effect.

Hepatopulmonary syndrome

Hepatopulmonary syndrome (HPS) is characterized by an oxygenation defect induced by pulmonary vascular dilatation in the setting of liver cirrhosis or portal hypertension. It is defined by an alveolar-arterial gradient > 15 mm Hg measured at sea level. This syndrome is seen in 15 to 30% of cirrhotic patients and has been associated with worse survival. Most HPS patients are either asymptomatic or develop the insidious onset of dyspnea. The key event in its pathogenesis is the development of intrapulmonary vascular dilatation (IPVD), which has been linked to increased pulmonary levels of nitric oxide. Pulse oximetry is a useful screening test for HPS, which can guide subsequent use of arterial blood gases. Contrast-enhanced transthoracic echocardiography is the most effective test to demonstrate IPVD. Another method for detecting IPVD is the radionuclide lung perfusion scanning, using technetium-labeled macroaggregated albumin particles. Liver transplantation is the only available treatment for HPS, resulting in complete resolution or significant improvement in gas exchange in over 85% of patients.

Prevalence of metabolic syndrome and risks of abnormal serum alanine aminotransferase in Hispanics: a population-based study

Aim

Study the prevalence of metabolic syndrome (MS) and risk factors for and association with elevated alanine aminotransferase (ALT) as markers of hepatic injury in a large Hispanic health disparity cohort with high rates of obesity.

Methods

Analysis of data from a prospective cross-sectional population based study. From 2004-7, we randomly recruited 2000 community participants to the Cameron County Hispanic Cohort collecting extensive socioeconomic, clinical and laboratory data. We excluded 153 subjects due to critical missing data. Pearson chi-square tests and Student's t-tests were used for categorical and continuous variable analysis, respectively. Logistic regression analysis was performed to determine the risk factors for elevated ALT.

Results

The mean age of the cohort was 45 years and 67% were females. The majority of the cohort was either overweight (32.4%) or obese (50.7%). Almost half (43.7%) had MS and nearly one-third diabetes. Elevated ALT level was more prevalent in males than females. Obesity was a strong risk for abnormal ALT in both genders. Hypertriglyceridemia, hypercholesterolemia and young age were risks for elevated ALT in males only, whereas increased fasting plasma glucose was associated with elevated ALT in females only.

Conclusion

We identified high prevalence of MS and markers of liver injury in this large Mexican American cohort with gender differences in prevalence and risk factors, with younger males at greatest risk.

Serial pulse oximetry in hepatopulmonary syndrome

BACKGROUND/AIM

The natural history of hepatopulmonary syndrome (HPS) is poorly characterized and how hypoxemia develops and progresses over time is unclear. We evaluated oxygenation over time in advanced liver disease patients with and without HPS using serial pulse oximetry.

METHODS

Data from a prospective cohort of patients evaluated for liver transplantation were analyzed. All patients with significant cardiopulmonary disease were excluded and patients with and without HPS were compared. Arterial oxygen saturation measurements with pulse oximetry (SpO(2)) were recorded serially from initial evaluation until transplantation or last clinic visit on record. Patients with SpO(2) measurements at ≥ 2 visits were included.

RESULTS

A total of 22 HPS patients were compared to 32 non-HPS patients (18 with intrapulmonary vasodilation on contrast echocardiography, CE) over a mean duration of 20 months and 4 SpO(2) measurements. HPS patients had lower SpO(2) at baseline (96.8 vs. 98.4%, P = 0.02) and at end of follow-up (95.8 vs. 98.2%, P = 0.02), and were more likely to have a ≥ 2% reduction (P = 0.04) and faster decline in SpO(2) as compared to non-HPS patients (F = 2.2, P = 0.04). HPS patients with lower SpO(2) and/or PO(2) at baseline appeared more likely to worsen over time. There was no difference in SpO(2) over time between the 2 non-HPS subgroups (- or +CE).

CONCLUSIONS

HPS patients have a significant decline in SpO(2) over time compared to non-HPS patients, and therefore, pulse oximetry may be useful for monitoring cirrhotics for development or worsening of HPS. Presence of intrapulmonary vasodilation in the absence of hypoxemia does not appear to affect SpO(2) over time.

Pulmonary complications of cirrhosis

Pulmonary vascular complications of liver disease comprise two distinct clinical entities: hepatopulmonary syndrome (HPS-microvascular dilatation and angiogenesis) and portopulmonary hypertension (POPH-vasoconstriction and remodeling in resistance vessels). These complications occur in similar pathophysiologic environments and may share pathogenic mechanisms. HPS is found in 15% to 30% of patients with cirrhosis and its presence increases mortality and the risks of liver transplantation, particularly when hypoxemia is present. Contrast echocardiography and arterial blood gas analysis are required to establish the diagnosis. No medical therapies are available, although liver transplantation is effective in reversing the syndrome. POPH is found in 4% to 8% of patients undergoing liver transplantation evaluation, and the presence of moderate to severe disease significantly increases perioperative transplant mortality. Transthoracic echocardiography is recommended for screening and right-heart catheterization is required to establish the diagnosis. Medical therapies are increasingly effective in improving pulmonary vascular hemodynamics in POPH and may result in better perioperative outcomes.

Pulmonary diseases and the liver

Chronic liver disease is associated with many pulmonary complications. Several, including hepatopulmonary syndrome, portopulmonary hypertension, and hepatic hydrothorax have been extensively reviewed. However, hepatobiliary manifestations of primary pulmonary diseases have received less attention. This review focuses on hepatobiliary complications of respiratory failure, cystic fibrosis, α-1 antitrypsin deficiency, sarcoidosis, and tuberculosis.

Vanishing bile duct syndrome in human immunodeficiency virus: Nevirapine hepatotoxicity revisited

Vanishing bile duct syndrome (VBDS) refers to a group of disorders characterized by prolonged cholestasis as a result of destruction and disappearance of intrahepatic bile ducts. Multiple etiologies have been indentified including infections, neoplastic disorders, autoimmune conditions and drugs. The natural history of this condition is variable and may involve resolution of cholestasis or progression with irreversible damage. VBDS is extremely rare in human immunodeficiency virus (HIV)-infected patients and anti-retroviral therapy has never been implicated as a cause. We encountered a young pregnant female with HIV and VBDS secondary to anti-retroviral therapy. Here, we report her clinical course and outcome.

Genetic risk factors for hepatopulmonary syndrome in patients with advanced liver disease

BACKGROUND & AIMS

Hepatopulmonary syndrome (HPS) affects 10%-30% of patients with cirrhosis and portal hypertension and significantly increases mortality. Studies in experimental models indicate that pulmonary angiogenesis contributes to the development of HPS, but pathogenesis in humans is poorly understood. We investigated genetic risk factors for HPS in patients with advanced liver disease.

METHODS

We performed a multicenter case-control study of patients with cirrhosis being evaluated for liver transplantation. Cases had an alveolar-arterial oxygen gradient > or = 15 mm Hg (or > or =20 mm Hg if age > 64 years) and contrast echocardiography with late appearance of microbubbles after venous injection of agitated saline (intrapulmonary vasodilatation); controls did not meet both criteria for case status. The study sample included 59 cases and 126 controls. We genotyped 1086 common single nucleotide polymorphisms (SNPs) in 94 candidate genes.

RESULTS

Forty-two SNPs in 21 genes were significantly associated with HPS after adjustments for race and smoking. Eight genes had at least 2 SNPs associated with disease: CAV3, ENG, NOX4, ESR2, VWF, RUNX1, COL18A1, and TIE1. For example, rs237872 in CAV3 showed an odds ratio of 2.75 (95% confidence interval: 1.65-4.60, P = .0001) and rs4837192 in ENG showed an odds ratio of 0.35 (95% confidence interval: 0.14-0.89, P = .027). Furthermore, variation in CAV3 and RUNX1 was associated with HPS in gene-based analyses.

CONCLUSIONS

Polymorphisms in genes involved in the regulation of angiogenesis are associated with the risk of HPS. Further investigation of these biologic pathways might elucidate the mechanisms that mediate the development of HPS in certain patients with severe liver disease.

Health-related quality of life and survival in liver transplant candidates

Health-related quality of life (HRQOL) is an important measure of the effects of chronic liver disease in affected patients that helps guide interventions to improve well-being. However, the relationship between HRQOL and survival in liver transplant candidates remains unclear. We examined whether the Physical Component Summary (PCS) and Mental Component Summary (MCS) scores from the Short Form 36 (SF-36) Health Survey were associated with survival in liver transplant candidates. We administered the SF-36 questionnaire (version 2.0) to patients in the Pulmonary Vascular Complications of Liver Disease study, a multicenter prospective cohort of patients evaluated for liver transplantation in 7 academic centers in the United States between 2003 and 2006. Cox proportional hazards models were used with death as the primary outcome and adjustment for liver transplantation as a time-varying covariate. The mean age of the 252 participants was 54 +/- 10 years, 64% were male, and 94% were white. During the 422 person years of follow-up, 147 patients (58%) were listed, 75 patients (30%) underwent transplantation, 49 patients (19%) died, and 3 patients were lost to follow-up. Lower baseline PCS scores were associated with an increased mortality rate despite adjustments for age, gender, Model for End-Stage Liver Disease score, and liver transplantation (P for the trend = 0.0001). The MCS score was not associated with mortality (P for the trend = 0.53). In conclusion, PCS significantly predicts survival in liver transplant candidates, and interventions directed toward improving the physical status may be helpful in improving outcomes in liver transplant candidates.

Plasma levels of S100A4 in portopulmonary hypertension

We previously showed that a single nucleotide polymorphism in S100A4 was associated with portopulmonary hypertension (PPHTN) in patients with advanced liver disease. We aimed to determine the association between plasma levels of S100A4 and PPHTN. We performed a case-control study of patients with advanced liver disease. Cases with PPHTN had mean pulmonary artery pressure >25 mmHg, pulmonary vascular resistance >240 dynes s cm(-5) and pulmonary capillary wedge pressure </=15 mmHg. Controls with liver disease had right ventricular systolic pressure <40 mmHg and normal right atrial and ventricular morphology by echocardiography. Plasma samples were assayed for S100A4. The study sample included 14 cases with PPHTN and 32 controls with liver disease. There was no difference in mean age between cases and controls (p = 0.52). Seventy-nine percent of cases were female compared with 44% of controls (p = 0.03). There was no difference in S100A4 levels between cases and controls (p = 0.58). Both groups had significantly higher S100A4 levels than healthy volunteers (p <0.05). There was no significant difference in plasma levels of S100A4 between PPHTN patients and controls with liver disease, although liver disease itself was associated with increased S100A4 levels.

Attenuation of experimental hepatopulmonary syndrome in endothelin B receptor-deficient rats

Experimental hepatopulmonary syndrome (HPS) after common bile duct ligation (CBDL) in rat is accompanied by increased lung vascular endothelial endothelin B (ETB) receptor expression and increased circulating levels of endothelin-1 (ET-1). The onset of HPS is hypothesized to be triggered by ET-1/ETB receptor activation of endothelial nitric oxide synthase (eNOS)-derived NO production in the pulmonary endothelium. However, whether functional pulmonary vascular ETB receptors are required for the development of experimental HPS is not defined. We evaluated the effects of vascular ETB receptor deficiency on the development of experimental HPS. The molecular and physiological alterations of HPS were compared in 2-wk CBDL wild-type and ETB receptor-deficient (transgenic sl/sl) rats. Relative to wild-type rats, basal hepatic and plasma ET-1 levels were elevated in sl/sl controls although, unlike wild-type animals circulating ET-1 levels, did not increase further after CBDL in sl/sl animals. In contrast to wild-type animals, ETB receptor-deficient rats did not develop increased Akt and eNOS expression and activation and did not develop gas exchange abnormalities of HPS after CBDL. There was a similar degree of pulmonary intravascular monocyte accumulation in both 2-wk CBDL sl/sl and wild-type animals. In conclusion, ETB receptor deficiency inhibits lung Akt/eNOS activation and prevents the onset of experimental HPS after CBDL. This effect is independent of inhibition of pulmonary intravascular monocyte accumulation. These results demonstrate that ET-1/ETB receptor signaling plays a key role in the initiation of experimental HPS.

Developmental changes in circulating IL-8/CXCL8 isoforms in neonates

Interleukin-8 (IL-8/CXCL8) is widely expressed in fetal tissues although inflammatory changes are not seen. Circulating IL-8 is comprised of an endothelial-derived [ala-IL-8](77) isoform and another, more potent [ser-IL-8](72) secreted by most other cells; [ala-IL-8](77) can be converted into [ser-IL-8](72) by proteolytic removal of an N-terminal pentapeptide from [ala-IL-8](77). In this study, we show [ala-IL-8](77) is the predominant circulating isoform of IL-8 in premature neonates but not in term neonates/adults, who have [ser-IL-8](72) as the major isoform. This isoform switch from the less potent [ala-IL-8](77) to [ser-IL-8](72) correlates with a maturational increase in the neutrophil chemotactic potency of plasma IL-8. The emergence of [ser-IL-8](72) as the major isoform is likely due to increased plasma [ala-IL-8](77)-convertase activity and/or changes in the cellular sources of IL-8. Developmental changes in IL-8 isoforms may serve to minimize its inflammatory effects in the fetus and also provide a mechanism to restore its full activity after birth.

Genetic risk factors for portopulmonary hypertension in patients with advanced liver disease

RATIONALE

Portopulmonary hypertension (PPHTN) occurs in 6% of liver transplant candidates. The pathogenesis of this complication of portal hypertension is poorly understood.

OBJECTIVES

To identify genetic risk factors for PPHTN in patients with advanced liver disease.

METHODS

We performed a multicenter case-control study of patients with portal hypertension. Cases had a mean pulmonary artery pressure >25 mm Hg, pulmonary vascular resistance >240 dynes.s(-1).cm(-5), and pulmonary capillary wedge pressure < or =15 mm Hg. Controls had a right ventricular systolic pressure < 40 mm Hg (if estimated) and normal right-sided cardiac morphology by transthoracic echocardiography. We genotyped 1,079 common single nucleotide polymorphisms (SNPs) in 93 candidate genes in each patient.

MEASUREMENTS AND MAIN RESULTS

The study sample included 31 cases and 104 controls. Twenty-nine SNPs in 15 candidate genes were associated with the risk of PPHTN (P < 0.05). Multiple SNPs in the genes coding for estrogen receptor 1, aromatase, phosphodiesterase 5, angiopoietin 1, and calcium binding protein A4 were associated with the risk of PPHTN. The biological relevance of one of the aromatase SNPs was supported by an association with plasma estradiol levels.

CONCLUSIONS

Genetic variation in estrogen signaling and cell growth regulators is associated with the risk of PPHTN. These biologic pathways may elucidate the mechanism for the development of PPHTN in certain patients with severe liver disease.

Serotonin transporter polymorphisms in patients with portopulmonary hypertension

BACKGROUND

The long allele of a functional promoter polymorphism in the serotonin transporter (SERT) is associated with an increased risk of some forms of pulmonary arterial hypertension. We hypothesized that the long allele or other polymorphisms in SERT would be associated with an increased risk of portopulmonary hypertension (PPHTN) in patients with advanced liver disease.

METHODS

We performed a multicenter case-control study. Subjects undergoing liver transplant evaluation at seven centers were prospectively screened for the presence of PPHTN using transthoracic echocardiography. PPHTN was confirmed by right heart catheterization using standard criteria.

RESULTS

The study sample included 30 case patients with PPHTN and 109 control subjects with advanced liver disease. There was no significant association between the long allele and case status in an adjusted additive model (odds ratio, 0.63; 95% confidence interval, 0.33 to 1.21; p = 0.17). If anything, LL genotype tended to be associated with a lower risk of PPHTN. There were no associations between other SERT polymorphisms and PPHTN.

CONCLUSIONS

SERT polymorphisms are not associated with the risk of PPHTN in patients with advanced liver disease. Other clinical or genetic risk factors may play a role in this complication of portal hypertension.

Low intensity shear stress increases endothelial ELR+ CXC chemokine production via a focal adhesion kinase-p38{beta} MAPK-NF-{kappa}B pathway

CXC chemokines with a glutamate-leucine-arginine (ELR) tripeptide motif (ELR(+) CXC chemokines) play an important role in leukocyte trafficking into the tissues. For reasons that are not well elucidated, circulating leukocytes are recruited into the tissues mainly in small vessels such as capillaries and venules. Because ELR(+) CXC chemokines are important mediators of endothelial-leukocyte interaction, we compared chemokine expression by microvascular and aortic endothelium to investigate whether differences in chemokine expression by various endothelial types could, at least partially, explain the microvascular localization of endothelial-leukocyte interaction. Both in vitro and in vivo models indicate that ELR(+) CXC chemokine expression is higher in microvascular endothelium than in aortic endothelial cells. These differences can be explained on the basis of the preferential activation of endothelial chemokine production by low intensity shear stress. Low shear activated endothelial ELR(+) CXC chemokine production via cell surface heparan sulfates, beta(3)-integrins, focal adhesion kinase, the mitogen-activated protein kinase p38beta, mitogen- and stress-associated protein kinase-1, and the transcription factor.

Risk factors and impact of chronic obstructive pulmonary disease in candidates for liver transplantation

Chronic obstructive pulmonary disease (COPD) may cause significant symptoms and have an impact on survival. Smoking is an important risk factor for COPD and is common in candidates for liver transplantation; however, the risk factors for and outcomes of COPD in this population are unknown. We performed a prospective cohort study of 373 patients being evaluated for liver transplantation at 7 academic centers in the United States. COPD was characterized by expiratory airflow obstruction and defined as follows: prebronchodilator forced expiratory volume in 1 second/forced vital capacity < 0.70. Patients completed the Liver Disease Quality of Life Questionnaire 1.0, which included the Short Form-36. The mean age of the study sample was 53 +/- 9 years, and 234 (63%) were male. Sixty-seven patients (18%, 95% confidence interval 14%-22%) had COPD, and 224 (60%) had a history of smoking. Eighty percent of patients with airflow obstruction did not previously carry a diagnosis of COPD, and 27% were still actively smoking. Older age and any smoking (odds ratio = 3.74, 95% confidence interval 1.94-7.23, P < 0.001) were independent risk factors for COPD. Patients with COPD had worse New York Heart Association functional class and lower physical component summary scores on the 36-Item Short Form but had short-term survival similar to that of patients without COPD. In conclusion, COPD is common and often undiagnosed in candidates for liver transplantation. Older age and smoking are significant risk factors of COPD, which has adverse consequences on functional status and quality of life in these patients.

Pilot study of pentoxifylline in hepatopulmonary syndrome

Hepatopulmonary syndrome (HPS) results when chronic liver disease or portal hypertension causes intrapulmonary microvascular dilatation with hypoxemia. In experimental HPS, tumor necrosis factor alpha (TNF-alpha) overproduction contributes to vasodilatation, which is improved by pentoxifylline, a TNF-alpha inhibitor. The effectiveness of pentoxifylline in humans is unknown. The aim of this open-label, single-arm clinical trial was to assess the efficacy and tolerability of pentoxifylline in patients with cirrhosis and advanced HPS undergoing liver transplantation evaluation. Nine adults with cirrhosis and moderate to severe HPS were enrolled. All patients had an initial 2-week titration to a target dose of pentoxifylline of 400 mg by mouth every 8 hours, which was continued for 6 weeks. Baseline and follow-up arterial blood gases and TNF-alpha levels were evaluated. Adverse effects and tolerability were assessed. The 9 patients had a mean age of 55 +/- 10 years, and 67% were female. The most common causes of cirrhosis were hepatitis C virus and alcohol (55%). The mean Model for End-Stage Liver Disease score was 11 (range, 6-19), and patients had advanced hypoxemia [mean partial pressure of arterial oxygen (PaO(2)) = 54 +/- 12 mm Hg, mean alveolar-arterial oxygen gradient (A-a PaO(2)) = 57 +/- 15 mm Hg]. Of the 9 patients enrolled, follow-up blood gases were done in 7. There was no significant change in PaO(2) (P = 0.3) or A-a PaO(2) (P = 0.3) with treatment. Pentoxifylline was poorly tolerated. Nausea (100%) and vomiting (56%) were the predominant side effects, and only a single patient was able to complete full-dose therapy. Treatment with pentoxifylline did not improve arterial oxygenation in advanced HPS, and tolerance was limited by gastrointestinal toxicity.

Clinical risk factors for portopulmonary hypertension

Portopulmonary hypertension affects up to 6% of patients with advanced liver disease, but the predictors and biologic mechanism for the development of this complication are unknown. We sought to determine the clinical risk factors for portopulmonary hypertension in patients with advanced liver disease. We performed a multicenter case-control study nested within a prospective cohort of patients with portal hypertension recruited from tertiary care centers. Cases had a mean pulmonary artery pressure > 25 mm Hg, pulmonary vascular resistance > 240 dynes x second x cm(-5), and pulmonary capillary wedge pressure < or = 15 mm Hg. Controls had a right ventricular systolic pressure < 40 mm Hg (if estimable) and normal right-sided cardiac morphology by transthoracic echocardiography. The study sample included 34 cases and 141 controls. Female sex was associated with a higher risk of portopulmonary hypertension than male sex (adjusted odds ratio = 2.90, 95% confidence interval 1.20-7.01, P = 0.018). Autoimmune hepatitis was associated with an increased risk (adjusted odds ratio = 4.02, 95% confidence interval 1.14-14.23, P = 0.031), and hepatitis C infection was associated with a decreased risk (adjusted odds ratio = 0.24, 95% confidence interval 0.09-0.65, P = 0.005) of portopulmonary hypertension. The severity of liver disease was not related to the risk of portopulmonary hypertension.

CONCLUSION

Female sex and autoimmune hepatitis were associated with an increased risk of portopulmonary hypertension, whereas hepatitis C infection was associated with a decreased risk in patients with advanced liver disease. Hormonal and immunologic factors may therefore be integral to the development of portopulmonary hypertension.