TXPortopulmonary hypertension (POPH) is a serious complication of cirrhosis that is associated with mortality beyond that predicted by the Model for End-Stage Liver Disease (MELD) score. Increased pulmonary vascular resistance (PVR) may be initiated by pulmonary vasoconstriction, altered levels of circulating mediators, or shear stress, and can eventually lead to the classic vascular remodeling (plexiform lesion) that characterizes POPH. Portal hypertension is a prerequisite for the diagnosis of POPH, although the severity of pulmonary hypertension is unrelated to the severity of portal hypertension or the nature or severity of liver disease. POPH precludes liver transplantation (LT) unless the mean pulmonary artery pressure (MPAP) can be reduced to a safe level. The concept of an acceptable pressure has changed: we now consider both MPAP and PVR in the diagnosis, and we include the transpulmonary pressure gradient so that we can factor in fluid overload and left ventricular failure. Pulmonary vasodilator therapy includes oral, inhaled, and parenteral agents, and one or more of these agents may significantly lower pulmonary artery pressures to the point that LT becomes possible. The United Network for Organ Sharing recommends MELD exception points for patients with medically controlled POPH, but this varies by region. Patients who undergo LT need specialized intraoperative and postoperative management, which includes the availability of intraoperative transesophageal echocardiography for assessing right ventricular function, and rapidly acting vasodilators (eg, inhaled nitric oxide and/or epoprostenol). Published case series suggest excellent outcomes after LT for patients who respond to medical therapy.

Background The current Organ Procurement Transplantation Network (OPTN) policy grants Model for End Stage Liver Disease (MELD) exception points to patients with portopulmonary hypertension (POPH), but potentially important factors, such as severity of liver disease and pulmonary hypertension, are not included in the exception score, and may affect survival. The purpose of this study was to identify significant predictors of waitlist mortality in patients with POPH. Methods We performed a retrospective cohort study of patients in the OPTN database with hemodynamics consistent with POPH [defined as mean pulmonary arterial pressure (mPAP) >25mmHg and pulmonary vascular resistance (PVR) ≥240 dynes•s•cm−5] who were approved for a POPH MELD exception between 2006 and 2014. Using a Cox proportional hazards model, we identified predictors of waitlist mortality (or removal for clinical deterioration). Results One hundred ninety adults were included. Age (HR 1.04, 95% CI 1.00-1.08, P=0.0499), initial native MELD score (HR 1.11, 95% CI 1.05-1.17, P<0.001), and initial PVR (HR 1.12 per 100 dynes•s•cm−5, 95% CI 1.02-1.23, P=0.02) were the only significant univariate predictors of waitlist mortality and remained significant predictors in a multivariate model, which had a c-statistic of 0.71. PVR and mPAP were not significant predictors of posttransplant mortality. Conclusions Both the severity of liver disease and POPH (as assessed by MELD and PVR, respectively) were significantly associated with waitlist, but not posttransplant, mortality in patients with approved MELD exceptions for POPH. Both factors should potentially be included in the POPH MELD exception score to more accurately reflect waitlist mortality risk.

BackgroundHuman immunodeficiency virus (HIV) infected patients are at increased risk for the development of pulmonary arterial hypertension (PAH). Recent reports have demonstrated that HIV associated viral proteins induce reactive oxygen species (ROS) with resultant endothelial cell dysfunction and related vascular injury. In this study, we explored the impact of HIV protein induced oxidative stress on production of hypoxia inducible factor (HIF)-1α and platelet-derived growth factor (PDGF), critical mediators implicated in the pathogenesis of HIV-PAH.MethodsThe lungs from 4-5 months old HIV-1 transgenic (Tg) rats were assessed for the presence of pulmonary vascular remodeling and HIF-1α/PDGF-BB expression in comparison with wild type controls. Human primary pulmonary arterial endothelial cells (HPAEC) were treated with HIV-associated proteins in the presence or absence of pretreatment with antioxidants, for 24 hrs followed by estimation of ROS levels and western blot analysis of HIF-1α or PDGF-BB.ResultsHIV-Tg rats, a model with marked viral protein induced vascular oxidative stress in the absence of active HIV-1 replication demonstrated significant medial thickening of pulmonary vessels and increased right ventricular mass compared to wild-type controls, with increased expression of HIF-1α and PDGF-BB in HIV-Tg rats. The up-regulation of both HIF-1α and PDGF-B chain mRNA in each HIV-Tg rat was directly correlated with an increase in right ventricular/left ventricular+septum ratio. Supporting our in-vivo findings, HPAECs treated with HIV-proteins: Tat and gp120, demonstrated increased ROS and parallel increase of PDGF-BB expression with the maximum induction observed on treatment with R5 type gp-120CM. Pre-treatment of endothelial cells with antioxidants or transfection of cells with HIF-1α small interfering RNA resulted in abrogation of gp-120CM mediated induction of PDGF-BB, therefore, confirming that ROS generation and activation of HIF-1α plays critical role in gp120 mediated up-regulation of PDGF-BB.ConclusionIn summary, these findings indicate that viral protein induced oxidative stress results in HIF-1α dependent up-regulation of PDGF-BB and suggests the possible involvement of this pathway in the development of HIV-PAH.

Despite numerous therapeutic advances in pulmonary arterial hypertension, patients continue to suffer high morbidity and mortality, particularly considering a median age of 50 years. This article explores whether early, robust reduction of right ventricular afterload would facilitate substantial improvement in right ventricular function and thus whether afterload reduction should be a treatment goal for pulmonary arterial hypertension. The earliest clinical studies of prostanoid treatment in pulmonary arterial hypertension demonstrated an important link between lowering mean pulmonary arterial pressure (or pulmonary vascular resistance) and improved survival. Subsequent studies of oral monotherapy or sequential combination therapy demonstrated smaller reductions in mean pulmonary arterial pressure and pulmonary vascular resistance. More recently, retrospective reports of initial aggressive prostanoid treatment or initial combination oral and parenteral therapy have shown marked afterload reduction along with significant improvements in right ventricular function. Some data suggest that reaching threshold levels for pressure or resistance (components of right ventricular afterload) may be key to interrupting the self-perpetuating injury of pulmonary vascular disease in pulmonary arterial hypertension and could translate into improved long-term clinical outcomes.Based on these clues, the authors postulate that improved clinical outcomes might be achieved by targeting significant afterload reduction with initial oral combination therapy and early parenteral prostanoids.

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