Clinical Outcomes after Liver Transplantation in Patients with Portopulmonary Hypertension

Making Living-donor Liver Transplantation a Viable Option for Patients With Portopulmonary Hypertension

Liver transplantation (LT) in patients with significant portopulmonary hypertension (PoPH) is associated with an increased risk of several complications, including graft failure. Graft loss is one of the major reasons. Living donor LT (LDLT) is not routinely performed in the United States in this patient population. In addition, ethical considerations often preclude donation from healthy donors in the setting of a procedure associated with an elevated risk of recipient morbidity and mortality. However, LDLT allows LT to be performed electively, using a superior graft with an improved probability of a good outcome. The key to success in managing these patients is establishing a multidisciplinary team that follows an institutional protocol with clear evaluation and management criteria. These criteria include screening and early diagnosis as well as treatment of PoPH with the goal of optimizing pulmonary arterial hemodynamics and maintaining right ventricular function. Any protocol should include admitting the patient to the hospital a day before surgery for placement of a pulmonary artery catheter to measure and derive relevant hemodynamic variables. A multidisciplinary team should determine the fitness for a transplant a after a careful review of the most up-to-date clinical information. Finally, the team prescribes and executes a plan for optimization and safe perioperative management of the patient. In this report, we discuss our approach to the perioperative management of a patient with significant PoPH who safely underwent LDLT with an excellent postoperative outcome.

Pulmonary Complications of Portal Hypertension

Portopulmonary hypertension (POPH), hepatopulmonary syndrome, and hepatic hydrothorax constitute significant complications of portal hypertension, with important implications for management and liver transplantation (LT) candidacy. POPH is characterized by obstruction and remodeling of the pulmonary resistance arterial bed. Hepatopulmonary syndrome is the most common pulmonary vascular disorder, characterized by intrapulmonary vascular dilatations causing impaired gas exchange. LT may improve prognosis in select patients with POPH. LT is the only effective treatment of hepatopulmonary syndrome. Hepatic hydrothorax is defined as transudative pleural fluid accumulation that is not explained by primary cardiopulmonary or pleural disease. LT is the definitive cure for hepatic hydrothorax.

Hemodynamic and Clinical Response to Liver Transplantation in Children and Young Adults POPH Patients

Portopulmonary hypertension is an intractable form of pulmonary hypertension. Although liver transplantation is recommended for patients who respond poorly to treatments, the mechanisms by which liver transplantation improves pulmonary hypertension remain unclear. The present study investigated these mechanisms by retrospectively evaluating patients' data. This study retrospectively evaluated echocardiography and catheterization data before and after liver transplantation in 12 patients who underwent liver transplantation from 2001 to 2019. The 12 patients included one male and 11 females, of median age at liver transplantation of 10 years, 2 months. Nine patients underwent liver transplantation for congenital biliary atresia and three for portal vein aplasia or hypoplasia. Mean pulmonary arterial pressure was 44.1 ± 8.1 mmHg at the first cardiac catheter examination, 35.3 ± 7.8 mmHg before liver transplantation, and 29.5 ± 9.3 mmHg 6 months after liver transplantation. Pulmonary artery pressure was reduced by treatments of pulmonary hypertension and by liver transplantation. Pulmonary vascular resistance did not differ before and after liver transplantation, whereas the cardiac index decreased significantly, indicating that the significant reduction in mean pulmonary artery pressure was due to a decrease in cardiac index. Decreased cardiac index was thought to result from improvements in hyperdynamic conditions due to increased (normalized) systemic vascular resistance. Liver transplantation likely suppresses shear stress on pulmonary arteries, preventing further damage by hyper-circulation. A longer-term evaluation is required to determine the effect of improving pulmonary artery remodeling.

Portopulmonary hypertension: peculiarities of diagnosis and treatment

Portopulmonary hypertension is defined as the development of pulmonary hypertension secondary to portal one. Its exact prevalence is difficult to determine due to the lack of routine screening in patients with portal hypertension. Hemodynamic changes associated with portal hypertension, including the hyperdynamic state, portosystemic shunts, and splanchnic vasodilation, cause significant disturbances in the pulmonary vasculature and play a key role in the pathogenesis of the disease. Without treatment, portopulmonary hypertension leads to progressive right ventricular failure with a poor prognosis. Although Doppler echocardiography is the best initial screening tool for symptomatic patients and candidates for liver transplant, right heart catheterization remains the gold standard for disease diagnosis. Treatment of patients with portopulmonary hypertension is aimed at improving cardiac function, reducing pulmonary vascular resistance, and optimizing functional capacity. Pulmonary hypertension-specific therapy, which includes prostacyclin and its receptor agonists, endothelin receptor antagonists, phosphodiesterase inhibitors, and guanylate cyclase stimulators, plays a key role in the treatment of patients with portopulmonary hypertension. Small uncontrolled and recent single randomized controlled trials have reported promising results of vasodilator therapy in terms of clinical and hemodynamic improvement in patients, allowing certain patients to undergo liver transplantation. This review discusses the epidemiology, approach to diagnosis and treatment of patients with portopulmonary hypertension. We used MEDLINE database on the PubMed platform and the Cochrane library to search for literature sources using the keywords: portopulmonary hypertension, portal hypertension, pulmonary hypertension, liver cirrhosis, pulmonary complications.

The applications of ECMO in liver transplant recipients

Extracorporeal membrane oxygenation (ECMO) has emerged as a vital instrument for sustaining respiratory and cardiac functions when traditional methods have failed. Its function in managing acute pulmonary and cardiac challenges during liver transplantation (LT) has expanded significantly. While ECMO was initially viewed as a rescue strategy for acute intraoperative or posttransplant complications, its application now also encompasses the pretransplant stage of LT. Our review aims to thoroughly summarize both research and specific cases where ECMO has been utilized across pre- and perioperative phases in liver transplant recipients. By assessing the published literature, we discuss specific indications, the types of ECMO employed, their outcomes, and the unique challenges of applying ECMO during LT. In particular, the pretransplant use of ECMO is increasing, and its prudent introduction prior to LT, supported by meticulous planning, has the potential to optimize patient outcomes. It is challenging to manage liver transplant patients on ECMO. More research and experience are needed to refine the techniques and improve patient outcomes. Furthermore, decision-making must be tailored to each patient's unique circumstances, and a clear, practical, and well-defined plan for subsequent steps is essential.

Portopulmonary Hypertension: An Updated Review

Portal hypertension may have major consequences on the pulmonary vasculature due to the complex pathophysiological interactions between the liver and lungs. Portopulmonary hypertension (PoPH), a subset of group 1 pulmonary hypertension (PH), is a serious pulmonary vascular disease secondary to portal hypertension, and is the fourth most common subtype of pulmonary arterial hypertension. It is most commonly observed in cirrhotic patients; however, patients with noncirrhotic portal hypertension can also develop it. On suspicion of PoPH, the initial evaluation is by a transthoracic echocardiogram in which, if elevated pulmonary pressures are shown, patients should undergo right heart catheterization to confirm the diagnosis. The prognosis is extremely poor in untreated patients; therefore, management includes pulmonary arterial hypertension therapies with the aim of improving pulmonary hemodynamics and moving patients to orthotopic liver transplantation (OLT). In this article, we review in detail the epidemiology, pathophysiology, process for diagnosis, and most current treatments including OLT and prognosis in patients with PoPH. In addition, we present a diagnostic algorithm that includes the current criteria to properly select patients with PoPH who are candidates for OLT.

Current clinical understanding and effectiveness of portopulmonary hypertension treatment

Portopulmonary hypertension (PoPH) is a rare subtype of Group 1 pulmonary arterial hypertension (PAH) with a poor prognosis. According to the most up-to-date definition, PoPH is characterized by a mean pulmonary arterial pressure (PAP) of >20 mmHg at rest, a pulmonary artery wedge pressure of ≤15 mmHg, and a pulmonary vascular resistance (PVR) of >2 Wood units with portal hypertension. Like PAH, PoPH is underpinned by an imbalance in vasoactive substances. Therefore, current guidelines recommend PAH-specific therapies for PoPH treatment; however, descriptions of the actual treatment approaches are inconsistent. Given the small patient population, PoPH is often studied in combination with idiopathic PAH; however, recent evidence suggests important differences between PoPH and idiopathic PAH in terms of hemodynamic parameters, treatment approaches, survival, socioeconomic status, and healthcare utilization. Therefore, large, multi-center registry studies are needed to examine PoPH in isolation while obtaining statistically meaningful results. PoPH has conventionally been excluded from clinical drug trials because of concerns over hepatotoxicity. Nevertheless, newer-generation endothelin receptor antagonists have shown great promise in the treatment of PoPH, reducing PVR, PAP, and World Health Organization functional class without causing hepatotoxicity. The role of liver transplantation as a treatment option for PoPH has also been controversial; however, recent evidence shows that this procedure may be beneficial in this patient population. In the future, given the shortage of liver donors, predictors of a favorable response to liver transplantation should be determined to select the most eligible patients. Collectively, advances in these three areas could help to standardize PoPH treatment in the clinic.

Portopulmonary hypertension practice patterns after liver transplantation

Portopulmonary hypertension (POPH) is a type of pulmonary arterial hypertension occurring exclusively in those with portal hypertensive liver disease. Liver transplantation (LT) can significantly improve outcomes. Current guidelines counsel against immediate adjustments to targeted therapy after LT and suggest routine echocardiography as sufficiently informative to guide therapeutic adjustments. Current practice patterns for adjusting targeted therapy after LT in POPH, and how they compare with guidelines, are not well established. To answer this question, we performed an institutional review board-approved, cross-sectional mixed-methods survey-based study of US POPH providers. Anonymized requests to complete the survey were sent through professional networks between January 20, 2022, and April 20, 2022. Responses were compared between cardiologists and pulmonologists using Fisher's exact tests, at a significance of 0.05. A total of 85 POPH physicians were included in the final analysis (66% pulmonologists and 34% cardiologists). Following LT, the majority of respondents routinely used a combination of standard cardiopulmonary assessment modalities to guide adjustment of targeted therapy following LT. Most respondents (69%) started by adjusting parenteral prostacyclins with small titrations and frequent reassessments within 3 months of LT, but some (19.7%) adjusted targeted therapy immediately after LT. Our results showed that the majority of respondents favored serial integrated cardiopulmonary testing (including routine right heart catheterization) to guide the adjustment of targeted therapy in POPH after LT, and almost one-fifth of respondents weaned therapy immediately after LT. Our study demonstrates heterogeneity in POPH practice patterns after LT, highlights differences between current practice patterns and the most recent guidelines, emphasizes the need for additional research, and supports a team-based approach to standardize care for these high-risk patients and optimize post-LT outcomes.

Portopulmonary Hypertension

PoPH is a well-recognized complication of portal hypertension with or without cirrhosis and is classified as a subset of PAH. Identification of PoPH is crucial as it has a major impact on prognosis and liver transplant candidacy. Echocardiogram is the initial screening tool of choice and the patient should proceed to RHC for confirmation. PAH-directed therapy is the treatment of choice, allowing the patient to achieve a hemodynamic threshold to undergo a liver transplant safely.

Struggling Between Liver Transplantation and Portopulmonary Hypertension

Portopulmonary hypertension (PoPH) is a progressive, ultimately fatal cardiopulmonary disease that occurs exclusively in patients with underlying portal hypertensive liver disease. PoPH outcomes are driven by both the severity of underlying liver disease and the degree of cardiac adaptation to elevated pulmonary pressures. The mainstay of treatment in PoPH is targeted pulmonary vascular therapy. Liver transplantation (LT) can be beneficial in some patients, but is associated with considerable risks in the PoPH population, and outcomes are variable. The optimal management strategy for PoPH, LT, or medical therapy alone, is unclear, and further research is needed to help guide clinical decision-making.

Portopulmonary Hypertension in Nontransplanted Patients: Results of the Largest US Single-Institution Registry

OBJECTIVE

To explore clinical characteristics, risk profiles, and outcomes of patients with portopulmonary hypertension (PoPH) who have contraindications to liver transplant (LT).

METHODS

From the largest US single-institution registry of patients with PoPH, we analyzed 160 patients who did not receive LT between 1988 to 2019. Pulmonary arterial hypertension (PAH)-pertinent characteristics, hemodynamic features, treatments, and risk stratification were compared at baseline, first follow-up visit, and censor/death time.

RESULTS

Median survival for the entire cohort was 27.5 months from the diagnosis of PoPH. Overall survival was 89%, 77%, 51%, and 38% at 6 months, 1 year, 3 years, and 5 years, respectively. Survival was significantly affected by the severity of liver disease (P<.001). Most patients received PAH-specific therapies (136 [85%]), predominantly monotherapy (123 [77%)]. With treatment, significant improvements were noted in World Health Organization functional class (P=.04), 6-minute walk distance (P<.001), right ventricular function (P<.001), pulmonary vascular resistance (P<.001), and Registry to Evaluate Early and Long-term Pulmonary Arterial Hypertension Disease Management (REVEAL) Lite 2 score (P=.02) univariately. Per European Society of Cardiology risk stratification, no patient met full criteria for low risk at baseline or at follow-up. In a multivariate Cox risk model, 6-minute walk distance, right atrial pressure, pulmonary capillary wedge pressure, bilirubin level, and Model for End-Stage Liver Disease-sodium score of 15 or higher were associated with increased risk of death.

CONCLUSION

Patients with PoPH who did not undergo LT had a poor prognosis. This persisted despite use of PAH-specific therapies and significant improvements in hemodynamics, echocardiography parameters of right ventricle function, 6-minute walk distance, and World Health Organization functional class.

Mending the Model for End-Stage Liver Disease: An in-depth review of the past, present, and future portopulmonary hypertension Model for End-Stage Liver Disease exception

Patients with portopulmonary hypertension (POPH) have an increased cardiovascular and overall mortality risk when undergoing liver transplantation (LT). However, such risk is not captured in their Model for End-Stage Liver Disease (MELD) laboratory score. POPH MELD exception criteria were established in 2006 with the aim of prioritizing these patients for LT prior to pulmonary hypertension (PH) progression and eventual right heart failure. The original criteria emphasized a posttreatment, pre-LT mean pulmonary arterial pressure (mPAP) of <35 mm Hg and pulmonary vascular resistance (PVR) <400 dynes-s-cm^-5 or <5 Wood units (WU). Since 2006, there have been important advances in the treatment of POPH with pulmonary arterial hypertension (PAH)-targeted therapies and newer evidence regarding LT outcomes and risk factors for perioperative mortality. Specifically, PVR rather than mPAP has been shown to be more strongly associated with outcomes, including mortality. In addition, among treated patients with POPH, mPAP may be persistently elevated related to an elevated cardiac output or other factors that do not necessarily reflect POPH disease severity. Thus, in February 2021, the Organ Procurement and Transplantation Network approved proposed modifications to POPH MELD exception criteria, now allowing either of the following posttreatment, pre-LT hemodynamic profiles: mPAP less than 35 mm Hg and posttreatment PVR less than 400 dynes-s-cm^-5 (or less than 5 WU) or mPAP greater than or equal to 35 mm Hg and less than 45 mm Hg and posttreatment PVR less than 240 dynes-s-cm^-5 (or less than 3 WU). This article reviews the history of the POPH MELD exception criteria, describes the recent modifications to the exception criteria and the evidence supporting them, and highlights unanswered questions and areas for future research.

Pulmonary Vascular Resistance Predicts Mortality and Graft Failure in Transplantation Patients With Portopulmonary Hypertension

Portopulmonary hypertension (POPH) is a pulmonary vascular disease associated with significant morbidity and mortality in those with liver disease, conferring a higher mortality in patients awaiting liver transplantation (LT). Although not a transplant indication, patients with POPH can experience significant clinical improvement following LT, and those maintaining a mean pulmonary artery pressure (MPAP) <35mm Hg and a pulmonary vascular resistance (PVR) <5 Woods units (WU) are granted additional listing points to expedite LT. The effect of POPH on posttransplant outcomes such as mortality and graft failure, however, is not well defined. We performed a retrospective cohort study of the US Organ Procurement and Transplantation Network database of all adult patients who underwent LT between January 1, 2006, and December 1, 2020. Using adjusted accelerated failure time models, we examined the relationship between a diagnosis of POPH and outcomes following LT and the relationship between pre-LT hemodynamics and post-LT survival (alive with a functioning graft) in patients with POPH. Compared with those undergoing transplants without exception points, patients with POPH had comparable post-LT survival rates but were significantly more likely to have graft failure. Both pre-LT MPAP and PVR predicted post-LT survival in POPH, with a pre-LT PVR of ≥1.6 WU, more than doubling the hazard for mortality (death or a nonfunctioning graft; coefficient, 2.01; standard error, 0.85; hazard ratio, 2.21; P = 0.02). POPH may confer a significantly higher risk of post-LT graft failure compared with patients with cirrhosis without POPH, and a pre-LT PVR of ≥1.6 WU may predict post-LT survival. Further investigation into the relationship between pre-LT hemodynamics, right ventricular function, and post-LT outcomes of mortality and graft failure in POPH is needed.

Hepatopulmonary Syndrome and Portopulmonary Hypertension: Pulmonary Vascular Complications of Liver Disease

Pulmonary vascular disease is a frequent complication of chronic liver disease and portal hypertension, affecting up to 30% of patients. There are two distinct pulmonary vascular complications of liver disease: hepatopulmonary syndrome (HPS) and portopulmonary hypertension (POPH). HPS affects 25% of patients with chronic liver disease and is characterized by intrapulmonary vasodilatation and abnormal arterial oxygenation. HPS negatively impacts quality of life and is associated with a 2-fold increased risk of death compared to controls with liver disease without HPS. Angiogenesis, endothelin-1 mediated endothelial dysfunction, monocyte influx, and alveolar type 2 cell dysfunction seem to play important roles in disease pathogenesis but there are currently no effective medical therapies. Fortunately, HPS resolves following liver transplant (LT) with improvements in hypoxemia. POPH is a subtype of pulmonary arterial hypertension (PAH) characterized by an elevated mean pulmonary arterial pressure and pulmonary vascular resistance in the setting of normal left-sided filling pressures. POPH affects 5% to 6% of patients with chronic liver disease. Although the pathogenesis has not been fully elucidated, endothelial dysfunction, inflammation, and estrogen signaling have been identified as key pathways involved in disease pathogenesis. POPH is typically treated with PAH targeted therapy and may also improve with liver transplantation in selected patients. This article highlights what is currently known regarding the diagnosis, management, pathobiology, and outcomes of HPS and POPH. Ongoing research is needed to improve understanding of the pathophysiology and outcomes of these distinct and often misunderstood pulmonary vascular complications of liver disease. © 2021 American Physiological Society. Compr Physiol 11:1-22, 2021.

Causes and Circumstances of Death in Portopulmonary Hypertension

The causes and circumstances surrounding death are poorly studied in patients with portopulmonary hypertension (PoPH). We sought to determine the specific reasons for dying and characteristics surrounding this process in patients with PoPH.

Outcomes of Liver Transplantation in Treated Portopulmonary Hypertension Patients With a Mean Pulmonary Arterial Pressure ≥35 mm Hg

Portopulmonary hypertension (POPH), pulmonary arterial hypertension (PAH) that develops in the setting of portal hypertension, affects 5%–6% of patients with liver disease and is associated with significant morbidity and mortality. A mean pulmonary arterial pressure (mPAP) threshold of 35 mm Hg is used to stratify perioperative risk and liver transplant eligibility in treated POPH patients but does not take into account the specific factors that contribute to the pressure elevation.