Hepatopulmonary Syndrome and Portopulmonary Hypertension: Current Status and Implications for Liver Transplantation

Abstract

Purpose of review: Hepatopulmonary syndrome (HPS) and portopulmonary hypertension (PoPH) are both pulmonary vascular complications of advanced liver disease; however, these syndromes have distinct pathophysiology, clinical implications, and management.

Recent findings: While both conditions are associated with portal hypertension, HPS results from diffuse pulmonary capillary vasodilation and PoPH results from vasoconstriction and vascular remodeling of pulmonary arteries. In HPS, no medical therapies clearly improve outcomes; however, patients have excellent post-LT outcomes with near uniform reversal of hypoxemia. In PoPH, several medical therapies used in idiopathic pulmonary hypertension have been shown improve pulmonary hemodynamics, symptoms, and potentially LT outcomes; however, further study is needed to determine best treatment regimens, long-term outcomes on medical therapy, and role of LT.

Summary: While HPS results in severe hypoxemia that is usually reversible by LT, PoPH patients develop progressive pulmonary hypertension that may improve with medical therapy.

Keywords: arterial hypoxemia with elevated A-a gradient; hepatopulmonary syndrome; intravascular pulmonary dilation; liver transplant evaluation; portopulmonary hypertension; pulmonary hypertension medical therapy.

Figure 1:

Pathophysiology of Hepatopulmonary Syndrome (A) and Portopulmonary Hypertension (B). ET: endothelin 1; TNF-alpha: tumor necrosis factor- alpha; IL-6: interleukin-6; NO: nitrous oxide; VEGF: vascular endothelial growth factor; CO: carbon monoxide; AV: arteriovenous; V-Q mismatch: ventilation-perfusion mismatch; R -> L: right to left. Figure made using BioRender graphics.

Figure 2:

Work-up for Hepatopulmonary Syndrome (HPS). Portal HTN: portal hypertension; LT: liver transplant; TTE: transthoracic echocardiography; IPVD: intrapulmonary vascular dilation; ABG: arterial blood gas; A-a gradient: alveolar-arterial oxygen gradient; PaO2: partial pressure of arterial oxygen; MELD: model for end-stage liver disease.

Figure 3:

Work-up for Portopulmonary Hypertension (PoPH). Portal HTN: portal hypertension; LT: liver transplant; TTE: transthoracic echocardiography; PAH: pulmonary arterial hypertension; mPAP: mean pulmonary artery pressure; PCWP: pulmonary capillary wedge pressure; PVR: pulmonary vascular resistance; CI: cardiac index; WHO II-IV: World Health Organization functional class II-IV; RVSP: right ventricular systolic pressure; RV: right ventricle; ePVR: estimated pulmonary vascular resistance; ERS: European Respiratory Society