Clinical Impact of Intrapulmonary Vascular Dilatation in Candidates for Liver Transplant

Abstract

Background: Intrapulmonary vascular dilatations (IPVD) frequently are detected in patients with liver disease by the delayed appearance of microbubbles at contrast-enhanced echocardiography. IPVD with an elevated alveolar-arterial (A-a) gradient define hepatopulmonary syndrome (HPS); however, the importance of IPVD in the absence of abnormal gas exchange is unknown. We aimed to determine the clinical impact of IPVD in patients with liver disease.

Methods: We performed a cross-sectional study within the Pulmonary Vascular Complications of Liver Disease 2 Study, a multicenter, prospective cohort study of patients being evaluated for liver transplant. We excluded patients with obstructive or restrictive lung disease, HPS, or intracardiac shunting. We compared patients with and those without IPVD.

Results: Forty-six patients with IPVD and 81 patients without IPVD were included. Patients with IPVD were more likely to have autoimmune hepatitis and less likely to have cryptogenic cirrhosis and hepatocellular carcinoma. Patients with IPVD had higher Child-Pugh scores (6 [interquartile range (IQR), 5-7] vs 5 [IQR, 4-7]; P = .04), possibly higher Model for End-Stage Liver Disease scores (14.5 [IQR, 11.6-15.8] vs 12.2 [IQR, 9.4-15.5]; P = .06), higher PaO₂ levels (97.9 [IQR, 92.0-103.0] vs 89.0 [IQR, 82.0-96.9] mm Hg; P < .001), and lower A-a gradients (9.9 [IQR, 6.2-13.5] vs 14.9 [IQR, 9.0-21.8] mm Hg; P < .001). Symptoms and quality of life were similar between the groups.

Conclusions: Autoimmune hepatitis and increased liver disease severity were associated with the presence of IPVD, which was characterized by higher PaO₂ levels. Future studies to better characterize IPVD pathogenesis and the relationship of IPVD to HPS are warranted.

Keywords: hepatopulmonary syndrome; intrapulmonary vascular dilatation; liver transplant.

Figure 1

Selection of study sample. A-a = alveolar-arterial; ABG = arterial blood gas; HPS = hepatopulmonary syndrome; IPVD = intrapulmonary vascular dilatation; PFTs = pulmonary function tests; PPHTN = portopulmonary hypertension; PVCLD2 = Pulmonary Vascular Complications of Liver Disease 2.

Figure 2

Distribution of intrapulmonary shunt severity among patients with intrapulmonary vascular dilatation: 39 patients (84.8%) had a mild degree of intrapulmonary shunting, five patients (10.9%) had moderate intrapulmonary shunting, and two patients (4.3%) had severe intrapulmonary shunting.