In a new study, researchers determined that elevated serum bilirubin levels and a low 6-minute walk distance are predictors of poor prognosis in patients with inoperable chronic thromboembolic pulmonary hypertension. The research — whose findings appear to offer important disease prognosis markers — is titled “Serum Bilirubin and 6-min Walk Distance as Prognostic Predictors for Inoperable Chronic Thromboembolic Pulmonary Hypertension: A Prospective Cohort Study,” and was published in the Chinese Medical Journal.
Chronic thromboembolic pulmonary hypertension (CTEPH) is a rare and severe type of pulmonary hypertension (PH) caused by blood clots in the lungs and characterized by symptoms such as shortness of breath, weakness, fatigue and, potentially, heart failure. Unlike other types of PH, CTEPH is potentially treatable, even curable, with the pulmonary endarterectomy (PEA) procedure. However, a large proportion of patients are deemed inoperable due to severe co-morbidities. In order to develop timely and personalized therapies, risk stratification of CTEPH patients through the identification of prognosis markers is of great importance, but still lacking. Hemodynamic parameters, measured through right heart catheterization, have been explored as predictors of prognosis, but these can only be obtained through an invasive and painful procedure.
In the present study, researchers looked for potential non-invasive prognostic predictors. Their focus was on liver function markers (serum levels of transaminase, GGT, and total bilirubin), as liver dysfunction is a consequence of heart failure due to hepatic congestion caused by increased central venous pressure, and on measurements of exercise capacity using the 6-minute walk test (6MWT or 6MWD, for distance).
The long-term study, from June 2005 to May 2013, enrolled 77 patients with inoperable CTEPH. Baseline clinical characteristics for serum biomarkers of liver function, such levels of aspartate aminotransferase, alanine aminotransferase, GGT, uric acid, and serum bilirubin, and for the 6MWT were determined at enrollment. During the study period, 22 patients died. Regression analyses showed that increased serum concentration of total bilirubin, elevated N-terminal of the prohormone brain natriuretic peptide, decreased 6MWD capacity, and increased central venous pressure and higher pulmonary vascular resistance were all correlated with an increased risk of mortality. Moreover, serum concentrations of total bilirubin and the 6MWT were shown to be independent predicting factors of patient survival.
Due to some study limitations, the researchers suggest the need of further investigation. But, they conclude, “an elevated serum bilirubin level and a poor 6MWD are powerful prognostic predictors for mortality in inoperable CTEPH patients. Measurements of serum bilirubin and exercise capacity may help to identify high-risk patients and predict their outcome.”