Six-minute walk distance predicts mortality in liver transplant candidates

Abstract

The 6-minute walk distance (6MWD) is a simple test measuring global physical function. It is commonly used to predict mortality in patients with cardiac and pulmonary diseases, but it is also useful in assessing the functional status of patients with a variety of other medical conditions. We sought to determine (1) the characteristics of the 6MWD in patients listed for liver transplantation (LT), (2) the existence of a relationship between the 6MWD and the quality of life, and (3) the relationship between the 6MWD and survival in LT candidates. The 6MWD was prospectively measured in all patients listed for LT. The 6MWD was determined when the listed Model for End-Stage Liver Disease (MELD) score was ≥ 15. Patients were followed until LT, death, removal from the wait list, or the end of the study period. Quality of life was assessed with the Short Form 36 (SF-36). In 121 patients, the mean 6MWD was 369 ± 122 m; it was not related to age, height, weight, body mass index, albumin level, or etiology of liver disease and showed a moderate correlation with the physical component score (PCS) on the SF-36 (r = 0.4) and a moderate inverse correlation with the native MELD score (r = -0.61). In an unadjusted analysis, a high native MELD score, a low 6MWD, and a low PCS were associated with mortality, with only the 6MWD retaining significance after adjustment for covariates. Each 100-m increase in the 6MWD was significantly associated with increased survival (hazard ratio = 0.48, P = 0.0001), with 6MWD < 250 m being associated with an increased risk of death (P = 0.0001). In conclusion, the 6MWD is significantly reduced in patients awaiting LT and is inversely correlated with the native MELD score. A pretransplant 6MWD < 250 m is a risk for death on the wait list.