Lower six minute walk (6MW) distance has been associated with increased mortality in patients with pulmonary hypertension, idiopathic pulmonary fibrosis (IPF), and COPD. However, there is a paucity of data on the prognostic ability of the 6MW in lung transplantation (LUT) recipients. We sought to determine the association between distance covered during 6MW and mortality in a diverse cohort of LUT recipients.
From 1991 till July 2005, 198 adult LUT were done at our center. The standard 6MW at 6 months post LUT was routinely added as an objective measure in 2000 and distance was measured in meters (m). Patients that survived less than 6 months were excluded from analysis. A historical cohort study was performed. Patients were assembled into quartiles by distance walked and differences between demographic variables were assessed with either the unpaired t test or chi square as appropriate. A regression model was constructed to assess the impact of 6MW distance walked on all-cause mortality, controlling for various confounders. Kaplan Meier survival curves were constructed by quartiles and differences between groups were tested with the Log Rank test.
There were no differences between groups regarding age, gender, race, pre operative diagnosis, SLT vs. BLT, BMI, pre operative RVEF or LVEF, %HTN, %DM and CrCl. Mean distance walked for each quartile: Q1 329 +/− 33m, Q2 390 +/− 19m, Q3 457 +/− 17m, Q4 538 +/− 70m. The logistic regression model showed no impact of either demographics or distance walked on survival. The log rank (Mantel Cox) test yielded a p value 0f 0.083.
Lower distance walked during 6MW at 6 months post LUT is not predictive of all-cause mortality in our cohort of LUT recipients, possibly due to our smaller sample size.
Routine 6MW evaluations in post LUT recipients may not be helpful as a prognostic tool. Further studies are warranted to assess if other features of the 6MW beyond distance walked have prognostic significance.
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