6 minute walk work and other clinical correlates of peak VO2 in pulmonary vascular disease

Background: Peak VO2 is the gold standard for assessing exercise capacity but 6 minute walk distance (6MWD) is mostly used surrogate measure. However, body mass may influence the predictive ability of 6MWD. Hence, 6 minute walk work (6MWW=6MWD X bodyweight) is an alternative measure but has not been fully investigated in all pulmonary vascular disease (PVD) groups. Aims: In PVD patients; 1) To determine whether 6MWW and/or other clinical parameters correlate with peak VO2. 2) Investigate the ability to predict peak VO2 from other measures, such as 6MWW. Method: Clinical data was retrospectively analysed from 38 chronic thromboembolic pulmonary hypertension (CTEPH),41 chronic thromboembolic disease (CTED), and 13 pulmonary hypertension (PH) patients. 6MWD, 6MWW, lung function, echocardiogram and right heart catheter (RHC) data were correlated with peak VO2. Results: A number of 6 minute walk measures, lung function, RHC and echocardiogram parameters correlated to peak VO2. Amongst the PVD groups 6MWW and TLCO were the highest correlated to peak VO2 (Table 1). Following linear regression analysis a predictive equation was produced in CTEPH and CTED groups. CTEPH=VO2 (ml/min) = - 252 + 0.049*6MWW (R2 = 0.79) CTED=VO2 (ml/min) = - 266 + 0.028*6MWW + 147.6*TLCO (adjusted R2 = 0.78). Conclusion: 6MWW is highly correlated to peak VO2 in PVD suggesting body mass does influence the predictive power of 6MWD. Further work is needed to validate the generated predicted equations.