B106-02 The Incremental Shuttle Walk Test — A Practical Surrogate for VO2 Peak in Pulmonary Hypertension

Abstract Rationale Cardiopulmonary exercise testing (CPET) is the gold standard for assessment of peak exercise capacity. CPET derived VO2 peak is a strong, independent predictor of outcome in pulmonary arterial hypertension (PAH) and improves risk stratification when used in place of 6-minute walk distance in the 4 strata ESC/ERS model1,2. The incremental shuttle walking test (ISWT) is an externally paced, symptom-limited, field walking test that aims to reflect peak exercise capacity3. There are currently only limited data validating the ISWT as a reflection of VO2 peak in PAH4,5. AIM To determine whether the incremental shuttle walk test can serve as a valid surrogate for VO2 peak in PAH and chronic thromboembolic pulmonary hypertension (CTEPH). Methods Consecutive patients from the ASPIRE registry referred to the CPET lab at the Sheffield pulmonary vascular disease unit with a diagnosis of PAH or CTEPH were included. The patient’s most recent ISWT prior to CPET was taken as the comparator. VO2 peak and incremental shuttle walk test distance (ISWTD) were compared with correlation and multivariable linear regression analyses. Results 107 patients, 62% male, mean age 52( +/-15) years were included. 61 (57%) had PAH and 46 (43%) CTEPH. Mean mPAP was 37 (+/-13.7) mmHg, median PVR 4.2 (2.7 - 7) WU, and mean PAWP 10.1 (+/-3.1) mmHg. Mean ISWTD was 498 (+/-257) meters and mean VO2 peak was 17.5 (+/-5.2) ml/kg/min. There was a strong, positive and linear relationship between VO2 peak and ISWTD (Pearson’s r = 0.78, p = 0.001) (figure 1). Linear regression analysis demonstrated that VO2 peak was the principal determinant of ISWTD (R² = 0.607), while adjustment for demographic variables, diagnosis, and haemodynamic severity did not meaningfully increase the explained variance (adjusted R² = 0.603). In this cohort, each 1 mL/kg/min increase in VO2 peak was associated with an approximately 37m greater ISWTD. Conclusions The relationship between VO2 peak and ISWTD was strong and linear across the full range of walking distances. In regression analysis, VO2 peak was the principal determinant of walking distance, explaining approximately 60% of its variance. These findings suggest that the ISWT may serve as a practical field measure of peak aerobic capacity in both PAH and CTEPH. This abstract is funded by: None