Abstract P2136: Prognostic Value of the Six-Minute Walk Test in Patients with Hypertrophic Cardiomyopathy

Abstract

Background: The six-minute walk test (6MWT) is a simpler, safer, and more cost-effective measure of functional capacity than cardiopulmonary exercise testing (CPET) and can be used for risk stratification of several cardiovascular diseases. However, there are no data on the prognostic value of the 6MWT in hypertrophic cardiomyopathy (HCM). Objective: To investigate the prognostic value of the 6MWT in HCM and determine whether it can be used as an alternative to CPET. Methods: A total of 534 patients with HCM were prospectively recruited to undergo both 6MWT and CPET. The endpoint of this study was major adverse cardiovascular events (MACE, a composite of cardiovascular death, heart failure, aborted sudden cardiac death, and stroke). The associations of the 6MWT with MACE were investigated using survival analyses, and the ability of 6MWT and CPET parameters to predict MACE were compared. Results: Four hundred and ninety-six patients with HCM who had complete follow-up data available were included. The mean age was 46.8 years, and 69.1% were male. The 6MWT distance correlated significantly with peak VO 2 on CPET (r=0.328, P<0.001). Thirty-eight patients had MACE during a median follow-up of 2.7 years. A shorter 6MWT distance was independently associated with a higher risk of MACE (per 100-m decrease, hazard ratio 1.755, P=0.003) after adjusting for covariables. The association between peak VO 2 and MACE was also determined (per 1 mL/min/kg decrease, hazard ratio 1.102, P=0.044). The ability of the 6MWT distance to predict MACE was not significantly different from that of peak VO 2 (C-statistic, 0.643 vs 0.616). The optimal cutoff value of the 6MWT distance was identified as 423 m. Addition of the 6MWT distance (as a dichotomous variable) to the adjusted Cox model with clinical and demographic covariables significantly improved the ability of the model to predict MACE (C-statistic, 0.791 vs. 0.731, P=0.038), while addition of peak VO 2 did not improve the prediction performance of the model (C-statistic, 0.754 vs. 0.731, P=0.346). Conclusions: Poor performance on the 6MWT was an independent risk factor for MACE in patients with HCM. The 6MWT distance provided additional prognostic discrimination beyond conventional covariables when compared with peak VO 2 . These findings suggest that the 6MWT not only serves as an alternative to CPET but has greater clinical value, highlighting the importance of routine 6MWT to assess functional capacity in patients with HCM.