Averaged decrease in SpO2 during six-minute walk test as a novel prognostic marker for elderly heart failure patients

Abstract Background: Exercise capacity is pivotal in risk stratification in heart failure (HF) and the six-minute walk test (6MWT) is often employed to evaluate it, but estimation of the absolute risk in elderly patients through six-minute walk distance (6MWD) is difficult due to comorbidities resulting in wide variability among individuals, implicating unmet-needs for comprehensive index for exercise capacity in the elderly. Methods: During the 6MWT, 6MWD and exercise-induced changes in peripheral oxygen saturation (ΔSpO₂-Ex) were measured. The associations between these parameters and cardiovascular outcomes, including HF rehospitalization and cardiovascular death within one year after discharge were assessed. Results: Fifty-five HF patients with age > 65 yeas were investigated. The mean 6MWD was 237.5 m, and the mean ΔSpO₂-Ex was 5.8 %. Kaplan-Meier analysis revealed a significant correlation between larger ΔSpO₂-Ex and adverse cardiovascular outcomes (HR 6.66, p<0.001) compared to 6MWD (HR 2.40, p=0.031). In multivariate analysis, ΔSpO₂-Ex was an independent risk factor. The combination of short-6MWD and large-ΔSpO₂-Ex identified patients with markedly high incidence rate of cardiovascular events. Conclusions: ΔSpO₂-Ex could be an independent prognostic marker for HF patients, surpassing the predictive power of 6MWD, suggesting that the 6MWT can provide a novel prognostic assessment that reflects exercise capacity through ΔSpO₂-Ex.