Exercise-induced oxygen desaturation identifies early post-discharge risk in patients with heart failure
I Sunayama, K Min, Y Orihara, K Shimizu, S Hayashi, J Ono, A Daimon, M Oboshi, E Manabe, A Eguchi, M Asakura, M IshiharaAbstract
Background
Early rehospitalization after discharge represents a vulnerable period in patients with heart failure (HF) and remains a major unmet clinical challenge. We have previously demonstrated that exercise-induced oxygen desaturation (ΔSpO₂-Ex), assessed by the 6-minute walk test (6MWT), predicts long-term outcomes in HF. Whether ΔSpO₂-Ex can also predict early post-discharge outcomes has not been established.
Purpose
To investigate the prognostic value of ΔSpO₂-Ex for predicting short-term (90-day) clinical outcomes in patients with HF.
Methods
In a prospective observational study, 82 patients hospitalized for acute HF underwent a standardized 6MWT prior to discharge. Peripheral oxygen saturation (SpO₂) was continuously monitored during the 6MWT. ΔSpO₂-Ex was defined as the difference between maximum resting SpO₂ and the mean SpO₂ during the 6MWT. Patients were followed for 90 days for a composite endpoint of HF rehospitalization or cardiovascular death. Associations between ΔSpO₂-Ex and outcomes were assessed using Cox proportional hazards models.
Results
The mean age was 78.4 years, and 48% were female. The mean left ventricular ejection fraction (LVEF) was 46.7%, and the median NT-proBNP level was 2124 pg/mL. The median ΔSpO₂-Ex was 4.2%, and patients were stratified into small (<4.2%) and large (≥4.2%) ΔSpO₂-Ex groups accordingly. Kaplan–Meier analysis demonstrated early and sustained separation of event-free survival curves, with significantly higher event rates in the large ΔSpO₂-Ex group (HR 4.80; 95% CI 1.37–16.85; p=0.014). When analyzed as a continuous variable, ΔSpO₂-Ex remained strongly associated with outcomes; each 1% increase in SpO₂ decline was associated with a 13% higher risk of the composite endpoint (HR 1.13; 95% CI 1.04–1.22; p=0.002). This association remained significant after adjustment for age, 6-minute walk distance, LVEF, or NT-proBNP.
Conclusions
ΔSpO₂-Ex serves as a prognostic marker for early post-discharge outcomes in patients with HF. In addition to its previously reported association with long-term prognosis, exercise-induced oxygen desaturation provides clinically actionable information for short-term risk stratification and may help identify patients who require intensified follow-up and management after hospital discharge.Kaplan–Meier analysis of 90-day outcomesFor image description, please refer to the figure legend and surrounding text.