Bending oxygen saturation index and risk of worsening heart failure events in chronic heart failure

Aims: Bendopnea is a clinical symptom of advanced heart failure with uncertain prognostic value. We aimed to evaluate whether bendopnea and the change in oxygen saturation when bending forward (bending oxygen saturation index [BOSI]) are associated with adverse outcomes in ambulatory chronic heart failure (CHF) patients.

Methods and results: We prospectively evaluated 440 subjects with symptomatic CHF. BOSI was defined as the difference between sitting and bending oxygen saturation (SpO₂ ). The endpoint was the total number of worsening heart failure (WHF) events (heart failure hospitalization or urgent heart failure visit requiring parenteral diuretic therapy). The mean age was 74 ± 10 years, 257 (58.6%) were male, and 226 (51.4%) had a left ventricular ejection fraction <50%. Bendopnea was present in 94 (21.4%) patients, and 120 (27.3%) patients had a BOSI ≥-3%. The agreement between BOSI ≥-3% and bendopnea was moderate (Gwet's AC 0.482, p < 0.001). At a median (p25%-p75%) follow-up of 2.17 years (0.88-3.16), we registered 441 WHF events in 148 patients. After multivariable adjustment, BOSI was independently associated with the risk for total WHF episodes (overall, p < 0.001). Compared to improvement/no change in SpO₂ when bending (BOSI 0%), those with BOSI ≥-3% showed an increased risk of WHF events (incidence rate ratio [IRR] 2.16, 95% confidence interval [CI] 1.67-2.79; p < 0.001). In contrast, bendopnea was not associated with the risk of total WHF episodes (IRR 1.04, 95% CI 0.83-1.31; p = 0.705).

Conclusions: In ambulatory and stable CHF patients, BOSI ≥-3% and not bendopnea was independently associated with an increased risk of total (first and recurrent) WHF episodes. Awareness of SpO₂ while assessing bendopnea may be a useful tool for predicting heart failure decompensations.