Association of hypoxic burden metrics with cardiovascular outcomes in heart failure and sleep‐disordered breathing

AIMS: Heart failure (HF) and sleep‐disordered breathing (SDB) frequently coexist. We aimed to compare the prognostic value of different nocturnal hypoxic burden metrics in hospitalized HF patients. METHODS AND RESULTS: HF patients underwent polygraphy screening for SDB in this prospective cohort. Hypoxic burden metrics assessed using pulse oximetry included time < 90% oxygen saturation (T90), proportion of total recording time < 90% oxygen saturation (TRT90), oxygen desaturation index (ODI), and mean oxygen saturation (meanSO(2)). The prespecified endpoints were the composite of cardiovascular death or admission for worsening HF. This study included 764 hospitalized HF patients, 16.5% and 36.6% of whom had obstructive and central sleep apnoea, respectively. With a median follow‐up time of 2.2 years, endpoint events occurred in 410 (53.7%) patients. In univariate and multivariate analyses, T90, TRT90, and meanSO(2) were substantially associated with the composite outcome, whereas ODI was not. After multivariate Cox model adjustment, patients with 5.0 ≤ T90 ≤ 52.0 min [hazard ratio (HR) 1.32, 95% confidence interval (CI): 1.02–1.71, P = 0.034] or T90 > 52.0 min (HR 1.56, 95% CI: 1.21–2.02, P = 0.001) had a greater risk of the composite outcome than those with T90 < 5.0 min. The TRT90 and T90 results were similar. Compared with meanSO(2) > 95%, meanSO(2) < 93% (HR 1.47, 95% CI: 1.16–1.88, P = 0.002) was correlated with adverse outcomes. CONCLUSIONS: The hypoxic burden metrics T90, TRT90, and meanSO(2), but not ODI, were independent predictors of cardiovascular death or readmission for worsening HF. Indicators of duration and severity, not just the frequency of nocturnal hypoxaemia, should be valued and considered for intervention to improve outcomes in HF patients.