Cerebral desaturation in heart failure: Potential prognostic value and physiologic basis

Cerebral tissue oxygen saturation (SctO(2)) reflects cerebral perfusion and tissue oxygen consumption, which decline in some patients with heart failure with reduced ejection fraction (HFrEF) or stroke, especially during exercise. Its physiologic basis and clinical significance remain unclear. We aimed to investigate the association of SctO(2) with oxygen transport physiology and known prognostic factors during both rest and exercise in patients with HFrEF or stroke. Thirty-four HFrEF patients, 26 stroke patients, and 17 healthy controls performed an incremental cardiopulmonary exercise test using a bicycle ergometer. Integrated near-infrared spectroscopy and automatic gas analysis were used to measure cerebral tissue oxygenation and cardiac and ventilatory parameters. We found that SctO(2) (rest; peak) were significantly lower in the HFrEF (66.3±13.3%; 63.4±13.8%,) than in the stroke (72.1±4.2%; 72.7±4.5%) and control (73.1±2.8%; 72±3.2%) groups. In the HFrEF group, SctO(2) at rest (SctO(2rest)) and peak SctO(2) (SctO(2peak)) were linearly correlated with brain natriuretic peptide (BNP), peak oxygen consumption ([Image: see text] ), and oxygen uptake efficiency slope (r between -0.561 and 0.677, p < 0.001). Stepwise linear regression showed that SctO(2rest) was determined by partial pressure of end-tidal carbon dioxide at rest (P(ET)CO(2rest)), hemoglobin, and mean arterial pressure at rest (MAP(rest)) (adjusted R = 0.681, p < 0.05), while SctO(2peak) was mainly affected by peak carbon dioxide production ([Image: see text] ) (adjusted R = 0.653, p < 0.05) in patients with HFrEF. In conclusion, the study delineates the relationship of cerebral saturation and parameters associated with oxygen delivery. Moreover, SctO(2peak) and SctO(2rest) are correlated with some well-recognized prognostic factors in HFrEF, suggesting its potential prognostic value.