Estimating coronary sinus oxygen saturation from pulmonary artery oxygen saturation

Background and Objectives: Coronary sinus oxygen saturation is a useful indicator of health and disease states. However, it is not routinely used in clinical practice. Cardiovascular magnetic resonance imaging (CMR) oximetry can accurately estimate oxygen saturation in the pulmonary artery. This research aimed to provide a method for calculating coronary sinus oxygen saturation (ScsO2) from pulmonary artery oxygen saturation (SpaO2) that could be applied to CMR. Materials and Methods: A systematic literature review was conducted to identify prior work that included invasive measures of ScsO2 and either SpaO2 or right ventricular oxygen saturation. This revealed one study with appropriate data (ScsO2 and SpaO2 measurements, n = 18). We then carried out agreement and correlation analyses. Results: Regression analysis demonstrated a statistically significant, positive relationship between ScsO2 and SpaO2, giving a regression equation of ScsO2 = −31.198 + 1.062 × SpaO2 (r = 0.76, p < 0.001). A multivariable regression analysis of all reported variables, excluding SpaO2, independently identified superior vena cava oxygen saturation (SsvcO2) and arterial oxygen saturation (SaO2) as predictors of ScsO2 (r = 0.78, p < 0.001), deriving the equation ScsO2 = −452.8345 + 4.3579 × SaO2 + 0.8537 × SsvcO2. Conclusions: In this study, we demonstrated a correlation between coronary sinus oxygen saturation and pulmonary artery oxygen saturation, allowing the estimation of ScsO2 from SpaO2. This association enables the estimation of ScsO2 from purely CMR-derived data. We have also described a second model using arterial and superior vena cava saturation measurements, providing an alternative method. Future validation in larger, independent cohorts is needed.