The relationship between mixed venous blood oxygen saturation and pulmonary arterial and venous pressures in patients with heart failure

Abstract

Recent discoveries have identified intrapulmonary bronchopulmonary anastomoses (IBAs) as a relatively common phenomenon forming intrapulmonary right-to-left shunts. This study hypothesizes that IBAs play a significant role in the pathophysiology of heart failure. We aim to investigate the impact of these intrapulmonary right-to-left shunts on pulmonary arterial and venous pressures in heart failure patients, utilizing mixed venous oxygen saturation (SvO₂) as a key measurement. This study included 237 patients with heart failure who underwent cardiac catheterization. The relationships between SvO₂ and pulmonary artery systolic pressure (sPAP), pulmonary artery wedge pressure (PAWP), and left ventricular end-diastolic pressure (LVEDP) were examined using various statistical methods (single regression analysis, partial correlation analysis, structural equation modeling, and Bayesian estimation). All statistical methods that we performed showed that SvO₂ was significantly and negatively correlated with both sPAP and PAWP (p < 0.01, respectively). However, SvO₂ did not significantly correlate with LVEDP. These results suggest that a decrease in SvO₂ leads to an increase in PAWP and sPAP, while LVEDP is only passively influenced by PAWP. This phenomenon likely reflects the impact of an intrapulmonary right-to-left shunt caused by IBAs. The decrease in SvO₂ causes an increase in sPAP and may also cause an increase in PAWP via IBAs.

Keywords: heart failure; intrapulmonary bronchopulmonary anastomose; mixed venous blood oxygen saturation; pulmonary arterial pressure; pulmonary venous pressure.

FIGURE 1

Regression analysis showing the correlation between SvO₂ and sPAP, PAWP, and LVEDP. A significant negative correlation is found between SvO₂ and sPAP (a) and PAWP (b), but not with LVEDP (c). About (a) and (b), the dotted curves that exist above and below the regression line represent 95% confidence intervals. LVEDP, left ventricular end‐diastolic pressure; PAWP, pulmonary artery wedge pressure; sPAP, pulmonary artery systolic pressure; SvO₂, mixed venous blood oxygen saturation.

FIGURE 2

Structural equation modeling and Bayesian estimation. This path diagram in (a) shows the effect of SvO₂ on sPAP, PAWP, and LVEDP. Standardized coefficients, squared coefficients of multiple correlations (in italics), and correlation coefficients of the exogenous variables (in square brackets) are shown. SvO₂ is significantly correlated with sPAP and PAWP (p < 0.001, respectively), but not with LVEDP (p = 0.523). Additionally, e1, e2, and e3 are significantly correlated (p < 0.001). The results of Bayesian estimation in (b) using Amos Graphics are shown in a two‐dimensional contour image. From the center of the figure, the three colors are black, dark gray, and light gray, where black represents 95%; dark gray, 90%; and light gray, 50% confidence intervals. It is visually clear from this figure that the effects of SvO₂ on sPAP and PAWP are in the negative range, far from zero, strongly suggesting a negative effect on both (A); however, the effect of SvO₂ on LVEDP is on zero line, suggesting no effect on LVEDP (B, C). LVEDP, left ventricular end‐diastolic pressure; PAWP, pulmonary artery wedge pressure; sPAP, pulmonary artery systolic pressure; SvO₂, mixed venous blood oxygen saturation.