Development and Validation of a Noninvasive Model of Mixed Venous Oxygen Saturation in Heart Failure.

BACKGROUND

Mixed venous oxygen saturation (SvO2), measured with right heart catheterization, is a crucial prognostic tool in patients with heart failure. The prognostic significance of SvO2 estimated noninvasively using cardiovascular magnetic resonance (CMR) from the T2 of intracardiac blood pools remains unknown.

OBJECTIVES

The objective of the study was to develop a CMR model of mixed venous saturation (imaging-derived SvO2 [iSvO2]), and establish if it is associated with future adverse events in heart failure.

METHODS

The iSvO2 was modeled in the discovery cohort (N = 30), who underwent CMR T2 mapping and invasive right heart catheterization, by linear regression. The validation cohort of 628 patients with recently diagnosed heart failure underwent clinical assessment, CMR, and follow-up (median 3 years [IQR: 1.5-4.8]) for a primary endpoint of all-cause mortality or heart failure hospitalization.

RESULTS

Significant positive correlation was found between the ratio of right ventricular blood pool T2/left ventricular blood pool T2 and invasive mixed venous oxygen saturation (R = 0.82; 95% CI: 0.66-0.91; P < 0.001), giving the equation: iSvO2 = 95·(RV-T2BP/LV-T2BP). In the validation cohort, there was a strong association between iSvO2 and the primary endpoint (HR: 0.66 for 10% change in iSvO2; 95% CI: 0.54-0.81; P < 0.001), which remained significant after adjusting for age, sex, left ventricular ejection fraction, right ventricular ejection fraction, N-terminal pro-B-type natriuretic peptide, NYHA functional class, and diabetes.

CONCLUSIONS

The CMR iSvO2, measured from simple T2 maps of left and right ventricular blood pool, allows accurate estimation of the invasive SvO2. In a real-world heart failure registry, iSvO2 is an independent predictor of mortality and heart failure hospitalization.