Abstract Body (Do not enter title and authors here): Introduction: Non-invasive estimation of blood oxygen saturation (O2sat) by cardiac magnetic resonance (CMR) has clinical application in single ventricle heart disease. A T2-mapping based CMR method has been described to estimate O2sat in the heart and great vessels in specific regions of interest. This study builds on our prior validation of CMR oximetry maps to visualize O2sat data and determine optimal regions for evaluation in single ventricle hearts.

Methods: 14 single ventricle (age 17.1±6.8 years, 4 female) and 15 transplant control (age 16.6±4.6 years, 6 female) patients undergoing clinically indicated cardiac catheterization and CMR were recruited in a tertiary care children’s hospital. A series of T2-prepared single-shot steady-state free-precession images were acquired of intracardiac chambers and great vessels in free-breathing across T2-preparation times of 0 to 200 ms (Fig 1). Inter-echo spacing (τ) ranged from 0 to 25 ms. Color-coded maps were calculated representing estimated O2sat based on voxel-wise fitting of T2 data to the Luz-Meiboom model (S,T,τ,α). Regional O2sat from oximetry maps were compared to corresponding invasive catheterization data.

Results: Oximetry maps allowed visualization of O2sat to identify regions with uniform blood pools and with heterogenous O2sat (Fig 2). Correlation between O2sat via oximetry maps and catheterization were favorable overall (r=0.69, p<0.001), in single ventricle patients (r=0.70, p<0.001) and in transplant patients (r=0.69, p<0.001). Bland Altman plots (Fig 3) comparing O2sat via oximetry maps and catheterization demonstrated reasonable agreement overall (mean difference=-5.2, limits of agreement=-21.4,8.3), in single ventricle patients (mean difference=-4.3, limits of agreement=-22.5,14.0) and in transplant patients (mean difference=-5.6, limits of agreement=-21.0, 9.8). Pulmonary veins, atria, and regions with foreign material were difficult to visualize due to data heterogeneity and noise.

Conclusion: CMR can be utilized for non-invasive estimation of O2sat in complex heart disease with good correlation to current gold standard catheter-derived measurements. Oximetry maps can enhance visualization of regional O2sat and may guide further optimization of image acquisition and analysis. Streaming effects in human hearts altered by palliation surgeries may explain why oximetry maps visually depicted heterogenous O2sat. Ongoing patient recruitment is warranted.