Novel Markers Derived from Oxygenation-Sensitive Cardiac Magnetic Resonance Images in Metabolic Syndrome. (RF_FR_295)

Metabolic Syndrome (MetS) is a cluster of modifiable risk factors strongly associated with atherosclerosis (1). Individuals with MetS exhibit a heterogeneous coronary vascular response to breathing maneuvers, assessed using the Breathing-induced Myocardial Oxygenation Reserve (B-MORE), with several biomarkers derived from end-systolic oxygenation-sensitive cardiac magnetic resonance (OS-CMR) images (2,3). Novel software allows for analyzing all post-hyperventilation breath-hold images, rather than two traditionally used to derive B-MORE. Previous studies in heart failure showed a strong diagnostic potential for the heterogeneity of the response (4). The objective of this study was to evaluate myocardial oxygenation across the cardiac cycle including heterogeneity as a marker for coronary vascular function in individuals with MetS.



Methods:

We performed a single-center observational study of healthy adults and individuals with MetS, sex- and age-matched by decade. Subjects underwent an OS-CMR scan (3T Signa Premier, GE Healthcare) with vasoactive breathing maneuvers. Breath-hold images were identified by a reader blinded to patient status, and myocardial contours were drawn using an automated software prototype (Area19 Medical Inc). Signal intensity parameters normalized to the signal of the left ventricular blood pool were derived using MATLAB. Signal intensity heterogeneity was measured using neighbourhood standard deviation, which quantifies the variability of pixel intensities within the local area surrounding each pixel. Mann-Whitney tests were used to compare signal intensity between cases and controls, correcting for multiple comparisons.



Results:

Myocardial oxygenation was assessed in 54 healthy controls (25 female, mean age 55.7±9.9) and 54 individuals with MetS (25 female, mean age 56.5±9.3). Heterogeneity was significantly lower in the control group compared to MetS (3.6±1.2 vs 4.7±1.8, p=0.002) (Figure 1). Across the entire breath-hold, maximum signal intensity was significantly increased in controls (11.9±3.2) compared to cases (10.6±2.7) (p=0.034), as was the range of signal intensity values (7.95±2.7 vs 6.7±2.1, p=0.028) (Figure 2). In the first cardiac cycle of the breath-hold, these parameters were also significantly higher in controls (maximum value: 10.4±2.85 vs 9.4±2.5, p=0.038, range: 5.96±2.0 vs 5.12±1.7, p=0.038).



Conclusion:

This was the first study to investigate myocardial oxygenation across the cardiac cycle in MetS patients. These findings confirm the heterogeneity of coronary vascular function in MetS and support using changes in myocardial oxygenation across the cardiac cycle as a novel, sensitive set of markers for assessing coronary vascular function.