Abstract 17908: Regional Gradient of Blood Oxygen Level Dependant Cardiovascular MR (BOLD-CMR) in Patients with Coronary Artery Disease: A Comparative Study with Fractional Flow Reserve

Abstract

Background BOLD-CMR exploits the inherent magnetic property of hemoglobin with the signal intensity (SI) being dependent on its oxygenation status. As ischemic damage occurs primarily in the subendocardium, we hypothesized that this technique can be used to detect a transmural oxygenation gradient in patients with coronary artery disease (CAD).

Methods Patients scheduled for clinically-indicated coronary angiography (n=18, mean age 60.6±9.9 yrs) and healthy controls (n=11, mean age 29±4 yrs) were scanned using a 1.5T MRI system. BOLD-CMR was performed at rest and during adenosine-induced vasodilation. Change in BOLD signal intensity was calculated for the sub-epicardial and -endocaridal regions. In patients, segmental analysis was compared with the fractional flow reserve (FFR) and quantitative coronary angiography (QCA). An FFR cutoff of 0.80 defined significant coronary artery stenosis.

Results CAD patients had overall reduced response to hyperemia across the whole myocardium. There was no transmural gradient to the BOLD SI in healthy subjects, whereas CAD patients had significantly different responses in the subepicardium versus the subendocardium in all segments, regardless of the FFR. Response in segments subtended by coronaries with an abnormal FFR had further reduced BOLD SI change upon hyperemia and an even more significant difference transmurally. There was no significant correlation between the subepicardial or subendocardial BOLD SI change and percent stenosis as measured by QCA.

Conclusion BOLD-CMR can distinguish regional changes in oxygenation present in CAD patients and not present in healthy subjects. Segments subtended by normal FFR values also exhibited regional changes, demonstrating the presence of abnormal oxygenation despite no functionally significant limiting stenoses. BOLD-CMR provides a non-invasive transmural assessment of myocardial oxygenation and may prove to be a sensitive tool for detection of ischemia.