Abstract 3687: Assessment of Endothelial Function in the Forearm with Blood Oxygen Level-Dependent Magnetic Resonance Imaging
Background: Blood Oxygen Level-Dependent Magnetic Resonance Imaging (BOLD-MRI) sensitively detects changes of blood flow, blood volume, and oxygenation.
Objective: To assess endothelial function with BOLD-MRI during reactive hyperemia in the human forearm and compare the results with ultrasound assessment of Flow Mediated Dilation (FMD) as the current gold standard of endothelial function assessment.
Methods: In 15 healthy male volunteers, BOLD-MRI signal intensity (SI) in the forearm musculature was continuously measured during reactive hyperemia after an upper arm occlusion for 5 minutes. The area under the curve of the SI changes during reactive hyperemia (AUC-BOLD) was used as a marker for endothelial function. Endothelial dysfunction was induced with a reperfusion injury after sustained (15 minutes) arterial occlusion of the brachial artery and endothelial function was reassessed after 15 min.. The same protocol was repeated with an ultrasound assessed FMD test on a different day. For reproducibility assessment 7 of the volunteers underwent MR examination on a second day.
Results: AUC-BOLD during reactive hyperemia averaged 7.6 %s ±1.3 and was significantly reduced to 4.8 %s ±1.9 after reperfusion injury (mean difference 2.8, SEM 0.5, p<0.001). Also FMD was reduced by reperfusion injury from 9.2% ±4.2 to 4.6% ±3.6 (mean difference 4.6%, SEM 1.1, p<0.01), whereas maximum flow-increase in the brachial artery and maximum BOLD-SI increase during reactive hyperemia remained unchanged. The correlation between FMD and AUC-BOLD on an individual basis was significant but weak (r2=0.27, p=0.007). Using a threshold of 5.6 %s, AUC-BOLD accurately detected endothelial dysfunction induced by a reperfusion injury (sensitivity 86%, specificity 100%). The coefficient of variability for a repeated assessment of AUC-BOLD on a second day was 7.6% and slightly below what is reported for FMD.
Conclusion: BOLD-MRI offers a new option to assess endothelial function with good reproducibility and complementary information to ultrasound assessed FMD, since it mainly assesses the microvasculature. In addition it can potentially be applied in other vascular beds such as the heart.