Coronary flow reserve (CFR), ratio of maximal myocardial blood flow (MBF) during pharmacologically induced coronary vasodilation to resting MBF, is an integrated measure of flow through both the large epicardial coronary arteries and the microcirculation. CFR has been proposed as an indirect parameter to evaluate the function of the coronary microcirculation, and its impairment is a strong predictor of cardiovascular mortality.

Rubidium PET-computed tomography scanner, the gold standard method to evaluate CFR is not available in France. We aimed to assess cardiac microcirculation using MRI myocardial perfusion in diabetic patients.

Using semi-quantitative analysis by MRI, we estimated CFR by the Myocardial Perfusion Reserve Index (MPRI), ratio between perfusion signal (maximal upslope) with adenosine stress and rest of myocardial segments in 27 diabetic patients without coronary artery disease perfectly phenotype for microangiopathy (eye, kidney, nerve). MPRI was analyzed according to the presence of extra cardiac microangiopathy.

This technique is feasible with routine MRI protocols. Reproducibility was very good: 99 myocardial segments analyzed by 2 independent observers: MPRI 2.2±0.76 vs. 2.24±0.8; mean of differences: − 0.033 IC95% [−0.13; 0.07]. MPRI was lower in the group of diabetic patients with extra-cardiac microangiopathy (n=11) as compared to the group without (n=16): 2.01±0.78 vs. 2.31±0.7, P=0.51, not statistically significant because of the modest number of patients. CFR was significantly altered in myocardial segments analyzed in diabetics with microangiopathy (n=150) as compared to myocardial segments from diabetics without microangiopathy (n=192): 1,99±0.83 vs. 2.35±0.98 P<0.002.

Semi quantitative analysis of CFR is feasible in a daily routine after stress MRI. Preliminary result in diabetic patients suggests a strong link between microangiopathy and a decrease in CFR.