Resting coronary flow estimated by dynamic coronary CT angiography: Potential for use in the detection of plaque burden and myocardial ischemia

Purpose We propose a resting coronary flow index (rCFI) estimated by dynamic coronary CT angiography (CCTA) for potential use in detecting coronary plaque burden and myocardial ischemia. Materials and Methods A total of 124 patients with stable coronary artery disease (CAD) who underwent CCTA were prospectively enrolled in this study. The original data set of dynamic CCTA with continuous 8 to 12 cardiac cycles was interpolated to 24 to 36 image sets using the motion coherence image processing. Using the maximum slope method, rCFI was defined as the ratio of the maximum upslope in the attenuation of distal coronary artery to that of the ascending aorta. Coronary plaques were classified as non-calcified or calcified based on the presence or absence of low attenuation plaque. For patients who may need additional functional assessment, additional stress/rest myocardial perfusion scintigraphy (MPS) was performed. Results rCFI for vessels with non-calcified plaques was significantly lower than that for normal arteries (0.73 ± 0.23 vs. 0.88 ± 0.22, p < 0.00001). In limited intermediate stenosis, a similar significant difference was observed between the two groups (0.76 ± 0.23 vs. 0.89 ± 0.20, p < 0.0001). In contrast, no significant decrease in rCFI was observed between normal and calcified plaques (0.81 ± 0.28). rCFI for ischemia depicted by MPS was significantly lower than for non-ischemia (0.63 ± 0.24 vs. 0.84 ± 0.19, p < 0.05). The use of the optimal cutoff could detect ischemia, with a C-static value of 0.73, 53% sensitivity, and 93% specificity. Conclusion rCFI can be used for the detection of plaque burden and myocardial ischemia in CAD.