Quantitative relationship between the extent and morphology of coronary atherosclerotic plaque and downstream myocardial perfusion

Objectives: The purpose of this study was to quantify the effects of coronary atherosclerosis morphology and extent on myocardial flow reserve (MFR).

Background: Although the relationship between coronary stenosis and myocardial perfusion is well established, little is known about the contribution of other anatomic descriptors of atherosclerosis burden to this relationship.

Methods: We evaluated the relationship between atherosclerosis plaque burden, morphology, and composition and regional MFR (MFR(regional)) in 73 consecutive patients undergoing Rubidium-82 positron emission tomography and coronary computed tomography angiography for the evaluation of known or suspected coronary artery disease.

Results: Atherosclerosis was seen in 51 of 73 patients and in 107 of 209 assessable coronary arteries. On a per-vessel basis, the percentage diameter stenosis (p = 0.02) or summed stenosis score (p = 0.002), integrating stenoses in series, was the best predictor of MFR(regional). Importantly, MFR(regional) varied widely within each coronary stenosis category, even in vessels with nonobstructive plaques (n = 169), 38% of which had abnormal MFR(regional) (<2.0). Total plaque length, composition, and remodeling index were not associated with lower MFR. On a per-patient basis, the modified Duke CAD (coronary artery disease) index (p = 0.04) and the number of segments with mixed plaque (p = 0.01) were the best predictors of low MFR(global).

Conclusions: Computed tomography angiography descriptors of atherosclerosis had only a modest effect on downstream MFR. On a per-patient basis, the extent and severity of atherosclerosis as assessed by the modified Duke CAD index and the number of coronary segments with mixed plaque were associated with decreased MFR.