Non-invasive fractional flow reserve in vessels without severe obstructive stenosis is associated with coronary plaque burden

Aims: Non-invasive fractional flow reserve derived from coronary CT angiography (FFRCT) has been shown to be predictive of lesion-specific ischemia as assessed by invasive fractional flow reserve (FFR). However, in practice, clinicians are often faced with an abnormal distal FFRCT in the absence of a discrete obstructive lesion. Using quantitative plaque analysis, we sought to determine the relationship between an abnormal whole vessel FFRCT (V-FFRCT) and quantitative measures of whole vessel atherosclerosis in coronary arteries without obstructive stenosis. Methods: FFRCT was calculated in 155 consecutive patients undergoing coronary CTA with >= 25% but less than 70% stenosis in at least one major epicardial vessel. Semi-automated software was used to quantify plaque volumes (total plaque [TP], calcified plaque [CP], non-calcified plaque [NCP], low-density non-calcified plaque [LD-NCP]), remodeling index [RI], maximal contrast density difference [CDD] and percent diameter stenosis [% DS]. Abnormal V-FFRCT was defined as a minimum value of <= 0.75 across the vessel (at the most distal region where FFRCT was computed). Results: Vessels with abnormal V-FFRCT had higher per-vessel TP (554 vs 331mm(3)), CP (59 vs 25mm(3)), NCP (429 vs 295mm(3)), LD-NCP (65 vs 35mm(3)) volume and maximum CDD (21 vs 14%) than those with normal VFFRCT (median, p < 0.05 for all). Using a multivariate analysis to adjust for CDD and % DS, all measures of plaque volume were predictive of abnormal V-FFRCT (OR 2.09, 1.36, 1.95, 1.95 for TP, CP, NCP and LD-NCP volume, respectively; p < 0.05 for all). Conclusion: Abnormal V-FFRCT in vessels without obstructive stenosis is associated with multiple markers of diffuse non-obstructive atherosclerosis, independent of stenosis severity. Whole vessel FFRCT may represent a novel measure of diffuse coronary plaque burden.