Impact of regional functional ischemia on global coronary flow reserve in patients with stable coronary artery disease

Background: Global coronary flow reserve (g-CFR) provides powerful prognostic information. The relationship between g-CFR and the regional physiological indices of fractional flow reserve (FFR), coronary flow reserve (r-CFR), and the index of microcirculatory resistance remains undetermined. This study aimed to assess the relationship between regional and global physiological indices and determinants of cardiovascular magnetic resonance imaging (CMR)-derived g-CFR. Methods: A total of 151 patients with single de novo intermediate to stenotic epicardial lesions referred for diagnostic invasive coronary angiography who underwent phase-contrast tine CMR of the coronary sinus (CS) were included. g-CFR was calculated as the ratio of hyperemic and resting CS flow (CSF). Regional and global physiological parameters were compared, and determinants of g-CFR were assessed. Results: There was a weak linear relationship between FFR and g-CFR (R-2 = 0.04, p = 0.013), while r-CFR and g-CFR, or combinations of the other regional-global indices were not significantly correlated. When patients were divided into two groups by FFR of 0.80, there were also no significant differences in global physiological indices between the groups (FFR <= 0.80 vs. FFR > 0.80; g-CFR: 2.73 vs. 2.61, p = 0.48; hyperemic CSF: 3.32 vs. 3.52 ml/min/g, p = 0.84). Higher high-sensitivity cardiac troponin-1(hs-cTnI) and higher resting CS flow were independently associated with impaired g-CFR, and the combination could efficiently identify patients with g-CFR < 2.0. Conclusions: Given weak relationship among global and regional physiological indices, these indices may provide complementary efficacy for prognostication in patients with single-vessel stable coronary artery disease. Combination of hs-cTnl and resting CS flow could estimate g-CFR without pharmacological hyperemic induction. (C) 2018 Japanese College of Cardiology. Published by Elsevier Ltd. All rights reserved.