Impact of ramus coronary artery on computed tomography derived fractional flow reserve (FFRCT ) in no apparent coronary artery disease

Background: The ramus artery contributes to the development of turbulence, which may influence computed tomography (CT) derived fractional flow reserve (FFR CT) even without coronary artery disease (CAD). The relationship between ramus-induced turbulence and FFR CT is unclear. Method and Results: A total of 120 patients with <20% coronary stenosis assessed by both FFR CT and invasive coronary angiography were evaluated. The patients were divided into three groups: absent-ramus (n = 72), small-ramus that could not be analyzed by FFR CT (n = 18), and large-ramus that could be analyzed by FFR CT (n = 30). FFR CT measurements were performed at the proximal and distal segments of the left anterior descending (LAD), left circumflex (LCX), and ramus artery. With absent-ramus and small-absent ramus groups, FFR CT was measured at the distal end of the left main trunk at the same level for the proximal segments of the LAD and LCX. In absent-ramus group, proximal FFR CT showed no significant differences between three vessels (LAD =.96 ±.02; MID =.97 ±.02; LCX =.97 ±.02). However, in small and large-ramus groups, proximal FFR CT was significantly higher in the ramus artery than LAD and LCX (small-ramus, LAD =.95 ±.03, Ramus =.97 ±.02, LCX =.95 ±.03; large-ramus: LAD =.95 ±.03, Ramus =.98 ±.01; LCX =.96 ±.03; p <.05). A large ramus was associated with a higher prevalence of a distal FFR CT ≤.80 (odds ratio 7.0, 95% CI 1.2–40.1, p =.03). A proximal ramus diameter predicted distal FFR CT ≤.80 (cut-off 2.1 mm, AUC.76, sensitivity 100%, specificity 52%, 95% CI.61–.90). Conclusions: The presence of a large-ramus artery may cause an FFR CT decline in no apparent CAD.