Diverse changes of ramus coronary artery on computed tomography derived fractional flow reserve due to ramus artery in normal coronary artery disease

Abstract

Abstract Funding Acknowledgements Type of funding sources: None. Background The ramus artery contributes to the development of turbulence, which may influence computed tomography (CT) derived fractional flow reserve (FFRCT) even without coronary artery disease. The relationship between ramus-induced turbulence and FFRCT is unclear. Purpose To investigate the effect of the ramus artery on FFRCT in normal coronary arteries. Methods A total of 120 consecutive patients who underwent both CT angiography including FFRCT and invasive coronary angiography, resulting in < 20% coronary artery stenosis were evaluated. The patients were divided into three groups: absent-ramus (n = 72), small-ramus that could not be analysed by FFRCT (n = 18), and large-ramus that could be analysed by FFRCT (n = 30). FFRCT was measured at the proximal and distal segments of the left anterior descending (LAD), left circumflex (LCX), and ramus artery (in absent-ramus group, FFRCT was measured at just above the bifurcation between LAD and LCX) were measured. The proximal FFRCT segment (proximal LAD, yellow circle; proximal Ramus or just above the bifurcation angle, yellow square; proximal LCX, yellow triangle) was measured at the same level of each vessel and the distal segment (distal LAD, white circle; distal ramus, white square; distal LCX, white triangle) was measured at obtained by the FFRCT analysis (Figure 1). Vessel morphology (vessel length, lumen volume, plaque volume), bifurcation angle, and left ventricular mass were assessed. Results In the absent-ramus group, proximal FFRCT showed no significant difference between three vessels (LAD, 0.96 ± 0.02; MID, 0.97 ± 0.02; LCX, 0.97 ± 0.02). However, in small and large-ramus groups, proximal FFRCT was significantly higher in the ramus artery than LAD and LCX (small-ramus: LAD = 0.95 ± 0.03, Ramus = 0.97 ± 0.02, LCX = 0.95 ± 0.03; large-ramus: LAD = 0.95 ± 0.03, ramus = 0.98 ± 0.01; LCX = 0.96 ± 0.03; p < 0.05) (Figure 2). A large ramus was associated with a higher prevalence of a distal FFRCT ≤0.80 (odds ratio 7.0, 95% CI 1.2–40.1. p = 0.03). A proximal ramus diameter predicted distal FFRCT ≤ 0.80 (cut-off 2.1 mm, AUC 0.76, sensitivity 100%, specificity 52%, 95% CI 0.61–0.90). Conclusions The presence of a large-ramus artery may cause an FFRCT decline in normal coronary arteries.