P6181The association of coronary lumen volume to left ventricle mass ratio with myocardial blood flow and fractional flow reserve

Background A low coronary lumen volume to left ventricle mass ratio (V/M) derived from coronary computed tomography angiography (CCTA) has been proposed as a factor contributing to impaired myocardial blood flow (MBF) even in the absence of obstructive coronary artery disease (CAD). Objective To elucidate the association of V/M with non-invasively obtained MBF parameters by means of [15O]H2O positron emission tomography (PET), as well as its correlations with invasively measured fractional flow reserve (FFR), overall and specifically in vessel with non-obstructive CAD. Methods This is a substudy of the PACIFIC trial, in which 208 patients underwent CCTA, and [15O]H2O PET prior to invasive coronary angiography (ICA) in conjunction with 3 vessel FFR measurements. Patient specific V/M was calculated for 152 patients. Matched vessel specific hyperemic MBF (hMBF), coronary flow reserve (CFR), FFR, and patient specific V/M were available for 431 vessels. The median V/M (20.71 mm3/g) was used to divide the study population into a group with a low V/M (<20.71 mm3/g) and a high V/M (≥20.71 mm3/g). Non-obstructive CAD was defined as a ≤50% stenosis grade on ICA. Results Overall, a higher percentage of vessels with an abnormal hMBF (34% vs. 19%, p=0.009), lower FFR values (0.93 [interquartile range: 0.85–0.97] vs. 0.95 [0.89–0.98], p=0.016), and a higher number of positive FFR values (20% vs. 9%, p=0.004) were observed among vessels in the low V/M group. Furthermore, a weak correlation between V/M, global hMBF (R=0.179, p=0.027), and global CFR (R=0.163, p=0.045) as well as a weak significant association with vessel specific hMBF (p=0.027), and FFR (p<0.001) was observed (figure 1). V/M was not independently predictive of vessels specific MBF parameters or FFR. Among vessels with non-obstructive CAD (361 vessels), an abnormal hMBF tended to be more frequently observed in vessels with a low patient specific V/M (21% vs. 13%, p=0.056). Globally, there was no correlation between V/M and hMBF nor CFR. Patient specific V/M tended to be weakly associated with vessel specific hMBF (p=0.083) and was associated with FFR (p=0.027) (figure 1). Lastly, patient specific V/M tended to be independently predictive of FFR in this specific group. Conclusion Overall, vessels with an abnormal hMBF, and positive FFR measurements were more frequently observed in patients with a low V/M compared to those with a high V/M. Furthermore, V/M weakly correlated with global hMBF as well as with CFR and was associated with vessel specific hMBF and FFR. However, there was no correlation between V/M and global nor vessel specific blood flow parameters in the absence of obstructive CAD, notwithstanding a weak association of V/M with FFR within this group was noted.