Determining Hemodynamically Significant Coronary Artery Disease: Patient-Specific Cutoffs in Quantitative Myocardial Blood Flow Using [ 15 O]H 2 O PET Imaging.

Currently, cutoffs of quantitative [15 O]H2 O PET to detect fractional flow reserve (FFR)-defined coronary artery disease (CAD) were derived from a single cohort that included patients without prior CAD. However, prior CAD, sex, and age can influence myocardial blood flow (MBF). Therefore, the present study determined the influence of prior CAD, sex, and age on optimal cutoffs of hyperemic MBF (hMBF) and coronary flow reserve (CFR) and evaluated whether cutoff optimization enhanced diagnostic performance of quantitative [15 O]H2 O PET against an FFR reference standard. Methods: Patients with chronic coronary symptoms underwent [15 O]H2 O PET and invasive coronary angiography with FFR. Optimal cutoffs for patients with and without prior CAD and subpopulations based on sex and age were determined. Results: This multicenter study included 560 patients. Optimal cutoffs were similar for patients with ( n = 186) and without prior CAD (hMBF, 2.3 vs. 2.3 mL·min-1 ·g-1 ; CFR, 2.7 vs. 2.6). Females ( n = 190) had higher hMBF cutoffs than males (2.8 vs. 2.3 mL·min-1 ·g-1 ), whereas CFRs were comparable (2.6 vs. 2.7). However, female sex-specific hMBF cutoff implementation decreased diagnostic accuracy as compared with the cutoff of 2.3 mL·min-1 ·g-1 (72% vs. 82%, P < 0.001). Patients aged more than 70 y ( n = 79) had lower hMBF (1.7 mL·min-1 ·g-1 ) and CFR (2.3) cutoffs than did patients aged 50 y or less, 51-60 y, and 61-70 y (hMBF, 2.3-2.4 mL·min-1 ·g-1 ; CFR, 2.7). Age-specific cutoffs in patients aged more than 70 y yielded comparable accuracy to the previously established cutoffs (hMBF, 72% vs. 76%, P = 0.664; CFR, 80% vs. 75%, P = 0.289). Conclusion: Patients with and without prior CAD had similar [15 O]H2 O PET cutoffs for detecting FFR-defined significant CAD. Stratifying patients according to sex and age led to different optimal cutoffs; however, these values did not translate into an increased overall accuracy as compared with previously established thresholds for MBF.