Standardized angiographic projections allow evaluation of coronary artery side branches with quantitative flow ratio (QFR).

Quantitative flow ratio (QFR) is a novel, software-based noninvasive method for the quantitative evaluation of coronary physiology. QFR results correlate with invasive FFR measurements in the three main epicardial coronary arteries. However, QFR data for the evaluation of coronary side branches (SB) are scarce. The evaluation of QFR-performance of SB was retrospective and prospective. Eighty-seven patients with suspected chronic coronary syndrome, who received angiography using routine core lab projections, were retrospectively analyzed. On the second part 37 patients, who received angiography using recommended standardized coronary angiography projections, were prospectively analyzed. Quantitative analysis was performed for SB with a maximum lumen diameter proximal of ≥2 mm based on quantitative coronary angiography (QCA) by two certified experts with the software QAngio XA 3D 3.2. Using routine projections, QFR computation in 55 % of the SB were obtained (123 out of 224). Using standardized projections, 85 % of SB were computed by QFR (64 out of 75; p < 0.001 vs routine projections). The fluoroscopy time for recommended projections was not significantly different as opposed to routine projections (3.75 2.2 vs. 4.58 3.00 min, p = 2.6986). Using the standardized projections was associated with a higher amount of contrast medium (53.44 24.23 vs. 87.95 43.73 ml, p < 0.01), longer overall procedure time (23.23 16.35 vs. 36.14 17.21 min, p < 0.01) and a higher dose area product (1152.28 576.70 vs. 2540.68 1774.07 cGycm, p < 0.01). Our study shows that the blood flow of the vast majority of coronary SB can be determined non-invasively by QFR in addition to the main epicardial coronary arteries when standardized projections are used.