Several indices used to assess coronary flow and the impact of coronary stenosis are available in clinical practice. While these indices are providing complementary data about coronary flow, the interplay and test retest repeatability between indices in a controlled setting remain sparse.

We sought to evaluate in a fixed setting, the impact of coronary stenosis on Fractional Flow Reserve (FFR), Absolute coronary Blood Flow (ABF), Absolute Microvascular Resistance (AMR), Index of Microvascular Resistance (IMR) and Coronary Flow Reserve (CFR) using a coronary flow simulator.

To assess the impact of stenosis on a coronary flow simulator (FFR WetLab Version 2.0) we created stenoses from 10% to 70% stenosis in a 3mm diameter plastic tube controlled with Optical Coherence Tomography. Three different flows and two consecutive measurements were obtained applying the following indices: FFR, ABF, AMR, IMR and CFR with a pressure/temperature wire and infusion catheter two consecutive times.

We compared 113 pairs of measurements within 3 different fixed flows (Panel AB) as well as test-retest repeatability in 24 FFR, 24 ABF, 24 AMR, 24 IMR and 17 CFR. Overall we observed that FFR and flow (ABF) decrease proportionally while resistances (AMR) increase with tighter stenoses with stable IMR and CFR. Test-retest repeatability showed excellent reproducibility for FFR, ABF and AMR respectively 0.98 (0.97–0.99), 0.92 (0.81–0.97) and 0.91 (0.79–0.96) (P<0.0001 for all); however, test-retest repeatability was weaker for IMR and poor for CFR respectively 0.53 (0.16–0.77) (P=0.006) and 0.27 (−0.26–0.67) (P=0.30).

In coronary flow simulator FFR and ABF values decrease and AMR increase with progressive tighter coronary stenosis with excellent test-retest repeatability while IMR and CFR remained stable albeit with poorer test-retest repeatability probably in part due to variations manual injection techniques.