Stability of Flow Velocity and Intracoronary Resistance in the Intracoronary Electrocardiogram-triggered Pressure Ratio

It has been found that the assessment of coronary artery lesions using the fractional flow reserve and instantaneous flow reserve measurements reduces the incidence of further cardiovascular events. Here, we investigated differences in the coronary flow velocity and resistance within the analysis interval between the instantaneous flow reserve (iFR) and the intracoronary electrocardiogram (IC-ECG)-triggered distal/aortic pressure (Pd/Pa) ratio (ICE-T). Thirty-three consecutive patients with stenoses that required coronary flow measurement were enrolled. ICE-T was defined as the average Pd/Pa ratio in the period corresponding to the isoelectric line of the IC-ECG. The index value, flow velocity, and intracoronary resistance during the analysis intervals of the iFR and ICE-T, both at rest and under hyperemia, were compared. The index value and intracoronary resistance of the ICE-T were found to be significantly lower, while the flow velocity was significantly higher, than those of the iFR (P < 0.001), and all fluctuations in ICE-T values were also significantly smaller than those in the iFR.In conclusion, the ICE-T is theoretically superior to pressure-dependent indices for analyzing phases with low and stable resistance, without an increase in invasiveness.