Effect of Elective Percutaneous Coronary Intervention on Hyperemic Absolute Coronary Blood Flow Volume and Microvascular Resistance

Background-The hemodynamics involved in the relationship between absolute coronary blood flow (ABF) volume and myocardial resistance (MR) are complex, and the effect of percutaneous coronary intervention (PCI) on their changes remains unclear. The aim of this study was to investigate the differences in hyperemic ABF and MR before and after elective PCI using a thermodilution method. Methods and Results-We investigated 28 vessels (right coronary artery, 9; left anterior descending coronary artery, 18; left circumflex coronary artery, 1) from 28 patients with stable angina pectoris undergoing elective PCI. ABF was measured pre- and post-PCI using a pressure-temperature sensor-equipped wire, based on a thermodilution method with a continuous saline infusion of 20 mL/min through a proximally located microcatheter with an end-hole in the target vessel. MR equals distal coronary perfusion pressure divided by ABF at maximal hyperemia. Conventional fractional flow reserve was also measured pre- and post-PCI. Fractional flow reserve increased significantly after PCI (from 0.70 [0.65-0.75] to 0.88 [0.85-0.95]) in all examined territories. ABF also increased significantly (from 137.8 mL/min[86.3-180.8 mL/min] to 173.3 mL/min [137.9-234.3 mL/min]; increase: 52.8 mL/min [9.7-80.8 mL/min]) while MR decreased in 11 vessels and increased in 17. No significant relationship was detected between these increases in fractional flow reserve and ABF. Both pre- and post-PCI MR distributed in a wide range, and there was a significant relationship between pre-PCI MR and the increase in ABF (r=0.44; P=0.02) although no significant change in MR was observed between pre-and post-PCI (P=0.37). Conclusions-Direct measurement of ABF and MR using thermodilution method offers a feasible approach that could shed a light on previously unclear aspects of coronary hemodynamics.