Abstract
BACKGROUND: Coronary flow reserve (CFR) provides prognostication and coronary physiological information, including epicardial coronary stenosis and microvascular function. The relationship between stress transthoracic Doppler echocardiography (TDE)-derived coronary flow velocity reserve (CFR(S-TDE)) and thermodilution-derived coronary flow reserve (CFR(thermo)) before and after elective percutaneous coronary intervention (PCI) remains unclear. METHODS: This single-center prospective registry study evaluated patients who underwent fractional flow reserve (FFR)-guided elective PCI for left anterior descending artery (LAD) lesions with wire-based invasive physiological measurements and pre- and post-PCI stress TDE examinations. RESULTS: A total of 174 LAD lesions from 174 patients were included in the final analysis. A modest correlation was detected between the pre-PCI CFR(S-TDE) and the pre-PCI CFR(thermo) (r=0.383, P<0.001). The frequently used CFR(S-TDE) threshold of 2.0 corresponded to a pre-PCI CFR(thermo) of 2.18. Pre-PCI CFR(S-TDE) underestimated pre-PCI CFR(thermo) [1.89 (1.44-2.31) vs. 2.05 (1.38-2.93), P<0.001]. Both CFR(S-TDE) and CFR(thermo) increased significantly post-PCI [pre-PCI CFR(S-TDE) 1.89 vs. post-PCI CFR(S-TDE) 2.33, P<0.001; pre-PCI CFR(thermo) 2.05 (1.38-2.93) vs. post-PCI CFR(thermo) 2.59 (1.63-3.55), P<0.001]. In contrast, there was no significant relationship between changes in CFR(S-TDE) and changes in CFR(thermo) after PCI (r=0.008, P=0.915) or between post-PCI CFR(S-TDE) and post-PCI CFR(thermo) (r=0.054, P=0.482). CONCLUSIONS: Pre-PCI CFR(S-TDE) and CFR(thermo) are modestly correlated, but post-PCI CFR(S-TDE) and CFR(thermo) have no correlation. CFR(S-TDE) and CFR(thermo) are not interchangeable, particularly post-PCI, suggesting that the two metrics represent different coronary physiologies after PCI.