Noninvasive transthoracic doppler flow velocity and invasive thermodilution to assess coronary flow reserve

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.