Doppler Flow Velocity and Thermodilution to Assess Coronary Flow Reserve: A Head-to-Head Comparison With [15O]H2O PET

Abstract

Objectives: This study sought to compare Doppler flow velocity reserve (CFR_Doppl) and thermodilution-derived coronary flow reserve (CFR_thermo) head-to-head with the gold standard for quantification of myocardial perfusion, [¹⁵O]H₂O positron emission tomography (PET).

Background: Coronary flow reserve (CFR) is an important parameter for assessing coronary vascular function. To date, 2 techniques are available for invasive assessment of CFR: Doppler flow velocity and thermodilution. Although these techniques have been compared with each other, neither has been compared with [¹⁵O]H₂O PET perfusion imaging.

Methods: CFR was assessed in 98 vessels of 40 consecutive stable patients with suspected coronary artery disease. Patients underwent [¹⁵O]H₂O PET, followed by invasive angiography in conjunction with simultaneous measurements of fractional flow reserve, CFR_Doppl, and CFR_thermo. Both normal and obstructed arteries were included.

Results: The quality of Doppler flow velocity traces was significantly lower than that of thermodilution curves (p < 0.001). A moderate correlation was observed between CFR_Doppl and CFR_thermo (r = 0.59; p < 0.001). CFR_Doppl correlated well with PET-derived CFR (CFR_PET) (r = 0.82; p < 0.001). In contrast, the correlation between CFR_thermo and CFR_PET was only modest (r = 0.55; p < 0.001). This difference in correlation with CFR_PET was significant (t = 4.9; df = 95; p < 0.001). Bland-Altman analysis revealed a tendency of CFR_thermo to overestimate flow reserve at higher values.

Conclusions: Coronary flow reserve, determined using Doppler flow velocity, has superior agreement with [¹⁵O]H₂O PET in comparison with CFR_thermo.

Keywords: Doppler flow velocity; coronary flow reserve; mean transit time; positron emission tomography; thermodilution.