Novel doppler assessment of intracoronary volumetric flow reserve: validation against PET in patients with or without flow-dependent vasodilation

Abstract

Volumetric blood flow (Q) determination requires simultaneous assessment of mean blood flow velocity and vessel cross-sectional area. At present, no method provides both values. Intracoronary Doppler-based assessment of coronary flow velocity reserve (CFVR) relies on average peak velocity (APV). Because this does not account for changes in velocity profile or vessel area usually occurring with flow-dependent vasodilation, results can be misleading. The aim of this clinical study was to validate against the current gold standard (measurement of myocardial perfusion reserve [MPR] by PET) a new, Doppler-based method for calculating coronary Q and coronary flow reserve (CFR).

Methods: Doppler-based intracoronary Q was measured with a proprietary guidewire device in a nonstenotic coronary artery at baseline and during adenosine-induced hyperemic flow (140 mug/kg/min intravenously during 7 min). Three gate positions were assessed, of which 2 were lying within the vessel and 1 was intersecting the vessel. The zeroth (M(0)) and the first (M(1)) Doppler moments of the intersecting gate were used to calculate mean blood flow velocity (M(1)/M(0)) and vessel area (M(0)), and M(0) of the 2 proximal gates was used to correct for scattering and attenuation. CFR was calculated as hyperemic/resting flow with Q and compared with APV-derived CFVR and with the corresponding segmental MPR obtained with (15)O-labeled water and PET.

Results: Q (CFR, 2.60 +/- 1.07) correlated well with PET (MPR, 2.58 +/- 1.11) (r = 0.832, P < 0.005; Bland-Altman limits, -1.42 to 1.09), whereas CFVR did not (r = 0.09, P = not statistically significant; Bland-Altman limits, -3.36 to 2.24). However, in vessels without dilation, there was no difference between CFR, CFVR, and MPR.

Conclusion: This procedure for intracoronary Q measurement using the proprietary Doppler guidewire system, which accounts for both changes in flow profile and changes in vessel area, allows invasive, accurate assessment of CFR even in the presence of flow-dependent vasodilation.