995-17 Are Intracoronary Doppler Flow Velocity Measurements Accurate for Assessment of Coronary Flow Reserve?

Abstract

Coronary flow reserve (CFR) measurements are useful for assessment of coronary stenoses and microvascular function in patients. Intracoronary Doppler probes are commonly used for CFR measurement, but changes in flow velocity reflect volumetric flow only if the conduit vessel size is constant. We hypothesized that potent resistance vessel dilators used for CFR measurement also produce conduit artery dilation that perturbs the relationship between coronary flow velocity and volumetric flow. Coronary flow velocimetry (Doppler-tipped guidewire) and quantitative angiography were performed in a non-stenotic artery at control (Con), and during a maximally dilating dose of intracoronary adenosine before and after nitroglycerin (NTG) 100 μg i.c. in 6 patients. CFR was measured conventionally using peak/rest flow velocity changes alone (Vel) and flow estimates incorporating angiographic vessel cross-sectional area (VxA). (mean ± s.e.m.) Coronary Diameter (mm) CFR Con adenosine NTG Con Vel Can VxA NTG Vel 2.50 ± 0.26 2.89 ± 0.30 * 2.93 ± 0.28 * 3.0 ± 0.2 4.0 ± 0.3 † 3.8 ± 0.4 ‡ * p < 0.01 vs control † p < 0.01 vs can Vel ‡ p = 0.08 vs can Vel 1) Intracoronary adenosine produces concurrent conduit as well as resistance vessel dilation that is similar in magnitude to nitroglycerin. 2) Coronary flow reserve is underestimated if blood flow changes are assessed using flow velocity measurements alone. 3) Coronary flow reserve measured using velocity changes after pretreatment with nitroglycerin is similar to measurement that incorporates angiographic cross-sectional area, and may obviate the need for area determination.