Assessment of coronary flowreserve by coronary pressure measurement: Comparison with flow- or Velocity-Derived coronary flow reserve

Objectives This study sought to assess the reliability of pressure-derived coronary flow reserve (CFR) compared with flow- or velocity-derived CFR. Background Coronary flow reserve has been reported to have important clinical implications for the evaluation and treatment of coronary artery disease. Methods Using a pressure guide wire, coronary pressure distal to the stenosis was measured at rest and during hyperemia in seven dogs with various degrees of stenosis and in 30 patients with angina (29 and 34 stenoses in total, respectively). Pressure at the tip of the guiding catheter was also recorded with a fluid-filled transducer system. Pressure-derived CFR was calculated by the square root of the pressure gradient across the stenosis (ΔP) during hyperemia divided by ΔP at rest, using a proprietary software system. At the same time, coronary flow was monitored proximal to the stenosis with a flow meter in the experimental dogs, and coronary flow velocity distal to the stenosis was assessed using a Doppler guide wire in patients with angina. Flow-derived (or velocity-derived) CFR was compared with pressure-derived CFR. Results Except for one stenosis that showed no ΔP at rest, a significant correlation was obtained between pressure- and flow-derived CFR in the animal study (y = 1.05x − 0.03, R = 0.92, P = 0.0001). A significant correlation was also seen between pressure- and velocity-derived CFR in the human study, except in three stenoses with no resting ΔP (y = 0.70x + 0.37, R = 0.85, P = 0.0001). Conclusions Similar to flow (or velocity) measurement, CFR can be assessed by pressure measurement, except in stenoses with minor resting ΔP.