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Simultaneous coronary pressure and flow velocity measurements in humans. Feasibility, reproducibility, and hemodynamic dependence of coronary flow velocity reserve, hyperemic flow versus pressure slope index, and fractional flow reserve.

BACKGROUND
To assess coronary lesion severity in the catheterization laboratory, several guide wire-based methods have been proposed. The purpose of the present study was to compare the feasibility and the reproducibility of coronary flow velocity reserve (CFVR), instantaneous hyperemic diastolic velocity-pressure slope index (IHDVPS), and pressure-derived myocardial fractional flow reserve (FFRmyo).


METHODS AND RESULTS
From distal coronary pressure and flow velocity signals (0.014-in guide wires), CFVR, IHDVPS, and FFRmyo were computed in 15 stenoses (13 patients) under the four following pairs of conditions: (1) twice under baseline conditions; (2) during atrial pacing at 80 and 110 bpm; (3) before and during intravenous infusion of nitroprusside; and (4) before and during intravenous infusion of dobutamine. A total of 104 measurements were obtained. Both CFVR and FFRmyo could be calculated in all cases. IHDVPS could be calculated in only 79% of cases. The mean value of CFVR did not change between the two baseline measurements and during infusion of nitroprusside but decreased from 1.85 +/- 0.41 to 1.66 +/- 0.45 (P < .05) during atrial pacing and from 1.90 +/- 0.50 to 1.41 +/- 0.28 (P < .05) during dobutamine infusion. The mean values of IHDVPS and FFRmyo remained similar, whichever the changes in hemodynamic conditions. The coefficient of variation between two consecutive measurements was significantly lower for FFRmyo (4.2%) than for CFVR (17.7%) and for IHDVPS (24.7%).


CONCLUSIONS
CFVR is easy to measure but sensitive to hemodynamic changes. IHDVPS can be measured only in < 80% of cases and is highly variable even without changes in hemodynamic conditions. FFRmyo is easy to measure and almost independent of hemodynamic changes.