CORONARY FLOW RESERVE CALCULATED FROM PRESSURE MEASUREMENTS IN HUMANS- VALIDATION WITH POSITRON EMISSION TOMOGRAPHY

Background Experimental studies have shown that fractional flow reserv e (defined as the ratio of maximal achievable flow in a stenotic area to normal maximal achievable flow) can be calculated from coronary pre ssure measurements only. The objectives of this study were to validate fractional flow reserve calculation in humans and to compare this inf ormation with that derived from quantitative coronary angiography. Met hods and Results Twenty-two patients with an isolated, discrete proxim al or mid left anterior descending coronary artery stenosis and normal left ventricular function were studied. Relative myocardial flow rese rve, defined as the ratio of absolute myocardial perfusion during maxi mal vasodilation in the stenotic area to the absolute myocardial perfu sion during maximal vasodilation (adenosine 140 mu g.kg(-1).min(-1) in travenously during 4 minutes) in the contralateral normally perfused a rea, was assessed by O-15-labeled water and positron emission tomograp hy (PET). Myocardial and coronary fractional flow reserve were calcula ted from mean aortic, distal coronary, and right atrial pressures reco rded during maximal vasodilation. Distal coronary pressures were measu red by an ultrathin, pressure-monitoring guide wire with minimal influ ence on the transstenotic pressure gradient. Minimal obstruction area, percent area stenosis, and calculated stenosis flow reserve were asse ssed by quantitative coronary angiography. There was no difference in heart rate, mean aortic pressure, or rate-pressure product during maxi mal vasodilation during PET and during catheterization. Percent area s tenosis ranged from 40% to 94% (mean, 77+/-13%), myocardial fractional flow reserve from 0.36 to 0.98 (mean, 0.61+/-0.17), and relative flow reserve from 0.27 to 1.23 (mean, 0.60+/-0.26). A close correlation wa s found between relative flow reserve obtained by PET and both myocard ial fractional flow reserve (r=.87) and coronary fractional flow reser ve obtained by pressure recordings (r=.86). The correlations between r elative flow reserve obtained by PET and stenosis measurements derived from quantitative coronary angiography were markedly weaker (minimal obstruction area, r=.66; percent area stenosis, r=-.70; and stenosis f low reserve, r=.68). Conclusions Fractional flow reserve derived from pressure measurements correlates more closely to relative flow reserve derived from PET than angiographic parameters. This validates in huma ns the use of fractional flow reserve as an index of the physiological consequences of a given coronary artery stenosis.