FRACTIONAL FLOW RESERVE - A USEFUL INDEX TO EVALUATE THE INFLUENCE OFAN EPICARDIAL CORONARY STENOSIS ON MYOCARDIAL BLOOD-FLOW

Background Fractional flow reserve (FFR), defined as the ratio of maxi mum flow in the presence of a stenosis to normal maximum flow, is a le sion-specific index of stenosis severity that can be calculated by sim ultaneous measurement of mean arterial, distal coronary, and central v enous pressure (P-a, P-d, and P-v, respectively), during pharmacologic al vasodilation. The aims of this study were to define ranges of FFR v alues, whether associated with inducible ischemia or not, and to inves tigate FFR in normal coronary arteries. Methods and Results In 60 pati ents accepted for percutaneous transluminal coronary angioplasty (PTCA ) of single-vessel disease, with a positive exercise test (ET) <24 hou rs before PTCA, FFR was determined during adenosine induced hyperemia just before and 15 minutes after angioplasty. P-a was measured by the guiding catheter, P-d by an 0.018-in fiber-optic pressure-monitoring w ire, and P-v by a multipurpose catheter. The ET was repeated after 5 t o 7 days, and only if this second ET had reverted to normal was the pr e-PTCA value of FFR definitely considered to be associated with induci ble ischemia and the post-PTCA value not. Myocardial FFR (FFR(myo)) in creased from 0.53+/-0.15 before PTCA to 0.88+/-0.07 after PTCA. Corona ry FFR increased from 0.38+/-0.19 to 0.83+/-0.12. In all patients, val ues of FFR(myo) definitely associated with ischemia were less than or equal to 0.74, whereas all except two values not associated with induc ible ischemia exceeded 0.74. Moreover, FFR(myo) in 18 coronary arterie s in 5 normal patients equaled 0.98+/-0.03. Conclusions A value of FFR (myo) of 0.74 reliably discriminates coronary stenosis, whether associ ated with inducible ischemia or not. Therefore, FFR(myo) is a useful i ndex to determine the functional significance of an epicardial coronar y stenosis and may facilitate clinical decision making in patients wit h an equivocal coronary stenosis.