IMPROVED ASSESSMENT OF CORONARY STENOSIS SEVERITY USING THE RELATIVE FLOW VELOCITY RESERVE

Background-Myocardial fractional flow reserve (FFR) is based on pressu re measurements. We have now sought to establish a Doppler-based conce pt of relative flow velocity reserve (RFVR) for the functional assessm ent of stenosis severity in epicardial coronary arteries. A clear thre shold value to discriminate the functional severity of a coronary sten osis does not exist for coronary flow velocity reserve (CVR) based on intracoronary Doppler measurements. In contrast, the concept of FFR, w hich is based on intracoronary pressure measurements, has been extensi vely validated. An FFR value below 0.75 reliably indicates a significa nt stenosis. Methods and Results-RFVR is calculated as the ratio betwe en distal CVR in the stenosed target vessel and distal CVR in a nonste notic reference vessel. In 21 patients, RFVR was determined in 24 targ et vessels by use of intracoronary adenosine and correlated to the FFR , determined as the ratio of mean poststenotic to aortic pressures, in the target vessel. Stenosis severity was classified according to quan titative coronary angiography analysis. Reference diameter was 3.0+/-0 .4 mm (mean+/-SD), and area stenosis was 74+/-15% (range, 40% to 95%). CVRs in the target and reference vessels were 2.1+/-0.5 and 2.6+/-0.7 , respectively. FFR ranged from 0.49 to 0.99 (mean, 0.81+/-0.15) and R FVR from 0.53 to 1.0 (mean, 0.82+/-0.13). Poststenotic CVR did not cor relate with either percent area stenosis (r=0.27, P=NS) or FFR (r=0.33 , P=NS). In contrast, FFR as well as RFVR showed a curvilinear relatio n to percent area stenosis (r=0.89, P<0.0001 and r=0.79, P<0.0001, res pectively). There was a close linear correlation between FFR and RFVR (r=0.91, P<0.0001). Conclusions-RFVR correlates closely to FFR and to percent area stenosis, whereas the correlation of CVR with FFR and per cent area stenosis is rather poor. RFVR is a promising new concept for assessment of coronary stenosis severity and clinical decision making based on Doppler measurements.