QUANTITATIVE CORONARY ARTERIOGRAPHY AND ITS ASSESSMENT OF ATHEROSCLEROSIS .2. CALCULATING STENOSIS FLOW RESERVE FROM PERCENT DIAMETER STENOSIS

Background. Assessment of coronary artery disease by quantitative coro nary arteriography (QCA), while highly accurate, is more expensive tha n visual estimates of disease and involves the measurement of numerous variables requiring specialized equipment and personnel, thereby redu cing its clinical applicability. In part 1 of this paper, the independ ent variables that influence flow of 1040 coronary artery segments wer e analyzed. Methods and Results. Using the information previously repo rted in part 1 of this paper, we set out to determine the importance o f each of the independent variables (percent diameter and area stenosi s, length, absolute diameter, entry and exit angles) in the prediction of stenosis, flow reserve (SFR). Analysis of variance (ANOVA) was use d to determine the importance of each of these variables, as well as t heir interactions, on the determination of SFR. Only percent diameter stenosis (%DS) demonstrated statistical significance (P < 0.001) in de termining stenosis flow reserve. When the results of SFR were plotted against %DS, a quadratic relationship was demonstrated with an R2 valu e of 0.903 (r = 0.95). To verify the quadratic equation, the %DS of 10 0 different arterial stenoses was measured and used to calculate an SF R by the quadratic formula. The QCA and quadratic (calculated) determi ned SFRs compared favorably, with a correlation of 0.97. Conclusions. The ability to calculate SFR directly from measured %DS allows the inc orporation of calculated SFR into the clinical setting, where cardiolo gists can interpret lesion severity both anatomically and hemodynamica lly. This incorporation can be done without additional cost to the phy sician, hospital, patient, or third-party payers. Contemporary quantit ative coronary arteriography (QCA) methods accurately measure stenosis flow reserve (SFR) under conditions of coronary artery disease but ar e too expensive for practical clinical use. A simple laminar flow (Poi seuille) model was fitted to 1040 stenotic lesions and cross-validated on an independent sample of 100 lesions. This simple model was found adequate for practical use with a cross-validated correlation of 0.97 with QCA measurement. Turbulence and other known complexities had no p ractical effect.