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Quantitative Coronary Arteriography and Its Assessment of Atherosclerosis: Part II. Calculating Stenosis Flow Reserve from Percent Diameter Stenosis

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Background. Assessment of coronary artery disease by quantitative coronary arteriog raphy (QCA), while highly accurate, is more expensive than visual estimates of disease and involves the measurement of numerous variables requiring specialized equipment and personnel, thereby reducing its clinical applicability. In part 1 of this paper, the indepen dent variables that influence flow of 1040 coronary artery segments were analyzed. Methods and Results. Using the information previously reported in part 1 of this paper, we set out to determine the importance of each of the independent variables (percent diameter and area stenosis, length, absolute diameter, entry and exit angles) in the prediction of stenosis flow reserve (SFR). Analysis of variance (ANOVA) was used to determine the importance of each of these variables, as well as their interactions, on the determination of SFR. Only percent diameter stenosis (%DS) demonstrated statis tical significance (P < 0.001) in determining stenosis flow reserve. When the results of SFR were plotted against %DS, a quadratic relationship was demonstrated with an R2 value of 0.903 (r = 0.95). To verify the quadratic equation, the %DS of 100 different arterial stenoses was measured and used to calculate an SFR by the quadratic formula. The QCA and quadratic (calculated) determined SFRs compared favorably, with a correlation of 0.97. Conclusions. The ability to calculate SFR directly from measured %DS allows the incor poration of calculated SFR into the clinical setting, where cardiologists can interpret lesion severity both anatomically and hemodynamically. This incorporation can be done without additional cost to the physician, hospital, patient, or third-party payers. Contemporary quantitative coronary arteriography (QCA) methods accurately measure stenosis flow reserve (SFR) under conditions of coronary artery disease but are too expensive for practical clinical use. A simple laminar flow (Poiseuille) 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 practical effect. © 1994, Sage Publications. All rights reserved.

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