Quantitative coronary angiography in predicting functional significance of stenoses in an unselected patient cohort

Objectives. This study investigated the value of quantitative coronary angiography for predicting coronary flow reserve, as calculated from the transstenotic pressure gradient in a large, unselected patient cohort. Background. In patients with extensive coronary artery disease, quantitative coronary angiographic findings fail to correlate with functional variables of coronary stenoses. New developments in pressure-monitoring wire technology permitted validation in humans of the concept of myocardial fractional flow reserve as assessed from coronary pressure measurements. Methods. One hundred ten patients with normal left ventricular function were studied in the setting of coronary angioplasty. Quantitative coronary angiography was performed on-line using the ACA system. Myocardial and coronary fractional flow reserve were calculated from aortic and distal coronary pressures during maximal coronary hyperemia. Results. When data before and after angioplasty were pooled, a curvilinear relation was found between myocardial fractional flow reserve and both diameter stenosis (r = 0.79) and minimal lumen diameter (r = 0.82), and a linear relation was found between myocardial fractional flow reserve and angiographic stenosis flow reserve (r = 0.78). Correlations between quantitative angiographic and pressure-derived indexes, although significant, were characterized by a large dispersion of the values of myocardial fractional flow reserve for a similar angiographic degree of stenosis. Nevertheless, the sensitivity and specificity of a minimal lumen diameter <1.5 mm to predict myocardial fractional flow reserve <0.72 were 96% and 89%, respectively. The corresponding values for a diameter stenosis >50% were 93% and 85%, respectively. Conclusions. 1) In an unselected patient cohort, geometric indexes of stenosis severity derived from quantitative coronary angiography correlate significantly with physiologic variables, although these relations are imprecise in individual patients. 2) Nevertheless, the diagnostic accuracy of quantitative coronary angiography in predicting myocardial fractional flow reserve <0.72 is high and allows its use for clinical decision making in the individual patient during diagnostic or interventional procedures.