The radiographic assessment of coronary blood flow parameters.

TO HAVE a complete understanding of coronary ar- tery disease, a clinician must be able to evaluate coro- nary anatomy, ventricular function, and coronary blood flow. Selective coronary arteriography and left ventriculography remain the standard means for ob- taining information on the first two factors. Although visual analysis of percent diameter coronary stenosis suffers from significant intraobserver and interob- server variability, quantitative analysis of arterio- graphic images provides accurate and objective mea- surements of arterial geometry. The third factor, coronary blood flow, is rarely measured directly. Most often, alterations in blood flow are inferred clinically from the coronary anatomy. This inference is based on the close correlation between percent diameter stenosis and coronary flow reserve found in experimental ani- mals, coronary flow reserve being defined as the ratio of maximal hyperemic-to-baseline blood flow in a coronary artery.' Contrary to these experimental ob- servations are data suggesting that human coronary flow reserve correlates poorly with percent diameter stenosis and only moderately with absolute measure- ments of stenosis geometry-' Recent developments in radiographic technology have therefore rekindled an interest in measuring coro- nary blood flow and flow reserve in the catheterization laboratory, with the intention of providing an inde- pendent means for their assessment. Results of pre- liminary trials suggest that this is possible, although contrast media cannot be used to measure coronary blood flow by traditional approaches. Early data also suggest that many factors in addition to epicardial arterial stenosis need to be considered in the clinical interpretation of blood flow parameters.