The use of quantitative coronary angiography (QCA) in interventional cardiology

Abstract

SummaryQuantitative Coronary Angiography (QCA) has become the gold standard in the assessment of the immediate and long term results of various coronary interventions, both pharmacological and mechanical. In particular, the phe-nomenon of restenosis has been primarily described and researched on the basis of sequential QCA studies. Although initially intended as a system to assess the extent of disease within the coronary tree, the Cardiovascular Angiographic Analysis System (CAAS) has become the most utilized quanti-tative system for restenosis trials. At the Thoraxcenter, more than 1700 patients who have undergone PTCA, stenting, atherectomy or laser have had sequential angiographic studies analyzed by CAAS. Several new and unforseen problems have been encountered with this later application of the CAAS system, due to either the device or the effect of the intervention on the angiographic appearance of the treated coronary vessel. In this chapter, we review the capabilities of the CAAS system and outline some of the methodological problems and shortcomings of the system that have become evident from our experience with coronary devices. Specific examples include the immediate evaluation after a complicated dissection, the determination of the exact location of radioluscent stents within the coronary vessel and the difficulties of assessing reference diameters in segments that have been “overdilated” following stenting or atherectomy. Although our studies have relied almost exclusively on data based on a contour detection method, we have been interested in densitometry and discuss the use of information (and problems) of the data obtained by the densitometric method. Finally, we address the issue of how to use QCA-acquired data to compare the various coronary interventional devices with information currently available and for future randomized trials. We have evaluated the immediate results with the concept of the “expansion ratio”. The late results have been compared by two methods: 1) historical angioplasty studies previously analyzed by CAAS;