Quantitative coronary angiography (QCA) in interventional cardiology: Clinical application of QCA measurements

Abstract

Q UANTITATIVE coronary angiography (QCA) has had a tremendous impact in the field of interventional cardiology. Because of its superior accuracy and objectivity, QCA has supplanted visual and hand-held caliper assessments of coronary arteriograms and has improved interobserver and intraobserver variability. 1-3 QCA is now the gold standard for the assessment of the coronary tree in the context of scientific research, 4 although it has not yet gained widespread appeal for routine clinical use. 5 Until very recently, mainly because of the expense and time-consuming aspect involved in routine clinical application of sophisticated computer-based analysis, QCA has only been available for off-line use. 6-9 In addition, the extra precautions that must be taken by the angiographer in obtaining images suitable for quantitative analysis 1~ imply that many angiograms routinely performed by busy clinicians or in acute or emergency situations may not be analyzable by an automated computer-based system. 5 However, with the progressively increasing number of clinics involved in multicenter restenosis prevention trials in which QCA plays an integral role, 1H3 perhaps these extra precautions may become routine clinical practice. QCA has been particularly useful in interventional cardiology as the only objective and reliable means of assessing the immediate and long-term effects of coronary interventions. In particular, the phenomenon of restenosis has primarily been described and researched most extensively on the basis of sequential QCA studies. At the Thoraxcenter (Rotterdam, The Netherlands), we have been advocating the importance of QCA since the first report of its use by our group in 1978 TM and, subsequently, with renewed vigour after our initial experience with QCA in the assessment of coronary interventions, as reported in 1982.15 The Cardiovascular Angiographic Analysis System (CAAS) has been extensively and rigorously validated, 16-18 and technical aspects are presented in the accompanying report. The entire angiographic database now consists of collected information from more than 5,000 patients who have undergone several different forms of nonoperative coronary revascularization. The principles of QCA, which were initially designed for diagnostic studies of coronary artery disease (CAD), have necessarily been adapted to more complex situations related to either the presence of a device or the effect of an intervention on the angiographic appearance of a damaged vessel. The introduction of several newer devices in the past 7 years, has presented a number of unique and unforeseen problems in image analysis and the subsequent interpretation of important quantitative data, as described in the accompanying report. The emergence of digital subtraction angiography has allowed on-line performance of QCA measurements in the catheterization laboratory, so that a technique previously confined to research applications has been transformed into a powerful analytic tool, directly applicable to clinical decision making. 7,19 The immediate availability of QCA measurements during interventional procedures provides a unique opportunity for more accurate selection of appropriate interventional devices (eg, balloon, stent, or atherotome dimension) and for continuous monitoring and immediate evaluation of the result obtained. During the last 5 years at the Thoraxcenter, a large clinical experience has been accumulated through the application of the Philips Digital Cardiac Imaging (DCI) Automated Coronary Analysis System. 6,9 In vivo study of stenosis phantoms placed in porcine