THERAPY AND PREVENTION PTCA Changes in cross-sectional area of the coronary lumen in the six months after angioplasty: a quantitative analysis of the variable response to percutaneous transluminal angioplasty

Although immediate and late changes in coronary stenoses after percutaneous transluminal coronary angioplasty (PTCA) have been reported, most investigators have employed qualitative or semiquantitative techniques to analyze the angiograms. Such data is not optimal because of considerable interobserver variability and the use of relative instead of absolute changes in lesion geometry. Analysis is further compounded by the indistinct edges that characterize coronary lesions immediately after angioplasty. To quantify the changes in minimal cross-sectional area (MCSA) of the coronary lumen that occur during and after PTCA, we analyzed the angiograms of 23 patients before PTCA, immediately after PTCA, and at 7.2 + 3.0 (mean ± SD) months follow-up using two computerassisted methods of angiographic analysis quantitative coronary angiography (QCA) and videodensitometry (VID). QCA provides an absolute measure of the area of the lumen; VID is a nongeometric method that is not dependent on exact border recognition. Based on these quantitative methods, we found that successful angioplasty is associated with about a three-fold increase in the MCSA of the lesion (from 1.0 to 3.2 mm2). This area is, however, well below normal and is less than half of the average MCSA of the inflated dilating balloon. Analysis of follow-up angiograms demonstrated that eight of 23 patients had a substantial late increase in the MCSA of the lesion (from 2.7 to 4.1 mm2) after the angioplasty procedure. Clinical, hemodynamic, and angiographic characteristics immediately after PTCA were not predictive of MCSA of the lumen at follow-up. Because substantial late increases in MCSA of the lumen occur in about one-third of patients, angiographic and noninvasive analyses performed immediately after PTCA will not define the ultimate adequacy of coronary dilation in many patients undergoing PTCA. Circulation 73, No. 3, 467-475, 1986. PERCUTANEOUS transluminal coronary angioplasty (PTCA) has gained wide clinical acceptance as a treatment for coronary artery disease.1' 2 Despite widespread use, however, neither the mechanisms responsible for the initial coronary luminal enlargement From The Cardiovascular Center, The Cardiovascular Image Processing and Ultrasonic Imaging Laboratories, and Departments of Internal Medicine, Electrical and Computer Engineering, and Radiology University of Iowa and Iowa City Veterans Administration Medical Center, Iowa City. Supported by National Institutes of Health grants HL27633, HL29976, HL00916, HL14388, HL32295 (Specialized Center of Research in Ischemic Heart Disease), and HL01290 (Research Career Development Award, Dr. Skorton), and the U.S. Veterans Administration grant MRIS 1100.2. Address for correspondence: Maryl Johnson, M.D., Cardiovascular Division, Department of Internal Medicine, University of Iowa Hospitals and Clinics, Iowa City, IA 52242. Received July 1, 1985; revision accepted Oct. 3, 1985. Vol. 73, No. 3, March 1986 produced by PTCA nor the factors that determine the duration of the increase in the size of the lumen are well understood. Previous angiographic follow-up studies have shown that restenosis occurs in approximately onethird of initially successful dilations.3 Visual estimates of percent stenosis have also suggested that in some cases a further increase in size of the lumen may occur in the 6 months after PTCA.' 6,7 The significance of such observations based on percent stenosis is uncertain for several reasons. First, estimates of percent stenosis are associated with a high degree of interobserver variability." Second, measurements of percent stenosis correlate poorly with size of the lumen and physiologic significance of the lesion.'2 '4 Third, immediately after angioplasty, the dilated coronary 467 by gest on Jne 5, 2017 http://ciajournals.org/ D ow nladed from