Validation of coronary artery saphenous vein bypass graft diameter measurements using quantitative angiography

The accepted value for reproducibility (true change) is two standard deviations (SD) of the differences between repeat measurements. It has been well established for coronary artery measurements using several different quantitative coronary angiography (QCA) systems, but it has not been well documented for saphenous vein grafts (SVG). The purpose of this study was to assess, using the Cardiovascular Measurement System (CMS), the measurement reproducibility of 24 vein grafts from 24 patients who had symptom-directed control angiography. Three equal graft segments were studied separately. Focal narrowings expressed in percent stenosis varied from 5 to 80% (mean 20.8 +/- 15.9%). The average minimum lumen diameter (MLD) was 3.07 +/- 0.81 mm and the average interpolated reference diameter (Ref. D) was 3.87 +/- 0.58 mm. We assessed the reproducibility of measurements obtained from two separate imagings of the graft in the same view but at least 20 minutes apart, near the beginning and at the end of the angiographic procedure (simulating baseline and end-trial examinations). The SD for differences in measurements (variability) was 0.183 mm for the MLD, 0.193 mm for the Ref.D, 0.184 mm for the mean diameter (Mean D) and 3.72% for the percent diameter stenosis (PDS). A reasonable true change cut-off for SVG measurements in our laboratory is > or = 0.4 mm for the minimum and mean lumen diameters, and > or = 10% for the PDS, when QCA is obtained with the QCA-CMS analytical software package.