Reproducibility of measurements of coronary narrowings by videodensitometry: unreliability of single view measurements.

Computer-assisted videodensitometry has been shown to be a reliable and reproducible method of measuring absolute and relative coronary narrowings. Using a commercially available analyzer (Vanguard XR70) we confirmed the intra- and interobserver reproducibilities in 34 narrowings in 9 patients. Analyses were performed on normal area and diameter, stenotic area and diameter, percent area stenosis and percent diameter stenosis. For all 6 analyses, excellent intra- and interobserver correlations were found (r = 0.93-0.98), with slopes close to 1 and intercepts close to zero. In a separate study of 16 lesions in 11 patients, each lesion was analyzed in both the RAO and LAO planes. Correlation between the measurements was reasonable with r = 0.76 for the stenotic area and r = 0.75 for the absolute diameter stenosis. However, with suboptimal slopes (0.54 and 0.63 respectively), actual differences between measurements in the two planes were often unacceptably large. These data suggest that videodensitometry is a highly reproducible quantitative angiographic method; however, single view analyses are inadequate for comparative studies.