Pathologic validation of a new method to quantify coronary calcific deposits in vivo using intravascular ultrasound

Current methods of calcium quantification by intravascular ultrasound (IVUS ) measure the are of calcium using the cross-sectional image at the lesion and at the reference site while neglecting calcium elsewhere. Calcium at th ese sites may not adequately represent the extent of total epicardial coron ary calcium. We devised a new method to quantify calcium as a percentage of the coronary luminal surface. This study examines whether this new method accurately reflects coronary calcium determined by histology. Seventeen pos tmortem coronary arteries were pressure-fixed and imaged by IVUS using a mo torized pullback device. Total plaque-luminal circumferential length and ca lcified plaque-luminal circumferential length were measured from serial cro ss-sectional IVUS images every 1 mm. With use of Simpson's method, the tota l plaque and calcified plaque surface area was then calculated. Histologic sections were stained with hematoxylin-eosin and Movat pentachrome at 3-mm intervals. Calcium was independently quantified by planimetry under light m icroscopy. Histologic analysis (n = 253 sections) revealed a wide range of calcium (0 to 47 mm(2); mean 12 +/- 16 mm(3)). The IVUS-derived calcified p laque surface area was 17 +/- 23 mm(2)), which represented 3.1 +/- 4.1% (ra nge 0% to 13.9%) of the total plaque surface area. The histologic and IVUS quantification of calcium by this method wets strongly related (r = 0.84, p < 0.0001), which was an improvement over current 2-dimensional measures of calcium are (r = 0.41, p = 0.18). Calculation of calcified plaque surface area from sequential IVUS images appears to accurately reflect the degree o f total coronary calcification. (C) 2000 by Excerpta Medica, Inc.