Coronary
calcium is intimately associated with coronary
atherosclerotic plaque development, although it is controversial as to whether coronary
calcium is associated with plaque instability. We analyzed 101 IVUS-detected ruptured plaques and compared them with 101 computer-matched control plaques without evidence of plaque
rupture. The
arc of
calcium was measured every 0.5 mm within 10-mm-long segments that spanned the minimum lumen cross-sectional area, and the number and length of
calcium deposits were assessed. Ruptured plaques had a significantly larger number of individual
calcium deposits than control plaques (3.5 +/- 1.7 vs 1.8 +/- 1.1, p <0.001). However, the
arc of the largest
calcium deposit was smaller and the length of the largest
calcium deposit in each plaque was shorter in ruptured plaques compared with control plaques (67.3 degrees +/- 41.4 degrees vs 114.9 degrees +/- 77.4 degrees , p <0.001, and 1.6 +/- 1.3 vs 4.0 +/- 2.7 mm, p <0.001, respectively). There was no difference in the number of superficial
calcium deposits between the 2 groups, although ruptured plaques had significantly smaller
arcs of superficial
calcium compared with control plaques (56.2 degrees +/- 35.5 degrees vs 95.8 degrees +/- 65.2 degrees , p <0.001). Conversely, the number of deep
calcium deposits was significantly larger in ruptured plaques than in control plaques (1.8 +/- 1.4 vs 0.3 +/- 0.6, p <0.001), although the
arc of deep
calcium was similar in the 2 groups. Ruptured plaques had quantitatively less
calcium, especially superficial
calcium, but a larger number of small
calcium deposits, especially deep
calcium deposits. In conclusion, ruptured plaques are associated with a larger number of
calcium deposits within an
arc of <90 degrees , a larger number of deep
calcium deposits, and a remodeling index.