Intravascular Ultrasound Study of Patterns of Calcium in Ruptured Coronary Plaques

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° ± 41.4° vs 114.9° ± 77.4°, 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° ± 35.5° vs 95.8° ± 65.2°, 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°, a larger number of deep calcium deposits, and a remodeling index.