Background-Atherosclerotic plaque stability is related to histological composition. However, current diagnostic tools do not allow adequate in vivo identification and characterization of plaques. Spectral analysis of backscattered intravascular ultrasound (IVUS) data has potential for real-time in vivo plaque classification. Methods and Results-Eighty-eight plaques from 51 left anterior descending coronary arteries were imaged ex vivo at physiological pressure with the use of 30-MHz IVUS transducers. After IVUS imaging, the arteries were pressure-fixed and corresponding histology was collected in matched images. Regions of interest, selected from histology, were 101 fibrous, 56 fibrolipidic, 50 calcified, and 70 calcified-necrotic regions. Classification schemes for model building were computed for autoregressive and classic Fourier spectra by using 75% of the data. The remaining data were used for validation. Autoregressive classification schemes performed better than those from classic Fourier spectra with accuracies of 90.4% for fibrous, 92.8% for fibrolipidic, 90.9% for calcified, and 89.5% for calcified-necrotic regions in the training data set and 79.7%, 81.2%, 92.8%, and 85.5% in the test data, respectively. Tissue maps were reconstructed with the use of accurate predictions of plaque composition from the autoregressive classification scheme. Conclusions-Coronary plaque composition can be predicted through the use of IVUS radiofrequency data analysis.Autoregressive classification schemes performed better than classic Fourier methods. These techniques allow real-time analysis of IVUS data, enabling in vivo plaque characterization. (Circulation. 2002;106:2200-2206.)

for the Integrated Biomarker and Imaging Study-2 InvestigatorsBackground-Lipoprotein-associated phospholipase A 2 (Lp-PLA 2 ) is expressed abundantly in the necrotic core of coronary lesions, and products of its enzymatic activity may contribute to inflammation and cell death, rendering plaque vulnerable to rupture. Methods and Results-This study compared the effects of 12 months of treatment with darapladib (an oral Lp-PLA 2 inhibitor, 160 mg daily) or placebo on coronary atheroma deformability (intravascular ultrasound palpography) and plasma high-sensitivity C-reactive protein in 330 patients with angiographically documented coronary disease. Secondary end points included changes in necrotic core size (intravascular ultrasound radiofrequency), atheroma size (intravascular ultrasound gray scale), and blood biomarkers. Background therapy was comparable between groups, with no difference in low-density lipoprotein cholesterol at 12 months (placebo, 88Ϯ34 mg/dL; darapladib, 84Ϯ31 mg/dL; Pϭ0.37). In contrast, Lp-PLA 2 activity was inhibited by 59% with darapladib (PϽ0.001 versus placebo). After 12 months, there were no significant differences between groups in plaque deformability (Pϭ0.22) or plasma highsensitivity C-reactive protein (Pϭ0.35). In the placebo-treated group, however, necrotic core volume increased significantly (4.5Ϯ17.9 mm 3 ; Pϭ0.009), whereas darapladib halted this increase (Ϫ0.5Ϯ13.9 mm 3 ; Pϭ0.71), resulting in a significant treatment difference of Ϫ5.2 mm 3 (Pϭ0.012). These intraplaque compositional changes occurred without a significant treatment difference in total atheroma volume (Pϭ0.95). Conclusions-Despite adherence to a high level of standard-of-care treatment, the necrotic core continued to expand among patients receiving placebo. In contrast, Lp-PLA 2 inhibition with darapladib prevented necrotic core expansion, a key determinant of plaque vulnerability. These findings suggest that Lp-PLA 2 inhibition may represent a novel therapeutic approach.

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Traditionally, the development of coronary artery disease (CAD) was described as a gradual growth of plaques within the intima of the vessel. The outer boundaries of the intima, the media and the external elastic membrane (EEM), were thought to be fixed in size. In this model plaque growth would always lead to luminal narrowing and the number and severity of angiographic stenoses would reflect the extent of coronary disease. However, histologic studies demonstrated that certain plaques do not reduce luminal size, presumably because of expansion of the media and EEM during atheroma development. This phenomenon of "arterial remodeling" was confirmed in necropsy specimens of human coronary arteries. More recently, the development of contemporary imaging technology, particularly intravascular ultrasound, has allowed the study of arterial remodeling in vivo. These new imaging modalities have confirmed that plaque progression and regression are not closely related to luminal size. In this review, we will analyze the role of remodeling in the progression and regression of native CAD, as well as its impact on restenosis after coronary intervention.