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The authors studied the reproducibility of repeated measurements of left ventricular volumes, weight, and wall stress as determined with cine and spin-echo magnetic resonance (MR) imaging. Two observers analyzed 40 serial MR imaging examinations twice, yielding a total of 160 repeated measurements. Estimates of 95% ranges for change were ejection fraction, 10% and 12%; wall mass, 16% and 21%; and wall stress, 22% and 20%, for measurements derived from cine MR imaging and spin-echo MR imaging, respectively. Reproducibility was not significantly different between cine and spin-echo MR imaging. Intraobserver, interobserver, and interexamination errors were quantitated with variance component analysis. Interexamination variability was the single most important contributor to total variance. Reproducibility of left ventricular chamber volume measurements with MR imaging is superior to that of other imaging modalities. In addition, MR imaging can provide reliable estimates of wall mass and wall stress. Efforts to improve reproducibility should be aimed at lowering interexamination variability.

Background-Matrix metalloproteinase-9 (MMP-9) is involved in atherosclerosis and elevated MMP-9 activity has been found in unstable plaques, suggesting a crucial role in plaque rupture. This study aims to assess the effect of MMP-9 on plaque stability in apolipoprotein E-deficient mice at different stages of plaque progression. Methods and Results-Atherosclerotic lesions were elicited in carotid arteries by perivascular collar placement. MMP-9 overexpression in intermediate or advanced plaques was effected by intraluminal incubation with an adenovirus (Ad.MMP-9). A subset was coincubated with Ad.TIMP-1. Mock virus served as a control. Plaques were analyzed histologically. In intermediate lesions, MMP-9 overexpression induced outward remodeling, as shown by a 30% increase in media size (pϭ0.03). In both intermediate and advanced lesions, prevalence of vulnerable plaque morphology tended to be increased. Half of MMP-9 -treated lesions displayed intraplaque hemorrhage, whereas in controls and the Ad.MMP-9/Ad.TIMP-1 group this was 8% and 16%, respectively (pϭ0.007). Colocalization with neovessels may point to neo-angiogenesis as a source for intraplaque hemorrhage. Conclusion-These data show a differential effect of MMP-9 at various stages of plaque progression and suggest that lesion-targeted MMP-9 inhibition might be a valuable therapeutic modality in stabilizing advanced plaques, but not at earlier stages of lesion progression. Key Words: adenovirus Ⅲ atherosclerosis Ⅲ metalloproteinases Ⅲ remodeling Ⅲ vulnerable plaque M atrix metalloproteinase (MMP) family members are enzymes with activity against extracellular matrix (ECM) constituents and are linked to atherosclerosis and plaque rupture. Because plaque disruption is a frequent cause of acute coronary syndromes 1,2,3 and MMPs are believed to degrade the ECM in the fibrous cap, 4,5 these enzymes might prove to be relevant targets for therapeutic intervention.However, the evidence that links these proteases to plaque destabilization is largely based on retrospective observations. Elevated MMP levels, among which is MMP-9, were found in unstable areas in carotid endarterectomy specimens. 6,7 Several promoter polymorphisms are correlated to coronary artery disease and to lesion complexity. 8,9 Also, elevated MMP-9 plasma levels can be detected in patients with acute coronary syndromes. 10,11 Taken together, this suggests that MMP-9 is causally involved in plaque destabilization, although the underlying mechanism remains unclear. One report showed that MMP-9 overexpression leads to thrombosis by stimulating release of matrix-bound tissue factor in balloon-injured coronaries. 12 Conversely, targeted gene disruption of MMP-9 in mice impaired smooth muscle cell (SMC) migration and led to collagen accumulation. 13 In vitro, MMP-9 deficiency impaired the contracting capacity of collagen, indicating that MMP-9 not only is important for SMC migration and matrix degradation but also plays a role in ECM organization. 13 Notwithstanding these observations, direct evidence fo...

MSCT angiography detected a high prevalence of CAD in asymptomatic patients with type 2 diabetes. A relatively high proportion of plaques were non-calcified (41%). Importantly, a calcium score <10 did not exclude CAD in these patients. MSCT might be a useful technique to identify CAD in asymptomatic patients with type 2 diabetes with incremental value over calcium scoring.