Characterization of Coronary Atherosclerosis by Magnetic Resonance Imaging
The following are points to remember about this review of the current state of cardiovascular magnetic resonance imaging (CMR) assessment of coronary atherosclerosis:
1. As CMR of the coronary arteries requires very high spatial resolution, this requires additional scan time and results in increased susceptibility to motion-related artifacts due to cardiac motion and breathing motion. New sequences are being developed to address these limitations, which may permit more routine and comprehensive coronary imaging in the future.
2. Noncontrast CMR is promising for identification of subclinical coronary atherosclerosis, coronary plaque burden, and positive remodeling of the coronary artery, as it requires no contrast agents and does not expose patients to ionizing radiation. While coronary wall imaging by CMR remains technically challenging, the excellent safety profile of this technique may be promising for serial plaque imaging.
3. Noncontrast CMR may be useful to noninvasively evaluate coronary artery endothelial function by imaging the vasodilatory response to stimuli. This application may be useful to assess the relationship between local coronary endothelial function and plaque characteristics.
4. Direct visualization of intracoronary thrombus has been reported using noncontrast CMR. While technically challenging, this may provide a novel means to noninvasively and safely evaluate the formation of intracoronary thrombus.
5. Imaging of coronary artery wall edema is possible using noncontrast CMR, and this finding has been reported at sites of acute coronary syndrome and acute coronary injury. As this is thought to identify neovascularization and increased permeability of the endothelium, investigations using this technique may improve our understanding of acute coronary pathology.
6. Studies suggest that increased gadolinium contrast uptake in the coronary wall may be associated with acute inflammation, edema, neovascularization, and specific types of plaque composition. Limited data are available at present, but this is a promising area for future research.
7. Novel contrast agents have been developed that target specific molecules such as fibrin and elastin, and have been demonstrated to identify thrombi, lipid-rich plaques, and inflammatory cell infiltration. Such contrast agents may be useful to identify high-risk plaques and to image inflammatory cell infiltration following myocardial infarction.
8. While technical challenges remain, CMR is able to uniquely image the presence and characteristics of coronary atherosclerosis and to assess endothelial function, and is highly promising for identification of high-risk plaque features. As CMR requires no ionizing radiation and no iodinated contrast, it may represent a safe technique to assess clinical risk and for serial monitoring of coronary plaque.
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