Computed Tomography Coronary Angiography in Patients With Acute Myocardial Infarction Without Significant Coronary Stenosis
What plaque characteristics are observed in infarct-related coronary arteries following acute myocardial infarction (AMI) in the absence of significant stenosis by invasive coronary angiography (ICA)?
This prospective study compared plaque characteristics by coronary computed tomographic angiography (CCTA) between infarct-related coronary arteries (IRAs) and non-IRAs in 50 individuals following AMI without significant stenosis by ICA (maximal diameter stenosis <50%), and with evidence of late-gadolinium enhancement by magnetic resonance imaging. From an overall population of 2,079 individuals with AMI who underwent ICA at a single center, 76 were identified as having no significant stenosis; after excluding individuals with imaging contraindication (n = 5) or lack of late-gadolinium enhancement (n = 21), the final study population consisted of 50 patients.
ICA reported normal coronary arteries in 25 patients and nonsignificant plaque in the remaining 25 individuals. CCTA identified plaque in 42 individuals, with 61 plaques noted in IRAs and 40 identified in non-IRAs. IRAs (vs. non-IRAs) demonstrated significant differences in plaque composition (p = 0.005) with a larger proportion representing noncalcified or mixed plaque, larger mean plaque area (6.1 ± 5.4 mm2 vs. 4.2 ± 2.1 mm2, p = 0.03), and a higher remodeling index (1.25 ± 0.41 vs. 1.08 ± 0.41, p = 0.01); no differences were observed in mean stenosis severity, the presence of spotty calcification, or mean attenuation.
In patients who experience AMI without significant stenosis by ICA, IRAs are observed to have a different plaque composition, larger plaque area, and greater plaque remodeling as compared to non-IRAs.
Patients presenting with AMI but without significant stenosis by ICA are common and can be challenging from a diagnostic perspective. This study found that CCTA frequently identified coronary plaque in IRAs that appeared completely normal by ICA, illustrating the limitations of a technique that can only visualize the vessel lumen. Further, there is growing interest in determining specific plaque characteristics that may be associated with greater risk, especially as many AMIs are known to occur in plaques without significant stenosis. While this study is limited to observation of post-AMI plaque, it identifies important differences in plaque features between culprit and nonculprit arteries, which may improve our understanding of AMI and identification of at-risk lesions.
Keywords: Constriction, Myocardial Infarction, Plaque, Atherosclerotic, Coronary Stenosis, Coronary Angiography, Tomography, Cardiology, Gadolinium, Cardiovascular Diseases, Calcinosis, Coronary Vessels, Magnetic Resonance Imaging
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