Atherosclerotic plaque pathohistology and classification with high-resolution MRI

A series of research works had proven that high-resolution magnetic resonance imaging (MRI) was an effective tool to identify the morphological appearance of atherosclerotic vulnerable plaque. We performed further study to compare ex vivo vascular morphology with MRI and histological examination using the specimens of carotid endarterectomy and femoral artery (FA) prosthetic reconstruction, and described the detailed histology and immunohistochemistry features of plaque.

Eight consecutive patients (five males, mean age 67.4 years) who were recruited into our study had high-grade stenosis or occlusion of carotid artery and FA (70 to 100%). Four patients accepted carotid endarterectomy and others underwent FA prosthetic reconstruction.

The high level of accuracy was shown in classification of the plaque type. The sections of plaques detected by MRI were classified as follows: 12 (22.2%) were modified American Heart Association (AHA) type III, 11 (20.4%) were type IV-V, 26 (48.2%) were type VI and 5 (9.3%) were type VII. According to the histological observations, the overall accurate rate by MRI showed a high level accuracy of 90.7% (49/54). Immunohistochemistry of cellular components in plaque shoulder demonstrated that CD68-positive macrophages were strongly dominated along the arterial wall. Reduced expression of smooth muscle actin (SMA)-positive smooth muscle cells were detected in the fibrous cap of atheroma. CD31 stain showed the increased presence of CD31-positive neomicrovessels.

Atherosclerosis is a systematic disease that can involve whole body vascular beds. Non-invasive high-resolution MRI will provide useful information in morphological studies of the arterial walls and classification of the plaque type.