Comparison between adventitial and intimal inflammation of ruptured and nonruptured atherosclerotic plaques in human coronary arteries.

OBJECTIVE

To verify the possible role of adventitial inflammation in atherosclerotic plaque vulnerability and coronary artery remodelling.

METHODS

We compared the mean numbers of lymphocytes in the adventitia and in the plaque of ruptured thrombosed and stable equi-stenotic coronary segments of 34 patients who died due to acute myocardial infarction. We also analysed adventitial microvessels, adventitial fibrosis and the external elastic membrane.

RESULTS

In the adventitia, the numbers of lymphocytes and microvessels/mm2 were 69.5+/-88.3 and 60.9+/- 32.1 in culprit lesions and 16.4 +/- 21.1 and 44.3+/-16.1 in stable lesions (p<0.05); within the plaques, the mean number of lymphocytes was 24+/-40.8 in culprit lesions and 10.9+/-13.2 in stable ones (p=0.17). The mean percent area of adventitial fibrosis/cross-sectional area of the vessel was significantly lower in unstable plaques (p<0.001). The confocal images showed holes in the external elastic membrane.

CONCLUSION

Unstable plaques exhibit chronic pan-arteritis, accompanied by enlargement, medial thinning, and less fibrosis than in stable lesions, which is compatible with vessel aneurysm. Adventitial inflammation may contribute significantly to atheroma instability.