In addition, it has been suggested that as a metalloproteinase, the PAPP-A produced by activated macrophages may be involved in degradation of the plaque extracellular matrix with consequent weakening of the fibrous cap
23), (24) Although axial resolution remains too low for measuring cap thickness of the fibrous cap
with its rupture, a recent study reports that the thickness of the fibrous cap
with its rupture were visualized.
A fibrous cap
forms over the lesion, enlarging and restructuring it.
Plaques with large lipid cores and thin fibrous caps
are vulnerable to rupture, resulting in thrombus formation and possible arterial occlusion.
Virtual histology analysis of the plaque confirmed the findings of vulnerable plaque with a large lipid core and a thin fibrous cap
In the most rupture prone plaque, Lp-PLA2 was also highly prominent within the thin fibrous cap
, suggesting that Lp-PLA2 and its enzymatic byproducts may play a role in promoting plaque instability.
If the atheroma does not fissure, the smooth muscle cells within the intima will lay down collagen, forming a dense fibrous cap
characteristic of a Type V lesion or fibroatheroma.
Inflammation, which is implicated in the formation of early fatty streaks as well as at the onset of adverse cardiovascular events, causes cells within the plaque to secrete enzymes that degrade and weaken the fibrous cap
, leading to rupture of unstable plaques and thrombus (clot) formation.