Atherosclerotic Plaque Morphology

Atherosclerosis

• Atherosclerotic plaques have three components: cells (smooth muscle cells, macrophages, and T cells), extracellular matrix (including collagen), and intracellular and extracellular lipid.
• Atherosclerotic plaques can gradually occlude vessel lumina, compromising blood flow and causing ischemic injury.

Morphology

• Atherosclerotic plaques consist of a central lipid core, a fibrous cap, and a residual lumen.
• Inflammation, calcifications, and neovascularization are common features of atherosclerotic plaques.

Atherosclerosis Consequences

• Atherosclerotic stenosis: narrowing of the lumen, causing ischemic injury, typically occurs when the occlusion produces a 70% decrease in luminal cross-sectional area.
• Rupture, ulceration, and erosions: exposing highly thrombogenic plaque constituents (collagen), which can lead to hemorrhage, atheroembolism, and aneurysm formation.
• Atheroembolism: plaque rupture can discharge atherosclerotic debris into the bloodstream, producing microemboli that can block distant arteries.
• Aneurysm formation: atherosclerosis-induced pressure or ischemic atrophy of the underlying media, with loss of elastic tissue, causes weakness and potential rupture.

Pathogenesis

• Endothelial cell injury and dysfunction cause increased vascular permeability, leukocyte and platelet adhesion, and inflammation.
• Injured endothelial cells allow the accumulation of lipoproteins, leading to monocyte migration into the intima and transformation into macrophages and foam cells.
• Smooth muscle cells produce extracellular matrix (collagen) and inflammatory cytokines, which activate T-cells.
• PDGF (from activated platelets, macrophages, endothelial cells, and smooth muscle cells) induces smooth muscle cell recruitment and proliferation.

Morphology – Fatty Streaks

• Fatty streaks: composed of lipid-filled foamy macrophages, beginning as multiple minute flat yellow spots, eventually coalescing into elongated streaks 1 cm long or longer.

Arteriolosclerosis

• Arteriosclerosis: hardening of the arteries, a generic term reflecting arterial wall thickening and loss of elasticity, with distinct clinicopathologic conditions: atherosclerosis, arteriolosclerosis, and Mönckeberg medial sclerosis.

Atherosclerosis

• Characterized by intimal lesions called atheromas (or atheromatous or atherosclerotic plaques) that impinge on the vascular lumen and can rupture to cause sudden occlusion.
• Involves medium-sized to large arteries and underlies the pathogenesis of coronary, cerebral, and peripheral vascular disease.

This quiz covers the components and morphology of atherosclerotic plaques, including cells, extracellular matrix, and lipid. It also touches on ulceration and thrombus in complicated lesions.