A fatty spot on a child's aorta is not an "early myocardial infarction". It is the morphological start that the Committee on Vascular Lesions of the American Heart Association (Stary H.C. et al., Circulation 1994) described as types I–II: an increase in the number of intimal macrophages and the appearance of foam cells, then layers of foamy macrophages and smooth muscle cells with lipid droplets. Such changes by themselves do not deform the lumen and produce no clinical signs. They matter because the types that do break the intima grow out of them.
The intima is the inner layer of the artery, normally thin, with the endothelium facing the lumen. At sites of adaptive intimal thickening (locations constant from birth, a response to local haemodynamics), atherosclerosis begins earlier and progresses further — this is an observation of the Stary classification, not "atherosclerosis is the same everywhere".
The chain you need to be able to tell at the exam without a list of ten arrows, but in the right order.
- ApoB-containing particles (mainly LDL) penetrate the endothelium into the intima. The probability of retention rises with the plasma concentration of particles and with the duration of exposure. ESC/EAS 2025 specifically emphasises: atherosclerosis begins early, and cumulative exposure to high LDL-C in youth is associated with a higher risk of ASCVD later.
- In the intima the particles are retained, oxidised and modified. Modified LDL is recognised by macrophage scavenger receptors.
- Macrophages accumulate cholesterol esters and turn into foam cells — cells whose cytoplasm looks foamy on section because of lipid vacuoles. A cluster of foam cells macroscopically produces a fatty spot.
- Intimal smooth muscle cells also accumulate lipid and synthesise extracellular matrix.
- Extracellular lipid collects into pools (Stary type III, the "intermediate" lesion) — this is the bridge to the atheroma.
Inflammation here is not "a separate disease" but part of the response to retained lipid: recruitment of monocytes, endothelial activation, cytokine production. The review formulation "atherosclerosis is an inflammatory disease" (Ross R., N Engl J Med 1999;340:115–126) is useful as an illustration of the mechanism, but not as a basis for changing management: in this course management is set by guidelines, not by a 1999 review.
The experimental root of lipid infiltration is the cholesterol models of atherosclerosis in rabbits, classically associated with the work of Anichkov at the beginning of the 20th century. This is an animal model: it proved that exogenous cholesterol can cause atherosclerosis-like lesions in the rabbit. In humans the causality of LDL-C was proven not by this experiment but by genetics (FH, Mendelian randomisation on ATP citrate lyase in the rationale for bempedoic acid, ESC/EAS 2025) and by RCTs of LDL-C lowering.
The boundary of the lesson. The course does not assert "inflammation is primary, lipid secondary" or the reverse as an ideology. The working model of the 2025 guidelines: lipid in the wall triggers inflammation, the plaque grows, the risk of an acute event grows. The therapeutic lever with the strongest evidence base is lowering LDL-C.
Another boundary. Endothelial dysfunction, vasospasm and microvascular dysfunction are part of the spectrum of chronic coronary syndromes in ESC 2024, but they are not the same as morphological atherosclerosis of the aorta. They must not be substituted for one another in an answer at a pathological anatomy exam.