[1][2] The material consists of mostly macrophage cells,[3][4] or debris, containing lipids, calcium and a variable amount of fibrous connective tissue.

The heart arteries are difficult to track because they are small (from about 5 mm down to microscopic), they are hidden deep within the chest and they never stop moving.

[12][13] Over time, atheromata usually progress in size and thickness and induce the surrounding muscular central region (the media) of the artery to stretch out, which is termed remodeling.

[citation needed] The endothelium (the cell monolayer on the inside of the vessel) and covering tissue, termed fibrous cap, separate atheroma from the blood in the lumen.

[citation needed] The accumulation (swelling) is always in the tunica intima, between the endothelium lining and the smooth muscle middle layer of the artery wall.

[citation needed] After they accumulate large amounts of cytoplasmic membranes (with associated high cholesterol content) they are called foam cells.

When foam cells die, their contents are released, which attracts more macrophages and creates an extracellular lipid core near the centre to inner surface of each atherosclerotic plaque.

[citation needed] Conversely, the outer, older portions of the plaque become more calcified, less metabolically active and more physically stiff over time.

[citation needed] Historically, arterial wall fixation, staining and thin section has been the gold standard for detection and description of atheroma, after death and autopsy.

Traditionally, clinical carotid ultrasounds have only estimated the degree of blood lumen restriction, stenosis, a result of very advanced disease.

The limited exception to this rule is that with very advanced atheroma, with extensive calcification within the wall, a halo-like ring of radiodensity can be seen in most older humans, especially when arterial lumens are visualized end-on.

On cine-floro, cardiologists and radiologists typically look for these calcification shadows to recognize arteries before they inject any contrast agent during angiograms.

Atheromata continue to be the primary underlying basis for disability and death, despite a trend for gradual improvement since the early 1960s (adjusted for patient age).

[citation needed] The older methods for understanding atheroma, dating to before World War II, relied on autopsy data.

Autopsy data has long shown initiation of fatty streaks in later childhood with slow asymptomatic progression over decades.

[6] One way to see atheroma is the very invasive and costly IVUS ultrasound technology; it gives us the precise volume of the inside intima plus the central media layers of about 25 mm (1 in) of artery length.

The most promising since the early 1990s has been EBT, detecting calcification within the atheroma before most individuals start having clinically recognized symptoms and debility.

[citation needed] From human clinical trials, it has become increasingly evident that a more effective focus of treatment is slowing, stopping and even partially reversing the atheroma growth process.

[citation needed] Paroi artérielle et Risque Cardiovasculaire in Asia Africa/Middle East and Latin America (PARC-AALA) is another important large-scale study, in which 79 centres from countries in Asia, Africa, the Middle East, and Latin America participated, and the distribution of CIMT according to different ethnic groups and its association with the Framingham cardiovascular score was investigated.

Multi-linear regression analysis revealed that an increased Framingham cardiovascular score was associated with CIMT, and carotid plaque independent of geographic differences.

[citation needed] It has been reported in another study that a maximal CIMT value of 0.956 mm had 85.7% sensitivity and 85.1% specificity to predict angiographic CAD.

More recently, some of the complex immune system patterns that promote, or inhibit, the inherent inflammatory macrophage triggering processes involved in atheroma progression are slowly being better elucidated in animal models of atherosclerosis.