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I have learnt from Khan Academy's video on atheresclerosis that when the endothelial cells of an artery are damaged, atheroma forms at the site, and if the atheroma’s fibrous cap is ruptured, thrombogenic material is released from the atheroma, causing a blood clot. Having read other articles on this issue, this phenomenon is known as the atherothrombosis. And I believe that the fact that atheroma is formed before thrombosis is because thrombogenic material isn’t released when endothelial cells are damaged; thus cholesterol deposits in the area to form atheroma first.

However, in another video, when endothelial cells in blood vessels are damaged, platelet activation occurs due to the exposed collagen, and thrombosis occurs. Why is it that blood clotting occurs first instead of atheroma?

I have also learnt from my other question on Biology StackExchange that hypoxemia in the valve pocket of the large veins can cause endothelial damage that triggers the clotting cascade.

Therefore, I am confused as to which of atheroma or blood clot is formed first when endothelial cells are damaged; and if either one is formed first, why is that so? I’m certain that after a blood clot is formed, atheroma won’t be formed as I’ve not found any article that supports this sequence.

References:

  1. https://www.khanacademy.org/science/health-and-medicine/circulatory-system-diseases/coronary-artery-disease/v/atherosclerosis

  2. https://www.youtube.com/watch?v=R8JMfbYW2p4

  3. https://academic.oup.com/eurheartj/article/25/14/1197/509341

  4. How do veins's valve pocket sinus tend to become hypoxic?

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It is unlikely that atheroma would develop as a complication of a thrombus.

Atherosclerosis and thrombosis are two independent disorders and not two stages of the same disorder. Atherosclerosis is a disorder of the arterial wall and atheroma develops in the arterial wall. Thrombosis is a disorder of the blood and thrombus is merely attached to the atheroma or arterial or vein wall.

In veins, only thrombosis, but not atherosclerosis can occur, as mentioned here.

In arteries, thrombosis usually occurs only as a complication of an atheroma or calcification (PubMed, 2017):

The majority of coronary thrombi are caused by plaque rupture (55–65%), followed by [plaque] erosions (30–35%), and least frequently from calcified nodules (2–7%).

It is very rare that thrombus develops in arteries that have previously not been damaged by atherosclerosis (PubMed, 2015).

Further evidence that thrombus formation is an unlikely initial event in the development of an atherosclerotic plaque:

  1. Thrombosis is not mentioned as an initial stage or risk factor in development of atherosclerosis in various texts: Textbookofcardiology.org, Pathophys.org

  2. Genetic coagulation disorders are not likely risk factors for atherosclerosis (Atherosclerosis, Table 2 (PubMed, 2010):

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