In my textbook, it is written that atheromatous plaques block the artery. This leads to heart attack and and heart failure. But my question is why do the plaques only block arteries and not the veins? Do the plaques also block the veins?
Atherosclerosis can develop in high pressure systems, such as arteries, and not in low pressure systems, such as veins. It is high blood pressure that can damage the lining of the blood vessel and initiate the process of atherosclerosis.
BUT, atherosclerosis can develop in veins that have been used as grafts instead of arteries, for example, in a coronary artery bypass surgery.
In this regard, we may note that atherosclerotic lesions do not develop in the veins in their normal environment of low pressure and high flow, but that the lesions do develop when the veins are used as arterial bypass grafts where they are subjected to high pressure. Similarly, atherosclerotic lesions develop in the pulmonary arteries only in pulmonary hypertension.