Structural defects: Defects while in the composition of the blood vessel can result in narrowing. Most of these are obtained at start, plus the cause is unidentified. When atherosclerosis narrows the arteries, blood tends to clot while in the narrowed spots, forming a thrombus, a style of blood clot (plural https://www.sgvascularctr.com/types-of-treatments-for-vascular-diseases/