Blood vessel which supply oxygenated blood to various organs of body are termed as arteries and blockages in arteries supplying any particular organ (heart, kidney, brain, etc) lead to cessation or decrease in blood supply to that organ. The genesis of these blockages is multi factorial out of which heredity, diabetes, hypertension, increased cholesterol levels in body, smoking are few known predisposing factors.
Regarding your query, as to whether chelation therapy removes these blockages, I would say, its a hype and until now there is no clear evidence or data to support this. However cholesterol lowering medicines do have potential (enough evidence to support) to slow down the progression of these blockages, these drugs have been shown even to regress these blockages in some studies.