Oh the previous rely is correct. Coenzyme Q10 has been shown to help prevent the accumulation of arterial plaque, and MAY help "clean" plaque deposits from arteries. The later is not yet proven conclusively.
Vitamin E is also beneficial.
The reason why coenzyme Q10 help prevent the deposition of plaque in arteries is because they are antioxidants that prevent LDL cholesterol from oxidising. It is oxidised low density lipoproteins (LDL) that cause arterial plaque deposition