A disease characterized by a degenerating metabolic lesion of large arteries in which the tunica intima becomes thickened by cholesterol deposits and hardened by healing and degeneration.

If coronary arteries are involved, circulation to the heart muscle is reduced, resulting in compromise of normal function because of ischemia (inadequate blood supply)

The endothelium and smooth muscle are primarily involved. In early stages the effects are partly reversible, whereas at late stages vessels become irreversibly calcified and hardened.
- The interest in cholesterol-lowering drugs stems from the role of cholesterol in the etiology and course of atherosclerosis.  This extremely widespread disease predisposes to myocardial infarction, cerebral thrombosis, ischaemic gangrene of the extremities, and other serious illnesses.  It is characterized by infiltration of cholesterol and oxidized cholesterol into macrophages, converting them into foam cells in lesions of the arterial walls.  This is followed by a complex sequence of changes involving platelets, macrophages, smooth muscle cells, growth factors, and inflammatory mediators that produces proliferative lesions which eventually ulcerate and may calcify.   The lesions distort the vessels and make them rigid.  In individuals with elevated plasma cholesterol levels, the incidence of atherosclerosis and its complications is increased.  The normal range for plasma cholesterol is said to be 120 to 200 mg/Dl, but in men, there is a clear, tight, positive correlation between the death rate from ischaemic heart disease and plasma cholesterol levels above 180 mg/dL.  Furthermore, it is now clear that lowering plasma cholesterol by diet and drugs slows and may even reverse the progression of atherosclerotic lesions and the complications they cause.
- In evaluating plasma cholesterol levels in relation to atherosclerosis, it is important  to analyze the LDL and HDL levels as well.  LDL delivers cholesterol to peripheral tissues, including atheromatous lesions, and the LDL plasma concentration correlates positively with myocardial infarctions and ischaemic strokes.  On the other hand, HDL picks up cholesterol from peripheral tissues and transports it to the liver, thus lowering plasma cholesterol.  It is interesting that women, who have a lower incidence  of myocardial infarction than men, have higher HDL levels.  In addition, HDL levels are increased in individuals who exercise and those who drink one or two alcoholic drinks per day, whereas they are decreased  in individuals who smoke, are obese, or live sedentary lives.  Moderate drinking decreases the incidence of myocardial infarction, and obesity and smoking are risk factors that increase it.  Plasma cholesterol and the incidence of cardiovascular diseases are increased in familial hypercholesterolemia, due to various loss-of-function mutations in the genes for LDL receptors.

Reference:
1. Ganong's Review of Medical Physiology: 23rd Edition.  Kim E. Barrett et al.  McGraw-Hill Publishing. 2010.