Evaluation of Atorvastatin on Atherosclerosis Composition

The primary goal of this project is to evaluate the effect of the cholesterol lowering drug Atorvastatin on the composition and character of coronary atherosclerosis (heart blockages). Atorvastatin is known to reduce cholesterol, reduce cardiac events, and halt the progression of coronary atherosclerosis. However, the reduction in cardiac events is out of proportion to the reductions in the total amount of atherosclerosis. Thus, the drug likely decreases cardiac events by changing the composition of the coronary atherosclerotic plaques. It is likely that the drug causes the "heart blockage" to change from a "vulnerable plaque" to a "stable" plaque. There are several features of "vulnerable plaques" that can be detected in arteries of the heart using intravascular ultrasound. The goal of this project is to examine the effects of atorvastatin on atherosclerosis plaque composition using this intravascular ultrasound in patients undergoing serial cardiac catheterizations. Our hypothesis is that atorvastatin will reduce the number of "vulnerable plaques" and increase the number of "stable plaques" seen by intravascular ultrasound. We plan to enroll a total of 20 patients. The patients will be evaluated by cardiac catheterization with intravascular ultrasound analysis and then be treated with atorvastatin for 6 months. These 20 patients will return to the cardiac catheterization laboratory 6 months later for a repeat catheterization with intravascular ultrasound evaluation. The secondary goal of this proposal is to evaluate in humans the relationship between coronary atherosclerosis (plaque buildup in the arteries of the heart) and wall shear stress (the force generated against the wall of the artery by the flow of blood). The reason for this sub-study is that there is great interest in understanding the characteristics that cause the progression of coronary atherosclerosis. Local forces such as shear stress may play an important role in the focal progression of "vulnerable" atherosclerotic plaques. Indeed, low shear stress is known to be an important factor in the early formation of atherosclerosis. However, the relationship of low shear stress to development and progression of advanced "rupture prone" ("vulnerable") plaques has not been elucidated. Our hypotheses are: (1) "Vulnerable plaques" are more commonly located at areas of low shear stress(2) "Vulnerable plaques" at areas of low shear stress are more likely to progress over the following 6 months than plaques located in normal shear stress regions.