| Heart scans may detect
improved coronary blood flow related to statin therapy better than merely
monitoring cholesterol levels Exercise heart scans may detect an improvement in coronary blood flow due to statin therapy that is not apparent by changes in blood cholesterol in patients with coronary heart disease, according to an article in the August 20th issue of the Journal of the American College of Cardiology. "While cholesterol-lowering statin drugs lower the risk of heart attack and other cardiac events in heart disease patients, they don't eliminate the risk entirely. Many healing mechanisms beyond cholesterol lowering are triggered by statin medications, including reductions of vascular inflammation, stimulation of development of new endothelial cells, and greater production of nitric oxide, which allows the artery to dilate in response to stress. Routine stress heart scans with radiotracers can demonstrate the healing of the coronary arteries during statin therapy," said Ronald G. Schwartz, MD, lead author of the current study. This pilot study compared serial changes in myocardial blood flow and in blood cholesterol profile over the first 6 months of treatment with pravastastin. Although cholesterol levels began to decrease by 6 weeks of treatment, improvements in blood flow to myocardium became statistically significant only at 6 months of therapy. This delay in response as assessed by heart scan matches the timing of trends of therapeutic effectiveness (namely, reduced myocardial infarction and cardiac death) seen in large clinical studies with the statin. Some patients showed improvement in perfusion abnormalities with expected substantial reductions in cholesterol, but improvement in the scans of other patients was not associated with major reductions in cholesterol levels. Furthermore, some patients showed improved cholesterol levels during early pravastatin treatment but showed no change or worsening of their heart scans. The findings raise the question of which test, if either, is the better predictor of therapeutic response to statin therapy? "The incremental value of the stress test with
nuclear imaging, or SPECT MPI (single photon emission computed tomography,
myocardial perfusion imaging) for predicting coronary events compared to
other clinical data such as coronary risk factors and exercise electrocardiogram
testing is very well established. It seems likely the heart scans of myocardial
perfusion track the expected prognostic benefit of statin therapy better
than do cholesterol levels," Schwartz said. "However, further
study in larger ongoing trials which is now taking place is required to
evaluate this question." In an editorial, Roger S. Blumenthal, MD, and Ty J. Gluckman, MD, also noted that the current study improves scientists' understanding of how statins affect coronary atherosclerosis. They pointed out that the use of other medicines, including aspirin, angiotensin converting-enzyme inhibitors, beta-blockers, and cholesterol-lowering drugs other than statins, make it difficult to be certain that the observations in this study are due solely to statin use. However, they urged that future studies use similar measures of heart perfusion and predicted that heart scans may eventually have a role in routine patient management. "This study leads us to take a closer
look at how myocardial perfusion imaging can be used to accurately predict
those individuals at increased risk of cardiovascular disease events. In
an era where the utilization of statins continues to grow, a better understanding
of their short- and long-term mechanisms of action is strongly needed,"
they wrote. |