A new imaging technique has enabled scientists to actually see the loss of fat in artery walls after treatment with a cholesterol-lowering agent. A refinement of MRI technology that allows visualization of the artery wall was developed at the Cardiovascular Institute at Mount Sinai School of Medicine and reported to the AHA meeting in November.

It's well known that statins reduce heart attacks, unstable angina, and strokes. How they do it has been a question. One possibility has been that they reduce the fat content of plaques, making them more stable.

This report is the first direct evidence in humans that statins physically reduce plaque.

The new MRI images also demonstrated that plaques that have more cholesterol in them are most likely to rupture and cause heart attacks or strokes. Researchers point out that plaque doesn't cause any problems as long as it stays in the artery wall. But when it ruptures, the body tries to repair the damage by forming blood clots. And it is the clots that cause heart attacks or strokes by blocking blood vessels to the heart or brain.

The reduction in fat is not immediate, however. While significant reductions in LDL and total cholesterol levels were observed as early as 6 weeks after the trial began, it took 12 months before the changes in the artery walls were visible. MRIs done at 6 months did not show the changes.

Since MRI is a non-invasive and painless procedure, the researchers projected its usefulness in examining patients early to see if plaque is present - in much the same way that preventive measures such as mammograms and chest x-rays are used.