By Megan Rauscher

WESTPORT, CT (Reuters Health) – Prolonged intensive lipid-lowering therapy is associated with a markedly decreased lipid content in carotid atherosclerotic plaques, according to a report in the October issue of Arteriosclerosis, Thrombosis and Vascular Biology: Journal of the American Heart Association.

"The clinical implication of this is that the low plaque lipid composition would predict greater plaque stability, and would thus reduce clinical ischemic events such as myocardial infarction or stroke," lead investigator Dr. Xue-Qiao Zhao of the University of Washington, Seattle, told Reuters Health.

Dr. Zhao and colleagues used high-resolution MRI to determine the effects of 10 years of intensive lipid-lowering therapy with niacin, lovastatin, and colestipol, on the plaque content of eight hyperlipidemic CAD patients randomly selected from 60 participants of the Familial Atherosclerosis Treatment Study (FATS). Eight patients with CAD matched for age, baseline LDL and triglycerides who had never been treated with lipid-lowering drugs served as controls.

The investigators found that treated patients had significantly lower LDL cholesterol levels than untreated patients at 84 mg/dL versus 158 mg/dL, respectively, and higher HDL levels at 51 mg/dL versus 37 mg/dL, respectively (p < 0.001).

Moreover, the plaque lipid content was "strikingly" reduced in the treated group compared with the untreated group, 1% versus 17%, respectively, the team reports. Treated subjects also had a smaller core lipid area compared with untreated subjects, 0.7 mm² versus 10.2 mm², respectively (p = 0.01).

The extremely low plaque lipid composition among the treated patients was associated with a low rate (5%) of cardiac death or nonfatal MI over 10 years of follow-up in the FATS study, the team notes. This "encouraging" finding lends support to the belief that less lipid in plaque means more stability and fewer ischemic events, they say. Prospective studies are now under way to test this hypothesis.

Editorialists Dr. Joel D. Morrisett and Dr. William Insull, Jr., from Baylor College of Medicine in Houston, Texas, believe the use of MRI for evaluating the efficacy of lipid-lowering intervention has "far-reaching significance and implications."

MRI is non-invasive, non-irradiative and permits serial measurements over time without the hazards of other imaging techniques such as intravascular ultrasonography and angiography.

"But arguably, the most valuable characteristic of MRI is its inherent remarkable capacity for distinguishing tissue components of differing chemical composition," Drs. Morrisett and Insull contend. With further refinements and standardization, this MRI-derived information should prove "useful for estimating the vulnerability of a plaque to rupture."

Arterioscler Thromb Vasc Biol 2001;21:1623-1629,1563-1564.