Effects of prolonged intensive lipid-lowering therapy on the characteristics of carotid atherosclerotic plaques in vivo by MRI - A case-control study

High-resolution magnetic resonance imaging (MRI) with flow suppression not only provides useful information on luminal and wall areas of the carotid a rtery but also can identify the principal tissue components of the carotid atherosclerotic plaque. The effects of intensive lipid-lowering therapy on these MRI tissue characteristics were examined in patients with coronary di sease (CAD). Eight CAD patients who have been receiving intensive lipid-low ering treatment (niacin 2.5 g/d, lovastatin 40 mg/d, and colestipol 20 g/d) for 10 years in the Familial Atherosclerosis Treatment Study (FATS) follow -up were randomly selected from among 60 such treated patients. Eight CAD p atients who were matched to the treated patients for age (+/-3 years), base line low density lipoprotein (+/-5 mg/dL), and triglycerides (+/- 50 mg/dL) but who had never been treated with lipid-lowering drugs were selected as controls. For each of these 32 carotid arteries, luminal and plaque areas w ere measured by planimetry, in a blinded protocol, from the magnetic resona nce image that showed most plaque. Fibrous tissue, calcium, and lipid depos its were identified on the basis of established criteria. Plaque compositio n was estimated as a fraction of total planimetered area. Patients treated with 10-year intensive lipid-lowering therapy, compared with control subjec ts, had significantly lower low density lipoprotein cholesterol levels (84 versus 158 mg/dL, respectively; P<0.001) and higher high density lipoprotei n cholesterol levels (51 versus 37 mg/dL, respectively; P<0.001). As a grou p, treated patients, compared with untreated control subjects, had a smalle r core lipid area (0.7 versus 10.2 mm(2), respectively; P=0.01) and lipid c omposition (1% versus 17%, respectively). Group differences in luminal area (55 [treated] versus 44 [control] mm(2), P=NS) and plaque area (58 [treate d] versus 64 [control] mm(2), P=NS) tended to favor treatment. MRI appears useful for estimating carotid plaque size and composition. Hyperlipidemic C AD patients frequently (97%) have at least moderate (greater than or equal to 40% area stenosis) carotid plaque. In this case-control study, prolonged intensive lipid-lowering therapy is associated with a markedly decreased l ipid content, a characteristic of clinically stable plaques.