C-NMR Spectroscopy of Human Atherosclerotic Lesions Relation Between Fatty Acid Saturation, Cholesteryl Ester Content, and Luminal Obstruction

Previous investigations have used C-nuclear magnetic resonance (NMR) spectroscopy to demonstrate the similarities between lipoproteins and the mobile lipids of atheroma. In this study, we tested the hypothesis that "CNMR changes are related to indices of histological severity. We classified 20 human arteries according to their obstruction ratio (OR), defined as the ratio of the plaque area to the area delimited by the external elastic lamina. In group A, OR was <40%, and in group B, OR was >40%. We analyzed at 9.4 T the resonances of unsaturated (UFA) and polyunsaturated (PUFA) carbons, the resonances of the carbons 19 and 21 (C19,C21) of cholesteryl esters (CE), the methine carbon peak of fatty acids (CH2)n, the choline peak from phospholipids (PL), and the glycerol peak from triglyceride (TG). The UFA/PUFA, UFA/(CH2)0, and PUFA/(CH2)n ratios are Except for chemical extraction, no technique is effective in characterizing the lipid component of an atheromatous plaque. Intravascular ultrasound or angioscopy in vivo and histopathological examination in vitro generate high-resolution structural information but lack good data with respect to chemical composition. The need to detect and characterize all stages of atheroma development has become more important inasmuch as unstable coronary syndromes or strokes may result from arterial lesions that have not yet become severely stenotic. The rupture of atheromatous plaques is a major contributor to the development of myocardial infarction, and it has been demonstrated that plaque vulnerability is dependent on the biochemical characteristics of the lipid pool. Natural-abundance C-nuclear magnetic resonance (NMR) spectroscopy allows the nondestructive characterization of lipid chemical composition. Because of its broad chemical shift bandwidth, C-NMR provides more information regarding chemical constituents than 'H-NMR and has been used for structural and dynamic studies of cholesteryl esters (CE), triglycerides (TG), and phospholipids (PL)."Hamilton and Cordes examined plasma lipoproteins and intact athReceived November 11, 1993; revision accepted August 25, 1994. From the Cardiac Unit, NMR Center, and Department of Pathology, Harvard Medical School and Massachusetts General Hospital, Boston. Reprint requests to J.-F. Toussaint, MD, c/o Dr Howard Kantor, Cardiac Unit, Massachusetts General Hospital, Jackson 1410, 32 Fruit St, Boston, MA 02114. © 1994 American Heart Association, Inc. markers of fatty acid saturation. (C19,C21)/(CH2)n, choline/ (CH2)n, and glycerol/(CH2)n are indices of CE, PL, and TG content, respectively. UFA/PUFA in group A is 1.15±0.34 versus 1.63±0.32 in group B (P=.005). PUFA/(CH2)n is 0.26+0.10 in group A versus 0.16±0.04 in group B (P=.O49). C19,C21/(CH2)n in group A is 0.32±0.15 versus 0.63±0.23 for group B (/=.003). No significant difference was found in UFA/(CH2)n or in the TG or PL ratios. C spectral examination of human atherosclerosis demonstrates decreased resonances for polyunsaturated fatty acyl chains and cholesteryl esters with increasing obstruction. (Arterioscler Thromb. 1994;14:19S1-1957.)