In Vivo Temperature Heterogeneity of Atherosclerotic Plaques Is Determined by Plaque Composition

Abstract

Background-Temperature heterogeneity of atherosclerotic plaques has been associated with macrophage accumulation in ex vivo studies. We investigated in vivo whether modifying the cell composition of rabbit atherosclerotic plaques by dietary cholesterol lowering can influence temperature heterogeneity. Methods and Results-Twenty New Zealand rabbits were randomized to either a normal (nϭ10) or cholesterol-rich (0.3%) diet (nϭ10) for 6 months. Thereafter, intravascular ultrasound and intravascular catheter-based thermography of the surface of aortic arch and descending aorta were performed in all animals. Ten control and 5 hypercholesterolemic rabbits were euthanized, and their aortas were analyzed histologically. The 5 remaining rabbits received a normal diet for 3 months and underwent repeat ultrasound and thermography before euthanasia followed by histology. Ex vivo temperature was measured in 3 additional rabbits at 6 months to correlate local temperature with local plaque composition. In control animals, plaque formation and temperature heterogeneity were absent. In hypercholesterolemic rabbits, plaque formation was prominent in the thoracic aorta. Plaques were composed of fibromuscular tissue and contained, underneath endothelial cells, an accumulation of foam cells of macrophage origin. Temperature heterogeneity was markedly elevated and increased with plaque thickness. Importantly, after 3 months of cholesterol lowering, plaque thickness remained unchanged, but temperature heterogeneity was significantly decreased. This paralleled plaque histology, which showed a marked loss of macrophages. The ex vivo experiments demonstrated the relation between local temperature and local total macrophage mass. Conclusions-In vivo temperature heterogeneity of rabbit atherosclerotic plaques is determined by plaque composition. In vivo thermography may have important clinical implications in the assessment of plaque composition.

Frontiers in Intravascular Imaging Technologies

“…70 In that study, the aortic segments of hypercholesterolemic rabbits showed significant heterogeneity that was associated with increased plaque thickness by IVUS. After 3 months of dietary cholesterol lowering, however, this heterogeneity decreased significantly, whereas plaque thickness remained unchanged.…”

Inflammation as a Cardiovascular Risk Factor

“…20 Using this catheter, which is capable of detecting temperature heterogeneity to 0.01°C in various conditions of blood flow, temperature, and luminal stenosis, such temperature heterogeneity has been detected in atherosclerotic dogs and rabbits, in which increased temperature was correlated with increased total macrophage mass. 19,21 Using a thermography catheter, Stefanadis et al 22 studied 90 subjects, 15 of whom had stable angina, 15 who had unstable angina (UA), and 15 who had acute myocardial infarction (MI). Another 45 patients had normal coronary arteries.…”

Fluorescence lifetime in cardiovascular diagnostics

“…[3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] Several optical spectroscopy techniques have been already used in atherosclerosis research, such as Raman, near-infrared ͑NIR͒, diffuse reflectance NIR, and fluorescence spectroscopy. Reviews of these techniques and studies include those by Moreno and Muller, 19 Fayad and Fuster, 20 MacNeill et al, 3 Pasterkamp et al, 21 and Honda and Fitzgerald.…”