β‐Carotene enhances plaque detection by fluorescence attenuation in an atherosclerotic rabbit model

Improved detection of plaque during cardiovascular procedures could enhance the outcome of diagnosis and therapy. We evaluated a new method to stain plaque using a special intravenous preparation of β‐carotene (β‐C) in an in vivo model. β‐C was used to enhance the absorption coefficient of plaque and decrease the laser–induced fluorescence emission. Using this approach the difference in fluorescence emission was accentuated between normal artery and atherosclerotic plaque. Twenty‐nine NZW rabbits were divided into five groups, each receiving a different intervention. This included the administration of β‐C to rabbits on a normal or a high cholesterol diet, with or without endothelial debridement. Aortae were examined grossly, by histology, and relative total fluorescence was detected at 886 sites using 488 nm or 514 nm laser excitation. At 488 nm excitation, unstained plaque attenuated total fluorescence twice as much as normal controls (7.55± 1.46 vs. 15.06 ± 3.12; P <0.0001); β‐C stained plaque attenuated total fluorescence 17 times more than normal controls (0.89 ± 0.29 vs. 15.06 ± 3.12; P <0.0001). Total fluorescence from unstained plaque was eight times greater than plaque stained with β‐C (7.55 ± 1.46 vs. 0.89 ± 0.29; P <0.0001). Results obtained using 514 nm excitation were similar. The attenuation effect persisted up to 8 weeks following β‐C administration. Thus, β‐C stained plaque displayed fluorescence attenuation, which suggests that pretreatment with β‐C may greatly enhance plaque detection. This may be useful as a guide during‐plaque removal procedures. © 1993 Wiley‐Liss, Inc.