Determination of Human Coronary Artery Composition by Raman Spectroscopy

Abstract

Background We present a method for in situ chemical analysis of human coronary artery using near-infrared Raman spectroscopy. It is rapid and accurate and does not require tissue removal; small volumes, ≈1 mm ³ , can be sampled. This methodology is likely to be useful as a tool for intravascular diagnosis of artery disease. Methods and Results Human coronary artery segments were obtained from nine explanted recipient hearts within 1 hour of heart transplantation. Minces from one or more segments were obtained through grinding in a mortar and pestle containing liquid nitrogen. Artery segments and minces were excited with 830 nm near-infrared light, and Raman spectra were collected with a specially designed spectrometer. A model was developed to analyze the spectra and quantify the amounts of cholesterol, cholesterol esters, triglycerides and phospholipids, and calcium salts present. The model provided excellent fits to spectra from the artery segments, indicating its applicability to intact tissue. In addition, the minces were assayed chemically for lipid and calcium salt content, and the results were compared. The relative weights obtained using the Raman technique agreed with those of the standard assays within a few percentage points. Conclusions The chemical composition of coronary artery can be quantified accurately with Raman spectroscopy. This opens the possibility of using histochemical analysis to predict acute events such as plaque rupture, to follow the progression of disease, and to select appropriate therapeutic interventions.