  Understanding the viability of the ischemic myocardial tissue is a critical
issue in determining the appropriate surgical procedure for patients with
chronic heart failure after myocardial infarction (MI). Conventional MI
evaluation methods are; however, preoperatively performed and/or give an
indirect information of myocardial viability such as shape, color, and blood
flow. In this study, we realize the evaluation of MI in patients undergoing
cardiac surgery by Raman spectroscopy under label-free conditions, which is
based on intrinsic molecular constituents related to myocardial viability. We
identify key signatures of Raman spectra for the evaluation of myocardial
viability by evaluating the infarct border zone myocardium that were excised
from five patients under surgical ventricular restoration. We also obtain a
prediction model to differentiate the infarcted myocardium from the
non-infarcted myocardium by applying partial least squares
regression-discriminant analysis (PLS-DA) to the Raman spectra. Our prediction
model enables identification of the infarcted tissues and the non-infarcted
tissues with sensitivities of 99.98% and 99.92%, respectively. Furthermore, the
prediction model of the Raman images of the infarct border zone enabled us to
visualize boundaries between these distinct regions. Our novel application of
Raman spectroscopy to the human heart would be a useful means for the detection
of myocardial viability during surgery.
