Development of a rapid and novel diagnostic technique for cardiac amyloidosis using Raman spectroscopy

Although the prognosis of cardiac amyloidosis has improved with the development of therapies, the time required for disease typing remains a critical issue. We investigated the potential of Raman spectroscopy for the more rapid diagnosis and typing of cardiac amyloidosis. Heart biopsies were collected from patients with the AL (4) and ATTR (4) types of cardiac amyloidosis, and tissue sections were subjected to Raman microscopy. A principal component analysis (PCA) of spectral data was performed and receiver operating characteristic (ROC) curves were created to confirm the accuracy of discriminating between amyloid-deposition and non-deposition sites, and between AL and ATTR. The steep peak at 1680 cm^-1, reflecting the β-sheet structure, was useful for detecting the amyloid-deposition region. By restricting the spectral analysis to amyloid-deposition sites, AL and ATTR were discriminated by principal components with a characteristic broad peak at 1520-1540 cm^-1, which was also observed in the Raman spectrum of AL, but not ATTR. The area under ROC curve discriminating AL and ATTR was 0.78. PCA of the Raman spectra of cardiac biopsies has the potential not only to detect amyloid-deposition sites in tissue but also to rapidly discriminate between the AL and ATTR types of cardiac amyloidosis.