Rapid Multi-modal Spectroscopy of Fresh Human Cardiac Tissue detects Fibrosis in IHD and DCM

Purpose: Heart disease is the leading cause of hospitalisations, morbidity, and mortality globally, but there are no point-of-care instruments that can provide metabolic or morphological diagnoses in real time [1]. We demonstrate that point-of-care multimodal spectroscopy using Near-Infrared (NIR) and Raman-Spectroscopy (RS) can be used to diagnose human heart tissue.

Methods: We generated 105 spectroscopic scans, which compromised of 4 NIR and 3 RS scans per sample to generate a “multimodal spectroscopic scan” (MSS) for each heart, done across 15 patients, 5 each from the dilated cardiomyopathy (DCM), Ischemic Heart Disease (IHD) and Normal pathologies. Each of the MSS scans was undertaken in 3 seconds. Data were entered into machine learning (ML) algorithms to assess accuracy of MSS in diagnosing tissue type [2].

Results: The median age was 50 years (IQR 49-52) for IHD, 47 (IQR 45-50) for DCM, 36 (IQR 33-52) for healthy patients (p=0.35), 60% of which were male. MSS identified key differences in IHD, DCM and normal heart samples in regions typically associated with fibrosis and collagen (NIR wavenumbers: 1433, 1509, 1581, 1689, 1725 nm; RS wavelengths: 1658, 1450 and 1330 cm-1). In principal component (PC) analyses, these differences explained 99.2% of the variation in 4 PCs for NIR, 81.6% in 10 PCs for Raman, and 99.0% in 26 PCs for multimodal spectroscopic signatures. Using a stack machine-learning algorithm with combined NIR and Raman data, our model had a precision of 96.9%, recall of 96.6%, specificity of 98.2% and Area-Under-Curve (AUC) of 0.989 (Table 1). NIR and Raman modalities alone had similar levels of precision at 94.4% and 89.8% respectively (Table 1). MSS combined with ML showed accuracy of 90% for detecting dilated cardiomyopathy, 100% for ischemic heart disease and 100% for diagnosing healthy tissue.

Conclusion: Multimodal spectroscopic signatures, based on NIR and Raman spectroscopy, could provide cardiac tissue scans in 3-seconds to aid accurate diagnoses of fibrosis in IHD, DCM and normal hearts.

Identify the source of the funding for this research project: Austin Medical Research Foundation, Austin Hospital, Heidelberg, Australia.