Optical Remodeling of the Myocardium in Covid-19: Insights From Polarization-Interference Mapping

Objective assessment of long-term structural alterations in the myocardium following COVID-19 infection remains challenging due to its predominantly subclinical course and the lack of highly sensitive morphological markers. Conventional histological methods are limited in detecting early tissue microstructural disorganization, particularly in fibrillar networks. Recent advances in optical polarimetric techniques, especially Mueller-matrix imaging, provide new opportunities for quantitative evaluation of tissue anisotropy and detection of subtle pathological and necrotic changes. The aim of the study. To identify and assess quantitative polarimetric markers of structural anisotropy in myocardial tissue for the differential diagnosis of long-term post-COVID changes using Mueller-matrix imaging. Materials and methods. The research was based on the analysis of native histological sections of the myocardium obtained from deceased individuals aged 18-40 years. Four representative groups were formed: a control group (no COVID-19 in the past) and two research groups with different durations after COVID-19 infection. Mueller-matrix imaging of linear birefringence (MMI LB) was applied, followed by statistical, correlation, and fractal analysis of coordinate distributions of polarization parameters. Diagnostic performance was assessed using balanced accuracy metrics. Scientific research. The research is a part of the comprehensive research project of the Department of Internal Medicine, Clinical Pharmacology and Occupational Diseases of the Bukovinian State Medical University “Features of the comorbid course of internal organ diseases: mechanisms of mutual aggravation and ways of pharmacological correction” (state registration number 0124U002435; research period: January 1, 2024 – December 31, 2028). Bioethics. The research materials have been reviewed and approved by the bioethics Commission of Bukovinian State Medical University (Protocol №7 dated April 16, 2026). Results. It was found out that statistical (asymmetry Q₃, excess Q₄), correlation (correlation area SK, autocorrelation excess PSD4), and fractal (power spectral density excess PSD₄) markers demonstrate high sensitivity to long-term post-COVID myocardial changes. The highest diagnostic performance was observed for excess-based parameters (Ac up to 95%). Differentiation between groups showed good to very good levels of balanced accuracy for most markers, with slightly lower accuracy in distinguishing later post-COVID periods. A progressive decrease in linear birefringence values and disruption of fibrillar organization were observed with increasing time since infection. Conclusions. Mueller-matrix polarimetric analysis of myocardial tissue enables objective detection of microstructural alterations associated with long-term post-COVID effects. The identified statistical, correlation, and fractal markers demonstrate high diagnostic potential and may be used for differential assessment of myocardial remodeling. Their combined application improves diagnostic accuracy and should be considered alongside established clinical and morphological criteria in the evaluation of post-COVID cardiovascular involvement.