Novel micro-computed tomography contrast agents to visualise the human cardiac conduction system and surrounding structures in hearts from normal, aged, and obese individuals: Iodine and graphene oxide – visualising human conduction system in normal, aged, and obese hearts

Research purpose: The cardiac conduction system (CCS) regulates electrical impulses across the heart and cardiac arrhythmias cause structural remodelling of the CCS. Since its discovery over a century ago, the precise anatomy and differences between the human CCS in healthy, aged, and obese human hearts has remained relatively unknown. Using iodine potassium-iodide (I₂KI) and graphene oxide (GO) as contrast agents for high-resolution micro-computed tomography (micro-CT), we explored and identified the anatomies of whole healthy, aged, and obese hearts, including their CCS. Basic procedures: Human specimens were obtained from 5 post-mortem hearts, under local ethical rules and stored in the Dobrzynski laboratory, under the Human Tissue Act 2004. Specimens were stained with I₂KI or GO contrast agents before scanning with micro-CT. Data obtained from micro-CT was uploaded onto Amira v6.5 software for analysis, 3-dimensional reconstructions, and segmentation of relevant structures. Following micro-CT analyses, tissue blocks were cryosectioned and stained for histological assessments. Main findings: There are obvious anatomical structural differences between the healthy, aged and obese hearts. Compared to the healthy heart, the aged heart and obese heart had larger chambers; thicker myocardial walls; thicker blood vessels; more extensive nodal regions and connective tissue; more epicardial fat; and fewer Purkinje fibres. Our use of I₂KI and GO as contrast agents for high-resolution micro-CT scanning contribute to - and expands - the current understanding of CCS structural variations between healthy, aged and obese human hearts.These current and novel techniques can have key impacts on our anatomical understandings for current treatments for cardiovascular disease and the development of mathematical models of aged and diseased hearts. Thus ultimately aiding in the reduction of cardiac morbidities and reduction of patient death rate.