The main cell types of the heart are the cardiomyocytes, fibroblasts, smooth muscle cells, epicardial cells, pericytes and endothelial cells, which form the endocardium and interior lining of vasculature and valves [26]. The heart contains a network of nerve bundles and nerve fibres, some of which are encapsulated by Schwann cells [27]. Pacemaker and Purkinje cells are specialised cardiomyocytes that form the conduction system of the heart. The sinoatrial node (SAN) and the atrioventricular node (AVN) are formed by groups of pacemaker cells which generate electrical impulses and conduct them from the atria to the ventricles, respectively. Immune populations are found in the healthy adult heart including resident macrophages [28–30]. Created with BioRender.com.