![]() As a result, the conduction system is rarely presented in the attitudinally correct position 28. This makes the placement of the analysed volumes back into the context of the whole heart difficult, and prone to error. Such destructive analysis is further limited by the requirement to use preparations of an isolated part of a given heart, small enough for routine fixation and sectioning. Any such technique is limited in 3D resolution by the distance between successive sections, typically 60–340 µm 23, 25. Our present understanding of sinus node and atrioventricular node morphology owes much to painstaking reconstruction of 2D serial histology 22, 23, 24, 25, 26, 27. Depiction of 3D cellular alignment, therefore, should ideally be generated from image data as close as possible to this order of spatial resolution. Individual cardiomyocytes are of the order of a few tens of microns in dimension, and the path and velocity of conduction is known to be dictated by their orientation 21. In order to produce simulations with the highest possible structural fidelity, models must include (1) accurate morphological representations of the human cardiac conduction system and its interface with the working myocardium, and (2) the 3D orientation of the cardiomyocytes within these tissues. The fidelity of the current models, however, is compromised by the use of simplified geometric data sets from disparate species 16, 18, 19, 20. Efforts have been made to produce detailed electrophysiological data to inform such models 14, 15, 16, 17. Up to now, this information has been absent from the literature.īiophysically-detailed mathematical models are powerful tools with which to investigate normal and pathological cardiac conduction. Knowledge of the 3D micro-anatomy of the human cardiac conduction system, therefore, is crucial. We have shown previously the 3D distribution of the cardiac conduction system in animal hearts 9, 10, 11, 12, along with the link between its molecular and micro-anatomical remodelling in disease 13. The onset of such conditions may be attributed to age, genetic predisposition, lifestyle, myocardial remodelling, fibrosis of tissues, and history of surgical procedures. They also occur in almost 40% of patients attending cardiology outpatient clinics 7. The main components of the cardiac conduction system are the sinus node of the right atrium, which is the primary pacemaker the atrioventricular conduction axis, which normally forms the only pathway allowing excitation to pass between the atria and ventricles and the Purkinje network, which allows fast and coordinated conduction within the ventricles 3, 4.Ĭardiac arrhythmias and conduction disturbances affect 0.1% of adults younger than 55 years old, increasing to 9% in those older than 80 years 5, 6, 7, 8. They act also to conduct impulses throughout the heart, in a rapid and coordinated fashion 1. They have the ability spontaneously to generate electrical impulses and to function as pacemakers 1, 2. The specialised cardiomyocytes, known as the cardiac conduction system, are anatomically discrete from the working myocardium, and cannot be visualised using traditional non-invasive techniques. Such data presented as 3D images or 3D printed models, will inform discussions between medical teams and their patients, and aid the education of medical and surgical trainees. ![]() We also offer a practical method for investigation of remodelling in disease, and thus, virtual pathology and archiving. By showing the precise 3-dimensional relationships between the cardiac conduction system and surrounding structures, we provide new insights relevant to valvar replacement surgery and ablation therapies. Since the rate of depolarisation is dictated by cardiac microstructure, and the precise orientation of the cardiomyocytes, our data should improve the fidelity of mathematical models. The data presented should have multidisciplinary impact. We have incorporated the high-resolution anatomical data into mathematical simulations of cardiac electrical depolarisation. These data show that commonly accepted anatomical representations are oversimplified. We show that cardiomyocyte orientation can be extracted from these datasets at spatial resolutions approaching the single cell. Here, using contrast enhanced micro-computed tomography, we present, in attitudinally appropriate fashion, the first 3-dimensional representations of the cardiac conduction system within the intact human heart. Cardiac arrhythmias and conduction disturbances are accompanied by structural remodelling of the specialised cardiomyocytes known collectively as the cardiac conduction system.
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