Heterogeneous three-dimensional anatomical and electrophysiological model of human atria

Abstract

Investigating the mechanisms underlying the genesis and conduction of electrical excitation in the atria at physiological and pathological states is of great importance. To provide knowledge concerning the mechanisms of excitation, we constructed a biophysical detailed and anatomically accurate computer model of human atria that incorporates both structural and electrophysiological heterogeneities. The three-dimensional geometry was extracted from the visible female dataset. The sinoatrial node (SAN) and atrium, including crista terminalis (CT), pectinate muscles (PM), appendages (APG) and Bachmann's bundle (BB) were segmented in this work. Fibre orientation in CT, PM and BB was set to local longitudinal direction. Descriptions for all used cell types were based on modifications of the Courtemanche et al. model of a human atrial cell. Maximum conductances of Ito, IKr and ICa,L were modified for PM, CT, APG and atrioventricular ring to reproduce measured action potentials (AP). Pacemaker activity in the human SAN was reproduced by removing IK1, but including If, ICa,T, and gradients of channel conductances as described in previous studies for heterogeneous rabbit SAN. Anisotropic conduction was computed with a monodomain model using the finite element method. The transversal to longitudinal ratio of conductivity for PM, CT and BB was 1:9. Atrial working myocardium (AWM) was set to be isotropic. Simulation of atrial electrophysiology showed initiation of APs in the SAN centre. The excitation spread afterwards to the periphery near to the region of the CT and preferentially towards the atrioventricular region. The excitation extends over the right atrium along PM. Both CT and PM activated the right AWM. Earliest activation of the left atrium was through BB and excitation spread over to the APG. The conduction velocities were 0.6ms-1 for AWM, 1.2ms-1 for CT, 1.6ms-1 for PM and 1.1ms-1 for BB at a rate of 63bpm. The simulations revealed that bundles form dominant pathways for atrial conduction. The preferential conduction towards CT and along PM is comparable with clinical mapping. Repolarization is more homogeneous than excitation due to the heterogeneous distribution of electrophysiological properties and hence the action potential duration.

Three‐dimensional Integrated Functional, Structural, and Computational Mapping to Define the Structural “Fingerprints” of Heart‐Specific Atrial Fibrillation Drivers in Human Heart Ex Vivo

“…The computed atrial wall thickness in the left atrial appendage was found to be affected by the extremely complex and trabecular atrial anatomy,30 and thus wall thickness of the left atrial appendage was not reported. The atrial cellular activation model is based on a simplified Fenton‐Karma model, not biophysics‐based cellular models10, 12 for the sake of computational efficiency, although it was validated by optical mapping data in this study and widely used by us15, 27 and others 28. Additionally, because of a single uniform cellular model used across the atria in the computer model, APDs in some regions (eg, distal side of PV sleeves) may not match well between modeling and optical mapping.…”

Nonlinear physics of electrical wave propagation in the heart: a review

“…Examples of such studies are the San Diego rabbit model [117] and the Auckland swine model [118]. Similarly, detailed models of human atria are also available [119]. More recently, individual geometries of the hearts are obtained by magnetic resonance imaging like e. g. in the Oxford rabbit model [29].…”

Modeling Defibrillation

“…FEM and FVM are both very well suited for spatial discretizations of complex geometries with smooth representations of the boundaries, which is a key feature when polarization patterns induced via extracellularly applied currents are to be studied. Both FVM and FEM have been used to model electrical activity in anatomical realistic models of the atria (Harrild & Henriquez, 2000;Seemann et al, 2006;Vigmond et al, 2004;Virag et al, 2002) as well as the ventricles (Ashihara et al, 2008;Plank et al, 2009;Potse et al, 2006;Ten Tusscher et al, 2007). Mesh generation requirements are similar for both techniques, that is, the domain of interest has to be tessellated into a set of non-overlapping and conformal geometric primitives (Fig.…”

“…5). With the FVM, quadrilaterals in 2D (Harrild & Henriquez, 1997) and hexahedral elements in 3D (Harrild & Henriquez, 2000;Trew, Le Grice, Smaill & Pullan, 2005) have been preferred, whereas with the FEM, triangles and quadrilaterals were used in 2D and tetrahedral or hexahedral elements in 3D (Munteanu et al, 2009;Seemann et al, 2006). Typically, monolithic meshes consisting of one element type only were used, but exception exist Rocha et al, 2011) where hybrid meshes consisting of tetrahedra, hexahedra, pyramids and prisms were used.…”