Impact of mechanical deformation on pseudo-ECG: a simulation study.

AIMS: Electrophysiological simulations may help to investigate causes and possible treatments of ventricular conduction disturbances. Most electrophysiological models do not take into account that the heart moves during the cardiac cycle. We used an electro-mechanical model to study the effect of mechanical deformation on the results of electrophysiological simulations. METHODS AND RESULTS: Pseudo-electrocardiogram (ECG) were generated from the propagation of electrical signals in tissue slabs undergoing active mechanical deformation. We used the mono-domain equation for electrophysiology with the Bueno-Orovio ionic model and a fully incompressible Guccione-Costa hyperelastic law for the mechanics with the Nash-Panfilov model for the active force. We compared a purely electrophysiological approach (PE) with mono-directional (MD) and bi-directional (BD) electromechanical coupling strategies. The numerical experiments showed that BD and PE simulations led to different S- and T-waves. Mono-directional simulations generally approximated the BD ones, unless fibres were oriented along one short axis of the slab. When present, notching in the QRS-complex was larger in MD than in BD simulations. CONCLUSIONS: Tissue deformation has to be taken into account when estimating the S- and T-wave of the ECG in electrophysiological simulations.

Verification of cardiac mechanics software: benchmark problems and solutions for testing active and passive material behaviour.

Models of cardiac mechanics are increasingly used to investigate cardiac physiology. These models are characterized by a high level of complexity, including the particular anisotropic material properties of biological tissue and the actively contracting material. A large number of independent simulation codes have been developed, but a consistent way of verifying the accuracy and replicability of simulations is lacking. To aid in the verification of current and future cardiac mechanics solvers, this study provides three benchmark problems for cardiac mechanics. These benchmark problems test the ability to accurately simulate pressure-type forces that depend on the deformed objects geometry, anisotropic and spatially varying material properties similar to those seen in the left ventricle and active contractile forces. The benchmark was solved by 11 different groups to generate consensus solutions, with typical differences in higher-resolution solutions at approximately 0.5%, and consistent results between linear, quadratic and cubic finite elements as well as different approaches to simulating incompressible materials. Online tools and solutions are made available to allow these tests to be effectively used in verification of future cardiac mechanics software.

Validation of a heterogeneous elastic-biphasic model for the numerical simulation of the PDL.

An elastic-biphasic model for the simulation of the periodontal ligament (PDL) and the adjacent tooth is presented and investigated. The PDL is modelled as a biphasic material following the work of Ehlers and Markert (2001 ), whereas the tooth is modelled as a linear elastic body. A spatial discretisation scheme is proposed based on mixed finite elements for the spatial discretisation. Due to nonlinearity in the model, a predictor-corrector scheme is employed as a temporal discretisation scheme. In order to validate the PDL model, in vitro measurements are compared with numerical simulations. The numerical simulations are performed using geometries resulting from micro-CT scanner of the same porcine tooth, which was employed for the in vitro measurements.