Cardiac anisotropy in boundary-element models for the electrocardiogram

Area of Science:

• Biomedical Engineering
• Computational Biology
• Medical Imaging

Background:

• The boundary-element method (BEM) is a common tool for electrocardiogram (ECG) simulation.
• A key limitation of BEM is its difficulty in modeling anisotropic electric conductivity in the myocardial interstitium.
• Previous approaches often simplified anisotropy, focusing only on intracellular aspects or ignoring it.

Purpose of the Study:

• To investigate the effectiveness of a "compound" anisotropy ratio within a BEM framework for ECG simulation.
• To compare BEM results with those from a finite-difference (FD) model capable of handling complex anisotropies.
• To determine if BEM can accurately represent myocardial interstitial anisotropy.

Main Methods:

• ECG simulations were performed using a BEM model incorporating dipole sources and a compound anisotropy ratio.
• Results were compared against a finite-difference model that allowed for uncompromised representation of both intracellular and interstitial anisotropy.
• Different anisotropy models were evaluated: compound anisotropy, intracellular anisotropy only, and fully isotropic.

Main Results:

• A compound anisotropy ratio in the BEM model yielded acceptable agreement with the FD model for given conductivities.
• Fully isotropic BEM models produced significant, unacceptable discrepancies compared to the FD model.
• BEM models considering only intracellular anisotropy showed intermediate accuracy, less accurate than the compound anisotropy approach.

Conclusions:

• The use of a compound anisotropy ratio enables BEM-based ECG models to more accurately incorporate myocardial interstitial anisotropy.
• This approach offers a viable method to improve the fidelity of BEM simulations in electrocardiology.
• BEM, when adapted with compound anisotropy, can overcome previous limitations in simulating anisotropic cardiac tissue conductivity.