Region Specific Modeling of Cardiac Muscle: Comparison of Simulated and Experimental Potentials

Abstract

This article investigates the quantitative predictive capabilities of region-specific models by comparing experimental electrograms obtained from in vivo mapping of the ventricular free wall with those obtained through simulation of a region specific three-dimensional bidomain model that incorporates measured fiber orientations. Epicardial electrograms were recorded from canine left ventricles during and after unipolar pacing using a 528-channel electrode plaque. Fiber directions throughout the tissue were estimated from diffusion-weighted MRI and from pace mapping. Electrograms were computed in the bidomain model with experimentally derived properties during paced activations at the same spatiotemporal resolution as those recorded experimentally. Epicardial potentials from model and experiment were directly compared, and sensitivities of these comparisons to reference electrode location and to the choice of material properties were analyzed. The comparisons performed here demonstrate, that (1) the stimulus artifact can be used to estimate the in vivo myocardial fiber architecture, (2) the correlation between simulated and experimental electrograms decreases with increasing pacing depth, and (3) the quantitative comparisons between bidomain model and experimental data are sensitive to both the description of the fiber architecture, and the location of the unipolar reference electrode, but relatively insensitive to moderate changes in the bidomain conductivities.

Epicardial Fiber Organization in Swine Right Ventricle and Its Impact on Propagation

“…4 -8 It is also thought to affect current distribution during defibrillation shocks 9,10 and thus affect their odds of failure and success. All this explains the persistent interest in structural aspects of myocardial organization 11,12 and motivates further refining the existing knowledge of myocardial fiber architecture.The characteristic feature of myocardial fiber organization is the gradual counterclockwise rotation of fibers throughout the heart wall 1,13-16 with the total rotation angle from endocardium to epicardium across species ranging from 120°( dog) to 180°(pig). 17,18 Although in general the dependence of fiber rotation on depth is considered well established, information about fiber organization near the epicardial surface remains scarce.…”

“…4 -8 It is also thought to affect current distribution during defibrillation shocks 9,10 and thus affect their odds of failure and success. All this explains the persistent interest in structural aspects of myocardial organization 11,12 and motivates further refining the existing knowledge of myocardial fiber architecture.…”

“…Using data averaged from all the tissue samples would likely not reproduce the unusual epicardial activation patterns that we observed experimentally. This emphasizes the need for precise structural descriptions to accurately predict the electrophysiological effects 12 in individual experimental preparations.…”

A parallel solver for anisotropic cardiac models

“…The excitation and recovery phases are influenced by the direction of the myocardial fibers and by the anisotropic conductivity of the intra and extracellular media. While the former phase has been examined in considerable detail both experimentally and numerically (see [1,2,3]), much less is known concerning the latter (see [4,5,6,7]). During a normal heartbeat, the time course of the ventricular transmembrane potential displays mainly three phases having different time and space scales.…”

Stable time integration suppresses unphysical oscillations in the bidomain model

“…For example, the forward Euler (FE) method has been used frequently; see e.g., Muzikant et al [5], Sambelashvili and Efimov [6], ten Tusscher and Panfilov [7], and Tranquillo et al [8]. An investigation of the stability of FE applied to the bidomain model was performed in Puwal and Roth [9].…”