Wave front fragmentation due to ventricular geometry in a model of the rabbit heart

Abstract

The role of the heart's complex shape in causing the fragmentation of activation wave fronts characteristic of ventricular fibrillation (VF) has not been well studied. We used a finite element model of cardiac propagation capable of simulating functional reentry on curved two-dimensional surfaces to test the hypothesis that uneven surface curvature can cause local propagation block leading to proliferation of reentrant wave fronts. We found that when reentry was induced on a flat sheet, it rotated in a repeatable meander pattern without breaking up. However, when a model of the rabbit ventricles was formed from the same medium, reentrant wave fronts followed complex, nonrepeating trajectories. Local propagation block often occurred when wave fronts propagated across regions where the Gaussian curvature of the surface changed rapidly. This type of block did not occur every time wave fronts crossed such a region; rather, it only occurred when the wave front was very close behind the previous wave in the cycle and was therefore propagating into relatively inexcitable tissue. Close wave front spacing resulted from nonstationary reentrant propagation. Thus, uneven surface curvature and nonstationary reentrant propagation worked in concert to produce wave front fragmentation and complex activation patterns. None of the factors previously thought to be necessary for local propagation block (e.g., heterogeneous refractory period, steep action potential duration restitution) were present. We conclude that the complex geometry of the heart may be an important determinant of VF activation patterns. (c) 2002 American Institute of Physics.

Critical mass hypothesis revisited: role of dynamical wave stability in spontaneous termination of cardiac fibrillation

“…Primarily because of computational constraints, we used relatively simple action potential and tissue models, rather than a physiologically detailed late-generation action potential model (20,24,32) or an anatomically realistic tissue model (18,46,52,57). These simplifications may affect the results and conclusions drawn from our simulations.…”

“…In fact, the less frequent self-termination of VF than AF may be due to larger tissue mass as well as more complex 3-D structure and topology. Computer simulations of a realistic (57) or a simplified (46) ventricle model are necessary to understand how dynamical instability interacts with the topology of the ventricles in the maintenance of fibrillation and to validate whether conclusions from simulations of 2-D and 3-D slabs are still valid.…”

“…Ca 2+ cycling dynamics can also create dynamical instabilities (8,13,37,49), which may be very important for the maintenance of fibrillation, as demonstrated in the atrium (9,19). 2) We used simple 2-D and 3-D monodomain tissue models, which are much simpler than the bidomain structures and geometries of the real atria and ventricles, which in turn may affect the spiral wave dynamics (18,46,48,52,57) and the maintenance of fibrillation. Our observation that T s is determined by area-to-perimeter ratio was based on 2-D rectangular tissue geometries.…”

A simulation study of the effects of cardiac anatomy in ventricular fibrillation

“…Indeed, even in normal cardiac tissue without significant fibrosis, infarction, or ischemia, VF can be induced by a sufficiently large electrical stimulus, and it is still unclear what factors cause wavebreak. For example, one important aspect of the gross anatomy of the heart is the shape of the ventricular cavities, the interventricular septum, and the overall geometry of the lower heart (8). Another critical aspect of cardiac gross anatomy is the anisotropy of electrical conduction, which is created by the twisted distribution of cardiac fibers through the myocardial wall (9).…”

Computational modeling of cardiac electrophysiology: A novel finite element approach

“…About a decade ago, Aliev and Panfilov [18] and Fenton and Karma [19] suggested the numerical analysis of traveling excitation waves with the help of explicit finite difference schemes. At the same time, one of the first finite element algorithms for cardiac action potential propagation was proposed by Rogers and McCulloch [20][21][22]. They suggested combined Hermitian/Lagrangian interpolation for the unknowns.…”