Electroanatomical Characterization of Atrial Microfibrosis in a Histologically Detailed Computer Model

Abstract

Fibrosis is thought to play an important role in formation and maintenance of atrial fibrillation (AF). The propensity of fibrosis to increase AF vulnerability depends not only on its amount, its texture plays a crucial role as well. While the detection of fibrotic tissue patches in the atria with extracellular recordings is feasible based on the analysis of electrogram fractionation, as used in clinical practice to identify ablation targets, the classification of fibrotic texture is a more challenging problem. This study seeks to establish a method for the electro-anatomical characterization of the fibrotic textures based on the analysis of electrogram fractionation. The proposed method exploits the dependency of fractionation patterns on the incidence direction of wavefronts which differs significantly as a function of texture. A histologically detailed computer model of the right atrial isthmus was developed for testing the method. A stimulation protocol was conceived which generated various incidence directions for any given recording site where electrograms were computed. A classification method is derived then for discriminating three types of fibrosis, no fibrosis (control), diffuse and patchy fibrosis. Simulation results showed that electrogram fractionation and amplitudes and their dependency upon incidence direction allow a robust discrimination between different classes of fibrosis. Finally, to minimize the technical effort, sensitivity analysis was performed to identify a minimum number of incidence directions required for robust classification.

Reentry and Ectopic Pacemakers Emerge in a Three-Dimensional Model for a Slab of Cardiac Tissue with Diffuse Microfibrosis near the Percolation Threshold

“…Propagation near fibrosis is associated with fractionated electrograms [31, 32]. Two-dimensional computer simulations have already given valuable insights about the relation between microfibrosis and complex fractionated electrograms [13, 15, 19]. …”

“…The extracellular potential is computed using the large volume conductor approximation [15]. To this end, we integrate all the currents in the tissue with respect to the position of the electrode: where is the distance from the electrode to the particular point of the tissue and A is a constant including the ratio of extracellular and the intracellular resistivities.…”

“…This type of fibrosis is known as microfibrosis due to the microscopic scale of the heterogeneities [13–15]. …”

“…Recent clinical studies of guided CFAE ablation revisited the benefits and risks of this procedure and clearly suggest that further investigation on this topic is required [34–36]. Different computer simulations have also already given valuable insights into how the microstructure of cardiac tissue, specifically microfibrosis, and CFAE are related [13, 15]. …”

Microscopic Isthmuses and Fibrosis Within the Border Zone of Infarcted Hearts Promote Calcium-Mediated Ectopy and Conduction Block

“…As illustrated in Figure 7, fibrosis disrupts the intracellular matrix creating complex microscopic pathways through which the wavefront has to travel following zig-zag courses [42]. Such structural alterations lead to: (1) conduction slowing, a factor known to promote arrhythmias by shortening the wavelength [43]; and (2) electrogram fractionation [44] typically used in clinical practice to identify ablation targets [45]. Fibrosis has also been suggested to promote triggered activity by reducing the protective sourcesink mismatch of tightly coupled tissue [15].…”