Influence of Fibrotic Tissue Arrangement on Intracardiac Electrograms During Persistent Atrial Fibrillation

Jorge Sánchez1, Mark Nothstein1, Laura Unger1, Javier Saiz2, Beatriz Trénor Gomis2, Olaf Doessel3, Axel Loewe4
1Institue of Biomedical Engineering, Karlsruhe Institute of Technology (KIT), 2Centro de Investigación e Innovación en Bioingeniería (Ci2B), Universitat Politècnica de València, 3Institute of Biomedical Engineering, Karlsruhe Institute of Technology, 4Karlsruhe Institute of Technology (KIT)


During persistent atrial fibrillation, cardiac tissue undergoes electrophys-iological and structural remodeling. Fibrosis in the atrial tissue has an important impact on the myocyte action potential (AP) and its propaga-tion. The objective of this work is to explore the effect of heterogeneities present in the fibrotic tissue on the intracardiac electrogram (EGM). Hu-man atrial myocyte and fibroblast electrophysiology was simulated using mathematical models proposed by Koivumäki et al. representing electri-cal remodeling under peAF as well as a remodeling due to the paracrine effect of the transforming growth factor β1 (TGF-β1). 2D tissue simula-tions were performed using the monodomain approach and EGM forward calculations with the infinite conductor approximation. Furthermore, we varied the density of fibrosis (10%, 20%, 40%) present in a circular re-gion of 2cm diameter. We also varied the ratio of myocytes coupled to myofibroblasts vs. collagen in fibrotic elements (0%-100%, 25%-75%, 50%-50%, 75%-25%, 100%-0%). Results show that increasing the fibro-sis density changes the reentry dynamics from a functional to an anatom-ical reentry due to a block of conduction in regions with high fibrosis density (40%). Higher densities of fibrosis (40%) had a more homoge-nous distribution of Shannon entropy values inside the fibrotic region. EGM morphology was affected by the ratio of myofibroblasts vs. colla-gen. For low myofibroblast ratios (<50%), the mean duration of the ac-tive segments inside the fibrotic region were shorter (43.8 ms, 61.48 ms and 45.83 ms for 10%, 20% and 40% of fibrosis correspondently) com-pared to higher myofibroblast ratios (45.66 ms, 62.24 ms, 48.09 ms for 10%, 20% and 40% of fibrosis correspondently). Our results show that fibrosis arrangement can alter the dynamics of reentry and EGM mor-phology.