Session MD.3

Electrogram Fractionation Caused by Microfibrosis: Insights from a Microstructure Model

V Jacquemet*, B Robinson, CS Henriquez

Duke University
Durham, NC, USA

Complex fractionated atrial electrograms are used as potential targets for catheter ablation therapy of atrial fibrillation. Although fibrosis has been associated with the presence of fractionated electrograms, characterizing the substrate through inspection of electrograms is challenging. The purpose of this study is to develop a computational framework to determine how progression of microfibrosis leads to changes in electrogram morphology and degree of fractionation.
A 2D microstructural tissue model of size 8.64x2.88mm (discretization 15x10um) composed of 8354 cells with varying shapes and sizes was created. Microfibrosis was introduced as a set of collagenous septa disconnecting transverse coupling. These septa were aligned with fiber orientation and randomly distributed over the tissue, covering 10%, 20% or 30% of the side-to-side contact area between the myocytes, and having an average length of 165um, 315um, 630um or 945um. For each of the 12 cases, 6 different realizations of the random distribution were generated. Transverse plane wave propagations were simulated using the Courtemanche kinetics. Unipolar electrograms were computed at 87 sites. Their morphology was characterized by their amplitude, asymmetry and number of deflections (number of local maxima and minima).
Along with the progression of microfibrosis, wavefront propagation became more discrete and transverse conduction velocity slowed down from 30 cm/s (control) to 7.5 cm/s. Increasing microfibrosis density (D) reduced electrogram average amplitude by 15%, 27%, 38% for D=10%, 20%, 30%. As the average length (L) of collagenous septa was increased, a larger spatial variability in electrogram morphology was observed. The occurrence of positive asymmetric complexes was more common (40% for L>500um vs 18% for L<500um, 0% at control). The average number of deflections increased (8.3+/-1.0 for L>500um vs 5.7+/-1.2 for L<500um, 3 at control), indicating a higher degree of fractionation. In conclusion, changes in cell-to-cell coupling at the microscale have a significant impact on electrogram morphology. Microstructure computer models may assist the interpretation of electrograms to extract more information about the arrhythmogenic substrate.

(Abstract Control Number: 133)