Phase Singularities in a Cardiac Patch Model with a Non-conductive Fibrotic Area during Atrial Fibrillation

In-silico cardiac patches with a non-conductive fibrotic areas were used to investigate the occurrence and characteristics of rotors described by phase singularities (PSs). A rotor was generated in a virtual tissue patch represented by a Courtemanche model adapted to mimic AF conditions. Non-conductive fibrotic elements were incorporated around the center of the patch (densities of 20%, 30%, and 40%). Electrograms (EGMs) were calculated and their phase was determined using Hilbert transform. PSs were detected and PS density maps (PSDMs) were generated. Six attributes were used to investigate bipolar EGMs obtained from the original signals: sample entropy (SampEn), determinism (DET), peak-to-peak (PP), wave similarity (WS), organization index (OI), and cycle length (CL). 77.1% of the PSs occurred inside the fibrotic region - with a higher density in the border zone - for 20% density; 99.8% for 30%; 99.7% for 40%. SampEn was significantly higher in regions with PSDM=5, while DET, PP, and WS were significantly lower (P<0.0001). PSs tended to meander outside the fibrotic area for lower fibrotic density. Bipolar EGM attributes offer a complementary way for rotor detection in the presence of non-conductive fibrosis.