Arrhythmogenicity of cardiac fibrosis: fractal measures and Betti numbers

Infarction- or ischaemia-induced cardiac fibrosis can be arrythmogenic. We use mathematcal models for diffuse fibrosis ($mathcal{DF}$), interstitial fibrosis ($mathcal{IF}$), patchy fibrosis ($mathcal{PF}$), and compact fibrosis ($mathcal{CF}$) to study patterns of fibrotic cardiac tissue that have been generated by new mathematical algorithms. We show that the fractal dimension $mathbb{D}$, the lacunarity $mathcal{L}$, and the Betti numbers $beta_0$ and $beta_1$ of such patterns are textit{fibrotic-tissue markers} that can be used to characterise the arrhythmogenicity of different types of cardiac fibrosis. We hypothesize, and then demonstrate by extensive textit{in silico} studies of detailed mathematical models for cardiac tissue, that the arrhytmogenicity of fibrotic tissue is high when $beta_0$ is large and the lacunarity parameter $b$ is small.