Complexity Forum: Kim Christensen (Imperial College)
Speaker: Kim Christensen (Imperial College)
Title: A simple model for atrial fibrillation
Abstract: Atrial fibrillation (AF) is the most common abnormal heart rhythm and is the single biggest cause of stroke. Ablation, where regions of the atrial muscle are destroyed, is applied largely empirically and can be curative in some patients but with overall disappointing clinical success rate. We take a physicist's approach and devise the simplest possible model where the complex phenomenon of AF is an emergent property. We provide novel mechanistic insight into the propagation of activation wavefronts on a structure which mimics the basic architecture of heart muscle. We show that as the characteristics of the structure is modified by age-related changes, AF emerges. The simplicity of the model allow us to identify principal regions responsible for the initiation and maintenance of AF, the ablation of which terminates AF. Moreover, we predict that increasing the refractory period, as is done by particular anti-arrhythmic agents, may not only terminate the fibrillation but also reduces the risk of inducing fibrillation in the first place. Hence our model provides clinically testable insights into AF which might inform ablation therapies and arrhythmic risk assessment. The model is also interesting from a purely statistical physics point of view. The transition from regular to fibrillatory behaviour is technically a finite-size effect but not trivially so, and therefore it will be present in systems of all sizes.