Atrial fibrillation (AF) is the most common heart rhythm disturbance. 25% of the New Zealand population who are 40 years old will develop AF in their lifetime. Recurring sudden incidents of AF can be prevented by clinical intervention. However, the mechanisms responsible for persistent AF (PeAF) are poorly understood and treatment outcomes are disappointing. Computer models provide a powerful framework for investigating the exact mechanisms that contribute to the initiation and maintenance of PeAF. This research proposal is built on collaboration between University of Auckland and the University of Michigan. We seek to use i) large animal experimental models that enable the effects of electrical and structural remodelling to be differentially altered and ii) anatomically-detailed in-silico models of atrial activation that can be related directly to the experimental setting, but support more systematic investigation of AF. The proposal will produce research outputs of the highest international quality.