Action Potentials|Arrhythmias, Cardiac|Atrial Fibrillation|Computer Simulation|Excitation Contraction Coupling|Genetic Predisposition to Disease|Heart Atria|Heart Conduction System|Humans|Ion Channel Gating|Models, Cardiovascular|Models, Genetic|Mutation|Myocardial Contraction|Potassium|Potassium Channels, Inwardly Rectifying