RYR2 and atrial fibrillation: Ryanodine receptor 2 (RyR2) channels that play a key role in sarcoplasmic reticulum release of calcium with myocyte depolarization are dysfunctional in disease states such as heart failure and atrial fibrillation where the cardiac chambers are known to distend and stretch (Hove-Madsen et al., 2004; Fischer et al., 2013).