RYR2 and atrial fibrillation: Within the hyperphosphorylated context of AF, the increase in CaMKII phosphorylation of RyR2, would maintain SR Ca2+ load by increasing Ca2+ sparks and SR Ca2+ leak avoiding proarrhythmic effects of Ca2+ waves and ITI, which at least at a certain point of the AF progression would need to be accompanied by an attempted restriction of the strong PKA phosphorylation by PDEs in this compartment.