RYR2 and hydrops fetalis: Although protein kinase A (PKA) has also been shown to phosphorylate RyR2 channels, inconsistent findings regarding the arrhythmic effect of PKA hyperphosphorylation of RyR2 at Ser2809 in HF were reported [3, 7, 16, 85, 90, 110, 120, 135, 138, 140, 154], further suggesting the key role of CaMKIIδ in HF-evoked arrhythmias.