RYR2 and hydrops fetalis: An increase of RyR2 open probability, as may occur during HF in ventricular myocytes, also leads to an increased amount of Ca2+ sparks, resulting in an increased diastolic [Ca2+]i concentration and reduced SR Ca2+ content since more Ca2+ is pumped out of the cell by the NCX (Neef and Maier, 2013).