RYR2 and hydrops fetalis: Overall, this mathematical modeling study suggests that increased IP<sub>3</sub>R2 expression in the context of HF may contribute to pro-arrhythmic Ca<sup>2+</sup> signaling via increased Ca<sup>2+</sup> spark frequency but may also serve a compensatory function by countering changes in Ca<sup>2+</sup> spark morphology that arise due to RyR2 remodeling within CRUs in HF.