RYR2 and hydrops fetalis: To further evaluate the specific contribution of RyR2 to CD in HF, we used a mouse model with RyR2 phospho-mimetic PKA phosphorylation on Ser2808 causing RyR2 Ca2+ leak (RyR2-p.Ser2808Asp)26,31,53 and compared it to a non-leaky RyR2 mouse model that is protected against RyR2 Ca2+ leak due to the genetic ablation of the RyR2 PKA-phosphorylation site Ser2808 (RyR2-p.Ser2808Ala)26,31,54 (see cardiac function in Supplementary Table 5).