KCNN3 and hydrops fetalis: Ventricular KCa2.1 channels may contribute (together with KCa2.2 and KCa2.3) to apamin‐sensitive K+ currents that were described in rodents (Chua et al., 2011; Hsieh et al., 2013; Lee et al., 2013; Ni et al., 2013) and show increased levels in HF models (Hsieh et al., 2013; Lee et al., 2013).