SCN9A and hydrops fetalis: Our main results are (i) expression of acetylcholine receptor nicotinic subunit ε (CHRNE) shows strong preferential expression in the atria (compared to ventricles), (ii) TRPV4 (TRPV4) is expressed RA preferentially (compared to LA), (iii) Cav2.2 (CACNA1B) and BKCa β-1 subunits (KCNMB1) are expressed LA preferentially (compared to RA), (iv) TREK-1 (KCNK2) and Kir2.1 (KCNJ2) are higher expressed in ventricles compared to atria, (v) Nav1.7 (SCN9A) is lower expressed in HF (compared to donor) and (vi) Kv7.5 (KCNQ5) is lower expressed in AF (compared to SR or CAD).