KCNK1 and mitral valve disorder: In our own studies, AF and heart failure patients showed unchanged cardiac KCNK1 mRNA levels [10,40], while others reported upregulation of KCNK1 mRNA patients with atrial dilatation [11] or Brugada syndrome [80], downregulation of KCNK1 mRNA in AF [12] or mitral valve disease [81].