KCNH2 and familial long QT syndrome: acute inhibition in HEK293-hERG cells and guinea-pig ventricular myocytes incubated with sera from guinea-pigs immunized with a 31–amino acid peptide corresponding to the hERG pore-forming region (E-pore peptide) and cross-reacting with sera from anti-Ro/SSA-positive CTD patients with LQTS