SCN5A and familial long QT syndrome: Even when specifically evaluating targeted deletions for well-established genes known to lead to LQTS (LQT1: KCNQ1; LQT2: KCNH2; and LQT3: SCN5A) in humans or genes underlying major repolarizing currents in mouse heart, there are several examples of either failure to find an effect, inconsistent results across studies or differences between in vivo and ex vivo/cellular electrophysiological measurements (Salama and London 2007).