In the ventricular myocardium, which expresses Cx43 but not Cx40, conduction velocity is unaffected by Cx40-deficiency and the inducibility of ventricular arrhythmias under normal conditions was not increased (Verheule et al., 1999; Bevilacqua et al., 2000; Tamaddon et al., 2000), although one study reported an increased inducibility of ventricular tachycardia (VT) in Cx40−/− mice during infusion of isoproterenol (Bevilacqua et al., 2000), possibly involving the Purkinje system. This evidence concerns the gene GJA5 and Ventricular arrhythmia.