Many studies have been done to shed light on the role of this tetrodotoxin-insensitive sodium channel in disease states. It has been demonstrated that mutated sodium channels in dilated cardiomyopathy may function differently depending upon the specific mutation type of the principal Na+ channel. Specifically, Nguyen et al have demonstrated that these mutations may lead to changes in physiological function such as slower action potential rise time, enhanced late sodium current during steady state, or impaired inactivation. Additional mutations in the SCN5A gene have been linked to shifts in voltage dependence of Na+ channel inactivation in patients with idiopathic ventricular fibrillation. Prior research has suggested that decreased inactivation of late sodium currents may contribute to action potential prolongation. A different SCN5A gene abnormality has been shown to lead to decreased sodium current density and an positive shift in the cell membrane half-maximal activation potential. Therefore, mutations of the Na+ channel can cause altered channel behavior and arrhythmias.