Mutations in the IQ motif of Nav1.5 (R1897W, E1901Q, S1904L, Q1909R, R1913H, and A1924T) [68,69] result in BrS1, LQT3 or mixed syndromes (an overlap of BrS1/LQT3 [65,70,71], see Figure 3). The gene discussed is SCN5A; the disease is long QT syndrome 3.