Diagnosis of RWS is established by prolongation of the QTc interval in the absence of specific conditions known to lengthen it (for example, QT-prolonging drugs) and/or molecular genetic testing of the genes known to be associated with RWS, of which KCNQ1 (locus name LQT1), KCNH2 (locus name LQT2) and SCN5A (locus name LQT3) are the most common. Other, less frequently involved genes are KCNE1 (locus name LQT5), KCNE2 (locus name LQT6), CAV3 (locus name LQT9), SCN4B (locus name LQT10), AKAP9 (locus name LQT11), SNTA1 (locus name LQT12) and KCNJ5 (locus name LQT13).