KCNH2 and familial long QT syndrome: In the 70 families we found 64 different mutations; 22 in KCNQ1, 28 in KCNH2, 9 in SCN5A, 3 in KCNE1 and 2 in KCNE2. All patients were heterozygous carriers of a single mutation, except one double heterozygous proband (1.4% of families), who carried p.R583G in KCNQ1 and p.A93T in KCNE1. Twenty-six of the mutations have only been described in Danish LQTS patients (Tables 1, 2, 3), 18 have not been reported previously.