KCNQ1 and Sinus bradycardia: 1991; Lupoglazoff et al. 2004). We tried to assess the heart rate in nonsymptomatic, heterozygous, mild, KCNQ1 mutation carriers. As patients with homozygous mutations were having β‐blockers, we evaluated the family members having a heterozygous mutation in the KCNQ1 gene. In total, we have analyzed the heart rate in 16 heterozygous KCNQ1 mutation carriers; sinus bradycardia (≤60 beats/min) was observed in 50% of the heterozygous carriers (n = 8), matching against age‐specific control values. This has been shown in Table 2.