KCND3 and sudden infant death syndrome: Recently a study reported that R214Q mutation in SCN1Bβ linked to Brugada syndrome and sudden infant death syndrome via a combined loss‐of‐function of Nav1.5 current and gain‐of‐function of Ito current,35 which indicated a similar modulation effect of Navβ1b on Kv4.3 as Navβ1 does.