Testing for QT syndromes is recommended for the major genes (KCNQ1–Potassium Voltage-Gated Channel Subfamily Q Member 1, KCNH2–Potassium Voltage-Gated Channel Subfamily H Member 2, SCN5A–Sodium Voltage-Gated Channel Alpha Subunit 5) in symptomatic patients and their family members when suspecting long-QT syndrome (LQTS) [163]. This evidence concerns the gene KCNQ1 and familial long QT syndrome.