<unk>  is the most common form of congenital Long QT syndrome (LQTS), a genetic heart condition that affects the electrical properties of heart muscle cells. Those affected are at risk of abnormal heart rhythms which can lead to fainting, seizures, or sudden death.<unk>  can be distinguished clinically from other forms of inherited LQTS as it affects only the electrical properties of the heart, while other forms of LQTS can also affect other parts of the body.<unk>  is caused by abnormal variants in the genes responsible for producing certain proteins used to transport charged particles (ion channels) within the heart. These abnormalities interfere with the electrical signals that heart cells use to coordinate contractions, causing the heart to take longer to recharge in between beats. The condition is usually diagnosed using an electrocardiogram, but other tests sometimes used include Holter monitoring, exercise testing, and genetic testing. It may be treated using medication such as beta-blockers, an implantable cardioverter-defibrillator, or surgery to disrupt the sympathetic nervous system.<unk>  is estimated to affect 1 in every 7,000 people.
Romano–Ward syndrome
Brugada syndrome
Witteveen–Kolk syndrome
Andersen–Tawil syndrome
Townes–Brocks syndrome
Laugier–Hunziker syndrome
Baggio–Yoshinari syndrome
Morgagni Stewart Morel syndrome