Long QT syndrome refers to a category of cardiac arrhythmias involving a prolonged QT interval that can be detected by EKG. Affected individuals may experience fainting episodes and ventricular tachycardia (specifically torsade de pointes), and in some cases, sudden death may occur. Exercise, stress, and loud noises have been implicated as precursers to cardiac events in certain types of Long QT syndrome. Hearing loss is an additional feature in individuals with Jervell and Lange-Nielsen syndrome. Long QT syndrome is usually inherited in an autosomal dominant pattern with reduced penetrance, but the risk of significant episodes may decrease after early adulthood. This panel consists of 18 genes that are associated with this condition.