page_title: Long QT syndrome
section_title: Inherited
hierarchical_section_title: Long QT syndrome / Causes / Inherited
caption_attribution_description: English: ECGs from a single family showing Romano-Ward and Jervell-Lange-Nielsen forms of Long QT syndrome alongside ECG from an unaffected family member.
context_page_description: Long QT syndrome is a condition in which repolarization of the heart after a heartbeat is affected. It results in an increased risk of an irregular heartbeat which can result in fainting, drowning, seizures, or sudden death. These episodes can be triggered by exercise or stress. Some rare forms of LQTS are associated with other symptoms and signs including deafness and periods of muscle weakness.
  Long QT syndrome may be present at birth or develop later in life. The inherited form may occur by itself or as part of larger genetic disorder. Onset later in life may result from certain medications, low blood potassium, low blood calcium, or heart failure. Medications that are implicated include certain antiarrhythmics, antibiotics, and antipsychotics. LQTS can be diagnosed using an electrocardiogram if a corrected QT interval of greater than 480–500 milliseconds is found, but clinical findings, other EKG features, and genetic testing may confirm the diagnosis with shorter QT intervals.
  Management may include avoiding strenuous exercise, getting sufficient potassium in the diet, the use of beta blockers, or an implantable cardiac defibrillator.
context_section_description: Inherited, or congenital long QT syndrome, is caused by genetic abnormalities.  LQTS can arise from variants in several genes, leading in some cases to quite different features.  The common thread linking these variants is that they affect one or more ion currents leading to prolongation of the ventricular action potential, thus lengthening the QT interval.  Classification systems have been proposed to distinguish between subtypes of the condition based on the clinical features (and named after those who first described the condition) and subdivided by the underlying genetic variant.  The commonest of these, accounting for 99% of cases, is Romano–Ward syndrome (genetically LQT1-6 and LQT9-16), an autosomal dominant form in which the electrical activity of the heart is affected without involving other organs. A less commonly seen form is Jervell and Lange-Nielsen syndrome, an autosomal recessive form of LQTS combining a prolonged QT interval with congenital deafness. Other rare forms include Anderson–Tawil syndrome (LQT7) with features including a prolonged QT interval, periodic paralysis, and abnormalities of the face and skeleton; and Timothy syndrome (LQT8) in which a prolonged QT interval is associated with abnormalities in the structure of the heart and autism spectrum disorder.
caption: Electrocardiograms from a single family showing unaffected family member (top), Romano Ward syndrome (middle) and Jervell and Lange-Nielsen syndrome (bottom).
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