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Long QT syndrome (LQTS) is a condition affecting repolarization (relaxing) of the heart after a heartbeat, giving rise to an abnormally lengthy QT interval. [7] It results in an increased risk of an irregular heartbeat which can result in fainting, drowning, seizures, or sudden death. [1]
Most patients with drug-induced QT prolongation are asymptomatic and are diagnosed solely by EKG in association with a history of using medications known to cause QT prolongation. [7] A minority of patients are symptomatic and typically present with one or more signs of arrhythmia, such as lightheadedness, syncope, or palpitations. [7]
Jervell and Lange-Nielsen syndrome causes severe sensorineural hearing loss from birth, affecting both ears. Those affected have a prolonged QT interval on an electrocardiogram and are at risk of abnormal heart rhythms (arrhythmias), which can cause dizziness, blackouts, or seizures. [2]
There’re at least 10 specific gene mutations that are known to be linked to Long QT syndrome, which are referred to as, for example, LQT1, LQT2, and so on, all of which have some effect on one or more ion channels. Aside from congenital causes though, sometimes the QT interval can be prolonged by certain medications which affect ion channels.
Andersen–Tawil syndrome, also called Andersen syndrome and long QT syndrome 7, is a rare genetic disorder affecting several parts of the body. The three predominant features of Andersen–Tawil syndrome include disturbances of the electrical function of the heart characterised by an abnormality seen on an electrocardiogram (a long QT interval) and a tendency to abnormal heart rhythms ...
Romano–Ward syndrome is a descriptive term for a group of subtypes of long QT syndrome, specifically subtypes LQT1-6 and LQT9-16. [8] Several subtypes of Romano–Ward syndrome have been described based on the underlying genetic variant. [5] These subtypes differ in clinical presentation and their response to treatment.
Distribution of QT intervals amongst healthy males and females, and amongst those with congenital long QT syndrome. An abnormally prolonged QT interval could be due to long QT syndrome, whereas an abnormally shortened QT interval could be due to short QT syndrome. The QTc length is associated with variations in the NOS1AP gene. [21]
Common causes for torsades de pointes include drug-induced QT prolongation and less often diarrhea, low serum magnesium, and low serum potassium or congenital long QT syndrome. It can be seen in malnourished individuals and chronic alcoholics , due to a deficiency in potassium and/or magnesium.