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Torsades occurs as both an inherited (linked to at least 17 genes) [6] and as an acquired form caused most often by drugs and/or electrolyte disorders that cause excessive lengthening of the QT interval. [7] Common causes for torsades de pointes include drug-induced QT prolongation and less often diarrhea, low serum magnesium, and low serum ...
In long QT syndrome it takes longer for this repolarisation to occur, shown in individual cells as a longer action potential while being marked on the surface ECG as a long QT interval. [11] The prolonged action potentials can lead to arrhythmias through several mechanisms. The arrhythmia characteristic of long QT syndrome, torsades de pointes ...
Although QT interval prolongation is one of the most common reasons for drug withdrawal from the market, the overall incidence of drug-induced QT prolongation is difficult to estimate. [13] One study in France estimated that between 5-7% of reports of ventricular tachycardia , ventricular fibrillation , or sudden cardiac death were in fact due ...
Long QT syndrome, or LQTS, is when somebody’s QT interval is longer than normal, which should typically be less than half of a cardiac cycle. In fact, for a heart rate of 60 beats per minute, the QT interval’s generally considered to be abnormally long when it’s greater than 440 milliseconds in males or 460 milliseconds in females.
QT interval dispersion (QTd) is the maximum QT interval minus the minimum QT interval, and is linked with ventricular repolarization. [40] A QTd over 80 ms is considered abnormally prolonged. [ 41 ] Increased QTd is associated with mortality in type 2 diabetes. [ 41 ]
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]
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 principally diagnosed by measuring the QT interval corrected for heart rate (QTc) on a 12-lead electrocardiogram (ECG). Romano–Ward syndrome is associated with a prolonged QTc, although in some genetically proven cases of Romano–Ward syndrome this prolongation can be hidden, known as concealed Long QT syndrome. [13]