Long QT Syndrome
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What is LQTS?

Long QT Syndrome or LQT is a sort of heart condition where electrical system of the heart malfunctions, which might lead to conditions resulting in the sudden death of a young person. The LQTS happens when in the cardiac ventricles, prolongation of the repolarization (recovery) after depolarization (excitation) is seen and experienced.

Such a condition may result in abnormal and fast heart beats (called Arrhythmias) this condition is famously called, in medical history as, Torsade de Pointes, when the heart pumps but no blood is pumped out. Such a condition results in the deprivation of oxygen supply to the brain and thus might lead to a sudden fainting or a sudden death due to the ventricular arrhythmias.

Types of LQTS

The Long QT Syndrome is usually classified into two categories – genetic and drug-induced or acquired. Genetic LQTS are a direct result of the genetic mutations in one of the genes. These mutations result in the prolongation of the duration of the ventricular action potential (APD), thereby increasing the length of the QT interval. Drug induced LQTS is usually the result of an anti-arrhythmic drugs like amiodarone etc, while many other drugs (anti-psychotic drugs, such as Haloperidol and Ziprasidone) are also reported to have resulted in this syndrome.

Long QT Syndrome can be further sub-divided based on the gene which has resulted in the condition. Based on this classification, LQTS has ten types – LQT1 (most common type of syndrome found in 40 to 45% cases), LQT2 (second most commonly found, in 30 to 35% cases), LQT3, LQT4, LQT5, LQT6, LQT7, LQT8, LQT9 and LQT10.

Causes of LQTS

As mentioned above, genetic mutations can cause the Long QT syndrome, while the drug-induced cases are also seen. These drug-induced or the acquired LQT cases are more commonly seen and are caused by the disturbances in the blood electrolytes and by some drugs. Some of the drugs affecting and consequently leading to the LQTS are: electrolyte disorders, hypokalemia, hypomagnesemia, hypocalcemia, drug-induced, Antiarrhythmic drugs, Quinidine, Amiodarone, Sotalol, Procainamide, Antihistamines, terfenadine, astemizole, Macrolide antibiotics, Erythromycin, Certain Fluoroquinolone, antibiotics, Major tranquilizers, Tricyclic antidepressants, Gastrointestinal Motility agents, Cisapride, Domperidone.

LQTS Symptoms

The most common and only symptom is when the person faints or passes out suddenly, either while exercising or when experiencing intense emotions like fear, arousal etc. This comes without any warning or sensation. Thus, it is usually seen that in cases where death happens, the person appears normal and fit, showcasing no symptoms of the cardiac arrest.

Who's Affected By LQTS?

One in almost every 7000 people is affected by Long QT syndrome. The disease can start appearing in pre-teen to the teenage years, while newborns and middle aged may also fall prey to LQTS.

LQTS Diagnosed and Treatment

LQT can be easily diagnosed by examining the ECG of the person. Further, the doctors can make use of the diagnostic score testing where each point is given on the basis of specific criteria, which help us determine the probability of the disease.

In treatment, administration of drugs like beta blockers is highly effective in controlling the condition in most of the cases. However, some people might require a pace-maker and an implantable defibrillator.

The treatment can further be divided into two sections – arrhythmia prevention, and arrhythmia termination. In Arrhythmia prevention, the doctors need to use such medicines and surgical methods which root out the cause of the arrhythmias.

Most arrhythmias are cause by the “after depolarisations”, which are in return caused by increased states of adrenergic stimulation. Thus, such steps, which reduce the stimulation of adrenergic elements, should be taken. For example -- administration of beta receptor blocking agents, potassium supplementation, Mexiletine, amputation of the cervical sympathetic chain (left stellectomy) etc.

In case of arrhythmia termination, treatment involves stopping the already acquired LQTS. There is only one way to do this – placement of an implantable Cardioverter-defibrillator (ICD). These are used in combination with beta blocker therapy.

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