Long QT Syndrome - Causes - Mechanism - Symptoms - Treatment.

Long QT syndrome (LQTS) is a heart rhythm disorder that can potentially cause fast,
chaotic heartbeats. These rapid heartbeats may trigger a sudden fainting spell or seizure. In some cases, your heart may beat erratically for so long that it can cause sudden death

Before Studying QT syndrome, one should have a brief idea of Electrocardiogram (ECG).
ECG has 5 waves
P, Q, R, S and T.

Q, R and S waves are treated as a single unit and is called QRS complex.

• P wave is formed by contraction of atria. 
• The QRS complex is formed during the depolarization and contraction of ventricles.
• T Wave is formed by the repolarization phase of ventricular action potential conduction.

In the above figure, you can clearly see

P-R interval, S-T interval, QRS interval and Q-T interval.

QT interval is the time taken by the ventricle to complete one cycle of the action potential (conduction).

In Long QT Syndrome the patient has abnormally longer Q-T interval. That is the conduction of impulse becomes slow down which results in arrhythmias. The longer the Q-T interval slower will be the conduction and lesser will be the ventricular beats. sometimes the patient's heart fails to beat which may result in fainting or death.

Causes: 

You can be born with a genetic mutation that puts you at risk of long QT syndrome. In addition, certain medications and medical conditions may cause long QT syndrome.

Signs and Symptoms:

The most common symptom of long QT syndrome (LQTS) is a sudden loss of consciousness, also known as syncope. The condition may also cause seizures and in some instances, cardiac arrest and sudden death.

The severity of the condition varies greatly. Some people never experience syncope and others may have frequent episodes that could possibly lead to cardiac arrest and sudden death.

It is important to note that symptoms usually occur without warning and are caused by a very fast heart rhythm called torsade de pointes. Syncope may occur during

or just after physical exertion, emotional excitement or sudden auditory arousal, such as from an alarm clock.
Treatment:

It is important to note that with the correct diagnosis and therapy, long QT syndrome (LQTS) is a treatable disorder and most deaths are preventable. Many people with the condition can be treated with medication. A minority of patients will need an implantable cardiac defibrillator.