Long QT syndrome

Long QT syndrome (LQTS) is a problem in the heart's conducting system, which affects repolarization process of the heart thereby causing fast and chaotic heartbeats. Congenital LQTS is inherited, whereas, in other cases, certain medications, stroke, and neurological disorders may cause LQTS.

LQTS leads to rapid abnormal heart rhythm known as arrhythmia, fainting or loss of consciousness known as syncope, or seizures, or even sudden death.

Signs and symptoms

People with LQTS experience symptoms associated with the prolonged of Q-T interval during exercise such as

  • Fainting for no apparent reason
  • Fainting during or shortly after exercise or emotional excitement

Deafness is a symptom of congenital LQTS. Emotional excitement (such as fright, anger, or pain) is the other symptom.

Causes

Long QT syndrome (LQTS) is caused by two main reasons which include:

Acquired LQTS is caused by many medications which prolong the QT interval. Your sensitivity to these medications may be related to your genetic makeup.

Congenital LQTS is an inherited disorder which is caused by an abnormality in the gene code for the ion channels.

Risk factors

You may be at a higher risk of inherited or acquired LQTS if:

  • you experience unexplained fainting, or unexplained near drownings or other accidents, unexplained seizures, or a history of cardiac arrest
  • your family members experienced unexplained fainting, unexplained near drownings or other accidents, unexplained seizures, or a history of cardiac arrest
  • your first-degree relatives are with known LQTS
  • you are taking medications which cause QT interval prolongation
  • you are deficient in potassium, magnesium or blood calcium levels

Complications

LQTS can cause the heart's rhythm to spin out of control, triggering life-threatening, irregular heart rhythms (arrhythmias) including:

  • Torsades de pointes
  • Ventricular fibrillation

Diagnosis

There are few very common techniques used to diagnose LQTS.

An electrocardiogram (ECG) is the best test to diagnose LQTS. The ECG machine records heart's electrical conductivity in waveforms, in which prolonged Q-T interval can be easily noticed.

A stress test often known as exercise ECG is used to show an abnormal Q-T interval. This abnormal QT interval is normal during the resting ECG.

Few people with LQTS may not have prolonged QT interval almost all the time which is often overlooked by the doctor during the examination. Holter monitoring will provide a continuous reading of the heart rate and rhythm over a 24-hour period or more which helps the doctors to look at the recording to identify any prolonged Q-T interval over a prolonged period.

Treatment

Treatment for those with LQTS may include lifestyle changes, medicines, or surgery.

  • Lifestyle changes can help to manage the condition of LQTS
  • Medicines such as beta-blockers are commonly prescribed for the patients with LQTS. These are effective in managing the symptoms of LQTS but do not cure LQTS.
  • If uncontrolled ventricular fibrillation is caused by LQTS, then an implantable cardioverter defibrillator (ICD) is needed.

Prevention or self- management

Be careful about the medications you take as few of them can prolong the QT interval. These medications include appetite suppressants, decongestants, and common antibiotics.

Habit forming drugs, such as cocaine and amphetamines are harmful to those with LQTS.

Seek immediate medical interventions if you are at a risk of low blood-potassium levels such as in the case of diarrhea or vomiting.

Preventive measures are always helpful especially for those who are asymptomatic for LQTS.