Long QT syndrome



Long QT syndrome is a condition in which the heart takes longer than normal to relax between contractions. It can cause fast, irregular heartbeats, with the risk of fainting or seizure. In some cases, the heart it can beat abnormally for so long that it causes sudden death.

The syndrome can be hereditary in nature and therefore present from birth.

An acquired form is caused, however, by the use of certain drugs, by an imbalance of salts and minerals in the body (electrolyte imbalance) and by some diseases.

The syndrome is treatable: drugs that prevent changes in the heart rhythm may be taken, while in some cases surgery or the implantation of a pacemaker or defibrillator may be required.

A simple electrocardiogram can diagnose the syndrome: the term “long QT” refers to the particular aspect of the electrocardiogram trace.

The syndrome is not common and inherited in about one in 2,000 people.


Many people with long QT syndrome do not have any disorders (symptoms). They may become aware of the disease as a result of an EKG done for another purpose or from a family history related to the disease.

If any disturbances are felt, they include:

  • fainting, the most common ailment.The heart cannot pump blood as it should and the brain is not getting enough oxygen. Within a minute or two, the heart rhythm then returns to normal and the person regains consciousness. Fainting can occur when the person is in a state of excitement, anger, fear, or while exercising. Unlike fainting due to various causes and generally characterized by warning signs, in the case of long QT you can lose consciousness even without any premonition, but simply only for a sudden noise, such as the ringing of the telephone or the sound of an alarm.
  • epileptic crisisa seizure could occur if the heart continues to beat abnormally and the brain does not get enough oxygen
  • unexpected deathSudden death could also occur if the heart does not resume its normal beating and an external defibrillator is not used in time to restore the heart to normal rhythm.

The signs and symptoms (symptoms) of long QT syndrome, inherited or already present at birth, can occur as early as in the fetus, during the first weeks or months of life, or even in old age, or even never present in life. Most people experience their first ailment around the age of 40; the reason is still unclear.

Disorders can often be felt during sleep or upon awakening. It is advisable to seek medical attention if you faint during exercise or in an emotional situation or after using a new drug, especially if you are aware that the drug may prolong the QT interval. A family history of long QT (having first degree family members, such as parents, siblings, or children with the syndrome) should also be reported to the treating physician.


The cause of long QT syndrome is usually genetic, attributable to a defective gene inherited from a parent.At least 17 genes associated with the syndrome have been identified to date. The defective gene affects the proteins that form the channels that allow the passage of ions, such as sodium, calcium and potassium. They regulate the electrical activity of the heart, in other words allow the contraction and relaxation of muscle fibers. A mutation of this gene causes a malfunction of these channels.

Some medications can trigger long QT syndrome in the acquired form. These include: some antibiotics, some antihistamines, some antidepressants and antipsychotics, diuretics, medicines for maintaining normal heart rhythm (antiarrhythmics), some anti nausea. The acquired syndrome tends to particularly affect people already predisposed from birth; this explains why not all individuals taking the above drugs develop long QT.

Risk factors are represented by:

  • having one or more first degree relatives with the inherited form of the syndrome
  • taking one or more drugs that can cause the syndrome
  • altered levels of potassium, magnesium or calcium in the bloodoften associated with anorexia nervosa
  • fainting
  • Seizures


Genetic long QT syndrome often goes undetected (diagnosed) or is mistaken for, for example, epilepsy. However, the syndrome may be the cause of some otherwise unexplained deaths that occur in children and young adults. For example, an unexplained drowning of a young person could be the first indicator of the existence of long QT syndrome within a family unit.

For a correct assessment of long QT, both the medical examination and the history of the state of health over time (anamnesis) are important.

If the doctor suspects the syndrome, he may order some tests including:

  • electrocardiogram (ECG), which reveals the rhythm and electrical activity of the heart by drawing a trace on graph paper. The examination can be done at rest or under exertion, for example on a treadmill or an exercise bike. The person's family may also be required to undergo this test
  • cardiac holter, a device to be worn for one day (24 hours) to record the activity of the heart in all the different phases of the day (work, sleep, sport, etc.)
  • genetic examination, it may be necessary to identify the defective gene causing long QT and to help identify other family members who have inherited the gene. It is effective in detecting 3 out of 4 cases of acquired long QT syndrome


Hereditary long QT therapy involves the administration of drugs, such as beta blockers, which control irregular heartbeats and slow the pulse. In the case of frequent or severe disorders (symptoms), which put the person at risk of having a life-threatening arrhythmia, it may be necessary to insert a pacemaker or an implantable cardiac defibrillator into the body. In some cases this may be necessary. a specific surgery, called sympathectomy.

In the case of long acquired QT caused by taking some drugs, they must be stopped as soon as possible and replaced with others.

Lifestyle changes

In addition to taking medications or any surgery, lifestyle changes can reduce the risk of fainting or cardiac arrest. They include:

  • avoid taking drugs that cause the syndrome
  • drink plenty of fluids in case of ailments causing vomiting or diarrhea
  • lower body temperature in case of fever
  • reduce exposure to loud or sudden noises (such as alarms or alarms)
  • avoid stressful situations
  • avoid contact sports or particularly strenuous physical exercises

If the complaints (symptoms) are mild and infrequent, your doctor may just prescribe you to follow these simple preventative measures or lifestyle changes, without any medication.


For long acquired QT syndrome, you need to be very careful about the medications you take. Some can trigger the syndrome and lead to dangerous heart arrhythmias.

Abusive substances (drugs) such as cocaine and amphetamines put people with long QT syndrome at great risk.

In the case of disorders that cause lowering of potassium levels, especially if accompanied by vomiting or diarrhea, it is advisable to undertake adequate medical therapy as soon as possible. Such disturbances can in fact trigger a long QT episode.

Pregnancy and childbirth are generally not associated with major disorders in women with long QT syndrome. However, close medical supervision during and after pregnancy is strictly recommended.


NHS. Long QT syndrome (English)

Mayo Clinic. Long QT syndrome (English)

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