Rare genetic diseases: Long QT Syndrome

By Cristiano Antonino Last updated Dec 18, 2022

Long QT syndrome is a rare genetic disorder that can cause malignant arrhythmias. Treatment is based on the use of beta-blocker drugs

Long QT syndrome is a rare genetic disorder (1 in 2000 individuals in the general population) characterised by a prolongation on the electrocardiogram of an interval called the QT interval (the time in which the heart ‘recharges’ after a contraction) and, therefore, by the possible occurrence of malignant arrhythmias.

Malignant arrhythmias can cause palpitations, syncope and sudden death.

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Long QT syndrome is caused by a genetically based alteration of certain proteins involved in the electrical stability of the heart

To date, a total of seventeen genes have been identified that, when altered, can cause the disease.

The various forms found have a progressive numbering and forms 1, 2 and 3 are the ones discovered first because they are the most frequent.

They are also the most studied.

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Specific events that trigger life-threatening arrhythmias are known for the three main genetic forms of long QT syndrome:

In patients with type 1 disease, the largest genetic subgroup, most cardiac episodes that can cause death occur during sporting activity;

Patients with type 2 disease are particularly sensitive to emotions and sudden noises, such as the ringing of the telephone or the alarm clock.

In addition, females appear to be at higher risk in the postpartum period;

Patients with type 3 have more frequent episodes during rest or sleep.

In all patients with long QT syndrome, the administration of drugs capable of causing further prolongation of the QT interval, which could lead to the initiation of life-threatening arrhythmias, must be avoided.

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Treatment of long QT syndrome is based on therapy with drugs that protect the heart from physical or psychological stress, so-called beta-blockers

In some cases, beta-blockers can be combined with Mexiletine (in type 2 or type 3 forms) and thus prove more effective in preventing the symptoms of the disease.

Sometimes, in some very serious patients, a device such as a pacemaker or cardiac defibrillator is implanted, which help regulate the heartbeat and save lives in the event of cardiac arrest.

Another practice used even before automatic defibrillator implantation is left gangliostelectomy via thoracoscopy (surgery on the nerves that regulate the heartbeat).

Ongoing research will allow the diseased gene to be modified and normalised in the future.

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