Cardiac arrhythmias: long QT cardiac syndrome

By Cristiano Antonino Last updated Jun 17, 2023

Long QT syndrome is a cardiac pathology, attributable to the family of heart arrhythmias

When the patient has a long QT, it means that his normal ventricular contraction is impaired and he lengthens.

Since the pathology is rather rare, it is still today the subject of careful medical research that can establish in an increasingly precise way all the existing causes and risk factors.

It is generated by an anomaly of the sinus node, that area of the myocardial muscle proposed for the genesis of cardiac electrical signals.

Between one contraction and another (repolarization phase), the heart muscle always needs to relax to be ready for the next stroke (depolarization phase).

The relaxation usually occurs within a few nanoseconds but, in patients with long QT, it can last longer, leading to an effective change in the normal heart rhythm.

Although rare, long QT syndrome affects about 1 in 2000 people today, preferring female subjects to male ones

If acquired, the age of onset is usually variable, but it has been noted that most symptomatic patients complain of the first symptoms already around the age of 40.

In the case of hereditary long QT, the symptoms can instead appear already in the first days after birth or in any case at a young age.

Notifying the doctor promptly in the event of even unexplained episodes of typical symptoms is essential.

In addition to syncope, long QT is among the leading causes of sudden cardiac arrest death.

Brief outline of the anatomy of the heart

The heart is an involuntary muscle. This means that, of its normal activity, it does not need voluntary stimulation to beat.

Divided into four cavities, in the upper part it has two atria, which collect venous blood from the organs and lungs.

In the lower part it houses two ventricles, from which the oxygenated blood is pumped towards all the organs of the body, for their correct functioning.

The heart is formed by a particular muscular wall called myocardium, which conducts the nerve impulses capable of marking the phases of contraction and relaxation of the heart muscle.

In the right atrium there is the sinus node, a small cellular aggregate capable of generating rhythmic impulses (and, therefore, the heart rate).

Together with other secondary nodes, it forms the electrical conduction system of the heart, i.e. the set of all those small cellular and nervous complexes that maintain coordinated cardiac contractile activity.

In long QT syndrome, the harmonic alternation of muscle contraction and relaxation phases is lost.

At that point, the normal heart rate changes.

Maintaining good heart activity is essential, otherwise the individual could incur not only in more serious cardiac problems, but also in other systemic pathologies of the organism, up to death.

Long QT syndrome is a very subtle disease

In the initial stages it can be totally asymptomatic or with non-specific disturbances attributable to simple generalized malaise.

However, there are some manifestations that it is good to keep an eye on, and in the presence of which it is very important to notify your doctor.

Typical symptoms of long QT are:

Palpitations and tachycardia. They indicate that there is some problem at the heart rate level, which must therefore be checked. In general, suffering from arrhythmias can be a problem: where they are sudden and transient they can lead to syncope but, if prolonged, they can cause cardiac arrest.
Frequent and sudden fainting. The individual loses consciousness for no valid reason (for example due to panic attacks), becomes pale and cyanotic.
Episodes of epileptic seizures.

It should be remembered that prevention, in addition to timely intervention, is essential to avoid serious cardiac complications or even cardiac insufficiency and arrest.

Causes

Recent studies have shown that the long QT syndrome can be hereditary and congenital or acquired over time, consequently dividing the triggering causes into two different macro-groups.

The hereditary long QT is the most common, and is caused by the incorrect functioning of some genes in the body’s DNA.

These genes are involved in the production of some myocardial ion channels, which, if altered, unbalance the correct supply of some vital substances essential for good health and cardiac functioning.

These are sodium, calcium and potassium, which are very active in determining the diastole and systole rhythms of the heart.

Hereditary long QT can also be aggravated by the presence of two congenital disorders: Romano Ward syndrome and Jervell-Nielsen syndrome.

The acquired long QT instead develops during the life of the person, as a result of internal imbalances of the electrolyte type, i.e. generated by an altered supply of some substances, or as a result of the repeated use of some drugs (antibiotics, antidepressants, antipsychotics, antihistamines , diuretics, drugs for the treatment of arrhythmias, for hypercholesterolemia, antidiabetics).

Some risk factors may affect the onset of acquired long QT

These are the most common:

Having close family members with the same problem increases the risk of being affected.
Some diseases, which act by creating internal imbalances, can increase the risk of long QT onset. In particular, hypothyroidism, HIV infection, anorexia nervosa and congenital deafness.
Long QT can appear as a response of the heart following myocarditis, myocardial infarction and the implementation of resuscitation maneuvers.

Diagnosis

Diagnosing long QT syndrome is often far from simple since, especially in the early stages, the disease presents itself as totally asymptomatic.

It is essential to contact your trusted doctor, and subsequently to a cardiologist specialist, if even just one of the symptoms indicated above is present.

If you are subject to frequent and senseless palpitations and syncope, or if you have someone in the family who already suffers from the same pathology, then you need more attention.

The anamnesis phase always consists of a careful observation of the present symptoms and of the patient’s clinical history.

Subsequently, the cardiologist prescribes an electrocardiogram (ECG), the only diagnostic test to date capable of further investigating the presence of this syndrome.

The ECG allows you to study the rhythm and cardiac electrical impulses, and returns them in the form of a waveform.

In the electrocardiogram, each wave has its precise amplitude and regularity, so that a change in the interval shown on the diagnostic chart undoubtedly corresponds to a change in the duration of the heart beat with its diastole and systole phases.

In subjects with long QT intervals, the duration of these intervals is longer than normal

The proper name of long QT syndrome derives exactly from the name of the sinus waves shown on the ECG (Q wave and T wave, i.e. the time that passes between the moment in which the ventricles contract and their relaxation before the next stroke).

Increasingly, the diagnostic procedure for identifying the long QT syndrome also includes a careful genetic investigation, to identify the genes possibly responsible for the ventricular malfunction.

Unfortunately, the problem remains that a large number of affected patients are unaware of their condition due to the asymptomatic nature of the disease which, if not treated adequately, can begin with sudden cardiac arrest.

Treatments and prevention

The most appropriate treatments for the treatment of long QT are currently classified according to the nature of the pathology: hereditary or acquired.

In fact, the two types require different therapies, precisely because their etiology is also different.

For both, these are interventions aimed at shortening the QT interval and bringing it to levels considered normal and not harmful.

Treatments for hereditary long QT

To resolve the congenital long QT, the cardiologist generally prescribes some categories of beta-blocker drugs.

The most serious situations of hereditary long QT require surgical therapy.

For those suffering from bradycardia and sinus rhythm disruptions, the option is to have a pacemaker implanted.

The implantable cardioverter defibrillator is instead ideal for those who have already had episodes of syncope and cardiac arrest.

The most modern surgical techniques also exploit the excellent results obtained with cardiac sympathetic denervation, i.e. the removal of the nerve endings that modify the heart rhythm.

Treatments for acquired long QT

Since the development of the acquired long QT may depend on the repeated intake of some drugs and substances, its resolution usually lies in the interruption of the drug therapy that causes the arrhythmia.

In asymptomatic patients who do not have ventricular arrhythmias and no history of close family members with long QT, periodic observation alone and the assumption of basic pharmacological therapy is sufficient.

For those at risk, prevention is essential.

Since arrhythmias are most often the result of intense efforts, it is advisable to abstain from high level or contact sports, to prevent the heart from going into hyperfunction or from suffering violent trauma.

It is essential to keep calm in everyday life. Anxiety and stress negatively affect heart health.

In some rare situations, long QT arrhythmia can develop following intense scares such as sudden loud noises.

In general, maintaining a healthy lifestyle, consisting of constant exercise and a rich diet, can help prevent heart disease.

In this regard, it is recommended to take daily adequate levels of potassium, a fundamental ion for cardiac functioning.

The prognosis for long QT is variable, for some people it can remain latent for a long time or for life, while for others it can develop violently and suddenly.

It is good practice for anyone with a family member affected by the disease to also undergo routine examinations and preventive ECG.

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