Kanałopatie is a group of rare, genetically determined heart diseases. They are caused by mutations in genes encoding ion channels. A common feature of channelopathy is a propensity for life-threatening ventricular arrhythmias in people with a structurally he althy heart.

Kanałopatieis a group of diseases that should be considered in the differential diagnosis of syncope and unexplained episodes of cardiac arrest - especially in young people who do not have any heart disease in the tests, which could cause ventricular arrhythmias.

It is important that a patient with a suspected ion channel disease is under specialist care as soon as possible. Despite the inability to eliminate the underlying cause of canopathy, it is possible to influence the patient's quality of life and improve his safety. Due to the family presence, it should be remembered to include the diagnosis and observation of the patient's relatives. Prophylactic treatment may be considered in patients who are not yet asymptomatic.

Ion channels are proteins built into the membranes of cells and responsible for the transport of ions. Channels within muscle cells (including the heart muscle) are involved in producing an action potential - a transient change in electrical potential. This phenomenon is called depolarization.

It is followed by a return to the initial state, i.e. repolarization. The final effect of depolarization is to initiate contraction of the muscle fibers.

Abnormalities in the functioning of this complex mechanism, in particular disturbances in the repolarization phase, may result in a tendency to develop dangerous arrhythmias. Below are the characteristics of the most important bands.

Congenital Long QT Syndrome (LQTS)

Congenital long QT syndrome is caused by a mutation in the potassium or sodium ion channel subunit. Its disturbances lead to an extension of the action potential duration, which in turn carries the risk of arrhythmia. So far, 15 types of mutations responsible for this disease have been identified.

A common feature of all teams is the elongation of the so-called QT interval (measured from the beginning of the QRS complex to the end of the T wave) in the ECG recording and the occurrence of cardiogenic syncope - most typically in the course of polymorphic ventricular tachycardia, the so-called torsade depointes.

  • Tachycardia: when the heart beats suddenly

Unfortunately, the disease can cause sudden cardiac death, especially in young people. Sometimes, the canalopathy is accompanied by other characteristic symptoms. This allows us to distinguish clinical syndromes from them, among others:

  • Romano-Ward syndrome - the most common form; is inherited in an autosomal dominant manner
  • Jervell-Lange-Nielsen syndrome - recessive inheritance, coexists with deafness
  • Andersen-Tawil syndrome - there are temporary paresis and dysmorphic features such as: small jaw, hypertelorism (wide spacing of the eyeballs) and finger development disorders

The diagnosis of LQTS is largely based on a medical history and an ECG examination. Patient history has recurrent episodes of ventricular arrhythmias resulting in syncope and other symptoms suggestive of arrhythmia.

Tachycardia attacks in particular types of disease may be triggered by specific situations, e.g. physical exertion, emotions, and even sleep and rest.

In the first type (LQTS1) swimming is a characteristic provoking factor. Due to the heredity of the syndrome, cases of sudden, unexplained death in the patient's family may be very suggestive.

Symptoms of LQTS usually appear in young people - in the first two decades of life.

The confirmation is an electrocardiogram (EKG), which shows a prolonged corrected QT interval. This state should be differentiated from the so-called acquired syndrome of long QT. Its causes are primarily electrolyte disturbances, such as potassium deficiency or magnesium deficiency, and the effects of drugs. As in the congenital syndrome, there is an increased risk of serious arrhythmic events.

In some patients, the length of the QT interval may be within the normal range. In diagnostic tests, provocation tests are also used: exercise tests or an epinephrine test.

Genetic testing plays a very important role in LQTS, confirming the diagnosis and identifying the syndrome in other family members before the first symptoms appear.

Congenital long QT syndrome is a genetically determined disease, so it is not possible to completely remove the cause.

Treatment is based on improving the quality of life by preventing attacks of arrhythmias and preventing sudden cardiac death. The basis is the modification of the lifestyle consisting in the elimination of triggers such as overexertion, loud sounds or emotional stress.

It is also important to avoid drugs that prolong QT and to maintain the concentration of electrolytes (mainly potassium) at an appropriate level. Chronic use of beta-blockers (nadolo and propranolol are preferred) play a major role in pharmacological treatment. The antiarrhythmic mexiletine, which may shorten the QT interval, also plays an auxiliary role.

Invasive treatment is of great importance. In people with congenital long QT syndrome, implantation of a cardioverter-defibrillator (ICD) may be considered. The device is designed to detect and terminate ventricular arrhythmias with an electrical impulse.

The primary indication for an ICD implantation is an arriving episode of cardiac arrest. They should also be considered in the case of recurrent episodes of arrhythmias and failure of antiarrhythmic therapy.

If pharmacotherapy is ineffective and the ICD is contraindicated or its discharges are too frequent, the alternative is left sympathetic cardiac denervation (LCSD) by removing the 4 sympathetic thoracic ganglia. Denervation contributes to shortening the QT and reducing the risk of arrhythmia attacks.

Congenital short QT syndrome (SQTS)

Unlike long QT syndrome, this type of channelopathy is extremely rare. So far, less than 300 cases of this disease have been reported worldwide.

Truncated QT syndrome is caused by mutations of genes encoding proteins of calcium and potassium channels. At the moment, 6 mutations have been identified, distinguishing 6 disease subtypes. Inheritance is autosomal dominant.

As with other channelopathies, SQTS predisposes to recurrent ventricular arrhythmias. Rapid tachycardia can develop into ventricular fibrillation and cause sudden cardiac death. Short QT syndrome can also contribute to attacks of supraventricular arrhythmias, such as atrial fibrillation.

Shortening the QT interval on the ECG is the basis of diagnosis. Additional, significant features of the recording are high waves, pointed T waves in leads V1-V3.

Patients who have experienced an episode of cardiac arrest due to SQTS are candidates for the implantation of a cardioverter-defibrillator as part of the so-called secondary prevention.

Antiarrhythmic drugs play an important role in pharmacotherapy as they prolong the QT interval by their mechanism of action. These include quinidine, propafonenone, and sotalol.

Brugada Team

Brugada syndrome is an arrhythmogenic heart disease caused by a mutation in the gene encoding sodium channels. As with previous canopathies, inheritance is autosomal dominant.

The band's name is derived fromfrom the Brugada brothers - Spanish cardiologists who first described him. The incidence is on average 1-30 per 100,000 people. Men get sick about 8 times more often than women. Symptoms of the disease usually appear in younger people (around 20-40 years of age)

In Brugada syndrome, polymorphic ventricular tachycardia is also the main type of arrhythmia. Seizures usually occur at night - this is due to a slower heart rate while you sleep. As with other channelopathies, tachycardia can develop into ventricular fibrillation and lead to cardiac arrest.

The key element of recognition is a very significant image of the so-called rapture. the J point seen in leads above the right ventricle on the ECG. It is worth noting that there are as many as 3 types of notations characteristic of this complex.

Moreover, changes visible in the EKG can change dynamically - they appear and disappear spontaneously. When the result is in doubt, an alternative may be provocation tests with antiarrhythmic drugs - ajmaline or flecainide.

The first rule of treatment is to adhere to the avoidance of triggers of arrhythmias such as alcohol consumption and heavy meals. This also applies to many drugs that can trigger arrhythmias in Brugada syndrome.

For this reason, it is necessary to consult a doctor regarding the appropriateness of taking individual preparations. Drugs that can contribute to arrhythmia can be found at www.brugadadrugs.org

As with other congenital arrhythmic syndromes, some patients may be eligible for an ICD. This is primarily about patients who have had an episode of cardiac arrest. Pharmacotherapy is of very limited importance.

Catecholamine-dependent polymorphic ventricular tachycardia (CPVT)

CVPT is in most cases caused by a mutation in the ryanodine receptor gene and the kalsquestrin protein. The consequence is an excessive release of calcium ions into the cell's interior, which triggers arrhythmias.

Inheritance is autosomal dominant. Through genetic testing, the defective gene can be identified in most patients.

As in other channelopathies, the predominant symptom is recurrent episodes of syncope due to polymorphic or bidirectional ventricular tachycardia in people with a structurally he althy heart.

Arrhythmia attacks are strongly associated with exercise and emotional stress - states in which there is an increased secretion of catecholamines (e.g. adrenaline). In CVPT, symptoms can appear very early - already in the periodchildhood.

It is believed to be responsible for approx. 15% of sudden deaths among young people. On average, in the age of 12-20, over 60% of affected people experienced the first episode of fainting or cardiac arrest.

The main test that confirms the diagnosis is the electrocardiographic exercise test, the purpose of which is to trigger the arrhythmia. A resting ECG is usually normal, although people with CVPT may have a slightly slower heart rate. Supraventricular arrhythmias are also common.

The basic recommendation is to avoid physical exertion. The treatment of choice is the use of beta-blockers. A history of cardiac arrest or recurrent, documented attacks of tachycardia despite treatment are indications for the implantation of a cardioverter-defibrillator. Left-sided heart denervation may also be considered.

Channelopathy also includes diseases such as:

  • congenital littermate
  • episodic ataxia
  • erytromelalgia
  • malignant hyperthermia
  • myasthenia gravis
  • familial hemiplegic migraine
  • type IV mucolipidosis
  • cystic fibrosis
  • alternating hemiplegia
  • neuromyotonia
  • periodic hyperkalemic paralysis
  • periodic hypokalemic paralysis
  • generalized epilepsy with febrile seizures plus
  • congenital hyperinsulinemia

Category:

Cardiology