SVC syndrome: what is it, what is dangerous, symptoms, treatment, prognosis

What is SVC Syndrome?

SVC syndrome (syndrome Wolf–Parkinson's–White or WPW syndrome) Is a rare congenital heart disease characterized by abnormalities in the electrical system of the heart. People with WPW syndrome have an abnormal alternate electrical pathway (accessory pathway) between atrium and ventricle, which leads to irregular heartbeat (arrhythmias) and increased heart rate abbreviations (tachycardia).

The heart of a normal, healthy person has four chambers. The two upper chambers are the atria, the two lower chambers are the ventricles.

In the right atrium of a normal heart, there is a natural pacemaker (sinoatrial node, Kis-Flak node) that initiates and controls the heartbeat. When the Keys-Flack node is triggered, electrical activity travels through the right and left atria, causing them to contract. The impulses travel to the atrioventricular node (AV node, Ashoff-Tavara node), which is the bridge that allows impulses to travel from the atria to the ventricles. The impulse then travels through the walls of the ventricles, causing them to contract. The regular pattern of electrical impulses from the heart causes the heart to fill with blood and contract normally.

The accessory electrical pathway in people with SVC bypasses the normal pathway and causes the ventricles to beat earlier than usual (preliminary excitation) and may allow electrical impulses to be conducted in both directions (i.e., from the atria to the ventricles and from the ventricles to atria).

Signs and symptoms

Symptoms associated with SVC syndrome vary greatly from case to case. Some patients do not have any abnormal heart rhythms or associated symptoms (i.e., asymptomatic disease). Although the disorder is present at birth, symptoms may not appear until adolescence or early childhood.

People with Wolff-Parkinson-White syndrome may have one or more irregular palpitations, especially episodes of abnormally fast heartbeats occurring above the ventricles (supraventricular tachycardia). These episodes often start and end abruptly and can last from a few minutes to several hours. The frequency of episodes varies from case to case. Some people experience episodes every week, others only a few sporadic episodes.

Various symptoms may occur during these episodes, including:

• heart palpitations;
• labored breathing (dyspnea);
• dizziness;
• chest pain;
• decreased exercise tolerance;
• anxiety;
• dizziness.

In some cases, the victims lose consciousness (fainting).

Some people with WPW syndrome may have atrial flutter, in which the atrium beats regularly at an extremely high frequency, or atrial fibrillation, in which there is a rapid irregular twitching of the muscle wall.

In extremely rare cases, sick people may develop ventricular fibrillation, a serious condition in which normal the electrical activity of the heart is disrupted, which leads to inconsistent heartbeats and malfunctions of the main pumping chambers of the heart (ventricles). Although rare in WPW syndrome, ventricular fibrillation can potentially lead to cardiac arrest and sudden death.

Causes and risk factors

Most cases of SVC syndrome occur randomly in the general population for no apparent reason (sporadically) and are not inherited. Some cases of SVC syndrome are inherited and may be inherited as an autosomal dominant trait.

Genetic diseases are determined by two genes, one of which a person receives from the father, and the other from the mother. Dominant genetic disorders occur when only one copy of the abnormal (defective) gene is needed for the disease to occur. An abnormal gene can be inherited from either parent or the result of a new mutation (gene change) in a person with a disease. The risk of passing an abnormal gene from a sick parent to offspring is 50% with each pregnancy, regardless of the sex of the unborn child.

In individuals with isolated WPW syndrome, no specific genetic mutation has been identified, and the exact role of genetics in the development of the syndrome has not been fully understood. However, a rare autosomal dominant disorder known as familial Wolff-Parkinson-White syndrome has been linked to chromosome 7. Scientists have found that mutations in the regulatory subunit gamma-2 of the gene for AMP-activated protein kinase (PRKAG2), located on the long arm (q) of chromosome 7 (7q36) cause this disorder, which includes features of WPW syndrome, progressive blockage of conduction, and overgrowth of part of the heart (hypertrophy hearts).

Some scientists believe that familial SVC syndrome is a violation of glycogen accumulation, a group of disorders in which stored glycogen, usually broken down into glucose to supply the body with energy, accumulates in various organs. SVC syndrome is known to occur as part of other glycogen storage disorders such as Pompe disease or Danone disease.

Approximately 7 to 20% of people with WPW syndrome have a congenital heart defect such as Ebstein's anomaly, a condition in which there is a violation of the tricuspid valve. The tricuspid valve connects the right atrium to the right ventricle.

The symptoms of SVC syndrome are the result of an alternate electrical pathway. A normal heart has one pathway (sinoatrial node) that carries electrical impulses from small chambers of the heart (atria) to large chambers (ventricles). These electrical impulses cause the muscles of the atria and then the ventricles to contract and relax, pumping blood throughout the body. Patients with SVC syndrome have a second pathological conduction pathway called the Kent bundle, which sends additional electrical impulses from the atrial muscles to the ventricular muscles. These additional electrical impulses bypass the normal route and disrupt the normal rhythm of the heartbeat and cause disturbances, usually rapid contractions known as atrial flutter, atrial fibrillation, or paroxysmal supraventricular tachycardia". The exact cause of the alternative pathways is unknown.

Affected populations

WPW syndrome is often a congenital condition, but cannot be detected until adolescence or later. The peak incidence is observed in persons aged 30 to 40 years in otherwise healthy adults. Some reports suggest that WPW is more common in men than in women. The estimated prevalence of the disease is 0.1-3.1 per 1000 people.

Diagnostics

The diagnosis of SVC syndrome is based on careful clinical evaluation, detailed patient history, and various specialized studies. Such research may include:

• electrocardiogram (ECG);
• Holter monitoring;
• electrophysiological research.

An electrocardiogram records electrical impulses from the heart and can reveal abnormal electrical patterns. Holter monitoring is a portable device designed to continuously monitor the electrical activity of the heart. The device is usually worn for 24 hours. During electrophysiological examinations, a thin tube (catheter) is inserted into a blood vessel, which is attached to the heart, where it measures electrical activity. Each of these specialized examinations can detect abnormal heart rhythms associated with WPW syndrome.

Some patients with SVC syndrome may be clinically silent, which means they have no symptoms associated with the disorder, including abnormal results from various heart examinations.

Symptomatic Disorders

Symptoms of the following disorders may be similar to those of SVC syndrome. Comparisons can be useful for differential diagnosis.

Laun-Ganong-Levine syndrome (LGL) - a rare congenital heart disease involving abnormalities in the electrical system of the heart. The ventricles receive some or all of their electrical impulses from an irregular pathway (alternate pathway). People with LGL syndrome experience a variety of irregular heartbeats, including atrial flutter, atrial fibrillation, and paroxysmal atrial arrhythmias. Symptoms associated with these irregular heartbeats include weakness, fatigue, heart palpitations, and nausea. The exact location of the alternative pathway in LGL is not known.

Sick sinus syndrome (SSSU) - rare heart diseasecharacterized by an irregular heartbeat (arrhythmia). Patients experience an excessively slow heartbeat (bradycardia) and palpitations (tachycardia). Additional cardiac arrhythmias may occur, including gradual supraventricular tachycardia, atrial flutter, and atrial fibrillation. Palpitations, weakness, fainting and nausea are common symptoms of this syndrome. Most cases of SSS occur in adults aged 50 and over. SSSU is caused by a malfunction of the natural pacemaker of the heart (Kis-Flak node).

Heart rhythm abnormalities associated with SVC syndrome (eg, atrial flutter, supraventricular tachycardia), can occur as separate primary signs or as secondary to structural heart disease. Such alternative causes of abnormal heart rhythms must be distinguished from SVC syndrome.

Treatment of SVC syndrome

Treatment for Wolff-Parkinson-White syndrome may include surveillance without special intervention (monitoring), the use of various medications, and a surgical procedure known as a catheter (radio frequency) ablation.

Specific therapeutic procedures and interventions can vary depending on many factors, such as:

• type of arrhythmia;
• frequency;
• the type and severity of associated symptoms;
• risk of cardiac arrest;
• the person's age and general health;
• and / or so on. factors.

Decisions regarding the use of specific interventions should be made by physicians and other members of the healthcare team, in careful consultation with the patient, based on:

• the peculiarities of his case;
• careful discussion of potential benefits and risks;
• patient preferences;
• other relevant factors.

Some asymptomatic patients may not need therapy. Regular follow-up visits are necessary to monitor the work of the heart.

A variety of medications are used to control episodes of arrhythmias in some people with WPW. Such drugs are known as antiarrhythmic drugsinclude:

• Adenosine;
• Procainamide;
• Sotalol;
• Flecainide;
• Ibutilide;
• Amiodarone.

Calcium channel blockerssuch as Verapamil can also be used. Some medicines, such as Verapamil, can increase the risk of ventricular fibrillation and must be used with caution.

The cardiotonic and antiarrhythmic drug, Digoxin, is contraindicated in adults with SVC syndrome. However, it is sometimes used prophylactically to treat children with SVC who do not have ventricular flutter.

In some cases, medications may not be enough to combat episodes of abnormal heartbeats, or individuals may not tolerate the medications. In such cases, a surgical procedure is used known as catheter ablation. This procedure can also be used in patients at high risk of cardiac arrest and sudden death, including some asymptomatic patients.

During catheter ablation, a small, thin tube (catheter) is inserted into the heart and guided to the abnormal pathways where high-frequency electrical energy is used to destroy (ablate) tissue that forms abnormal way. This form of therapy has an extremely high success rate and may end the need for drug treatment in many patients.

In the past, open heart surgery has been used to treat patients with SVC syndrome. Because of the success of a less invasive procedure, catheter (radio frequency) ablation, open-heart surgery is rarely performed in patients with this disease.

Forecast

Once WPW is identified and treated appropriately, the prognosis is good.

Asymptomatic patients with only pre-excitation of the ventricles on an ECG usually have a very good prognosis. Many develop symptomatic arrhythmias over time, which can be prevented with prophylactic EPS and radiofrequency catheter ablation. Family history patients sudden cardiac death (SCD) or significant symptoms of tachyarrhythmia or cardiac arrest have a worse prognosis. However, after definitive therapy, including curative ablation, the prognosis is good again.