What is 1st degree blockade? What is AV heart block

One of their vital organs is the heart. Its work is based on alternate contraction (compression) and relaxation of the muscle layer of the atria and ventricles. The correct rhythm is ensured by a conduction system with two central nodes: the sinus-atrial (sinoatrial, SA) and the atrioventricular (atrioventricular, AV). Pathological conditions caused by conduction disturbances in the area of ​​the atrioventricular (AV) node are called AV blockades.

The concept of atrioventricular block

Both atria and both ventricles of the heart are forced to contract by an electrical impulse that occurs in the area of ​​the sinus node. Under the influence of the resulting impulse, the atria contract. Next, the impulse is conducted to the atrioventricular node, located at the border of the ventricles and atria. In this area, the conduction of the impulse is delayed for a fraction of a second, allowing blood to pass from the cavities of the atria to the cavities of the ventricles. Then, along the legs of the formation of the conduction system - the bundle of His - the impulse passes into the ventricles already filled with blood, causing them to contract and push blood into the aorta and blood vessels. The mechanism of AV block consists of a time delay or complete inability to conduct an impulse through the atrioventricular node.

How are AV blocks classified?

Atrioventricular blockades are classified according to several criteria. According to development time and duration, there are the following varieties:

• acute, or transient or transient - occurs against the background of myocardial infarction, taking increased doses of cardiac glycosides, as well as various poisonings;
• intermittent, or alternating, or intermittent - occurs against the background of ischemic heart disease (coronary heart disease), accompanied by insufficiency of coronary blood supply;
• chronic – characteristic of various heart lesions.

According to the level (location of the disturbance) of conductivity:

There are 3 degrees of blockade severity: first, second and third. In the case of 1st and 2nd degrees, they speak of incomplete or partial blockade; 3rd degree is a complete AV block with severe disruption of the body. The mechanism of blockades by degrees:

• 1st degree AV block - the occurrence of conduction disturbances at any level with slowing in the AV node, while the conduction of atrial impulses to the muscle fibers of the ventricles is preserved;
• 2nd degree AV block - deterioration of conduction at any level, with blocking of some atrial impulses that do not reach the muscle fibers of the ventricles;
• 3rd degree AV block - complete blocking of the impulse in the area of ​​the AV node, while the conduction of impulses to the muscle fibers of the ventricles stops; the atrial rhythm is determined by the influence of the sinus node, and the contraction of the muscle fibers of the ventricles occurs at its slow rhythm (40 beats per 1 minute or less).

Clinical manifestations of the second degree can be different and are divided into 2 types:

1. Mobits type 1 - each subsequent impulse is conducted in the AV node with increasing delay until it reaches complete blocking. During such a critical delay and complete blockade of the impulse, ventricular contraction does not occur. These moments are called Samoilov-Wenckebach periods.
2. Type Mobits 2 – blocking of impulse conduction occurs suddenly, without a gradual increase in delay. In these cases, the process is characterized by a cyclical nature: every third or every second impulse may not be carried out.

Reasons

Depending on the causes, blockades can be functional (reversible) or organic (irreversible). Functional ones do not lead to changes in the conduction system of the heart. Such conditions are caused by increased processes in the parasympathetic division of the autonomic nervous system. Organic blockades are caused by irreversible changes in the conduction system due to various damaging factors - fibrous or sclerotic changes, the influence of toxic substances, abnormal structure of the heart and other reasons. Cardiac factors contributing to the development of AV block:

• myocarditis;
• impaired blood supply to the heart (spasms or blockage of coronary vessels) with ischemic heart disease and atherosclerosis;
• acute myocardial infarction, especially with spread to the interventricular septum;
• heart defects – congenital or acquired;
• rheumatism;
• post-infarction cardiosclerosis;
• syphilis with the spread of the damaging process to the myocardium;
• tumor formations of the heart;
• formation of calcification and fibrosis of unknown etiology in the conduction system;
• hemochromatosis;
• sarcoidosis

Various substances that, if intoxicated, may cause AV blockade:

• cardiac glycosides (Strophanthin, Digoxin, Korglykon);
• beta-blockers (Bisaprolol, Metoprolol, Propanolol);
• calcium channel blockers (Verapamil, Corinfar, Diltiazem);
• antiarrhythmic drugs (Amiodarone, Cordarone, Quinidine);
• lithium salts (Lithium carbonate, Lithium hydroxybutyrate).

Other causes of AV block:

• surgical interventions;
• hypothyroid syndrome;
• insertion of an intracardiac catheter;
• atopic myotonia.

Symptoms

The main complaints of patients are interruptions in the functioning of the heart (rhythm disturbances), darkening of the eyes, and dizziness. Pre-syncope and fainting, a feeling of fear during the “fading” and “slowing” of the heart, shortness of breath, and severe general weakness may occur.

With 1 degree of AV block, there may be no symptoms; with 2 degrees of Mobits type 1, there may also be no symptoms or the presence of infrequent interruptions in cardiac activity. Mobts type 2 blockade is accompanied by a large number of symptoms that occur in paroxysms. 3rd degree blockade is characterized by severe bradycardia and hemodynamic disturbances. In this case, patients often lose consciousness, falling into a serious condition requiring immediate medical attention. An attack accompanied by severe weakness and bradycardia below 40 beats per minute, cyanosis of the face and upper body, chest pain and loss of consciousness with convulsions is called Morgagni-Adams-Stokes syndrome.

Treatment of atrioventricular blockades

1st degree blockade requires monitoring the dynamics of the condition without any therapy. If the cause of the blockade is taking medications, their dose is adjusted or discontinued. It is possible to replace it with other medications. For cardiac causes of blockades, drug treatment is carried out with beta-adrenergic stimulants (Orciprenaline, Isoprenaline). If the cause of the blockage is a general disease, it should be treated. If an attack of Morgagni-Adams-Stokes occurs, emergency measures are taken: intravenous or subcutaneous administration of atropine, sublingual administration of Izadrina with further hospitalization.

In case of complete blockade, temporary electrical stimulation is performed - the introduction of a temporary intracardiac pacemaker through a venous catheter. Often this procedure precedes radical treatment - the installation of a permanent intracardiac pacemaker, which normalizes the frequency and rhythm of heart contractions, stabilizing the patient’s condition and improving his quality of life. Installation of an pacemaker is indicated for complete blockade, 2nd degree blockade of the Mobits 2 type with frequent attacks, as well as after suffering at least one Morgagni-Adams-Stokes attack.

One of the fairly common ailments of the cardiovascular system is considered to be atrioventricular block, which can vary in severity. In short, this condition is simply called AV block. We will consider the disease of 1st, 2nd and 3rd degrees in more detail, and also discuss its treatment and talk about how prevention is carried out.

About what kind of AV block there is (degree of condition)

AV block is a form of blockade of the conduction of natural electrical impulses through the atrioventricular node, located between the atria and ventricles. There are three degrees of this pathological condition, depending on whether the electrical impulse is conducted slowly, periodically, or completely blocked.

With first-degree AV block, each impulse from the atria reaches the ventricles, but its conduction is delayed literally for a split second - at the moment it passes through the atrioventricular node. This pathological condition does not make itself felt in any way. It occurs in well-trained athletes, as well as in adolescents and young adults who have high vagus nerve activity. In addition, 1st degree AV block can occur against the background of rheumatism, heart damage, sarcoidosis, etc.

2nd degree AV block is manifested by the fact that not every impulse reaches the ventricles from the atria. In this case, a rare and often irregular contraction of the heart is observed. Sometimes such a blockade transforms over time into a 3rd degree blockade.

With 3rd degree AV block, the conduction of natural impulses from the atria to the ventricles completely stops. The heart rate and rhythm of the heart are set by the atrioventricular node or directly by the ventricles. The lack of natural stimulation by the sinus node leads to the fact that ventricular contractions occur very rarely - less than forty times per minute. Thus, 3rd degree AV block is a dangerous arrhythmia that can negatively affect the pumping function of the heart. The patient experiences fainting, dizziness and heart failure. If the ventricles contract more than forty times per minute, the symptoms are less serious, but patients suffer from fatigue, hypotension (during elevation of the body), and shortness of breath.

About how AV block is corrected (treatment)

If a patient has 1st degree AV block, which is not accompanied by negative symptoms, only dynamic observation is indicated. If the disorder is caused by the consumption of medications, for example, cardiac glycosides, drugs against arrhythmia or beta blockers, it is important to adjust their dosage or completely stop them.

Second-degree AV block requires treatment of the disease, and third-degree disease is a reason for serious monitoring and long-term therapy.

If AV blockades are of cardiac origin (developed against the background of a heart attack, myocarditis, cardiosclerosis, etc.), the patient is prescribed therapy with beta-adrenergic stimulants, for example, isoprenaline or orciprenaline. Over time, a pacemaker is implanted.

First aid medications (if necessary to stop Morgagni-Adams-Stokes attacks) are isadrin or atropine. The first is administered sublingually, and the second - subcutaneously. To correct the phenomena of congestive heart failure, diuretics are used, as well as cardiac glycosides (only with caution) or vasodilators. For symptomatic treatment, medications such as teopeca, belloid and corinfar are usually used.

A radical method of treating AV blockade is the installation of a so-called pacemaker. This surgical intervention helps restore normal rhythm and heart rate. The decision about surgical correction is made after consultation with a cardiac surgeon.

How to prevent AV block (prevention)

The main measure for preventing AV block is systematic observation by a cardiologist, especially in old age. Such observation involves, first of all, taking an ECG - an electrocardiogram, as well as monitoring the heart rate in case of any suspicion of any violations. Prevention of AV block also involves maintaining a healthy lifestyle, giving up bad habits, as well as proper nutrition, rich in potassium and magnesium.

The prognosis for patients with AV block depends on the degree of the disorder, as well as the type of underlying disease. The most serious prognosis is typical for patients with 3rd degree AV block. Such patients are disabled and develop heart failure.

At the same time, early implantation of a special pacemaker makes it possible to increase the life expectancy of patients with this diagnosis by an order of magnitude, as well as significantly improve their quality of life. Also, timely implantation helps prevent worsening of the degree of AV block.

P.S. The text uses some forms characteristic of oral speech.

What is AV block? Atrioventricular block: causes, symptoms, diagnosis and treatment

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Atrioventricular (AV) block 1st degree - what is it and how to treat

Atrioventricular block of the 1st degree is a pathological (less often physiological) sign, determined on an electrocardiogram, reflecting a violation of the conduction of a nerve impulse through the conduction system of the heart.

To understand what this condition is and how to treat 1st degree AV block, it is necessary to explain that the heart has a conduction system that has a clear hierarchy. The AV node (Aschoff-Tavara node) is located in the interatrial septum and is responsible for conducting the signal to contract from the atria to the ventricles.

Epidemiology

Grade 1 AV block is a fairly common condition. The incidence increases in direct proportion to age, since over time the risk of developing cardiac pathology (especially coronary artery disease) increases significantly.

There is evidence that AV block of the 1st degree is observed in 5% of people with cardiac disorders. As for children, their incidence varies from 0.6 to 8%.

Classification

By frequency and periodicity of development:

• persistent - is identified and persists in the future;
• transient (transitory) - was discovered once, but subsequently disappeared;
• intermittent - after detection it went away, but then showed up again.

Based on the location of the block, AV blockade is divided into:

• proximal (violation in the part of the node closest to the atria);
• distal (the part close to the ventricles is affected);
• There are combined blockades.

By prognostic value

• Relatively favorable: proximal AV block of degree 1 of a functional nature;
• Favorable: complete blockades of the acute type, with QRS widening (distal block).

Causes of AV block

The causes of the disease can be divided into organic and functional.

There are also a number of syndromes in which isolated degeneration of the AV node and His bundle is noted.

1) In the first case, partial anatomical (structural) damage to the conduction system is observed. This is observed, for example, when the node is involved in fibrosis after myocardial damage, with myocarditis, coronary heart disease, and Lyme disease. Congenital ab blockade is rare (children of mothers with CTD suffer). The AV node is often involved in inferior myocardial infarctions.

2) With a functional blockade, the morphology of the node is not impaired, only the function suffers, which, of course, is better amenable to correction.

This condition occurs when the tone of the parasympathetic nervous system predominates, antiarrhythmics are taken (beta-blockers - bisoprolol, atenolol; calcium channel blockers - verapamil, diltiazem; glycosides - corglikon, strophanthin), electrolyte disturbances (hyper-/hypokalemia).

It is also worth saying that 1st degree AV block can also normally occur, and no treatment is required. This happens, for example, among professional athletes and young people.

3) Degenerative changes in the AV node due to genetic pathology.

They develop due to mutations in the gene encoding the synthesis of sodium channel proteins in cardiomyocytes.

The following syndromes are specific: Leva, Lenegra, idiopathic calcification of the node.

Manifestations

What is heart block? In this case, the diagnostic ECG criterion for this condition is a prolongation of the PQ interval by more than 0.2 seconds, while the P waves are normal and the QRS complexes do not fall out.

Clinically, this condition does not manifest itself in any way, since the heart contracts correctly, although less frequently than normal.

Therefore, this finding on the ECG does not indicate the need for treatment; rather, monitoring of the condition is necessary.

Symptoms may appear when triggered - physical. load. If syncope attacks (fainting) or dizziness occur, one should suspect that the blockade has moved to the second degree (the next stage).

Patient monitoring program

In order to notice the progression of incomplete blockade in time and begin its correction in time, the following is shown:

• repeated ECG studies (frequency determined by the doctor);
• daily (Holter) ECG monitoring.

Of course, an ECG provides comprehensive information regarding rhythm disturbances, which is 1st degree AV block. But in order to identify the causes, additional studies, for example, echocardiography, will be useful. Determining the concentration of medications taken in the blood and studying the ionic composition of the blood may be diagnostically important.

1st degree AV block does not require drug treatment. Dynamic monitoring of the condition of such people is shown. However, if the cause is identified and can be eliminated, this must be done.

If pathology develops as a result of taking medications, reduce the dose or discontinue the medication and select another one; in the case of electrolyte disturbances, correct the electrolyte balance. To summarize, we can say that functional AV block of the 1st degree can and should be influenced; in the case of organic damage to the node, a wait-and-see approach should be chosen.

With a proven functional type blockade, the tone of the autonomic innervation can be carefully adjusted. Drugs such as Belloid and Teopek are used.

Features in children

Disturbances in the conduction of impulses through the heart are quite common in children. This is due to the pathology of pregnancy resulting from maternal diseases (diabetes mellitus, SLE), exposure to environmental factors, etc.

Heart rate is measured differently in infants than in adults: heart rate is 100 beats/min. is already considered bradycardia and requires attention. Therefore, first-degree AV block is noticeable at birth.

The following symptoms are noted: pallor or cyanosis, lethargy, weakness, breast refusal, increased sweating. At the same time, there may be no clinical manifestations in grade 1.

In case of functional disorders, it is favorable; in case of organic disorders, a progressive course of the pathology is likely. Distal atrioventricular blocks are much more dangerous in terms of the risk of complications than proximal ones.

Prevention

There are no specific measures to prevent first-degree AV block.

As a measure of secondary prevention (prevention of progression), we can highlight monitoring of the condition and implantation of a pacemaker (if it worsens).

Heart block: complete and partial, various localizations - causes, signs, treatment

Disturbances in the passage of the impulse between the sinoatrial node and the beginning of the branching of the His bundle, which is called heart block, cause disruption of the heart rhythm and decreased blood supply to the brain.

Heart block, in which the passage of the excitation impulse slows down, is considered partial. If the impulse ceases to be transmitted completely, then complete heart block is formed.

When a partial blockade occurs, most patients feel quite healthy, attributing a slight malaise to fatigue after a hard day at work, stress, etc., since they do not feel significant disturbances in cardiac activity. In many cases, it is detected on an ECG during the next preventive examination or when seeking medical help. At the same time, the word “blockade” causes panic among many. So what kind of disease is this, and what danger does it pose to humans? Let's try to explain.

What is heart block?

work of the cardiac conduction system

Let's start with the fact that the normal functioning of the heart is facilitated by electrical impulses generated in the sinoatrial node. From it they are distributed throughout the atria, the contractions of which contribute to the transmission of the impulse further, through the atrioventricular node to the atrioventricular His bundle. From there it is distributed into areas through smaller branches. With a decrease in the automaticity of the sinus node, the passage of the impulse slows down, and the interval between atrioventricular contractions increases (lengthens).

Sometimes the impulse does not travel through the conductor system at all. In this case, there is no contraction of the atria or ventricles. A long pause occurs (atrial asystole), which is called the Wenckebach period. When it occurs, conductivity is restored again, thanks to the ectopic rhythm, which is called the “rescuing” rhythm. And the next atrioventricular interval is already of normal length. Symptoms with incomplete (partial) heart block are almost completely absent, since it does not disrupt the blood supply to the brain. Most often, partial heart block is accompanied by slight dizziness and slight malaise.

Complete heart block is characterized by the occurrence of bradysystole - a sharp decrease in the number of ventricular contractions (up to 30-40), when the number of atrial contractions remains normal. This almost always causes significant circulatory problems. Patients complain of shortness of breath, dizziness, and their vision suddenly becomes dark.

Sometimes a drop in cardiac activity (a sharp decrease in ventricular contractions to 15 per minute) causes cerebral ischemia. In this case, a Morgagni-Adams-Stokes (MAS) attack occurs: epileptiform convulsions develop, and the person loses consciousness for several minutes. Before it occurs, he begins to feel weak, a feeling of intense heat arises in his head, then he suddenly turns pale and loses consciousness. This condition is called instantaneous blockade. It develops when a violation of sinus rhythm turns into ventricular automaticity. Repeated attacks of MAS often cause death.

Video: heart block on ECG

The video shows an intermittent (alternating) blockade of either the right or left bundle branch

Heart blockades - briefly about the types

The following types of blockade are distinguished depending on where the obstacles that arise that cause disruption of the impulse patency are localized.

Sinoatrial blockade

Sinoatrial (SA) block is usually caused by excessive stimulation of the vagus nerve or organic damage to the sinus node. It is characterized by conduction disturbances in the area between the atria and the sinoatrial node, accompanied by loss of complete cardiac contraction, which is detected by auscultation (listening). The nature of the loss is irregular.

Sinoatrial blockades also develop under the influence of glycosides prescribed for the treatment of heart disease, potassium supplements and quinidine. It also occurs in people in excellent health who engage in various sports when their physical activity increases.

Partial (incomplete) blockade, associated with a decrease in the activity of the sinoatrial node, is asymptomatic. No treatment is required for this type of blockade. If there is a significant decrease in the activity of the sinus node caused by increased excitability of the vagus nerve, a course of therapy with atropine administered subcutaneously is carried out, and sympathomimetics can be used.

Intraatrial block

When it occurs, the patency of the excitation is disrupted inside the atria.

Atrioventricular block

The cause of atrioventicular (AV) blockade is the pathology of the passage of the impulse that excites the ventricles simultaneously through all three branches of the His bundle. They are divided according to degrees, which determine the severity of the disease.

1st degree

First degree heart block occurs when there is a delay in the passage of the electrical impulse through the atrioventricular region. It is detected only through an ECG. If cardiac activity is normal, the duration of the interval of impulse passage from the atria to the ventricles (P - Q) is 0.18 s. When a 1st degree blockade develops, the impulse conduction interval (P – Q) increases to 0.3 s and higher.

2nd degree

A 2nd degree block is characterized by a further increase in conduction disturbances in the atrioventricular node. This disorder has three types (Mobitz).

1. An ECG with Mobitz I (first type) shows a gradual increase in the P – Q interval, with the occurrence of Wenckebach periods (ventricular complexes periodically fall out).
2. For Mobitz II (second type), the P–Q interval remains unchanged, but a loss of ventricular contractions is noted.
3. Type three (Mobitz III) 2nd degree AV heart block is accompanied by an increase in the pathology of electrical impulse patency with loss of contractions. The electrocardiogram shows that the ventricular QRS complex contracts more often.

3rd degree

With the 3rd degree of blockade, the transmission of impulses in the atrioventricular node stops completely. And they begin to contract spontaneously, regardless of each other. Myocardial pathologies, drug intoxication and other factors lead to the development of complete blockade.

Intraventricular block

Intraventricular blockades (ventricular) are associated with the formation of pathology of the pathways located below the atrioventricular node: in the His bundle or one or more of its legs. With this type of blockade, the exciting impulse directed to the ventricles is delayed or not transmitted at all.

types of intraventricular blocks

Video: Lesson on Heart Blocks

Etiology

• Basically, the causes of heart block lie in the progression of diseases, such as:
  1. myocarditis of thyrotoxic, diphtheria or autoimmune type;
  2. diffuse connective tissue diseases;
  3. heart defects and tumors;
  4. sarcodia and amyloidosis;
  5. myxedema;
  6. syphilis affecting the heart and myocardial defects caused by rheumatism;
  7. myocardial infarction or cardiosclerosis.
• No less common causes are drug poisoning caused by exceeding the dosage of certain drugs: quinidine (against arrhythmia), Corinfar, verapamil, digitalis and a number of others. Digitalis preparations are especially dangerous for heart blockades of any kind.
• Incomplete blockade often occurs in completely healthy people. Most often it is caused by overexcitation of the vagus nerve, which is caused by increased stress during training or physical work.
• There have been cases of congenital blockade that occurs as a result of pathology of intrauterine development. In this case, newborns are diagnosed with heart defects, etc.
• Blockade can also be caused by certain types of surgical interventions used to eliminate various heart defects and other anomalies.

Blockades of intraventricular localization

The most common is intraventricular heart block. It has several varieties, which are classified based on which branch of the His bundle the pathology arose. The mechanism by which the excitatory impulse is transmitted to the ventricles from the atria includes three branching segments. They are called the legs of His. First there is a branch to the RV (right ventricle). It is called the bundle branch (right). Next comes the left segment (leg), which is directed downward. Being a continuation of the main trunk, it is thicker than the others. Just below the segment branching to the pancreas, the left segment divides into posterior and anterior branches. Along the posterior branch, excitation is transmitted to the septum, and along the anterior branch - directly to the ventricle, located on the left side.

Damage to any branch of the His bundle contributes to the formation of a single-bundle block. If conduction is impaired in two branches, then we are talking about a two-bundle blockade. If the pathology develops in all three legs (complete bundle lesion), this means the occurrence of a complete three-bundle transverse block of the atrioventricular (distal) type.

Based on the location of the conduction pathology, there is a division into right ventricular and left ventricular blockades. If conduction pathology occurs along the anterior or posterior part of the left segment of the His bundle, a blockade of the left ventricle of the heart is formed.

1. Pathology of the conduction of the anterosuperior left leg mainly progresses with the development of diseases leading to thickening of the wall of the left ventricle (its hypertrophy). This may be myocarditis, anomalies of the interatrial septum, aortic heart disease, heart attack, etc. There is a violation of the patency of the excitation along the anterior section of its side wall. It is distributed abnormally, starting from the lower areas and gradually rising upward. That is, the septum between the ventricles is first excited, then the impulse is transmitted to the lower portion of the posterior wall. At the end of the period, along the anastomoses, the excitation reaches the anterior section of the lateral wall. The cardiogram shows that the QRS interval is wider than during the normal passage of the impulse by 0.02 s. The R wave is of greater height, and the S wave is of greater depth. At the same time, abnormal Q waves are formed.
2. When excitation completely ceases to be transmitted through the His bundle (along its left leg), a complete left ventricular block occurs. But along the segment on the right side the impulse passes in a normal rhythm. And only after excitation occurs in the right part of the septum and RV, the impulse is sent to the left ventricle. Conduction disorders of this type are caused by severe heart diseases, which give complications in the form of various defects of the myocardium and impulse-conducting system.
3. When the left ventricular block is incomplete, the passage of the electrical impulse to the branching slows down. It is brought to the LV transseptally, in a retrograde direction (from left to right) along the right branch of the His bundle, starting from the RV.

The development of blockade of the right ventricle in most cases is caused by diseases leading to its overstrain and the formation of wall thickening. Anomalies of this type are often caused by intoxication of the body with medications prescribed to eliminate disturbances in the functioning of the heart (beta blockers, quinidine, etc.). RV block very often develops in people whose hearts are completely healthy. The anomaly in the patency of the impulse in this case lies in the fact that the septum and LV are first excited, and only then the impulse is transmitted to the RV.

From the above, the conclusion follows: the pathology of the passage of the excitation impulse in any of the branches of the His bundle is a partial blockade of one of the ventricles, on the side of which a pathological interruption of the branch occurred. Excitation to the blocked ventricle is transmitted in an abnormal “bypass” way: through the septum and the ventricle corresponding to the normally functioning branch.

Intraventricular blockades can be identified mainly by electrocardiographic examination. The cardiogram shows a deviation of the electrical axis to the left by an angle of up to 90° with a negative value in case of left ventricular block caused by conduction disturbances in the anterior segment. Deviation of the electrical axis to the right by an angle of up to 90° with a positive value indicates a blockade of the left posterior area. The QRS complex remains unchanged. To clarify the diagnosis, Holter monitoring is performed (taking readings for 24 hours or more).

Video: lesson on bundle branch blocks

Why is heart block dangerous?

Complete atrioventricular block is considered the most dangerous, as it has serious consequences, manifested in the following:

1. The occurrence of chronic heart failure, accompanied by fainting and collapse. Over time, it will progress, causing exacerbations of cardiovascular diseases (in particular coronary artery disease), chronic kidney diseases, etc.
2. Against the background of a slow rhythm, ectopic arrhythmias develop, including ventricular tachycardia.
3. A common complication is bradycardia, leading to hypoxia (oxygen starvation) of the brain and attacks of MAS, the frequent occurrence of which in older people is the cause of dementia.
4. Sometimes an attack of MAS causes ventricular fibrillation, leading to sudden death. Therefore, it is important to provide emergency assistance in a timely manner: if necessary, perform a cardiac massage (indirect) or perform forced ventilation.
5. During heart attacks or post-infarction conditions, complete heart block can cause cardiogenic shock.

Diagnosis

When some of the ventricular contractions are lost, their number decreases. This happens both with complete and partial blockade, including functional blockade. To identify the nature of its occurrence, a so-called atropine test is used. The patient is given atropine. An incomplete blockade, the occurrence of which is not associated with pathological changes, then disappears literally after half an hour.

On the electrocardiogram, only the waves are modified, showing that the impulse exciting the contraction passes from the atrium to the ventricle very slowly. With partial second-degree heart block, the cardiogram shows that the impulse passes with a slowdown. The wave of atrial contraction is recorded, but there is no wave indicating ventricular contraction. Partial blockade of the right leg is recorded on the cardiogram by slight changes in the thoracic leads on the right side and the appearance of small notches on the S wave.

Pathology treatment method

Treatment for heart block (antrioventricular) is prescribed depending on the type and cause of its occurrence. For first-degree atrioventricular block, constant clinical monitoring of the patient is sufficient. Drug therapy is carried out if his condition worsens. If the blockade develops against the background of a heart disease (myocarditis or acute myocardial infarction), then the underlying disease is first eliminated. The treatment method for 2nd and 3rd degree blockade is selected taking into account the location of the conduction disorder.

• If the blockade is of the paroxysmal type, then treatment is carried out with sympathomimetic agents (isadrin) or subcutaneous administration of atropine.
• With a distal blockade, drug therapy does not give the desired effect. The only treatment is electrical stimulation of the heart. If the blockade is acute and occurs as a result of myocardial infarction, then temporary electrical stimulation is performed. In case of persistent blockade, electrical stimulation should be carried out continuously.
• In case of sudden complete blockade, if it is not possible to perform electrical stimulation, an Isuprel or Euspiran tablet (or half a tablet) is placed under the patient’s tongue. For intravenous administration, these drugs are diluted in glucose solution (5%).
• Complete heart block that develops against the background of digitalis intoxication is eliminated by withdrawing glycosides. If the blockade, the rhythm of which does not exceed 40 beats per minute, persists even after discontinuation of glycosides, Atropine is administered intravenously. In addition, Unitol injections are given intramuscularly (up to four times a day). If necessary (for medical reasons), temporary electrical stimulation is performed.

Under the influence of drugs on the vagus nerve, there are often cases when complete heart block turns into partial.

Help yourself

In case of incomplete blockade, specific drug treatment is not required. But care must be taken to reduce the likelihood of its transition to more severe forms. And the symptoms that arise, such as dizziness and heaviness in the chest, also cannot be ignored. Therefore, it is recommended to reconsider your lifestyle and diet, and give up bad habits. If you experience discomfort caused by the blockade, do the following:

1. If you feel dizzy and weak, you need to lie down (or sit down). Stop while walking.
2. Do a simple breathing exercise:
   • take a deep breath;
   • While inhaling, hold your breath for a few seconds (the longer the better);
   • Exhale all the air completely.
   • Repeat the exercise until the condition improves.

Complete heart blocks

Let's look at what a complete intraventricular block caused by pathological changes looks like on an ECG. The amount of damage to each branch of the left leg of His is indicated by the deviation of the isoline towards negative or positive values. It is located neutrally (zero position), when excitation is transmitted to the ventricles in a normal rhythm. If the passage of the impulse is disrupted, a widening of the QRS complex is recorded, which in some cases reaches more than 0.18 s.

With a significant increase in depolarization caused by conduction disturbances in the His bundle, early repolarization occurs. On the electrocardiogram this process is recorded as follows:

• The ST segment in the left chest is shifted below the isoline; the T wave takes the shape of a negative equilateral triangle.
• The ST segment in the right parts of the chest is above the isoline, the T wave has a positive value.

When the right ventricular block occurs, the following occurs:

1. A low S wave of greater width is formed;
2. The R wave, on the contrary, is narrow but high;
3. The QRS complex is shaped like the letter M.
4. Secondary repolarization (early) is reflected in the chest leads on the right by an upwardly convex ST segment, which has a slight downward shift. In this case, the T wave is inverted (upside down).

Complete atrioventricular block, which occurs as a result of pathological changes in the myocardium or against the background of an overdose of certain types of drugs, can develop in a distal or proximal type.

• The proximal type of block occurs when the ventricular pacemaker is located in the atrioventricular node. On the ECG, this type of blockade is indicated by a normal (not widened) QRS complex, the frequency of ventricular contractions is quite high (up to 50 per minute).
• In the distal type, the ventricular pacemaker has a lower idioventricular location. It is the bundle of His with all its branches. It is called a third-order automatic center. The electrocardiogram shows that the number of ventricular contractions is reduced, it does not exceed 30 per minute. This is indicated by a widening of the QRS complex of more than 0.12 s and the layering of the P wave on the ventricular QRS complex. It may have a changed shape (if the automatic impulse occurs below the point at which the His bundle begins to branch). The ventricular complex retains an unchanged shape if the initial point of localization of the automatic impulse is located in the bundle itself.

With atrioventricular block, simultaneous contraction of the ventricles and atria occurs. This gives an increased sound of the first tone, which is called “cannon”. It is clearly audible when listening. The symptoms of this type of blockade depend on the degree of circulatory disturbance and the causes that cause it. If the frequency of ventricular contractions is high enough (at least 36 per minute), and there are no concomitant diseases, then patients do not experience discomfort or unpleasant sensations. In some cases, when cerebral blood flow decreases, dizziness occurs, and consciousness begins to periodically become confused.

With an increase in the duration of the interval between ventricular contractions, partial AV blockade can become complete, causing acute circulatory disorders in the brain. It is often accompanied by a slight eclipse of consciousness and heart pain. In more severe cases, MAS attacks occur, accompanied by convulsions, and the person loses consciousness for a short time. Prolonged ventricular arrest can cause instant death due to ventricular fibrillation.

Drug therapy for complete blockade

Therapy for complete blockade of any type is carried out based on etiology and pathogenesis.

1. If the reason lies in the excessive use of medications, their dosage is adjusted, up to complete withdrawal.
2. To eliminate the blockade caused by cardiac genesis, it is necessary to use beta-agonists (orciprenaline, isoprenaline).
3. Relief of MAS attacks is carried out with an isadrin tablet under the tongue, as well as the administration of atropine subcutaneously or intravenously. If stable heart failure occurs, vasodilators and diuretics are prescribed. The use of cardiac glycosides is possible in small dosages with constant monitoring of the patient's condition.
4. The resulting arrhythmia is eliminated by quinidine.
5. To treat blockade that occurs in a chronic form, symptomatic drugs are used: Corinfar, Belloid, Teopec.

Radical methods include implantation of a pacemaker. Indications for its use are:

• low ventricular rate;
• increased period of asystole (more than 3 s);
• occurrence of MAS attacks;
• complete blockade, complicated by persistent heart failure, angina pectoris and other diseases of the cardiovascular system.

Forecast

A favorable prognosis is given only with partial blockades. The development of a complete third-degree block leads to complete disability, especially if it is complicated by heart failure or occurs against the background of myocardial infarction. The implantation of a pacemaker will make it possible to make more favorable prognoses. When used, some patients may experience partial restoration of their ability to work.

Features of heart block localizations

His bundle and its blockade

His bundle block has distinctive features. It may be constant or appear periodically. Sometimes its occurrence is associated with a certain heart rate. But the most important thing is that this type of heart block is not aggravated by severe disease. And although this blockade in itself does not pose a threat to human health, it can serve as a harbinger of more serious heart disease (in particular myocardial infarction). Therefore, it is necessary to periodically undergo a heart examination using an ECG.

A pathological conduction disorder, the location of which becomes the bundle branch, can pose a threat to life. This is explained by the fact that she is a fourth-order pacemaker. It regenerates low-frequency pulses (no more than 30 per minute). It should be noted that the highest frequency impulse (up to 80 per minute) is formed in the sinoatrial node. The next atrioventricular node of the second order produces impulses with a decrease in frequency to 50 per minute. The His bundle (third-order pacemaker) generates impulses at a frequency of 40 per minute. Therefore, in the event of obstruction of the excitatory impulse along the pacemakers of all levels, they are automatically formed in the Purkinje fibers. But their frequency decreases to 20 per minute. And this leads to a significant decrease in the blood supply to the brain, causes its hypoxia and leads to pathological irreversible disorders in its work.

Sinoatrial heart block

violation of the generation or conduction of impulses at the level of the sinus node

A distinctive feature of sinoatrial block (SB) is that it can occur simultaneously with other types of heart rhythm disturbances and conduction pathologies. Sinoatrial block is sometimes caused by a weak sinus node. It can be permanent, transient or have a latent form.

In this case, three stages of its manifestation are distinguished.

• At the first stage, the passage of the impulse through the sinoatrial region is delayed. It can only be detected by electrophysiological studies.
• At the second stage, two types of SB should be considered. With the development of the first type, a periodic blocking of one impulse occurs at the exit from the atria. Sometimes several impulses in a row are blocked at once, with Weckenbach periodicity. The R-R interval corresponding to the pause is extended. But its value is less than twice the R-R interval that precedes the pause. Gradually, the intervals that follow a long pause become shorter. It is detected during a standard ECG, on which the pulse frequency is displayed without change.
• The second type is characterized by a sudden disruption of impulse conduction, in which there are no Weckenbach periods. On the cardiogram, the pause is recorded as doubling, tripling, etc. pauses R-R.
• The third stage is a complete disruption of impulse conduction in the atria.

Interatrial block

One of the small rare heart rhythm disorders is interatrial block. Like all other types, it has three stages.

1. The impulse of excitation is delayed.
2. Periodic blocking of the excitatory impulse entering the left atrium.
3. Dissociation of atrial activity or complete conduction disturbance.

The third stage is characterized by the automaticity of the formation of impulses from two sources at once: the sinoatrial and gastroatrial node. This is due to the fact that due to the emerging pathology of the sinus node, the number of impulses formed in it sharply decreases. At the same time, an accelerated formation of the number of impulses in the AV node occurs. This leads to simultaneous contraction of the ventricles and atria, regardless of each other. This type of blockade has another name - “Pre-ventricular dissociation” or dissociation with interference. On the electrocardiogram it is recorded together with normal contractions. When listening, a more sonorous “gun” tone is heard from time to time.

Heart block in childhood

In childhood and adolescence, the same types of blockade are formed as in adults, differing only in the cause of occurrence: acquired (due to a disease) or congenital etiology. Acquired forms in children and adolescents are secondary, and develop as a complication after surgery to eliminate various cardiac pathologies, or against the background of diseases with an inflammatory or infectious etiology.

Congenital blockade can be caused by the following reasons:

• Diffuse damage to the mother's connective tissue.
• The presence of type II diabetes mellitus (insulin-dependent) in the mother. This syndrome is called Legerne disease.
• Not fully formed right leg of the His bundle.
• Anomaly in the development of the interatrial and interventricular septa.
• M.Lev disease

The most dangerous is the third degree of atrioventricular or complete transverse block caused by damage to all three legs of the His bundle. When they occur, the conduction of impulses to the ventricles from the atria is completely absent. It does not always have pronounced symptoms. Its only manifestation is bradycardia.

But as it progresses, there is a gradual stretching of the heart chambers, hemodynamic disturbances with a slowdown in overall blood flow. This leads to a deterioration in the supply of oxygen to the brain and myocardium. As a result of hypoxia, children experience neuropsychic disorders. They remember and assimilate educational material poorly, and lag behind their peers in physical development. The child often experiences dizziness, weakness, and slight fainting. Any stressful situation and increased physical activity can lead to fainting.

In the treatment of complete blockade in children, anti-inflammatory and hormonal drugs, antioxidants, nootropics and vitamin complexes are used. Severe forms, in which drug therapy is ineffective, are recommended to be eliminated by cardiac pacing. Pacemakers are also used in the treatment of congenital forms of heart block accompanied by bradycardia. Emergency assistance for loss of consciousness (attack of MAS) consists of closed (indirect) cardiac massage, administration of atropine or adrenaline. Continuous monitoring of conductivity through an ECG is recommended.

Congenital heart blocks often cause the death of a child in the first year of life. In a newborn they are manifested by the following symptoms:

1. Blueness or cyanosis of the skin, lips;
2. Increased anxiety or, conversely, excessive lethargy;
3. The baby refuses to take the breast;
4. He experiences increased sweating and increased heart rate.

For mild forms, drug treatment is not required. But the child needs constant monitoring by a cardiologist. In some cases, surgical intervention is recommended, which can save the baby’s life.

Hello! I had surgery for tetralogy of Fallot in childhood, and now they have diagnosed 2nd degree AV block, Mobitz 1. Can I play sports? What to do with stabbing pain in the heart area?

Hello! You did not specify what exactly you have besides the blockade, what sports you want to do, what worries you besides the pain in your heart, but in any case, you need to contact a cardiologist for pain; you cannot self-medicate. You need to be very careful with sports, especially if you have a serious arrhythmia. Contact a cardiologist who will explain what you can do and what you should avoid.

Yes, this is possible, but the anesthesiologist must know about all your problems.

Are operations during anesthesia contraindicated if there is a partial block of the His bundle? Will they lead to deterioration?

Hello! If there is incomplete blockade of the bundle branches, then anesthesia is possible, but the anesthesiologist should be aware of all these changes.

Normally, the human heart rate is 60-80 beats per minute. This rhythm sufficiently ensures blood supply to the vessels at the time of heart contraction in order to fully meet the oxygen needs of the internal organs.

The normal conduction of electrical signals is due to the coordinated work of the conducting fibers of the myocardium. Rhythmic electrical impulses are generated in the sinus node, then travel along the atrial fibers to the atrioventricular junction (AV node) and further along the ventricular tissue (see image on the left).

A block to conduction of an impulse can occur at each of the four levels. Therefore, they highlight , intraatrial, atrioventricular And . Intraatrial blockade does not pose a danger to the body; sinoatrial blockade can be a manifestation of sick sinus syndrome and be accompanied by severe bradycardia (rare pulse). Atrioventricular (AV, AV) blockade, in turn, can lead to severe hemodynamic disturbances, if conduction disturbances in the corresponding node of 2 and 3 degrees are detected.

Statistics

According to WHO statistics, the prevalence of AV block based on the results of daily ECG monitoring reaches the following figures:

• In healthy young people, 1st degree blockade is recorded in up to 2% of all subjects,
• In young people with functional or organic pathology of the heart and blood vessels, 1st degree blockade is recorded in 5% of all cases,
• In persons over 60 years of age with underlying heart pathology, 1st, 2nd and 3rd degree AV block occurs in 15% of cases,
• In persons over 70 years of age - in 40% of cases,
• In patients with myocardial infarction, 1st, 2nd or 3rd degree AV block is recorded in more than 13% of cases,
• Iatrogenic (drug) AV block occurs in 3% of all patients,
• Atrioventricular block is the cause of sudden cardiac death in 17% of all cases.

Reasons

1st degree AV block can occur normally in healthy people, if there is no background myocardial damage. In most cases it is transient (transitory). This type of blockade often does not cause clinical manifestations, and therefore is detected during a routine ECG during preventive medical examinations.

Also, grade 1 can be found in patients with hypotensive type, when parasympathetic influences on the heart predominate. However, persistent 1st degree blockade may indicate a more serious heart pathology.

Grades 2 and 3 in the vast majority of cases indicate the presence of organic myocardial damage in the patient. These diseases include the following (according to the frequency of blockade detection):

1. . Due to the fact that during ischemia the myocardium experiences a prolonged, chronic lack of oxygen (hypoxia), the performance of the heart muscle decreases sharply. Microscopic foci of tissue appear that do not contract fully and do not conduct impulses. If such foci are located on the border of the atria and ventricles, then obstacles arise in the path of the impulse, and a blockade develops.
2. . The mechanism for the occurrence of blockade is similar, only the cause of the disruption of impulse conduction is both foci of ischemic tissue and necrotic (dead) myocardial tissue.
3. . The mechanism for the development of blockade is a gross violation of the morphological structure of muscle fibers, since heart defects lead to the formation of cardiomyopathy -
   structural changes in the chambers of the heart.
4. , in particular after the experience. This is the replacement of ordinary cardiac tissue with scar fibers, which cannot conduct impulses at all, as a result of which an obstacle arises for them.
5. , long-term and leading to hypertrophic or obstructive left ventricular disease. The mechanism of blockade development is similar to previous diseases.
6. Diseases of other organs - endocrinological diseases (diabetes mellitus, especially type 1, hypothyroidism - lack of hormones secreted by the thyroid gland in the blood, etc.); stomach ulcer; poisoning and intoxication; fever and infectious diseases; traumatic brain injuries.

Symptoms

Symptoms of 1st degree AV block may be scanty or absent altogether. However, patients often note such signs as increased fatigue, general weakness, a feeling of shortness of breath during physical activity, dizziness and a feeling of interruptions in the heart, pre-syncope with flickering spots before the eyes, ringing in the ears and other harbingers of what is now the person will lose consciousness. This is especially pronounced when walking or running quickly, since a blocked heart is unable to provide adequate blood flow to the brain and muscles.

2nd and 3rd degree AV block is much more pronounced. During a rare heartbeat (less than 50 per minute), the patient may lose consciousness for a short period of time (no more than 2 minutes). This is called (Morgagni-Edens-Stokes) and poses a threat to life, since this type of conduction disorder can lead to complete cardiac arrest A. But usually the patient regains consciousness, bypass and additional conduction pathways “turn on” in the myocardium, and the heart begins to contract at a normal or slightly lower frequency. However, a patient with an attack of MES must be promptly examined by a doctor and hospitalized in the cardiology, arrhythmology or therapeutic department of the hospital, since the issue of the need to install a pacemaker, or artificial pacemaker, will subsequently be decided.

In extremely rare cases, a patient may never regain consciousness after an attack of MES, in which case he should be taken to the hospital as quickly as possible.

Diagnosis of AV block

The algorithm for diagnosing rhythm disturbances in general and AV block consists of the following measures:

If the patient has the above-described complaints, call an ambulance or examine a therapist(cardiologist/arrhythmologist) in a local clinic with an electrocardiogram.

The ECG will immediately show signs such as a decrease in the parameter reflecting ventricular contractions (bradycardia), an increase in the distance on the film between the P waves responsible for atrial contractions and the QRS complexes responsible for ventricular contractions. In case of 2nd degree AV block, Mobitz type 1 and Mobitz type 2 are distinguished, which are manifested on the ECG by periodic loss of ventricular contractions. With grade 3, an extremely rare pulse appears due to a complete transverse block, the atria work in their normal rhythm, and the ventricles in their own (with a frequency of 20-30 per minute or less).

After the patient is hospitalized in the department of therapy, cardiology or arrhythmology, He undergoes instrumental methods of further examination:

• , to clarify the nature of myocardial pathology, if any; the contractility of muscle tissue and the ejection fraction of blood into large vessels are also assessed,
• Blood pressure and ECG during the day with subsequent assessment of the degree of blockade, the frequency of its occurrence and its relationship with physical activity,
• Exercise testing is used in patients with myocardial ischemia and chronic heart failure.

In any case, only a doctor can prescribe an exact examination plan for a patient during an in-person examination.

Treatment of AV block

Patients with 1st degree atrioventricular block do not require treatment if they do not have organic heart pathology or diseases of other organs.

In mild cases, it is usually enough to make lifestyle adjustments - give up fatty fried foods, eat right, spend more time in the fresh air and eliminate bad habits. In the presence of vegetative-vascular dystonia, contrast showers have a beneficial effect on the cardiovascular system.

If the patient notes weakness, fatigue and decreased activity, accompanied by low blood pressure and a rare pulse (at least 55 per minute), he can take courses of tinctures of ginseng, schisandra or eleutherococcus as general strengthening and tonic drugs, but only in consultation with the attending physician.

With 2nd and 3rd degree AV block, especially accompanied by attacks or MES equivalents, the patient requires full treatment.

Thus, treatment of the underlying disease of the heart or other organs comes to the fore. While the underlying cause of the block is being diagnosed and the first steps are being taken to treat the block, the patient is prescribed drugs such as atropine, isadrine, glucagon and prednisolone (subcutaneously, in tablets or intravenously, depending on the drug). In addition, it is possible to prescribe teopek, aminophylline or corinfar (nifedipine, cordaflex) in tablets.

As a rule, after treatment of the underlying disease, conduction through the AV node is restored. However, a formed scar in the area of ​​the node can cause persistent conduction disturbance in this place, and then the effectiveness of conservative therapy becomes questionable. In such cases, it is preferable for the patient to install a device that will stimulate contractions of the atria and ventricles at a physiological frequency, providing the correct rhythmic pulse.

The operation to install an pacemaker can currently be performed free of charge according to quotas obtained from the regional departments of the Ministry of Health.

Are there possible complications of AV block?

Complications from atrioventricular block can indeed develop, and they are quite severe and life-threatening. For example, an attack of MES due to a pronounced rare pulse with complete AV block may lead to sudden cardiac death or arrhythmogenic shock. In addition to acute complications, in patients with long-term AV block the course is aggravated, and also develops due to constantly reduced blood flow through the vessels of the brain.

Prevention of complications includes not only measures initially aimed at the occurrence of severe cardiovascular pathology. Timely consultation with a doctor, complete diagnosis and competent treatment will help to identify the blockade in time and avoid the development of complications.

Disease prognosis

Prognostically 1st degree AV block is more favorable than grades 2 and 3. However, in the case of correctly selected therapy for grades 2 and 3, the risk of complications is reduced, and the quality of life and its duration in patients improves. An installed pacemaker, according to a number of studies, significantly increases patient survival in the first ten years.

First degree AV block quite a few occur. According to WHO, it is observed in 5% of people with cardiac disorders and in 0.6% of children.

The prevalence of the disease increases with age and is associated with the risk of developing coronary artery disease and other heart pathologies.

Characteristic

AV block - pathological (sometimes physiological) sign, detected on the ECG and characterized by a failure of the conduction system. The point is to slow down the conduction of nerve impulses to the ventricles of the heart from the atria.

There are three main degrees of pathology, with the first two the blockade is considered partial, with the third - complete.

Reasons

There is a disruption in the functioning of the atrioventricular node, which transmits electrical impulses through itself. The reason may be a number of violations:

Functional: taking certain drugs to improve heart function (beta blockers, glycosides) for a long time, impaired innervation of the heart, malfunctions of the parasympathetic nervous system;

Organic: inflammatory processes or scar formation in certain areas of the myocardium, necrotic changes, ischemia or impaired blood supply to cardiomyocytes.

Pathology of the first degree can develop in athletes. It is physiological in nature, and the length of the PQ interval is normalized after physical activity.

First degree AV block

The pathology is characterized by a certain sign on the ECG: an increase in the length of the PQ interval, from 200 ms and above. There are no disruptions to the normal heart rhythm.

There are several forms of the first degree of pathology, each of them has distinctive features:

• Nodal. It differs in the only sign - an increase in the length of the PQ interval.
• Atrial. Additionally characterized by deformation of the P wave.
• Distal. An increase in the PQ interval is accompanied by distortion of the QRS complex.

Symptoms and diagnosis

There are transient blockades (which pass quickly) and permanent ones. The first type is difficult to diagnose and requires additional research - Holter monitoring.

Its essence is to connect an ECG machine, which takes readings within 24-48 hours. The technique helps to compare the results of the patient’s subjective sensations with changes in the electrocardiogram, assesses the degree of blockade, the severity of additional symptoms, and compares it with the time of taking medications.

Most often, the first degree of blockade is not accompanied by severe symptoms. Bradycardia may often occur. Some patients experience causeless weakness and severe fatigue.

Therapy

Treatment Most types of AV block consist of taking medications to improve cardiac conduction. Therapy is also carried out aimed at eliminating the cause of the development of pathology. Severe disease requires the installation of an external pacemaker (pacemaker).

First degree does not require specific treatment. Monitoring over time, periodic appointment of electrocardiography and daily Holter monitoring are indicated to monitor the progression of the disorder.

When a blockade develops due to the use of medications (beta blockers, drugs to eliminate arrhythmia), it is necessary to adjust the dose or completely stop taking it.

Features of pathology in children

Found in childhood mostly congenital blockades caused by disorders that occur in the mother during pregnancy (autoimmune diseases, diabetes mellitus). External factors can also influence: poor environment, smoking, etc.

The pulse rate in infants is assessed differently than in adults. Bradycardia is diagnosed when the heart rate is less than 100 beats per minute. This condition requires special attention, so even first-degree AV block in infancy is noticeable.

She is accompanied such signs:

• bluish or pale skin surface;
• breast refusal;
• increased sweating;
• weakness and lethargy.

As in adults, clinical manifestations of this type of pathology do not always appear.

Forecast

With the physiological nature of the changes - the prognosis is favorable. If the cause of conduction failure is pathology, its gradual progression may be observed. With the development of distal blockade (located near the His bundle), the risk of complications is higher.

Prevention includes actions to strengthen the cardiovascular system: cardio training, limiting saturated fats in the diet.

In most cases, the pathology does not pose a serious threat to life, but requires observation.

Heart blocks prevent normal blood flow to organs, causing changes in their function. They can occur in children and adults. Different types of blockades pose varying degrees of danger to the body.

In some cases, patients do not suspect that they have a heart pathology, considering themselves practically healthy.

Their heart block is detected during a medical examination or an ECG when visiting a doctor for another disease. The words “heart block”, discovered by the patient in the ECG report, cause panic fear of complete cardiac arrest. Should they be afraid?

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Description of the pathology

In the heart muscle there are clusters of nerve cells (the so-called nodes), in which nerve impulses arise, which spread along special nerve fibers along the myocardium of the atria and ventricles of the heart and cause their contractions.

One of these nodes (sinoatrial) is located in the atrium. It is here that an electrical impulse arises, which, spreading further into the atrioventricular node, ensures a normal heart rhythm. These nodes are called cardiac pacemakers.

The fibers through which impulses are transmitted from pacemakers to muscle fibers are called the conduction system. From the atrioventricular node to the muscles of the ventricles of the heart, impulses pass through bundles of nerve fibers called the bundle branches (left and right).

A disruption in the propagation of impulses generated in the atrial pacemaker is called heart block. They can be transmitted slowly or their conduction along the nerve fibers completely stops - partial or complete heart block develops accordingly. In any case, such changes cause cardiac arrhythmias.

With a slow pace of impulse passage, a longer than normal pause occurs between the contraction of the atria and ventricles. If the impulse is not carried out at all, then contraction of the atria or ventricles of the heart does not occur (atrial or ventricular asystole).

And only the next signal to contract is effective; contractions then occur at normal intervals until the next blockade.

Impairment of the conductivity of the electrical impulse can occur at different levels, which causes various forms of blockades. In this case, blood circulation is disrupted: in the absence of contraction of the ventricles, blood is not pushed into the blood vessels, pressure drops, and organ tissues are not provided with oxygen.

1st degree heart block and its consequences

Atrioventricular heart block (AV block) is the impaired passage of nerve impulses through the fibers of the conduction system between the atria and ventricles of the heart, which causes a serious malfunction of the cardiovascular system.

The danger and significance of AV blockade depend on its severity. There are 3 degrees of blockade severity:

1st degree	1st degree AVB heart block is usually detected during examination. It can be regarded in some cases both as a physiological condition (in young people, in well-trained athletes) and as a pathology (in the presence of other abnormalities and heart problems). may arise for various reasons. The most common of them: increased tone of the vagus nerve (occurs in athletes); sclerotic changes in the conduction system; pathological changes in heart valves; inflammation of the heart muscle (myocarditis); rheumatism; side effect of certain medications (cardiac glycosides, beta blockers, etc.); cardiosclerosis; myocardial infarction; intoxication; borreliosis (Lyme disease); changes in the electrolyte composition of the blood. Medications that can cause disturbances in the conduction of impulses in the heart include: Strophanthin; Korglukon, Digoxin; Nifedipine; Amlodipine; Cinnarizine; Verapamil; Atenolol; Bisoprolol and others. In the absence of any pathological changes in the cardiovascular system, 1st degree AV block does not manifest itself clinically; the person feels practically healthy. Conduction disturbances are detected by ECG and can be considered a variant of the norm. But such persons should be under the supervision of a cardiologist (with regular ECG monitoring), as the process may worsen. The appearance of fainting, dizziness and darkening of the eyes is a clinical manifestation of the transition of 1st degree AV blockade to a more severe degree.
2nd degree	There are 2 types: In the first type (called Mobitz 1), patients attribute fatigue and malaise to workload or stress, but dizziness and fainting may occur. In the second type (Mobitz 2), in addition to these manifestations, there is pain in the heart, cardiac arrest is felt, prolonged fainting, and clouding of consciousness occurs.
3rd degree	The 3rd degree of blockade, in which the impulse to the ventricles is not transmitted at all, is manifested by a decrease in pulse rate (less than 40 beats/min), severe weakness, severe dizziness, shortness of breath, and darkening of the eyes. If the number of ventricular contractions decreases to 15 per minute, the blood supply to the brain suffers, which is manifested by a feeling of heat in the head, severe pallor and loss of consciousness, and convulsive syndrome. Such manifestations are called instantaneous blockade. With the 3rd degree of blockade, the heart can completely stop working and death can occur.

Children and teenagers may also experience the same types of heart blocks that adults experience. The difference is that AV block in children can be not only acquired, but also congenital. Acquired blockade develops against the background of infections, heart disease or after surgical elimination of heart pathology.

Causes of congenital forms of blockade in children:

• maternal diseases (diabetes mellitus, systemic lupus erythematosus);
• widespread damage to connective tissue in the mother’s body;
• abnormalities in the development of the septa between the atria or ventricles;
• underdevelopment of the conduction system in the heart.

Congenital heart block quite often causes the death of a baby in the first year of life. Clinical manifestations in newborns are:

• cyanosis of the lips, nasolabial triangle, fingertips or skin of the body;
• severe restlessness or lethargy of the child;
• breast refusal;
• increased heart rate;
• increased sweating.

In cases of acquired disease, more severe conduction disturbances develop, including complete heart block. But even the most dangerous 3rd degree AV block is not always clinically manifested by severe symptoms. Some children have only one symptom - a decrease in the number of heartbeats.

As the process progresses, the cavities of the heart gradually expand, the overall blood flow slows down, and oxygen starvation of the brain substance develops. Hypoxia is manifested by memory deterioration and decreased academic performance.

The child is lagging behind in physical development, he often complains of dizziness and gets tired quickly. Increased physical activity or stress can lead to fainting.

Diagnostics

Atrioventricular block is diagnosed using an ECG: the interval between the P wave and the QRS complex increases, although the waves themselves are normal. will be even in the absence of any complaints from patients.

If 1st degree AV block is detected at a young age, in a well-trained person, then further in-depth examination may not be carried out.

But short-term recording of an ECG at rest does not always capture single, rarely occurring blockades. If there are complaints or any objective data on the heart, the doctor prescribes daily Holter monitoring. The monitor's sensors are attached to the chest. The examined patient leads a normal, habitual lifestyle.

The device continuously records ECG throughout the day, which is then analyzed. This absolutely painless, non-invasive diagnostic method allows you to determine the frequency of blockades, their dependence on the time of day and the patient’s physical activity. The study helps, if necessary, choose the right treatment.

Echocardiography (ultrasound of the heart) may also be prescribed. This study makes it possible to examine the septum, walls and cavities of the heart, and identify pathological changes in them as a possible cause of blockages. Their root cause may be a change in the valves.

Treatment

Atrioventricular block of the 1st degree (and sometimes 2nd) does not always require treatment. Only when cardiac pathology is detected is individually selected therapy carried out, which can also affect the frequency of blockades.

1st degree heart block in a child does not require drug treatment. Such children need constant monitoring by a pediatric cardiologist with regular ECG monitoring.

If there is a complete blockade, children are prescribed anti-inflammatory drugs, nootropics, drugs with antioxidant effects, and vitamins. If the child loses consciousness, emergency assistance should be provided to the child in the form of a closed heart massage. Congenital blockades and severe forms of acquired heart block are eliminated using an implanted pacemaker.

When the 1st degree of AV blockade passes into the 2nd degree according to the 2nd type (Moritz 2), into a partial (or complete) blockade of the 3rd degree, treatment is mandatory, since such severe conduction disturbances can cause sudden death from cardiac arrest.

The main method of restoring normal heart function is to implant a permanent or temporary pacemaker (PAC) into the patient. Temporary electrical stimulation is necessary, for example, in acute heart block resulting from myocardial infarction.

In preparation for the installation of an pacemaker, a complete examination of the patient and drug treatment (prescription of Atropine and other drugs) are carried out. It will not relieve the patient of the disease; it is used during the period of preparation for pacemaker implantation.

Installation of pacemaker is a surgical treatment method. It can be performed under local or general anesthesia. Its essence lies in the fact that the cardiac surgeon inserts special electrodes into the heart through the vessels (starting from the subclavian vein) and fixes them. And the device itself is sewn under the skin.

The impulse generated by the device causes normal contractions of the atria and ventricles at normal intervals. Rhythmic heart function and adequate blood supply to organs are restored. Stopping blood flow and sudden fluctuations in pressure disappear.

Clinical symptoms (dizziness and loss of consciousness) disappear, which significantly reduces the risk of cardiac arrest and sudden death.

After the operation, the patient is discharged on days 2-7 (after the studies have been performed). When applying a cosmetic suture, there is no need to remove it; it gradually dissolves. Upon discharge, the heart surgeon will recommend how long you should avoid physical activity.

A follow-up examination by a cardiologist is required after 1 month. A doctor's consultation is then recommended 6 and 12 months after surgery and annually thereafter. On an individual basis, the doctor will allow (in the absence of contraindications) sports activities after a few months.

The average period of use of the pacemaker is 7-10 years. In children it is smaller, which is associated with the child’s growth. The device is programmed (heart parameters are set) individually for each patient.

Monitoring the operation of the device must be carried out regularly and on time. If necessary, the doctor adjusts the program: if heartbeats are accelerated or slowed down, the patient’s lifestyle has changed. If the pacemaker ceases to ensure normal heart function, it must be replaced.