For the normal and coordinated functioning of organs and systems, a regular and sufficient supply of blood is necessary, which is ensured through heart contractions. The main function of the heart - contractility - can be disrupted by various disruptions in the conductivity of the myocardium - the heart muscle. One of these disorders is sinoatrial block, details of the causes, symptoms and treatment of which in children and adults are discussed in the article.

What is sinoatrial block and what are its causes?

The sinoatrial node (sinus node) is located in the wall of the right atrium slightly lateral to the mouth of the superior vena cava, midway between its opening and the right atrial appendage. The branches of the sinoatrial node (bundles of Bachmann, Wenckebach, Thorel) go to the myocardium of both atria and the atrioventricular junction. The disruption of the passage of the sinus impulse through the sinoatrial node is called sinoatrial block, or sinoauricular block.

Experts note that sinoatrial block is nothing more than a type of SSS (sick sinus syndrome), when the electrical impulse between the sinoatrial node and the atria is blocked. As a result, transient, temporary atrial asystole develops, which leads to loss of one or more ventricular complexes. Most often, incomplete blockade develops, in which any part of the impulses arising in the sinus node is not transmitted to the atria and ventricles. Less commonly, a loss of 2-3 cycles is observed, as a result of which a long pause is recorded during the examination, 3 times higher than normal intervals.

The disease is rare, affecting approximately 0.16% of people. It is most often diagnosed by ECG in people over 50 years of age, and about 70% of them are male. Sometimes sinoatrial blockade is observed in children, in the vast majority of cases - with congenital or acquired organic heart pathology at an early age.

The causes of blockade in 60% of cases are associated with progressive coronary heart disease, which is associated with damage to the right coronary artery, as well as with myocardial infarction of posterior localization against the background of coronary artery disease. In 20% of people, the pathology was diagnosed in connection with myocarditis of viral and bacterial etiology. Other possible causes of sinoatrial block:

• rheumatism;
• myocardial cardiosclerosis;
• myocardial calcification;
• severe hypertension;
• overdose or side effect from taking drugs - beta blockers, cardiac glycosides, quinidine;
• excess potassium in the blood;
• hypersensitivity of the carotid sinus;
• conducting reflex tests that lead to an increase in the tone of the vagus nerve;
• brain tumors;
• leukemia;
• pathologies of cerebral vessels;
• meningitis and encephalitis;
• congenital cardiomegaly;
• thyroid diseases;
• CHD (valvular defects);
• chest injury.

If the disease occurs in a child from birth, it may be hereditary, which is transmitted in an autosomal dominant manner. Also, sinoatrial blockade often develops a few days after electrical impulse therapy. Up to a third of cases of sinoauricular block remain without an identified cause of development, but if the pathology is fatal, then the autopsy shows fibrosis of the sinoauricular junction and various disorders in other parts of the conduction system of the heart. Thus, the anatomical basis of this disease is always degenerative or inflammatory processes of the sinus node and the tissues surrounding it.

Classification of pathology

Sinoatrial block occurs for various reasons, but they are all classified into the following groups according to the type of disorder:

1. Blocking the conduction of impulses from the sinus node to the atria.
2. Low impulse strength from the sinus node.
3. Complete absence of impulse production in the sinus node.
4. Poor susceptibility of the atrial myocardium to conduct electrical impulses.

Also, sinoatrial blockade is divided into the following degrees:

1. First degree - there is an increase in the conduction time of the impulse from the sinoatrial junction, but still this impulse reaches the atria, albeit with a delay. This disease is not visible on an ECG; it can only be determined using EFA.
2. Second degree - there is a periodic disturbance in the conduction of impulses to the atria, resulting in loss of ventricular complexes, which is determined by ECG. This degree of blockade is divided into two subtypes - sinoatrial blockade 2nd degree, type 1 (conduction disturbances develop gradually with periodically complete sudden disappearance of ventricular complexes) and type 2 (periods of absence of excitation of the heart muscle without a previous increase in sinoatrial conduction time).
3. Third degree, or complete sinoatrial block. The impulse from the sinus node does not reach the atria at all, and asystole continues until the 2nd or 3rd order pacemaker is activated.

Symptoms of manifestation

With sinoatrial blockade of the 1st degree, which is called partial (incomplete), the patient does not show any complaints, so it can only be detected after a thorough examination for other pathologies. Blockades of 2-3 degrees are more serious diseases, but the clinical picture during their development will largely depend on the rhythm frequency, the adaptation of a particular organism to a slower rhythm (bradycardia).

The second degree of sinoatrial blockade causes cerebrovascular accidents. Clinically, this manifests itself in the form of regular dizziness, sometimes leading to fainting, weakness, decreased performance, a feeling of the heart slowing down or the absence of its beating at any moment. Symptoms can develop as extrasystole, if the patient has only single impulses blocked, and also as bradycardia, if every 2nd impulse is blocked.

A more vivid clinical picture is provided by 3rd degree sinoatrial block. When the AV connection takes over the role of pacemaker, the person may not feel the heart rhythm at all. Other possible symptoms of the disease:

• syncope;
• unexpected, causeless failures (fainting);
• frequent dizziness;
• memory impairment;
• signs of heart failure - shortness of breath, suffocation, attacks of cardiac asthma, swelling, enlargement of the liver.

Complications of sinoatrial blockade

Severe bradycardia, which can be caused by complete sinoatrial block when the heart rate is less than 40 beats per minute, leads to frequent and severe attacks of Morgagni-Adams-Stokes. They not only provoke unpleasant symptoms - loss of consciousness, involuntary bowel movements and urination, muscle cramps and breathing problems, but can also cause sudden death, which more often happens with prolonged fainting.

In general, the prognosis even with complete sinoatrial block is considered more favorable than with complete atrioventricular block, since death is much less common. The prognosis will depend on the cause of the pathology, the type of blockade, associated arrhythmias and the overall health of the heart. The worst outcome is for elderly people who suffer from constant partial blockade due to coronary artery disease, since it most often turns into a complete blockade and ends in cardiac arrest.

Diagnostic methods

The main diagnostic method is an ECG, although to identify the first degree of blockade you will need to undergo an electrophysiological study - EFA. ECG signs of different degrees of sinoatrial block are as follows:

1. Second degree blockade of type 1 - the frequency of discharges in the sinus node is constant, there is an extended P-P interval during the pause, and there is a gradual shortening of the intervals before the pause.
2. Blockade of the 2nd degree, type 2 - a pause equal to the P-P interval, doubled or tripled, periodic loss of the PQRST complex is observed.
3. Blockade of the 3rd degree (complete) - absence of PQRST complexes (asystole), registration of the isoline until the next order pacemaker is activated. This manifests itself as the appearance of an ectopic rhythm with the absence of a normal P wave. Atrial fibrillation is often present.

For a more detailed study of heart function and diagnosing sinoatrial blockade, many patients are recommended to have 24-hour ECG monitoring, as well as a transesophageal ECG (the latter is required to detect complete blockade). To clarify the cause of the pathology, an ultrasound of the heart and other examinations are most often performed as indicated. Differential diagnosis is made with sinus arrhythmia, atrial extrasystole, sinus bradycardia.

Treatment methods

When the disease is caused by short-term causes, for example, an overdose of cardiac glycosides, sinoatrial blockade can be completely eliminated. It may go away without treatment once the influence of the risk factor ceases. With the development of sinoatrial blockade against the background of increased tone of the vagus nerve, which often happens in young people, the administration of Atropine, as well as sympathomimetics - Isoprenaline, Orciprenaline, helps. In some cases, drug therapy brings only short-term results, but an unstable improvement in rhythm even in such a situation can be achieved with the help of nitrates (Cardiket, Olicard), anticholinergics (Platifillin), as well as Nifedipine, Bellaspon, Belloid, Nonachlazine. However, all of these medications are not tolerated by many patients and contribute to the development of ectopic arrhythmias, and therefore should be used only with great caution.

Pacemaker implantation is mandatory for those patients who have repeated attacks of syncope (Morgagni-Adams-Stokes attacks), severe symptoms, as well as episodes of clinical death and increasing signs of heart failure. When the causes of the pathology cannot be corrected, then permanent pacemaker is performed (for example, cardiosclerosis, cardiac fibrosis in old age). Myocardial infarction, acute myocarditis, severe drug overdose require temporary cardiac pacing. Only an ECS will solve the problem of complete sinoatrial block, which causes conduction failures, tachyarrhythmias and threatens sudden cardiac arrest. Read about the differential diagnosis of myocarditis

What not to do

With sinoatrial blockade, you should not overload yourself with heavy work, practice competitive sports and static loads, eat with an abundance of salt and animal fats, not get enough sleep, expose yourself to prolonged stress, or lead an unhealthy lifestyle.

Preventive measures

It is not possible to prevent the hereditary form of the disease. Cases of sinoatrial blockade acquired during life can be prevented with early correction and treatment of cardiac diseases and the exclusion of inappropriate medications and their overdoses. You should regularly visit a cardiologist if you have coronary artery disease and lead a healthy lifestyle to prevent myocardial infarction. Monitoring hormonal levels, the state of the thyroid gland, blood vessels, and preventing chest injuries are important tasks for the patient, which can also be classified as measures of nonspecific prevention of sinoatrial blocks.

Are you one of the millions who have heart disease?

Have all your attempts to cure hypertension been unsuccessful?

Have you already thought about radical measures? This is understandable, because a strong heart is an indicator of health and a reason for pride. In addition, this is at least human longevity. And the fact that a person protected from cardiovascular diseases looks younger is an axiom that does not require proof.

The materials presented are general information and cannot replace medical advice.

Sinoatrial (sinoauricular) blockade

Correct myocardial contractions are ensured primarily by the work of the cardiac conduction system.

When the production or transmission of nerve impulses along the fibers of these structures is disrupted, discoordination of cardiac activity develops. One of the types of arrhythmias is sinoatrial (SA) block.

Blockades are a pathological slowdown in the conduction of impulses along the conduction pathways, up to the complete impossibility of transmission to other cells.

Among the main causes of such conditions are organic and functional changes caused by:

• inflammation of the myocardium;
• ischemia of the heart muscle;
• drug intoxication;
• vegetative dystonia;

Sinoatrial block corresponds to a disturbance in the conduction of electrical potential from the sinus node located at the level of the right atrium.

Impulse delay develops against the background of a high concentration of cardiac glycosides, β-blockers, cordarone, and quinidine. SA blockade can be a consequence of an increase in the level of potassium in the blood of patients, vagotonia, thyroid dysfunction, and can also be congenital and inherited.

Types of pathology

Based on their temporary nature, all blockades, including SA, are divided into two types: transient and permanent.

Regarding the severity of SA blockades are classified as follows:

1. incomplete:
2. 1st degree sinoatrial block;
3. SA blockade 2nd degree, first and second type;
4. advanced 2nd degree sinoauricular block;
5. complete sinoatrial block of the 3rd degree.

Manifestations of pathology are directly related to the severity of the delay of the impulse when passing from the main source of excitation to the atrioventricular node.

With minimal changes, all impulses slowly reach the end point. As the situation worsens, some potentials generated in the sinus node die out without reaching the AV connection.

Electrocardiographic signs

Violations of the mildest degree on the ECG do not have strictly individual signs. The cardiograph records the delay in the conduction of potentials through the atria, which is expressed in the prolongation of PQ intervals and PP distances without violating the RR ratios. In other words, the diagnostician will be presented with a picture of sinus bradycardia.

Second degree sinoatrial block is represented by 2 types:

1. complete extinction of one of the potentials with a preceding change in conduction delay (Samoilov-Wenckebach period);
2. unexpected interruption of sinus rhythm due to loss of a normal impulse.

Electrocardiographic signs of these disorders are the absence of timely appearance of the P wave. This manifestation may be preceded by a gradual reduction in the duration of PQ intervals during type 1 2nd degree blockade.

Degree 3 sinoauricular conduction disturbance on the ECG is recorded as a straight line without recording excitation from a normal source of impulses until the function of automatism is taken over by the downstream pacemaker.

Episodes of SA blockade 2 and other degrees can develop at any time of the day. In order to register changes of a temporary nature, a daily cardiogram is recorded (monitoring).

Symptoms

Minimal dysfunction in conduction along the sinoauricular junction can only be determined as a decrease in sinus rhythm (bradycardia); patients do not feel any interruptions in the heart.

SA blockade, starting from the 2nd degree, has clear clinical signs. During episodes, patients experience attacks of dizziness and complain of a feeling of irregular cardiac activity.

With a significant blockade, a fainting state develops due to insufficient blood supply to the brain, called a Morgagni-Adams-Stokes attack. Stopping breathing, involuntary urination and defecation, and convulsive readiness may accompany such fainting.

If, in the third degree of disturbance, the extinct sinus impulse is replaced by a rhythm from the atrioventricular connection, then patients do not notice any significant changes in their condition. Severe cases are characterized by complete asystole with the threat of sudden death.

Differentiated approach to diagnosis

The diagnosis is based on an assessment of the electrocardiogram with the possible inclusion of additional research and functional tests.

Blockade of the sinoatrial junction is differentiated from sinus bradycardia, in which the heart rate exceeds 40 beats per minute, in contrast to an abnormal slow rhythm with a frequency of 30–40 beats per minute.

An atropine test helps to make a final diagnosis. Immediately after administration of the drug, in the event of a blockade, the heart rate increases twofold, followed by a rapid decrease.

The presence of escape rhythms is a reason to clarify the nature of the arrhythmia, since replacement impulses are often similar to extrasystole, a change in the main source of excitation to atrial or atrioventricular.

Therapeutic tactics

First degree sinoatrial block often does not require treatment. In order to monitor the condition of the myocardium and avoid aggravation of the situation, the patient is periodically referred for an ECG and other cardiac studies.

If the patient has a history of taking medications that cause blocking of sinus impulses, it is necessary to reconsider medication prescriptions and switch to an alternative drug without this side effect.

In case of disturbance of sinoatrial conduction against the background of increased tone of the vagus nerve, they resort to the prescription of anticholinergics (atropine, platyphylline) and sympathomimetics (isadrine, ephedrine).

In the absence of a response to drug treatment, the presence of a blockade of degree 2, frequent episodes of Morgagni-Adams-Stokes attacks, and the threat of cardiac arrest are indications for deciding to install a pacemaker.

Forecast

The duration and quality of life of patients depend on the duration and form of conduction disturbance through the sinus node, the condition of the myocardium, and combination with other pathologies.

In general, the prognosis for this type of arrhythmias is better than for AV blockade. Short-term episodes of impulse delays in the sinoauricular region against the background of transient conditions do not aggravate the situation in general.

Constant manifestations of partial blocking of sinoatrial impulses can eventually transform into complete and advanced ones with the development of fainting attacks and the risk of sudden cardiac death.

Sinoatrial (SA) block

Sinoatrial block II degree type I with Wenkenbach periodicity

Second degree SA block of type II (Mobitz block) is characterized by loss of the sinus complex without changes in the P-P intervals (Fig. 48). This type of block occurs in long pauses as a result of sudden blocking of one or more sinus impulses without a preceding periodicity. Despite the absence of changes in the P-P intervals in the conducting complexes, a certain ratio can be established between the total number of sinus impulses and the number of impulses conducted to the atria - 2:1, 3:1, 3:2, 4:3, etc. Sometimes the loss can be sporadic. The extended P-P interval is equal to double or triple the main P-P interval. If the pause is prolonged, replacement complexes and rhythms arise. Regular 2:1 SA block mimics sinus bradycardia. If the cessation of conduction in the SA junction is prolonged to values ​​of 4:1, 5:1 (the pause is a multiple of the duration of 4-5 normal cycles), they speak of advanced SA blockade of the second degree, type II. Frequent occurrence of long pauses is perceived as a sinking heart, accompanied by dizziness and loss of consciousness. The symptoms correspond to the manifestations of SSSU.

Sinoatrial block II degree II type

SA block of the third degree (complete SA block) is recognized using electrophysiological methods. The ECG shows a slow escape rhythm (most often the rhythm of the AV junction). Clinical symptoms may be absent or signs of regional (cerebral) hemodynamic disorders may appear with a rare replacement rhythm. TREATMENT. The occurrence of SA blockade as a result of acute cardiac pathology requires active treatment of the underlying disease. In case of significant hemodynamic disturbances as a result of SA blockade, anticholinergics, sympathomimetics, and temporary cardiac pacing are used. With persistent SA blockade, the question of permanent cardiac pacing is raised.

What is 2nd degree heart block?

If there are disturbances in the functioning of the sinus node, new sources can form in various areas of the heart muscle. They provide electrical impulses.

The new sources presented may have a negative impact on the sinus node, competing with it or aggravating its activity.

There may be a blockage in the propagation of the wave through the heart muscle. All presented negative phenomena can be accompanied by arrhythmias and, in the worst case, blockades, which are called atrioventricular.

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Conducting cardiac system

Speaking about cardiac impulses, it should be noted that they are formed in the formation of the sinus node. It is located in the area of ​​the right atrium and is the main one.

It is the sinus node that guarantees the frequency of rhythmic contractions, which are then transmitted to the atrioventricular node.

The latter is located in the area of ​​the interatrial septum. The fibers that form the bundle of His lag behind it. It is located in the septum between the ventricles, from which both its legs emerge: right and left. The presented endings branch and terminate on the myocardial cells of the ventricles.

Each of the components of the conductive system can independently create excitation, and if the operation of a certain node located above is destabilized, its functioning will replace the underlying one.

However, in such a situation, the degree of impulse frequency suffers, and, as a result, the rhythm, which decreases significantly (from 60 to 20 contractions).

Causes of pathology

2nd degree heart block occurs due to the following factors:

• genetic predisposition and inherited pathologies;
• coronary heart disease and myocardial infarction;
• cardiosclerosis, angina pectoris, myocarditis;
• consuming large dosages of medicinal components or using medications not according to medical recommendations;
• change in the thickness of the heart muscle.

The heart rate of an adult in normal health is 60 to 80 repetitions per 60 seconds. If no heart contractions are observed within 3-5 seconds, then the person is likely to lose consciousness. He may also begin to have convulsive contractions, and in the absence of specialist help, death occurs.

The presented pathological phenomena are formed sometimes or can be observed constantly. Atrioventricular block is identified using an ECG.

Differences between 2nd degree heart block

With 2 degrees of heart block, not every impulse from the atria is conducted to the ventricular region, and therefore some contractions of the represented region are lost.

On the ECG, manifestations of deceleration or optimal complexes are identified first.

Only after this is a wave detected, which corresponds to the contraction of the precardiac region, and contraction of the ventricles is not observed. This can happen with every fifth, fourth, third and any subsequent contraction.

Blockades that form without a previous slowdown in implementation can transform into full-fledged heart block. Treatment when a 2nd degree blockade is detected largely depends on the underlying disease.

In some cases, atropine and isadrin are used. If the heart rate is significantly reduced, then permanent electrical stimulation of the heart is used, namely a pacemaker.

Treatment methods

When a blockade is formed due to pathologies of the heart (myocarditis or acute myocardial infarction), the leading disease is first dealt with.

The recovery algorithm for blockages of the 2nd and 3rd degree is selected taking into account where the disturbance is located within the conductivity:

• Treatment is carried out with drugs such as isadrin or the introduction of atropine under the skin.
• At the treatment stage, physical exercises are completely excluded. loads.

• Drug therapy does not guarantee the desired effect.
• The only treatment option is electrical stimulation of the heart muscle.
• When the blockade is acute and occurs as a result of myocardial infarction, intermittent stimulation is carried out due to electricity.
• With a stable blockade, the presented measure must be carried out continuously.

• If stimulation is not possible, an Isuprelai or Euspiran tablet is placed under the patient’s tongue (in some cases, 0.5 tablets are used).
• For introduction into the vein, these drugs are dissolved in a composition with glucose (5%).

• Neutralized by eliminating glycosides.
• If the blockage, the rhythm of which does not exceed 40 beats within 60 seconds, persists even after stopping glycosides, Atropine is introduced into the vein.
• In addition, Unitol injections are injected into the muscles (up to 4 times during the day).
• If there is such a need (for medical reasons), then temporary electrical stimulation is performed.

You can learn more about 2nd degree heart block here.

Under the influence of medicinal components on the vagus nerve, situations are possible in which absolute blockage of the heart is transformed into partial.

Folk remedies

The use of folk recipes to restore health during heart blockade is also recommended to be agreed with a specialist. But first of all, you need to follow basic lifestyle recommendations.

It is necessary to avoid the consumption of alcohol and cigarettes, and to minimize the use of strong coffee and tea. It is undesirable to consume salt, as well as fried and fatty foods.

For a speedy recovery, salty and smoked dishes are excluded from the menu, and preference is given to fruits, vegetables, meat and fish with a low percentage of fat, as well as similar dairy products.

Traditional medicine can offer the following simple recipes that will help the heart muscle function fully:

• 2 tsp. Dried finely chopped valerian root is poured into 100 ml of boiling water and boiled under the lid for 15 minutes.
• The product is cooled and filtered; it should be consumed three times a day, 1 tbsp. l. before meals.

• To prepare it you need 1 tbsp. l. pour 400 ml of boiling water with a heap of lemon balm herb and let it cool until it cools 100%.
• After this, the product is filtered and taken 0.5 cups 3 times a day before eating.
• The presented mixture is in great demand among athletes.

• 1 tsp. The flowers of the plant are poured with 200 ml of boiling water and heated in a water bath for 15 minutes.
• The composition is cooled, filtered and diluted with water to 200 ml.
• Drink 0.5 cups 30 minutes before meals.

Mixing onions with an apple, for the preparation of which you need to mix 1 small head of regular onion. Next, grate 1 apple on a fine grater and mix the resulting mixture thoroughly. The mixture must be consumed 2 times in between meals.

Peppermint composition, for the preparation of which use 1 tbsp. l. finely chopped mint leaves, which are poured with 200 ml of boiling water. Infuse the mixture under the lid for at least 60 minutes. The decoction is filtered and consumed slowly over 24 hours.

It is necessary to avoid excessive physical and emotional stress, remember to adhere to a rest regime and carry out physical exercises as often as possible.

Consequences

The timing of disability is directly dependent on how difficult the leading disease is.

The prognosis depends on the underlying disease and the level of blockage. A pessimistic prognosis is associated with distal blockades, because they are prone to constant development - the consequences in this case will be the most severe.

Absolute heart block of the distal type is identified by the likelihood of fainting in 70% of cases. The blockade, which develops according to the proximal algorithm, is determined by the possibility of fainting in 25% of cases.

• if a primary attack of Morgagni-Adams-Strokes occurs and an pacemaker is not transplanted, then life expectancy is significantly reduced and will be no more than 2.5 years;
• the survival rate of patients increases due to permanent stimulation;
• the prognosis after transplantation is directly dependent on the nature of the leading disease.

If myocardial infarction of the anterior wall occurs, then with absolute blockade there is aggravated damage to the septum between the ventricles. This means that the prognosis is extremely unfavorable: the mortality rate from ventricular fibrillation or cardiac failure is identified in 90% of cases.

Read here what blockade of the left leg of the heart is.

The relationship between false chord and heart block is described in another article.

People should not neglect folk recovery methods, which will enable a person to live on without encountering blockades.

Sinoatrial block (SA): what it is, causes, symptoms, ECG, treatment

Sinoatrial block (sinoauricular, SA block) is considered one of the variants of sick sinus syndrome (SU). This type of arrhythmia can be diagnosed at any age; it is recorded somewhat more often in males; it is relatively rare in the general population.

In a healthy heart, the electrical charge is generated in the sinus node, which is located deep in the right atrium. From there it spreads to the atrioventricular node and the bundle branches. Due to the sequential passage of the impulse through the conductive fibers of the heart, the correct contraction of its chambers is achieved. If an obstacle arises in one of the areas, then the reduction will also be disrupted, then we are talking about a blockade.

With sinoatrial blockade, the reproduction or propagation of the impulse to the underlying parts of the conduction system from the main, sinus node is disrupted, therefore the contraction of both the atria and ventricles is disrupted. At a certain moment, the heart “misses” the impulse it needs and does not contract at all.

Different degrees of sinoatrial block require different therapeutic approaches. This disorder may not manifest itself at all, or may cause fainting and even death of the patient. In some cases, sinoatrial blockade is permanent, in others it is transient. In the absence of a clinic, you can limit yourself to observation; a 2-3 degree blockade requires appropriate treatment.

Causes of sinoatrial block

Among the main mechanisms of sinoauricular blockade are damage to the node itself, disruption of the propagation of impulses through the heart muscle, and changes in the tone of the vagus nerve.

In some cases, the impulse is not formed at all, in others it is present, but too weak to cause contraction of cardiomyocytes. In patients with organic damage to the myocardium, the impulse encounters a mechanical obstacle in its path and cannot pass further along the conducting fibers. Insufficient sensitivity of cardiomyocytes to electrical impulses is also possible.

Factors leading to sinoauricular block are considered:

1. Heart defects;
2. Inflammatory changes in the heart (myocarditis);
3. Cardiovascular form of rheumatism;
4. Secondary damage to heart tissue due to leukemia and other neoplasms, injuries;
5. Coronary heart disease (cardiosclerosis, post-infarction scar);
6. Myocardial necrosis (infarction);
7. Cardiomyopathy;
8. Vagotonia;
9. Intoxication with drugs when the permissible dose is exceeded or individual intolerance - cardiac glycosides, verapamil, amiodarone, quinidine, beta-blockers;
10. Organophosphorus poisoning.

The functioning of the SA is influenced by the activity of the vagus nerve, so when it is activated, impulse generation may be disrupted and SA blockade may occur. Usually in this case they talk about transient SA blockade, which appears on its own and goes away in the same way. This phenomenon is possible in practically healthy people, without anatomical changes in the heart itself. In isolated cases, idiopathic sinoauricular block is diagnosed when the exact cause of the pathology cannot be determined.

In children, conduction disturbances from the sinoatrial node are also possible. Typically, such arrhythmia is detected after 7 years of age, and a common cause is autonomic dysfunction, that is, the blockade is more likely to be transient, against the background of increased tone of the vagus nerve. Among the organic changes in the myocardium that can cause this type of blockade in a child are myocarditis, myocardial dystrophy, in which, along with SA blockade, other types of arrhythmias can be detected.

Types (types and degrees) of sinoatrial blockade

Depending on the severity of the arrhythmia, there are several degrees of it:

• SA blockade 1st degree (incomplete), when changes are minimal.
• SA blockade 2nd degree (incomplete).
• SA blockade 3rd degree (complete) is the most severe, the contraction of both the ventricles and atria is impaired.

With 1st degree block of the sinus node, the node functions, and all impulses cause contraction of the atrial myocardium, but this happens less frequently than normal. The impulse through the node passes more slowly, and therefore the heart contracts less often. It is impossible to record this degree of blockade on an ECG, but it is indirectly indicated by rarer, as expected, heart contractions – bradycardia.

With sinoatrial blockade of the 2nd degree, the impulse is no longer always formed, resulting in a periodic absence of contraction of the atria and ventricles of the heart. It, in turn, comes in two types:

• SA blockade 2nd degree, type 1 - the conduction of the electrical signal through the sinus node gradually slows down, as a result of which the next contraction of the heart does not occur. The periods of increase in the pulse conduction time are called Samoilov-Wenckebach periods;
• SA blockade of the 2nd degree, type 2 – contraction of all parts of the heart occurs after a certain number of normal contractions, that is, without periodic slowing down the movement of the impulse along the SA node;

Sinoauricular block of the 3rd degree is complete, when the next contraction of the heart does not occur due to the lack of impulses from the sinus node.

The first two degrees of blockade are called incomplete, since the sinus node, although abnormal, continues to function. The third degree is complete, when impulses do not reach the atria.

Features of ECG with SA blockade

Electrocardiography is the main way to detect heart blocks, through which uncoordinated activity of the sinus node is detected.

SA blockade of the 1st degree does not have characteristic ECG signs; it can be suspected by bradycardia, which often accompanies such blockade, or shortening of the PQ interval (a variable sign).

The presence of SA blockade can be reliably confirmed by ECG starting from the second degree of disorder, in which full cardiac contraction does not occur, including the atria and ventricles.

On the ECG at stage 2 the following are recorded:

1. Lengthening the interval between atrial contractions (A-P), and during the loss of one of the next contractions this interval will be two or more normal;
2. Gradual decrease in R-R time after pauses;
3. Absence of one of the next PQRST complexes;
4. During long periods of absence of impulses, contractions may occur generated from other sources of rhythm (atrioventricular node, bundle branches);
5. If not one, but several contractions occur at once, the duration of the pause will be equal to several R-R, as if they were occurring normally.

Complete blockade of the sinoatrial node (3rd degree), is considered when an isoline is recorded on the ECG, that is, there are no signs of electrical activity of the heart and its contraction, and is considered one of the most dangerous types of arrhythmia, when there is a high probability of death of the patient during asystole.

Manifestations and diagnostic methods of SA blockade

The symptoms of sinoatrial block are determined by the severity of disorders in the conductive fibers of the heart. In the first degree, there are no signs of blockade, as well as the patient’s complaints. With bradycardia, the body “gets used” to a rare pulse, so most patients do not experience any worries.

SA blockades of 2 and 3 degrees are accompanied by tinnitus, dizziness, discomfort in the chest, and shortness of breath. Against the background of a slower rhythm, general weakness is possible. If SA blockade has developed due to a structural change in the heart muscle (cardiosclerosis, inflammation), then an increase in heart failure is possible with the appearance of edema, cyanosis of the skin, shortness of breath, decreased performance, and enlarged liver.

In a child, the signs of SA blockade differ little from those in adults. Parents often pay attention to decreased performance and fatigue, blue discoloration of the nasolabial triangle, and fainting in children. This is the reason to contact a cardiologist.

If the interval between heart contractions is too long, then Morgagni-Adams-Stokes (MAS) paroxysms may occur, when the flow of arterial blood to the brain is sharply reduced. This phenomenon is accompanied by dizziness, loss of consciousness, noise, ringing in the ears, possible convulsive muscle contractions, involuntary emptying of the bladder and rectum as a result of severe brain hypoxia.

syncope with MAS syndrome due to sinus node blockade

Suspicion of the presence of a blockade in the heart arises already during auscultation, during which the cardiologist records bradycardia or loss of the next contraction. To confirm the diagnosis of sinoauricular block, the main methods are electrocardiography and 24-hour monitoring.

Holter monitoring can be performed for 72 hours. Long-term ECG monitoring is important in those patients in whom, if the presence of arrhythmia is suspected, no changes could be detected in a regular cardiogram. During the study, a transient blockade, an episode of SA blockade at night or during physical activity may be recorded.

Children also undergo Holter monitoring. The detection of pauses lasting more than 3 seconds and bradycardia of less than 40 beats per minute is considered diagnostically significant.

A test with atropine is indicative. The introduction of this substance to a healthy person will cause an increase in the frequency of heart contractions, and with SA blockade, the pulse will first double, and then just as rapidly decrease - a blockade will occur.

To exclude other cardiac pathologies or search for the cause of the blockage, an ultrasound of the heart can be performed, which will show the defect, structural changes in the myocardium, scarring area, etc.

Treatment

1st degree SA blockade does not require specific therapy. Usually, to normalize the rhythm, it is enough to treat the underlying disease that caused the blockade, normalize the daily routine and lifestyle, or discontinue medications that could disrupt the automatism of the sinus node.

Transient SA blockade against the background of increased activity of the vagus nerve is well treated by prescribing atropine and its drugs - bellataminal, amizil. The same medications are used in pediatric practice for vagotonia, which causes transient blockade of the sinus node.

Attacks of SA blockade can be treated medicinally with atropine, platyphylline, nitrates, nifedipine, but, as practice shows, the effect of conservative treatment is only temporary.

Patients with sinus node blockade are prescribed metabolic therapy aimed at improving myocardial trophism - riboxin, mildronate, cocarboxylase, vitamin and mineral complexes.

If SA blockade is recorded, beta blockers, cardiac glycosides, cordarone, amiodarone, and potassium supplements should not be taken, as they can cause even greater difficulty in the automaticity of the SA and worsen bradycardia.

If blockade of the SA node leads to pronounced changes in well-being, causes an increase in heart failure, and is often accompanied by fainting with a high risk of cardiac arrest, then the patient is offered to have a pacemaker implanted. Indications may also include Morgagni-Adams-Stokes attacks and bradycardia below 40 beats every minute.

In case of sudden severe blockade with Mroganyi-Adams-Stokes attacks, temporary cardiac stimulation is necessary, chest compressions and artificial ventilation are indicated, atropine and adrenaline are administered. In other words, a patient with such attacks may require full resuscitation measures.

If the exact reasons for the development of sinoatrial blockade have not been established, there are no effective measures to prevent this phenomenon. Patients who have already recorded changes in the ECG should correct them with the help of medications prescribed by the cardiologist, normalize their lifestyle, and also regularly visit the doctor and have an ECG taken.

Children with arrhythmias are often advised to reduce the overall level of exercise and reduce participation in sports sections and clubs. Visiting children's institutions is not contraindicated, although there are experts who advise limiting the child in this too. If there is no risk to life, and episodes of SA blockade are rather isolated and transient, then there is no point in isolating the child from school or going to kindergarten, but observation at the clinic and regular examination are necessary.

Sinus node arrest is a type of impulse formation disorder when the sinus node, the main pacemaker, stops functioning for some period.

Sinoatrial blockade is a type of conduction disorder in which an impulse, having originated in the sinus node, cannot “pass” to the atria. What happens when you stop sinus node. what about sinoatrial blockade , the clinical picture is identical. Moreover, even on an ECG it is not always possible to distinguish one from the other. Therefore, we will combine them into one article.

With these arrhythmias, pauses of varying durations occur both on the ECG and in the work of the heart. This does not mean that if the sinus node stops, the person will instantly die. Nature took care of the safety net.

If the sinus node fails, the atria or atrioventricular node takes over the pacemaker function. If for some reason these two sources also fail, then the last backup sources are the ventricles. However, they cannot maintain adequate heart function for a long time, since the frequency they can generate does not exceed 30-40 beats per minute, and this is at best.

It must be said that a stop of the sinus node can occur for a short time; for such a description of the electrocardiogram to appear, it is enough to record one stop and after a few seconds the native rhythm returns, so it is not always possible to reach backup sources.

There are many reasons for sinus node arrest, and in any case it is necessary to undergo a full cardiac examination, since sinus node arrest does not occur out of the blue, and it is the cause that will determine the treatment tactics and prognosis of the disease.

In conclusion, it must be said that the hearts of some patients throughout their lives work in the atrial rhythm or the rhythm of the atrioventricular junction. These backup sources are quite capable of ensuring adequate functioning of the heart, and if they fail, then there is only one way out - implantation of a pacemaker.

Sinoauricular block heart - a disturbance in the conduction of impulses from the sinus (sinoatrial) node to the atrial myocardium. This type of B. s. usually observed with organic changes in the atrial myocardium, but sometimes occurs in practically healthy people when the tone of the vagus nerve increases. There are three degrees of sino-auricular block (SAB): I degree - slowing down the transition of the excitation impulse from the sinus node and atrium; II degree - blocking the conduction of individual impulses; III degree - complete cessation of impulses from the node to the atria.

The causes of sinoauricular (SA) blockade may be coronary atherosclerosis of the right coronary artery, inflammatory changes in the right atrium with the development of sclerotic changes due to myocarditis, metabolic disorders in the atria, various intoxications and primarily cardiac glycosides, β-blockers, antiarrhythmic drugs quinidine series, poisoning with organophosphorus substances. Immediate causes of SA blockade:

1) the impulse is not generated in the sinus node;

2) the strength of the sinus node impulse is insufficient to depolarize the anterior heart;

3) the impulse is blocked between the sinus node and the right

Sinoauricular block can be I. II. III degree.

+ Treatments

Sinoauricular block

Sinoauricular block. When conduction disturbances of this type occur, the impulse is blocked at the level between the sinus node and the atria.

Etiology and pathogenesis. Sinoauricular block can be observed after heart surgery, in the acute period heart attack myocardium, in case of intoxication with cardiac glycosides, while taking quinidine, potassium supplements, beta-blockers. More often it is recorded with damage to the atrial myocardium, especially near the sinus node, by a sclerotic, inflammatory or dystrophic process, sometimes after defibrillation, very rarely in practically healthy individuals with increased tone of the vagus nerve. Sinoauricular block occurs in individuals of all ages; more often in men (65%) than in women (35%).

The mechanism of sinoauricular blockade has not yet been clarified. The question has not been resolved whether the cause of the blockade is a decrease in atrial excitability, or whether the impulse is suppressed in the node itself. In recent years, sinoauricular block is increasingly considered a sick sinus syndrome.

Clinic. Patients with sinoauricular block usually do not show any complaints or experience short-term dizziness during cardiac arrest. Occasionally during long stops hearts Morgagni-Edams-Stokes syndrome may occur.

By palpation of pulse and auscultation hearts loss of heart contractions and a large diastolic pause are detected. Loss of a significant number of heartbeats leads to bradycardia. Rhythm hearts regular or more often irregular due to changes in the degree of blockade, jumping contractions, extrasystole.

There are three degrees of sinoauricular block. With first degree blockade, the time of impulse transition from the sinus node to the atria is prolonged. Such a conduction disorder cannot be registered on an electrocardiogram and is detected only with the help of an electrogram. Second degree sinoauricular block in clinic observed in two versions: without Samoilov-Wenckebach periods and with Samoilov-Wenckebach periods.

First option recognized electrocardiographically by long pauses in which the P wave and the associated QRST complex are absent. If one cardiac cycle falls out, then the increased R-R interval is equal to twice the main R-R interval or slightly less. The value of the R-R interval depends on the number of heartbeats that occur. Usually there is a loss of one sinus impulse, but sometimes there are dropouts after each normal contraction (allorhythmia). Such sinoauricular block (2:1) is perceived as sinus bradycardia. Clinically, it can be determined only after a test with atropine or physical activity by the doubling of the rhythm, or by an electrocardiogram.

Second degree sinoauricular block with Samoilov-Wenckebach periods (second option) has the following features:

1) the frequency of discharges in the sinus node remains constant;

2) a long R-R interval (pause), including a blocked sinus impulse, shorter in duration than the double R-R interval preceding the pause;

3) after a long pause, a gradual shortening of the R-R intervals occurs;

4) the first R-R interval following a long pause is longer than the last R-R interval preceding the pause. In some cases, with this type of blockade, before long pauses (losses of impulses), there is not a shortening, but an extension of the R-R interval.

III degree sinoauricular block characterized by complete blockade of impulses from the sinus node with a persistent rhythm from the underlying parts of the conduction system (more often popping up replacement rhythms from the atrioventricular junction).

Diagnostics. Sinoauricular block should be distinguished from sinus bradycardia, sinus arrhythmia, blocked atrial extrasystoles, and second degree atrioventricular block.

Sinoauricular block and sinus bradycardia can be differentiated using atropine or exercise testing. U sick with sinoauricular block during these tests, the heart rate doubles, and then suddenly decreases by 2 times (elimination and restoration of the blockade). With sinus bradycardia, a gradual increase in rhythm is observed. With sinoauricular block, the extended pause is not associated with the act of breathing, but with sinus arrhythmia it is associated.

With a blocked atrial extrasystole, the electrocardiogram shows an isolated P wave, while with sinoauricular block there is no P wave and the associated QRST complex (i.e., the entire cardiac cycle is missing). Difficulties arise if the P wave merges with the T wave preceding the extended pause.

With atrioventricular block of the second degree, in contrast to sinoauricular block, the P wave is constantly recorded, an increasing increase in time or a fixed time of the P-Q interval is noted, followed by a blocked (without the QRST complex) P wave.

Treatment of sinoauricular block should be aimed at eliminating the cause that caused it (intoxication with cardiac glycosides, rheumatism, ischemic disease hearts etc.).

With a significant decrease in heart rate, which causes dizziness or short-term loss of consciousness, it is necessary to reduce the tone of the vagus nerve and increase the tone of the sympathetic nervous system. For this purpose, 0.5-1 ml of a 0.1% atropine solution is prescribed subcutaneously or intravenously or in drops (5-10 drops in the same solution 2-3 times a day). Sometimes they give effect adrenomimetic funds- zphedrine and drugs isopropylnorepinephrine (orciprenaline or alupent and isadrin). Ephedrine is used orally at 0.025-0.05 g 2-3 times a day or subcutaneously in the form of a 5% solution of 1 ml. Orciprenaline (alupent) is injected slowly into a vein, 0.5-1 ml of a 0.05% solution, intramuscularly or subcutaneously, 1-2 ml, or given orally in tablets of 0.02 g 2-3 times a day. Izadrin (novodrin) is prescribed under the tongue (until complete resorption) 1/g-1 tablet (1 tablet contains 0.005 g) 3-4 or more times a day. It must be remembered that an overdose of these drugs may cause headache, palpitations, tremors of the limbs, sweating, insomnia, nausea, vomiting (see also “Antiarrhythmics”).

In severe cases, especially when Morgagni-Edams-Stokes syndrome occurs, electrical stimulation of the atria is indicated (in acute cases - temporary, in chronic cases - permanent).

Prognosis for sinoauricular block depends on the nature of the underlying disease, as well as on its degree and duration, and the presence of other rhythm disturbances. In most cases, it is asymptomatic and does not lead to severe hemodynamic disturbances. However, if the blockade is accompanied by Morgagni-Edams-Stokes syndrome, the prognosis is unfavorable.

Prevention of sinoauricular blockade is a difficult task, since its pathogenesis is not clear enough. As with other rhythm disturbances, attention should be paid to treatment the underlying disease causing the blockade.

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