Complete AV block on ecg. Atrioventricular block. Degrees of atrioventricular blockade

Atrioventricular (atrioventricular) block(AV block) - a disorder of conduction function, expressed in slowing down or stopping the passage of an electrical impulse between the atria and ventricles and leading to a disorder of heart rhythm and hemodynamics. AV block may be asymptomatic or accompanied by bradycardia, weakness, dizziness, attacks of angina and loss of consciousness. Atrioventricular block is confirmed using electrocardiography, Holter ECG monitoring, and EPI. Treatment of atrioventricular block can be medication or cardiac surgery (implantation of a pacemaker).

General information

Atrioventricular block is based on a slowdown or complete cessation of the passage of the impulse from the atria to the ventricles due to damage to the AV node itself, the His bundle or the branches of the His bundle. Moreover, the lower the level of damage, the more severe the manifestations of the blockade and the more unsatisfactory the prognosis. The prevalence of atrioventricular block is higher among patients suffering from concomitant cardiac pathology. Among people with heart disease, I degree AV block occurs in 5% of cases, II degree - in 2% of cases, III degree AV block usually develops in patients over 70 years of age. Sudden cardiac death, according to statistics, occurs in 17% of patients with complete AV block.

The atrioventricular node (AV node) is part of the conduction system of the heart, providing sequential contraction of the atria and ventricles. The movement of electrical impulses coming from the sinus node is slowed down in the AV node, allowing the atria to contract and pump blood into the ventricles. After a short delay, the impulses spread along the His bundle and its legs to the right and left ventricles, promoting their excitation and contraction. This mechanism ensures alternate contraction of the atria and ventricles myocardium and maintains stable hemodynamics.

Classification of AV blocks

Depending on the level at which the disturbance of electrical impulse conduction develops, proximal, distal and combined atrioventricular blockades are distinguished. With proximal AV blockade, impulse conduction may be disrupted at the level of the atria, AV node, and His bundle branch; at distal – at the level of the branches of the His bundle; with combined ones, multi-level conduction disturbances are observed.

Taking into account the duration of development of atrioventricular block, it is divided into acute (with myocardial infarction, drug overdose, etc.), intermittent (intermittent - with ischemic heart disease, accompanied by transient coronary insufficiency) and chronic forms. According to electrocardiographic criteria (slowness, periodicity, or complete absence of impulse conduction to the ventricles), three degrees of atrioventricular block are distinguished:

I degree– atrioventricular conduction through the AV node is slowed down, but all impulses from the atria reach the ventricles. Clinically not recognized; on the ECG the P-Q interval is prolonged > 0.20 seconds.
II degree– incomplete atrioventricular block; not all atrial impulses reach the ventricles. The ECG shows periodic loss of ventricular complexes. There are three types of second-degree AV block according to Mobitz:

Mobitz type I - the delay of each subsequent impulse in the AV node leads to a complete delay of one of them and loss of the ventricular complex (Samoilov-Wenckebach period).

Mobitz type II - critical impulse delay develops suddenly, without a previous prolongation of the delay period. In this case, the absence of conduction of every second (2:1) or third (3:1) impulse is noted.

III degree- (complete atrioventricular block) - complete cessation of the passage of impulses from the atria to the ventricles. The atria contract under the influence of the sinus node, the ventricles contract at their own rhythm, less than 40 times per minute, which is not enough to ensure adequate blood circulation.

Atrioventricular blocks of the 1st and 2nd degrees are partial (incomplete), blockades of the 3rd degree are complete.

Reasons for the development of AV blockades

According to etiology, functional and organic atrioventricular blockades are distinguished. Functional AV blockades are caused by an increase in the tone of the parasympathetic nervous system. Atrioventricular block of the first and second degrees is observed in isolated cases in young physically healthy individuals, trained athletes, and pilots. It usually develops during sleep and disappears during physical activity, which is explained by increased activity of the vagus nerve and is considered a normal variant.

AV blockades of organic (cardiac) origin develop as a result of idiopathic fibrosis and sclerosis of the conduction system of the heart in various diseases. The causes of cardiac AV blockade can be rheumatic processes in the myocardium, cardiosclerosis, syphilitic heart disease, interventricular septal infarction, heart defects, cardiomyopathies, myxedema, diffuse connective tissue diseases, myocarditis of various origins (autoimmune, diphtheria, thyrotoxic), amyloidosis, sarcoidosis , hemochromatosis , heart tumors, etc. With cardiac AV blockade, a partial blockade may initially be observed, however, as cardiac pathology progresses, a third-degree blockade develops.

Various surgical procedures can lead to the development of atrioventricular blockade: aortic valve replacement, plastic surgery of congenital heart defects, atrioventricular RFA of the heart, catheterization of the right side of the heart, etc.

With second degree atrioventricular block, patients feel a loss of the pulse wave as interruptions in the heart area. With type III AV block, Morgagni-Adams-Stokes attacks occur: a decrease in heart rate to 40 or less beats per minute, dizziness, weakness, darkening of the eyes, short-term loss of consciousness, pain in the heart, cyanosis of the face, and possibly convulsions. Congenital AV block in patients of childhood and adolescence can be asymptomatic.

Complications of AV block

Complications from atrioventricular blockade are mainly caused by a pronounced slowdown in rhythm that develops against the background of organic heart damage. Most often, the course of AV block is accompanied by the appearance or worsening of chronic heart failure and the development of ectopic arrhythmias, including ventricular tachycardia.

The course of complete atrioventricular block may be complicated by the development of Morgagni-Adams-Stokes attacks associated with cerebral hypoxia as a result of bradycardia. The onset of an attack may be preceded by a feeling of heat in the head, attacks of weakness and dizziness; During an attack, the patient turns pale, then cyanosis and loss of consciousness develop. At this point, the patient may need chest compressions and mechanical ventilation, since prolonged asystole or the addition of ventricular arrhythmias increases the likelihood of sudden cardiac death.

Repeated episodes of loss of consciousness in elderly patients can lead to the development or worsening of intellectual-mnestic disorders. Less commonly, with AV blockade, the development of arrhythmogenic cardiogenic shock is possible, more often in patients with myocardial infarction.

In conditions of insufficient blood supply during AV blockade, phenomena of cardiovascular failure (collapse, fainting), exacerbation of coronary heart disease, and kidney diseases are sometimes observed.

Diagnosis of AV blocks

When assessing the patient's medical history in case of suspected atrioventricular block, the fact of past myocardial infarction, myocarditis, other cardiopathologies, and taking medications that interfere with atrioventricular conduction (digitalis, β-blockers, calcium channel blockers, etc.) is ascertained.

When auscultating the heart rhythm, a correct rhythm is heard, interrupted by long pauses, indicating loss of ventricular contractions, bradycardia, and the appearance of Strazhesko's cannon I tone. An increase in pulsation of the neck veins is determined compared to the carotid and radial arteries.

On the ECG, first degree AV block is manifested by a prolongation of the P-Q interval > 0.20 seconds; II degree - sinus rhythm with pauses, as a result of loss of ventricular complexes after the P wave, the appearance of Samoilov-Wenckebach complexes; III degree – a decrease in the number of ventricular complexes by 2-3 times compared to atrial complexes (from 20 to 50 per minute).

Additional laboratory tests for AV blockade are indicated in the presence of concomitant conditions and diseases (determination of the level of electrolytes in the blood during hyperkalemia, the content of antiarrhythmics in case of their overdose, enzyme activity during myocardial infarction).

Treatment of AV blocks

With first degree atrioventricular block that occurs without clinical manifestations, only dynamic observation is possible. If AV block is caused by taking medications (cardiac glycosides, antiarrhythmic drugs, β-blockers), dose adjustment or complete discontinuation is necessary.

In case of AV blockades of cardiac origin (myocardial infarction, myocarditis, cardiosclerosis, etc.), a course of treatment with β-adrenergic stimulants (isoprenaline, orciprenaline) is carried out, and then implantation of a pacemaker is indicated.

First aid drugs for the relief of Morgagni-Adams-Stokes attacks are isoprenaline (sublingual), atropine (intravenous or subcutaneous). For symptoms of congestive heart failure, diuretics, cardiac glycosides (with caution), and vasodilators are prescribed. As symptomatic therapy for the chronic form of AV blockade, treatment is carried out with theophylline, belladonna extract, and nifedipine.

A radical method of treating AV block is the installation of an electrical pacemaker (pacemaker), which restores normal rhythm and heart rate. Indications for implantation of an endocardial pacemaker are a history of Morgagni-Adams-Stokes attacks (even a single one); ventricular rate less than 40 per minute and periods of asystole of 3 or more seconds; AV block II degree (Mobitz type II) or III degree; complete AV block, accompanied by angina pectoris, congestive heart failure, high arterial hypertension, etc. To decide on surgery, consultation with a cardiac surgeon is necessary.

Forecast and prevention of AV blocks

The influence of developed atrioventricular block on the patient’s future life and ability to work is determined by a number of factors and, above all, the level and degree of blockade and the underlying disease. The most serious prognosis is for grade III AV block: patients are unable to work, and the development of heart failure is noted.

The prognosis is complicated by the development of distal AV blocks due to the threat of complete blockade and rare ventricular rhythm, as well as their occurrence against the background of acute myocardial infarction. Early implantation of a pacemaker can increase the life expectancy of patients with AV block and improve their quality of life. Complete congenital atrioventricular blocks have a more favorable prognosis than acquired ones.

As a rule, atrioventricular block is caused by an underlying disease or pathological condition, so its prevention is the elimination of etiological factors (treatment of cardiac pathology, avoidance of uncontrolled use of drugs that affect the conduction of impulses, etc.). To prevent worsening of the degree of AV block, implantation of a pacemaker is indicated.

Atrioventricular block is the cessation of nerve impulse transmission between the atria and ventricles of the heart.

This is what happens with the most severe atrioventricular block (3rd degree)

The harmonious functioning of the heart is coordinated by the autonomic conduction system of the heart. It consists of special muscle fibers that are capable of conducting nerve impulses. The “leader” of the autonomic conduction system of the heart is the autonomic nervous system.

The peculiarity of the conduction system of the heart is that its fibers are able to independently generate the impulse necessary for contraction. In this case, the number of impulses decreases from top to bottom.

The conduction system of the heart is called autonomous because it itself produces impulses for myocardial contraction. This gives a person a margin of safety for survival. In case of severe injuries, loss of consciousness and other disasters, the heart continues to beat, increasing the chances of life.

Normally, the sinus node generates a rhythm with a frequency of 60 to 90 beats per minute. The atria contract at this rate. The task of the atrioventricular part is to delay the excitation wave on its way to the ventricles. Contraction of the ventricles begins only after the atria have completed their work. The frequency from the atrioventricular part is 40–60 pulses. This is not enough for a full life, but still better than nothing.

The atrioventricular node is part of the conduction system of the heart

A condition in which the impulse is not conducted from the sinus node is called AV block. The lower its level, the fewer impulses the heart receives. A decrease in heart rate makes blood circulation ineffective and, in severe cases, threatens life.

A cardiologist treats heart blocks. It should be contacted if a person feels interruptions. After 40 years, it is advisable to consult a cardiologist annually in order to “catch” the problem at an early stage. Initial forms of blockades respond well to treatment, and you can live with them for many years. In the case of moderate blockades, they can be compensated for by regular medication use and proper alternation of exercise and rest. Severe cases are treated by implantation of a pacemaker, with which one can successfully live to an old age.

Why does this blockade occur?

There are several main reasons:

There are a lot of diseases that cause AV block. Rheumatic heart disease, amyloidosis, Addison's disease, thyrotoxicosis, collagenosis and other conditions can be distinguished. Researchers claim that the likelihood of heart block is inherited: mutations of the genes responsible for conducting the impulse are being actively studied.

Regardless of the cause, atrioventricular block can vary in severity. Mild diseases are treated by a cardiologist; in more complex cases, the participation of a cardiac surgeon is required.

Three degrees of severity

There are 3 degrees of severity: the first is the mildest, and the third is called complete or transverse heart block. The second degree is also divided into 3 subtypes. The degree of severity is determined by a combination of clinical signs and ECG results.

Electrocardiographic signs of AV blocks of varying degrees are as follows:

Blockades of 2 and 3 degrees develop in two cases: with high tone of the parasympathetic nervous system (has inhibitory functions) and with diseases accompanied by inflammation, infiltration, endocrine and metabolic disorders. The tone of the parasympathetic part of the autonomic nervous system increases with heavy sports loads and overdose of vasoactive drugs.

Characteristic symptoms

Atrioventricular block manifests itself differently depending on the severity.

1st degree

The first degree may not be clinically detected. This is an incidental finding in young people under 20 years of age, its frequency in the world is just over 1%. It reduces tolerance to heavy physical activity. Athletes are more susceptible to it; their frequency reaches almost 9%. With age, the number of people suffering from such a blockade increases to 5%.

This problem is found in almost all people suffering from myocarditis and severe infections. With recovery from the infection, the blockade also passes.

2nd degree

Manifestations of 2nd degree AV block are noticeable from the moment heart rhythm disturbances begin.

When the heart rate decreases, the minute volume, or the number of liters of blood that the ventricles can pump, decreases.
Initial manifestations are shortness of breath during exercise, vague chest pain, and weakness.
With a decrease in the frequency of beats, the patient feels interruptions, as if the heart freezes for a while.
Dizziness, darkening of the eyes, and brief fainting may occur.
Weakness, headaches, and shortness of breath increase.

These symptoms may be intermittent; a person does not see a doctor for a long time, attributing it to ordinary fatigue. The frequency of these blockades is up to 3% of the entire population in any country.

3rd degree

Atrioventricular block of the 3rd degree (or complete transverse) is life-threatening. All organs suffer from oxygen starvation and metabolic disorders.

The most striking symptom is Morgagni-Adams-Stokes, or fainting, which developed due to cerebral ischemia. 3 or 10 seconds after the blockade occurs with a heart rate of up to 40 beats per minute, the person suddenly turns pale, loses consciousness and falls. Usually after 1–2 minutes the blood flow is restored, the person comes to his senses and gets up, his skin turns red at this time. Needless to say, how dangerous this symptom is in an urban environment or while driving. If blood flow does not return on its own, immediate life-saving medical measures are required.

Differences in heart rate with different types of atrioventricular block

Diagnostics

Today, atrioventricular block is no longer a death sentence. First of all, the cardiologist prescribes an examination to find out all the details of the body’s condition. It includes Holter monitoring, ultrasound of the heart chambers, and laboratory tests.

Holter monitoring is a 24-hour recording of an ECG using a recorder or recorder that is attached to the patient’s body. Continuous recording can be maintained for several days. At the same time, the patient records all his actions in time: got up, walked, climbs the stairs, eats, communicates, and so on. By comparing activity activity and the ECG tape, the cardiologist gets an objective picture.

Treatment methods

1st degree

1st degree blockade does not require treatment unless it is caused by inflammation. Patients with endo- or myocarditis are treated in a cardiology hospital. The criterion for recovery is the disappearance of blockade on the ECG, restoration of normal sinus rhythm.

2nd degree

Second degree blockade of the second and third types is an indication for immediate hospitalization. Restoring rhythm is an urgent task. The doctor’s goal is to facilitate the passage of impulses from the atria to the ventricles; with AV blockade at the level of the atrioventricular node, atropine is used for this, but at a lower location the medicine will not help.

If a conduction interruption is recorded at the level of the left bundle branch or even lower, then electrical stimulation is needed. It is possible to restore normal rhythm using electrical stimulation; for this purpose, temporary stimulation is used when a probe electrode is inserted into the right atrium. This is a preparatory stage for the installation of a permanent pacemaker.

3rd degree

Complete transverse block is life-threatening and is treated in the intensive care unit. If the condition is caused by organic damage to the heart (infarction, Lenegra syndrome or idiopathic bilateral damage to the His bundle, cardiosclerosis), then adrenergic agonists are first used - orciprenaline or isoprenaline. Then the general condition of the person is assessed, whether his body can cope with a heart attack or adapt to cardiosclerosis. If adaptation does not occur and the rhythm does not hold, then a pacemaker is installed.

An artificial pacemaker is also called a pacemaker. The operation to install it is a minor one and is performed under local anesthesia. An active electrode under X-ray control will be inserted through the lateral saphenous vein of the arm into the right atrium, and a small titanium housing will be placed under the subcutaneous fat on the chest, usually on the left.

The pacemaker housing is placed under the subcutaneous fat of the chest. To ensure that it is not rejected by the body, it is made of titanium (or a special alloy), which is inert for our body

Forecast

Various AV blocks are the fourth most common cause of heart rhythm disturbances. On average, the prognosis for these conditions looks like this:

Patients with a pacemaker should avoid exposure to radar installations and high-voltage equipment. They cannot undergo MRI examinations or receive thermal physical therapy. You can return to normal life in a month and a half. Pacemakers are replaced within 5 to 15 years; this is their average service life.

AV block and distinctive features of 2nd degree

Atrioventricular block (AV block) is a rhythm conduction disorder characterized by abnormal propagation of electrical impulses from the atria to the ventricles.

Such a disorder of cardiac activity can lead to significant hemodynamic consequences, which makes the diagnosis and treatment of such a condition relevant.

Atrioventricular blockades of high (2 and 3) degrees are of greatest clinical importance.

Causes

The etiological factors leading to the occurrence of atrioventricular block are as follows:

Functional: autonomic dysfunction, psycho-emotional overload, reflex influence in pathology of internal organs.
Coronary: coronary heart disease, myocarditis, heart defects, cardiomyopathy, Lewy and Lenegra disease.
Toxic: overdose of adrenotropic drugs (beta blockers), chemicals (alcohol, heavy metal salts), endogenous intoxication associated with pathology of internal organs (jaundice, renal failure).
Electrolyte imbalance: hyperkalemia, hypermagnesemia.
Hormonal dysfunction: menopause, hypothyroidism.
Congenital disorders of atrioventricular conduction.
Mechanical: heart injuries.
Idiopathic.

Classification

According to the nature of the blockade:

Transient (transient).
Intermittent (intermittent).
Chronic (permanent).

The first type of pathology often occurs with myocardial infarction of the lower wall, which is associated with increased tone of the vagus nerve.

Depending on the location of the lesion in the conduction system, the following types of atrioventricular block are distinguished:

Proximal (at the level of the atria, AV node).
Distal (His bundle lesion).

The second type is considered a prognostically unfavorable form of rhythm disturbance.

It is customary to distinguish 3 degrees of pathology:

1 is characterized by slow conduction of an electrical impulse in any part of the conduction system.
At 2, there is a gradual or unexpected blocking of one, and less often two or three impulses.
Degree 3 represents a complete cessation of the conduction of the excitation wave and the functional ability of pacemakers of the 2nd–3rd order.

Along with this, degree 2 is divided into 2 types - Mobitz 1 and Mobitz 2, the characteristics of which will be discussed below.

Clinical picture of AV blockade 2nd degree

Clinical manifestations of AV blockade depend on its type, the presence of concomitant pathology, and the level of damage to the conduction system. It can range from asymptomatic to loss of consciousness with the onset of convulsive syndrome. In patients with type 1 2nd degree atrioventricular block, in most cases there are no symptoms.

It can be observed as a side effect during treatment with beta blockers, some calcium antagonists, and digitalis preparations.

Often this pathology can be observed in patients with acute myocardial infarction in the lower wall. Functional disorder of AV conduction type Mobitz 1 is observed in young people during sleep and in athletes.

Atrioventricular block type 2, which often accompanies acute myocardial infarction in the anterior wall, is considered more unfavorable.

Patients complain of chest pain, slow and arrhythmic pulse, shortness of breath, and general weakness.

Due to a decrease in heart rate and a decrease in the minute volume of blood ejection, cerebral circulation suffers, which will manifest itself as dizziness, confusion, and fainting.

In severe cases, such a rhythm disorder is accompanied by loss of consciousness with the occurrence of clonic convulsions, which is characterized by a change in the color of the skin (cyanosis), a decrease in blood pressure, and shallow breathing.

Diagnostics

Impairment of impulse conduction is diagnosed based on complaints, anamnesis, objective examination, laboratory and instrumental examination. The main complaint of patients with atrioventricular block is bradycardia and irregular pulse. From the anamnesis, you can find out information about provoking factors (stress, heavy physical activity), the presence of chronic diseases, treatment with certain drugs. During the examination, a rare irregular pulse is noticed; in the jugular veins, a separate large pulse wave is detected by auscultation; a periodically loud first tone is determined.

Electrocardiography and 24-hour Holter monitoring remain the gold standard for diagnosing rhythm disturbances. AV blockade of the 2nd degree on the cardiogram tape has the following characteristic features

gradual lengthening of the P-Q interval, interrupted by loss of the ventricular (QRS) complex with a preserved P wave;
after the complex falls out, a normal P-Q interval is recorded, followed by a repetition of the lengthening;
The rhythm is sinus and often irregular.
Mobitz 2:
regular or chaotic loss of the ventricular complex with preservation of the P wave;
the P-Q interval is normal or increased without a tendency to progressively lengthen;
sometimes expansion and deformation of the ventricular complex;
The rhythm is sinus, but not always correct.

In case of transient blockade, 24-hour Holter monitoring is more informative.

Additionally, laboratory (general blood and urine tests, blood biochemistry, hormonal status studies) and instrumental (ultrasound diagnostics, scintigraphy, coronary angiography) examinations are carried out, which allows us to establish a violation of the internal organs and detect structural abnormalities of the heart leading to arrhythmia.

Therapy of AV blockades of the 2nd degree

Treatment depends on the type of blockade, the severity of the patient’s condition, and the etiological causes of the disease.

The following treatment methods are distinguished:

Medication tactics involve the use of drugs to restore rhythm.

In the case of AV blockade, the universal drug is atropine.

However, the most effective is the installation of a permanent or temporary pacemaker. More often, such tactics are necessary for Mobitz 2, when in type 1 patients are mostly subject to dynamic observation.

To successfully treat the pathology, it is necessary to identify the cause of the rhythm disturbance and take measures to eliminate it using various methods.

Treatment of Morgagni–Adams–Stokes syndrome

A Morgagni–Adams–Stokes attack in a patient’s life may be the first and last, so this condition requires the provision of emergency resuscitation measures of the following nature:

Place the patient in a horizontal position with the head end elevated.
Ensure airway patency and venous access.
Monitor vital functions.
Oxygen is supplied according to indications.
Intravenous injection of atropine at the recommended dose.
Carrying out electropulse therapy if appropriate equipment is available.
Delivery of the patient to the hospital.

Transient 2nd degree AV block

Transient 2nd degree AV block, if Holter monitoring reveals delays (pauses) in the conduction of an electrical impulse (signal) lasting more than 3 seconds, even if the disease is asymptomatic, is an indication for implantation of a pacemaker. Transient AV block of the 2nd stage, if delays longer than 3 seconds are not detected, require observation by a cardiologist (arrhythmologist) with periodic daily ECG monitoring. If the disease progresses, a decision will be made to install a pacemaker.

Transient 2nd degree AV block, accompanied by syncope (fainting caused by a temporary interruption of blood flow to the brain), is considered life-threatening and requires the installation of an artificial cardiac pacemaker (APM) - a pacemaker. Transient AV block, stage 2. otherwise called transient - it can be complete or partial, but, in general, it tends to progress with age.

In some cases, 2nd degree AV block is considered normal for young people during sleep and may resolve (or not recur) on its own. However, there are clear criteria when installing a pacemaker is required: with sinus rhythm for the atria, with a delay of more than 3 s, with atrial fibrillation - more than 5 s.

They definitely don’t take you to serve in the army if you have an ECS, but with a transient 2nd degree AV block they can take you, because The blockade is not permanent. In this case, we are usually talking about a staff position. If you have permanent fainting, you will not be accepted into the army.

Transient 2nd degree AV block with Wenckebach periodicity means Mobitz type I - it, as a rule, being the first or second degree, does not require special treatment, but requires observation by a cardiologist. For 2nd degree AV block type Mobitz II, permanent pacing is indicated.

Treatment of transient 2nd degree blockades

Treatment of transient 2nd degree AV blocks is carried out only by implantation of an electrical pacemaker. Atropine can be used while waiting for the pacemaker to be installed, but medications are not used as an independent treatment. Atropine is ineffective for complete AV block because does not affect conduction in the His–Purkinje bundle.

Treatment for transient 2nd degree AV block of type 1 is often not required - it occurs during sleep even in healthy people, but the disease is classified as unfavorable and, if diagnosed, requires observation by a specialist.

Atrioventricular block (AV) of the heart: causes, degrees, symptoms, diagnosis, treatment

Normally, the human heart beats at a rate of 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, sinoatrial, intraatrial, atrioventricular and intraventricular blockades are distinguished. 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.

Statistical data

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.

Causes

1st degree AV block can occur normally in healthy people if there is no underlying 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 a hypotonic type of vegetative-vascular dystonia, 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):

Cardiac ischemia. 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.
Acute and subacute myocardial infarction. The mechanism of the blockade is similar, only the cause of the disruption of impulse conduction is both foci of ischemic tissue and necrotic (dead) myocardial tissue.
Congenital and acquired heart defects. 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.

Cardiosclerosis, in particular after myocarditis. 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.

Arterial hypertension, long-standing and leading to hypertrophic or obstructive left ventricular cardiomyopathy. The mechanism of blockade development is similar to previous diseases.

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 an attack of MES (Morgagni-Edams-Stokes) and is life-threatening, since this type of conduction disorder can lead to complete cardiac arrest. 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 emergency medical team or be examined by a therapist (cardiologist/arrhythmologist) at a clinic at the place of residence 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 a minute or less).

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

Ultrasound of the heart (echocardioscopy), 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,
Holter monitoring of 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 notices 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 an artificial pacemaker, which 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 can lead to sudden cardiac death or arrhythmogenic shock. In addition to acute complications, in patients with long-term AV block, the course of chronic heart failure is aggravated, and discirculatory encephalopathy 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 2nd and 3rd degrees. 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.

Atrioventricular block (AV block) is a partial or complete disruption of the conduction of the excitation impulse from the atria to the ventricles.

Causes of AV block :

organic heart diseases:
- chronic ischemic heart disease;
- acute myocardial infarction;
- cardiosclerosis;
- myocarditis;
- heart disease;
- cardiomyopathy.
drug intoxication:
- glycoside intoxication, quinidine;
- overdose of beta-blockers;
- overdose of verapamil and other antiarrhythmic drugs.
pronounced vagotonia;
idiopathic fibrosis and calcification of the cardiac conduction system (Lenegra disease);
fibrosis and calcification of the interventricular septum, mitral and aortic valve rings (Lewy disease);
damage to the myocardium and endocardium caused by connective tissue diseases;
electrolyte imbalance.

Classification of AV blocks

stability of the blockade.
- transient (transitory);
- intermittent (intermittent);
- constant (chronic).
blocking topography.
- proximal level - at the level of the atria or atrioventricular node;
- distal level - at the level of the trunk of the His bundle or its branches (the most unfavorable type of blockade in prognostic terms).
degree of AV block.
- AV block of the first degree - slowing of conduction in any part of the conduction system of the heart;
- AV block of the second degree is a gradual (sudden) deterioration of conduction in any part of the conduction system of the heart with periodic complete blocking of one (two, three) excitation impulses;
- AV block of the third degree (complete AV block) - complete cessation of atrioventricular conduction and the functioning of ectopic centers of the 2nd and 3rd order.

Depending on the level of blocking of the excitation impulse in the atrioventricular system, the following types of AV blockades are distinguished, each of which, in turn, can achieve varying degrees of blocking of the excitation impulse - from I to III degrees (at the same time, each of the three degrees of blockade can correspond to different levels of conduction disturbance):

Internodal block;
Nodal block;
Brainstem blockade;
Three-bundle block;
Combined blockade.

Clinical symptoms of AV block :

unequal frequency of venous and arterial pulses (more frequent contractions of the atria and rarer contractions of the ventricles);
“giant” pulse waves that arise during the period of random coincidence of the systole of the atria and ventricles, having the character of a positive venous pulse;
periodic appearance of a “cannon” (very loud) first tone during auscultation of the heart.

1st degree AV block

all forms 1st degree AV block:
- correct sinus rhythm;
- increase in the PQ interval (more than 0.22 s with bradycardia; more than 0.18 s with tachycardia).
nodular proximal form First degree AV block (50% of all cases):
- increasing the duration of the PQ interval (mainly due to the PQ segment);
- normal width of P waves and QRS complex.
atrial proximal form.
- an increase in the PQ interval by more than 0.11 s (mainly due to the width of the P wave);
- often split P wave;
- the duration of the PQ segment is no more than 0.1 s;
- QRS complex of normal shape and duration.
distal three-beam form blockades:
- increased PQ interval;
- the width of the P wave does not exceed 0.11 s;
- widened QRS complex (more than 0.12 s) deformed like a two-bundle block in the His system.

2nd degree AV block

all forms 2nd degree AV block:
- Sinus irregular rhythm;
- Periodic complete blocking of the conduction of individual excitation impulses from the atria to the ventricles (absence of the QRS complex after the P wave).
nodal form AV block (Mobitz type I):
- a gradual increase in the width of the PQ interval (from one complex to another), interrupted by the loss of the ventricular QRST complex while maintaining the P wave;
- normal, slightly widened PQ interval, recorded after loss of the QRST complex;
- the above-described deviations are called Samoilov-Wenckebach periodics - the ratio of P waves and QRS complexes is 3:2, 4:3, 5:4, 6:5, etc.
distal form AV block (type II Mobitz):
- regular or random loss of the QRST complex while maintaining the P wave;
- constant normal (widened) PQ interval without progressive lengthening;
- widened and distorted QRS complex (sometimes).
2nd degree AV block type 2:1.
- loss of every second QRST complex while maintaining correct sinus rhythm;
- normal (widened) PQ interval;
- possibly an expanded and deformed ventricular QRS complex with a distal form of blockade (non-permanent sign).
progressive 2nd degree AV block.
- regular or random loss of two (or more) ventricular QRST complexes in a row with a preserved P wave;
- normal or widened PQ interval in those complexes where there is a P wave;
- widened and deformed QRS complex (non-constant sign);
- the appearance of replacement rhythms with severe bradycardia (non-permanent sign).

Third degree AV block (complete AV block)

all forms complete AV block:
- atrioventricular dissociation - complete separation of atrial and ventricular rhythms;
- regular ventricular rhythm.
proximal form Third degree AV block (the ectopic pacemaker is located in the atrioventricular junction below the block):
- constant intervals P-P, R-R (R-R >P-P);
- 40-60 ventricular contractions per minute;
- The QRS complex is practically unchanged.
distal (trifascicular) form complete AV block (the ectopic pacemaker is located in one of the branches of the bundle branch):
- atrioventricular dissociation;
- constant intervals P-P, R-R (R-R >P-P);
- 40-45 ventricular contractions per minute;
- The QRS complex is widened and deformed.

Frederick's syndrome

The combination of third degree AV block with atrial fibrillation or flutter is called Frederick's syndrome. With this syndrome, the conduction of excitation impulses from the atria to the ventricles completely stops - chaotic excitation and contraction of individual groups of atrial muscle fibers are observed. The ventricles are excited by the pacemaker, which is located in the atrioventricular junction or in the ventricular conduction system.

Frederick's syndrome is a consequence of severe organic lesions of the heart, which are accompanied by sclerotic, inflammatory, and degenerative processes in the myocardium.

ECG signs of Frederick's syndrome :

atrial fibrillation (f) or atrial flutter (F) waves, which are recorded instead of P waves;
non-sinus ectopic (nodal or idioventricular) ventricular rhythm;
correct rhythm (constant R-R intervals);
40-60 ventricular contractions per minute.

Morgagni-Adams-Stokes syndrome

Second- and third-degree AV blockades (especially distal forms) are characterized by a decrease in cardiac output and hypoxia of organs (especially the brain), caused by ventricular asystole during which effective contractions do not occur.

Causes of ventricular asystole :

as a result of the transition of second degree AV block to complete AV block (when the new ectopic ventricular pacemaker located below the level of blockade has not yet begun to function);
sharp inhibition of automatism of ectopic centers of the second and third order during third degree blockade;
flutter and ventricular fibrillation observed with complete AV block.

If ventricular asystole lasts more than 10-20 seconds, convulsive syndrome develops ( Morgagni-Adams-Stokes syndrome), caused by brain hypoxia, which can be fatal.

Prognosis for AV block

AV block I degree and II degree (Mobitz type I)- the prognosis is favorable, since the block is often functional in nature and rarely transforms into a complete AV block (or Mobitz type II);

Second degree AV block (Mobitz type II) and progressive AV block- has a more serious prognosis (especially the distal form of block), since such blockades aggravate the symptoms of heart failure, are accompanied by signs of insufficient cerebral perfusion, and often transform into complete AV block with Morgagni-Adams-Stokes syndrome;

Complete AV block has an unfavorable prognosis, because is accompanied by rapid progression of heart failure, deterioration of perfusion of vital organs, and a high risk of sudden cardiac death.

Treatment of AV blocks

1st degree AV block— treatment of the underlying disease + correction of electrolyte metabolism is necessary, no special treatment is required;

2nd degree AV block (Mobitz I)- IV atropine (0.5-1 ml 0.1% solution), if ineffective - temporary or permanent electrical stimulation of the heart;

Second degree AV block (Mobitz II)— temporary or permanent electrical stimulation of the heart;

3rd degree AV block- treatment of the underlying disease, atropine, temporary electrical stimulation.

Atrioventricular block 2nd degree

Atrioventricular block of the second degree or heart block of the second degree is characterized by a violation, delay or interruption of the conduction of the atrial impulse through the atrioventricular node to the ventricles.

Types of 2nd degree blockades

Although patients with second-degree block may be asymptomatic, a variant called Mobitz type I atrioventricular block can still cause noticeable symptoms. With AV block of the second degree of the 1st type (Mobitz-I or with the Samoilov-Wenckebach periodicity), the P-Q intervals are successively lengthened, and the R-R intervals are reduced until the impulse from the atria ceases to be conducted to the ventricles, then after the P wave the complex There is no QRS. Then the cycle of changes in the P-Q and R-R intervals is repeated until the next loss of the QRS complex. The duration of each period is described through the ratio of P waves and QRS complexes. (4:3; 3.2 and so on). In atrial fibrillation, second-degree AV block of type 1 can manifest itself as periodically occurring long R-R intervals after their consistent decrease. In a group study of elderly men (mean age 75 years) with Mobitz type I atrioventricular block, it was found that implantation of a pacemaker prolonged the life of these patients.

With second degree AV block of the 2nd type (Mobitz-I), periodic loss of the QRS complex occurs without changes in the P-Q interval. The frequency of the blockade is described by the ratio of P waves and QRS complexes (4.3; 3:2). Atrioventricular block of the Mobitz type II can lead to complete cardiac arrest with the associated risk of increased mortality.

Symptoms of second degree blockade

Patients with second degree atrioventricular block may experience a wide range of symptoms:

Absence of symptoms (most common in Mobitz type I patients, such as well-trained athletes and persons without organic heart disease)

Dizziness, weakness or loss of consciousness (more common in Mobitz type II)

Chest pain if heart block is due to ischemia or myocarditis

Periodically occurring irregular heartbeats

Episodes of bradycardia

Phenomena of insufficient tissue perfusion including hypotension

Symptoms of 2nd degree atrioventricular block may resemble a complete block of the left bundle branch.

ECG changes

To identify and determine the type of atrioventricular block of the second degree, an ECG study is used:

· Blockade Type I Mobitz. A gradual, from one complex to another, increase in the duration of the P - Q R interval, which is interrupted by the loss of the ventricular QRST complex (while the P wave remains on the ECG)

· After the loss of the QRST complex, a normal or slightly extended P - Q R interval is again recorded. Then everything is repeated (Samoilov-Wenckebach period). The ratio of P and QRS is 3:2, 4:3, etc.

· Blockade Type II Mobitz. Regular (type 3:2, 4:3, 5:4, 6:5, etc.) or random loss of the QRST complex (while maintaining the P wave)

The presence of a constant (normal or extended) P-QR interval without its progressive lengthening. Sometimes widening and deformation of the QRS complex.

· Atrioventricular block II degree type 2:1. Loss of every second QRST complex while maintaining correct sinus rhythm. The P-QR interval is normal or extended. With the distal form of blockade, expansion and deformation of the ventricular QRS complex is possible (unstable sign).

First aid for second degree atrioventricular block

Emergency care for second degree atrioventricular blockade consists of intravenous administration of 1 ml of a 0.1% atropine solution with 5-10 ml of a 0.9% sodium chloride solution, and the administration of one isadrin tablet under the tongue. During a Morgagni-Adams-Stokes attack (i.e., when periods of prolonged ventricular asystole lasting longer than 10-20 s occur during a second-degree block, the person loses consciousness, a convulsive syndrome similar to epileptic develops, which is caused by cerebral hypoxia), a cardiac pulmonary resuscitation. Under no circumstances should cardiac glycosides or novocainamide be administered. Also read first aid for cardiac arrhythmia. After assistance is provided, the patient is transferred to the cardiology team or hospitalized on a stretcher in the cardiology department.

AV (atrioventricular block)

Atrioventricular block is a type of heart arrhythmia in which the transmission of impulses from the atria to the ventricles is disrupted.

According to its genesis, atrioventricular block can be functional and organic. In the first case, we are talking about a neurogenic blockade caused by an increase in the tone of the vagus nerve, in the second - about a rheumatic process in the myocardium, atherosclerosis of the coronary vessels, infarction of the interventricular septum or syphilitic damage to the heart. This is the so-called cardiac form of atrioventricular block. With this form, at first there may be an incomplete blockade, but as the pathological process progresses, a complete blockade develops. The prognosis depends both on the underlying disease and on the degree of the blockade itself.

Three degrees of AV block

There are three degrees of atrioventricular block.

First degree atrioventricular block

First degree atrioventricular block is characterized by a slowdown in the conduction of impulses from the atria to the ventricles. Does not cause subjective sensations. Auscultation can detect a weakening of the first tone and an additional atrial sound.

The ECG shows a prolongation of the PQ interval of more than 0.18-0.2 s.

With this type of blockade, no special treatment is required.

Second degree atrioventricular block

With second-degree atrioventricular block, single impulses from the atria sometimes do not pass through the ventricles. If this phenomenon occurs rarely and only one ventricular complex is lost, patients may not feel anything, but sometimes they feel moments of cardiac arrest, during which dizziness or darkening occurs in the eyes. Symptoms increase with the loss of several ventricular complexes in a row (an advanced type of blockade).

The ECG may record periodic prolongation of the PQ interval followed by a single P wave that does not have a subsequent ventricular complex (type I block with Wenckebach periodicity). Typically this type of block occurs at the level of the atrioventricular junction.

Another option (type II atrioventricular block appears on the ECG as loss of QRS complexes against the background of normal duration or equally elongated PQ intervals. The ratio of P waves and QRS complexes can be varied: 3. 2, 4. 3, etc. It is also possible to lose several in a row ventricular complexes, accompanied by previously described clinical manifestations.

Third degree atrioventricular block

With third-degree block, or complete atrioventricular block, impulses from the atria do not reach the ventricles, as a result of which the ectopic secondary center of heart automaticity begins to act, the impulses of which spread through the ventricles and cause their contraction. In this case, patients often complain of general weakness, fatigue, dizziness, shortness of breath, short-term convulsions, and a Morgagni-Adams-Stokes attack.

During auscultation, rare cardiac activity is heard, the first heart sound varies in intensity, sometimes strong (cannonball). Blood pressure is significantly increased. The ECG shows independent activity of the atria and ventricles. The frequency of P waves exceeds the frequency of QRS complexes, extended or normal duration.

The combination of atrial fibrillation with complete atrioventricular block is called Frederick's phenomenon.

Incomplete atrioventricular block

The interval between contraction of the atria and ventricles is prolonged. With incomplete blockade, depending on how severe the disturbance in the passage of the impulse is, three degrees are distinguished.

I degree blockade is the most common and mildest form. With it, all impulses pass from the atrium to the ventricles, but the transit time is extended to 0.2-0.4 seconds or more instead of the normal 0.18-0.19 seconds and the ventricles contract with some delay.
Second degree blockade is characterized by a gradual prolongation of the time of passage of the impulse from the atrium to the ventricles, followed by the loss of one of the contractions as a result of the moment of complete obstruction. In this case, patients complain of heart palpitations and dizziness. Clinically, this manifests itself in a long diastolic pause and periodic loss of pulse. During this period of extended diastole, conduction capacity is restored.
With third degree blockade, the conductivity of impulses is so reduced that they periodically do not reach the ventricles and contractions of the latter fall out at certain intervals (1:2, 1:3, etc.).

Treatment. In case of incomplete atrioventricular block, treatment is determined by the causative factors that caused it.

Complete atrioventricular block

With this blockade, the passage of impulses from the atria to the ventricles is completely disrupted and the latter switch to an independent automatic rhythm; in this case, contraction impulses arise at some point of the conduction system below the atrioventricular node.

The number of ventricular contractions is determined by the location of the automatic impulse. The further it is from the atrioventricular node, the less frequent the contractions of the ventricles, the number of which with complete blockade can reach 40-30-15 per minute. When the contractions of the atria and ventricles coincide, the sonority of the first tone increases sharply - Strazhesko’s “cannon tone”.

Complete blockade is diagnosed clinically: when examining the patient in a supine position, it is possible to count 70-80 undulations of the jugular vein with a pulse of 30-40.

With long intervals between individual contractions of the ventricles, especially at the moment of transition of incomplete atrioventricular block to complete, an acute disorder of cerebral circulation may occur, including ischemia.

Clinical picture

The clinical picture is different - from a slight darkening of consciousness to epileptiform convulsions, which is determined by the duration of ventricular arrest (from 3 to 10-30 seconds); pulse up to 10-20 beats per minute, it is almost not palpable, blood pressure cannot be heard. This is Morgagni-Edams-Stokes syndrome. Attacks can be repeated several times during the day and be of varying intensity; lasting up to 5 minutes can be fatal.

At the moment of transition of incomplete blockade to complete, ventricular fibrillation may occur, which is the cause of sudden death. To suppress ventricular fibrillation or fibrillation, electrical defibrillation is applied to the heart through the chest, under the influence of which the circular transmission of excitation is stopped.

Ventricular fibrillation can be reversible with prompt action.

Atrioventricular block is a slowing or stopping of impulses from the atria to the ventricles. For the development of atrioventricular block, the level of damage to the conduction system can be different - conduction disturbance in the atria, in the atrioventricular junction, and even in the ventricles.

The causes of atrioventricular block are the same as for other conduction disorders. However, independently developing degenerative-sclerotic changes in the conduction system of the heart are also known, which lead to atrioventricular block in the elderly (Lenegra and Lev's diseases).

The presence of congenital atrioventricular block is accompanied by such congenital heart defects as ventricular septal defect, endocardial fibroelastosis, less commonly coarctation of the aorta, tetralogy of Fallot, tricuspid valve atrophy, aneurysm of the membranous part of the septum. Atrioventricular block is also observed, which is inherited in an autosomal dominant manner and manifests itself at 30-60 years of age. Before its occurrence, the appearance of conduction blocks in the bundle branches is often noted.

Atrioventricular block (atrioventricular) is a disorder of the conduction of excitation from the atria to the ventricles. Clinical symptoms and electrocardiographic manifestations can be observed with conduction disturbances at the level of:

atrial tract,
in the atrioventricular node,
in the trunk,
in the bundle of His.

According to V. Doshchitsin’s classification, in functional diagnostics there are, respectively, 4 types of atrioventricular blockades, 3 proximal (located at the beginning of the conduction system of the heart, listed first) and one distal (final):

atrial,
nodal,
stem,
trifascicular (three-bundle).

They can only be distinguished based on ECG analysis. There are cases of combinations of different types. Since the atrioventricular node occupies a central place in the formation of blockades, it is necessary to recall its structure and role.

What is the atrioventricular node?

The atrioventricular node (Ashofa-Tavara) is a collection of special myocardial cells in the lower part of the right atrium near the interatrial septum. The size of the node is 3x5 mm. In terms of importance of rank, it represents a second-order automatic center (after the sinus node) and is called upon to take on the role of a pacemaker in the event of a failure of a higher-ranking pacemaker.

Czech scientist Jan Purkinje was the first to describe special heart cells: they consist, like myocytes, of actin and myosin, but do not form a clear structure for contraction, and are oversaturated with calcium ions. It turned out that these features make it possible to create electrical impulses or spontaneously excite. This makes them related to neurons. Subsequently, 2 types of cells were distinguished in the conduction system of the heart:

some create electrical impulses;
others organize their conduction from the atria to the ventricles.

Nutrition is delivered to the cells in 90% of cases through a branch of the right coronary artery, in 10% of cases - from the left circumflex artery of the heart.

Depending on the density, the knot is formed by three layers of different compactness. And in longitudinal size it is functionally divided into two channels:

α - slow;
β - fast.

The correct functioning of cells and channels ensures the uninterrupted flow of impulses from the sinus node to the ventricles and synchronizes the work of all parts of the heart.

Reasons for the blockade

The reasons for the blockade may be:

functional influence of the central nervous system through the vagus nerve (observed in healthy people, athletes);
the effect of drugs from the digitalis group;
inflammatory process during rheumatic attack, myocarditis of various etiologies caused by childhood infections, sore throat, influenza;
area of necrosis or ischemia during the development of myocardial infarction;
focal and diffuse cardiosclerosis;
hyperkalemia and acidosis;
myocardial dystrophy in the conduction system zone;
consequences of hypertrophic changes in hypertension, myocardiopathy;
post-traumatic scars on the heart.

If conductive pathways enter the affected area during a heart attack, they lose their properties.

Types of atrioventricular block

Atrioventricular block is divided into:

incomplete - despite impaired conduction, most impulses, albeit late, reach the ventricles;
complete - a rupture of the atrioventricular communication occurs.

By time:

short-term and permanent;
random and periodic.

In addition to the listed types, blockade is distinguished according to three degrees of severity. They have ECG differences and characterize the depth of damage to the conduction pathways.

Characteristics of disorders during first degree blockade

Atrioventricular block of the 1st degree means a slowdown in the transit time of the impulse from the atria to the ventricles to 0.2 seconds or more (this corresponds to a widening of the PQ interval on the ECG) at a normal rhythm frequency.

In cases of proximal blockade, the shape of the ventricular complex does not change. In the distal version, the QRS complex is deformed and widened. Its width is over 0.3 sec. indicates a sign of combined conduction disorder.

The diagnostic value of first degree blockade is most significant in myocarditis. After treatment it disappears. But it is impossible to make a diagnosis based on one ECG sign alone. Clinical symptoms must be taken into account first.

The ECG shows differences in the blockade in the proximal and distal areas

Characteristics of disorders during second degree blockade

2nd degree blockade means that some impulses from the atria are not conducted into the ventricles. The ECG shows “loss” of ventricular complexes. In this case, the atrial and ventricular contractions are counted separately and the ratio is calculated (for example, blockade 3:1 or 5:1).

There are 3 types of second degree atrioventricular block:

Type I is also called Wenckebach or Mobitz type I - the ECG reveals PQ intervals with a gradual lengthening, then there is a loss of ventricular contraction. The sign is called the Wenckebach-Samoilov period. More typical for blockade in the proximal sections, so the ventricular complexes are not changed. Rarely, atrioventricular block of the first type is combined with impaired conduction in the His bundles, due to which the QRS widens.
Type II or Mobitz II- loss of complexes from the ventricles also occurs, but there are no previous lengthenings of PQ. Associated with impaired incomplete conduction at the level of the trifascicular bundle, therefore the ventricular complexes are often dilated and deformed.
Type III - prolapse occurs in the correct fixed order (every second, third or quadruple complex of the ventricles), and bradycardia is observed. It is considered an indicator of progression of the cause of the blockade. Possible at both proximal and distal levels. The QRS complex either changes or maintains the correct shape.

Mobitz type II (arrows indicate loss of every second ventricular complex)

Characteristics of disorders during third degree blockade

The third degree is equivalent to complete atrioventricular block. Impulses from the atria do not enter the ventricles at all, so the atria and ventricles of the heart contract independently of each other at their own pace. As a rule, the ventricles are more difficult to excite, so they “work” more slowly.

Also, like the two milder degrees, complete atrioventricular block can occur due to proximal or distal lesions.

Proximal complete blockade causes a ventricular rhythm that originates in the atrioventricular node, bradycardia of about 50 per minute, ventricular complexes are not changed, contractions occur synchronously.

The distal block is characterized by altered QRS complexes. The number of contractions slows down to 25–30.

A combination of complete atrioventricular block with atrial flutter or fibrillation (Frederick's syndrome) is rarely observed. The ECG reveals frequent atrial waves against the background of rare ventricular contractions.

Clinical picture

With a first-degree blockade, as a rule, the patient does not present any specific complaints. Changed health is associated with the underlying disease. In the second or third degree, circulatory disorders of a compensatory and adaptive nature occur: each contraction of the ventricles becomes larger in volume, which leads to myocardial hypertrophy. Cardiac pathology is usually accompanied by a number of symptoms:

Bradycardia of 30 beats per minute causes insufficient blood flow to the brain, dizziness occurs, and short-term loss of consciousness is possible.
Patients feel rare strong impulses (beats) of the heart into the chest. This is caused by the overlap of the rhythm of contractions of the atria and ventricles and the formation of single complete regular systoles.
When listening to the patient's heart, they have the characteristic of a “cannon shot”. During examination of the neck, a pronounced pulsation of the veins is detected due to the return wave of blood into the jugular vein.
For diagnosis, an important point is the absence of acceleration of the pulse after physical activity, or any fluctuations when holding the breath while taking a deep breath.

The distances between atrial and ventricular contractions are not changed, but are not connected into a single complex

If the blockade is caused by an inflammatory process or unfinished scarring, then all the signs are inconsistent.

In patients with pathological menopause and vegetative-vascular dystonia, the influence of the vagus nerve is pronounced. This is determined by conducting a test with Atropine. After a small dose is administered subcutaneously, the blockade is removed.

A severe manifestation of complete atrioventricular block is Morgagni-Adams-Stokes syndrome, caused in half of the cases by short-term ventricular asystole with preserved atrial flutter. The other half is represented by the outcome of flutter or ventricular fibrillation (hyperdynamic form).

Treatment

Treatment of atrioventricular block is determined by the causes of the pathology.

If the rhythm disorder is associated with an acute overdose of digitalis preparations:

immediately stop taking the medication;
gastric lavage is usually ineffective; 30 minutes after administration, activated charcoal has a greater effect, which should be given several times;
Antidigoxin and Atropine are administered by injection;
Phenytoin and Lidocaine are indicated when blockade is combined with ventricular arrhythmias;
if it is not possible to immediately administer Antidigoxin, the potassium concentration should be reduced by intravenous administration of a solution of glucose with insulin, ingestion of Polystyrene sulfonate ion exchange resin, Hypothiazide;
In order to eliminate acidosis, a solution of sodium bicarbonate (soda) is injected dropwise.

The beautiful plant is very deceptive when included in folk recipes; it is safe to use better prepared preparations as prescribed by a doctor.

It is necessary to remember the ineffectiveness of the methods of forced diuresis, hemosorption and hemodialysis in this case.

In the absence of effect and persistent bradycardia, external cardiac pacing is used. The endocardial type of stimulation is not indicated, since there remains a risk of ventricular fibrillation and death.

When the blockade is associated with increased tone of the vagus nerve, the following have a good effect:

preparations with Atropine (suppositories with belladonna, Zelenin drops);
Adrenaline and Izadrin have the opposite effect.

To treat an inflammatory focus that interrupts the conduction of impulses, the following are used:

antibiotics;
large doses of corticosteroid hormones;
Hypothiazide as a potassium-removing drug is recommended for concomitant hyperkalemia;
To remove local acidification, small doses of an alkaline solution are used.

If the blockades are ischemic in nature, a full range of medications is used to dilate blood vessels, eliminate impaired metabolism in cells, and reduce the ischemic area:

fast and prolonged action nitrates;
coronary agents;
β-blockers even with bradycardia 50 per minute.

Atropine solution is used when there is a threat of transition to a more severe degree.

With frequent attacks of Morgagni-Adams-Stokes, defibrillation is performed, and the issue of installing an artificial pacemaker is decided.

Serious difficulties for the doctor are caused by incipient heart failure with edema, attacks of shortness of breath against the background of atrioventricular block and bradycardia. The most common remedy - digitalis preparations - cannot be prescribed due to the severity of the type of blockade. In such cases, they resort to a pacemaker with a given rhythm. The device allows you to temporarily remove the patient from a state of heart failure using conventional means.

Treatment for atrioventricular block requires caution and frequent monitoring of electrocardiographic changes. Therefore, patients need to come regularly for scheduled examinations. It is not recommended to use any folk remedies.

Atrioventricular block (syn. atrioventricular block, AV block) is a disorder in the conduction of electrical impulses from the atria to the ventricles, against which the heartbeat slows down. If the victim is not provided with emergency assistance in a timely manner, there is a high probability of death.

The disease can be acquired during life or inherited. In most situations, pathology develops in those patients who have.

Sometimes the disease is asymptomatic, but often the clinical picture includes severe dizziness, angina, weakness and attacks of loss of consciousness.

The main diagnostic measures are instrumental procedures, in particular daily ECG monitoring. The diagnostic process must necessarily include laboratory tests and manipulations performed directly by a doctor.

Treatment of AV block depends on the severity of the disease, but most often conservative methods are sufficient. Patients may require cardiac surgery - implantation of a pacemaker.

According to the International Classification of Diseases, Tenth Revision, the disease has an individual code. The ICD-10 code is I44.

Etiology

Atrioventricular heart block occurs due to a slowdown or complete cessation of the passage of the impulse from the atria to the ventricles, which develops against the background of damage:

atrioventricular node;
His bundle;
atrial tract;
trunk of the His bundle.

It is worth considering that the lower the level of damage, the more severe the symptoms and the worse the prognosis.

The congenital form is extremely rarely diagnosed - only in 1 baby out of 20 thousand newborns. In such cases, the occurrence of the disease is influenced by:

complete absence of sections of the conduction system;
other congenital cardiac anomalies;
a large dose of medications taken by a woman during pregnancy.

Acquired blockade can form as a result of such diseases:

hypotonic type of course;
in acute or subacute form;
secondary;
moved earlier ;
obstructive left ventricular cardiomyopathy;
traumatic brain injuries;
and other endocrine disorders;
infections;
acute poisoning of the body, for example, from medications, alcoholic beverages or chemicals;
or acidosis;
or - one of the most common provocateurs of illness in children;
rheumatic diseases that have caused complications on the heart;
the formation of malignant or benign neoplasms in the myocardium or other structures of the heart;
or ;
sclerosis of the heart vessels;
diffuse connective tissue diseases.

In addition to the above diseases, the causes of AV block may include certain medical interventions:

aortic valve replacement;
treatment of congenital heart defects;
right heart catheterization;
radiofrequency ablation of the heart.

Often pathology becomes a consequence of irrational use of drugs:

beta blockers;
cardiac glycosides;
calcium channel blockers;
lithium salts;
antiarrhythmics.

Classification

There are several main types of the disease:

complete AV block - characterized by rupture of the atrioventricular communication;
incomplete AV block - almost all impulses, albeit delayed, reach the ventricles.

Depending on the duration, the pathology is:

short-term (transient AV block) and permanent;
random and periodic (transient AV block).

There are several degrees of severity, which differ in the clinical picture and ECG data:

Atrioventricular block of the 1st degree in children or adults - is expressed by a slowdown in the time of passage of an impulse from the atria to the ventricles from 0.2 seconds or more. Heart rate remains normal.
2nd degree AV block - some impulses from the atria do not reach the ventricles.
3rd degree AV block - impulses from the atria do not reach the ventricles at all. In such cases, they speak of complete atrioventricular block.

It is worth noting that clinicians distinguish several types of disease of 2 degrees of severity:

Type 1 (Wenckebach variety or Mobitz 1). The delay of each subsequent impulse in the atrioventricular node is fraught with a complete delay of one of them and loss of the ventricular complex.
Type 2 (2nd degree AV block Mobitz 2). It is characterized by the sudden development of a critical impulse delay. There is a lack of conduction of every 2 or 3 impulses.
Type 3. Every 2, 3 or 4 pulses occur in a certain order. Bradycardia develops.

Among all persons who were diagnosed with atrioventricular block, the following incidence of pathology is noted:

1st degree AV block in children and adults - 5%, in 2% it is observed in healthy individuals, for example, in people in whose lives sports are of great importance;
2nd degree AV block - expressed in 2%;
3rd degree AV block is the most common because it has pronounced symptoms and often develops at the age of 70 years and older.

Symptoms

The severity of symptoms is influenced by the following factors:

level of conduction disturbance;
degree;
etiology;
severity of concomitant heart disease.

First clinical signs:

dyspnea;
weakness and weakness;
unmotivated fatigue;
feeling of tightness in the chest;
attacks of dizziness;
loss of consciousness for a short period of time.

With 2nd degree AV block, the symptoms will be as follows:

palpable sinking of the heart;
minor headaches;
severe but short-term dizziness;
constant weakness and fatigue;

If the disease progresses to stage 3, the symptoms of atrioventricular block will be as follows:

darkening of the eyes;
severe dizziness;
pain in the heart area;
seizures;
blue discoloration (cyanosis) of the facial skin;
decrease in heart rate to 40 or less beats per minute;
loss of consciousness.

It is noteworthy that congenital atrioventricular block can be completely asymptomatic.

Diagnostics

Establishing the correct diagnosis is carried out by a cardiologist, who must study the results of laboratory and instrumental examinations and independently carry out a number of manipulations.

Thus, the primary diagnosis for AV block includes:

studying the medical history - to search for diseases that could precede the onset of pathology;
collection and analysis of life history - to establish the fact of inadequate use of medications;
listening to the patient using a phonendoscope to determine heart rate;
a detailed survey - to identify the first time of onset and intensity of symptoms, which will indicate the form and nature of the disease.

Among the most informative instrumental procedures it is worth highlighting:

ECG and EchoCG;
Ultrasound of the heart;
daily ECG monitoring;
CT or MRI of the heart;
MSCT and EPI.

Laboratory tests are of an auxiliary nature and are limited to general clinical and biochemical blood tests.

Treatment

Treatment tactics are determined by the severity of the disease and whether incomplete or complete AV block is diagnosed in the patient.

If there is asymptomatic or first degree atrioventricular block caused by taking medications, take a wait-and-see approach and completely stop taking any medications.

In other cases, to cure the disease, the following is prescribed:

"Atropine";
antibacterial substances;
corticosteroid hormones.

Second degree atrioventricular block is treated with the following methods:

taking coronary lytics and beta-blockers;
injection of sodium bicarbonate and alkaline solutions, Antidigoxin and Atropine may be required;
the use of diuretics, vasodilators and cardiac glycosides.

For 3rd degree atrioventricular block, treatment is performed only using cardiac surgery methods. A cardiac pacemaker is implanted for the following indications:

Heart rate less than 40 beats per minute;
periods of asystole of 3 or more seconds;
severe course of complete atrioventricular block;
arterial hypertension;
development of complications.

Possible complications

If a patient diagnosed with atrioventricular block does not receive emergency care in a timely manner, the likelihood of developing the following consequences is extremely high:

occurrence or worsening in a chronic form;
ectopic;
ventricular;
brain hypoxia;
arrhythmogenic cardiogenic shock;
exacerbation of coronary artery disease and kidney pathologies;
cardiovascular failure;
- observed in 17%, especially when people were not provided with adequate emergency care;
intellectual-mnestic disorders - more often manifested in elderly patients.

Prevention and prognosis

To avoid the development of atrioventricular block, there are no specific measures. Prevention of the disease will consist of general simple rules, including:

maintaining a healthy and moderately active lifestyle;
refusal to take medications that were not prescribed by the attending physician;
early detection and full treatment of those diseases that can provoke an anomaly;
regular visits to a cardiologist and other specialists to undergo a complete medical preventive examination.

Atrioventricular block is a dangerous disease, the prognosis of which depends on the severity. The most favorable outcome is for stage 1 and 2 AV block when treatment is started in a timely manner.

The most serious prognosis is observed with 3rd degree AV block - in such cases complications most often develop that make patients unable to work or even lead to death.