Blockade of the bundle branch legs
The blockade of the bundle legs is a malfunction in the operation of the cardiac activity, caused by the partial or total absence of impulse transmission along the conducting pathways of the atrioventricular bundle, provoking a delay in the excitation of the ventricular myocardium and accompanied by changes in the electrocardiographic pattern.
In the structure of cardiovascular diseases, accompanied by cardiac disorders, blockage of the bundle of the bundle has up to 2.5% of cases, among which a large proportion is the blockade of the anterior superior branch of the left branch of the bundle. The localization of this branch in the projection of the aortic valve ring promotes the development of blockade due to the constant effect of increased pressure in the ventricular cavity, as well as the pathology of the aortic valve.
On the second place on occurrence there is an blockade of the right leg of a bundle of the Head, which has no connection with any other cardiac pathology. The blockade of the posterior branching of the left bundle of the bundle is rare, as an isolated pathology, due to the fact that it is supplied from both the anterior and posterior descending coronary arteries. Recent scientific research has refuted the three-beam structure of the conducting pathways of the heart, although this concept is still used today for practical purposes. According to this theory, all possible intraventricular blockades are divided according to the principle of localization:
1. Blockade in the projection of one beam:
* impaired transmission of electrical impulse along the anterior branch of the left foot of the atrioventricular bundle;
* blocking the transfer of impulse along the posterior branch of the left foot of the atrioventricular bundle;
* violation of the conductivity function along the fibers of the right leg of the bundle.
2. Blockade of both beams:
* Combined blockade (anterior upper branch of the left leg and the right leg of the bundle of His);
* hemiblocade (the posterior lower branch of the left leg and the right leg of the bundle of His).
3. Blockade of three beams.
The causes of blockade of the bundle branch legs
The blockade in the conducting system of the atrioventricular bundle can occur both against the background of complete well-being in healthy people (blockade of the right leg of the bundle of His), and be a consequence of organic damage to the cardiac myocardium. In some cases, the atrioventricular blockade is an accidental finding in ECG recording and becomes the reason for the patient's on-site examination for the presence of cardiac pathology.
As a rule, the violation of the electrical impulse is due to the presence of a focus in the cardiac muscle with a non-typical structure (necrosis, sclerosis, myocardial defect), therefore, in most cases, persistent complete blockade of the bundle's legs is a consequence of the organic pathology of the heart muscle.
Among the cardiac causes of blockade of the bundle of the bundle are the leading positions in the frequency of occurrence: hypertensive disease with a tendency to a crisis course, acute coronary insufficiency and transmural myocardial infarction , hypertrophic and dilated forms of cardiomyopathies, and the use of surgical methods for treating heart diseases.
The dependence of the onset of two-beam blockades and the patient's pathology of the aortic valve (congenital aortic defects), as well as coarctation of the aortic arch, was reliably proven.
Important in the emergence of the blockade is the state of electrolyte balance in the body. Thus, hyperkalemia and hypercalcemia with a combined decrease in the level of sodium in the blood can become a provocateur of the development of any form of disturbance of the rhythm of the cardiac activity, including blockade of the legs of the bundle of His.
There is a separate type of blockade of the legs of the atrioventricular bundle of iatrogenic genesis (the appearance of signs of blockade after the application of separate groups of drugs - antiarrhythmic, diuretic drugs and cardiac glycosides).
The main pathogenetic mechanism for the development of impaired conduction of the pulse along the conduction paths of the bundle of the bundle is the appearance of focal organic lesion as a result of compression due to edema, necrosis followed by sclerosis, changes in the excitability and duration of the refractory period, and a decrease in the potential level on the membrane.
The blockages of the fibers of the conduction system of the bundle are not accompanied by gross disturbances of the rhythm and unpleasant sensations in the patient, because the legs of the atrioventricular bundle are drivers of the fourth order rhythm, that is, they are able to generate no more than 30 pulses per minute, unlike sine Atrial node generating up to 80 pulses for 1 minute. When this or that branching of the atrioventricular bundle is blocked, the pulses begin to be generated and propagate along the conductive paths of Purkinje fibers with a slowed frequency up to 20 pulses per minute. These circumstances do not pose a threat to the life of the patient, however, the prolonged course of the disease provokes irreversible changes in the brain due to impaired blood flow to the brain structures.
Symptoms of the bundle branch blockade
Three types of blockades are distinguished in the course of the disease: persistent, transient (blockades alternate with unchanged intraventricular conduction) and alternating (ECG changes are determined for the blockade of one, then the second leg).
This form of disturbance of the rhythm of cardiac activity refers to the category of intraventricular blockades, therefore it is not accompanied by gross violations of the rhythm and heart rate. Patients suffering from blockage of the legs of the atrioventricular bundle, mostly present nonspecific complaints that do not allow to make a correct preliminary diagnosis during the initial examination of the patient: dizziness and short-term disturbances of consciousness, a feeling of shortness of breath, reduced efficiency and fast fatigue.
If the patient has a blockage of the left leg of the bundle of His, which develops against the background of the cardiovascular pathology, patients present complaints characteristic of certain nosological forms (cardialgia or typical attacks of angina, symptoms of heart failure). With percussion of the heart in such a situation, the expansion of cardiac dullness is determined, and the auscultatory signs of blockade is the splitting of the II tone on the apex of the heart, which is dependent on respiratory phases.
In the laboratory examination of blood and urine, no changes are detected, only examination of the hormonal status allows to determine the extracardiac nature of the blockade of the bundle of the bundle.
Holter ECG monitoring is an obligatory instrumental method for researching a patient with suspected intragastric blockade. This method allows not only to determine the changes in ECG, characteristic of a form of blockade of the bundle of the bundle, but also to register clinical symptoms that arise in the patient at the time of the blockade. An obligatory condition for properly conducted Holter monitoring is the constant observation of the patient with his own sensations and the recording of all changes and the time of their occurrence. Maintaining such a diary in some cases makes it possible to determine the cause of the blockade, the elimination of which helps prevent the development of a disturbance in the rhythm of cardiac activity.
In a situation when ECG registration fails to reveal reliable symptoms of atrial-ventricular bundle blockade, the patient is shown to perform a transesophageal electrophysiological study to assess the state of the cardiac conduction system.
Despite the absence of severe clinical symptoms, blockages of the legs of the bundle of the Hisnus do not always have a favorable course and in the situation of the existing chronic pathology of the heart can be fatal.
The consequences of the blockade of the legs of the bundle of the Gysa arise with complete blockade and are characterized by the development of Morganya-Adams-Stokes attacks. In order to prevent this condition, which is dangerous for the life and health of the patient, the patient is recommended to have the product of implantation of a pacemaker.
Blockade of the right leg of the bundle
In the general structure of the incidence of blockade of the bundle of the bundle, a blockade of the right leg accounts for up to 4.5%, among which the majority of patients are men of advanced age who suffer from ischemic heart disease with episodes of acute coronary insufficiency.
Congenital etiologic factors in the occurrence of blockade of the right leg of the atrioventricular bundle are the anomalies of the development of the fibers of the bundle of the bundle, as well as the disturbance of the normal position of the vessels. Acquired risk factors are chronic heart diseases, accompanied by organic myocardial pathology (ischemic heart disease, hypertensive heart disease with frequent crises, acute myocardial infarction and postinfarction cardiosclerosis ).
The clinical manifestations of the blockade of the right foot of the atrioventricular bundle are non-specific and largely characterize the main cardiac pathology, which triggered the development of the blockade. At the initial examination of the patient in favor of blockade of the right leg of the bundle, His is indicated by the splitting of the II tone in all auscultative points, caused by asynchronous contraction of the ventricles and non-simultaneous closing of the aortic and pulmonary valves. In addition to the splitting of the second tone, its intensification during inspiration is noted, since during this period the physiological slowing of the closing of the valves of the pulmonary valve takes place.
When determining the tactics of treating a patient with blockade of the right leg of the atrioventricular bundle, it should be based on the presence or absence of acute cardiac pathology. So, with blockade, which developed against a background of acute myocardial infarction, emergency admission of a patient to a cardiac hospital is mandatory. If the blockade of the right leg of the bundle has developed in a completely healthy young man, this condition does not require medical treatment, since it rarely provokes complications and has favorable predictions for the patient's life.
In any situation, even if there is a concomitant cardiac pathology, the prognosis for the life of a patient with right leg blockade is more favorable than that of the left foot of the atrioventricular bundle, since this blockade is almost never transformed into a complete atrioventricular block .
Blockade of the left bundle branch leg
The risk group for the disease of blockage of the left leg of the bundle of the Hisnus are elderly women in the age group of 50-70 years old, suffering from hypertensive heart disease for a long time. At a young age in healthy people, this form of rhythm disturbance practically does not occur.
An objective examination of patients with left bundle branch blockade in 90% of cases is accompanied by auscultation of lengthening of the first tone in combination with a split second tone due to uncoordinated ventricular contraction, uneven closure of aortic and pulmonary valves that increase during exhalation.
The blockade of an electric pulse in the anterior branch of the left leg of the atrioventricular bundle arises and progresses in diseases accompanied by an increase in the thickness of the myocardium in the projection of the left ventricle (pathology of the interventricular septum, myocardial infarction, myocarditis of infectious origin, congenital and acquired aortic valve defects). As a result of this blockade, the impulse is not transmitted to the side wall, but spreads "from below-upward". Thus, excitation of the posterior wall of the left ventricle occurs first, and lateral and anterior walls are excited with delay.
The blockade of the left foot of the atrioventricular bundle is the main provoker of the onset of complete atrioventricular block, ventricular tachycardia and ventricular fibrillation, which in 70% of cases are fatal, so this rhythm disturbance is unfavorable for the life of the patient.
Incomplete bundle block bundle branch
To assess the mechanism of development of incomplete blockade of the legs of the bundle, the features of the conduction system of the heart should be taken into account. The atrioventricular fascicle has wide dimensions, therefore, conduction disturbance can be observed only in part of the fibers belonging to the right or left leg of the bundle, and in this situation electrocardiography reveals signs of incomplete intraventricular blockade.
A characteristic difference between the incomplete blockade of the right bundle of the bundle and the full one is the splitting of the QRS complex into V1-2 leads in the absence of a pronounced expansion of this ventricular complex.
The left leg of the atrioventricular bundle has two branches, in this connection, under incomplete blockade of this leg is meant a violation of the advance of the electric pulse along one of the branches. In order to determine which branch of the left bundle of the bundle is blocked, it is necessary to evaluate the presence of a deviation of the electrical axis of the heart on the ECG in the II standard lead (the expressed left-hand diagram indicates blockade of the anterior branch, and the deviation of the electric axis to the right testifies to the blockade of the posterior branch).
Clinical manifestations of incomplete blockade of the bundle of the bundle are minimal, and with objective examination of the patient, no auscultatory changes are detected.
Complete blockade of the bundle branch legs
As a result of a complete blockade of the right leg of the bundle, the normal course of systolic excitation of the ventricular myocardium is disrupted. Thus, excitation from the interventricular septum is transmitted only to the cardiac muscle of the left ventricle, and the excitation to the right ventricle is transmitted with a delay, since the transfer of the pulse in this case occurs via other conducting paths (Purkinje fibers).
Such anomalous excitation of the right ventricle is reflected electrocardiographically as an expansion of the ventricular complex in leads V1-2 with an unchanged value of the S-wave, which reflects the state of left ventricular excitation. The delay in the transfer of impulse to the right ventricle is also reflected in the registration of the ECG in the form of negativity of the T wave in the right thoracic leads.
The main distinctive criterion for a complete blockade of the right bundle of the bundle is the increase in the QRS aggregated ventricular complex in the II standard lead, the magnitude of which is more than 0.12 s.
The pathogenesis of the complete blockage of the left leg of the bundle is identical, that is, the excitation from the interventricular septum is reached only by the right ventricle, from which, through the Purkinje network of fibers, the electrical impulse is transferred to the cardiac muscle of the left ventricle of the heart.
In this situation, all electrocardiographic changes are recorded in the left thoracic leads (widening of the QRS summation complex in the second standard lead, discordant depression of the ST segment).
Blockade of the bundle of the bundle on the ECG
Very often, ECG diagnostics becomes the only effective method of instrumental examination, which allows one to make a conclusion about the presence of a blockade of the legs of the bundle already with the primary treatment of the patient. There are both common signs of ECG pattern changes, and specific for each form of blockade. Obligatory conditions for decoding the registration of electrocardiography is the evaluation of the width and shape of the QRS complex in all leads, and the definition of the thoracic leads in which the QRS complex has a cleavage.
The signs of blockage of the upper branch of the left foot of the atrioventricular bundle are:
- criteria for deviating the electric axis to the left not less than 45%;
- expansion of the QRS complex about 0,9-0,11 s;
- the presence of specific ventricular complexes of the type qR, rS / r in standard leads;
- in the thoracic leads, the amplitude R decreases and the depth S increases.
For the blockade of the posterior lower branch of the left leg of the bundle, the following ECG signs of impulse conduction are characteristic:
- increased amplitude of the R wave in the III lead as compared to the II lead, which indicates a sharp deviation of the electric axis of the heart by more than 90%;
- a slight expansion of the QRS complex (not more than 0.11 s);
- width of tooth Q in III and aVF leads less than 0.04 s;
- presence of a deep tooth S in I and aVL leads with the formation of the rS wave.
The complete blockade of the left bundle of the bundle is characterized by more significant changes in ECG registration:
- a sharp expansion of the QRS complex for more than 0.12 s;
- complete absence of S and Q teeth in I, aVL and V6 leads with simultaneous expansion of the R wave with a serrated vertex;
- formation of the complex rS and QS in III, aVF and V2 leads;
- Definition of a skewed depression of the T wave and segment ST and dominant R wave in I, aVL and V6 leads with discordant oblique rise of the ST segment in the leads V1-2.
The only difference between an incomplete blockade and a complete block is a slight change in the ST segment and a slight expansion of the QRS complex.
Diagnostic electrocardiographic criteria for complete blockade of the right bundle of the bundle are:
- extended to 0.12 with QRS complex;
- registration in the leads V1-2, aVF and III of the ventricular complex of the rSR type;
- widening of the tooth S and its prevalence over the width of the tooth R in aVL, I and V6 leads;
- ST segment depression in V1-2 leads with simultaneous negation of the T wave;
Two-beam blockades have their own characteristic electrocardiographic changes, caused by a violation of the conductivity of the pulse along each of the bundles of the Gys.
With a two-beam blockade of the anterior branch of the left leg and the right foot of the atrioventricular bundle, the following electrocardiographic signs are observed:
- sharp left-hand deviation of the electric axis;
- an extension of more than 0.12 from the QRS complex;
- skewed depression of the ST segment in V1-2 leads with simultaneous negation of the T wave with the formation of a ventricular complex of the rSR type;
- an increase in the depth of the S wave in leads II, III and aVF with the formation of the rS complex.
The localization of the blockade in the posterior branching of the left leg and right leg is also accompanied by a combination of characteristic ECG registration changes:
- sharp right-hand deviation of the electric axis;
- an extension of more than 0.12 from the QRS complex;
- ST segment depression in V1-2 leads with simultaneous negation of the T wave;
- the depth of the tooth S is greater than the depth of the tooth R in aVL and I leads.
When decoding ECG registration, it is necessary to carefully evaluate the detected changes and to compare them with the patient's clinical symptoms, since in some cases a two-beam blockade of the bundle of the bundle can simulate ECG signs of acute transmural myocardial infarction.
Treatment of bundle branch blockade
Due to the fact that in most cases the blockade of the legs of the atrioventricular bundle of the Gysa is an accidental finding in the recording of electrocardiography and is not accompanied by a gross organic lesion of the heart muscle, there is no specific medical and surgical treatment of this pathology.
People with signs of blockage of one of the legs of the bundle of His, especially those taking place in intermittent form, are recommended to follow simple rules during the attack, thereby helping to eliminate the attack of a partial intraventricular blockade:
- It is necessary to completely exclude physical activity during an attack, and if possible, take a horizontal position for several minutes;
- it is recommended to perform simple breathing exercises with alternating deep inspiration and exhalation, as well as a delay in breathing during the "exhalation" phase. This exercise allows a few minutes to remove the signs of blockade.
As a preventive measure to reduce the number of seizures, as well as prevent its transformation into a more life-threatening atrioventricular blockade, it is recommended that a certain number of diet and dietary rules be followed:
- obligatory daily night sleep lasting not less than eight hours;
- correction of eating behavior with the exception of products containing cholesterol and daily consumption of foods high in fiber;
- an annual visit to the cardiologist and the passage of a control electrocardiographic and ultrasound examination.
Etiopathogenetic therapy is used only in the case of authentically established background organic pathology of the cardiovascular system, which not only acts as a provoker of the impulse blockade on the bundles of the Hisnus, but also significantly influences the prognosis and outcome of the disease.
Such pathologies as acute coronary syndrome, transmural myocardial infarction, pulmonary embolism and hypertensive crisis with concomitant signs of blockade of the bundle's legs are justification for inpatient hospitalization for qualitative diagnosis and the appointment of an adequate treatment regimen.
In a situation where the blockade of the bundle of the bundle arises against the background of high blood pressure, the use of antihypertensive agents of combined action is recommended to reduce the load on the myocardium (Kaptopres at a dose of 25 mg once and the subsequent transition to a maintenance dosage of 12.5 mg in the morning on a daily basis).
As a prophylaxis for further organic damage to the myocardium, as well as to improve the function of cardiac muscle conduction in patients with blockade of the atrioventricular bundle of the gypsum, it is advisable to use a course of drugs that improve metabolic processes in the myocardium (Mildronate in a daily dose of 0.5 g, Riboxin 200 mg 3 times a day, Trimetazidine in a daily dose of 40 g), lasting at least 1.5 months.
The appointment of drug treatment is possible only with the exclusion of the onset of blockade of the legs of the bundle of His on the background of taking medicines (the so-called "dosage form" of the blockade).
No less effective in this situation are traditional medicine products that have a cardioprotective and calming effect (alcohol tincture of hawthorn and May lily of the valley flowers in 10 drops in the morning).
The surgical method of treatment of bundle branch blockade is applied only in the case of malignant progressive course with frequent Morgane-Adams-Stokes attacks and the risk of full atrioventricular blockade and implicates the pacemaker as an artificial heart rate generator.