bundle branch block
bundle branch block - it is the failure of heart activity due to partial or complete lack of momentum transfer by conduction paths atrioventricular bundle provoking delay excitation ventricular myocardiumand is accompanied by changes in the electrocardiographic pattern.
The structure of cardiovascular diseases associated with disorders of cardiac activity, the share of bundle branch block falls to 2.5% of cases, among which a large proportion of the blockade of the front upper branch of the left bundle branch block.Localization of this branch in the projection of the ring of the aortic valve contributes to the development of the blockade, as a result of constant exposure to high pressure in the ventricles, as well as the pathology of the aortic valve.
The second highest incidence is right bundle branch block, which has no connection with any other cardiac pathology.Blockade rear branching left bundle branch block is rare, as an isolated pathology, due to the fact that
1. The blockade in the projection of the beam:
* disruption of electrical impulse on the anterior branch of the left leg atrioventricular bundle;
* Lock momentum transfer of the posterior branch of the left leg atrioventricular bundle;
* dysfunction of conduction fibers Right bundle branch block.
2. Blockade of the two beams:
* Combined blockade (front upper arm left leg and right bundle branch block);
* gemiblokada (rear lower branch of the left leg and right bundle branch block).
3. Blockade of the three beams.
reasons bundle branch block
blockade in the conduction system atrioventricular bundle may occur on the background of well-being in healthy people (right bundle branch block) or be the result of an organic lesion of a heart attack.In some cases, atrioventricular block is a random finding in the ECG recording and becomes a cause for the impact assessment of the patient for the presence of cardiac disease.
As a rule, the violation of an electrical pulse caused by the presence in the chamber of the heart muscle is not the typical structure (necrosis, sclerosis, myocardial defect), so in most cases resistant complete bundle branch block are the result of organic disease of the heart muscle.
Among cardiac causes bundle branch block leading position occupied by frequency of occurrence: hypertension with a penchant for crisis course, acute coronary insufficiency and transmurralny myocardial infarction, hypertrophic cardiomyopathy and dilatation form, as well as the use of surgical treatment of heart disease.
authentically proved the dependence of occurrence of two-stream blockages and the availability of patient pathology of the aortic valve (aortic congenital malformations) and coarctation of the aorta.
Equally important in the emergence of a blockade state electrolyte balance in the body.So, hyperkalemia, and hypercalcemia with concomitant reduction in sodium levels in the blood may be an agent provocateur of any form of cardiac arrhythmias, including bundle-branch block.
There is a separate type of blockade legs atrioventricular bundle of iatrogenic origin (appearance of symptoms after application of the blockade of certain groups of medicines - anti-arrhythmic, diuretics and cardiac glycosides).
main pathogenetic mechanisms of disorders of impulse conduction pathways of bundle branch block is the occurrence of focal lesions in the organic result of compression due to edema, necrosis, followed by sclerosis, changes in excitability and the duration of the refractory period, decrease the potential of the membrane.
Blockade fiber conduction system bundle branch block are not accompanied by serious violations of rhythm and discomfort the patient, due to the fact that the legs of the atrioventricular bundle are the pacemakers of the fourth order, that is, they are able to generate a maximum of 30 pulses per minute, as opposed tofrom the sinoatrial node, generating 80 pulses for 1 minute.When blocking a particular branch atrioventricular beam pulses start to be generated and distributed by the Purkinje fibers pathways with slow rate of up to 20 pulses per minute.These circumstances do not threaten the patient's life, but the long course of the disease provokes irreversible changes in the brain caused by disturbance of blood supply to the brain structures.
Symptoms bundle branch block
Adrift disease are three forms of blockades: persistent, transient (alternate blockade intact intraventricular conduction) and alternating (determined by ECG changes blockade of one or the second leg).
This form of cardiac arrhythmia refers to the category of intraventricular blocks, so not accompanied by gross violations of rhythm and heart rate.Patients suffering from the blockade legs atrioventricular bundle, basically impose nonspecific complaints, do not allow the initial evaluation of the patient's right to put a preliminary diagnosis: dizziness and transient impairment of consciousness, a feeling of shortness of breath, decreased performance and fatigue.
If the patient appears left bundle branch block, which develops against the background of cardiovascular disease, patients complain characteristic for different clinical entities (kardialgiya or typical angina, heart failure symptoms).At a percussion of the heart in such a situation is determined by the expansion of cardiac dullness, auscultation and signs of the blockade is the splitting of II tone on the apex of the heart, having dependence on the respiratory phases.
Laboratory tests of blood and urine are not detected any change, only a survey to determine the hormonal nature of noncardiac origin bundle-branch block.
mandatory instrumental studies of the patient with suspected intraventricular blockade is the Holter ECG monitoring.This method can not only detect ECG changes characteristic of some form of bundle-branch block, but also to record clinical symptoms that occur in the patient at the time of the attack the blockade.Prerequisite properly conducted Holter monitoring is the continuous observation of the patient with their own feelings and registration of all changes and the time of their occurrence.Keeping such a diary, in some cases to determine the cause of the blockade, the removal of which prevents the development of cardiac rhythm disorders.
In a situation, when ECG can not detect significant symptoms blockade the atrioventricular bundle, the patient is shown holding a transesophageal electrophysiological study, to evaluate the state of the conduction system of the heart.
Despite the absence of clinical symptoms, bundle branch block are not always favorable current situation and existing chronic heart disease can be fatal.
Consequences bundle branch block occur in complete blockade and characterized by the development of seizures of Morgagni-Adams-Stokes.In order to prevent this life-threatening and the patient's health status of the patient is recommended to work pacemaker implantation.
right bundle branch block
In general morbidity bundle branch block at a fraction of the blockade of the right leg falls to 4.5%, of which most of the patients are men older age group, suffering from coronary heart disease and acute coronary episodesfailure.
congenital etiologic factors in the occurrence of blockade of the right leg atrioventricular bundle are anomalies of shells fiber bundle branch block, as well as a violation of the normal position of the vessels.Purchase of risk factors for chronic diseases of the heart, accompanied by organic pathology infarction (ischemic heart disease, hypertensive heart disease with frequent crises, acute myocardial infarction and myocardial infarction).
Clinical manifestations of the blockade of the right leg atrioventricular bundle are non-specific and is increasingly characterized by the basic cardiac pathology, which trigger the development of the blockade.At the initial examination of the patient in favor of the right bundle branch block indicates cleavage II tone at all points of auscultation due to asynchronous ventricular contractions, and by closing non-simultaneous aortic and pulmonary valves.Besides splitting II tone celebrated its strengthening during inspiration, because in this period there is a physiological slowing closing the valves of the pulmonary valve.
In determining the tactics of treatment of the patient with the blockade of the right leg atrioventricular bundle should be based on the presence or absence of acute cardiac pathology.Thus, the blockade, developed against acute myocardial infarction, it is obligatory to emergency hospitalization of the patient in a hospital cardiology.If the right bundle branch block occurred in a perfectly healthy young man, this state does not require medical treatment, as rarely provokes complications and has a favorable outlook for the patient's life.
In any situation, even if the existing concomitant cardiac disease, the prognosis for the patient's life to the blockade of the right leg more favorable than the left leg atrioventricular bundle, since this blockade virtually never transformed into a complete atrioventricular block.
left bundle branch block
risk for the disease left bundle branch block are elderly women in the age group 50-70 years, long-term hypertensive heart disease.At a young age in healthy people, this form of arrhythmia is practically nonexistent.
objective examination of patients with left bundle branch block in 90% of cases, followed by auscultation extension of the first tone in combination with split-second tone caused by uncoordinated contraction of the ventricles, uneven by closing the aortic and pulmonary valves increases during exhalation.
blockade of the electrical impulse through the front left leg branching atrioventricular bundle arises and progresses in cases involving an increase in the thickness of the myocardium in the projection of the left ventricle (ventricular septal pathology, myocardial infarction, myocarditis infectious origin, congenital and acquired aortic valve).As a result of the blockade of impulse is not transmitted to the side wall, and apply the "bottom-up".Thus, the first is excited posterior wall of the left ventricle, and the side and front walls are excited with delay.
blockade of the left leg atrioventricular bundle is the main provocateur occurrence of complete AV block, ventricular tachycardia and forms ventricular fibrillation, which in 70% of cases are fatal, so this dysrhythmia is hazardous to the patient's life.
incomplete bundle branch block
order to assess the mechanism of incomplete bundle branch block should be considered especially cardiac conduction system.Atrioventricular beam has a wide size, so there may be a violation of the conductivity only in a part of the fibers belonging to the right or left bundle branch block, and in such a situation by electrocardiography revealed signs of incomplete intraventricular blockade.
characteristic difference between an incomplete right bundle branch block of the total, is the splitting of the QRS complex in leads V1-2 in the absence of express extension of the ventricular complex.
left leg atrioventricular bundle has two branches, in this connection, a partial blockage of leg meant a violation of the promotion of the electric pulse on one of the branches.In order to determine which branch of the left bundle branch block is locked, it is necessary to evaluate the presence of axis deviation on ECG in standard lead II (expressed levocardiogram indicates blockade of the anterior branch and axis deviation to the right favors the posterior branch of the blockade).
clinical manifestations of an incomplete bundle branch block is minimal and an objective examination of the patient is not determined by auscultation changes.
complete bundle branch block
As a result, a complete right bundle branch block interfere with the normal systolic ventricular excitation.So, with the excitement of the interventricular septum is transmitted only on the heart muscle of the left ventricle and the right ventricle to the excitement is transmitted with a delay, as the momentum transfer in this case the other pathways (Purkinje fibers).
Such abnormal excitation of the right ventricular electrocardiographic reflected in an extension of the ventricular complex in leads V1-2 in the largest intact teeth S, which reflects the state of excitation of the left ventricle.The delay of transmission pulse to the right ventricle also has reflected in the ECG as negativatsii T wave in the right precordial leads.
main distinguishing criterion of complete right bundle branch block is an increase in the summation of the ventricular QRS complex in II standard lead, the value of which amounts to more than 0.12 seconds.
Pathogenesis occurrence complete left bundle branch block is similar, that is, the excitement of the interventricular septum reaches only the right ventricle, which through a network of Purkinje fibers electrical impulse is transmitted to the heart muscle of the left ventricle of the heart.
In this situation, all the electrocardiographic changes are recorded in the left chest leads (extension summation of the QRS complex in the second standard lead, discordant segment depression ST).
bundle branch block on the ECG
Often ECG diagnosis is the only effective method of instrumental examination, allowing even for the primary treatment of the patient to conclude that the presence of bundle branch block.There are signs of change as common ECG pattern and specific for each form of the blockade.The prerequisites decryption registration electrocardiography is to evaluate the width and shape of the QRS in all leads, and the definition of chest leads in which QRS complex is splitting.
Signs of blockade of the upper branch of the left leg atrioventricular bundle are:
- criteria for the left axis deviation is not less than 45%;
- extension of the QRS complex with about 0,9-0,11;
- the presence of specific ventricular complexes of type qR, rS / r in the standard leads;
- in the chest leads decreases the amplitude of the R and the depth increases S.
back to blockade the lower branch of the left bundle branch block characterized by the following ECG signs of impulse conduction:
- increased R-wave amplitude in lead III in comparison with lead II thattestifies about the dramatic axis deviation greater than 90%;
- a slight expansion of the complex QRS (less than 0.11 sec);
- the width of the Q wave in leads III and aVF less than 0.04 s;