AV-blockade 1, 2, 3 degrees
One of their vital organs is the heart. Its work is based on alternating contraction (compression) and relaxation of the muscular layer of the Atria and ventricles. The correct rate is provided by a conductive system with two Central nodes: sinus-atrial (sa, SA) and atrioventricular (atrioventricular, AV). Pathological conditions caused by disorders of conduction in the region of the atrioventricular (AV) node, called the AV-blockade.
The concept of atrioventricular block
Both Atria and both ventricles of the heart forces us to decrease the electrical impulse, which occurs in the sinus node. Under the influence of the resulting pulse are reduced atrial. Next, the impulse is conducted to the atrioventricular node, located on the border of the ventricles with the Atria. In this region impulse conduction in a fraction of seconds delayed, allowing blood to pass from the cavities of the Atria in the cavity of the ventricles. Then along the legs of the formation of the conduction system – bundle branch block, the impulse is already in filled with blood the ventricles causes them to contract and push blood into the aorta and blood vessels. The mechanism of AV blockade is in time delay or in complete failure of the impulse through the atrioventricular node.
Are classified as AV-blockade
Atrioventricular block klassificeret on several grounds. At the time of development and duration the following types:
- acute, or transient or transient – occurs against a background of myocardial infarction, ingestion of high doses of cardiac glycosides, as well as various poisonings;
- intermittent, or alternating, or intermittent – occurs on the background of IHD (ischemic heart disease), accompanied by insufficiency of coronary blood supply;
- chronic – characterized by various lesions of the heart.
The level (location of violation) conductivity:
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- proximal – violation in the Atria, in the region of the trunk bundle branch block in the AV node;
- distal – level violations in the area of legs of bunch of gisa;
- combined (mixed) is a condition in which disorders arise at different levels.
There are 3 degrees of severity of the closures: first, second and third. In the case of 1 and 2 degrees talk about incomplete or partial blockade, 3rd degree is a complete AV blockade with severe disorders of the body. The mechanism of blockade by degrees:
- blockade AV degree 1 – the occurrence of conduction disturbances at any level of slowing in the AV node, the conduction of atrial impulses to muscle fibers of the ventricles are stored;
- AV block 2nd degree a deterioration of the conductivity at any level, with block some atrial impulses do not reach the muscular fibres of the ventricles;
- AV block 3rd degree – complete block of the impulse in the area of the AV node, the conduction of impulses to muscle fibers of the ventricles is stopped; the rhythm of the Atria due to the influence of the sinus node and the contraction of muscle fibers of the ventricles occurs in its slow rhythm (40 beats in 1 minute and less).
The clinical manifestations of the second degree may be different and are divided into 2 types:
Depending on the reasons for the blockade may be functional (reversible) or organic (irreversible). Functional not lead to changes in the conduction system of the heart. Such condition is caused by the increasing processes in the parasympathetic division of the autonomic nervous system. Organic blockade due to irreversible changes in the conducting system because of various damaging factors – fibrotic or sclerotic changes, the influence of toxic substances, improper structure of the heart and other causes. Cardiac factors contributing to the development of AV-blockade:
- impaired blood flow to the heart (spasm or blockage of coronary arteries) in coronary artery disease and atherosclerosis;
- acute myocardial infarction, especially with the spread in the interventricular septum;
- heart defects – congenital or acquired;
- postinfarction cardiosclerosis;
- syphilis, spread of damaging process in the myocardium;
- tumor formation of the heart;
- the formation of calcification and fibrosis of unknown etiology in a conductive system;
Different substance by which intoxication may cause AV blocks:
- cardiac glycosides (Strofantin, Digoxin, Korglikon);
- beta-blockers (Bisoprolol, Metoprolol, Propanolol);
- calcium channel blockers (Verapamil, Corinfar, Diltiazem);
- antiarrhythmic agents (Amiodarone, Cordarone, Quinidine);
- lithium salts (Lithium carbonate, Lithium hydroxybutyrate).
Other causes of AV blocks:
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- gipotireoidne syndrome;
- introduction intracardiac catheter;
- the myotonia atopicescie.
The main complaints of patients are disruptions of the heart (arrhythmias), darkening of the eyes, dizziness. May experience presyncopal state and fainting, a sense of fear during the «fading» and «slow» heart, shortness of breath, sharp General weakness.
With 1 degree AV blockade symptoms may be absent in 2 degree type 1 Mobitz it is also possible the absence of symptoms or the presence of infrequent disruptions of cardiac activity. Blockade of the type 2 Malts accompanied by a number of symptoms that occur with paroxysmal. Blockade of 3 degrees is characterized by sudden bradycardia and circulatory disorders. Patients often lose consciousness, falling into a serious condition requiring immediate medical attention. The attack is accompanied by sudden weakness and bradycardia below 40 beats per minute, cyanosis of the face and upper torso, pain in the chest and loss of consciousness with convulsions is called the syndrome of Morgagni-Adams-Stokes.
Treatment of atrioventricular blocks
1 the degree of blockade requires observation of the dynamics of the state without any therapy. If the reason for the blockade is the medication, adjust the dose or cancel. Possible replacement for other drugs. If cardiac causes blockade medical treatment beta-adrenostimulyatorov (Ortsiprenalina, Izoprenalin). If the cause of the blockade is a common disease, it should be treated. In the event of attack Morgagni-Adams-Stokes carry out emergency measures: intravenous or subcutaneous administration of atropine, the hyoid reception Izadrina further hospitalization.
When a full blockade is carried out a temporary stimulation – the introduction of a temporary intracardiac pacemaker through the venous catheter. Often this procedure is preceded by radical treatment – the installation of a permanent intracardiac EX, which normalizes the frequency and rhythm of cardiac contractions, stabilizing the patient and improving his quality of life. The installation of the FORMER is shown in a full blockade, blockade of 2 degrees type, 2 MOBITs with frequent attacks, and after suffering at least one attack Morgagni-Adams-Stokes.