Atrioventricular (predserdno-ventricular) blockade (AV-blockade) – the conductivity malfunction which is expressed in delay or the termination of passing of an electric impulse between auricles and ventricles and leading to frustration of a warm rhythm and haemo dynamics. AV-blockade can proceed asymptomatically or be followed by bradycardia, weakness, dizziness, attacks of stenocardia and loss of consciousness. Atrioventricular blockade is confirmed by means of an electrocardiography, holterovsky ECG monitoring, EFI. Treatment of atrioventricular blockade can be medicamentous or cardiac (implantation of an electropacemaker).
Atrioventricular blockade delay or complete cessation of passing of an impulse from auricles to ventricles owing to defeat actually is the cornerstone of AV-knot, Gis's bunch or legs of a bunch of Gis. At the same time, the defeat level is lower, the it is heavier than manifestation of blockade and the forecast is more unsatisfactory. Prevalence of atrioventricular blockade is higher among the patients having the accompanying cardiopathology. With heart diseases AV-blockade of the I degree occurs among persons in 5% of cases, the II degrees – in 2% of cases, the III extent of AV-blockade usually develops at patients 70 years are more senior. Sudden warm death, statistically, comes at 17% of patients with full AV-blockade.
The atrioventricular knot (AV-knot) is a part of the carrying-out system of heart providing consecutive reduction of auricles and ventricles. The movement of the electric impulses arriving from sinusovy knot is slowed down in AV-knot, providing a possibility of reduction of auricles and forcing of blood in ventricles. After a small delay impulses extend on Gis's bunch and his legs to the right and left ventricle, promoting their excitement and reduction. This mechanism provides serial reduction of a myocardium of auricles and ventricles and supports stable haemo dynamics.
Classification of AV-blockade
Depending on the level at which violation of carrying out an electric impulse develops allocate the proximal, disteel and combined atrioventricular blockade. At proximal AV-blockade carrying out an impulse can be broken at the level of auricles, AV-knot, a trunk of a bunch of Gis; at disteel – at the level of branches of a bunch of Gis; at combined – raznourovnevy violations of conductivity are observed.
Taking into account duration of development of atrioventricular blockade allocate its sharp (at a myocardial infarction, overdose of medicines etc.), intermittiruyushchy (alternating – at IBS which is followed by passing coronary insufficiency) and chronic forms. By electrocardiographic criteria (delay, frequency or total absence of carrying out an impulse to ventricles) three extents of atrioventricular blockade distinguish:
- The I degree – atrioventricular conductivity through AV-knot is slowed down, however all impulses from auricles reach ventricles. Clinically it is not distinguished; on the ECG the interval of P-Q is extended> 0,20 seconds.
- The II degree – incomplete atrioventriulyarny blockade; not all predserdny impulses reach ventricles. On the ECG - periodic loss of ventricular complexes. Allocate three types of AV-blockade of the II degree on Mobittsa:
- Mobitts type I – the delay of each subsequent impulse in AV-knot leads to a full delay of one of them and loss of a ventricular complex (Samoylov's period – Venkebakh).
- Mobitts type II – a critical delay of an impulse develops suddenly, without the previous lengthening of the period of a delay. At the same time lack of carrying out every second (2:1) or the third (3:1) impulse is noted.
- The III degree - (total atrioventricular block) – complete cessation of passing of impulses from auricles to ventricles. Auricles are reduced under the influence of sinusovy knot, ventricles - in own rhythm, 40 times in min. are more rare that it is not enough for ensuring adequate blood circulation.
Atrioventricular blockade of I and II degrees are partial (incomplete), blockade of the III degree – full.
Reasons of development of AV-blockade
On an etiology functional and organic atrioventricular blockade differ. Functional AV-blockade are caused by increase in a tone of a parasympathetic part of the nervous system. Atrioventricular blockade of I and II degrees in isolated cases is observed at young physically healthy faces, the trained athletes, pilots. Usually it develops in a dream and disappears during physical activity that is explained by hyperactivity of the wandering nerve and is considered as norm option.
AV-blockade of organic (kardialny) genesis develop as a result of idiopathic fibrosis and a sclerosis of the carrying-out system of heart at his various diseases. As the reasons of kardialny AV-blockade rheumatic processes can serve in a myocardium, a cardiosclerosis, syphilitic damage of heart, a heart attack of an interventricular partition, heart diseases, a cardiomyopathy, a miksedem, diffusion diseases of connecting fabric, myocardites of various genesis (autoimmune, diphtheritic, tireotoksichesky), , , hemochromatosis, heart tumors, etc. At kardialny AV-blockade partial blockade can be observed in the beginning, however, in process of progressing of cardiopathology, blockade of the III degree develops.
Can lead various surgical procedures to development of atrioventricular blockade: prosthetics of the aortal valve, plasticity of congenital heart diseases, atrioventricular RChA of heart, kateterization of the right departments of heart and so forth.
Quite seldom in cardiology the congenital form of predserdno-ventricular blockade (1:20 000 newborns) meets. In case of congenital AV-blockade lack of sites of the carrying-out system (between auricles and AV-knot, between AV-knot and ventricles or both legs of a bunch of Gis) with development of appropriate level of blockade is observed. At a quarter of newborns atrioventricular blockade is combined with other warm anomalies of congenital character.
Intoxication medicines quite often occurs among the reasons of development of atrioventricular blockade: warm glycosides (digitalisy), β-blockers, blockers of calcic channels (verapamil, diltiazemy, is more rare - korinfary), antiaritmika (hinidiny), lithium salts, some other medicines and their combinations.
Symptoms of AV-blockade
The nature of clinical manifestations of atrioventricular blockade depends on the level of violation of conductivity, extent of blockade, an etiology and weight of an associated disease of heart. The blockade which developed at the level of atrioventricular knot and not causing bradycardia clinically do not prove in any way. The clinic of AV-blockade at this topography of violations develops in cases of the expressed bradycardia. Because of small ChSS and falling of minute emission of blood by heart in the conditions of physical activity at such patients weakness, short wind, sometimes – stenocardia attacks are noted. Because of decrease in a cerebral blood-groove dizziness, passing feelings of confusion of consciousness and faints can be observed.
At atrioventricular blockade of the II degree patients feel loss of a pulse wave as interruptions in area of heart. At AV-blockade of the III type there are Morganyi-Adams-Stokes's attacks: the pulse urezheniye to 40 and less beats per minute, dizziness, weakness, darkening in eyes, short-term loss of consciousness, pain in heart, cyanosis of the person, is possible - spasms. Congenital AV-blockade at patients of children's and youthful age can proceed asymptomatically.
Complications of AV-blockade
Complications at atrioventricular blockade are generally caused by the expressed delay of a rhythm developing against the background of organic damage of heart. Most often the course of AV-blockade is followed by emergence or aggravation of chronic heart failure and development of ektopichesky arrhythmias, including, ventricular tachycardia.
The course of total atrioventricular block can be complicated by development of attacks of Morganyi-Adams-Stokes connected with a brain hypoxia as a result of bradycardia. The feeling of heat in the head, attacks of weakness and dizziness can precede the beginning of an attack; during an attack the patient turns pale, then cyanosis and loss of consciousness develops. At this moment performing indirect massage of heart and IVL as the long asistoliya or accession of ventricular arrhythmias increases probability of sudden warm death can be required by the patient.
Repeated episodes of loss of consciousness at patients of senile age can lead to development or aggravation intellectual violations. Less often at AV-blockade development of aritmogenny cardiogenic shock is possible, is more often at patients with a myocardial infarction.
In the conditions of insufficiency of blood supply at AV-blockade the phenomena of cardiovascular insufficiency (a collapse, faints), an exacerbation of coronary heart disease, diseases of kidneys are sometimes observed.
Diagnostics of AV-blockade
At assessment of the anamnesis of the patient in case of suspicion on atrioventricular blockade find out the fact postponed in the past of a myocardial infarction, myocarditis, other cardiopathologies, reception of the medicines breaking atrioventricular conductivity (a digitalisa, β-blockers, blockers of calcic channels, etc.).
At an auskultation of a warm rhythm the correct rhythm interrupted by the long pauses indicating loss of ventricular reductions, bradycardia, emergence of gun I tone of Strazhesko is listened. Increase in a pulsation of cervical veins in comparison with sleepy and beam arteries is defined.
On the ECG AV-blockade of the I degree is shown by lengthening of an interval of R-Q> 0,20 sec.; The II degrees - a sinusovy rhythm with pauses, as a result of losses of ventricular complexes after a tooth P, emergence of complexes of Samoylov-Venkebakh; The III degrees – reduction of number of ventricular complexes by 2-3 times in comparison with predserdny (from 20 to 50 in a minute).
Carrying out daily monitoring of the ECG on Holtera at AV-blockade allows to compare subjective feelings of the patient with electrocardiographic changes (for example, faints with sharp bradycardia), to estimate degree of bradycardia and blockade, connection with activity of the patient, drug intake, to define existence of indications to implantation of a pacemaker, etc.
By means of carrying out an electrophysiological research of heart (EFI) the topography of AV-blockade is specified and indications to its surgical correction are defined. At existence of the accompanying cardiopathology and for its identification at AV-blockade carry out an echocardiography, by heart MCKT or MPT.
Carrying out additional laboratory researches at AV-blockade is shown in the presence of the accompanying states and diseases (definition in blood of level of electrolytes at a giperkaliyemiya, the maintenance of antiaritmik at their overdose, activity of enzymes at a myocardial infarction).
Treatment of AV-blockade
At atrioventricular blockade of the I degree proceeding without clinical manifestations only dynamic observation is possible. If AV-blockade is caused by reception of medicines (warm glycosides, antiarrhytmic medicines, β-blockers)))))))))), carrying out correction of a dose or their full cancellation is necessary.
At AV-blockade of kardialny genesis (at a myocardial infarction, myocardites, a cardiosclerosis, etc.) it is treated with β-adrenostimulyator (izoprenaliny, ortsiprenaliny), implantation of a pacemaker is shown further.
Medicines of first aid for knocking over of attacks of Morganyi-Adams-Stokes are (sublingual), atropine (intravenously or hypodermically). At the phenomena of stagnant heart failure appoint diuretics, warm glycosides (with care), vazodilatator. As symptomatic therapy at a chronic form of AV-blockade it is carried out lecheniyeteofilliny, belladonna extract, nifedipine.
Radical method of treatment of AV-blockade is installation of the electropacemaker (EX-) restoring a normal rhythm and heart rate. Endokardialny EX-serve as indications to implantation existence in the anamnesis of attacks of Morganyi-Adams-Stokes (even single); frequency of a ventricular rhythm less than 40 in minute and the periods of an asistoliya of 3 and more seconds; AV-blockade of the II degree (the II type on Mobittsa) or the III degrees; the full AV-blockade which is followed by stenocardia, stagnant heart failure, high arterial hypertension etc. Consultation of the heart surgeon is necessary for the solution of a question of operation.
Forecast and prevention of AV-blockade
Influence of the developed atrioventricular blockade on further life and working ability of the patient is defined by a number of factors and, first of all, level and extent of blockade, the main disease. The most serious forecast at the III extent of AV-blockade: patients are disabled, development of heart failure is noted.
Development of disteel AV-blockade because of threat of a total block and a rare ventricular rhythm, and also their emergence against the background of a sharp myocardial infarction complicates the forecast. Early implantation of an electropacemaker allows to increase life expectancy of patients with AV-blockade and to improve quality of their life. Total congenital atrioventricular block predictively is more favorable, than acquired.
As a rule, atrioventricular blockade is caused by the main disease or a pathological state therefore its prevention is elimination of etiologichesky factors (treatment of cardiac pathology, an exception of uncontrolled administration of drugs, the impulses influencing carrying out etc.). For prevention of aggravation of extent of AV-blockade implantation of an electropacemaker is shown.