AV blockade

Description:

Atrioventricular (AV) blockade is a disturbance of transfer of nervous impulse in the carrying-out system of heart.
There is a cross blockade of which the conductivity disturbance caused by defeat of a node of Ashof — Tavar and the general part of a ventriculonector and longitudinal blockade with disturbance of conductivity of one of ventriculonector legs is characteristic.
Depending on weight AV-blockade can be the 1st, 2nd and 3rd degree (full).

AV-blockade of the 1st degree is a lengthening of an interval of PQ more than 0,20 pages. It is found in 0,5% of young people without symptoms of a heart disease. At elderly AV-blockade of the 1st degree most often happens a consequence of the isolated disease of the carrying-out system, for example at Lenegr's disease.

At AV-blockade of the 2nd degree a part of atrial impulses does not reach ventricles. Blockade can develop at the level of the AV-node and Gis's system — Purkinye.

Expressiveness of AV-blockade can be characterized a ratio of number of teeth P and the QRS complexes. So, if only every third impulse is carried out, speak about
To AV-blockade of the 2nd degree with carrying out 3:1.

    * If at AV-blockade (for example, with carrying out 4:3 or 3:2) intervals of PQ are not identical and Venkebakh's periodical press is observed, speak about AV-blockade of the 2nd degree like Mobitts I.

    * At AV-blockade of the 2nd degree like Mobitts I the QRS complexes usually narrow as blockade happens above a ventriculonector at the level of the AV-node.

    * Even if at AV-blockade like Mobitts I blockade of a leg of a ventriculonector is noted, AV-blockade level, most likely, is at the level of the AV-node. Nevertheless in this case the elektrogramma of a ventriculonector is necessary for confirmation of level of blockade.

Far come AV-blockade (3:1, 4:1 and above) belongs to AV-blockade of the 2nd degree like Mobitts II. The QRS complexes at the same time usually wide (blockade of the right or left leg of a ventriculonector is characteristic), and the level of blockade is below the AV-node. AV-blockade like Mobitts II usually happens at the level of Gis's system — Purkinye or below it. It often turns into full AV-blockade.

At AV-blockade 2:1 it is impossible to define its type (Mobitts I or Mobitts II).

AV-blockade of the 3rd degree, or full AV-blockade, shares on acquired and inborn.

From inborn total  atrioventricular block women – about 60% of the revealed cases suffer more. Mothers of children with inborn AV-blockade in 30 — 50% of cases suffer from collagenoses, most often a system lupus erythematosus.

The acquired full AV-blockade usually develops at the age of 60 — 70 years, is more often at men.

AV blockade reasons:

The most frequent origin of an atrioventricular block is the isolated disease of the carrying-out system (Lenegr's disease). Besides, AV-blockade can arise at a myocardial infarction, usually in the first 24 h. It arises at patients with the lower myocardial infarction and at 2% of patients with a front heart attack.

Medicines against the background of which reception the risk of development of an atrioventricular block is increased:

    * Some antagonists of calcium
    * Beta adrenoblockers
    * Digoxin
    * Antiarrhytmic means with hinidinopodobny action

Coronary heart disease:

    * Myocardial infarction
    * Myocardium ischemia

The isolated disease of the carrying-out system of heart:

    * Lenegr's disease
    * Disease Leva

Inborn heart diseases:

    * Inborn full AV-blockade (it is diagnosed most often at a system lupus erythematosus for mother)
    * Defect of an interatrial partition like ostium primum
    * Transpositions of the main arteries

Quite often disturbance of conductivity meets at calcification of valve rings and various genesis cardiomyopathies, collagenoses (a system scleroderma, a pseudorheumatism, a syndrome of Reuters, a system lupus erythematosus, an ankylosing spondylitis, a polymiositis).

Infiltrative diseases of a myocardium:

    * Amyloidosis
    * Sarcoidosis
    * Hemochromatosis

Inflammatory diseases:

    * Infectious endocarditis
    * Myocarditis (Chagas's disease, laymsky disease, rheumatism, tuberculosis, measles, epidemic parotitis)

Metabolic disturbances:

    * Hyperpotassemia
    * Gipermagniyemiya

Endocrine diseases:

    * Primary adrenal insufficiency

Damage of the AV-node:

    * Heart operations
    * Radiation of a mediastinum
    * Heart catheterization
    * Catheter destruction

Tumors:

    * Mesothelioma
    * Lymphogranulomatosis
    * Melanoma
    * Rhabdomyosarcoma

Neurogenic reasons:

    * Carotid sinus syndrome
    * Vazovagalny reactions

Neuromuscular diseases:

    * Atrophic myatonia and others.

AV blockade symptoms:

The clinical picture of an atrioventricular block depends on degree of its expressiveness.
AV-blockade of the 1st degree usually proceeds asymptomatically.

AV-blockade of the 2nd degree if it is only not far come AV-blockade, seldom causes complaints, however it can turn into full AV-blockade.

Full AV-blockade can be shown by weakness or faints — everything depends on the frequency of the replacing rhythm.

Heart rate is changeable as reductions of auricles get on different phases of work of ventricles.

Periodic change of amplitude of pulse wave is characteristic of AV-blockade of the 2nd degree. At full AV-blockade filling of arterial pulse changes chaotically. Besides, at full AV-blockade high ("gun") waves And pulse of jugular veins are noted (they arise when reduction of auricles happens at the closed AV-valves).

The loudness of cardiac sounds changes because of the changing filling of ventricles too.

    * When lengthening an interval of PQ I the cardiac sound becomes more silent therefore silent I tone is characteristic of AV-blockade of the 1st degree, at AV-blockade of the 2nd degree like Mobitts I the loudness of the I tone decreases from a cycle to a cycle, and at full AV-blockade it different all the time.

    * At full AV-blockade there can be a functional mesosystolic noise.

AV blockade treatment:

Medical tactics at an atrioventricular block also depends on its type and degree of manifestation. At AV-blockade of the 1st degree and the 2nd degree like Mobitts I treatment is not required. At AV-blockade of the 2nd degree like Mobitts II and full AV-blockade the constant EX-is usually shown.

Drug treatment is used only waiting for EX-, as an independent measure it is not applied.

The main drug which is used before EX-— atropine.

    * Atropine can reduce AV-blockade if it is caused by increase in a parasympathetic tone, but not ischemia.

    * Atropine is more effective at AV-blockade against the background of lower, than against the background of a front myocardial infarction.

    * Atropine does not influence conductivity in Gis's system — Purkinye and therefore is inefficient at full AV-blockade, and also at AV-blockade of the 2nd degree caused by blockade at the level of Gis's system — Purkinye.

    * Atropine does not influence the replaced heart.

    * At AV-blockade of the 2nd degree like Mobitts II atropine should be used with care as it can reduce the frequency of reduction of ventricles. So, AV-blockade with carrying out 2:1 with an atrial frequency of 80 beats per minute can turn into AV-blockade 3:1 with an atrial frequency of 90 beats per minute therefore the frequency of reduction of ventricles will fall from 40 to 30 beats per minute.

Anti-digoxin (Fab-fragments of antibodies to digoxin) is used at hemodynamically significant AV-blockade caused by digoxin. The dose is calculated so:

Quantity of bottles = Weight (kg) × Serumal concentration of digoxin (ng/ml): 100

Rolled into one 38 mg of anti-digoxin contain. Contents of one bottle connect 0,6 mg of digoxin.