Intraatrial block

Intraatrial block is in violation of the passage of excitation in the atria, is observed for large morphological changes of atrial myocardium and often precedes the appearance of atrial fibrillation. Intraatrial block can be incomplete or complete.
In rare cases, full intraatrial block there are two sources of rhythm in the atria, completely independent of one another.
The clinical picture depends on the state of blood circulation. Characteristic clinical signs, except for ECG, no. With incomplete intraatrial block P wave broadened, split or forked, sometimes into two phases (Fig. 22). At full intraatrial block, there are two different forms of P wave with independent timing. In this case, the ventricular can be associated with either one of these sources of rhythm, or alternately with both.

Fig. 22. Intraatrial block (ECG standard thoracic and unipolar limb leads).

The diagnosis is made solely on the basis of electrocardiographic study.
Treatment and ability to work are determined by the state of ventricular myocardium.
Atrio-ventricular blockade — violation of the passage of excitation between the atria and ventricles — may be incomplete or complete. Atrioventricular block is a consequence resulting from the infection, intoxication or disorders of the coronary circulation defeat conductive path connecting the atria and ventricles (atrio-ventricular node, or bundle branch block).

Fig. 23. Incomplete atrio-ventricular block — the first form.

Fig. 24. Incomplete atrio-ventricular blockade — The second form.

Fig. 25. Incomplete atrio-ventricular blockade — the third form.

1. Incomplete atrio-ventricular block is manifested in three ways. First, the most common form is an increase in the interval between the atria and ventricles (Fig. 23). Increase atrioventricular interval thus can reach a considerable size. The second form is the Wenckebach periods — Samoilov — a gradual increase in the atrioventricular interval, when the increase reaches a certain value, reduction ventricle falls. Following a blocked ventricular atrioventricular interval is usually normal (Fig. 24). Third, the most rare form is occurring at the time of loss of ventricular rate during normal atrioventricular interval associated reductions (Figure 25). The mechanism of partial atrioventricular block is unclear. Its effect on the blood circulation is negligible.
The clinical picture depends on the disease that caused the blockade, and its shape. Complaints of the patients are not typical. The first form of the blockade often auscultated gallop rhythm (atrial form) Due to an increase in the interval between the atrial and ventricular parts of the first tone.
In the second and third forms of the blockade can fall during ventricular contraction mark on the jugular vein wave and listening to catch the tone deaf atrial caused by blocked atrial contraction.
On the ECG at the first interval of the form P Q increased (Fig. 23). In the second form, a gradual increase in the interval P — Q with the fallout of a ventricular complex after a certain number of cuts (Fig. 24). In the third form of hair loss occurs from time to time some of ventricular contractions, the interval P — Q with associated reductions in normal (Fig. 25).
The diagnosis can sometimes be determined on the basis of auscultation and confirmed by electrocardiography.
2. Complete atrioventricular block is characterized by independent atrial and ventricular rhythm is manifested in two forms: myogenic (most common), caused morphological changes of the atrioventricular conduction system, and neurogenic (much rarer), caused by a lesion of wiring system and a sharp impact on the heart of the parasympathetic autonomic nervous system.
When myogenic form of complete closure of atrial contractions normal number, the intervals between them are equal. Reduced the number of ventricular contractions, sometimes up to 5-8 in 1 min., Depending on the location of automatic pulse in atrioventricular conduction system. When neurogenic form of blockade independent right ventricular rhythm is missing, but there was a temporary occurring more or less prolonged ventricular termination. Sometimes appear in the form of neurogenic blockade automatic ventricular follow one another with the wrong intervals.
Complete atrio-ventricular block may be associated with incomplete (with one form blockade may be transferred to another) and sometimes with beats, with atrial fibrillation and atrial flutter. When complete atrioventricular block is broken very important for the body's regulation of heart rate extracardiac nerves.
The clinical picture is largely determined by the disease, contributing to the blockade, and blood circulation. In good condition and sufficient infarction ventricular rate (at least 36 to 1 min.) Patients are usually no complaints. Characteristic of complete atrioventricular block is slowing pulse. On examination, it may be noted rhythmic ruffling neck veins, which continued during the pulse pauses. When the atrial and ventricular contractions are the same, ruffling increases sharply. When listening you can set varying amounts of the first tone, the sonority of his times dramatically enhanced ("gun-tone" on Strazhesko). The maximum intensity of the first tone occurs when the atrial reduction a very short period of time precedes ventricular contraction.
ECG on myogenic form blockade independent atrial rhythm is expressed in the regular alternation of atrial P wave, independent of ventricular rhythm — alternating ventricular complexes (QRST). Sometimes, atrial and ventricular complexes superimposed on one another (Fig. 26 and 27). Form of ventricular complex with atrioventricular block depends on the starting point of automatic ventricular pulse.

Fig. 26. Complete atrio-ventricular blockade. Independent rhythm of the atria and ventricles. SFG carotid artery.

Fig. 27. Complete atrio-ventricular block. Independent rhythm of the atria and ventricles. On phonocardiogram — "gun tone."

Fig. 28. Complete atrio-ventricular block. Contract only atrial ventricular contractions are absent.

When neurogenic form blockades sometimes observed following one after the other with not quite regular intervals P wave in the absence of ventricular complexes (Fig. 28). PCG can be noted on the alternation of independent atrial part of the first tone (fourth atrial tone) and ventricular part, the amplitude of the oscillations of the first tone. Arterial and venous pressure is usually not changed. Complete cessation or significant reduction in ventricular rate may lead to cerebral blood flow and cause Adams — Stokes — Morgagni syndrome (see).
Diagnosis can be made on the basis of auscultation. With blockade, in contrast to sinus bradycardia, the strength of the first tone varies. Accurate diagnosis can be made only on the basis of electrocardiography. Ability to work on the state of the contractile myocardium, size and localization of the source that caused the blockage, and the ventricular rate. When unaffected contractile myocardium and adequate ventricular rate in patients may be a long time to do the work, even associated with moderate physical exertion.
Treatment with myogenic form blockade reduced to the effects of the process that caused the break pulse storage. Bring an end to the blockade is rarely possible. Increased frequency of ventricular rate may accelerate with atropine.
With sharp slowing of the heart and inclinations to the syndrome Adams — Stokes — Morganite use special devices — electrostimulators that give the opportunity to bring heart rate to 60-80 in 1 min.

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