Blockade of cardiac conduction system

One of the unique properties of cardiac muscle — the ability to conduct nerve impulses from the sinus node (the main pacemaker) to the Purkinje fibers located in the interventricular septum towards the apex.

Due to this possibility are ongoing concerted reduction of the Atria and ventricles. Excitatory pathways may occur partial or complete obstacles. Such violations are called heart block.

The change of rhythm depends on the location of the site with inhibit impulse conduction. The examination of healthy people showed that the heart block may be functional, do not have to have a strong anatomic pathology.

Clinical manifestations are accompanied by only severe degrees of conduction disorders. In most cases, the signs are detected on the electrocardiogram (ECG).

The types of closures and their characteristics

In relation to the site of injury distinguish the blockade:

• sinoaurikuliarnaya,
• atrial,
• atrioventricular (AV),
• intraventricular.

The most common atrioventricular blockade and conduction disturbance in separate legs of bundle branch block (two bundles of fiber that disintegrates within the ventricular conducting system).

Sinoaurikuliarnaya blockade

Under sinoaurikuliarnaya blockade refers to a disorder of the rhythm, triggered by complete reduction of the whole heart. The pause is almost double the interval between successive cuts. Such loss may occur accidentally or with consistent frequency.

The pulse of the patient is characterized by "loss" the next shock wave. Physical exertion in some cases eliminates the blockade, the same is observed after the introduction of atropinopodobnami drugs.

For the doctor it is important to distinguish sinoaurikuliarnaya blockade of respiratory arrhythmia. With a deep breath in the face of delays the rhythm slows down. And the unit of conductivity does not affect the frequency.

The ECG examination revealed loss rate and pause equal to two cardiac cycles.

Extent of violations of AV-blockade

On ECG characteristics and clinical course to distinguish between 3 degrees of disturbed conduction in the atrioventricular blockade.

First degree only reflects the slow conduction of excitation in the atrioventricular bundle. This means that the time from atrial to ventricular increase from normal 0,15–0,18 sec. to 0.2 sec. On the ECG, respectively Dlinnaya interval PQ.

Conduction of the 1st degree is often observed in the midst of acute rheumatic fever. After the treatment it disappears. Persistent changes occur in:

• postmyocardial cardiosclerosis;
• atherosclerotic lesionscoronary arteries, especially branches of the right coronary artery);
• slow sepsis;
• syphilitic myocarditis.

When examining the role of the vagus nerve is set to the left barrel, Innervate a large part of bundle branch block.

Second degree atrioventricular heart block is progressive deterioration of conductivity and the depletion of the system. On ECG appear periods Samoylov-Wenckebach — one loss reduction. This may be every third, fourth or fifth systole of the ventricles.

Accordingly, the patient feels a change in the strength of the pulse impact. The clinical manifestations need to look carefully at the pulsation of the cervical vessels. Heart auscultation the doctor may need to keep both hand on the pulse, then you can feel the loss reduction without ECG.

Another described Wenckebach type is characterized by the loss of individual contractions of the ventricles while maintaining the interval PQ. This confirms incomplete atrioventricular blockade with a ratio of atrial and ventricular contractions to 2:1, 3:1 or 4:1.

The third degree is known as complete transverse blockade. It is detected by different statistical research ranges from 0.53 to 0.8% of all electrocardiography.

The causes and mechanism of development of AV-blockade

The main cause is atherosclerosis (in 50-70% of cases). Conduction is disturbed because of the low patency of the coronary vessels that feed the cells. About 5% of cases are caused by rheumatic inflammation diphtheria. Much less the blockade of the left ventricle accompanies myocardial infarction posterior wall, scarlet fever and other infections.

With the full blockade of bundle branch block loses its conductive ability. Impulses causing contraction of the ventricles, occur below the injury site. In the result, the Atria continue to receive impulses from the sinus node and decrease in the normal rhythm (60-80 beats per minute), while the ventricles are "Yes" other instructions and work slowly, regardless of the Atria.

It is proved that in the atrioventricular node, the frequency of 50 pulses per minute. If the focus is located above the dividing the total beam on the right and left legs, bradycardia reaches 25-20 per minute.