What is an AV blockade? Atrioventricular blockade: causes, symptoms, diagnosis and treatment

Atrioventricular blockade is a physiological impairment of the transmission of nerve impulses through the cardiac conduction system from the ventricles to the atria. Complex at first glance, the name comes from the Latin words atrium and ventriculus, which denote the atrium and ventricle, respectively.

About the heart, its structure and conductive system

The heart of man, like many other living things belonging to mammals, consists of the right and left parts, each of which has an atrium and ventricle. Blood from the entire body, namely from a large circle of blood circulation, first enters the right atrium, and then into the right ventricle, then - through the vessels to the lungs. Enriched with oxygen, blood from the small circle of circulation from the lungs flows into the left atrium, from which it enters the left ventricle, and from it is transferred to the organs and tissues along the aorta.

The current of blood in the heart ensures the functioning of its conducting system. It is thanks to her that the heart beats correctly - a timely contraction of the atria and ventricles and the flow of blood through them. If there is a violation in the transmission of nerve impulses between the atria and the ventricles, the latter contract too slowly or out of time - after a long time after atrial contraction. As a result, the blood flow strength changes, it does not eject it into the blood vessels at the right time, there is a drop in pressure and other serious changes in the cardiovascular system.

Why is the AV blockade dangerous?

The degree of danger of atrioventricular blockage depends on its severity. The mild forms of conduction disturbance can be asymptomatic, the mean - to require clarification of the causes and treatment to prevent heart failure. With complete blockade, instant death may occur from cardiac arrest. That is why the violation of nerve conduction in the heart can not be ignored, even if at the moment there are no serious signs of the disease.

Classification by degree of AV blockade

AV-blockade of the heart can be of several types and subtypes. By severity, the following are distinguished: AV blockade of the first degree, often not accompanied by any external disturbances and in many cases being the norm, a second-degree block, divided into two subtypes: type 1 (Mobits 1, or Wenckebach blockade) and Type 2 (Mobits 2), and blockade of the third degree - a complete stop of the transmission of nerve impulses from the atria to the ventricles.

1st degree of AV blockade

AV blockade 1 degree can be a normal physiological phenomenon for young patients. Often diagnosed and regularly trained athletes, and they are also considered the norm. With such a blockade, a person usually does not have any noticeable symptoms indicating a heart problem. AV-blockade 1 degree in the absence of signs of disease, as a rule, does not require treatment, but it may be necessary in the presence of other abnormalities in the work of the heart. Also in this case, the doctor can be assigned repeated ECG, daily ECG monitoring and additional studies, such as Echocardiography (ultrasound of the heart). In the electrocardiogram, an atrioventricular block of degree 1 is manifested by an increase in the interval between the teeth P and R, while all of the P teeth are normal, and QRS complexes always follow them.

2 nd degree

AV blockade of the 2nd degree happens, as already described above, of the first and second type. In the course of the 1st variant (Mobitz 1), it can be asymptomatic and does not require treatment. In this case, the physiological basis of the occurrence of the block is usually the problem in the atrioventricular node. AV-blockade of the second degree in the Mobits type 2 - usually a consequence of pathology in the lower conducting system (Gisa-Purkinje). As a rule, it proceeds with obvious symptoms and requires additional diagnosis and rapid initiation of treatment to prevent the development of a complete blockade with cardiac arrest.

AB blockades on the ECG (second degree 1 type) are characterized by a progressive increase in the PR interval, after which the QRS complex falls out and then restores a rhythm close to normal. Then everything repeats itself. This periodicity is called the periodical of Samoilov-Wenckebach. The second type of AV blockade with the second degree on the ECG is characterized by the constant or spontaneous precipitation of the QRS complex, while the extension of the PR interval, as in the Mobitz type 1, does not occur.

3rd degree

AV-blockade of the third degree is congenital and acquired. Characterized by the complete absence of pulses passing from the atria to the ventricles, in connection with which is called a complete blockade. Since impulses through the atrioventricular cardiac node are not carried out, for the emergency support of the heart, pacemakers of the second order are activated, i.e. the ventricle works by its own rhythm, not associated with the rhythm of the atrium. All this causes serious violations in the functioning of the heart and the work of the cardiovascular system. Blockade of the third degree requires a rapid onset of treatment, since it can lead to the death of the patient.

On the ECG, a third-degree blockade looks like this: there is no connection between the P-teeth and the QRS complexes. They are recorded at inappropriate times and at different frequencies, ie, two unrelated rhythms are identified, one is atrial, the other ventricular.

The causes of the AV blockade

The most frequent causes of such abnormalities as AV blockade are increased tonus of the vagus nerve in athletes, sclerosis and fibrosis of the conduction system of the heart, the pathology of the heart valves, myocarditis, myocardial infarction, electrolyte disorders and the use of certain drugs, for example cardiac glycosides ("Digoxin" , "Korglikon", "Strofantin"), calcium channel blockers (Amlodipine, Verapamil, Diltiazem, Nifedipine, Cinnarizine), beta blockers (Bisoprolol, Atenolol, Carvedilol, ). A complete blockade can be congenital. This pathology is often recorded in children whose mothers suffer from systemic lupus erythematosus. Another cause of the onset of a third degree block is Lyme disease, or borreliosis.

Symptoms of AV blockade

Atrioventricular blockade of 1 degree, as well as blockade of 2 degrees of the first type, is usually not accompanied by any symptoms. However, in the Moritz 1 blockade, dizziness and fainting are observed in some cases. The second type of the second degree manifests itself by the same signs, as well as by the turbidity of the mind, the pains in the heart and the sensation of its stop, with prolonged syncope. Symptoms of complete atrioventricular blockade are a decrease in the pulse rate, severe weakness, twisting of the head, darkening in the eyes, convulsions, loss of consciousness. There may also come a complete stop of heart activity with a fatal outcome.

Diagnosis of AV blockade

Diagnosis of atrioventricular blockade is carried out by electrocardiography. Often AV-blockade of the 2nd degree (as well as the 1st one) is detected accidentally during an ECG without complaints during the preventive medical examination. In other cases, the diagnosis is performed if there are any symptoms that may be associated with problems in the nervous system that conducts the nervous impulses, for example, with dizziness, weakness, darkening in the eyes, fainting.

If the patient is diagnosed with an EC blockade, and there are indications for further examination, the cardiologist usually recommends a daily ECG monitoring. It is carried out with the help of a Holter monitor, therefore it is also often referred to as Holter monitoring. Within 24 hours there is a constant continuous recording of the ECG, while a person leads a habitual and characteristic way of life - moves, takes food, sleeps. The study is non-invasive and does not cause any discomfort.

After the recording of the electrocardiogram, the data from the monitor is analyzed with the issuance of the corresponding conclusion. The plus of this method of diagnosis, in comparison with the usual short ECG record, is that it is possible to find out with what frequency blockades occur, at what time period of the day they are fixed most often and at what level of activity of the patient.

Treatment

Not always atrioventricular blockade of the first degree, as well as the second, requires medical intervention. With the 1st in medical activities, as a rule, there is no need. Also, with the second in the first type (Moritz 1), therapy is usually not performed, although additional studies to identify concomitant problems with the heart can be recommended.

Treatment of AV blockade is necessary for the second degree of the Moritz type 2, as well as partial or complete blockade of the third degree, since such a significant conduction disorder can lead to sudden death. The main method of correcting the malfunction of the heart is to install the patient an electrocardiostimulator (ECS), temporary or permanent. Also appointed and specific drug therapy - "Atropine" and other drugs. Medicines are not able to cure a person with this disease and are usually used in the period before the implantation of the EKS.

Preparing for the installation of an EX

Preparation for implantation of the pacemaker includes, in addition to electrocardiography, echocardiography - ultrasound examination of the heart. Echocardiography allows you to visualize the wall, cavities and septa of the heart and detect any primary diseases that could be the cause of AV blockade, for example, valve pathology. If a cardiologist with an ultrasound examination has detected heart problems, concomitant therapy is performed in parallel with the treatment of atrioventricular blockade. This is especially important in cases where these pathologies are the cause of the violation of conductivity. Also, standard clinical studies are being performed - blood and urine tests. If the patient has diseases of other organs and systems, in the preoperative period, appropriate diagnostic measures can be recommended to him.

Implantation of EXC

Setting the pacemaker with a diagnosis such as AV blockade is a planned surgical procedure. It can be performed both under general anesthesia and under local anesthesia. The surgeon passes through the subclavian vein along the vessels to conduct electrodes towards the heart, which are fixed there. The device is sewed under the skin by a special technique. The wound is stitched.

EKS is an artificial substitute for the pacemaker, which conducts pulses from the atria to the ventricles and normalizes the heartbeat. Due to periodic or constant stimulation, the chambers contract in the right order and at the right interval, the heart fully fulfills its pump function. There are no stagnation and sudden changes in blood pressure in the circulatory system, and the risk of symptoms such as dizziness, unconsciousness, and others commonly occurring in patients diagnosed with an AV blockade is significantly reduced, as is the risk of sudden death from stopping Cardiac activity.

After operation

The postoperative period, if there are no other health problems that complicate it, usually is not accompanied by any serious limitations. The patient's home is released for 1-7 days, having previously conducted some studies. Care of the wound in the area of the implanted body of the device is carried out according to the recommendations of the doctor. Removal of sutures is necessary if they are stitched with suture material, which does not resolve itself. If the wound is closed with a cosmetic suture during the installation , it is not necessary to remove the wound.

The first weeks after the pacemaker implantation it is recommended to avoid physical activity, and also to save the seam area (sports, if there are no contraindications, you can start several months later, without consulting a doctor). 1 month after the procedure, a cardiologist's control consultation is appointed. Then the check is carried out in six months and again one year from the day of implantation, and then every year.

The operating time of the EKS depends on many factors. On average, this period is 7-10 years, and in children it is usually much less, which is associated, in particular, with the growth of the child's body. Control of the stimulant, as well as its programming for a specific patient, is performed by the doctor. Verification of the efficiency of the device must be carried out in a timely manner. Also, if necessary, the program is also adjusted - the specified parameters of functioning. This may be necessary if the pacemaker does not perform the tasks assigned to it: the heart rate is too low or high and / or the patient is not feeling well. Also, other settings can be set by the doctor when changing a person's lifestyle and lack of stimulation, such as active sports.

The main cause of the failure of the EKS is a decrease in the capacity of the battery - its discharge. In such cases, the device must be replaced with a new one, and a cardiologist consultation is required. Electrodes, which are in the heart cavity, usually remain for life and in good working conditions do not require replacement, giving the person the opportunity to fully live, despite heart problems.