Distinguish 2 types of 2nd degree AV block: type I, which is a relatively harmless cardiac arrhythmia, and which is considered a serious disorder that requires additional research.
AV block II degree, type I (Mobitz I, Wenckebach periodics)
With this type of AV block we are talking about the so-called Wenckebach period. The PQ interval is initially normal.
With subsequent heart contractions, it gradually lengthens until the ventricular complex (QRS complex) falls out, since the conduction time in the AV node turns out to be too long and conduction of the impulse through it becomes impossible. This process is repeated.
AV block II degree, type I (Wenckebach period).On the upper ECG the Wenckebach periodic is 3:2. On the lower ECG, the Wenckebach 3:2 periodic changed to a 6:5 periodic.
Long registration. Paper speed 25 mm/s.
Second degree AV block, type II (Mobitz II)
With this blockade, every 2nd, 3rd or 4th impulse from the atrium (P wave) is carried out to the ventricles. Such rhythm disturbances are referred to as AV block 2:1, 3:1 or 4:1. On the ECG, despite the fact that P waves are clearly visible, the corresponding QRS complex appears only after every 2nd or 3rd wave.
As a result, with a normal atrial contraction rate, severe bradycardia may occur, requiring implantation of a pacemaker.
AV block with Wenckebach periodicity can be observed with vegetative-vascular dystonia and ischemic heart disease, while cardiac arrhythmias of the Mobitz type II are observed only with serious organic damage to the heart.
Second degree AV block (Mobitz type II).
A 21-year-old patient who had myocarditis. Only every 2nd atrial impulse is conducted to the ventricles.
The ventricular contraction frequency is 35 per minute. Complete blockade of PNPG.
Training video for detecting AV block and its degrees on an ECG
If you have problems watching, download the video from the pageAtrioventricular block is a pathological condition in which the propagation of excitation in the heart from the atria to the ventricles is impaired. In this case, rhythm and blood circulation are disrupted.
Between the atria and ventricles of the heart is the atrioventricular node - a collection of cells resembling nerve cells in structure and function. It receives electrical impulses from the atria, delays them for a fraction of a second, and then sends them into the ventricle. Thanks to this, the parts of the heart contract consistently, blood circulates correctly. With atrioventricular block, the delay of the nerve impulse becomes longer, or it does not pass at all.
Causes of atrioventricular block
In most cases, atrioventricular block is one of the symptoms of various heart diseases:
Atrioventricular block can develop in athletes during intense training, while taking certain medications (antiarrhythmic drugs,).
Symptoms of atrioventricular block
There are three degrees of atrioventricular block. Each of them manifests itself with its own symptoms.
In first-degree atrioventricular block, nerve impulses from the atria to the ventricles are conducted more slowly than normal. This does not affect the person’s condition in any way: he feels completely normal. Changes are discovered incidentally during electrocardiography. If the heart rate drops below 60, you may experience weakness, increased fatigue, shortness of breath, and chest pain.
In second degree atrioventricular block, some impulses from the atria do not reach the ventricles. That is, the atria send blood to the ventricles, but the ventricles do not pump it to the organs and tissues. When this happens, a person suddenly feels weak, dizzy, and his vision becomes dark. Shortness of breath, chest pain,...
With the third degree of atrioventricular block, impulses from the atria to the ventricles do not pass at all. The ventricles begin to generate impulses themselves and contract at a frequency of 40 beats per minute. The same symptoms occur as with the second degree of blockade, but they are more pronounced. If the heart rate drops to 20 beats per minute or lower, the brain stops receiving the required amount of oxygen. The person loses consciousness, his skin turns blue.
What can you do?
Atrioventricular block II and III degrees is a serious disease that requires urgent treatment. If symptoms occur, you should contact a cardiologist. According to statistics, patients with atrioventricular block are at high risk of developing sudden death as a result of cardiac arrest.
If symptoms reminiscent of third degree atrioventricular block occur, you should immediately call an ambulance.
What can a doctor do?
Atrioventricular block is detected using electrocardiography. It helps to see all the disturbances in the propagation of electrical impulses in the heart.
With first degree atrioventricular block, observation is usually sufficient and no special treatment is required. You need to be careful when taking medications that affect your heart function. If a doctor prescribes such drugs, the patient should warn him about heart rhythm disturbances.
For second and third degree atrioventricular block, a pacemaker is installed. During an attack, when impulses from the atria are not conducted to the ventricles at all, emergency assistance is required.
Forecast
With the first degree of blockade, the prognosis is favorable. In grades II and III, patients often become unable to work. The use of a pacemaker helps to significantly improve their quality of life and prolong it. With congenital blockade, the prognosis is more favorable than with acquired blockade.
Prevention
Timely treatment of heart disease helps prevent the development of atrioventricular block.
With second degree AV block, unlike first degree, impulses from the atria do not reach the ventricles every time. In this case, the duration of the PQ(R) interval can be either normal or increased.
Second degree AV block is usually divided into three types:
Mobitz type AV block 1.
It is characterized by a consistent, from complex to complex, progressive prolongation of the PQ(R) interval followed by loss of the ventricular QRS complex. That is, P is present, but QRS does not follow it.
Once again, signs of second-degree AV block type Mobitz 1.
Consistent, from complex to complex, progressive prolongation of the PQ(R) interval with subsequent loss of the ventricular QRS complex. This lengthening and loss is called the Samoilov-Wenckebach periods.
ECG No. 1
In this ECG we see how PQ(R) gradually increases from 0.26 to 0.32 s; after the last (4) P, the QRS complex did not arise - the impulse was blocked in the AV node. All! This is the Mobitz type 1 blockade.
Then the next P usually occurs again and the cycle resumes. But this ECG is also interesting because after 0.45 s. the QRS complex nevertheless arose, but not because the impulse was transmitted through the AV node, but because a replacement rhythm arose from that part of the AV node that is located below the blockade. This is a defense mechanism and here it worked perfectly. Most often, in the place where the QRS arose, just another P appears and the cycle resumes. But let's not go into details.
Mobitz type AV block 2.
This blockade is characterized by the appearance of episodes of sudden “loss” of the QRS after the P wave, without previous prolongation of PQ(R). In practice it looks like this.
It must be said that recognizing second degree blockades is often very difficult, while identifying first and third degree AV blocks is not very difficult.
We still have the so-called advanced blockade, it occupies an intermediate position between blockade of the II and III degrees, and for a better understanding of it we will talk about it after we consider
with atrioventricular degree II (3:2)a - Mobitz type I (with Samoilov-Wenckebach periods)
b - Mobitz type II
For all forms of AV blockade of the second degree:
1. Sinus is preserved, but in most cases,
2. Periodically, the conduction of individual electrical impulses from the atria to the ventricles is completely blocked (there is no QRST complex after the P wave)
Type I AV block, 2nd degree
Or Mobitz type I (more common in nodular blockade).ECG with 2nd degree AV block, type 1
See picture above(a)1. A gradual, from one complex to another, increase in the duration of the P - Q R interval, which is interrupted by the loss of the ventricular QRST complex (while the P wave remains on the ECG)
2. After the QRST complex falls out, a normal or slightly extended P - Q R interval is recorded again. Then everything is repeated (Samoilov-Wenckebach period). The ratio of P and QRS is 3:2, 4:3, etc.
Type II AV block, 2nd degree
or Mobitz type II (more common with distal blockade).ECG with 2nd degree AV block, type 2
See picture above (b)1. Regular (type 3:2, 4:3, 5:4, 6:5, etc.) or random loss of the QRST complex (while maintaining the P wave)
2. The presence of a constant (normal or extended) P - Q R interval without its progressive lengthening;
3. Sometimes - widening and deformation of the QRS complex
AV block - 2nd degree block, type 2:1. ECG data
ECG with second degree atrioventricular block.
a - atrioventricular block of the second degree, type 2:1
b - progressive atrioventricular block of the second degree
1. Loss of every second QRST complex while maintaining correct sinus rhythm;
2. P - Q R interval normal or extended
3. With the distal form of blockade, expansion and deformation of the ventricular QRS complex is possible (non-permanent sign)
Not uncommon. Occurs due to a disturbance in the conduction of impulses from the atria to the ventricles. Pathology develops against the background of various heart diseases.
If the conduction of electrical impulses through the AV node is disrupted, atrioventricular block occurs. The sinus node produces an impulse that travels along the atrial pathways. It then passes through the atrioventricular node. Here its speed decreases. Next, the impulse enters the ventricular myocardium, causing them to contract.
If pathological changes are observed in the atrioventricular node (AV) and the passage of the impulse through it slows down, then a blockage of the signal from the atria to the ventricles occurs.
Possible causes of heart block:
- Overdose of drugs (antiarrhythmic drugs, cardiac glycosides).
- Rheumatic pathologies.
- Ischemic disease.
- Cardiosclerosis.
Surgical manipulations in the heart area, etc., can contribute to the development of AV block.
If the rhythm is not disturbed, the patient may not notice the blockade of the atrioventricular node. This is the 1st degree of AV block, which is detected during a medical examination or examination.
With 2nd degree blockade, the patient feels a sinking heart (slow heartbeat) and experiences deterioration in health during physical exertion.
The passage of the impulse is incomplete and the longer the interval, the more pronounced the symptoms.Manifestations of blockade are observed with a decrease in heart rate. Symptoms such as dizziness, shortness of breath, weakness, chest pain, and short-term fainting appear.
3rd degree AV block is characterized by a severe course. The main clinical manifestations are persistent shortness of breath and Morgagni-Adams-Stokes attacks. With complete blockade, symptoms increase and are observed even at rest.
Possible complications
Against the background of AV block, the heartbeat slows down and organic damage to the heart occurs. This not only worsens the patient's condition, but can also lead to serious consequences.
If it has not been observed before, then over time it may appear and worsen.
Possible complications with atrioventricular block:
- Manifestations of a Morgagni-Adams-Stokes attack. The attacks are characterized by difficulty breathing, the appearance of convulsions, and sudden fainting. An attack occurs due to cerebral hypoxia. In this case, the patient needs urgent medical attention.
- A decrease in intellectual abilities and memory against the background of AV block occurs due to chronic oxygen starvation of the brain.
- Exacerbation of ischemia.
- Development of cardiogenic shock. In cardiogenic shock, the blood supply to organs is disrupted due to abnormal heart rhythms.
- In severe cases, if help is not provided in a timely manner, the attack can be fatal.
To avoid the development of serious consequences, it is important to promptly consult a doctor at the first signs of a malfunction of the heart. Only qualified specialist help can prevent their development.
Diagnostic methods
Initially, when visiting a doctor, the patient is examined and a medical history is taken. The doctor also listens to the heart rhythm and identifies possible abnormalities. If AV block is suspected, additional diagnostic measures are carried out.
To diagnose atrioventricular block, instrumental methods are prescribed: ECHO-cardiography, Holter method. The most informative is the electrocardiogram. This method allows you to determine the degree of conduction disturbance, signs of ischemia, and contraction frequency.
In the first degree of blockade, the ECG shows an increase in the PQ interval, but the sinus rhythm remains correct. With a second-degree block, an abnormal heart rhythm is noted and there is no QRS complex after P. This is a complete blocking of the excitation impulse, which occurs periodically.
The third degree of blockade will be indicated by an increase in the number of atrial complexes, as opposed to ventricular complexes.
Daily ECG monitoring can be carried out, during which signs of blockage, patient sensations, the effect of physical activity and results after taking medications are determined.
If there is a history of cardiac diseases, magnetic resonance imaging or CT cardiography may be prescribed. Your doctor may order laboratory tests for acute and chronic illnesses. This allows you to determine the amount of enzymes, the level of antiarrhythmics and other indicators.After a comprehensive examination, appropriate treatment is prescribed.
Features of treatment and prognosis
Treatment is carried out taking into account the degree of AV block. If stage 1 is diagnosed, then the patient in this case does not need treatment. Periodically, the patient must visit a cardiologist who will monitor his health.
Drug treatment is carried out for 2 and 3 degrees of atrioventricular block. It is necessary to establish the cause that led to the pathology and eliminate it.
Conservative therapy involves the use of certain groups of drugs:
- Beta-adrenomimetics (Isadrin, Atropine, Dobutamine, etc.), beta-blockers, anticoagulants, antibiotics, thrombolytics.
- Adrenergic agonists improve signal transmission and increase the strength of heart contractions, beta blockers lower blood pressure, anticoagulants prevent the formation of blood clots, and thrombolytics destroy blood clots.
- When taking glycosides, antiarrhythmic drugs, adrenoblockers, the doctor may cancel them or partially replace them.
- In case of acute heart failure, Glucagon 5 mg is administered intravenously over an hour. If necessary, diuretics and vasodilators are prescribed. It is possible to use Eufillin, Teopeka, Corinfar.
If a complete block is diagnosed, temporary electrical stimulation is performed to restore cardiac conduction. If necessary, a pacemaker is installed to restore the heart rhythm and heart rate.
In many cases, after treatment of the underlying cardiac pathology, conduction through the atrioventricular node is restored.
AV block is a serious pathology that, if not treated promptly, can lead to serious consequences. Elderly people are at risk. This category of people should undergo medical examination regularly. If you consult a doctor in a timely manner and start treatment, the prognosis is favorable.
More information about how the human heart works can be found in the video:
AV node block in most cases is a complication of the underlying disease and most often coronary heart disease. Prevention of atrioventricular block involves preventing heart pathologies, as well as their timely treatment.
To avoid the development of diseases of the cardiovascular system, it is necessary:
- Take care of your health, lead a healthy lifestyle, give up bad habits, and engage in moderate physical activity.
- Nutrition must be correct and complete. It is recommended to exclude fatty, fried, salty foods from the diet. It is advisable to eat more foods containing potassium and magnesium. These microelements have a beneficial effect on the heart muscle.
- Stressful situations should be avoided, as they negatively affect the central nervous system and heart activity.
- You need to sleep at least 8 hours a day. Everyday work must be diluted with short rests.
- It is important to regularly visit a cardiologist and undergo the necessary tests, then there will be no problems with the functioning of the heart.
By following these simple preventive measures, the development of many diseases can be prevented.
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