What Is an Atrioventricular Block?

In the process of cardiac electrical activation, abnormal electrical conduction between the atrium and ventricle can lead to arrhythmia, which prevents the heart from contracting and pumping blood. Atrioventricular block can occur in different places such as the atrioventricular node, the His bundle, and the bundle branch. According to the degree of block, it can be divided into first-degree, second-degree and third-degree atrioventricular block. The clinical manifestations, prognosis, and treatment of the three types of atrioventricular block are different.

Basic Information

nickname

Atrioventricular block

English name

atrioventricular block

Visiting department

cardiology

Common locations

heart

Common causes

Myocardial inflammation caused by various reasons is an important cause of this disease

Common symptoms

Usually asymptomatic, with symptoms such as palpitations, fatigue, fatigue, dizziness, etc.

Causes of atrioventricular block

1. Myocardial inflammation is most common for a variety of reasons, such as rheumatic, viral myocarditis, and other infections.

2. Vagus nerve excitement, often manifested as transient atrioventricular block.

3. Adverse drug reactions may lead to slow heart rate, such as digoxin, amiodarone, and equal heart rate. Most atrioventricular block disappears after stopping the drug.

4. Various organic heart diseases, such as coronary heart disease, rheumatic heart disease and cardiomyopathy.

5. Hyperkalemia, uremia and so on.

6. Idiopathic conduction system fibrosis, degeneration (ie aging), etc.

7. Atrioventricular block can be caused by trauma, cardiac surgery or interventional surgery, and accidental injury during catheter ablation or when it affects the atrioventricular conduction tissue.

Atrioventricular block classification

1. atrioventricular block

It means that the electrical conduction velocity from the atrium to the ventricle is slowed down, and the electrocardiogram shows that the PR interval is longer than 0.20s, but each atrial activation can be transmitted to the ventricles.

2. Second-degree atrioventricular block

It is divided into type I (Wen's or Mohs type I) and type II (Mohs type II). Second-degree atrioventricular block is the most common type of second-degree atrioventricular block, which means that the conduction time from the atrium to the ventricle gradually increases until one atrial excitement cannot be transmitted to the ventricle. Second-degree type II atrioventricular block refers to the sudden block of atrial excitement that cannot be transmitted to the ventricle. The electrocardiogram shows a QRS complex with intermittent leakage.

3. Third-degree atrioventricular block

Also known as complete atrioventricular block, it means that all atrial agitation cannot be transmitted to the ventricle. It is characterized by atrial and ventricular activities that are independent and irrelevant; and the atrial rate is faster than the ventricular rate.

Atrioventricular block clinical manifestations

Patients with first-degree atrioventricular block are usually asymptomatic.

Patients with second-degree type I atrioventricular block may be asymptomatic, and if they are symptomatic, they may feel palpitation or apnea.

Patients with third-degree atrioventricular block have symptoms related to the rate of ventricular rate and concomitant diseases. Patients may feel tired, fatigued, dizzy, syncope, and angina pectoris. For example, they may experience chest tightness, shortness of breath, and restricted movement when they have heart failure .

The above three types of atrioventricular block can transform as the disease progresses. When the first- and second-degree atrioventricular block suddenly progresses to the third-degree atrioventricular block, the sudden decrease in ventricular rate leads to cerebral ischemia, and the patient may experience loss of consciousness, convulsions, and severe cases may cause sudden death. Only second-degree atrioventricular block developed less to third-degree atrioventricular block.

Atrioventricular block treatment

Severe second-degree and third-degree atrioventricular block can significantly slow down the ventricular rate, with obvious symptoms such as syncope, loss of consciousness, and Alzheimer's syndrome, it is necessary to implant a pacemaker to prevent it from happening Prolonged cardiac arrest, causing life-threatening.

Pacemakers can be divided into single-chamber, dual-chamber and triple-chamber pacemakers. For patients with atrioventricular block, if the economic conditions permit, it is best to implant a dual-chamber pacemaker, so as to approximate the normal atrial contraction and ventricular contraction function. But if the economy is difficult, a single-chamber pacemaker can save lives. If combined with heart failure, consider implanting a three-chamber pacemaker.

Indications for implanting a permanent pacemaker include:

1. Any level of high or complete atrioventricular block with clinical symptoms;

2. Bundle-branch horizontal block, second-degree type II atrioventricular block occurs intermittently, and there are symptoms;

3. Sick sinus node syndrome or atrioventricular block, ventricular rate is often less than 50 beats / min, there are obvious clinical symptoms, or intermittent ventricular rate is less than 40 beats / min, or the dynamic electrocardiogram shows long RR interval of up to 3s (long interval can be relaxed to 5s in patients with AF), although it is asymptomatic, it should also be considered;

4. In patients with sinus node dysfunction or (and) atrioventricular block, when other factors must be used to slow the heart rate drugs, in order to ensure proper ventricular rate, a pacemaker should be implanted.