Atrioventricular block

Introduction Ventricular block means that the impulse is blocked during the conduction of the atrioventricular. Divided into two categories of incompleteness and completeness. The former includes first- and second-degree atrioventricular block, the latter also known as third-degree atrioventricular block, and the block can be in the atria, atrioventricular node, His bundle and double bundle. Pay attention to the cause of atrioventricular block, whether there is organic heart disease, whether to take antiarrhythmic drugs for a long time or a large amount, whether there is cardiac surgery, inflammation, electrolytes and acid-base imbalance, etc., whether there is excessive vagal tone, Carotid sinus syndrome.

Cause

Cause:

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 drugs: such as digitalis and other antiarrhythmic drugs, most of the discontinuation of the drug, atrioventricular block disappeared.

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

5 high blood potassium, uremia and so on.

6 idiopathic conduction system fibrosis, degeneration, etc.

7 trauma, accidental injury during cardiac surgery or affecting atrioventricular conduction tissue can cause atrioventricular block.

an examination

Electrogram examination can determine the diagnosis and should be differentiated into incomplete (I degree and II degree) or complete (III degree) atrioventricular block. If necessary, the conditional person can also use the His bundle beam diagram.

First, once atrioventricular block:

The 1P-R interval is >0.20 seconds, and after each P wave, there are QRS complexes.

Second and second degree atrioventricular block:

Some atrial agitation cannot be transmitted to the ventricle. Some P waves do not have a QRS complex, and the ratio of atrioventricular conduction may be 2:1; 3:2; 4:3. The second degree of atrioventricular block can be divided into two types. Type I is also known as the Wenshi phenomenon, or Mohs type I, and type II is also known as Mohs type II.

(1) Second degree type I conduction block-Wen's phenomenon: 1P-R interval is gradually extended until P wave is blocked and ventricular leakage, 2R-R interval is gradually shortened until P wave is blocked by III°AVB; The RR interval including the blocked P wave is shorter than the sum of the two PP intervals.

(B) second degree type II atrioventricular block Mohs type II: 1P-R interval fixed, can be normal or prolonged. The 2QRS wave group has intermittent leakage, and the degree of blockage can be changed frequently, which can be 1:1; 2:1; 3:1; 3:2; 4:3. The QRS complex of the downlink is mostly a bundle branch block pattern.

The first and second degree of type I atrioventricular block, the block site is mostly at the atrioventricular node, and the QRS complex does not widen; the second degree of type II atrioventricular block, the block is more in the Greek Below the beam, the QRS complex is often widened.

(3) Complete atrioventricular block (third degree atrioventricular block): 1P wave is independent of QRS group; 2 atrial rate is faster than ventricular rate, atrial rhythm may be sinus or originated from ectopic; 3 Ventricular rhythm is maintained by the junction zone or ventricular autonomous pacemaker.

The shape of the QRS complex mainly depends on the location of the block. If the block is located above the branch of the His bundle, the escape beat point originates from the high ventricular arrhythm near the branch of the atrioventricular junction, and the QRS complex does not. Widening. If the block is located in the double bundle branch, the escape rhythm is low ventricular arrhythmia, and the QRS complex is widened or deformed. The rate of high escape rhythm in the adjacent compartment junction is often between 40-60 beats per minute, while the rate of low ventricular autonomic rhythm is between 30-50 beats per minute.

Differential diagnosis

According to typical ECG changes combined with clinical manifestations, it is not difficult to make a diagnosis. In order to estimate the prognosis and determine treatment, it is necessary to distinguish between physiological and pathological atrioventricular block, atrioventricular bundle block and three-branch block, and the degree of block.

The material in this site is intended to be of general informational use and is not intended to constitute medical advice, probable diagnosis, or recommended treatments.