Intra-atrial conduction block

Introduction to intra-atrial conduction block Intra-atrial block, referred to as intra-atrial block, refers to the conduction of the normal sinus node along the conduction system between the sinus node and the atrioventricular node, that is, the internode, and the activation is transmitted to the atrioventricular node. The room branch of the front knot (also known as Bachmann fiber) will be excited from the room to the left room. When there is an obstacle to the conduction function of the internode, an intra-atrial block is present. basic knowledge The proportion of illness: the incidence rate is about 0.002%-0.003% Susceptible people: no special people Mode of infection: non-infectious Complications: syncope A-S syndrome sudden death heart failure cerebral infarction

Atrial block

Common causes of incomplete atrial block (30%):

(1) The cause of incomplete atrial block: atrial fibrosis, adipose, amyloidosis and other degenerative changes, hypertrophy and/or dilatation of the left atrium and/or right atrium, atrium Acute or chronic inflammation of the muscle, acute atrial myocardium, chronic ischemia or atrial infarction can lead to atrial block, and incomplete atrial block is mostly seen in organic heart disease, such as rheumatic heart disease. Mitral stenosis, hypertension, heart failure, coronary heart disease, myocardial infarction, myocarditis, some congenital heart disease (such as atrial septal defect), cardiomyopathy, chronic pericarditis, hyperkalemia, increased vagal tone, digitalis And the effect of quinidine can lead to incomplete atrial block, incomplete atrial block is not only the conduction block of the room bundle or internode, usually left atrial hypertrophy, left atrial volume And persistent or temporary increase in pressure in the left atrium, or signs of increased left ventricular end-diastolic pressure.

(2) The cause of intermittent incomplete atrial block: Intermittent intraventricular block can be seen in all age groups, 7 to 97 years old, and many cases reported in China have organic heart disease, such as coronary heart disease. Cardiomyopathy, hypertensive heart disease, rheumatic heart disease, chronic obstructive pulmonary disease, constrictive pericarditis, sick sinus syndrome, etc., elderly patients with intraventricular conduction disorders may be associated with degeneration of cardiac conduction tissue About 36% of the intermittent intraventricular block reported in foreign countries have organic heart disease. Some cases have been observed for several months. After several years, they have changed from intermittent to fixed (persistent) intraventricular block, intermittent. The occurrence of intra-atrial blockade suggests atrial lesions.

Common causes of complete atrial block (atrial dislocation, atrial separation) (25%):

Common in the advanced stage of rheumatic heart disease, critical coronary heart disease patients, digitalis poisoning, uremia, quinidine poisoning, etc., part of the ECG performance before dying.

Common causes of sinus-ventricular conduction (15%):

More common in hyperkalemia.

The cause of diffuse complete atrial block (15%):

Clinically more common in hyperkalemia.

Pathogenesis

1. The pathogenesis of incomplete atrial block

(1) Mechanism of incomplete atrial block: Incomplete atrial block is mainly caused by prolonged conduction time in the atrium. Prolonged atrial conduction time can only be expressed in the right atrium, on the electrocardiogram. The amplitude of the first half of the P wave is increased (the first half of the P wave is the right atrial depolarization, the second half is the left atrial depolarization); it can also occur in the right to left heart chamber or the left atrium conduction delay, which is expressed as P wave The second half of the time limit is widened and the amplitude changes.

(2) Mechanism of intermittent incomplete atrial block: The intraventricular conduction disorder in the elderly may be related to the degeneration of cardiac conduction tissue, and about 36% of the intermittent intraventricular block reported abroad. In the case of quality heart disease, some cases were observed for several months. After several years, they changed from intermittent to fixed (persistent) intraventricular block. The occurrence of intermittent intraventricular block showed atrial disease.

2. The mechanism of complete atrial block

Complete atrial block is still a bidirectional phenomenon in a localized atrial muscle lesion, that is, a complete block of afferent and efferent block, and an atrial ectopic rhythm in the block. The autonomic changes of atrial ectopic excitability are more frequent, and the normal sinus rhythm (or ectopic atrial rhythm) outside the block can also change. The two rhythm points inside and outside the block do not affect each other. Complete blockade of atrial dislocation, because complete intraventricular block is limited to the block, so it is considered that this block should be called a localized complete atrial block more appropriate, according to the block outside the block The basic heart rhythm is sinus or atrial and divided into two types: 1 sinus with isolated atrial ectopic rhythm, such as atrial flutter, atrial fibrillation, atrial tachycardia, etc.; 2 atrial ectopic rhythm with isolated Atrial flutter, atrial fibrillation, atrial tachycardia, etc.

3. Mechanism of sinus-ventricular conduction

Atrial muscle extensive electrical paralysis, atrial muscle loss of excitability, conduction, while sinoatrial node, internodal bundle and atrioventricular conduction system are still excitatory and conductive, sinus activation can be directly along the internode, atrioventricular conduction The bundle is passed down to the ventricle and has nothing to do with the atrial muscle.

4. The mechanism of diffuse complete atrial block

All the conduction beams (room bundles and internodes) and atrial muscles in the atrium are excitatory and conductive. There are no sinus P waves on the electrocardiogram, and there is no atrial rhythm (no atrial P' wave, atrial flutter). Dynamic or atrial fibrillation).

Atrial block prevention

1. Pay attention to dietary intake and ensure sleep:

Try to reduce the intake of fat and cholesterol. If you eat meat, "fish is better than poultry, poultry is better than livestock." Pork and beef with high fat and cholesterol content are less delicious. Deep-sea fish have cardiovascular effects. Certain health effects. Especially for foods containing high cholesterol such as egg yolk, crab yellow, crab, animal brain, fish paste, and fish fat.

2. Tai Chi:

It has a good preventive effect on hypertension and heart disease, and is a common method for preventing and treating heart disease. In general, patients with better physical strength can practice old-fashioned Tai Chi, and those with poor physical strength can practice simplified Tai Chi. If you can't play a full set, you can play half a set. If you are weak and have poor memory, you can practice only individual actions, and practice in separate sessions.

Atrial block Complications, syncope, A-S syndrome, sudden death, heart failure, cerebral infarction

Complications such as syncope, dizziness, A-S syndrome or sudden death may occur. Heart failure, pulmonary infarction, cerebral infarction, myocardial infarction, sudden death, pulmonary heart disease, multiple organ failure, etc. may also occur. Room septal defect, ventricular septal defect and patent ductus arteriosus are often prone to pneumonia, prone to heart failure, Fallot's quadruple syndrome can often be complicated by cerebral thrombosis, brain abscess and other diseases.

Symptoms of atrial blockade Common symptoms Shortness of breath, shortness of breath, shortness of breath, chest tightness, heartbeat, disorder, atrioventricular septum, sudden incomplete, intraventricular block

1. Incomplete atrial block: Although there is no hemodynamic significance, but half of patients often have recurrent episodes of paroxysmal atrial fibrillation or atrial flutter, 40% of patients may have atrial Pre-systolic and atrial tachycardia history, patients may have chest tightness, shortness of breath, heartbeat and other symptoms.

2. Complete atrial conduction block: that is, atrial separation, more common in the critical period of structural heart disease, often occurs several hours before the death of critically ill patients, in addition to digitalis poisoning, uremia and drugs (such as taking amines) The effects of iodophenone can also be seen, often manifested as the clinical manifestations of the primary disease.

3. Diffuse complete atrial block and sinus-ventricular conduction: both due to hyperkalemia, but the latter is a wide range of electrical paralysis of the atrial muscle, atrial muscle loss of excitability and conduction, and sinoatrial node, The internode and atrioventricular conduction system are still excitatory and conductive, and can transmit sinus agitation to the ventricle; while the conduction and atrial muscles in the atrium of the former are completely excitatory and conductive, showing sinus arrest. When the sinus arrest time is long, it can cause dizziness or syncope, and even A-S syndrome, long-term sinus arrest, if not accompanied by escape, can cause sudden death.

Electrocardiogram with incomplete atrial block

(1) ECG characteristics of incomplete incomplete atrial block:

1 determined as sinus rhythm.

2 There is a dynamic change in P wave morphology and/or polarity.

At the same time of the 3P wave change, the PR interval is generally unchanged. Due to the delayed conduction in the atrial, some patients may have a prolonged PR interval.

4 ECG typing:

A. Immobility incomplete left atrial block: also known as Bachmann beam block, due to room beam breakage, degeneration or fibrosis, ECG performance: P wave time widening >0.11s, its amplitude is not high; P wave can appear as notch, frustration, double peak, biphasic, if it is double peak, the peak distance of double peak is 0.04s, showing a fixed mitral valve P wave, which is related to left atrial hypertrophy and atrial overload. The P wave morphology is difficult to identify, and this diagnosis can only be made after echocardiography is used to exclude left atrial overload or left atrial hypertrophy.

B. Immobility incomplete right atrial block: delayed conduction in the right atrium, depolarization time extension, top-down depolarization vector increases, and overlap with the subsequent left atrial depolarization vector to make left and right atrial depolarization Synchronization in the same direction, ECG performance: P wave amplitude increases, II, III, aVF lead on the P wave high tip, at this time and the lung type P wave (right atrial depolarization increased) morphology is difficult to identify, should do echocardiography, Combined with clinical exclusion, the cause of pulmonary P wave and the expansion of right atrium can be diagnosed.

Incomplete atrial conduction block is divided into the following four types by recording the P-ring amplification and synchronizing the electrocardiogram.

Type 1A: P wave is dome-shaped, corresponding P ring is large and deformed; Type 2B: most common, showing double-peak P wave, P ring is bidirectional, the two parts of the ring are nearly equal in size, horizontal or left The shape is often "8" shape; 3C type: less common, P wave is high and sharp, P ring has different sizes of notch; 4D type: seen in elderly patients, P wave low level, P vector ring small and dense .

The most reliable diagnostic method for incomplete atrial block is atrial endometrial mapping. Incomplete atrial block is caused by inhomogeneous conduction and refractory period, which can cause atrial reentry tachycardia. Atrial flutter, atrial fibrillation and other atrial arrhythmias.

(2) ECG characteristics of intermittent incomplete atrial block: it can be divided into intermittent left atrial block or room block and intermittent right atrial block, both of which are incomplete Intraventricular conduction block, the incidence is significantly lower than the fixed (persistent) incomplete intraventricular block.

The electrocardiogram is a sudden change in the morphology of the sinus P wave when the sinus rhythm is uniform, and the shape of "pulmonary P wave" or "mitral valve P wave" appears.

The diagnosis of intermittent intraventricular block is only reliable based on the same sinus P wave change in the same lead, because there are many factors affecting and causing P wave morphology and frequency anomaly, but there are also different P-wave forms. The dynamic changes are reported for diagnosis.

ECG characteristics of complete atrial block

(1) There are two kinds of P waves in the same lead: usually one is the dominant rhythm of sinus rhythm (sinus rhythm can be too slow, too fast, irregular and normal), can be transmitted, followed by QRS wave; the other is Atrial ectopic P wave, its frequency can be fast or slow, regularity is poor, can not be transmitted, sinus P wave is completely unrelated to ectopic P wave, but can overlap rather than fusion wave, occasionally dominate the heart rhythm as atrial or handover area Rhythm.

(2) A part of the atrial wave is fluttering, and the other part is vibrating.

(3) The right atrial wave is sinus, and the left atrial wave is fluttering or vibrating.

3. Electrocardiographic features of diffuse complete atrial block: no sinus P wave, no ectopic atrial rhythm (no atrial P' wave, atrial flutter or atrial fibrillation wave), diffuse complete atrial Internal conduction block on ECG with persistent sinus arrest, third degree sinus block, sinus-ventricular conduction, etc. can not be identified.

4. Characteristics of sinus-ventricular conduction ECG: P wave disappears, QRS wave width deformity, indoor block, ventricular or junctional escape rhythm, T wave high tip is called hyperkalemia T wave change, if blood potassium continuously rises High, the wider the QRS wave is deformed, the T wave becomes low and blunt, and then continues to increase, eventually forming a very slow ventricular flutter or ventricular fibrillation-like waveform.

Examination of atrial block

Mainly relying on the electrocardiogram, the electrocardiogram is a sudden change in the morphology of the sinus P wave when the sinus rhythm is uniform, and the shape of "pulmonary P wave" or "mitral valve P wave" appears. The diagnosis of intermittent intraventricular block is only reliable based on the same sinus P wave change in the same lead, because there are many factors affecting and causing abnormal P wave shape and frequency, but there are also different P-wave forms. The dynamic changes are reported for diagnosis.

Diagnosis and diagnosis of atrial block

diagnosis

According to the medical history, symptoms, signs and electrocardiogram performance can be clearly diagnosed.

Differential diagnosis

1. Intermittent incomplete intraventricular block and differential diagnosis of the following conditions

(1) P wave electric alternation: the PR interval is consistent, there is no P wave polarity or directional change, P wave changes alternately, and there is no transition P wave.

(2) Wandering heart rhythm: PR interval is inconsistent, often P wave polarity and directional change, P wave change is gradual, with transitional P wave, and intermittent PR interval is more consistent during intermittent intraventricular block There are few P-wave polarities or directional changes, P-wave changes are often abrupt changes, and few transitional P-waves appear. However, it can occur when the internodes are second-degree I-type Wen's block.

(3) atrial infarction: 1P wave high deformity, partly due to conduction disturbance in the room; 2P-R segment elevation or decrease; 3 often atrial arrhythmia.

(4) Differential conduction in the room: one or several sinus P wave morphological changes commonly seen in various types of pre-contraction or parallel rhythm, which can be called the clock phenomenon.

2. Differential diagnosis of complete intraventricular block

(1) Firstly eliminate all possible artifacts, interference, such as artificial artifacts, myoelectric interference, etc.: can be repeatedly tested at different times and under different conditions by using different ECG machines, especially the pseudo-electromyogram Poor, can be tested by breath holding, if the ectopic small P wave still exists, the myoelectric artifact can be ruled out.

(2) Identification with atrial rhythm: When the atrial rhythm is parallel, there is only a protective afferent block in the atrial pacing point, but there is no complete blockade, so the whole atrium can be excited and ectopic P wave, can be transmitted into the ventricle to generate QRS waves, or interfere with sinus agitation, form atrial fusion wave, and often have ventricular capture, P wave of atrial parallel rhythm, slightly larger than sinus P wave or etc. Large; atrial separation P wave children are not easy to see, atrial parallel rhythm PP is relatively constant, atrial parallel rhythm vagus nerve stimulation, can make parallel heart rhythm slow, but no effect on atrial separation.

3. Diffuse complete atrial block

On the electrocardiogram with persistent sinus arrest, third degree atrioventricular block, sinus-ventricular conduction, etc. can hardly be identified.

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