Bilateral bundle branch block

Introduction to bilateral bundle branch block Bilateral bundle-branch block (BBBB) is referred to as double bundle branch block, also known as bilateral bundle branch block, or left plus right bundle block. It means that the left and right bundle branches are blocked at the same time. basic knowledge Sickness ratio: 0.05% Susceptible people: no special people Mode of infection: non-infectious Complications: A-S syndrome

Bilateral bundle branch block

(1) Causes of the disease

The etiology of bilateral bundle branch block is similar to that of right bundle branch block and left bundle branch block. It is a serious damage of the bundle bundle under the His bundle, reflecting a wide range of lesions involving ventricular septum and The bundle branch conduction system in the ventricular muscles on both sides is easy to develop into a third degree atrioventricular block, especially in the case of high bilateral bundle branch trunk block.

(two) pathogenesis

When the bilateral bundle branches are blocked, the pathophysiological characteristics when they are excited through them are as follows: When the left and right bundle branch conduction times are significantly different, the beam branch block diagram of the bundle branch conduction delay occurs, when both sides When the difference of the bundle branch conduction velocity is 25 to 40 ms, the pattern of incomplete beam branch block appears. If the difference is greater than 40 ms, the pattern of complete beam branch block appears, so the conduction time of the bundle branch on both sides is not At the same time, the PR interval represents the atrioventricular conduction time on the faster side of the conduction velocity, and the QRS wave represents a slower beam bundle block diagram.

1. PR interval

Only the bilateral bundle branch is blocked to prolong the PR interval, and the PR interval represents the time from the sinus node to pass through the lighter side of the branch to the ventricle. In addition, if the left and right bundles The conduction time of the branch is the same, then the excitement is transmitted along the left and right bundle branches at substantially the same speed, so the PR interval is the activation from the sinus node (or atrial ectopic pacemaker), through the atrium, the junction area and The time at which the left and right bundle branches are simultaneously transmitted, for example, the left and right bundle branch conduction times are slightly prolonged, and the PR interval is also slightly prolonged; if the conduction times of the left and right bundle branches are moderately extended, then PR The interval is moderately extended.

2.QRS waveform

The QRS waveform depends on the degree of blockage of the left and right bundle branches, whether the ratio of atrioventricular conduction, conduction velocity, etc. are the same or consistent, and can be expressed as:

(1) If the factors of the left and right bundles are the same or the same, then the excitement is simultaneously transmitted along the double bundle branch, and the process is the same as normal, and the generated QRS wave is also normal.

(2) If any of the above factors is inconsistent between the left and right bundles, the activation is slow, the conduction time is short, and the side of the atrioventricular conduction occurs early (for example, left) The bundle branch is transmitted down to produce a contralateral (right bundle branch) block pattern (complete right bundle branch block pattern), and complete right bundle branch block and complete left bundle branch block pattern may alternate.

3. Atrioventricular conduction ratio

Depending on the degree of blockage of each bundle, whether the proportion of the atrioventricular compartment and the proportion of the atrioventricular conduction of each bundle branch are the same, and whether the same ratio of the atrioventricular conduction occurs at the same time, etc., can be expressed as:

(1) When the left and right bundles have the same ratio of compartments, the following two situations can occur:

1 If the atrioventricular conduction occurs at the same time, the ratio of the atrioventricular conduction to the ratio of the compartments of the bundle branch is the same regardless of which side of the bundle is transmitted down or simultaneously along the left and right bundle branches.

2 If the atrioventricular conduction occurs in succession, for example, the left and right bundles have a second degree (2:1) block, then the ECG does not show a 2:1 atrioventricular conduction ratio, but a 1:1 atrioventricular conduction. However, the QRS wave showed complete left bundle branch block and complete right bundle branch block alternately.

(2) One side bundle branch is three-degree block, while the other side bundle branch is second-degree block (for example, the ratio of atrioventricular conduction is 2:1), then the excitement is transmitted along the latter, showing a 2:1 compartment. Conduction.

(3) One side bundle branch (such as the right bundle branch) is blocked once, while the other bundle branch (such as the left bundle branch) is second-degree block (for example, the ratio of atrioventricular conduction is 2:1), then each time The excitement is transmitted along the former, and a 1:1 complete left bundle branch block pattern is formed.

Bilateral bundle branch block prevention

1. Active treatment of the primary disease, timely control, elimination of causes and incentives is the key to prevent the occurrence of this disease.

2. If the drug response is poor, an artificial cardiac pacemaker should be placed to prevent the occurrence of cardio-cerebral syndrome.

3. Diet has a section, daily life is always, emotional comfort, work and rest, avoiding evil, appropriate physical exercise to enhance physical fitness.

Bilateral bundle branch block complications Complications

When there is a third degree of atrioventricular block, chest tightness, palpitations, blackness, syncope, etc. may occur, and severe cases may have A-S syndrome.

Bilateral bundle branch block symptoms Common symptoms Dizziness, chest tightness, heart palpitations

If the degree of bundle branch block is light, there is no obvious symptom in itself. When the degree of blockage is heavy, arrhythmia may occur. When the third degree atrioventricular block occurs, the ventricular rate may be very slow, and palpitations and chest tightness may occur easily. Dizziness, syncope, A-S syndrome, etc.

1. Complete bilateral bundle branch trunk block

(1) When the third degree atrioventricular block is present on the electrocardiogram, and the patient must have organic heart disease according to other tests, especially in the case of left ventricular cirrhosis and cardiomyopathy, this third degree atrioventricular block should be considered. The stagnation may be caused by a complete bilateral bundle branch trunk block.

(2) When the third degree atrioventricular block is involved, there are various dynamic changes of the incomplete bilateral bundle branch trunk block pattern before and after, which is beneficial to the diagnosis of complete bilateral bundle branch trunk block.

2. Incomplete bilateral bundle branch trunk block

Incomplete cases of bilateral bundle branch block should be considered in the following situations, especially if the patient is confirmed to have structural heart disease according to other tests, especially those with left ventricular cirrhosis and cardiomyopathy.

(1) Once atrioventricular block:

1 When the bilateral bundle branches are slightly blocked, the conduction time is the same, symmetrical, the ECG shows a slight extension of the PR interval, QRS morphology, time limit is normal, the ratio of atrioventricular conduction is 1:1, only on the ECG At one time, atrioventricular block was presented, which was difficult to identify with the atrioventricular block that was blocked by the junction.

2 When the bilateral bundle branches are moderately blocked, the conduction time is the same, symmetrical, the ECG is moderately prolonged in the PR interval, the QRS morphology, the time limit is normal, the atrioventricular conduction ratio is 1:1, and the ECG is only once Atrioventricular block, which is difficult to distinguish from the atrioventricular block that is blocked by the junction area.

(2) Second degree atrioventricular block: When the bilateral bundle branches are second-degree block, the proportion of the atrioventricular compartment is the same (2:1), and the conduction time is the same, and the ECG shows a slight extension of the PR interval; QRS wave morphology, normal time limit, atrioventricular conduction ratio of 2:1, only second degree atrioventricular block on ECG, and it is difficult to identify second-degree atrioventricular block with junction block.

(3) Once atrioventricular block with bundle branch block:

1 When the bilateral bundle branch block is blocked once, the right bundle branch is mild, and the left bundle branch is moderate once blocked, the ECG shows a slight extension of the PR interval (first degree atrioventricular block) The QRS wave showed a complete left bundle branch block pattern with a ratio of 1:1.

2 When the bilateral bundle branch block is blocked once, the right bundle branch is severe, and the left bundle branch is moderate once block, the ECG shows a moderate extension of the PR interval (first degree atrioventricular block), QRS The wave is a complete right bundle branch block pattern with a ratio of 1:1.

3 When the bilateral bundle branch block is blocked by the right bundle branch, the left bundle branch is blocked twice (2:1), when the left bundle branch conduction time is longer than the right bundle branch, the ECG shows a mild PR interval. Prolonged (once atrioventricular block), QRS showed complete left bundle branch block, and the ratio of atrioventricular conduction was 1:1.

4 When the bilateral bundle branch block is blocked by the right bundle branch and the left bundle branch is blocked by three degrees, the electrocardiogram shows a slight extension of the PR interval (first degree atrioventricular block), and the QRS wave is complete. Left bundle branch block pattern, the ratio of the chamber is 1:1.

(4) Second degree atrioventricular block with bundle branch block:

1 When the bilateral bundle branch block is second-degree block, the proportion of the atrioventricular is the same (2:1), the electrocardiogram shows a slight extension of the PR interval, and the QRS is a complete left bundle branch block pattern, atrioventricular The ratio is 2:1.

2 When the bilateral bundle branch trunk block is a right bundle branch second degree block (2:1) and the left bundle branch is blocked by three degrees, the electrocardiogram shows normal PR interval, and the QRS wave is complete left bundle branch block. The pattern, the ratio of atrioventricular conduction is 2:1.

(5) Once atrioventricular block with right bundle branch block and left bundle branch block alternately:

1 When the bilateral bundle branch block is blocked by the right bundle branch once, the left bundle branch is blocked twice (2:1), and the conduction time is shorter than the right, the ECG shows a mild or moderate extension of the PR interval. At one-time atrioventricular block, the QRS wave showed a complete left bundle branch block pattern and a complete right bundle branch block pattern alternated with a ratio of 1:1.

2 When the bilateral bundle branch block showed a atrioventricular block, the left and right bundle branches were second-degree block, the proportion of the atrioventricular was the same, but at different times, the conduction time was the same, and the ECG showed a slight extension of the PR interval. At one degree of atrioventricular block, the QRS wave showed a complete left bundle branch block pattern and a complete right bundle branch block pattern alternated with a ratio of 1:1.

3 When the bilateral bundle branch trunk block is second-degree block, the conduction time right bundle branch is mildly second degree, the left bundle branch is moderately second degree block, and the atrioventricular ratio is the same, but at different times, the electrocardiogram is PR Moderate or mild extension, once atrioventricular block, QRS wave showed complete right bundle branch block and complete left bundle branch block pattern alternately, the ratio of atrioventricular is 1:1.

Bilateral bundle branch block check

Changes in the results of the corresponding laboratory tests for the primary disease may occur.

ECG features:

1. Combination of double bundle branch block

(1) The PR interval is prolonged, and the QRS wave is normal: when the bilateral bundle branch has a one- or two-degree block at the same time, and the degree of conduction between the two branches is equal and the ratio of the atrioventricular is equal, the QRS wave can be normal, but PR The interval is prolonged, and the second degree block is more obvious than the one-time block. This type is not easy to distinguish from one-degree atrioventricular block.

(2) One side bundle branch block pattern with PR interval extension:

1 Double bundle branch has a one-degree block at the same time, but the degree of delay of bilateral bundle branch conduction is different. For example, the right bundle branch is slightly blocked once, and the left bundle branch is moderately blocked. The PR interval is prolonged and one side appears. The bundle branch block pattern (for example, the complete left bundle branch block pattern) has a ratio of 1:1.

2 one side bundle branch once blocked, and the other side is third degree block, for example, the right bundle branch is a severe once block, while the left bundle branch is a third degree block, and the atrioventricular ratio is 1:1, the electrocardiogram The performance of the PR interval is prolonged, and the complete left bundle branch block pattern, this type can not exclude one side bundle branch block combined with first degree atrioventricular block.

(3) 2:1 leakage and the QRS waveform is normal: the PR interval can be slightly prolonged, because the bilateral bundle branches have secondary block at the same time, and both are synchronous 2:1 conduction block, this type should also be two Type II (2:1) atrioventricular block identification.

(4) One-side bundle branch block with ventricular wave group leakage: If it is a 2:1 leak, there are two possibilities for beam bundle level analysis.

1 The double-sided bundle branch has a second-degree block at the same time, and both sides are synchronously transmitted at 2:1, but the transmission speed is not equal, and the conduction of one side bundle branch is delayed.

The two side bundle branches have a third degree block, and the other side bundle branch has a second degree block, which is transmitted at 2:1.

(5) alternating left and right bundle branch block diagrams:

1 The double-sided bundle branch has a second-degree block at the same time, but it is not synchronously transmitted, and the conduction velocity of the bundle branches on both sides is equal or unequal.

The one side bundle branch was once blocked, while the other side bundle branch was blocked twice.

(6) The left and right bundle branches were all three-degree atrioventricular block, and the QRS wave was completely unrelated to the P wave. However, due to the complete blockage of the bilateral bundle branch, the ectopic pacemaker was located in the block. Below, the QRS complex is significantly enlarged, deformed, and the frequency is slower.

From the above, one of the reasons for the incompleteness of left-right right bundle branch block ECG is the left-right right bundle branch block, regardless of the degree (one, two, three degrees) or the type (second degree). Type I, Type II, 2:1, 3:1 and Inverse Wenshi, etc.), there are various arrangements. There are two points to note: 1 left and right bundle branch block are mutually influential, therefore, Sometimes the electrocardiogram of left and right bundle branch block is not simply the combination of left and right bundle branch block, but the characteristics of each bundle branch to maintain its blockade. This mutual influence (also known as dependence phenomenon) is often The ECG performance of each bundle branch is mutated. 2 Although any type of block can occur in each bundle, there are some common combinations: A. Second degree type I block is common in the left bundle branch; B Second degree type II block is common in the right bundle branch.

Left-to-right bundle branch block, which usually makes a diagnosis, is mostly asymmetry.

If the first four cases mentioned above, the body surface lead can only indicate the bilateral bundle branch trunk block, and the exact location of the block site depends on the His bundle beam diagram, but the alternation occurs in the same patient, or Intermittent left bundle branch and right bundle branch block pattern, combined with PR interval changes; or the same patient at right time with right bundle branch block and left bundle branch block, PR interval is constant, then the diagnosis is double Bundle branch block.

2. Special types of double bundle branch block ECG

(1) Frequency dependent intermittent double bundle branch block.

(2) occult conduction, dependence phenomenon leads to the change of double beam branch block ECG: its main feature is that one side bundle branch conduction depends on the other side bundle branch conduction, and the occult conduction depending on the phenomenon can lead to bilateral beam branch Blocking ECG has the following changes:

1 The original left or right bundle branch block pattern becomes a one-sided beam branch block pattern, and once the dependence phenomenon disappears, the previous ECG performance is restored, for example: in the right or left bundle branch (or Branches) have a degree of asymmetry, and the excitability that has been transmitted from one side of the bundle can be reversely transmitted to the other side of the bundle, so that the next excitation of the other branch is blocked. The lag, which causes the alternating block interruptions that are originally present on both sides of the bundle (such as the left bundle branch block and the right bundle branch block pattern alternately appear) to become only from the other side bundle branch, while the other side The bundle branch block pattern is continuously presented.

2 When the conduction of one side bundle branch (slow side bundle branch) is interrupted (three-degree block), the longer the conduction time of the contralateral bundle branch (fast-side bundle branch), the occult ectopic retrograde transmission to the contralateral bundle branch The greater the likelihood, the more likely the dependency phenomenon will occur.

3 When the bilateral bundle branches conduct conduction at the same time, the greater the difference in conduction time between the two sides, the greater the possibility that the branch from the fast side bundle is retrogradely concealed to the slow side bundle branch, and the dependence phenomenon is more likely to occur. Usually, this A difference must be at least 0.04 s or more, depending on the phenomenon may occur, and after a long interval, if the difference is reduced to less than 0.06 s, the dependence phenomenon is suspended, and this is manifested as one side bundle branch incomplete block. Graphics.

4 Once the dependence phenomenon is established, if other conditions remain unchanged, it will occur continuously.

The looming of the 5 dependence phenomenon depends on the degree and type of each bundle branch block, but the most important determinant is the way of excitatory conduction in the bilateral bundle branch after the intermittent stroke, if there is conduction interruption in one bundle branch, or The conduction time is significantly prolonged, the dependence phenomenon can be established or lasted, and there are two manifestations: A. The PR interval is often accompanied by the right margin branch block pattern after the leakage (sometimes 1:1 conduction) The length of the PR interval in the beam-blocking pattern reflects the dependence of the right bundle branch block on the future. B. The left bundle branch block graph is often more often than the right bundle branch block graph. There is a Wenshi phenomenon, which reflects the dependence phenomenon of the left bundle branch block. These two kinds of performances suggest that the smaller bundle branches (such as the right bundle branch) are prone to type II block, while the thicker bundle branches (such as The left bundle branch is prone to type I block (Wen's phenomenon).

6 Reversal of the direction of dependence depends on the phenomenon that one side of the bundle branch dependence is converted to the contralateral bundle branch. The electrocardiogram shows that the block diagram of the original right (or left) bundle branch suddenly changes to the left (or right) bundle branch. Blocking the graph, this can be seen in the following cases: A. In the late capture of the original slow-side bundle, the first excitement after the miss-pulse can only be transmitted from the original slow-side bundle or the conduction velocity is in the original slow-side bundle. The branch is faster, so the slow side bundle branch becomes the fast side bundle branch, and the original side bundle branch block (for example, the left side) is changed to the contralateral bundle branch block pattern (right side); B. The original slow side bundle branch The early capture occurred due to the abnormal conduction of the original slow-side bundle branch; C. When the original bilateral bundle branch was 1:1 down-conducting, the original fast-side bundle branch suddenly had conduction interruption, and the excitement suddenly abruptly The slow side bundle branch is transmitted downward, so the original left bundle branch block pattern suddenly changes to the right bundle branch block pattern.

7 The change of heart rate within a certain range can cause the degree of retardation of one or both bundle branches or the above various factors to change accordingly, thereby causing the looming or backward direction of the dependence phenomenon.

Diagnosis and diagnosis of bilateral bundle branch block

Diagnosis is based on clinical performance and examination.

At the time of identification, it should be observed that when the PR interval on the electrocardiogram, the ratio of the atrioventricular and the variability of the QRS waveform are large, it is helpful to diagnose the incomplete bilateral bundle branch trunk block.

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