Right bundle branch block

Introduction to right bundle branch block Right bundle branch block (right bundle-branch block, RBBB) is referred to as right bundle branch block. The right bundle branch block itself does not produce significant hemodynamic abnormalities, so it is often asymptomatic in clinical practice. If symptoms appear, they are mostly symptoms of the primary disease. basic knowledge The proportion of illness: 0.003%-0.005% (the incidence rate of middle-aged and elderly people over 50 years old is about 0.4%-0.5%) Susceptible people: no special people Mode of infection: non-infectious Complications: left bundle branch block

Right bundle branch block

(1) Causes of the disease

Right bundle branch block can be seen in normal people, but less, more children and young people, with incomplete right bundle branch block is more common, about 1% of normal young people have incomplete right bundle branch block Incomplete right bundle branch block patients can be found in congenital heart disease, especially in atrial septal defect, can also be seen in ventricular septal defect with biventricular enlargement, pulmonary venous malformation, etc.; patients with rheumatic heart disease mitral stenosis One third can occur, and incomplete right bundle branch block often occurs in the following pathophysiological conditions:

1 congenital cardiovascular malformation;

2 parts of coronary heart disease and cardiomyopathy;

3 parts of chronic lung disease, mild right ventricular hypertrophy or dilatation;

4 part of healthy people, mostly young people, incomplete right bundle branch block may be due to damage to the distal bundle of distal fiber, and the ventricular septum and right ventricular depolarization is normal.

The incidence of complete right bundle branch block is 0.25% to 1.0%. Most patients with complete right bundle branch block have organic heart disease, such as coronary heart disease, hypertensive heart disease, rheumatic heart disease, and myocardium. Disease, pulmonary heart disease, congenital heart disease, hyperkalemia, Lev disease, Lenegre disease or open heart surgery, the incidence of complete right bundle branch block in acute myocardial infarction is 3% to 7% Mainly occurring in the anterior wall of myocardial infarction, mostly proximal anterior descending artery occlusion, complete right bundle branch block often occurs in the following pathophysiological conditions:

1 myocardial ischemia caused by coronary arteriosclerosis;

2 right ventricular dilatation or hypertrophy;

3 chronic inflammation of the heart muscle;

4 conduction beam non-specific fibrosis bundle branch tissue sclerosis, degenerative lesion fibrosis, electrocardiogram evolution can be seen in these patients mostly have right bundle branch block, then combined with left anterior branch block, and then developed into a high degree of atrioventricular block With third-degree atrioventricular block (ie, complete bilateral bundle branch block), this lesion develops very slowly, often for many years to develop from a single bundle branch block to a bilateral bundle branch block, more common in Middle-aged and elderly patients;

5 a few fully healthy people.

(two) pathogenesis

The right bundle branch of the normal heart is about 16% longer than the left bundle branch. In the refractory period of each branch, the right bundle branch is the longest, followed by the right bundle branch > the left anterior branch > the left posterior branch > the left spacer branch. At the conduction velocity, the left bundle branch and the right bundle branch are normally within about 25 ms, and the QRS waveform is normal.

When the right bundle branch refractory period is extended and the conduction velocity is 25 to 40 ms slower than the left bundle branch, the QRS time limit can be slightly widened, showing a pattern change of partial conduction block, that is, an incomplete right bundle branch block is generated, such as When the temperature exceeds 40ms (more than 40~60ms) or the right bundle branch block conduction is interrupted, the QRS wave time limit is significantly widened (time limit 120ms), that is, complete right bundle branch block is generated.

Right bundle branch block prevention

1. Active treatment of the cause, such as treatment of coronary artery disease, hypertension, pulmonary heart disease, myocarditis, etc., can prevent the occurrence and development of indoor block.

2. Appropriate work and rest, diet, holidays, and appropriate physical exercise.

Right bundle branch block complication Complications left bundle branch block

There are generally no serious clinical complications.

Right bundle branch block symptoms Common symptoms Conduction block ECG abnormal QRS wave width deformity

The right bundle branch block itself does not produce obvious hemodynamic abnormalities, so it is often asymptomatic in clinical practice. If symptoms appear, it is mostly the symptom of the primary disease.

1. Complete right bundle branch block: The QRS wave of V1, V2 lead (or V3R, V4R) is rSR' type or wide and notched R wave, V5, V6 lead S wave is significantly wide, QRS time limit 0.12s, V1, V2 lead ST segment depression, T wave inversion; V5, V6 lead ST segment elevation, T wave erect, I, aVL and II lead are mostly wide and not deep S wave.

2. Incomplete right bundle branch block: except for the QRS wave time limit <0.12s, the other features are the same as complete right bundle branch block.

Right bundle branch block

There are many corresponding laboratory changes in the primary disease.

Mainly rely on ECG examination and diagnosis.

Complete right bundle branch block

(1) Typical ECG characteristics of complete right bundle branch block:

1 The QRS wave of the right chest V1, V2 lead (or V3R, V4R lead) is rsR', rSR' type, rsr' type or M type, and its R' wave is usually higher than r wave; a few are broad and have a notch R wave.

2V5, V6 lead S wave is significantly wide, time limit 0.04s, but not deep, III, aVR lead is qR wave, the R wave is widened and not high, I, aVL and II lead are mostly wide and not deep S wave.

The 3QRS time limit is 0.12s.

When the 4V1 and V2 leads have a notched R wave, the R peak time (wall activation time) is >0.05s, while the V5 and V6 lead R peaks are normal.

5ST-T changes, the direction is opposite to the direction of the QRS wave terminal vector, that is, the ST segment of the V1, V2 lead is depressed, the T wave is inverted, and the ST segment of the V5, V6 lead is raised, and the T wave is erect.

(2) A detailed description of a typical electrocardiogram of a complete right bundle branch block:

The 1QRS time limit is 0.12s, generally not more than 0.14s.

2 Generally, when the frontal QRS axis is measured, the QRS wave is not blocked, that is, the QRS wavefront 1/2 voltage is measured. The frontal QRS axis is usually in the normal range. If the axis is significantly offset, the combined branch conduction should be considered. Blocking.

The 3aVR lead QRS wave terminal is always upright, the aVL lead is always down, and the II, III, aVF lead QRS wave terminal can be upright or inverted.

4ST-T changes are generally not considered as a diagnostic criterion for complete right bundle branch block.

2. Incomplete right bundlebranch block (IRBBB)

(1) Characteristics of typical ECG with incomplete right bundle branch block:

1 The QRS wave of the right chest lead V1, V2 lead is rsR' type, rsr' type, rSR' type or M type, and its R' wave is usually higher than r wave.

2V5, V6, I lead S wave widened without deep.

The 3QRS time limit is <0.12s.

(2) A detailed description of the characteristics of a typical electrocardiogram of incomplete right bundle branch block:

1 may be associated with secondary ST-T changes, but is generally not used as a diagnostic criterion for incomplete right bundle branch block.

2 In practice, it is often encountered that only the right chest lead leads to a time limit of less than 0.12 s rsr' wave group, other leads are correspondingly changed but not obvious, such as the left chest lead is not blunt S The wave, or V1 lead, is of the Rsr' type.

3 Normal variation is mostly related to the physiological delayed depolarization of the right ventricular outflow tract.

4 Another ECG change of normal variation is: V1, rVL wave in aVL lead; S wave in I, II, III, V6 lead, this SI, SII, SIII pattern is seen in patients without heart disease, and on the room Remote depolarization related.

3. Special type of right bundle branch block ECG

(1) Intermittent right bundle branch block (intermitent RBBB):

1 heart rate-independent intermittent right bundle branch block: this type of intermittent right bundle branch block has nothing to do with the heart rate, and the right bundle branch block (complete or incomplete block) can be seen on the continuous ECG recording. Sometimes disappears, regardless of heart rate, the RR interval of the right bundle branch block pattern is equal to or close to the RR interval of the normal QRS-T wave group, and the ventricular rate is mostly in the normal range. This type of intermittent right bundle branch The block is actually a second degree II right bundle branch block.

2 Frequency-dependent intermittent right bundle branch block: including fast frequency, slow frequency and mixed frequency dependent right bundle branch block.

(2) Venturi phenomenon of right bundle branch block: second degree type I right bundle branch block.

The diagnostic criteria for ECG are:

1 very regular sinus (or other supraventricular) heart rhythm;

2 very regular atrioventricular conduction time (PR interval);

A QRS wave with a relatively normal shape appeared in 3 cycles;

4 If the successive QRS waves show that the bundle branch block is gradually aggravated, it can be diagnosed as a direct display of the Venturi phenomenon;

5 In addition to the first heart beat, if all other heart beats show a complete bundle branch block pattern, it is speculated that there is an incomplete occult Venn phenomenon.

The left and right bundles can be divided into the following three types:

1 Directly display the left or right bundle branch Venus phenomenon: manifested as a set of QRS wave beat-by-pulse widening to complete bundle branch block diagram.

2 Incomplete occult bundle branch Nevin's phenomenon: the first QRS wave in a group of heart beats is normal, and the rest are complete bundle branch block diagram.

3 Complete occult bundle branch Nevin's phenomenon: usually can not be distinguished from complete bundle branch block, unless the heart rate slows down enough to form a direct or incomplete occult phenomenon, it is suspected that this possibility Sex.

(3) Second degree type II (Mohs type II) right bundle branch block: ECG shows a certain proportion of the pattern without right bundle branch block and complete right bundle branch block pattern intermittent or alternating Appearance, for example, 2:1 second degree type II right bundle branch block, ECG showed that QRS wave without a right bundle branch block alternates with a QRS wave with a complete right bundle branch block. Another example is the 4:3 second degree type II right bundle branch block, the electrocardiogram shows that the QRS wave without the right bundle branch block alternates with the QRS wave of a complete right bundle branch block.

(4) Occult right bundle branch block: It means that there is no right bundle branch block pattern on the surface electrocardiogram. Only the artificial beam method can display the right bundle branch block pattern. The methods are as follows:

1 random exercise or action test: due to exercise, the heart rate is increased and the right bundle branch block pattern appears. There are two reasons: one is that the myocardium has no ischemia, only because the agitation occurs prematurely in the pathological refractory period that has been prolonged. For the fast frequency-dependent intermittent right bundle branch block, the right bundle branch block pattern disappears after the heart rate is slowed down: the second line of exercise causes myocardial ischemia or aggravates the damage and increases the heart rate. .

2 drugs: with atropine or isoproterenol can stimulate the emergence of right bundle branch block diagram.

The compensatory intermittent period after the contraction of the 3rd stage and the application of propranolol and other slowing the heart rate can make the original right bundle branch block pattern disappear and turn into the occult right bundle branch block.

(5) Orthostatic right bundle branch block: Right bundle branch block pattern appears in standing position or lying position. The right lateral branch branch block is associated with vagal nerve excitability, and there is no organic heart. When the disease is changed to sitting position, the sympathetic nerve excitability is increased, the heart rate is accelerated, the refractory period is shortened, the conduction function is improved, and the right bundle branch is restored to normal conduction.

(6) Complete right bundle branch block combined with right ventricular hypertrophy: The diagnosis of right ventricular hypertrophy by electrocardiogram alone has certain difficulties. The characteristics of right bundle branch block combined with right ventricular hypertrophy are:

1 Incomplete right bundle branch block, R'V1>1.0mV; complete right bundle branch block, R'V1>1.5 mV;

2 The electric axis is right-biased, often +110°;

3SV5, V6 often exceeds RV5, V6, Huang Wan, etc. The voltage of R'V1 is >1.5 mV, and most of them have right ventricular hypertrophy: on the contrary, there is no right ventricular hypertrophy, R'V1 is rarely >1.5mV, except for considering R'V1 And the voltage increase of SV5, if there is obvious right deviation of the ECG axis, more than 90% can be correctly diagnosed as right bundle branch block combined with right ventricular hypertrophy.

(7) Right bundle branch block combined with left ventricular hypertrophy: Because the two do not affect each other, the ECG has the conditions for diagnosing right bundle branch block and left ventricular hypertrophy. The heart vector diagram shows the right bundle branch resistance. The stagnation pattern is accompanied by the characteristic that the mid-term part of the QRS ring shifts significantly to the left due to left ventricular hypertrophy. The T-ring can be located in the left front or in a clockwise direction.

(8) Right bundle branch block combined with myocardial infarction: ECG also shows two patterns of myocardial infarction and right bundle branch block, which can clearly diagnose myocardial infarction because the initial depolarization vector of right bundle branch block is the same as normal It only changes at the back of the vector loop: in the case of myocardial infarction, the QRS vector changes from 0.03 to 0.04 s at the beginning, so the two can be displayed separately.

In the anterior wall myocardial infarction, if the ventricular septum is not involved, the right anterior precordial lead, such as the V3R, V1, V2 leads, still shows the right bundle branch block pattern, showing the rsR' wave, but from the V3 lead to the left In each of the pre-cardiac lead leads, a large q-wave reflecting the initial 0.03 to 0.04 s vector of the abnormality appears, so both sets of figures show that the anterior wall myocardial infarction can still be clearly diagnosed.

In the anterior wall myocardial infarction with right bundle branch block, most of the interventricular septum will be involved. At this time, the normal left-to-right initial interventricular septal depolarization vector disappears, and the electrocardiogram V3R, V1, V2 leads r The wave also disappears, and a large qR wave appears; there is an abnormal Q wave in the lead in the left anterior region, and the R wave is reduced. Due to the right bundle branch block, there is still a large S wave after the R wave, and the ST segment and the T wave change. , the same as the change of general myocardial infarction.

In the inferior myocardial infarction with right bundle branch block, the II, III, aVF leads have myocardial infarction, and the precordial lead still shows the right bundle branch block pattern. The ST segment T wave changes in line with myocardial infarction. which performed.

(9) Covered right bundle branch block: When right bundle branch block combined with left anterior branch block, left bundle branch block, left ventricular hypertrophy, etc., the pattern of right bundle branch block on ECG Atypical, for example, in the pre-cardiac lead is the right bundle branch block pattern, while the standard lead right bundle branch block pattern disappears, showing a pattern similar to the right bundle branch block; or the right anterior branch lead right bundle branch block pattern Disappeared; or right chest lead showed right bundle branch block pattern, left chest lead showed left bundle branch block pattern, etc., the above characteristics are called covered right bundle branch block.

1 left anterior branch block blocks the right bundle branch block:

A. Left anterior branch conduction block makes the standard lead right bundle branch block pattern concealed: at this time, the limb lead is similar to the left bundle branch block, and the chest lead shows a typical right bundle branch block pattern. : Left anterior branch block blocks the right bundle branch block, which is actually an atypical type of right bundle branch block with left anterior branch block. It is due to a strong leftward vector that delays, and simultaneously produces or The right-hand end vector of the right bundle branch block that is almost simultaneously generated partially or completely cancels each other. The left vector includes the left-hand vector generated by the left front branch block, and the degree of block is more obvious. The stronger the left vector, the larger the left axis of the electric axis, the characteristic of the electrocardiogram: the right bundle branch block pattern in the chest lead; the left anterior branch block is characterized by deep SII and SIII, and the III lead has no R' wave. , SI is small or absent, QI may or may not appear; frontal QRS axis is -75 ° ~ 60 °.

B. The left anterior branch conduction block makes the chest lead and right bundle branch block pattern obscured: at this time, the I lead and the V5, V6 lead have no terminal S wave, and the graph is similar to the left bundle branch conduction resistance. The stagnation, the right chest lead shows a right bundle branch block pattern, but sometimes the R' wave of the right chest lead will disappear, but an intercostal trace V1, V3R or V4R will still appear R' wave, The resulting principle is the same as the left anterior branch conduction block, which makes the standard lead right bundle branch block pattern obscured, possibly due to the generation of a strong left rear end vector, the right front end block of the right bundle branch block ( R') is completely offset, and sometimes the pattern of the standard lead and the right lead branch block of the chest lead can be masked at the same time, but it is rare, when the persistent left anterior branch block blocks the right bundle branch block. Left anterior branch conduction block with QRS time widening; right chest lead is rsR' type, similar to right bundle branch block; left chest lead and limb lead are R type, similar to left bundle branch block, left anterior branch The block graphic can present a complete left bundle branch block pattern in the limb lead.

The clinical significance of left anterior branch block to cover right bundle branch block is the same as left anterior branch block with right bundle branch block, but it should be noted that it may be misdiagnosed as simple left anterior branch block or left anterior branch block. Alternate with right bundle branch block and neglect the possibility of double bundle branch block, in addition, suggesting that may be accompanied by significant left ventricular hypertrophy, or left ventricular sidewall block (infarct or myocardial fibrosis), Therefore, it should be well identified.

2 left bundle branch block blocks the right bundle branch block:

A. The right bundle branch block is completely offset by the symmetrical conduction block of the left bundle branch. At this time, the degree, type, proportion of the atrioventricular compartment, length of conduction time, and the simultaneous initiation of conduction of the left bundle branch block The right bundle branch block is completely consistent, and the electrocardiogram shows a normal QRS-T wave. The PR interval can be extended by different degrees depending on the left or right bundle branch conduction time. If the left and right bundle branches have conduction interruption at the same time. (Bundle leakage), can produce ventricular leakage.

B. The right bundle branch block is completely concealed by the asymmetry of the left bundle branch and is a block diagram of the left bundle branch block. The length of the PR interval depends on the conduction time of the right bundle branch. It can be normal or prolonged. If the left and right bundle branches are interrupted at the same time, ventricular leakage can occur.

3 left ventricular hypertrophy masks right bundle branch block: its electrocardiogram has the following manifestations due to the difference in the degree of the two.

A. Left ventricular hypertrophy masks the QRS-T abnormality of the right bundle branch block: At this time, the electrocardiogram of left ventricular hypertrophy is as follows: the S wave of the V1 lead is very deep, and the rsR' pattern of the right bundle branch is converted into the rsr' pattern. At this time, the pseudo right bundle branch block caused by the depolarization of the pulmonary artery cone should be excluded. The R wave of the V5 lead is >2.5mV, and the ST segment of the V5 and V6 leads does not rise, but decreases, and the T wave is flat or Inversion; chamber wall activation time of V5 lead>0.05s; ST segment of V1 lead does not decrease, T wave is erect; RII RIII>2.5mV: ECG axis is close to left, about 0°.

B. Left ventricular hypertrophy is masked, and only the right bundle branch block pattern appears: Since the QRS ring area generated by the right bundle branch block is large, the left ventricular hypertrophy must be quite significant, so that the ECG can partially conceal each other. For example, when the right bundle branch block is blocked, the ST segment of the V1 lead is depressed, the T wave is inverted, the ST segment elevation of the V5 and V6 leads, and the T wave is erect; while the left ventricular hypertrophy, the ST segment of the V1 lead is elevated. The T wave is upright, the ST segment of the V5 and V6 leads is depressed, and the T wave is inverted. At this time, the two cancel each other out, but the main abnormality of the right bundle branch block is the additional ring of the terminal vector (ie, the third vector of the ventricular depolarization). Pointing to the right front; and the main abnormality of left ventricular hypertrophy is that the main vector increases to the left (ie, the second vector of ventricular depolarization). When the right bundle branch block is combined with left ventricular hypertrophy, the QRS initial vector is normal, and the QRS ring main vector Especially after 0.06s, it is more significantly biased to the left and the upper than the right bundle branch block. The terminal vector is the additional ring to the right. The ST-T vector is opposite to the left ventricular hypertrophy due to the right bundle branch block. Changes cancel each other out, can be close to normal or slightly left or right, pass When left ventricular hypertrophy with right bundle branch block, deep S wave and R-wave high V5 leads LVH presented in V1, and the like may still be retained.

Type 4B pre-excitation syndrome masks right bundle branch block: Type B pre-excitation syndrome can completely obstruct the right bundle branch block, or make the right bundle branch block become atypical.

3. Characteristics of His bundle beam diagram of right bundle branch block

(1) The time of the V wave is 0.12 s, indicating that the ventricular depolarization time is prolonged.

(2) The time of AH and HV is normal, indicating that the conduction time from the atrioventricular node His bundle to the left bundle branch is normal. If the HV time is prolonged, it means that the transmission through the left bundle branch is also delayed.

(3) The left bundle branch potential was recorded through the left ventricle, and the right bundle branch potential was recorded by the His bundle beam electrode to confirm the right bundle branch block.

Diagnosis and differentiation of right bundle branch block

diagnosis

Mainly rely on ECG examination and diagnosis.

Differential diagnosis

1. Identification of complete right bundle branch block and right ventricular hypertrophy

(1) The main features of ECG in right ventricular hypertrophy are:

The 1V1 lead QRS wave is R type, RS type, qR type. If r wave is more Rsr' type, R wave can be up to 1~1.5mV, chamber wall activation time is <0.06s (more than 0.03~0.05s).

2V5, V6 lead R / S 1.

The 3QRS time limit is <0.12s.

4 The frontal electric axis is about 110°.

5 clinical causes of right ventricular diastolic overload, such as atrial septal defect.

(2) The main features of complete right bundle branch block ECG are: V1 lead QRS is more rSR' type, no q wave, R' wave <1.5mV, wall motion time > 0.06s.

2. Identification of complete right bundle branch block and myocardial infarction

Complete right bundle branch block usually does not affect the diagnosis of myocardial infarction such as anterior wall, anterior wall, and anterior wall, but affects the electrocardiogram of the posterior wall myocardial infarction. The inferior myocardial infarction pattern can be slightly affected, and the false positive rate is about At 3%, when the posterior wall myocardial infarction spreads to the inferior wall and anterior wall, the R wave of V4V6, I and II, III, aVF leads disappears abnormally, and the pathological Q wave and other ECG changes are one. A reliable diagnostic indicator, pulmonary heart disease with complete right bundle branch block, V1, V2, II, III, aVF lead can appear Q wave, which is related to right ventricular hypertrophy of pulmonary heart disease, not caused by myocardial infarction Q wave.

3. Incomplete right bundle branch block and differential diagnosis of posterior wall myocardial infarction

In the posterior wall myocardial infarction, the R wave of the V1 lead is increased, but occasionally it can be expressed as rSr' type. Compared with the rSr' wave of incomplete right bundle branch block, the V1 lead T wave is erect. More common, T wave inversion is only seen in the early stage of acute positive posterior myocardial infarction, such as the presence of II, III, aVF lead pathological Q wave, also supports the diagnosis of positive posterior myocardial infarction.

4. Incomplete right bundle branch block and identification of straight back syndrome and funnel chest electrocardiogram

In the straight back syndrome and the funnel chest, the position of the heart changes correspondingly due to the change of the anteroposterior diameter of the thorax. The rSr' type can appear on the V1 lead, the general r' wave is small, and the P1 inversion of the V1 lead is similar to the left. The P wave inversion caused by atrial enlargement is not difficult to distinguish from the simple incomplete right bundle branch block.

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