bifascicular block
Introduction
Introduction to double branch block The indoor conduction system is a three-branch system, namely the right bundle branch, the left anterior branch, and the left posterior branch. The combination of any two of these three branches is called double branch block, referred to as bifascicular block. basic knowledge The proportion of illness: 0.002% Susceptible people: no special people Mode of infection: non-infectious Complications: A-S syndrome, sudden death
Cause
Double branch block cause
(1) Causes of the disease
1. Right bundle branch block combined with left anterior branch block common cause coronary heart disease, the incidence rate is as high as 40% ~ 60%, the incidence of acute myocardial infarction is 5% ~ 7%, Beijing area reported right bundle branch block combined with left anterior branch Blocking accounted for 23.8%, hypertensive heart disease was 20% to 25%. Because aortic valve calcification can affect these double branches, the incidence of block is also high, Lev's disease and Lenègre's disease The incidence rate is 23%. In addition, it can also be seen in cardiomyopathy, endocardial pad defect, ventricular septal defect, tetralogy of Fallot and other congenital heart diseases, and after cardiac surgery (such as mitral valve replacement) , after coronary artery bypass surgery, etc.).
2. Right bundle branch block combined with left posterior branch block is similar to the right bundle branch block combined with left anterior branch block, mainly seen in coronary heart disease, acute myocardial infarction, in anterior wall myocardial infarction complicated with bundle branch block, Reported in Beijing only 2.4%, the incidence of acute myocardial infarction <0.8%, in addition to extensive anterior wall myocardial infarction, lower, posterior wall combined with right ventricular infarction, or anterior wall combined with inferior myocardial infarction can also occur, autopsy It is reported that myocardial infarction occurs in almost all or most of the patient's ventricular septum. There are often double or three coronary artery lesions, left anterior descending artery, and right coronary artery often with severe stenosis. Therefore, the mortality rate is high, followed by hypertensive Heart disease and cardiomyopathy, indoor conduction system fibrosis, degeneration and so on.
3. Left anterior branch block combined with left posterior branch block is also called branch left bundle branch block. The etiology is the same as that of right bundle branch block combined with left anterior branch block, mostly caused by organic heart disease.
4. Left anterior branch block combined with left middle septum block because ischemic heart disease is the most common cause of left anterior branch and left mediastinal branch. Fibrosis with different degrees of septum is also a common cause of middle-aged and elderly people.
(two) pathogenesis
1. Right bundle branch block combined with left anterior branch block The right bundle branch and the left anterior branch are in the anterior chamber septal area. The two are very close, and both receive blood from the left anterior descending coronary artery. Therefore, if the anterior chamber is separated from the left ventricle and left ventricle When the anterior wall has lesions, it is easy to involve and damage both the right bundle branch and the left anterior branch. The pathological features are mostly myocardial fibrosis, degeneration or necrosis.
2. Right bundle branch combined with left posterior branch block because the right bundle branch and the left posterior branch are not as close as the right bundle branch and the left anterior branch in the anatomical position, but are far apart. In addition, the left posterior branch is a dual blood supply, which is itself There are fewer chances of loss, so the right bundle branch and the left posterior branch are less likely to be injured at the same time, so the incidence is much less than that of the right bundle branch block combined with the left anterior branch block. It is a rare double branch block. However, once it appears, it indicates that the myocardium and/or the conduction system are extensively and severely damaged.
Prevention
Double 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.
Complication
Double branch block complication Complications
When developing a complete atrioventricular block, serious complications such as syncope, A-S syndrome and sudden death may occur.
Symptom
Double branch block symptoms common symptoms sudden death syncope
1. Right bundle branch block combined with left anterior branch block itself has no obvious symptoms, but may develop syncope when developing complete atrioventricular block, A-S syndrome, sudden death, etc. due to multi-organism Heart disease, so the symptoms of the primary disease can occur.
2. The right bundle branch block combined with the left posterior branch block has no obvious symptoms. If the patient develops a high or third degree atrioventricular block, the symptoms caused by the latter can occur. In addition, the symptoms of the primary disease are mainly caused.
Examine
Double branch block check
Changes in the results of laboratory tests related to the primary disease may occur.
Electrocardiogram examination
(1) Characteristics of electrocardiogram of right bundle branch combined with left anterior branch block:
1 right bundle branch block graphic:
A. V1, V2 lead is rsR', rSR', rsr' or M type QRS wave, R' wave is usually higher than r wave (even can be wide and notched R wave).
The B.I, V5, and V6 leads are RS type, and the S wave is widened (the adult S wave is wider than the R wave, or S>40 ms).
C. QRS time limit 0.12s.
2 left front branch block features:
A. The left axis of the electric axis is -45° to -90°.
The B.aVL lead is of the qR type, and the II, IIIaVF is of the rS type.
(2) Four types of electrocardiogram:
1 Persistent right bundle branch block combined with persistent left anterior branch block: persistent double branch block.
2 Persistent right bundle branch block combined with intermittent left anterior branch block: ECG showed right bundle branch block and left anterior branch block with right bundle branch block appeared alternately in turn.
3 intermittent right bundle branch block combined with persistent left anterior branch block: ECG showed left anterior branch block and left anterior branch block with right bundle branch block alternately appear alternately.
4 intermittent right bundle branch block combined with intermittent left bundle branch block: intermittent double branch block, ECG showed normal ECG, right bundle branch block, left anterior branch block, right bundle branch block combined with left anterior branch The four types of graphics are blocked from time to time and appear alternately in turns.
(3) Special types of electrocardiogram:
1 When the right bundle branch block and the left anterior branch block, there is a deep S wave of I lead, even with the right axis of the electric axis, which can be seen in:
A. The right bundle branch block is heavy and the left anterior branch block is light.
B. Right bundle branch block with second degree type II left anterior branch block, which is easy to occur in the dwarf patient with the transverse clock direction of the transverse heart. When the I lead S wave is too deep, the ECG axis is right. Partially leading to the combined left anterior branch block is easily missed.
2 When the right bundle branch block and the left anterior branch block, the S-wave of I lead becomes smaller or disappears: When the right bundle branch block is accompanied by severe left anterior branch block, severe left anterior branch block can lead to the left ventricle. The right-to-left QRS terminal vector mostly cancels the left-to-right additional ring vector of the right bundle branch block, making the I-lead S-wave smaller or disappear, resulting in a right-branch block diagram on the limb lead. It becomes atypical, even similar to the left bundle branch block pattern, which is a complete right bundle branch block with a "limb lead disguised as a left bundle branch block." Sometimes the S wave of the V5 and V6 leads disappears. The degree of S-wave cancellation is positively correlated with the degree of left anterior branch block.
3 camouflage bundle branch block: is a typical ECG change of right bundle branch block combined with left anterior branch block, also known as right bundle branch block with camouflage left bundle branch block, it is right bundle branch block combined Left anterior branch block or indoor terminal conduction delay or left ventricular hypertrophy or anterior wall myocardial infarction, and most of them are caused by right bundle branch block combined with left anterior branch block, camouflage bundle branch block There are two types:
A. Standard lead camouflage bundle branch block: ECG features: a. The right anterior lead is a right bundle branch block pattern, b. The limb lead is a left bundle branch block pattern: with left anterior branch block Some performances, such as deep SII, SIII, III lead without R' wave, I lead without S wave or S wave is very small, q wave is optional, c. electric axis is often -60 ° ~ -75 °.
B. Pre-cardiac lead disguise bundle branch block: ECG features: a. Right anterior region lead shows right bundle branch block pattern; b. Left anterior region lead shows left bundle branch block pattern, if heart The anterior lead lead camouflage bundle branch block has no left front branch block, and its QRS axis has no abnormal left deviation.
Both types can appear on the same electrocardiogram, and the high left anterior branch block can offset some of the changes in the right bundle branch block.
4 right bundle branch block combined with left anterior branch block with inferior myocardial infarction: when the right bundle branch block with inferior myocardial infarction pattern II, III lead has a particularly deep Q wave, it is likely to suggest simultaneous left anterior branch resistance Stagnation.
(2) Characteristics of right bundle branch combined with left posterior branch block ECG:
1 chest lead shows right bundle branch block diagram:
A.V1, V2 leads exhibit rsr, rsR, rSR or M-type QRs waves, R waves are usually higher than r waves (even a wide and notched R wave), and S waves are often small.
The B.I, V5, and V6 leads are RS type, the R wave amplitude is low, and the s wave is widened (the adult S wave is wider than the R wave, or S>40 ms, and the terminal part is blurred).
C.QRS time 0.12 s.
The 2-limb lead shows an approximate left posterior branch block pattern:
A. The electrocardiogram axis is +90°+180°, and most of them are around 120° (the right axis of the electric axis caused by other causes should be excluded).
B. Presenting the characteristics of SIQIII, that is, I, aVL lead is rS type, II, III, aVF lead is qR type or qRs type (III, avF lead q wave is necessary) and q wave 0.04s, R wave The end is blunt.
C. II, III, aVF lead R wave amplitude is high: This is one of the typical manifestations of right bundle branch block combined with left posterior branch block, which is the addition of the same QRS vector, emphysema or There is no such manifestation in right ventricular hypertrophy, which means that the degree of left posterior branch block is complete or high, and those with high R wave amplitude are prone to develop third-degree atrioventricular block.
(3) Left anterior branch block combined with left posterior branch block ECG performance can be as follows:
1 presents complete left bundle branch block: when the left anterior branch and the left posterior branch simultaneously have a third degree block, the electrocardiogram presents a complete left bundle branch block pattern, which is difficult to occur with the left bundle branch. The pattern of complete left bundle branch block caused by stagnation, only left anterior branch block or left posterior branch block before and after left anterior branch block and left posterior branch block showed complete left bundle branch block pattern. The pattern, or the left anterior branch block and the left posterior branch block pattern appear alternately to diagnose the left anterior branch block with the left posterior branch block, while the simple complete left bundle branch block has no such performance. Some people think that When the left bundle branch has a three-degree block (ie, the conduction is completely interrupted), its QRS time is often 0.14 s; when the QRS time is between 0.12 and 0.13 s, it is mostly left anterior branch block and left posterior branch block.
2 presents complete left bundle branch block with significant left axis of the electric axis: this is due to severe left anterior branch block than left posterior branch block, but it may also be once left bundle branch block combined with third degree left anterior branch block Caused by.
3 presents complete left bundle branch block with significant right axis deviation: this is due to the severity of left posterior branch block and left anterior branch block.
Regarding the conduction delay of the left bundle branch and the side branch block, whether it can be diagnosed from the electrocardiogram is still inconclusive.
(4) Characteristics of left anterior branch block combined with left middle septum block ECG:
The 1 limb lead showed a left anterior branch block pattern: the I lead was Rs type, the aVL lead was qR type, II, III, and the aVF lead was rS type.
2 The pre-cardiac lead showed that the left middle septum block pattern V1 ~ V6 leads are Rs type: V1 ~ 2 lead R / S > 1, Rv2 > Rv6, V5 ~ 6 lead no q wave.
2. ECG vector map features
(1) Right bundle branch block combined with left anterior branch block ECG vector diagram: it is characterized by the right side of the bundle branch block and the frontal surface block of the left anterior branch block, which does not cover each other.
1 transverse surface: According to the degree of right bundle branch block, the return branch and turn of the QRS ring can be different, as follows:
A. When the right bundle branch block is lighter: the return branch of the ring is also shifted forward, the ring is still in the reverse clockwise direction, and the slow running terminal additional ring is located on the right rear.
B. When the degree of right bundle branch block is heavier: the return branch of the ring moves forward, and can intersect with the centrifugal branch to form an "8" shape.
C. When the right bundle branch block is extremely heavy: the return branch of the ring moves completely to the front of the centrifugal branch, causing the QRS ring to rotate in the clockwise direction, and the slow-moving terminal additional ring is also moved to the right front.
2 frontal surface: QRS ring still has the characteristics of left front branch block, that is, the starting vector is to the right, the ring is reversed clockwise, the ring is expanded to the upper left, and the maximum QRS vector and half-area vector are oriented to the upper left, and the call axis is significant. Left-sided, due to the presence of right bundle branch block, the return branch is slow and tortuous, forming a terminal additional loop.
3 Right side: The QRS ring is located at the front upper side, the starting vector points to the front and the bottom, and the ring is turned counterclockwise. It can also be 8 shaped or clockwise.
4ST, T vector: secondary, facing left, lower rear.
If the left front branch is severely retarded, the QRS vector after 20ms is extremely biased to the left and the upper left, and the maximum vector of the QRS loop appears with a time delay, which can cancel the end-to-right, forward-facing vector generated by the right bundle branch block; If there is a myocardial fibrosis in the inferior wall at the same time, the downward vector in the frontal plane disappears, so the pattern in the limb lead can become the same as that in the left bundle branch block, which is called masked in the limb lead. Right bundle branch block, which is the characteristic of the ECG vector diagram of camouflage bundle branch block.
Right ventricular hypertrophy combined with left anterior branch block can present ECG vector graph similar to the above right bundle branch block with left anterior branch block, but the difference is that the former has no slow running terminal additional ring on all three faces. .
(2) right bundle branch block combined with left posterior branch block ECG vector features: ventricular depolarization order is from the left anterior branch distribution of the myocardium, early and middle depolarization order and simple left posterior branch block Similar, that is, the depolarization vector is shifted from the left front to the right rear; the late depolarization vector is toward the right front, and the simple right bundle branch is the same, so the 0.06s in the middle of the QRS ring, the vector change is the left posterior branch block. Therefore, the change of the terminal vector is caused by the right bundle branch block. The characteristics of the ECG vector diagram are as follows:
1 Horizontal surface: Most of the QRS rings are still turned counterclockwise, or in the shape of "8". The ring body is more prominently forward and rightward, and the terminal ring with slow running is mostly in the right front.
2 frontal surface: QRS ring turns clockwise, the starting vector is more to the left, the ring body is downward, to the right, in the lower right quadrant area > 50% of the total area, the largest vector is downward, right or left, running The slow end attachment loop is mostly at the bottom right, and the QRS main loop will shift significantly in the vertical direction.
3 right side: Most of the QRS ring is below, the steering is uncertain, and the additional ring that runs slowly at the end is mostly in the upper front.
4ST, T vector: secondary, facing left, back, bottom.
(3) Left anterior branch block combined with left septal block block ECG vector features:
1 transverse plane: the left middle septum block diagram, the QRS loop initial vector forward, followed by the leftward, counterclockwise turn, the QRS ring left front quadrant area is greater than 2/3 of the total area, and the terminal vector is at the right rear The T ring turns counterclockwise.
2 frontal surface: the left front branch block pattern, the QRS ring initial vector down, followed by the horizontal leftward counterclockwise turn, the ring body is wide, the main body is in the upper left quadrant, the terminal vector is in the upper right, the running is slightly slow, T The ring turned in a clockwise direction.
3 left side: QRS ring initial vector forward and downward, clockwise rotation, QRS ring body is in front of the top, and more contrary to the normal running direction, QRS ring before the Y axis is larger than 2/3 of the total area, The terminal vector is in the upper rear, the operation is slightly slow, and the T-ring turns counterclockwise, which is opposite to the QRS ring.
Diagnosis
Double branch block diagnosis and identification
diagnosis
According to the relevant clinical manifestations and electrocardiogram, the characteristics of ECG vector diagnosis.
Differential diagnosis
1. Identification of right bundle branch combined with left anterior branch block
Diagnosis of right bundle branch block combined with left anterior branch block should be differentiated from emphysema, thoracic deformity, straight back syndrome, etc. In these diseases, the left axis of the electric axis can be formed, but not the left anterior branch block, and the S wave can be formed. The II lead is deeper than the III lead (SII>SIII), but when the S and S leads of the II and III leads are deep, the right bundle branch block and the left anterior branch block are supported.
2. The diagnosis of right bundle branch block combined with left posterior branch block is difficult
Diagnosis must be made on the basis of exclusion of other causes of right-sided deviation of the ECG axis, such as right bundle branch block with right ventricular hypertrophy or chronic lung disease, elongated body and extensive anterior wall myocardial infarction, severe systolic heart time Identification is more difficult and must be combined with clinical exclusion. If it occurs in hypertension, coronary heart disease, cardiomyopathy, myocarditis, hyperkalemia and certain congenital heart diseases, most of them can be diagnosed, such as abnormal amplitude and duration. A long initial right vector is consistent with a change in heart vector for extensive sidewall myocardial infarction.
