left posterior fascicular block
Introduction
Introduction to left posterior branch block Left posterior branch block (LPH) is also called left posterior block. Left posterior branch block itself has no obvious symptoms, such as its combined right bundle branch block, there will be syncope, convulsions and so on. basic knowledge The proportion of illness: 0.001% Susceptible people: no specific population Mode of infection: non-infectious Complications: syncope, convulsions and convulsions
Cause
Left posterior branch block
(1) Causes of the disease
The common cause of left posterior branch block is coronary heart disease. The incidence of myocardial infarction is about 1%, because multiple vascular occlusions lead to anterior wall combined with inferior wall and right ventricular infarction, or anterior descending branch lesions lead to wide interventricular septum. Ischemia, necrosis can occur, and rarely appear alone, other hypertension, cardiomyopathy, myocarditis, aortic valve disease or degeneration of the indoor conduction system, dissection aneurysm, acute pulmonary heart disease, aortic arch constriction , high blood potassium, etc., can also be found in healthy people.
(two) pathogenesis
The left posterior branch block is less common than the left anterior branch block because the left posterior branch is shorter and thicker, about 20 mm long, and about 6 mm thick. The blood supply comes from the left and right coronary arteries of the left coronary artery, with a double blood supply; The branch is located in the left ventricular inflow tract which is not easily invaded. It is lightly impacted by the blood flow. Once the left posterior branch has a conduction block, it often indicates a wide and serious lesion. It also indicates that there is a right bundle or a right bundle. The conduction damage of the left anterior branch is less common in the left posterior branch.
Prevention
Left posterior 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.
Complication
Left posterior branch block complication Complications, syncope, convulsions and convulsions
If the right bundle branch block is combined at the same time, syncope, convulsions, etc. may occur.
Symptom
Left posterior branch block symptoms common symptoms convulsion conduction block syncope
Left posterior branch block itself has no obvious symptoms, such as its combined right bundle branch block, there will be syncope, convulsions and so on.
Examine
Left posterior branch block
The corresponding laboratory test results for the primary disease may change.
1. ECG examination features
(1) Typical ECG characteristics of left posterior branch block:
1QRS electric axis is right +90°+180°.
2I, aVL lead is rS type, II, III, aVF lead is qR type, q wave <0.02s, showing SIQIII type.
3QRS does not widen or slightly widen, and the time limit is <0.12s.
The R wave of the 4II, III lead is relatively high, RIII>RII.
There is no significant change in the QRS wave of the pre-cardiac lead. The V1 lead can be QS type, and the V2 lead can be rS type.
6 Exclude other causes that cause the motor shaft to be significantly right-handed.
(2) A detailed description of the typical ECG of the left posterior branch block:
1 Regarding the QRS electric axis right deviation value, each report is not completely the same, some people think that it is +90°~+120°; some people think that the left rear branch block should be considered when >+90°, and it can be diagnosed when >+120° For the left posterior branch block, but most people think that the QRS wave should also be used for diagnosis.
The 2V1 lead is QS or rS type, and the V5 and V6 leads often do not have q waves, because the QRS vector loop of the left posterior branch block has only characteristic changes on the frontal surface, but there is no obvious change in the horizontal plane, so the chest The lead-lead ECG has no special performance, but if it is traced at a lower level, q waves may appear, and V5 and V6 leads have deep S waves.
3 ECG shows that when the QRS electrocardiogram axis is significantly right-sided, it is necessary to combine the clinical diagnosis to determine the diagnosis. The following should be noted:
A. In the right ventricular hypertrophy, emphysema, pulmonary heart disease, significant infarction of the pulmonary infarction, extensive anterior wall myocardial infarction and other diseases, the ECG axis can appear right deviation, can also be seen in healthy young people and slimming Should be identified.
B. In the elderly, especially those with hypertension, coronary heart disease or left ventricular hypertrophy, the ECG axis should not be right-biased. If the ECG axis is >90°, the left posterior branch block should be considered. Diagnosis can be made when the ECG axis is >120°.
C. When an adult suffers from coronary heart disease, high blood pressure, etc., there is a significant right deviation of the electrocardiogram axis, and there is no other cause that causes the right axis of the electric axis to be considered as left posterior branch block.
D. When the extensive anterior wall myocardial infarction is accompanied by the right deviation of the electric axis, because the infarction of the site itself can cause the right axis of the electrocardiogram, at this time, the I, aVL lead is QS type, so it must be carefully diagnosed.
4 The following dynamic observation of ECG performance can help diagnose:
A. If the SIQIII waveform appears intermittently and the ECG axis is about 120°, the left posterior branch can be clearly diagnosed.
B. If the electrocardiogram axis of the original SIQIII is gradually shifted from the normal normal (such as 130 ° ~ 60 °) to about 120 °, and the QRS time limit is slightly wider than the previous 0.02 s, then the diagnosis is left Branch block, if the heart axis suddenly turns to normal, the diagnosis can be further confirmed.
C. If the following changes are found, the left rear branch block may be prompted or suspected:
a. The original SIQIII pattern that appears as a normal ECG axis, in the dynamic observation, found that the ECG axis is gradually right-biased, increasing by 60° or more, whether or not it reaches 120° (possibly at 90°).
b. For SIQIII graphs with 120° ECG axis, the amplitude of QRS wave is gradually increased or abruptly increased in dynamic observation, and the amplitude of R wave in II, III, avF leads is increased, I, the lead of AVL leads The wave deepens, but the ECG axis is no longer further right.
c. In the dynamic observation, it can be found that when the above-mentioned changer increases the ventricular rate or is accompanied by a slightly wide QRS wave (about 0.02 s), the possibility of left posterior branch block is increased, and the mechanism is accelerated. It can cause 3-phase block of the left posterior branch or differential differentiation of the left posterior branch type.
D. In patients with left ventricular organic heart disease, there is a SIQIII pattern with an ECG axis of about 120° on the ECG. It is more likely to diagnose left posterior branch block because of left ventricular disease (more with left ventricular hypertrophy). The presence of the left-sided ECG vector offsets the right-most ECG vector caused by the extremely significant eccentric heart, emphysema, pulmonary heart disease, right ventricular hypertrophy or extensive lateral myocardial infarction. The 120° ECG axis is caused by the left rear branch block.
(3) Special types of left rear branch block:
1 second degree type I left posterior branch block: similar to the second degree type I left anterior branch block, which is characterized by periodic QRS electric axis right stroke, with corresponding QRS wave shape, amplitude change, also divided into 3 kinds The type, that is, the direct display of the Venturi type left posterior branch block, the incomplete occult Vengen type left posterior branch block and the completely occult Vengen type left posterior branch block.
2 second degree type II left posterior branch block: manifested as intermittent or alternating left posterior branch block pattern, no frequency dependence.
3 left posterior branch block to cover the inferior myocardial infarction: acute inferior myocardial infarction, can destroy a large number of left posterior branch fibers, then II, III, aVF lead can appear Q wave wide 0.04s, QRS wave width can also reach Above 0.12s, the R wave amplitude also increased, and this inferior wall infarction combined with left anterior branch block.
4 Intermittent left posterior branch block: This has nothing to do with the heart rate. On the electrocardiogram, the left posterior branch block appears and disappears.
3. ECG vector characteristics
(1) The starting vector is to the left, forward and upward, and the frontal ring is indexed in the clockwise direction.
(2) After the start vector is the left ventricle and the posterior stimuli, and the ring expands downward to the right.
(3) Because the posterior and posterior ventricle of the left ventricle is delayed, the terminal vector conduction is delayed, facing the lower right, thus forming the right axis of the electric axis, but the simple left posterior branch block is less. The diagnosis should exclude the right ventricular hypertrophy, chronic Pulmonary heart disease and lateral myocardial infarction.
4. His bundle beam characteristics: If only the left posterior branch is blocked, the AH and HV intervals are in the normal range, that is, the excitement transmits the His bundle from the atrioventricular node, and reaches the ventricle through the right bundle branch and the left anterior branch. Prolonged HV interval, suggesting left posterior branch block with left anterior branch and right bundle branch incomplete block.
Diagnosis
Diagnosis of left posterior branch block
According to the left posterior branch block ECG features: QRS wave ECG axis is about 120°, SIQIII type, QRS wave time limit does not exceed 0.10s, exclude other causes that the motor axis is significantly right deviation, continuous dynamic observation of ECG changes can only Diagnosis, simple left posterior branch block is less common, but can form a double bundle branch block or a three bundle branch block with the right bundle branch, left anterior branch or septal branch block, so special attention should be paid to the diagnosis to avoid missed diagnosis. In addition, according to the ECG vector diagnostic criteria.
Differential diagnosis
1. Identification of left posterior branch block and inferior myocardial infarction: When left posterior branch block, II, III, aVF lead R wave is very high, q wave is small, time <0.02s; and inferior myocardial infarction , II, III, aVF leads appear wide and deep Q waves, r waves are very low or disappear.
2. Distortion of left posterior branch block and anterior wall myocardial infarction: anterior wall myocardial infarction may have right axis deviation, but pathological Q wave appears on the corresponding lead, while left posterior branch block has electric axis Right deviation (about 120 °), but no pathological Q wave.
3. Identification of left posterior branch block and right ventricular hypertrophy: ECG II lead of right ventricular hypertrophy is RS type, R wave is equal to S wave, chest lead has right ventricular hypertrophy pattern, left posterior branch block II lead The qR type, the chest lead QRS complex is normal.
4. SIQIIITIII syndrome: In the case of pulmonary infarction, it can be expressed as SIQIIITIII pattern, which is called functional left posterior branch block.
