left bundle branch block
Introduction
Introduction to left bundle branch block The incidence of left bundle branch block was 1%. The incidence of bundle branch block increases with age. In a prospective study of 855 male patients who were followed for 30 years, the incidence of left bundle branch block at 50 years was 0.4%, 2.3% at 75 years, and 5.7% at 80 years. There is no significant relationship with ischemic heart disease, myocardial infarction or cardiovascular death. Studies suggest that bundle branch block is very related to age and is a hallmark of degenerative diseases that can affect the slow progression of the heart muscle. However, left bundle branch block may be associated with significant and severe heart disease. basic knowledge The proportion of illness: 0.001% Susceptible people: no specific population Mode of infection: non-infectious Complications: left bundle branch septal branch block
Cause
Left bundle branch block
Disease factor (30%):
Very rarely seen in healthy people, most patients with organic heart disease, the ratio of male to female in complete left bundle branch block is about 2:1, the age of onset is 3 months to 83 years old, and the average age is (56.7±3.2). According to the domestic report, the causes of 137 patients with complete left bundle branch block were reported in the group. Coronary heart disease accounted for 45.3%, hypertension accounted for 19.7%, cardiomyopathy accounted for 8.7%, myocarditis accounted for 3.6%, and pulmonary heart disease accounted for 5.2%. Rheumatic heart disease accounts for 5.8%, congenital heart disease accounts for 0.7%, aortic disease (calcified aortic stenosis) accounts for 1.5%, others (such as Behcet's disease, acute renal failure, brain trauma, hyperthyroidism, nephritis) 9.4%, complete left bundle branch block with heart enlargement accounted for 72.5%, left ventricular enlargement accounted for 41.9%, left and right ventricular enlargement accounted for 2.6%, atrial enlargement accounted for 8.1%: with heart The failure rate accounted for 51.6%, and the heart enlargement without heart failure accounted for 20.9%.
Other factors (30%):
Other causes include Lev disease, Lengere disease, cardiac trauma, open heart surgery, hyperkalemia and quinidine, procainamide, amiodarone, high-dose lidocaine, etc. Left ventricular hypertrophy caused by sexual heart disease, left ventricular dilatation and traction can cause complete left bundle branch block, incomplete left bundle branch block and complete left bundle branch block. The pathological significance of stagnation is similar, except that the lesion is lighter and the left bundle is less damaged.
Pathogenesis
The trunk of the left bundle branch is very short. After the two bundles of fibers are separated from the His bundle, they are fan-shaped under the inferior septum of the left ventricular septum, and the subendocardium of each part of the left ventricle is divided into Purkinje fibers, so the left bundle Blocking of the branch often indicates a wide range of damage. This is because the left bundle is short and the branch is early. The anterior and posterior portions of the trunk receive blood supply from the anterior descending and posterior descending branches of the left coronary artery. Less, when the lesions are more extensive, all of them can be damaged. Therefore, once a complete left bundle branch block occurs, there is more suggestive of organic heart disease. The left bundle branch block is not necessarily the complete left bundle branch conduction system. The rupture may be caused by temporary myocardial ischemia or inflammation. The edema may cause the refractory period of the conductive fiber to be prolonged, or the conduction velocity may be slowed down, so that the left bundle branch block may occur, and the time may be hidden, and may return to normal or permanent. Sexual block, when the undulation period of the left bundle branch is prolonged, and the conduction velocity is significantly slower than the right bundle branch, the left bundle branch block can occur.
Prevention
Left 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.
Complication
Left bundle branch block complication Complications left bundle branch septal block
Left bundle branch septal branch block.
Symptom
Left bundle branch block symptoms common symptoms left ventricular hypertrophy angina pectoris abnormal heart sound
Left bundle branch block usually has no obvious hemodynamic abnormalities, so there are generally no obvious symptoms and signs, and the symptoms and signs appearing mostly are caused by the primary disease.
Examine
Left bundle branch block
There may be a corresponding laboratory test change for the primary disease.
Mainly rely on ECG and cardiac electrophysiological examination.
Electrocardiogram examination
(1) Complete left bundle branch block (CLBBB):
1 typical ECG characteristics of complete left bundle branch block:
A.QRS wave pattern change:
a. The left lead (V5, V6, I, aVL lead) appears wide, the top is blunt, there is a notched R wave, and there is no q wave except for the aVL lead.
b. Right chest V1, V2 lead is rs type (very small r wave followed by a deep and wide S wave), V1, V2 lead even QS type, V3 lead rare QS type, chest lead The hour hand is indexed.
c.III, aVF, aVR lead QRS wave is QS type.
The B.QRS wave time limit is 0.12s (about 0.14s or more).
C.V5, V6 lead chamber wall activation time (R peak time) 0.06s (mostly > 0.08s), V1, V2 lead chamber wall activation time is normal.
D.ST-T change: ST-T direction is opposite to QRS main wave direction, V1 lead ST segment is slightly elevated, T wave is upright; V5, V6 lead ST segment is low, T wave is inverted; I, aVL lead ST The segment pressure is low, and the T wave is inverted; the ST segments of III, avF, and avR leads tend to rise to different degrees, and the T wave is erect.
2 detailed description of typical ECG of complete left bundle branch block:
A.QRS wave time limit: The lower limit of the QRS wave time limit of complete left bundle branch block is 0.12s. Some scholars believe that it is not appropriate to extend the QRS time to 0.12s as the absolute standard for diagnosis, because some have typical left bundle branch block. The electrocardiogram of the graph does not necessarily have a QRS time of 0.12 s, so it should be combined with other features to determine whether there is a bundle branch block.
B. Flat-top R wave of the left anterior region lead: V5 in the typical V5, V6 lead has no q wave, and the R wave is obviously notched, which only accounts for about 68%, and about 30% of the left bundle branch block appears. Rs, rS, RSR and other graphics, and I, avL lead can appear typical R wave, may be due to the heart along the long axis clockwise position, the left ventricle facing the left rear index; may also be related to V5 The joint probe electrode placement is inaccurate, so a 12-lead ECG can be done, because sometimes in the V6 lead or V4, the V2 lead can show its original appearance, sometimes the V5 lead does not appear and the V6 lead shows a typical R pattern. .
C. R wave in the right anterior region lead: 33.3% in the QS type, 66.6% in the rS type, far more common than the former, V1 in the complete left bundle branch block, QS type in the V2 lead The reason is: when the complete left bundle branch block, the vector of the septal branch from the left posterior to the right disappears, and the abnormal vector from the right to the left of the septum and the right ventricle wall from the left posterior to the right anterior vector cancel each other. .
D.II, III, avF lead in QS type: confirmed by autopsy, complete left bundle branch block without inferior wall infarction, the inferior wall lead can be QS type, intermittent complete left bundle branch block Q Waves appear, and the Q-waves in the lower wall lead disappear when conduction is normal.
E.ST-T changes are due to changes in the secondary repolarization process caused by abnormalities in the depolarization process. However, in most patients with complete left bundle branch block, the myocardium often has inflammation, ischemia, myocardial fibrosis and other diseases. Therefore, in addition to the secondary ST-T changes, it is often possible to have a primary ST-T change factor, so the ECG ST-T change at this time may not be as typical as described above.
F. Whether the simple left left bundle branch block has a left axis deviation of the electric axis: there are still different views. Some people think that the complete left bundle branch block is not accompanied by the electric axis offset, and the QRS electric axis is normal as the diagnostic standard. One, and believes that if the left axis of the electric axis is accompanied, most of the left bundle branch with the left anterior branch block, it is confirmed that it can be accompanied by the left axis of the electric axis, and it is believed that after the complete block of the left bundle branch is interrupted, the right is excited. The bundle branch activates the right ventricle and then transmits to the left ventricle through muscle. The area of the first ventricle that reaches the left ventricle may be different. If the Purkinje fiber of the left posterior branch is reached first, the activation of the anterior wall of the left ventricle is delayed. Then it can be biased to the left; when the excitement first reaches the left front branch tip, the electric axis can be right-biased; if the excitement reaches the double-branched tip at the same time, the electric axis does not change.
3 type of complete left bundle branch block: the lesion of the complete left bundle branch block can be in the left bundle branch or left anterior branch + left posterior branch or both coexisting, can also occur in the His bundle According to the blockage, it can be roughly divided into the following four types of conduction block:
A. Left bundle branch trunk block: about 45.3%, including cases with the same degree of blockage and constant velocity conduction delay. The two are difficult to distinguish on the surface ECG, and the ECG of the left bundle branch block is completely In the graph of left bundle branch block, the frontal QRS axis is mostly in the normal range, and in a few cases, the motor axis is slightly left.
B. The two branches of the left bundle branch have different degrees of blockage at the same time: about 48.2%, of which:
a. Left anterior branch block > left posterior branch block, accounting for 96.9%, ECG showed complete left bundle branch block pattern + frontal QRS axis significantly left ( -30 °).
b. Left posterior branch block> Left anterior branch block: about 3.0%, ECG showed complete left bundle branch block + frontal QRS axis right deviation +120°; left posterior branch block + second degree (3 1) Left anterior branch block, for example: the first 2 QRS intervals of each group are 0.15 s, the electrical axis is -30°, showing a complete left bundle branch block pattern; the third QRS form is different from the former, The period is 0.11s, the electric axis is +11O°, which is consistent with the left rear branch block.
C. Left bundle branch trunk block combined with right bundle branch block: about 3.6%, ECG showed complete left bundle branch block + first degree atrioventricular block.
D. Three-block: about 2.9%, ECG performance: a. left anterior branch block + left posterior branch block + intermittent complete right bundle branch block, accounting for about 25%; b. complete left bundle Branch block + left anterior branch block + first degree atrioventricular block, accounting for about 50%.
E. Second degree type II atrioventricular block + intermittent left bundle branch block + intermittent left anterior branch block, accounting for about 25%.
(2) Incomplete left bundle branch block (ILBBB): The ventricular activation sequence of incomplete left bundle branch block is very similar to the complete left bundle branch at the initial stage of ventricular depolarization. Conduction block, incomplete left bundle branch block, the activation is not completely blocked by the left bundle branch, only the conduction is slow, generally 25 ms longer than the right bundle branch; if the delay exceeds 30 ms, the left bundle branch occurs Complete conduction block, the activation first passes through the dominating region of the right bundle branch, the excitability of the interventricular septum is transmitted from right to left, and the left septum is also stimulated to varying degrees, depending on the extent to which the right bundle branch is delayed. When the activation of the left bundle branch conduction system is reached, the left and left ventricular free walls of the remaining ventricular septum are depolarized in a normal manner.
1 Typical electrocardiographic features of incomplete left bundle branch block:
A.QRS waveform is similar to complete left bundle branch block, but not as obvious as the latter. I, V5, V6 lead appear high R wave, R or RS type, R wave has slight blur or notch, right A deep S wave appears in the chest lead (V1, V2 lead).
B.I, aVL, V5, V6 have no q wave.
The C.QRS wave time limit is <0.12s, but >0.10s.
D.V5, V6 lead chamber wall activation time (R peak time) is extended to 0.06s.
E. Secondary ST-T changes, T waves can be normal, low or inverted.
2 Detailed description of typical electrocardiographic features of incomplete left bundle branch block:
A.QRS wave time limit: It is generally considered to be 0.10~0.11s. A few scholars believe that the QRS time limit can be <0.10s. As long as the beginning of the left-side lead R wave is frustrated or the lead q waves disappear, the diagnosis can be diagnosed as incomplete. Sexual left bundle branch block.
B. Usually V5, V6 leads have no q wave, but in a few cases, V5, V6 leads can have small q waves, the mechanism is: when the left bundle branch conduction delay occurs, and is on the left When the left bundle branch block occurs in the posterior part of the septal branch, the left septal branch conduction is normal, so the V5 and V6 leads may have small q waves.
The small r wave of the C.V1, V2 lead can disappear.
The D.ST-T property can also be opposite to the QRS main wave.
3 Different views on the diagnosis of incomplete left bundle branch block: Some people think that the important diagnostic basis is I, aVL, V5, V6 lead without q wave, R wave is slightly blunt, but in some healthy young people The above-mentioned electrocardiogram performance may also occur, and the q-waves on these leads may also disappear when the left ventricular hypertrophy or the cardiac translocation causes the interventricular depolarization vector to be perpendicular to the lead axis of each left anterior region. Therefore, it is only possible to make this diagnosis when there is a regular change in the electrocardiogram and the dynamic change of the QRS width of the same lead on the same lead. Otherwise, it is difficult to make an incomplete left bundle in the daily clinical electrocardiogram examination. Diagnosis of branch block.
(3) Indexing of the left bundle branch block: only the second degree I type, the type II left bundle branch block is meaningful.
1 second degree type I left bundle branch block: ECG performance: Wen's cycle gradually changed from normal QRS pattern incomplete left bundle branch block to complete left bundle branch block, and repeated, this is the ECG directly showing left The total number of heart beats (QRS wave number) and the total number of heart beats transmitted by the left bundle branch (including the normal QRS waveform and gradually) of each of the Venturi cycles of the second-degree type I left bundle branch block. The ratio of the widened QRS wave number to the total number of complete left bundle branch block QRS waves is the left bundle branch conduction ratio, as the former is 5 and the latter is 4, which is 5:4. analogy.
2 second degree II left bundle branch block: the ECG showed a certain proportion, not the left bundle branch block pattern, and the complete left bundle branch block pattern intermittent or alternating, for example 2:1 Degree II left bundle branch block, ECG showed a QRS wave without left bundle branch block alternately with a QRS wave with a complete left bundle branch block, and another 4:3 second degree II left bundle branch At the time of block, the electrocardiogram showed that three QRS waves that did not have a left bundle branch block alternated with a QRS wave with a complete left bundle branch block.
(4) Special types of left bundle branch block ECG:
1 intermittent left bundle branch block: can be divided into two categories: one is non-frequency dependent left bundle branch block (not related to heart rate changes), also known as heart rate-independent intermittent left bundle branch block; The other type is frequency-dependent left bundle branch block, which can be divided into three types:
A. Fast frequency dependent left bundle branch block.
B. Slow frequency dependent left bundle branch block.
C. Mixed frequency-dependent left bundle branch block, intermittent left bundle branch block is less common than intermittent right bundle branch block, while mixed frequency dependent left bundle branch block is more than mixed frequency dependent right Bundle branch block.
2 Venturi phenomenon of left bundle branch block: The diagnostic criteria are the same as those of the right bundle branch block, and the diagnostic criteria of Friedberg et al. are used:
A. Very regular sinus (or other supraventricular) heart rhythm.
B. Very regular atrioventricular conduction time (PR interval).
C. The QRS complex with a relatively normal shape appears in the cycle.
D. If the successive QRS complexes show a gradual increase in bundle branch block, the diagnosis is a direct display of the Venturi phenomenon.
E. Except for the first heart beat, all other heart beats showed a complete bundle branch block pattern, which was presumed to be an incomplete occult branch bundle.
3 occult left bundle branch block: its characteristics are similar to occult right bundle branch block. There is no left bundle branch block pattern on ECG. When exercise test or random exercise or drug use, left bundle branch block The stagnation appears on the ECG.
4 orthostatic left bundle branch block: its mechanism of production is similar to orthostatic right bundle branch block.
5V5, V6 lead has q-wave left bundle branch block: usually V5, V6 lead does not appear q wave is one of the main features of diagnosis of left bundle branch block ECG, but in a few cases, left bundle branch block Q waves can appear in the V5 and V6 leads.
6 left bundle branch conduction delay: Liu Renguang et al (1987) the left bundle branch conduction is only slightly delayed to the right bundle branch (<0.025s) is called "left bundle branch conduction delay", the ECG vector map features the left bundle branch conduction Blocking, but no QRS time prolonged and medium, terminally slow operation, ECG performance: r wave of the right chest lead decreased, even QS type, S wave deepening (>2.0mV), ST segment elevation (concave face up), T wave is high; the left chest lead q wave disappears or decreases significantly, the s wave disappears and is R type; QRS time is normal, no setback, in the diagnosis should be differentiated from the anterior wall, anterior wall myocardial infarction, and should be combined X-ray, echocardiography excluded left ventricular hypertrophy, S (or QS) wave depth in V1 ~ 3 lead without frustration; ST segment elevation, but concave face up; T wave is high but constant, ST-T without infarction Derivation, all of which help to distinguish from acute myocardial infarction, such as the ability to induce a normal waveform, will be more conducive to the establishment of diagnosis.
7 Complete left bundle branch block combined with left ventricular hypertrophy: It is difficult to diagnose with electrocardiogram, because the autopsy shows that the diagnosis with conventional electrocardiogram is high, but the sensitivity is low, and can not reflect the left ventricular condition of the surviving patient. The incidence of left ventricular hypertrophy in patients with complete left bundle branch block is very high. Some scholars have found that 87.5% of patients with left bundle branch block have left ventricular hypertrophy by echocardiography. Therefore, echocardiography and electrocardiogram are proposed. The method of combining.
A. Hong Xiaosu et al (1995) reported the criteria for the diagnosis of complete left bundle branch block and left ventricular hypertrophy by echocardiography combined with electrocardiogram: Sv2+Rv635mm (sensitivity is 87.5%, specificity is 75%) ), Sv1+Rv535mm (sensitivity is 66.7%, specificity is 75%), left atrial abnormality (left atrial overload, sensitivity 45.8%, specificity 100%).
B. Kafka recommended diagnostic criteria for complete left bundle branch block with left ventricular hypertrophy: a. aVL lead R wave > 1.1 mV; b. QRS motor axis <-40 ° (RI 2.5 mV, this standard Specificity is 90%, Klein believes that SI+Rv6>45mm, QRS time limit>160ms with left atrial hypertrophy, sensitivity of 86%, specificity of 100%.
8 complete left bundle branch block combined with left axis of the electric axis: it is generally considered that the complete left bundle branch block has no significant left angle of the ECG axis, but there may also be a left deviation of the combined ECG axis, such as the left axis of the combined axis. Partial (-90 ° ~ -30 °) accounted for 32.6% ~ 38%, Chen Wanchun believes that the complete left bundle branch block with the left axis of the electric axis may have the following four cases:
A. Incomplete left bundle branch block combined with left anterior branch block.
B. Left anterior branch block The electrocardiogram of the wall block below the combined branch is similar to the complete left bundle branch block, and there is a left axis deviation of the electric axis.
C. Complete left bundle branch block with wall block: the complete left bundle branch block is mostly right deviation. If the left axis of the electric axis occurs later, it may be complete left bundle branch block combined with wall block. Instead of merging the left front branch block.
D. Left anterior branch block combined with left posterior branch block: left anterior branch block is more severe than left posterior branch block. If the left anterior branch and left posterior branch block alternately in the electrocardiogram, the complete left bundle branch block will appear later. The left axis of the electric axis is likely to be left anterior branch block combined with left posterior branch block, and the former is more serious than the latter. The clinical significance of complete left bundle branch block and left axis of the electric axis: the average age is older, most suffer from Coronary heart disease, heart enlargement, heart failure, etc., the condition is heavier, the atrioventricular and sinus block and ectopic heart rhythm are more common, electrophysiological examination shows that the complete left bundle branch block with the left axis of the motor axis average The PR, AH or HV interval was prolonged, and the effective refractory period of the atrium and atrioventricular node was also prolonged, reflecting a wide range of intraventricular conduction disorders.
9 left bundle branch block combined with myocardial infarction: diagnosis from the electrocardiogram has certain difficulties, because the initial vector of the ventricle changes when the left bundle branch block, the ventricular septal depolarization from right to left, through the myocardial septum The depolarization time is about 0.04s, and the lead on the left side of the heart appears to be opposite. Therefore, if there is myocardial necrosis in each part of the left ventricle, there will be no Q wave on the corresponding lead, and some in the right chest lead. QS waveforms can also occur, with ST-segment elevation, T-wave erect, similar to images of acute anterior myocardial infarction. The following ECG changes have some reference value for estimating complete left bundle branch block with myocardial infarction:
A. Complete left bundle branch block combined with acute anterior wall myocardial infarction: QRS wave of ECG in V5, V6, aVL, I lead is QR or qR type, and it is still necessary to rely on ST-T changes to confirm the diagnosis. In the case of simple complete left bundle branch block, V1 and V2 often have a certain degree of ST segment elevation, but when ST segment elevation is >0.8mV or exceeds half of the same lead T wave height or ST segment elevation exceeds The depth of rS or QR wave can be diagnosed as acute anterior wall myocardial infarction. If the ST-T evolution can be observed dynamically within a few days, it is more helpful for diagnosis.
B. Complete left bundle branch block combined with acute anterior wall myocardial infarction: difficult diagnosis, such as the r-wave of the pre-cardiac lead from right to left gradually becomes smaller or disappears, suggesting that the left bundle branch block is combined before Side wall myocardial infarction, in addition to V5, V6 lead ST segment elevation, regardless of whether there is a T wave inversion, is a reliable indicator of diagnosis, such as the dynamic observation of the elevation of the ST segment gradually decline is more conducive to diagnosis.
C. Complete left bundle branch block with acute inferior myocardial infarction: ECG shows II or III, QV or QS wave in aVF lead, but there are exceptions, such as ST-segment elevation in the above lead Coronal T waves (T-wave deep and symmetrical) are more valuable for the above diagnosis. Wang Sirang (1995) suggested that the following ECG changes can be helpful in estimating whether left bundle branch block is associated with myocardial infarction: a. ST segment and T wave changes :
Left chest lead changes: left bundle branch block with anterior wall acute myocardial infarction, left chest lead can often increase in ST segment, this ST segment is elevated, regardless of whether or not followed by T wave inversion, Both are a reliable indicator for the diagnosis of left ventricular anterior wall infarction. In addition, the ST segment of I, aVL leads may also be elevated. If the dynamic progression of ST-segment elevation and decline is observed, the diagnosis is more reliable. .
Changes in the right chest lead: In the left bundle branch block, the right chest lead often has a certain degree of ST segment elevation, if the ST segment elevation in the V1, V2 lead exceeds 0.8 mV or exceeds the same lead T If the wave height is half or the ST segment elevation exceeds the depth of the rS or QS wave, the acute anterior wall myocardial infarction can be diagnosed. If the elevated ST segment can be observed followed by the inverted T wave, and the ST-T has a clear evolution rule. , the diagnosis is more reliable.
ST-T changes in II, III, aVF leads: Because of the complete left bundle branch block, the ST segments of II, III, and aVF leads can be significantly elevated, so it is difficult to diagnose If the "coronal T wave" is accompanied by an elevated ST segment, it is more meaningful for the diagnosis of inferior myocardial infarction.
b. QRS wave group changes:
Indication of changes in ventricular septal infarction: in the complete left bundle branch block, V5, V6, aVL, I lead rarely appear q wave, if there is a wide interval of infarction, the abnormal vector of ventricular septal depolarization is no longer Exist, while the right ventricle is the first to depolarize the heart from the endocardium, the resulting vector is naturally from left to back, so the left chest lead and aVL, I lead in the q-wave, followed by the left bundle Delayed R wave, therefore, when Qr or qR type appears in V5, V6, aVL, I lead, it can be considered as a reliable indication of left bundle branch block with ventricular septal infarction, but in simple In the left bundle branch block, q waves can appear in the V5, V6, aVL, and I leads, so the diagnosis cannot be confirmed based on this index alone. It should be combined with the analysis of clinical data and ST-T. Only to make a correct diagnosis.
Indication of myocardial infarction in the anterior wall: when the R wave height of the anterior leads is significantly reduced and the V5 and V6 leads have significant S waves, the anterior or anterior wall myocardial infarction should be considered. The r-waves of the left thoracic leads gradually become smaller until they disappear, which is helpful for judging the infarction of the anterior wall. Because the left-branch block is only left, the r-wave amplitude of the chest lead should gradually increase from right to left.
Indication of inferior wall infarction: left bundle branch block with inferior myocardial infarction, often lead to Q wave or QS wave in II, III, aVF lead, although in the left bundle branch block sometimes in III and aVF lead Q waves can also occur, but if a Q wave appears in the II lead, it can be diagnosed as a combined inferior wall infarction.
When the left bundle branch block is complicated with myocardial infarction, since the initial ventricular depolarization vector has changed, the diagnosis of ST-T changes with q wave or some lead is limited. Therefore, according to ST In addition to the regular evolution of -T, it should be combined with clinical and laboratory myocardial enzyme assays to help diagnose.
The multicenter study of limiting infarct size (MILIS) evaluated the diagnostic criteria for left bundle branch block with acute myocardial infarction with high specificity (90% to 100%) and positive predictive value (85% to 100%): I, There are at least 2 leads in the aVL, V5, and V6 leads, Q waves are present; the R waves in the V1 to V4 leads are gradually decreased; and at least 2 leads in the V5 to V6 leads are delayed in the S wave ascending branch; Primary ST-T changes occur in at least 2 or more leads of adjacent leads in the infarcted area.
10 bundle branch block concurrent ventricular parallel rhythm: as long as there is bundle branch block, there is a condition of ventricular parallel rhythm, because the distal ectopic focus can be kept undisturbed, ventricular ventricular bundle block Parallel rhythm often occurs in the bundle branch block, and the protective mechanism also occurs in or around the block bundle. In patients with left bundle branch block, the ventricular ventricular rhythm beats are right bundle branch block type. Branch block, especially in patients with multi-segment block, such as multiple forms of ventricular ectopic beats, should consider multiple ventricular parallel rhythm, ventricular parallel rhythm combined with left bundle branch block, almost all organic For sexual heart disease, the prognosis depends on the primary disease and the heart function of the patient. A group of 6 patients reported that 5 of them died of heart failure within 6 to 16 months after the observation period. The treatment was mainly for etiological treatment. Ventricular bundle rhythm complicated by ventricular parallel rhythm can not be treated specially, and patients with permanent bundle branch block ventricular parallel rhythm symptoms can be treated with lidocaine, phenytoin, etc., if necessary, can be considered Cardiac pacemaker.
11 left bundle branch block tachycardia: refers to the QRS wave with left bundle branch block pattern of tachycardia, it is not a single independent clinical entity, can be divided into three types according to the cause:
A. Left bundle branch block type idiopathic ventricular tachycardia: its clinical features are: a. no clear evidence of heart disease; b. most patients have no obvious symptoms or mild symptoms; c. ventricular tachycardia in some patients The induction of overspeed is related to exercise or emotion; d. The response to ventricular stimulation or frequency-increasing stimulation is different, unable or can induce continuous or non-sustained ventricular tachycardia, and cannot or can be terminated by overspeed pacing. However, the reproducibility is not good, and the effects on various antiarrhythmic drugs are different. Verapamil or propafenone has certain curative effect. When the drug treatment is ineffective, cardioversion can stop the attack; e. QRS is at the time of tachycardia Complete left bundle branch block pattern, with an average ventricular rate of 174 beats/min, an average electrical axis of +65.8°, and an average QRS duration of 0.12 s.
B. Left bundle branch block ventricular tachycardia in patients with structural heart disease: such as bundle branch reentry ventricular tachycardia (mostly left bundle branch block ventricular tachycardia and dilated cardiomyopathy) Patients); pathological paroxysmal ventricular tachycardia (1/3 of left bundle branch block, multiple with organic heart disease such as myocardial infarction, etc.); arrhythmogenic right ventricular dysplasia ventricular Tachycardia (mostly left bundle branch ventricular tachycardia and right ventricular cardiomyopathy).
C. Left bundle branch block type supraventricular tachycardia with wide QRS wave: QRS wave time limit is 0.12 s when tachycardia occurs, or mildly widened, and the shape is left bundle branch block pattern, but its essence is Supraventricular tachycardia with supraventricular or anterior pre-excitation syndrome, supraventricular or lateral anterior or posterior bundle branch block or original bundle branch block, so supraventricular tachycardia At the time of rapid onset, the QRS wave pattern is a left bundle branch block pattern, which appears to be ventricular tachycardia. These patients have no basis for organic heart disease.
2. Characteristics of His bundle beam diagram of left bundle branch block
(1) The V-wave time is >0.12 s, suggesting that the intraventricular conduction is delayed.
(2) The interval between AH and HV is normal, indicating that the conduction from the atrioventricular node to the His bundle is normal. The conduction to the ventricle through the right bundle is normal. If the HV interval is also prolonged, the left bundle is completely blocked. There is also an incomplete block in the conduction of the right bundle.
(3) Simultaneously recording the left and right bundle branch potentials through the left and right hearts, it can be confirmed that the potential of the left bundle branch is significantly later than the right bundle branch (>40 ms).
Diagnosis
Diagnosis and differentiation of left bundle branch block
diagnosis
1. Complete diagnosis of left bundle branch block:
1QRS wave time extension (0.12s);
2V5, V6 lead without q wave, showing a wide, rough blunt R wave;
The 3V1 lead has a wide and deep rS or QS wave;
4 chamber wall activation time 0.06s;
5V5, V6 lead ST segment depression, T wave inversion, V1 lead ST segment elevation, T wave erect.
2. Incomplete left bundle branch block QRS time <0.12s, the rest with complete left bundle branch block.
Differential diagnosis
1. Identification with pre-excitation syndrome
(1) Type B pre-excitation syndrome can resemble a complete left bundle branch block pattern, the difference is:
The 1P-R interval is shortened more;
The 2QRS wave start vector has a delta wave, the middle segment of the wave group has no blunt, and the QRS wave is easily variability;
More than 3 no physical heart disease, often with a history of paroxysmal supraventricular tachycardia;
4 intravenous atropine, inhalation of isoamyl nitrite, or exercise, standing or deep inhalation followed by breath holding, improve the conductivity of the normal pathway, so that the pre-shock disappears, can also apply quinidine, procaine The amine inhibits the conductivity of the bypass and causes the pre-shock to disappear.
(2) The electrocardiogram of the bundle bypass is similar to the complete left bundle branch block, with the left bundle branch block pattern with the left axis of the electric axis (usually <-30°), the PR interval is normal, and the Q wave is small or absent. The two main points of identification are: when accompanied by a rapid frequency-dependent conduction delay or venturi conduction in the PR interval, or a tachycardia with a left bundle branch block pattern with the left axis of the electric axis, the suspected room bundle Caused by bypass, electrophysiological examination can establish a diagnosis.
(3) Coexistence of left bundle branch block and side channel: When the bypass channel is located on the same side of the bundle branch block, it may replace the block side bundle branch function, and does not appear as a bundle branch block pattern; if the bypass channel and bundle When the branch block is located on both sides of the heart, the ventricular depolarization wave may present both abnormalities at the same time. For example, when the left bundle branch block is accompanied by the right side bypass, the right ventricular side is simultaneously depolarized by the bypass and right bundle branches. The left ventricle side is delayed by ventricular septal muscle conduction depolarization. Therefore, the electrocardiogram has the characteristics of bundle branch block and pre-excitation syndrome. At this time, if the pre-excitation and bundle branch block occur intermittently, the diagnosis can be more clear.
2. Identification of left ventricular hypertrophy: left ventricular hypertrophy is characterized by: QRS wave <0.11s; V5, V6 lead R wave amplitude is high, beyond the normal range, no blunt, q wave; V5, V6 lead The ventricular activation time is not obvious, it can be 0.05s, generally <0.06s; V5, V6 lead ST segment depression, T wave low level.
3. Incomplete left bundle branch block and anterior wall myocardial infarction incomplete left bundle branch block, V1, V2 lead r wave disappears, can resemble anterior wall myocardial infarction, however acute myocardial infarction is often accompanied by ST-T wave dynamic evolution; ST-T wave in incomplete left bundle branch block is relatively fixed, and V5, V6 lead chamber wall activation time is longer than 0.06s.
4. Incomplete left bundle branch block and anterior wall myocardial ischemia: Incomplete left bundle branch block, V5, V6 lead can appear T wave inversion, and anterior wall myocardial ischemic T Wave inversion is very similar, but the T wave change in incomplete left bundle branch block is a secondary T wave change, the T wave direction is opposite to the QRS main wave direction, often accompanied by ST segment depression, inverted T wave ascending branch It is steeper than the descending branch; the T wave inversion of the anterior wall myocardial ischemia is a primary T wave abnormality caused by ischemia, and T wave inversion can be observed in the downward lead of other QRS complexes, and the inverted T wave is observed. The two symmetry.
