Intraventricular conduction block
Introduction
Introduction to intraventricular conduction block Ventricular conduction block refers to the conduction block below the branch of the His bundle, generally divided into left and right bundle branch block and left branch anterior and posterior branch block, clinically no other special except heart sound splitting which performed. Diagnosis relies mainly on electrocardiograms. basic knowledge The proportion of the disease: the incidence of the disease in the middle-aged and elderly people over 50 years old is about 0.005%-0.01% Susceptible people: occur in a variety of patients with structural heart disease Mode of infection: non-infectious Complications: complete atrioventricular block
Cause
Intraventricular block
Left bundle branch block often occurs in congestive heart failure, acute myocardial infarction, acute infection, quinidine and procainamide poisoning, hypertension, rheumatic heart disease, coronary heart disease and syphilitic heart disease. Left anterior branch block is more common, and left posterior branch block is less common.
Prevention
Intraventricular block prevention
The disease is often a complication of other diseases, such as coronary heart disease, also seen in hypertension, rheumatic heart disease, acute and chronic pulmonary heart disease, myocarditis, degenerative disease of cardiomyopathy conduction system Ebstein (Ebstein) Malformation and Fallot's quadruple syndrome or ventricular septal defect can be complicated by the surgery. Therefore, it is mainly to actively treat the primary disease in the clinic, and carefully observe the electrocardiogram. If it occurs, it should be treated promptly to prevent further development.
Complication
Intraventricular blockade complications Complications complete atrioventricular block
The disease can progress to complete atrioventricular block.
Atrioventricular block refers to impulsive blockage during atrioventricular conduction. Complete atrioventricular block is also called third-degree atrioventricular block, and the block can be in the atria, atrioventricular node, His bundle and double bundle. The symptoms of complete atrioventricular block depend on whether ventricular arrhythmia and ventricular rate and basic conditions of the myocardium are established. If the ventricular arrhythmia is not established in time, ventricular arrest occurs. The autonomous rhythm point is higher than just below the His bundle, and the ventricular rate is as fast as 40-60 beats/min. The patient may be asymptomatic. The ventricular arrhythmia of patients with double-bundle lesions is very low, and the ventricular rate is slower than 40 beats/min. Heart failure and cerebral ischemic syndrome (Adams-Stokes, Syndrome) or sudden death may occur. Slow ventricular rate often causes an increase in systolic blood pressure and a widening of pulse pressure.
Electrocardiographic findings of complete atrioventricular block: 1P wave is independent of QRS complex; 2 atrial rate is faster than ventricular rate, atrial rhythm may be sinus or originated from ectopic; 3 ventricular rhythm is caused by junction or ventricular autonomy The beat point is maintained.
The shape of the QRS complex mainly depends on the location of the block. If the block is located above the branch of the His bundle, the escape beat point originates from the high ventricular arrhythm near the branch of the atrioventricular junction, and the QRS complex does not. Widening. If the block is located in the double bundle branch, the escape rhythm is low ventricular arrhythmia, and the QRS complex is widened or deformed. The rate of high escape rhythm in the adjacent compartment junction is often between 40-60 beats per minute, while the rate of low ventricular autonomic rhythm is between 30-50 beats per minute.
Symptom
Symptoms of intraventricular conduction block Common symptoms Painful palpitations, chest pain, chest tightness, palpitations, palpitations, dizziness, dizziness, shortness, chest tightness, chest tightness, suffocation, sputum, fatigue, paleness
Intraventricular block refers to the conduction disorder below the branch of the atrioventricular bundle, and its common feature is the extension of the QRS time limit.
Normal impulses reach the ventricular muscle almost simultaneously through the atrioventricular bundle and the three-branch system, and the indoor conduction time is about 0.08 seconds, not more than 0.10 seconds.
(a) proximal bundle branch block
A small range of lesions involving the proximal end of the bundle branch (the branching portion of the atrioventricular bundle and the pseudo-branched portion) may cause a three-branch block or a combination of the right bundle branch and the left anterior branch.
(B) distal bundle branch block
The lesion involving the distal end of the three branches can cause: 1 left bundle branch branch block, ie left bundle branch block; 2 left bundle branch branch block, which is formed by the left bundle branch front and the posterior branch together Left bundle branch block; 3 left bundle branch anterior branch block; 4 left bundle branch posterior branch block; 5 right bundle branch block; 6 right bundle branch block combined with left bundle branch anterior branch block; 7 right bundle branch Blocking combined left branch branch branch block; 8 bilateral bundle branch block (double bundle branch block); 9 three branch block.
In the past, according to the QRS time limit of 0.12 seconds, the bundle branch block was divided into incompleteness and completeness. In fact, it can be divided into I, II, III degree block, and the I degree QRS time limit is slightly extended, which is equivalent to incomplete beam branch. Conduction block, the partial QRS time limit of the second degree is significantly prolonged, which is equivalent to intermittent bundle branch block. All QRS time limits of III degree are prolonged, which is equivalent to continuous complete bundle branch block, two or three combined block. When the degree of blockage can be different, the impulse is generally transmitted by a lighter block, and the formed QRS complex is in the form of two other blocks, and the three branches are completely blocked at the same time, which can cause one time. Or multiple ventricular leaks, so the ECG performance of incomplete three-block can be extremely complicated.
(C) intraventricular conduction block
The time limit of QRS in Pueraria fiber or intraventricular conduction block is prolonged, and the characteristic of no bundle branch block is collectively called intraventricular block.
Examine
Intraventricular conduction block check
Electrocardiogram
First, complete right bundle branch block
1V1 lead is rsR/type, r wave is narrow, R'' wave height is wide; 2V5, V6 lead is qRs or Rs type, S wave width; 3I lead has obviously widened S wave, avR lead has width R wave. 4QRS 0.12 seconds; 5T waves are opposite to the main direction of the QRS complex.
Second, complete left bundle branch block
1V5, V6 leads appear widened R wave, its top is flat, fuzzy or with a notch (M-shaped R wave), there is no q wave before; 2V1 lead is mostly rS or QS type, S wave is wide; 3I lead The combined R wave is wide or has a notch; 4QRS 0.12 seconds; the 5T wave is opposite to the main wave of the QRS group.
Third, the left front branch block
1 The left axis of the electric axis is -45°~-90°; the 2I and avL leads are qR type, the R wave is greater than the I lead in avL; the 3II, III, avF leads are rS type, and the S wave is in the III lead>II Lead; 4QRS <0.11 seconds, most normal.
Fourth, the left posterior branch block
1 electric axis right deviation (up to +120 ° or above); 2I, avL lead is rS type, II, III, avL lead is qR type; 3QRS <0.11S.
The left posterior branch is thicker, and the blood supply is also abundant. It is not easy to have conduction block. If the lesion is serious, the right bundle branch may be blocked at the same time, and it is easy to develop into a complete atrioventricular block.
Five, double bundle branch block
Double bundle branch block refers to the indoor conduction block caused by the conduction of the left and right bundle branches. Each side of the bundle branch conduction block is one or two degrees. If the degree of blockade on both sides is inconsistent, it will inevitably lead to many forms of combination, intermittent, regular or irregular left and right bundle branch block, accompanied by atrioventricular block, the PR interval of the heartbeat, The QRS complex law is roughly as follows:
1 only one side of the bundle branch conduction delay, the pattern of the side bundle branch block occurs, the PR interval is normal;
2 If the two sides are the same degree of one-degree block, the QRS complex is normal and the PR interval is slightly extended;
3 If the conduction delay (one degree) on both sides is different, the QRS complex has a slow side beam branch block pattern, and the PR interval is prolonged. The degree of QRS complex broadening depends on the two bundle conduction velocity. The difference, the extent of the PR interval depends on the conductivity of the bundle branch;
4 on both sides of the second degree or one side of one degree, the other side of the second degree, third degree block, there will be different atrioventricular conduction and bundle branch block diagram;
5 Both sides are blocked, then there is no QRS complex after P wave.
When a frame of ECG before and after the control can see the pattern of complete left bundle branch block and complete right bundle branch block, with or without atrioventricular block, you can definitely have a double beam Branch conduction block. If only one side bundle branch block has a PR interval extension or atrioventricular block, it can only be considered as suspicious, because at this time the atrioventricular block can be caused by atrioventricular node and atrioventricular bundle disease, if His bundle Electrogram examination only A--H extended and HV normal, can negate the bilateral bundle branch block.
When the left bundle branch or the right bundle branch and the left bundle branch branch cause conduction disorder, they are called two-branch block, and the more common ones are:
1 right bundle branch block with left anterior branch block; ECG has the characteristics of right bundle branch and left anterior branch block.
2 right bundle branch block with left posterior branch block.
3 left anterior branch block combined with left bundle branch block caused by left posterior branch block.
Right bundle branch block with alternating left anterior branch and left posterior branch block causes double branch branch block of left bundle branch and left bundle branch (called three branch block), this form is often accompanied by Mohs type II Atrioventricular block.
Bilateral or triple-block blockage is caused by severe heart disease, including acute myocardial infarction, myocarditis, and unexplained bundle branch fibrosis, which tends to develop complete atrioventricular block.
Diagnosis
Diagnosis and differentiation of intraventricular conduction block
diagnosis
ECG performance:
First, the right bundle branch block: QRS time limit of 0.12 s or more. The V1 lead is rsR', and the R' wave is blunt. The V5 and V6 leads are qRS, and the S wave is wide. The T wave is opposite to the main wave of the QRS. The pattern of incomplete right bundle branch block is similar to the above, but the QRS time limit is less than 0.12 s.
Second, the left bundle branch block: QSS time limit of 0.12 s or more. The V wave of the V5 and V6 leads is wide, and the top is notched or blunt, and there is no q wave in front. The V1 and V2 leads have a broad QS wave or rS waveform. The T wave is opposite to the main wave of the QRS. The incomplete left bundle branch block pattern is similar to the above, but the QRS time limit is less than 0.12 s.
Third, the left front branch block: the average frontal HRS axis is about -45 ° ~ -90 °. I, aVL lead is qR wave, II, III, aVF lead is rS pattern, RRS time limit is less than 0.12s.
Fourth, the left rear branch block: the frontal average QRS axis is right +90 ° ~ +120 ° (or +80 ° ~ +140 °). The I lead is rS wave, the II, III, aVF lead is qR wave, and RIII>RII, QRS time limit is less than 0.12 s. Before establishing diagnosis, the common lesions causing right axis deviation, such as right ventricular hypertrophy and lung, should be excluded. Emphysema, lateral myocardial infarction and normal variation.
Five, double branch block and three branch block: the former refers to the blockage of any two branches of the three branches of the indoor conduction system. The latter refers to the simultaneous blocking of the three branches. If the three-branch block is complete, complete atrioventricular block can occur. Different ECG performances may occur due to the combination of different numbers such as the number, degree, and intermittent occurrence of the branches. The most common is right bundle branch block with left front block. Right bundle branch block combined with post branch block is rare. When the right bundle branch block and the left bundle branch block alternate, the diagnosis of bilateral bundle branch block can be established.
Differential diagnosis
The disease needs to be differentiated from functional intraventricular conduction block. Functional intraventricular block is a physiological phenomenon in which bundle branches or branches occur when the heart rate is too fast, without any pathological significance. Pathological intraventricular block is a manifestation of functional and/or organic pathological changes in the bundle or branch. It is one of the manifestations of organic disease in the heart, or its main or even unique performance. The identification of functional and organic intraventricular block has extremely important clinical significance.
(1) Functional intraventricular block is when the branch or branch physiological refractory period is normal, the premature activation encounters some parts of the bundle branch or branch has not left the physiological refractory period, only along the The bundle branch or branch that is detached from the physiological refractory period is transmitted, resulting in a bundle branch or branch block pattern that does not deviate from the physiological refractory period, also called differential intraventricular conduction.
(2) Pathological intraventricular block is when the partial bundle branch or branch refractory period has pathological prolongation, the excitability is easy or continuous encountering part of the bundle branch or branch in the pathological refractory period, only along the detached The bundle or branch of the current stage is transmitted, and a bundle branch or branch block diagram with a pathological extension of refractory period is generated, which is referred to as intraventricular conduction block. Pathological intraventricular block is mainly caused by pathological prolongation of bundle branch or branch undulation due to various causes, and the conduction velocity is slowed, and there is no necessarily a histological break of bundle branch or branch.
