classic pre-excitation syndrome
Introduction
Introduction to typical pre-excitation syndrome The typical pre-excitation syndrome, also known as WPW syndrome, is the most common type of pre-excitation syndrome, with an incidence of 0.1 to 3.1, 90% of patients mostly under 50 years of age, more men than women. Men account for 60% to 70%, and all age groups can develop disease, but the incidence decreases with age. basic knowledge The proportion of illness: 0.005% Susceptible people: more than 50 years old men Mode of infection: non-infectious Complications: shock, sudden death
Cause
Typical pre-excitation syndrome etiology
(1) Causes of the disease
Most patients with WPW syndrome ECG have no structural heart disease, and most of them have abnormal pathways during embryonic development, which can coexist with congenital heart disease or acquired heart disease.
In adults, 60% to 70% of the heart with pre-excitation syndrome is normal, and those with organic heart disease are a minority, which can be seen in:
1. Congenital heart disease These conditions often coexist in the process of congenital heart vascular malformation, therefore, many congenital heart diseases such as atrial septal defect, large blood vessel transposition, tricuspid atresia or Ebstein malformation, ventricular septal defect, Fallot tetralogy, aortic coarctation, mitral valve multi-valve deformity, aortic and pulmonary artery two-valve can be combined with pre-excitation syndrome, congenital mitral valve malformation, ECG is mostly A-type WPW, and Patients with tricuspid atresia or Ebstein malformation are mostly type B WPW, suggesting that WPW syndrome and valvular malformation are homologous to the atrioventricular ring during structural development, and the incidence of WPW in Ebstein malformation patients can be as high as 5%~ 25%, and both are bypasses between the right atrium.
2. Acquired heart disease in valvular disease, various cardiomyopathy, coronary heart disease, hypertensive heart disease, cardiac trauma, etc. can be accompanied by pre-excitation syndrome, mostly manifested as type A WPW, mostly between the left atrium Bypass, it is generally believed that the pre-excitation syndrome that occurs after suffering from acquired heart disease is not caused by acquired heart disease itself. The bypass of the pre-excitation syndrome is already present, but only before the illness, due to The relationship between the bypass and the atrioventricular node-Xi-Pu system axis diameter electrophysiological characteristics, the bypass does not have a conduction function, and thus is not shown on the electrocardiogram, as the age increases or after suffering some kind of heart disease, two The interrelationship of the electrophysiological properties of the conduction pathways has changed, and the bypass has accelerated the conduction, and thus the characteristics of the pre-excitation syndrome appear on the electrocardiogram.
3. Familial pre-excitation syndrome is an autosomal dominant hereditary disease. It has been confirmed that the genes related to familial pre-excitation syndrome are located on chromosome 7q3, and are linked to three sites of D7S505, D7S483 and D7S688 on 7q3. D7S505 has the highest Lod value.
(two) pathogenesis
There is no consensus on the source of WPW syndrome bypass. The normal fibrous ring is the fibrous tissue of the happy room and the ventricle. When the embryo develops to 10~15mm, the atrioventricular ring begins to develop. In the early stage, it is a thin fiber. The layer has a small hole in it. The hole in the hole has a muscle bundle connecting the atrium and the ventricle. Later, due to the development of the fibrous layer and the atrophy of the muscle bundle in the hole, the small hole is finally completely closed to form a complete thick fibrous ring. At this time, the atrium and the ventricle are completely separated, and each undergoes contraction and relaxation activities. The atrioventricular annulus has no conduction stimulating function. Therefore, the atrial activation can only be transmitted to the ventricle through the atrioventricular node. During the development of the atrioventricular ring, If some of the small holes fail to close and the muscle bundle remains, these remaining muscle bundles make the additional conduction path between the compartments through the atrioventricular annulus, ie the Kent bundle, so the Kent bundle is due to the development of the atrioventricular annulus Formed by defects, this is the source of the bypass, the above changes have no other organic heart disease.
Prevention
Typical pre-excitation syndrome prevention
Pre-excitation syndrome 60%70% of the heart is normal, most of them form abnormal pathways during embryonic development. There is no effective prevention method. A small number of patients with pre-excitation syndrome coexist with congenital and acquired heart disease. Active treatment of the primary disease.
Complication
Typical pre-excitation syndrome complications Complications
Pre-excitation syndrome with rapid arrhythmia can cause syncope, even heart failure, shock, sudden death and other complications.
Symptom
Typical pre-excitation syndrome symptoms Common symptoms Chest tightness Acute dyspnea sudden supraventricular arrhythmia palpitations Tachycardia
Pre-excitation syndrome without arrhythmia, without any clinical symptoms, is often attributed to the category of benign arrhythmia, but the existence of bypass is after all an arrhythmia, especially the anatomical basis of reentry arrhythmia, arrhythmia Appearance and prevalence provide conditions, 40% to 80% of patients with pre-excitation syndrome with tachyarrhythmia, followed by paroxysmal supraventricular tachycardia, atrial fibrillation, atrial flutter, premature beats, etc. A small number can cause sudden death, so patients with asymptomatic pre-excitation syndrome must also undergo electrophysiological examination, and no arrhythmia can be considered benign.
For patients with pre-excitation syndrome with arrhythmia, the type of arrhythmia and the clinical situation of cardiovascular disease, and the corresponding clinical symptoms and hemodynamic changes, such as palpitations, chest tightness, shortness of breath, dizziness, syncope Even heart failure, shock, sudden death, etc.
Examine
Examination of typical pre-excitation syndrome
There is currently no relevant information.
Electrocardiogram examination
(1) ECG characteristics of typical pre-excitation syndrome:
The 1P-R interval is <0.12s.
2QRS wave broadening, time 0.11s.
3 pre-shock: also known as (delta or ) wave, is the beginning part of the QRS wave, showing a rough and frustrated wave.
4 Secondary ST-T changes: The ST segment shifts in the opposite direction of the pre-shock, and the T-wave is low or back-pre-shock.
(2) A detailed description of typical ECG characteristics of typical pre-excitation syndrome:
1P-R interval: about 85% of the cases have a PR interval of <0.10s, sometimes as short as 0.04s. The shortening of the PR interval is generally inversely proportional to the degree of QRS wave broadening, but the PJ interval is normal.
2QRS wave: Since the pre-shock is the beginning of QRS, the QRS wave is widened, occasionally up to 0.20 s. The pre-excitation syndrome can be divided into the following two types according to the characteristics of QRS:
A. Incomplete pre-excitation syndrome: supraventricular sexual agitation on the one hand, through the bypass, pre-delivered part of the ventricle, forming a delta wave, and on the other hand, excitatory along the normal atrioventricular conduction system to the ventricle, and under the bypass The agitation of the transmission is absolutely disturbed in the ventricle, forming a special type of ventricular fusion wave. This is called incomplete pre-excitation syndrome. The front part of the QRS wave is composed of pre-shock, and the middle and the back are formed by normal indoor conduction. When the excitement is transmitted along the bypass, the greater the composition of the ventricle, the larger the amplitude of the pre-shock is. On the contrary, the less the ventricular component is, the smaller the pre-shock is. The electrocardiogram of the incomplete pre-excitation syndrome is as follows: :
a. The QRS wave frontal deformity has a pre-shock, the pre-shock amplitude is small, the time taken is short, and the terminal part of the QRS wave is normal and sharp.
b. The QRS wave is broadened, but not very significant. The QRS wave time limit is 0.10 to 0.14 s.
The cP-R interval is <0.12 s.
d. The secondary ST-T change is not obvious, because there is no obvious abnormality in the QRS wave and the posterior segment (main wave), so there is no obvious secondary ST-T abnormality.
The eP-J interval is normal, and is less than 0.26s.
B. Complete pre-excitation syndrome: When the normal atrioventricular conduction system has conduction block, the supraventricular stimuli along the bypass can cause all ventricular myocardium depolarization, resulting in complete pre-excitation syndrome, QRS wave all For the composition of the pre-shock, the whole ventricular depolarization time is significantly prolonged, and the QRS wave shows a significant wide deformity. The electrocardiogram characteristics of the complete pre-excitation syndrome are as follows:
a. The QRS wave is obviously wide and deformed. There is a pre-shock at the beginning of the QRS wave, and the terminal part of the QRS wave is also obviously blunt.
b. QRS time is more than 0.12s, even up to 0.18s.
The cP-R interval is shortened, and the time limit is <0.12 s. If the bypass is blocked once, the PR interval is >0.12 s.
d. The secondary ST-T change is very obvious. The pre-shock and the QRS main wave upward lead ST segment decline, the T wave negative positive bidirectional or inverted; the pre-shock and the QRS main wave downward lead ST segment lift High, T wave positive and negative two-way, upright.
The eP-J interval is normal or prolonged.
3 Pre-shock ( wave): The pre-shock wave takes about 0.05s (usually 0.03~0.06s), and its amplitude is below 5mm, mostly 2~3mm. In a few cases, it can also be higher than QRS wave master. Wave, usually the pre-shock and the main wave of the QRS wave are in the same direction. If the pre-shock is small, it is not easy to judge that helium can be used, the carotid sinus can be compressed, and the pre-shock can be visualized by using atropine and isoproterenol. , or from small to large, deep inhalation, exercise, isoamyl nitrite, etc. can make the original pre-shock disappear.
4 Secondary ST-T wave changes: secondary ST-T wave changes occur in pre-excitation syndrome, the direction of which is similar to the direction of QRS wave induced by pre-shock, but if the pre-shock is positive, ST segment When the elevation or pre-shock is negative, the T wave is inverted, or the pre-shock is positive, but not significant, and the ST segment and the T wave are obviously moved down and inverted, which can definitely indicate this. The ST-segment or T-wave changes are mainly primary, indicating that in addition to the pre-excitation syndrome, the patient also has myocardial damage, but no pre-excitation syndrome of myocardial damage, in the episode of paroxysmal tachycardia Primary T wave changes can also occur after treatment with quinidine, especially.
(3) ECG typing of typical pre-excitation syndrome: According to the direction of depolarization of pre-shock, WPW syndrome can be divided into the following three types.
Type 1A pre-excitation syndrome: the bypass is located in the posterior basal part of the left ventricle. Type A pre-excitation syndrome is always equivalent to left or posterior septal bypass. Supraventricular sensation enters the ventricle from the posterior basal part of the left ventricle. The depolarization of the pre-shock is directed to the left, front, and bottom, and the electrocardiogram appears as a pre-shock and a QRS main wave in all the chest leads (V1 to V6) upwards (Fig. 1). Type is easy to mistaken for right ventricular hypertrophy, right bundle branch block or inferior myocardial infarction, should be noted for identification.
Type 2B pre-excitation syndrome: the bypass is located in the anterior wall of the right ventricle. The supraventricular sensation enters the ventricle from the anterior wall of the right ventricle. From the anterior to the posterior ventricle of the ventricle, the average vector of the pre-shock is directed to the left posterior, ECG. The main wave of the QRS wave in the V1~V3 lead is downward, showing QS, rS or Qr wave pattern; in the V4~V6 lead QRS wave main wave upward (Fig. 2), this type is easily misdiagnosed as anterior myocardial infarction or Complete left bundle branch block, it is believed that the type B pre-excitation syndrome is not necessarily the right side bypass, but also can be seen in other parts of the bypass.
When pre-excitation syndrome combined with bundle branch block, the diagnosis is more difficult, because type B WPW is like left bundle branch block, type A WPW is like right bundle branch block, especially when pre-excitation syndrome is persistent, and It is more difficult to diagnose only by conduction from the bypass. If the bypass and the bundle branch block are not on the same side, the two are easy to identify.
Type B pre-excitation syndrome is due to activation from the anterior wall of the right ventricle into the ventricle. In some patients with complete right bundle branch block, when pre-excitation syndrome occurs, pre-excitation can be transmitted to the right bundle branch block. At the distal end of the site, the waveform of the original complete right bundle branch block disappears. When the waveform of the pre-excitation syndrome disappears, the complete right bundle branch block waveform appears again, and the surface appears to be intermittent, but the surface appears to be intermittent. In fact, the complete right bundle branch block is persistent, and the pre-excitation syndrome is intermittent, which is the appearance of the latter masking the existence of complete right bundle branch block.
Type 3C pre-excitation syndrome: the bypass is located in the anterior wall of the left ventricle. The supraventricular sensation enters the ventricle from the anterior wall of the left ventricle. The average vector of the pre-shock is pointing to the right front. The electrocardiogram shows the deep Q wave in the V6 lead. Or in the QS wave pattern, the main wave in the right anterior region of the anterior region is upward. This type is rare and easily misdiagnosed as anterior wall myocardial infarction.
There is an intermediate type between type A and type B. The bypass is located in the posterior basal part of the right ventricle. The supraventricular sensation enters the ventricle from the posterior base of the right ventricle. The electrocardiogram shows that the V1 lead is QS, Qr or rs type. The V2 lead has a high R wave.
This type of typing method does not take into account the direction of the pre-shock, but instead considers the potential of the last part of the ventricular depolarization, so its significance for positioning is not accurate, but since this type of method is relatively simple, it has been used. It has been replaced by more precise positioning methods such as ECG positioning and endocardial mapping, electrophysiological examination.
(4) Special types of typical pre-excitation syndrome electrocardiogram:
1 frequency-dependent intermittent pre-excitation syndrome: the rate of heart rate plays a role in the refractory period of the atrioventricular bypass (slow bypass) forward conduction, that is, 3-phase or 4-phase block occurs in slow bypass. For example, when the heart rate is slow, the sinus P wave (ventricular supratype) can be transmitted through the atrioventricular bypass. When the heart rate increases, it cannot be transmitted through the atrioventricular bypass and through the normal atrioventricular conduction pathway. When the heart rate becomes faster, the atrioventricular bypass has a 3-phase block in the refractory period, and when the heart rate increases, it can be transmitted through the atrioventricular bypass. When the heart rate becomes slow, it cannot be transmitted through the atrioventricular bypass. It can only be transmitted through the normal atrioventricular conduction pathway, indicating that the 4-phase block occurs in the bypass during the refractory period when the heart rate is slow, suggesting that the 3,4 phase block can occur in the Kent bundle.
2 intermittent pre-excitation syndrome electrocardiogram features: the typical electrocardiogram of pre-excitation syndrome can appear intermittently, that is, several times the heart beats are different degrees of pre-excitation graphics, but other heart beats are normal graphics, or normal graphics and The pre-excitation patterns appear alternately, or they may be normal patterns for a long time (Fig. 6, 7). In addition, the degree of pre-excitation may also change during each heartbeat because the heart chamber is affected by each heartbeat. The range of pre-excitation from the bypass is different, and it can be irregular or gradually become larger or smaller. This is called the accordion phenomenon.
3 occult pre-excitation syndrome: also known as occult pre-excitation, refers to the atrioventricular bypass only one-way room reverse conduction function (occult bypass) without forward conduction function, so in sinus rhythm, tachycardia At the time of atrial pacing, the electrocardiogram QRS is normal without ventricular pre-excitation, and the clinical manifestations of recurrent supraventricular tachycardia (atrioventricular reentry tachycardia) are often accompanied by paroxysmal atrial fibrillation or atrial flutter. Occult pre-excitation syndrome is more common in healthy people without organic heart disease, and partly in patients with mitral valve prolapse and Ebstein malformation.
A. ECG characteristics of occult pre-excitation syndrome: ECG of occult pre-excitation syndrome is normal in sinus rhythm, even if episodes present with paroxysmal supraventricular tachycardia, there is no pre-excitation syndrome in ECG The performance, so it is more difficult to make a correct diagnosis of occult pre-excitation syndrome from the electrocardiogram, electrophysiological examination can confirm the diagnosis.
If the following ECG changes occur, consider the possibility of paroxysmal supraventricular tachycardia combined with occult pre-excitation syndrome: a. Paroxysmal supraventricular tachycardia has a faster ventricular rate, often 180 times / Min, b. The P wave appearing after the QRS wave is retrograde, the P wave in the I, II, III and aVR leads is inverted, and the I lead P wave is inverted, indicating that there is a left bypass, cR-P - Interphase functional bundle branch block (occurrence rate 33% to 77%), F. Atrial fibrillation and reentry tachycardia alternately appear, <p>
There are two types of paroxysmal supraventricular tachycardia in the presence of occult pre-excitation syndrome: a. pre-transmission atrioventricular reentry tachycardia; b. persistent transitional reentry tachycardia, in fact Atrioventricular bypass reentry tachycardia with slow conduction characteristics and concealed ventricular bypass near the posterior septum is a special type of occult pre-excitation syndrome.
B. Cardiac electrophysiological diagnosis and bypass localization of occult pre-excitation syndrome:
a. Rest, tachycardia and left and right atrial pacing, there is no pattern of pre-excitation syndrome on the ECG.
b. There is no need for pre-atrial contraction before the sinus rhythm can automatically trigger supraventricular tachycardia, and the first PR interval does not prolong when supraventricular tachycardia occurs.
c. After tachycardia QRS wave, there is retrograde P-wave, RP-interval is relatively fixed, RP-60ms (intracardiac method) or RP-70ms (esophagus method).
d. Non-invasive atrial activation sequence mapping is helpful for the location of occult bypass. At tachycardia, the esophageal lead and V1 lead electrocardiogram are simultaneously recorded, and the earliest atrial activation site in the two leads is observed. The lead is adjacent to the left atrium. When the P' wave depolarization of the esophageal lead is advanced compared to the V1 lead, the bypass is on the left side (Fig. 9); when the V1 lead P' wave depolarization is earlier than the esophageal lead P' wave, The bypass is on the right side (Figure 10) because the V1 lead is the right chest lead and the P' wave recorded in the V1 lead is the right atrium.
e. Intracardiac electrophysiological examination for the diagnosis of occult pre-excitation syndrome, especially the location of the interval bypass is more accurate and reliable, in the forward-type (forward-type) atrioventricular reentry tachycardia (OAVRT) or right At the ventricular apical pacing, pre-ventricular contraction stimulation during the refractory period of the His bundle can excite the atrium in advance, and the VA (RP-) interval and atrial retrograde activation sequence are similar to those of tachycardia, such as the occult interval. As a retrograde tachycardia, ventricular premature contraction stimulation can reverse the atrium when the atrioventricular node is in refractory period. The A wave generated by the retrograde excitation of the interval bypass often occurs before the H wave, such as retrograde A wave. It appears first in the opening of the coronary sinus, showing the presence of a posterior septal bypass; the retrograde A wave first appears in the low atrial septum, which is the anterior septal bypass.
f. Anterior atrioventricular reentry tachycardia (OAVRT) with functional bundle branch block (FBBB), RP interval measurement has diagnostic significance for occult bypass: occult free wall bypass as OAVRT The retrograde branch, if accompanied by the ipsilateral FBBB, must bypass the contralateral bundle branch and the interventricular septum to reach the ventricular end of the bypass, thus extending the reentry loop, slowing the ventricular rate, and comparing the RP-interval The original 35ms, with FBBB, the ventricular rate and RP-interval did not change, interval bypass with FBBB, RP-interval length 25ms, anterior septal bypass with RFBBB, RP interval prolonged; With LJFBBB, the RP-interval was not prolonged; the posterior septal bypass was accompanied by LFBBB, and the RP interval was prolonged. With RFBBB, the RP interval was not prolonged.
g. Recording the bypass potential is important for the diagnosis and treatment of occult pre-excitation syndrome. Epicardial or endocardial recording methods can be used. The latter is more practical, and special electrode catheters, such as electrode spacing, must be applied. For a 2mm multipolar catheter or an orthogonal lead, place the catheter in the coronary sinus and record the left bypass potential. If the right bypass potential is recorded, the lead should be placed on the right atrial side of the tricuspid annulus. Using a large lead electrode to measure at the mitral and tricuspid annulus, the positive rate of the bypass potential can be up to 100%. At OAVRT, the reverse bypass potential appears after the V wave, before the A wave, before the bypass. Stagnation occurs at AP-V, and reverse block often occurs at AP-A. The bypass potential is recorded at the septum, and the diagnosis of occult interval bypass is well defined.
C. Incidence of occult pre-excitation syndrome: occult pre-excitation syndrome can be seen in patients of any age, some patients with occult pre-excitation syndrome are congenital, and some people increase their pre-excitation syndrome with age It becomes occult, and some people's reverse conduction also changes, and finally disappears. The occult pre-excitation syndrome is rare in the elderly, and the incidence of occult pre-excitation syndrome is uncertain, accounting for supraventricular About 4% of tachycardia accounts for 17% to 37% of reentry supraventricular tachycardia. Occult pre-excitation syndrome occurs mostly in Kent bundles, and rarely occurs in James bundles and Mahaim bundles.
4Kent beam venturi period: Most of the Kent beam forward conduction refractory period is very short, often 0.35s, called fast bypass, a small part of the refractory period is quite long, 0.60 ~ 3.0s, called slow side Road, patients with WPW syndrome have a low incidence of bypass-type schistosomiasis, about 2.1%, and their ECG features are:
AP-P spacing rules.
The BP-R () interval is gradually extended until the wave disappears and the PR interval returns to normal.
C. The corresponding QRS wave is narrowed from wide to narrow, the degree of deformity is changed from light to heavy, and it is repeated, similar to the "accordion effect", while all the QRS waves of the latter are bypassed, and the sinusoidal fusion wave is formed by the common ventricle. The -wave and QRS waves caused by the unequal pre-excitation degree are narrowed from width to width, or gradually widened and narrowed, as if the accordion was closed or opened.
D. An alternating Venturi cycle can also occur, ie the Kent beam exhibits a Venturi phenomenon on a 2:1 block.
5 Reduced conduction and incremental conduction of the bypass:
A. Declining conduction of bypass: During atrial pacing or programmed atrial pre-stimulation, the AV interval is frequency-dependently prolonged, with gradual advancement of atrial pre-stimulation, AH interval and AV interval Gradually extended, while the H wave overlaps with the QRS wave, and the pre-excitation degree is gradually increased. When the X-ray beam is stimulated before, the QRS wave is normalized, indicating that the bypass also has a decreasing conduction performance.
B. Incremental conduction of bypass: The electrocardiogram shows that the PR interval is gradually shortened when the PP interval is fixed, and the QRS complex is normally graphed to partially pre-excited until completely pre-excited. (Figure 11).
6 bypassed second-degree type II block (Figure 12):
7 Highly conductive block of the bypass: The high-level conduction block of the normal atrioventricular conduction system, the mechanism of which is occult conduction and conduction block, due to the fast conduction speed of the bypass, the refractory period is short, and the occultity occurs. There is less chance of conduction, so the incidence of high conduction block of the bypass is low.
8 Abnormal conduction of bypass: Superconductivity is the excitation conduction that indicates the current refractory period. The superconducting conduction mainly occurs in the Xi-Pu system. The superconducting conduction of the bypass is very rare. The electrophysiological characteristics and bundle branch system of the superconducting conduction of the bypass The same, the performance is as follows:
A. The effective refractory period of the extension.
B. Relatively constant super-phase position (close to the T-wave end of the surface electrocardiogram).
C. Frequency dependent (supernormal phase shifts to the right at slow frequencies and superphase shifts to the left at fast frequencies) (Figure 13).
D. Conduction block (caused by occult reverse transmission activity) causes the supernormal phase to shift to the right.
E. It is easy to induce 2:1 superconducting at a suitable fast frequency.
F. Supernormal phase duration is the same.
G. The QRS wave time occurring in the supernormal phase is the same as the QRS wave time occurring in the late diastolic phase.
H. Supernormal phase can be displayed by extending the refractory period.
9 The fracture phenomenon of the bypass in the typical pre-excitation syndrome: the electrophysiological characteristic of the bypass is that the conduction velocity is fast and the refractory period is short. It is theoretically not easy to produce conduction crack phenomenon, but there have been some reports that the fracture phenomenon is An abnormal ECG phenomenon, the main cause of the fracture conduction phenomenon is that the symmetry period of different horizontal planes is inconsistent in the direction of the excitation conduction. There must be three conditions for the fracture conduction: A. There are A and B in the direction of the excitation conduction. B. The horizontal plane of the B phase is effective and should not be long. The pre-programming period first enters the effective refractory period and the conduction block occurs. C. The proximal A level also enters the relative refractory period. The conduction delay occurs. When the degree of delay is sufficient to cause the excitation to reach the B level through the A horizontal plane, the latter has been separated from the effective refractory period, and the fracture phenomenon of the B horizontal plane conduction may occur, and the B horizontal plane is blocked to the next time. The time interval during conduction is called the fracture zone.
Guo Jihong et al reported that the mechanism of the fracture phenomenon in the bypass is: A. In the conduction direction of sinus or atrial stimuli, the bypass is at the distal end, the atrial muscle is equivalent to the proximal end, and the effective refractory period of the bypass is 320 ms. It is obviously longer than the effective refractory period of the atrium (210ms). Therefore, the timely S2 stimulation may encounter the bypass refractory period to hinder conduction; B. After that, the atrial muscle enters the relative refractory period, and the conduction in the room is delayed, when delayed. When the time reaches 80ms, the S2 stimulation passes through the slow conduction in the room and reaches the beginning of the bypass. The latter has already detached from the refractory period, and as a result, the already blocked bypass has recovered the conduction function and is again transmitted.
10 Acquired pre-excitation syndrome: Partial slow bypass forward conduction function was not revealed when the positive ventricular function was good, and only appeared after the lesion occurred in the positive path.
11 dual ventricular fusion wave: Pre-excitation syndrome is a homologous ventricular fusion wave, but when the sinus P wave is bypassed, the right ventricle is transmitted to the ventricle, and the intraventricular pacemaker or even the junction area is the pacemaker. The fusion forms a dual ventricular fusion wave.
12 Delayed pre-excitation syndrome: This type is characterized by normal or prolonged PR interval, but the QRS wave is changed by typical pre-excitation syndrome (with delta wave, QRS time-limited), which is caused by normal atrioventricular conduction system and The conduction speed of the bypass is slowed down.
13 dysplastic pre-excitation syndrome: characterized by a very small pre-shock, short duration, and even difficult to distinguish from the blunt on the normal R wave ascending branch, the QRS interval is mostly normal, which produces a patient's compartment The conduction rate of the conduction system is particularly fast, so that only a small part of the ventricular muscle is pre-excited. This type is more common in children and young women with shorter PR intervals.
Pre-excitation syndrome masks bundle branch block:
A. If the pre-excitation zone is on the same side as the bundle branch block, the bundle branch block is masked and only the pre-excitation pattern is displayed. For example, type B pre-excitation syndrome masks the right bundle branch block, and the right bundle branch block is blocked. Normalization of the pattern; type A pre-excitation syndrome masks the left bundle branch block, normalizing the pattern of the left bundle branch block, and type B pre-excitation syndrome with right bundle branch block is rare. Some people think that it is only seen in the Ebstein malformation. It may be related to the following factors: a. The Kent beam terminates at the proximal end of the right bundle branch block or is too far from the right bundle branch, such as ending at the posterior wall of the right ventricle; b. The right bundle branch block occurs at With less branching, the right ventricular muscle and pre-shock cannot reach or all of the myocardium in the depolarization zone (Figure 14).
B. If the pre-excitation zone and the bundle branch block are on the opposite side, the two images coexist, such as type A pre-excitation syndrome with right bundle branch block, type B pre-excitation syndrome with left bundle branch block (figure 15).
Pre-excitation syndrome masks atrioventricular block: Pre-excitation syndrome with atrioventricular block, as long as the bypass function is normal, the positive block can be concealed, depending on the PR interval is often misdiagnosed, but if the PJ interval is prolonged, That is, whether there should be atrioventricular block or indoor block, it is better to perform esophageal atrial pacing check. If the wave is eliminated in the pacing, the true situation of the positive pathway conduction can be directly displayed (Fig. 16). Inflammatory syndrome with atrioventricular block often suggests organic heart disease.
Pre-excitation syndrome masks acute myocardial infarction or primary ST-T changes: the most common electrocardiographic changes in transmural myocardial infarction are initial vector abnormalities, and the delta wave of pre-excitation syndrome can also cause initial abnormalities in ventricular depolarization, and The ventricular depolarization begins earlier than the former. In addition, due to the difference in the bypass position, the delta wave has a negative phase or a positive phase in different leads, thus masking or resembling a myocardial infarction pattern, such as A-type WPW syndrome covering the front wall. Myocardial infarction: a case of intermittent type A WPW syndrome, in the V2, V3 lead in the pre-excitation interval, QS waveform, ST-T injury, ischemic evolution, QS wave disappears in the pre-excitation, atropine After the delta wave disappeared, there was a typical myocardial infarction pattern. Another pre-excitation syndrome masked the inferior myocardial infarction, patients with persistent chest pain, electrocardiogram II, III, aVF lead Q wave, serum myocardial enzyme increased, diagnosed as the inferior wall In acute myocardial infarction, a typical pattern of type A WPW syndrome appeared in the electrocardiogram a few days later, which masked the inferior wall infarction. After the A-type WPW syndrome disappeared, the inferior wall infarction pattern appeared again. In addition, the pre-excitation syndrome pattern resembled Myocardial infarction pattern (FIG. 17).
Pre-excitation syndrome masking or similar myocardial infarction pattern, the key lies in the direction of the wave average vector: when the mean vector of wave is around -70°, the pathological Q wave of the I, aVL lead disappears, masking the high sidewall Infarct pattern; when the mean vector of wave is around +100°, the pathological Q wave of leads II, III and aVF disappears, and the inferior wall infarction is concealed. In the case of pre-excitation syndrome alone, the average vector of wave points to -70°. When left and right, II, III, aVF leads can produce Q waves, similar to the inferior wall infarction: when the mean vector of wave points to +100°, Q waves are generated in I, aVL leads, similar to anterior myocardial infarction, type A The WPW syndrome ECG can also produce a pattern of positive posterior wall myocardial infarction. Type B WPW syndrome can produce a negative wave in the right chest lead similar to the anterior wall myocardial infarction pattern.
Pre-excitation syndrome is easy to cover up myocardial infarction and missed diagnosis. The following two points may suggest or suspect myocardial infarction or primary ST-T changes: A. ST-segment elevation occurs with R wave as the dominant link, B. Inverted, leading deep T wave, both can see the dynamic evolution process.
Pre-excitation syndrome masks ventricular hypertrophy: type A, type C pre-excitation syndrome is easy to cover left ventricular hypertrophy, and false positive rate of right ventricular hypertrophy is increased; type B pre-excitation syndrome is easy to cover right ventricular hypertrophy, and left The false positive rate of ventricular hypertrophy is increased. If the type A WPW sign is associated with right ventricular hypertrophy or type B WPW syndrome with left ventricular hypertrophy, both can be displayed simultaneously, that is, the pattern of pre-excitation syndrome and ventricular hypertrophy are simultaneously displayed. On the electrocardiogram.
Pre-excitation syndrome combined with diagnosis of bundle branch block:
A. Diagnostic criteria for pre-excitation syndrome combined with left bundle branch block:
a. Pre-excitation syndrome combined with left bundle branch block is generally only seen in type B pre-excitation syndrome.
b. In addition to the delta wave, the QRS wave reappears in the middle and after the QRS wave. The QRS voltage is higher than that of the pre-excitation (Rv5+Sv14.0mV), and the T wave is more to the right.
c. In addition to the vector, the ECG vector diagram has a conduction delay, frustration and distortion in the middle of the QRS ring, the maximum vector voltage is increased (2.5mV), and the T-ring is more to the right.
B. Diagnostic criteria for pre-excitation syndrome combined with right bundle branch block:
a. Pre-excitation syndrome combined with right bundle branch block, generally only seen in type A pre-excitation syndrome (Figure 19).
b. QRS wave In addition to delta wave, the right chest lead is rsR' type and T wave inverted.
c. In addition to the vector, the ECG vector diagram has a terminal vector that is obviously delayed to the right front, forming an additional loop, but the T-ring is not left to the left like the simple right bundle branch block, but to the left, this is because Due to the pre-excitation effect, but also the T-ring is still in the left and the lower is not affected, the ECG and ECG vector diagram should be combined in the diagnosis.
19 pre-existing syndrome: refers to pre-excitation syndrome with atrial fibrillation, atrial flutter, ventricular flutter, tremor, sudden death.
2. The electrophysiological examination of typical pre-excitation syndrome is characterized by atrial and ventricular pacing and pre-procedural stimulation, combined with His bundle electrogram to examine the typical pre-excitation syndrome, and electrophysiological examination can be used to understand the Kent bundle. Characteristics.
(1) Determining the presence of the bypass: Since the atrial activation is transmitted from the bypass to the ventricle earlier than the normal atrioventricular conduction system, the onset of the wave on the electrocardiogram occurs before the H wave of the His bundle beam diagram. Affirmative bypass, but the ventricular pre-shock is not very obvious and suspected to be pre-shock, or there is no ventricular pre-shock and suspected occult atrioventricular bypass. Electrophysiological examination can help diagnose bypass. Exist, the method is as follows:
1 Increase the pacing frequency by atrial pacing, or use the atrial pre-stimulation method to shorten the interatrial stimulation interval, and prolong the conduction time of the atrioventricular node. Impulse is easy to pass from the bypass. The pre-excitation component of the ventricle is gradually increased, which can make the original very small pre-shock surge, and there is no pre-shock ventricular pre-shock, which confirms the existence of the atrioventricular bypass.
In rare cases, there will be a double conduction phenomenon when the atrial procedure is stimulated before the atrial stimulation, that is, the atrial activation is first transmitted from the atrioventricular bypass, and all the ventricles form a complete pre-excitation pattern, and then the atrial agitation is transmitted from the atrioventricular node. All, and sometimes can be encountered, in the atrial pacing or atrial pre-stimulation, there must be the presence of atrioventricular bypass, but does not increase the pre-shock component of the ventricle.
2 change the atrial pacing site: due to electrophysiological examination routine use of the right atrial upper pacing, and the atrioventricular bypass is far, such as the pacing site is close to the atrioventricular bypass, the pacing impulse is easy to pass from the bypass, The original ventricular pre-excitation component can be increased little, and there is no pre-shock in the pre-shock, so the existence of the bypass can be confirmed, and the position of the bypass can be determined. For example, the pre-shock can be stimulated by the lower part of the right atrium. Increase, suggesting that the bypass is between the right atrium; from the coronary sinus electrode to stimulate the atria (or through the esophageal electrode to stimulate the atrium) to increase the pre-shock, suggesting that the bypass is located between the left atrium.
3 using the method or drug method of stimulating the vagus nerve: using compression of the carotid sinus, fatigue, beta blockers, calcium antagonists, adenosine and other slowing the atrioventricular conduction velocity, can be seen in the His bundle beam diagram AH is extended, and P- is unchanged, so the H wave moves backward, and the H wave can also enter the V wave, even after the V wave, which indicates that the excitement is transmitted from the bypass earlier from the atrioventricular node. Later, the pre-excitation on the ECG is greater, and the pre-shock can be more obvious. This confirms the existence of the bypass. Isoproterenol can increase the conduction velocity of the atrioventricular node and reduce the ventricular pre-shock component. Compression of the carotid sinus can lead to atrioventricular block and atrioventricular junction escape. In the sinus rhythm, there is an atrioventricular bypass ventricular pre-shock, and there is no room at the atrioventricular junction. The ventricular pre-shock of the road.
(2) Confirm that the bypass is a Kent bundle: If the following electrophysiological features are available, the bypass can be confirmed as a Kent bundle:
The initial vector of the 1P-R interval was changed, and the pathological Q wave of myocardial infarction was masked.
2 ventricular hypertrophy: the V1 lead of type A WPW syndrome resembles right ventricular hypertrophy when it is R or Rs type, but the PR interval of WPW syndrome is <0.12s, there is wave at the beginning of QRS wave, V1, V6 lead S The wave is not deep, and there is very little right axis deviation. The QRS wave of the V5 lead of the B-type WPW syndrome is high and should be differentiated from left ventricular hypertrophy. According to the PR interval <0.12s, there is a delta wave, etc., and the identification is not difficult.
Diagnosis
Diagnosis and identification of typical pre-excitation syndrome
Diagnostic criteria
1. Diagnosis of typical pre-excitation syndrome
(1) PR interval <0.12s.
(2) There is a delta wave.
(3) QRS wave widening.
(4) Secondary ST-T changes.
2. Diagnosis and prediction of high-risk WPW syndrome Patients with WPW syndrome often have tachyarrhythmia, for example, 40% to 80% of patients with atrioventricular reentry tachycardia, 11.5% to 34% of patients combined Atrial fibrillation, etc., these rapid tachyarrhythmia, due to rapid ventricular response caused by ventricular dysfunction dysfunction, increased ventricular fibrillation and ventricular fibrillation, so the life-threatening arrhythmia caused by WPW syndrome is called high risk WPW, some of the following performances can suggest this diagnosis and prediction:
(1) Tips on electrocardiogram and dynamic electrocardiogram: those who have been confirmed as WPW syndrome on ECG, such as frequent ventricular premature contraction, retrograde atrioventricular reentry tachycardia, rapid atrial fibrillation, especially atrial Those with a fibrillation RR interval 250ms should be vigilant, active treatment, and control of seizures.
(2) Tips in exercise load: If the patient with WPW syndrome suddenly changes to a normal QRS wave after exercise load, and the prolonged PR interval, it indicates that the patient's bypass refractory period is relatively long, according to this Predicting patients with ventricular fibrillation will be relatively slow even if they have atrial fibrillation; if the same lead wave is positively negative or negatively positive on the electrocardiogram during exercise, such patients are more likely to develop rapid atrial fibrillation. Occasionally, atrial fibrillation occurs immediately after or after exercise test. If the ventricular rate is 200 beats/min and the shortest RR interval is >250ms, the risk of ventricular fibrillation is less likely to occur: otherwise, 250ms predicts the risk of ventricular fibrillation, RR The patient is in a high-risk state with an interval of <180ms.
If the pre-excited patient does not have an organic heart disease, the active treadmill exercise test will have the same exercise load as the normal person, but if the concurrent supraventricular tachycardia, atrial flutter, or atrial fibrillation, the physical strength The ability to move will undoubtedly be significantly limited, so patients should be closely observed to prevent accidents.
(3) The instructions for drug testing and electrophysiological examination are helpful, but you must choose the indications and prepare for first aid.
Differential diagnosis
1. With the bundle branch block, the PR interval is >0.12s, the QRS time limit is often >0.12s, the abnormal width is more common, and the PJ interval is often >0.27s. Although the QRS wave has frustration, it is blunt, but There is no pre-shock in the initial part, the pattern is generally constant or changes with the pathological process, most of which have no complications such as supraventricular tachycardia and atrial fibrillation. This is not difficult to distinguish from WPW syndrome.
2. It is usually not easy to be misdiagnosed with myocardial infarction, but sometimes the downward wave can have a main wave upward QRS complex and the delta wave on the equipotential line with a main wave downward QRS wave, which is similar to pathological Q wave and mistakenly believe that myocardial infarction, such as type B WPW syndrome V1 ~ V3 lead in the QS type, similar to the anterior wall myocardial infarction; C type in the V5, V6 lead "Q" wave, similar to the sidewall myocardial infarction Some delta waves resemble inferior myocardial infarction in III, aVF leads, and some delta waves resemble high-wall myocardial infarction in I, aVL leads. The main point of identification is the electrocardiogram of WPW syndrome:
1 There are typical upward delta waves on other leads, and the QRS wave is broadened.
The 2P-R interval is <0.12s.
3 Primary ST-T changes lacking myocardial infarction.
In addition, the medical history should be carefully asked whether there are symptoms of myocardial infarction and changes in serum myocardial enzymes. Special attention should be paid to the evolution of ECG, especially the evolution of ST-T waves. It should also be noted that since the initial vector of WPW syndrome has Altered, the pathological Q waves of myocardial infarction were masked.
3. Ventricular hypertrophy The V1 lead of type A WPW syndrome resembles right ventricular hypertrophy when it is R or Rs type, but the PR interval of WPW syndrome is <0.12s, there is delta wave at the beginning of QRS wave, V1, V6 lead S The wave is not deep, and there is very little right axis deviation. The QRS wave of the V5 lead of the B-type WPW syndrome is high and should be differentiated from left ventricular hypertrophy. According to the PR interval <0.12s, there is a delta wave, etc., and the identification is not difficult.
