Pediatric Pre-excitation Syndrome
Introduction
Introduction to pediatric pre-excitation syndrome Pre-excitationsyndrome (also known as Wolff-Parkinson-Whitesyndrome), there is an additional conduction beam between the atrium and the ventricle, also known as the atrioventricular bypass, which makes some ventricles premature, pediatric The incidence rate is 1/1000. There is a residual non-specific myocardial fiber bundle across the atrioventricular annulus, which connects to the atrial ventricular muscle and is called the atrioventricular bypass. This abnormal atrioventricular bypass has atrioventricular conduction function, leading to abnormal electrophysiological manifestations and tachyarrhythmia, known as pre-excitation syndrome, also known as Wolff-Parkinson-White syndrome (Wo-Pa-Wai) syndrome ( WPW syndrome). This remaining conduction bypass is caused by abnormal cardiac development. In the early stage of embryonic development, the atria and ventricles are a continuous structure. In the future, the intermuscular connection gradually disappears and is replaced by an annulus fibrosus. The formation of the right bypass is due to the fact that the fetus does not form an atrioventricular annulus during development and is still connected by a bundle of muscle fibers, most of which disappear in the first 6 months of life. For example, after 6 months, the muscle bundle did not disappear, or the atrioventricular annulus was not formed, and the bypass was formed. The formation of the left free wall bypass was mainly caused by the absence of degeneration of interventricular fibrosis during embryonic development. basic knowledge Sickness ratio: 0.0001% Susceptible people: children Mode of infection: non-infectious Complications: arrhythmia, atrial fibrillation, sudden death
Cause
Causes of pre-excitation syndrome in children
(1) Causes of the disease
Most patients with pre-excitation syndrome have no structural heart disease, and a few are seen in the tricuspid valvular deformity, corrective large vessel dislocation, tricuspid atresia, right heart, endocardial fibroelastosis and cardiomyopathy. There are reports of familial morbidity.
Genetic characteristics
The age of pre-excitation syndrome varies according to the base of the survey population, which is 0.01-0.3% in normal healthy people, with an average of 0.15%. In children with congenital heart disease, the prevalence of pre-excitation syndrome is 0.3%~ 1.0%, pre-excitation syndrome can occur in any age group, from neonatal, infant, to old age, with a decreasing incidence of age, more identical twin males than females, most adult pre-excitation syndrome hearts are normal A small number may be associated with acquired or congenital heart disease. Although the bypass is congenital, its performance can be found in the next few decades, showing the acquired disease manifestations, relatives of patients with pre-excitation syndrome, especially many others. The relatives of the patients with the road, the pre-excitation rate increased, suggesting that the acquired genetic form, Mehdirad reported that 4 families found pre-excitation syndrome and ventricular hypertrophic cardiomyopathy, there exist autosomal dominant inheritance, gene locus 7q3, Xiao Jianzhong One case of maternal-inherited insulin-dependent diabetes mellitus was found in patients with type A pre-excitation syndrome. Molecular biological examination revealed a mutation of the 3243 mutation in the mitochondrial tRNAILen gene. For the WPW syndrome and chromosomal and genetic abnormalities, but the exact mode of inheritance needs further study.
2. Bypass anatomical features
Through cardiac electrophysiological studies, it has been confirmed that the pre-excitation syndrome is caused by the presence of an additional conduction beam between the atrium and the ventricle. Currently, the histologically confirmed atrioventricular additional conduction bundles are:
(1) The accessory bundle is the Kent bundle: it is located on the left or right side of the atrioventricular sulcus, connecting the atrium and the ventricle, and the pre-excitation syndrome is caused by this bundle.
(2) The bundle of the house bundle is the James bundle: another fiber that is the bundle between the posterior junctions, which is connected to the atrioventricular bundle by bypassing the upper and middle portions of the junction of the compartment.
(3) The bundle of the chamber is also called the Mahaim bundle: the junction between the compartment and the ventricle is connected. The above additional conduction bundles can exist alone or coexist. In recent years, cases of concurrent refractory supraventricular tachycardia have been adopted. Radiofrequency ablation or surgery to cut off the additional conduction beam, postoperative pre-excitation syndrome and tachycardia disappeared, further confirming this argument.
(two) pathogenesis
According to the anatomical classification of the bypass and the physiological characteristics of the bypass and the characteristics of the electrocardiogram, the pre-excitation syndrome is divided into:
1 typical pre-excitation syndrome (Kent beam pre-excitation syndrome).
2 short PR interval syndrome.
3Mahaim pre-excitation syndrome.
4 intermittent pre-excitation syndrome.
5 occult pre-excitation syndrome.
1. Kent beam pre-excitation syndrome
More common in children, the pre-excitation syndrome is caused by Kent bundle, and the excitability is transmitted from the atrium to the ventricle. At the same time, through the interventricular septum and the normal atrioventricular conduction system, the abnormal interventricular conduction beam crosses the chamber. The speed of the area is fast, so the excitement reaches the ventricle in advance, so that some of the ventricular muscles are pre-stressed, so the PR interval is shortened. These abnormal conduction bundles are composed of ordinary cardiomyocytes. After the activation is transmitted to the ventricle, the transmission in the ventricle is passed. Ventricular muscle conduction, ventricular muscle conduction velocity is 300 ~ 400mm / s, slower than normal through the indoor conduction fiber, only a part of the myocardial depolarization, so the initial part of the QRS wave is deformed and blunt, forming a pre-shock ( wave), and the excitability transmitted by the normal atrioventricular conduction system reaches the ventricle, the normal conduction fiber of the ventricle - His bundle, bundle branch and Purkinje fiber diffusion, the atrioventricular bundle conduction velocity is 1000 ~ 1500mm / s The Purkinje fiber is 4000mm/s, so that most of the ventricles that have not been depolarized are rapidly depolarized, so the QRS wave of the pre-excitation syndrome is wider than normal, and the time is prolonged, and the time from the start of the P wave to the end of the QRS wave ( PJ time limit) Still normal, the increase in the QRS wave time is equivalent to the shortening of the PR interval. It can be seen that the QRS wave of the pre-excitation syndrome is actually a ventricular fusion wave, and the supraventricular stimuli pass through the abnormal atrioventricular bypass. The normal atrioventricular conduction pathway is transmitted down two ways, each activating a part of the ventricular muscle, causing interference in the ventricle.
2. Short PR interval syndrome
Clinically short PR interval syndrome is not uncommon, more common in children and adolescents, but combined with paroxysmal supraventricular tachycardia is rare, when short PR interval syndrome complicated by atrial flutter or atrial fibrillation The ventricular rate is more rapid and there is a risk of sudden death. The mechanism of the short PR interval syndrome is as follows:
(1) James pre-excitation syndrome: Because the James bundle bypasses the atrioventricular node and reaches the lower part of the atrioventricular node, the sinus agitation directly passes through the James bundle to reach the His bundle, avoiding the gate function of the atrioventricular node, so the PR interval Shortened, on this basis repeated episodes of tachycardia, known as LGL syndrome.
(2) small atrioventricular node: that is, the atrioventricular node development is short.
(3) There is a fast path in the atrioventricular node.
3.Mahaim pre-excitation syndrome
In 1941, Mahaim et al first described that some of the conduction beams originated from the lower part of the atrioventricular node, the His bundle, the bundle branch, etc., ending in the interventricular septum or ventricular muscle, divided into a junction chamber bypass, a bundle chamber bypass. Etc., collectively referred to as the Mahaim bundle, is shorter than the Kent bundle, extremely slender, more common in children, decreasing with age, pre-excitation syndrome caused by Mahaim bundle is rare, ECG features normal or prolonged PR interval The QRS time limit is widened, there is a pre-shock, secondary ST-T changes occur, the PT interval is normal or slightly extended, and paroxysmal tachycardia can be complicated. In recent years, studies have found that there is also a relationship between the atrium and the ventricle. The bypass with Mahaim beam electrophysiological characteristics, called Mahaim bundle bypass, its tissue structure and electrophysiological characteristics are similar to the atrioventricular node. The bundle originates from the right atrium, mostly single root. Due to slenderness and high electrical resistance, The conduction velocity is slow, so the PR interval is normal or prolonged. The currently discovered Mahaim bundle is located between the right atrium and the right ventricle. The ventricular end is located at the right ventricular apex. Only the forward conduction performance, no back-transmission function, and concurrent room When the upper tachycardia is over, the QRS is wide and deformed. The electrocardiogram has a high specificity for the diagnosis of Mahaim pre-excitation syndrome, which can provide reliable evidence for the clinic. Since the bundle is located on the right side, the QRS complex is similar to the left bundle branch block pattern, and the left bundle branch block. In comparison, it has the following characteristics:
1 The patient is young and has no structural heart disease.
2 has a history of tachycardia.
3 When the left bundle branch block is V1, V2 is mostly rS or QS type, r wave is slender, and the QRS wave group transmitted under the Mahaim beam is mostly rS type in the V1~V4 lead, and the r wave is wider.
4 Because the bypass terminates in the right ventricular apex, the QRS axis is significantly left-biased.
4. Intermittent pre-excitation syndrome
With the advancement of dynamic electrocardiography technology, the detection rate of intermittent pre-excitation syndrome is increasing. Most patients with pre-excitation syndrome are intermittent, paroxysmal and transient. Like the atrioventricular node, the bypass can also be used. When the first-to-third degree anterior block occurs, the atrioventricular conduction is normal, and the pre-shock amplitude and time can be significantly reduced or disappeared when the bypass is once blocked. At the same time, the atrioventricular node and the bypass have a forward block. When the conduction velocity of the atrioventricular node is slower than that of the bypass, the pattern of prolongation of the PR interval plus the pattern of pre-excitation syndrome and the second-degree anterior block of the bypass are the electrophysiological mechanisms that produce intermittent pre-excitation syndrome. The following three performances:
1 Bypass pre-transmission block has nothing to do with heart rate changes.
The 23-phase forward block, the pre-excitation waveform disappears when the heart rate is increased.
34 phase forward block, after the heart rate is slowed down, the number of pre-excitation waveforms is smaller than that of normal indoor conduction. When the bypass occurs almost completely forward block, the waveform of the pre-excitation syndrome is occasionally seen. Once the three-degree forward block occurs, The pre-excitation syndrome pattern disappears, and the intermittent pre-excitation syndrome associated with sinus rhythm is sometimes very similar to the late diastolic ventricular premature contraction. It should be noted that the pre-excitation syndrome occurs intermittently, the PR interval is shortened, and the QRS time is shortened. Widening, there is pre-shock in the beginning of QRS, and late ventricular premature contraction occurs after the end of sinus P wave, much like intermittent pre-excitation syndrome. The main point of identification is that the latter frequently appears, PR The period is not fixed. When the PR interval is long enough, a ventricular fusion wave with a narrowed waveform may appear. When the inter-law period becomes shorter, there is no P wave before, and the diagnosis can be confirmed at this time.
5. Occult pre-excitation syndrome
The occult bypass only has one-way conduction from the ventricle to the atria, but can not be transmitted in the opposite direction. In sinus rhythm, the ventricle cannot be pre-excited. Therefore, the conventional 12-lead ECG does not have the electrocardiogram of WPW syndrome. The ventricular bypass is called occult bypass. Because the mechanism of most tachycardia in patients with WPW syndrome is caused by the atrioventricular node-His beam pre-transmission, which is caused by the large reentry loop of the bypass reversed, the occult bypass Even if there is only a reverse transmission function, it can still become part of the reentry loop and participate in the formation of atrioventricular reentry tachycardia on the electrocardiogram.
When the tachycardia is normal, the QRS wave is normal. The reversed P wave in the ST segment or the rising wave of the T wave after the QRS wave often indicates that the atrioventricular bypass is involved in the retrograde tachycardia, causing the unidirectional block of the bypass conduction. The cause is still unclear and may be related to various factors. In sinus rhythm, the atrial impulse enters the bypass, but the ventricular insertion near the bypass is blocked and the left or right occult bypass occurs. When there is a functional block in the bypass bypass patient, the bypass on the left side is more common in the ventricle insertion at the bypass, the bypass on the right side, the atrial insertion at the bypass, and the P-wave at the tachycardia. Follow the QRS wave, because the ventricle must be excited and then enter the bypass, excited atrial, so the retrograde P wave must occur after ventricular activation, atrioventricular nodal reentry tachycardia is different, the atrium usually occurs in the ventricular activation, retrograde The shape of the P wave is different from the usual retrograde P wave, because the atrial activation is eccentric, that is, different from the normal reversed sequence, in the atrioventricular nodal reentry tachycardia, and the retrograde atrial activation from the lower right atrium. Interval, and occult Road, mostly on the left, so that the retrograde atrial activation started from the left room, causes generation of a retrograde P-wave negative lead on the limb leads.
Prevention
Pediatric pre-excitation syndrome prevention
For long-term prevention of recurrence, it is not that the drug is effective for every patient. In fact, some drugs can increase the frequency of atrioventricular reentry tachycardia. This is because the drug only extends the bypass pre-transmission refractory period without prolonging. The bypass reverse refractory period, so when the atrial premature contraction, it is easier to induce tachycardia before the bypass occurs, oral administration of two drugs, such as quinidine and propranolol, or procaine Amines and verapamil, which can affect the pre-transmission of the reentry loop, reverse the transmission capacity of the two branches, and class III drugs such as amiodarone or sotalol may be effective in prolonging the atrioventricular node and atrioventricular bypass conduction. According to the clinical situation, the retinal tachycardia, medication history or electrophysiological drug screening can be used to determine the most appropriate drug treatment, for atrial fibrillation with rapid ventricular rate, when the patient receives treatment should be induced atrial fibrillation experiment, To determine if the ventricular rate is controlled, the patient bypass refractory period is very short and is not the subject of medical treatment because conventional medical treatment does not result in a meaningful extension of the bypass refractory period.
Complication
Pediatric pre-excitation syndrome complications Complications, arrhythmia, atrial fibrillation, sudden death
Patients with pre-excitation syndrome have atrioventricular bypass, and their electrophysiological properties are different from those of normal atrioventricular conduction system, so they are prone to reentry arrhythmia, such as paroxysmal supraventricular tachycardia, atrial fibrillation, pre-contraction, etc. Paroxysmal supraventricular tachycardia is the most common, with an incidence of 60% to 70%.
1. Pre-excitation syndrome with paroxysmal supraventricular tachycardia
Atrioventricular bypass has the characteristics of short refractory period and conduction all or none, no declining conduction or conduction delay, atrioventricular bypass can be pre-transmission and retrograde, and the average effective period of pediatric pre-transmission and back-transmission is 231ms. And 310ms, and the normal atrioventricular conduction system has completely different physiological characteristics, the premature ventricular refractory period is shorter than the atrioventricular bypass, and the conduction time is slower than the bypass, thus forming a return loop, which includes the atrium Muscle, atrioventricular conduction system, ventricular muscle and atrioventricular bypass, timely atrial or ventricular premature contraction (more than atrial), when one of the pathways is not out of refractory period and cannot be transmitted, excitement It can only be transmitted from another path to the ventricle. When the ventricular excitation wave reaches the far end of the previous path, the path can be detached from the refractory period and can be stressed. The excitable can pass through and revert to the atria, forming an inter-room reentry. Reentry, such as circulatory tachycardia (CMT), the activation of the reentry loop is longer than the effective refractory period of any part of the loop, with excitable gaps. , so the circular motion can Continued, the CMT of pre-excitation syndrome is divided into cis-transmission type and retrograde type. Because the conduction of the atrioventricular bypass is slow, the refractory period is long, and most of the stimuli are transmitted through the normal channel, that is, the cis-transmission type, and the retrograde type. Rare, atrioventricular bypass has a retrograde function, can not be forwarded, called occult atrioventricular bypass, in the sinus rhythm, PR interval is normal, QRS wave time limit is normal, no pre-shock, such patients can still occur Forward-type circular tachycardia, it is reported that about 30% of cases of paroxysmal supraventricular tachycardia are caused by occult atrioventricular bypass, electrocardiographic features and dominant compartments of concurrent CMT The bypass is consistent, but when the atrioventricular bypass is complicated by atrial fibrillation, the ventricular rate of atrial fibrillation is not too fast because the bypass has no pre-transmission function. The pre-excitation syndrome has two bypasses, and the circular motion is in two compartments. Bypassing the middle ring, ECG performance similar to the reverse type CMT can also occur, but it is rare.
2. Pre-excitation syndrome combined with bundle branch block
(1) Pre-excitation syndrome and right bundle branch block: When the incomplete A-type pre-excitation syndrome is incomplete and complete right bundle branch block, the QRS start of the right bundle branch block is pre-excited wave;
2QRS terminal part is broadly blunt, I, aVL, V5, V6 still have a wide S wave, V1 is changed from rsR type to RsR' or R type, complete pre-excitation syndrome with incomplete or complete right bundle When the block is blocked, the right bundle branch block pattern wave is completely concealed. After the pre-excitation syndrome pattern disappears, the right bundle branch block pattern can be displayed. Incomplete B-type pre-excitation syndrome combined with incomplete and complete right bundle When the branch is blocked, the characteristics of the right bundle branch block can be masked. The QRS has a pre-shock at the beginning, and the QRS terminal vector still points to the right front. The VR leads form qR, QR or R, V5, and V6. RS type, complete type B pre-excitation syndrome can completely cover the incomplete right bundle branch block pattern. When combined with complete right bundle branch block, V1 can be Qr type, r wave exists, is complete right bundle The only manifestation of branch block, short PR interval syndrome with right bundle branch block, showed a PR interval of <0.12 s, and the QRS complex showed complete or incomplete right bundle branch block pattern.
(2) Pre-excitation syndrome with left bundle branch block: Pre-excitation syndrome with less chance of left bundle branch block, can make the diagnosis more difficult, type A pre-excitation syndrome and left bundle branch block, Only the pre-excitation syndrome, the left bundle branch block pattern is concealed, and the electrocardiographic features of the B-type pre-excitation syndrome are similar to the left bundle branch block pattern, even if the complete left bundle branch block is combined. It is also impossible to make a clear diagnosis. After the pre-shock is removed, the left bundle branch block can be revealed. When the short PR interval syndrome is combined with the left bundle branch block, it should be differentiated from the type B pre-excitation syndrome. In the former, the V-V3 lead r-wave has a small amplitude, which takes a short time, while the latter r-wave is wider, and a high-R wave is present in the V3 with a left lead.
3. Pre-excitation syndrome with atrial fibrillation and flutter
Children with pre-excitation syndrome with atrial fibrillation and flutter are less common in adults (2% to 5%), and atrial fibrillation is more common in atrial flutter. The mechanisms of pre-excitation syndrome with atrial fibrillation are:
1 atrioventricular repetitive tachycardia triggers atrial fibrillation.
2 The function of the bypass itself, the bypass ventricle end is rooted, the myocardial conduction resistance of the bypass insertion into the ventricle end is small, and the reverse transmission speed is faster than the forward transmission speed. When multiple bypasses are involved in conduction, the reversible asymmetry can be transmitted to the atrium, such as the atrium. When the muscle is in a tremor phase, atrial fibrillation can be induced. After the bypass, atrial fibrillation can disappear.
3 atrial electrophysiological abnormalities, atrial enlargement and elevated pressure are important factors for atrial fibrillation not easy to terminate, ECG features:
The aP wave disappears and is replaced by an f wave.
b ventricular rate is not uniform, generally higher than the ventricular rate of simple atrial fibrillation, up to 180 times / min.
The cQRS complex is a large deformity, a typical pre-excitation syndrome pattern, and a pre-shock at the beginning of the QRS.
When the dQRS wave group is highly variable and the ventricular rate is fast, the degree of wide deformity of the QRS complex is aggravated. After the ventricular rate is slowed down, the pre-shock is reduced, and the degree of QRS malformation is lighter.
After the termination of atrial fibrillation, the sinus rhythm is a pre-excitation syndrome pattern.
f Atrial fibrillation is mostly induced by premature contraction.
Patients with gP-R cycle <220ms are prone to ventricular fibrillation.
4. Pre-excitation syndrome complicated with ventricular fibrillation
Pre-excitation syndrome is not only easy to atrial fibrillation, but also induces ventricular fibrillation based on atrial fibrillation, but it is rare, its mechanism:
1 bypass refractory period shortened, multiple bypasses involved in conduction, timely atrial premature contraction through the bypass into the ventricular fibrillation period, induced ventricular tachycardia and ventricular fibrillation.
2 After pre-excitation syndrome induces atrial fibrillation, rapid ventricular rate can reduce cardiac output, myocardial ischemia and hypoxia, reduce the threshold of ventricular fibrillation, rapid atrial activation through the bypass of the ventricle, induce ventricular fibrillation.
ECG performance:
1 sinus rhythm is a pre-excitation syndrome pattern, timely ventricular contraction under the ventricle triggers ventricular fibrillation.
2 Pre-excitation syndrome with atrial fibrillation, induced ventricular tachycardia or ventricular fibrillation when the ventricular rate is rapid.
The disease itself can be complicated by tachycardia, ventricular fibrillation, and even sudden death.
Symptom
Pediatric pre-excitation syndrome symptoms common symptoms poor appetite ventricular fibrillation tachycardia pale pale
The incidence of clinical symptoms in patients with pre-excitation syndrome varies greatly. The milder can be asymptomatic, and the severe ones cause obvious hemodynamic changes. The symptoms are mainly caused by atrioventricular reentry tachycardia, and the heart rate can reach 200-300 times. /min, most of the tachycardia caused symptoms, but not fatal, only a few patients formed ventricular fibrillation and were at risk of sudden death.
Tachycardia
Atrioventricular bypass-mediated tachycardia is most likely to occur in infancy, and 60% to 90% of tachycardia naturally disappears within 1 year of age. However, tachycardia, which naturally disappears during infancy, is about 1/3 later. Especially in the 4-6 age group will re-emerge, most infants with tachycardia episodes are missed because of no obvious symptoms, in the "endless" tachycardia, can be expressed pale, poor spirit, poor appetite.
2. Heart dysfunction
Sudden abnormal tachycardia can lead to cardiac insufficiency, most commonly seen in persistent junctional reciprocating tachycardia (PJRT). This risk stems from excessive ventricular rate and sustained tachycardia. For tachycardia cardiomyopathy, tachycardia is often misdiagnosed as dilated cardiomyopathy due to early detection, especially in children, and is often misdiagnosed as dilated cardiomyopathy. When tachycardia is controlled by appropriate treatment, tachycardia Myocardial disease is much better until it returns to normal.
Sudden death
In children with pre-excitation syndrome, atrial fibrillation causes rapid ventricular fibrillation via bypass and is at risk of sudden death.
Examine
Examination of pediatric pre-excitation syndrome
General routine examination without abnormalities, routine myocardial enzyme determination, blood electrolysis value, pH and immune function examination, routine ECG, echocardiography and chest X-ray examination, ECG changes of pre-excitation syndrome, generally divided into typical and Variant two types:
Typical pre-excitation syndrome
(1) Shortening of PR interval: within 0.08s for infants and young children, within 0.10s for older children and within 0.12s for adults.
(2) QRS wave time widening: infants and young children are above 0.08s, older children are above 0.10s, and adults are above 0.12s.
(3) QRS wave type: the beginning part is rough and frustrating, forming a pre-shock.
(4) PJ time: normal, infants and young children within 0.20s, older children within 0.24s, adults less than 0.26s, typical pre-excitation syndrome is due to coexisting atrioventricular or beam bundles and bundles According to the pre-excited pattern, it is divided into 3 types:
Type 1A: The pre-excited ventricular muscle is the posterior bottom of the left ventricle. The pre-shock and QRS wave main waves are upward in the V1, V2 and V5, and V6 leads.
Type 2B: Pre-excited on the right outdoor side wall, the pre-shock and QRS main waves are in the V1, V2 lead down, while the V5, V6 leads are up and the electric axis is left-biased.
Type 3C: The left ventricular side wall is pre-excited, the pre-shock and QRS waves are in the V1 and V2 leads, while the V5 and V6 leads are downward and the electric axis is right-biased.
2. Variant pre-excitation syndrome
Only the PR interval can be shortened, and the QRS wave is normal, caused by the accessory bundle of the house, also known as LGL-Ganong-Levine syndrome; or only the QRS wave is broadened, and there is a pre-shock and PR The interval is normal, caused by the bundle beam, the typical pre-excitation syndrome is the most common (Figure 6), the neonatal A-type is more than the B-type, the older two are similar, and the B-type is more common in patients with structural heart disease. .
Diagnosis
Diagnosis and differentiation of pre-excitation syndrome in children
Pre-excitation syndrome is an electrocardiogram diagnosis, which is often found by electrocardiogram, or caused by paroxysmal supraventricular tachycardia. The pre-excitation syndrome in neonatal period can disappear after more than 1 year old. Or evolved into a recessive type, which is related to the continuous myocardial fiber between the neonatal period conduction system and the embryonic stage. More than half of the children develop paroxysmal supraventricular tachycardia, sometimes pre-contraction This type of tachycardia often recurs, especially in the first-onset age after the age of 1 is more likely to relapse, pre-excitation syndrome, abnormal ventricular activation sequence, it can produce similar patterns with ventricular hypertrophy or bundle branch block, such as Do not pay attention to the shortening of the PR interval, but only pay attention to the QRS wave widening, which can often cause misdiagnosis. The B-type pre-excitation syndrome can be misdiagnosed as the left bundle branch block, and the C-type can be misdiagnosed as the right bundle branch block. Table 1, type A can be misdiagnosed as right ventricular hypertrophy, but the latter axis is right-biased and the PR interval is normal.
