Paroxysmal supraventricular tachycardia in children

Introduction to paroxysmal supraventricular tachycardia in children Paroxysmal supraventricular tachycardia (PSVT) is referred to as supraventricular tachycardia, including a group of ectopic impulse formation or reentry loops located in the atrial arrhythmia above the branch of the atrioventricular bundle; clinical manifestations and ECG characteristics are similar, collectively called the room Upper tachycardia. basic knowledge The proportion of illness: 0.02% Susceptible people: children Mode of infection: non-infectious Complications: heart failure cardiogenic shock

Pediatric paroxysmal supraventricular tachycardia

Congenital factors (45%):

Paroxysmal supraventricular tachycardia is common in children with no structural heart disease. Pre-excitation syndrome is prone to supraventricular tachycardia and is prone to recurrence. Acute infection can be an inducement.

Disease factors (45%):

Supraventricular tachycardia can also occur in organic heart disease, such as rheumatic carditis, tricuspid valvular, atrial septal defect, digitalis poisoning, cardiac catheterization, cardiac surgery can also occur supraventricular tachycardia Overspeed.

Pathogenesis

Cardiac electrophysiological studies suggest that a multi-system reentry of supraventricular tachycardia is caused by a small increase in self-discipline. Reentry can occur in the sinus node, atrium, atrioventricular node and atrioventricular bypass, with atrioventricular bypass and room Room junction reentry is the most common. Beijing Children's Hospital used esophageal atrial pacing to perform electrophysiological studies on 34 children with supraventricular tachycardia. The results showed that 19 patients (56%) had atrioventricular bypass reentry and 13 patients had atrioventricular nodal reentry. (38%), 2 cases (6%) of patients with autonomic increase, Chongqing Pediatric Hospital used the same method to study the mechanism of 27 cases of supraventricular tachycardia, and in 22 cases with subtype, the atrioventricular bypass reentry accounted for 63%, followed by atrioventricular nodal reentry.

1. Foldback mechanism

The occurrence of the return must have three factors: one-way conduction block, conduction delay and return loop.

(1) atrioventricular node reentry: the longitudinal separation of the atrioventricular node is a double path: slow path ( diameter) conduction is slow, refractory period is short; fast path ( diameter) conduction is fast, refractory period is long, in normal sinus rhythm At the same time, the atrial impulse is transmitted through the fast and slow path at the same time, and the QRS wave is generated by the fast path. The slow-path is transmitted to the atrioventricular bundle, and the latter is blocked in the refractory period of the fast path. If there is atrial period, Pre-contraction, the fast path is still in the refractory period, one-way block, the impulse is transmitted through the slow path to generate QRS wave, and the echo is reversed along the fast path to produce atrial echo, such as atrial premature contraction occurs more in advance, resulting in atrial When the echo is transmitted to the slow path, the latter has left the refractory period, and the atrioventricular nodal reentry room velocity (AVNRT) is formed, which is transmitted by the slow path. The fast path reverser is called the slow-fast type (S-FAVNRT). ), more common, from the fast path down, slow path back is called fast-slow (F-SAVNRT), rare.

(2) Atrioventricular reentry: pre-excitation syndrome with supraventricular tachycardia, atrioventricular node is slow, atrioventricular bypass is fast, and reentry loop includes atrioventricular node, ventricular muscle, atrioventricular bypass and atrial muscle The atrioventricular reentry ventricular tachycardia (AVRT) is usually triggered by a timely atrial premature contraction. Impulse is blocked in the bypass, and is transmitted along the atrioventricular node. When the ventricle is reached, it is retrogradely bypassed by the bypass, and the circulation is endless. Room reentry room ventricular tachycardia, from the atrioventricular node pre-transmission, bypass reversal is called the rumor-type atrioventricular reentry room ventricular tachycardia, by the bypass, the atrioventricular node reversal is called retrograde compartment reentry The rate of supraventricular ventricular is extremely rare. For example, the atrioventricular bypass of pre-excitation syndrome has only one-way retrograde function, and the electrocardiogram has no ventricular pre-excitation (normal PR interval, no delta wave), but can still be formed by bypass. The anterior chamber reentry ventricular tachycardia, known as recessive pre-excitation syndrome, was diagnosed as a AVRT in the Beijing Children's Hospital by esophageal atrial pacing, and the recessive pre-excitation syndrome was 6 (31%).

(3) sinus node reentry and intraventricular reentry: both are rare, sinus node reentry occurs in patients with sick sinus syndrome; intraventricular reentry is seen in patients with enlarged atrial heart disease.

2. Increased self-discipline

Due to the increased elevation of the 4 phase of the atrial or atrioventricular node, the formation of ectopic impulses, mostly in patients with structural heart disease, hypoxia, catecholamines and digitalis side effects, can cause atrial and atrioventricular node The self-discipline of the area is enhanced, and the autonomous atrial tachycardia in children may be caused by self-disciplined embryonic cells in the atrial muscle.

Pediatric paroxysmal supraventricular tachycardia prevention

1. Actively prevent upper respiratory tract infections and various myocarditis.

2. Prevent digitalis poisoning.

3. Actively prevent and treat congenital heart disease, but most children have not been able to find the cause, so the preventive measures are not clear.

Pediatric paroxysmal supraventricular tachycardia complications Complications heart failure cardiogenic shock

Often complicated by heart failure, cardiogenic shock, recurrent episodes can be complicated by tachycardia. Small complexion gray or gray, skin wet and cold, breathing faster, pulse is weak, often accompanied by dry cough, sometimes vomiting, palpitations, precordial discomfort, dizziness and so on. If the seizure lasts for more than 24 hours, heart failure is prone to occur. If there is an infection at the same time, there may be fever, peripheral white blood cells and other manifestations.

Pediatric paroxysmal supraventricular tachycardia symptoms Common symptoms tachycardia, shortness of breath, dizziness, palpitations, heart palpitations, angina pectoris, heart enlargement, dyspnea, edema

The clinical features are paroxysmal attacks, sudden onset and sudden stop, which can be seen at any age, infants are more common, newborns and the last month of the fetus can also occur, infants are more common in atrioventricular reentry, larger children are in the room There are many cases of stenosis, and the baby is more common within 4 months. The heart rate is accelerated when the attack occurs. The child reaches 160 times per minute, the baby can reach 250 to 325 times, the frequency is constant, and the attack lasts for a few seconds or even several days. However, it usually only lasts for several hours, rarely more than 2 to 3 days. Infants often have antifeedant, vomiting, restlessness, shortness of breath, sweating, paleness, coldness of the limbs and cyanosis and other manifestations of cardiogenic shock. Self-reported palpitations, pre-cardiac discomfort, angina pectoris and dizziness, etc., if the seizure lasts for a long time, more than 24h, heart failure occurs more frequently, and the heart rate of infants within 6 months is more than 200 times/min, which is more likely to be complicated by acute heart failure. For breathing difficulties, heart enlargement, liver enlargement, wheezing sound in the lungs, X-ray examination of mildly enlarged heart shadow and pulmonary congestion, but also fever, leukocytosis and shortness of breath, can be misdiagnosed as severe pneumonia, but attack Once stopped, heart failure is controlled, the child is comfortable as usual, tachycardia sudden sudden stop is the characteristic of the disease, fetal ventricular tachycardia can cause severe heart failure, fetal edema, pre-excitation syndrome often relapse, repeated episodes can be repeated Caused by tachycardia.

Pediatric paroxysmal supraventricular tachycardia

Can have hypoxemia performance, may have leukocytosis and so on.

1. Esophageal atrial pacing check

The mechanism of the supraventricular tachycardia and the diagnosis of each type can be clarified. The esophageal electrode is close to the left atrium, and the P wave (Pk) of the esophageal lead electrocardiogram is clearly and easily identifiable, which is beneficial to the room room period (RPE) when the room speed is high, such as synchronous tracing. The V1 lead electrocardiogram can distinguish the atrial activation sequence. The starting point of PE is the beginning of left atrial activation. The starting point of PV1 is the right atrial activation. Measuring PV1-PE time interval can identify the atrioventricular junction reentry and atrioventricular bypass. The speed is up, and the part of the bypass can be estimated. The upper speed of the room at the junction of the atrioventricular junction: RPE<70ms, PV1, PE occur synchronously, the PV1-PE time interval is close to zero, and the room side bypass room is fast: RPE > 70ms, PV1-PE time interval >30ms, left side bypass, PE first depolarization, PV1-PE time interval is negative; right side bypass, PV1 is the first to depolarize, PV1-PE time interval is positive, each type The electrophysiological characteristics of supraventricular esophageal atrial pacing are as follows:

(1) Atrioventricular junction area reentry room speed: 1 esophageal atrial pacing can induce and terminate the attack. The 2 compartment conduction curve was interrupted. 3 slow-fast: RPE<70ms, PER/RPE>1; fast-slow: RPE>70ms, PER/RPE<1. The 4PV1-PE time interval is close to zero.

(2) The rate of resection of the atrioventricular bypass: 1 esophageal atrial pacing can be induced and terminated. The 2 compartment conduction curve is uninterrupted. 3 As the atrial pacing frequency increases, the pre-shock gradually becomes apparent. 4RPE >70ms, forward PER/RPE >1; reverse PER/RPE<1. The distance between 5PV1-PE is >30ms, the left side channel is negative, and the right side channel is positive.

(3) Autonomous atrial tachycardia: 1 esophageal atrial pacing can not be terminated and induced. 2PER/RPE<1, RPE >70ms.

2. X-ray inspection

Chest radiographs can be seen in the chest radiograph, and the heart shadow is slightly enlarged and changed.

3.B Ultra

It can be seen that the liver enlarges the performance of liver congestion.

4. Typical pre-excitation syndrome

(1) The PR interval is shortened, <0.1s.

(2) The QRS time is extended, >0.1s.

(3) The beginning of the QRS wave is blunt, called pre-shock (also known as delta wave). Because the ventricular pre-excitation occurs, the ventricular start vector is opposite to the judgment. Therefore, for most children, the QRS wave can be passed. The pre-shock formed by the starting vector determines the position of the bypass. For example, the bypass is located at the back of the chamber, the ventricular excitation vector is upward, and the pre-shock is negative in the II, III and aVF leads; At the left or front of the chamber, the ventricular activation vector is to the right and the pre-shock is negative in the I and aVL leads.

(4) There may be secondary ST-T changes.

(5) The relationship between the pre-shock shape and the position of the bypass: The classical classification method (Rosenbaum) divides the WPW syndrome into two types, A and B. The pre-shock of type A is positive in the V1 to V5 leads. The QRS wave is also dominated by R waves. It is speculated that type A reflects the left atrium, there is a bypass between the ventricles, and the left ventricle is pre-excited. The pre-shock of type B is negative or positive in the V1 to V3 lead. The QRS wave is dominated by the S wave, and the pre-shock wave in the V4 to V5 lead is positive. It is speculated that the B type reflects the right side room, the interventricular septum, and the right side wall of the ventricle is pre-excited.

With the development of surgery and catheter radiofrequency ablation, the classical classification method has not adapted to the clinical needs. Some scholars have summarized the relationship between the sinus rhythm ECG and the parasitic position of the dominant pre-excitation syndrome:

5. Short PR interval syndrome

1 In normal sinus rhythm, the PR interval is <0.1s. 2QRS wave time is normal. There is no pre-shock at the beginning of the 3QRS wave.

6. Variant pre-excitation syndrome

The 1P-R interval is prolonged. 2QRS time extension. The 3QRS wave has a pre-shock at the beginning. 4 may be accompanied by secondary ST-T changes.

7. occult pre-excitation syndrome

The 1P-R interval is normal. The 2QRS wave time pattern is normal. There is no pre-shock at the beginning of the 3QRS wave.

The occult pre-excitation syndrome comes from the atrioventricular node of the atrium and the pre-transmission of the Hiselin bundle. The non-dominant bypass is transmitted from the ventricle to the atrium. The ectopic bypass has no prequel, so there is no pre-shock, the QRS is normal, occasionally. In some patients, continuous bundle branch differential conduction may occur, and there may be several bundle-distributed QRS waves before tachycardia occurs.

8.PJRT

The retrograde bypass is slow, allowing the atrioventricular node and His bundle to have enough time to restore excitability. The P wave that is slowly reversed by the bypass is closer to the subsequent QRS wave, and is farther away from the previous QRS wave. Due to the persistence of PJRT, the shape and location of P waves, ECG is easily misdiagnosed as persistent atrial tachycardia or even sinus tachycardia. Due to the inherent characteristics of the PJRT bypass, it can block the atrioventricular node or bypass. To terminate the tachycardia, the tachycardia can either terminate in the QRS wave or terminate in the P wave.

Diagnosis and diagnosis of paroxysmal supraventricular tachycardia in children

diagnosis

According to clinical manifestations and electrocardiogram, corresponding diagnosis can be made, and intracardiac electrophysiological examination can be performed if necessary.

1. RR interval: Absolutely uniform, ventricular rate of infants 250 ~ 325 times / min, children 160 ~ 200 times / min.

2. QRS wave: normal shape, if accompanied by differential conduction in the room, the QRS wave is broadened, showing a right bundle branch block; if it is a retrograde bypass, it is a prepaid syndrome pattern.

3. Retrograde P wave: Retrograde P wave (PII, III, aVF inversion, PavR erect) can be seen in about half of the cases, immediately following the QRS wave.

4. ST-T wave: It can be changed by ischemic type, and it can last for 1 to 2 weeks after the termination of the attack.

Differential diagnosis

Typical case diagnosis is not difficult, but it needs to be differentiated from sinus tachycardia in infancy. The heart rate can reach 200 times/min or more, but the RR interval is not absolutely uniform. The supraventricular tachycardia is accompanied by indoor differential conduction or reverse. Type bypass reentry, the QRS wave is large, deformed, need to be differentiated from paroxysmal ventricular tachycardia, heart rate increased significantly, need to be identified with atrial flutter.

Paroxysmal supraventricular tachycardia should be distinguished from chronic atrial tachycardia, turbulent atrial tachycardia and non-paroxysmal border tachycardia. The latter is also called autonomic tachycardia. ECG features:

1 ventricular rate 70 to 130 times / min.

2 atrial activation: no P wave, retrograde P wave or sinus P wave that is out of contact with QRS wave.

3 can occur atrioventricular dislocation and sinus sensation to capture the ventricle, because the heart rate is not fast or accelerate is not serious, does not cause hemodynamic changes, more asymptomatic, combined with atrioventricular dislocation, more due to digitalis poisoning, myocarditis, myocardial infarction, Atrial septal defect or intracardiac surgery, no compartmental dislocation caused by selective vagus nerve inhibition of sinus node, normal heart, good prognosis, treatment for primary disease.

When the baby's room is accompanied by heart failure, due to shortness of breath, lung sounds and liver enlargement, it may be misdiagnosed as pneumonia, which should be noted.

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