Premature contractions

Introduction to pre-contraction in children Premature contraction (prematurebeat) is called premature beat, also known as extrasystole. According to the location of the pacemaker, it can be divided into atrial, atrioventricular (intersection) and ventricular. The most ventricular, the second is the second, the border is less common. Pre-contraction and escape, an arrhythmia caused by ectopic beat stimulation, in which ventricular premature contractions are most common in children, and most have a good prognosis. The escape mainly occurs in children with sinus bradycardia or sinus arrest, and the prognosis depends on the primary disease. basic knowledge Sickness ratio: 0.0001% Susceptible people: children Mode of infection: non-infectious Complications: angina

Prenatal contraction etiology

(1) Causes of the disease

1. Classification ECG can distinguish between atrial, borderline and ventricular premature contractions.

(1) Pre-atrial contraction:

The atrial ectopic P wave that appeared before the first phase was different from the sinus P wave.

The 2P-R interval is prolonged in the normal range (>0.10 s) or in the interfering PR interval.

The QRS wave after the ectopic P wave is the same as the sinus QRS wave. If differential conduction occurs, the QRS wave pattern is mutated. If the ectopic P wave occurs too early, the atrioventricular junction area is still in the absolute refractory period. There is no QRS wave after the P wave, which is called a pre-atrial contraction that has not been transmitted.

4 compensation intervals are mostly incomplete.

(2) Premature contraction before contraction:

The QRS wave that appeared before the first phase has the same morphology as the sinus QRS wave.

2 retrograde P wave, PII, III, aVF inverted, PaVR erect, retrograde P wave can appear before QRS wave, its PR interval is <0.20s; it can also be embedded in QRS wave without retrograde P wave.

3 compensation intervals are mostly complete.

(3) ventricular premature contraction:

1 QRS wave appearing in advance, without P wave before it.

QRS wave widening before the 2nd stage (elderly >0.12s; infant >0.10s), deformity, and the opposite T wave direction is opposite. If the pace point is adjacent to the atrioventricular bundle, the QRS wave is close to normal. .

The 3 compensation interval is complete (Fig. 1). In the same lead of ECG, the pre-systolic contraction is different, the interval between the two is different, and the polymorphic pre-contraction occurs. After each interval of sinus beats, there is a period. The anterior contraction is called the second law. After every 2 sinus fluctuations, there is a pre-contraction to the triple law, and so on. Four or five joint laws, etc., pre-contraction is more than 5 times per minute, which is called pre-systolic contraction. 5 times or less is sporadic.

2. Causes

(1) healthy children: pre-contraction is common in healthy children or non-organic heart disease, due to overwork, mental stress, gastrointestinal diseases, biliary tract infections or autonomic nervous disorders, some can not find obvious Cause.

(2) Children with heart disease: Children with heart disease are more prone to premature contractions, such as rheumatic heart disease, various myocarditis, primary cardiomyopathy, congenital heart disease and heart failure, long QT syndrome, biceps Ventral prolapse and ventricular premature contraction often occur in ventricular prolapse.

(3) drug poisoning: digitalis drug poisoning often occurs ventricular premature contraction, other drugs such as quinidine, adrenaline, expectorant poisoning.

(4) hypokalemia and hypoxia: hypokalemia and hypoxia can also cause premature contraction.

(5) Others: Cardiac catheterization, cardiac surgery and anesthesia often occur pre-contraction, pleomorphism, three ventricular premature contractions in pairs or consecutively, more common in children with severe heart disease.

(two) pathogenesis

In recent years, with the further development of cardiac electrophysiology research, there have been some new understandings of the mechanism of pre-contraction, but so far there is no theory that can give a perfect explanation. According to recent literature reports, there are mainly the following theory:

1 fold back to the excitement;

2 ectopic rhythm points increase self-discipline;

3 triggering activities;

4 parallel heart rhythm, in the above mechanism, reentry excitability may be the most important and most common mechanism for producing pre-systolic contraction. For detailed mechanism of reentry excitatory, please refer to pediatric arrhythmia. If the reentry occurs only once, it will show pre-contraction. If the reentry occurs continuously, paroxysmal tachycardia is formed. There is often a fixed interval between the pre-systolic contraction and the anterior sinus beat. The self-discipline of the ectopic rhythm point is considered to be: there are some potential The ectopic rhythm point, in some specific cases, its self-discipline is increased, which is characterized by spontaneous depolarization of the 4-phase diastolic phase of the pacemaker cell or increased negative threshold value, which makes it easier to reach the threshold potential level and produce 1 ectopic Excited causes premature contraction. Some scholars believe that triggering activity can also cause premature contraction. It is mainly related to early post-depolarization and post-delay depolarization. Once the oscillating membrane potential reaches the threshold potential, it can trigger activity and form a new action potential. And triggering a pre-contraction, parallel rhythm theory that: in addition to the sinus node, there are other ectopic rhythms in the heart, and stored around the ectopic rhythm In the afferent block, the sinus agitation can not be invaded, and the ectopic rhythm point can continuously emit excitement according to its natural frequency. However, due to the irregular discharge block around it, some excitement cannot be transmitted. The interval between the formation of ectopic beats varies, and the pre-systolic contraction of parallel heart rhythm is not fixed. The fusion wave can occur, and the clinical ventricular parallel rhythm is more common.

Pre-contraction prevention in children

Pay more attention to the details of life, pay attention to living habits, and promptly find timely treatment.

Premature contraction complications in children Complications

Generally, there are no complications, such as palpitations and other symptoms after the heart disease.

Symptoms of premature contraction in children Common symptoms Heart palpitations, tachycardia, ventricular tachycardia

Most patients have no obvious symptoms. Older children may have heart palpitations, discomfort in the anterior region, irregular heartbeat or chest impact, sudden heart subsidence or pause. The symptoms of premature contraction in heart disease patients are more obvious. The heart auscultation is found twice. After a very close heartbeat, there is a long pause, which is consistent with the pulse pause. The first heart sound of the pre-contraction is mostly enhanced, and the second heart sound is weakened.

Pre-contraction examination

Regular blood electrolyte and acid-base balance check, such as blood potassium, calcium, magnesium, pH, etc.; check erythrocyte sedimentation rate, anti-"O", myocardial enzyme spectrum, immunoglobulin, etc.; if suspected drug factors, blood drug concentration should be checked Suspected nephrotic syndrome, urine routine and blood cholesterol plasma protein should be checked.

1. Electrocardiogram examination: ventricular premature contraction ECG performance:

(1) QRS wave: QRS wave appearing in advance, showing a wide deformity, time limit: adult > 0.12s, child > 0.10s, infant > 0.09s, if the pace point is adjacent to the His bundle, the QRS wave shape can be close to the sinus The farther away from the His bundle, the more obvious the QRS wave width is, and the subsequent T wave direction is often opposite to the main wave direction.

(2) There is no P wave in advance QRS wave: If the QRS wave occurs very late, it can fall behind the sinus P wave, forming the "PR' interval" of the sinus P wave and the advance ventricular QRS wave, which is better than the normal PR. The interval is short, PR'0.10s.

(3) There is often a complete compensatory interval: but the premature contraction occurs very early, may be reversed to the atria, the original rhythm of the sinus node changes, resulting in incomplete compensation interval, and the next PR The prolongation of the interval is caused by occult interference. In addition, when the heart rate is slow, the "insertion" premature contraction (also known as metastatic precontraction) does not affect the autonomicity of the sinus node.

(4) the appearance of ventricular premature contraction: can occur alone, can also be in pairs or in a joint law, the pair of pre-contraction, that is, two ventricular premature contractions appear continuously; the second law, that is, a sinus beat The latter ventricular contraction; or the triple law, that is, a ventricular contraction after two sinus beats,

(5) Inter-rational interval: in most cases, the inter-law interval is equal. If the interval of the same lead is constant, and the QRS wave is consistent, it is a single-source pre-contraction; The period is equal, and the QRS wave is consistent in morphology, which is multi-source ventricular premature contraction, and the interval between the two is different. The QRS wave is consistent in morphology, sometimes ventricular fusion waves, sometimes ventricular parallel rhythm (Fig. 4). There is a certain multiple relationship between the time intervals between two ectopic beats adjacent to each other.

(6) Origination point location: The ventricular premature contraction of pacing in different parts has different manifestations on the electrocardiogram. According to the electrocardiogram, the position of the ectopic pacemaker can be preliminarily judged.

X-ray and B-ultrasound should be routinely performed.

2. Exercise test: observe the reduction of ventricular premature contraction after exercise, disappear or increase, or induce ventricular tachycardia; whether there is ST-T wave change, whether the QT interval is prolonged after the heart rate increases, the shape is single Premature ventricular contraction, including pre-contraction or parallel pre-contraction, disappearance or reduction of anterior contraction in the late stage of exercise, no abnormalities in the above examination, the prognosis is good, after a period of time, pre-contraction can disappear on its own.

3. Echocardiography: observation of the size of the heart chamber, wall and valve conditions, changes in cardiac function, help to diagnose mitral valve prolapse, left ventricular false chordae, dilated and hypertrophic cardiomyopathy, arrhythmogenic right Room dysplasia and so on.

Diagnosis of premature contraction in children

diagnosis

The diagnosis of premature contraction mainly depends on electrocardiogram examination. The ventricular premature contraction is more common in healthy children. There is only ventricular premature contraction. There is no heart disease. How to evaluate the clinical significance of ventricular premature contraction should be understood. No accompanying symptoms, such as palpitation, dizziness or syncope, and the presence or absence of heart disease, require the necessary examination.

1. ECG and dynamic ECG

(1) ventricular premature contraction grading: According to conventional electrocardiogram and 24h dynamic electrocardiogram, ventricular premature contraction can be divided into 6 levels:

Level 0: No contraction before the period.

Level 1: Contraction 2 times/min or >30 times/h before the period.

Level 3: Polymorphism pre-contraction.

Grade 4 A: contraction before the contraction or 2 consecutive contractions.

Grade 4 B: There are more than 3 contractions before the continuity period.

Level 5: The R wave falls on the T wave, that is, the ventricular premature contraction occurs in the vulnerable period of the ventricle, and is likely to cause ventricular tachycardia or ventricular fibrillation.

(2) Benign pre-contraction: ventricular premature contractions in healthy children are consistent in morphology, and the inter-trial interval is equal. Most of them belong to grade 1, 2, and occasionally grade 4 A, which does not cause ventricular tachycardia. Benign contraction before the period.

(3) Complex ventricular premature contraction: pleomorphism, paired or continuous 3 and R wave falls on the T wave. Premature contraction is complicated ventricular premature contraction, and ventricular tachycardia may occur. More common in patients with structural heart disease, complex ventricular premature contraction should be further examined 24h dynamic electrocardiogram, cardiac catheterization and cardiovascular angiography, can obtain more detailed cardiac hemodynamic changes and morphology Change to understand mild myocardial disease.

(4) myocardial injury type: conventional electrocardiogram examination attention to myocardial injury ST-T wave changes, ventricular hypertrophy voltage standard and QT interval measurement, corrected QT interval should be <0.44s.

2. Ventricular premature contraction grading (Lown grading method) Lown is classified according to the ventricular premature contraction detected during the monitoring of patients with acute myocardial infarction. The clinical sometimes simply refers to more than 6 pre-systolic contractions as frequent. Contraction before the period, and below 6 times is the contraction before the accidental period.

3. Pre-systolic grading According to the Kleiger atrial pre-systolic grading standard, the atrial pre-contraction is divided into six levels.

Differential diagnosis

In pediatric clinics, determining the nature of pre-systolic contractions (benign or pathological) is a very important issue because it involves whether the child needs treatment or even hospitalization or school leave, which is why, in daily work, Parents who contracted children before the period are very concerned and often ask this question. Although there are some reference indicators in identifying benign premature contraction and pathological premature contraction, it is sometimes difficult for pediatricians to make a specific case. A clear answer.

1. Evaluation of the differential points of benign premature contraction and pathological pre-contraction In recent years, some literatures at home and abroad have mentioned some indicators or basis for identifying benign pre-contraction and pathological pre-contraction, and summarized the following points:

(1) Pathological pre-contraction (mechanic pre-contraction):

1 There are many basic diseases such as congenital or acquired heart disease, or pathological conditions such as metabolic disorders and drug poisoning.

2 joint or recurrent contraction.

3 multi-source or polymorphic pre-contraction.

4 showed a pre-contraction contraction of parallel heart rhythm.

The 5-ventricular premature contraction QRS complex was significantly broadened, >0.14 to 0.16 s.

6 each type of contraction coexisted before the period.

The sinus beat T wave changed after the 7th stage contraction.

8R-on-T type pre-contraction.

9 contraction before the frequency.

10 The number of pre-contraction increases or the exercise load test is positive.

11 ECG has signs of myocardial damage, such as ST segment, T wave changes.

12 accompanied by other arrhythmias such as tachycardia, bradycardia, conduction block or prolonged contraction of QT interval.

13 originated from the pre-systolic contraction of the left ventricle.

(2) Benign pre-contraction (functional pre-contraction, also known as simple pre-contraction):

1 No history of organic heart disease, more accidental discovery.

2 There are no obvious symptoms in the clinic, the activity is not limited, the heart is not big, and there is no organic heart murmur.

Before the 3rd stage, the contraction increased at night or at rest, and the number of contractions decreased or disappeared before the heart rate increased.

Before the 4th stage, the contraction was single-source, the interval was fixed, there was no R-on-T phenomenon, no short ventricular tachycardia, no QT interval extension and ST segment, T wave change, no conduction block, etc. Other ECG abnormalities, although the characteristics or diagnostic basis of pathological pre-contraction are listed above, clinical practice has proved that the diagnostic value of some indicators is not absolute, such as pre-systolic contraction, pre-term contraction or parallel rhythm Pre-systolic contraction, even paired pre-contraction or recurrent pre-contraction is not necessarily a pathological pre-contraction, children with benign pre-contraction may also have these ECG changes, in terms of electrocardiogram, multi-source Or polymorphic premature contraction, premature contraction, R-on-T precontraction, premature contraction of each type, with signs of myocardial damage or other types of arrhythmias, for pathological diagnosis Pre-contraction has a greater significance. Obviously, the more points are met, the greater the reliability of the diagnosis of pathological pre-contraction. However, the correlation between pathological pre-contraction and diagnostic support points remains to be further studied. Carry out, measure (integral) diagnosis It also needs to be further explored. Since the 1970s, the evaluation of the clinical significance and prognosis of ventricular premature systole has been widely used in the internal medicine field. Many scholars believe that the higher the grade, the worse the prognosis is. "The more opportunities there are."

In fact, the research data of Lown and Wolf are derived from the observation of patients with myocardial infarction. It has its particularity. It is considered that the Lown classification method is not suitable for ventricular premature contraction caused by other causes after non-myocardial infarction. There is no significant clinical significance in the evaluation of prognosis in patients with pre-sexual contraction. The ventricular premature contraction is different from that in adults in terms of etiology, clinical manifestations and prognosis. Therefore, the reference value of ventricular premature contraction Down classification is helpful for pediatric clinical work. Not big.

2. Qualitative diagnosis of pre-systolic contraction should adhere to the method of comprehensive analysis

When determining the pre-systolic nature, it is not possible to emphasize the diagnostic value of a single item unilaterally. It is necessary to pay attention to the above-mentioned ECG changes, and comprehensive analysis should be combined with other clinical data to determine the presence or absence of organic heart disease. In addition to a comprehensive system physical examination, two-dimensional and Doppler echocardiography should be performed and a three-dimensional image of the heart should be taken to observe whether the heart size, shape, intracardiac structure and blood flow direction are abnormal, and when suspected of myocarditis The troponin and serum enzymology should be tested, but the changes in myocardial zymogram are non-specific. The increase in total activity can be seen in many diseases and conditions. It is not possible to diagnose myocarditis and pathological preconditions based solely on elevated myocardial enzymes. Contraction, and detection of myocardial enzyme isoenzyme and troponin have higher specificity for assessing the presence or absence of myocardial damage, and its diagnostic value is also large, and conventional surface electrocardiogram examination is limited by the operation time.

Generally, only 50 to 100 cardiac cycles of ECG changes can be observed and recorded, often failing to reflect the overall appearance. Some pre-systolic and other arrhythmia are easily missed. Those with conditions should do 24h dynamic electrocardiogram, which can reflect 100,000 to 14 The electrocardiographic changes of 10,000 cardiac cycles significantly improve the positive diagnosis rate of arrhythmia, and help to determine the pre-systolic nature by observing the dynamic changes of pre-systolic contraction. The load ECG (active plate or bicycle exercise test) is determined. The nature of pre-contraction has a great help. If there is an increase in pre-contraction or pre-contraction after exercise, or even multi-source or pre-contraction, it is more pathological, but in recent years there have been domestic and foreign Scholars believe that some of the benign premature contractions caused by autonomic dysfunction may also increase significantly after exercise. Therefore, the diagnostic value of exercise tests needs to be re-evaluated. Regular exercise tests are only applicable to school-age children and older preschools. Children who do not have the equipment condition can not do the above exercise test, or because the child is too young to cooperate with the examination, it can be made for older children. Exercise 50 to 100 times or assist infants and toddlers to do sit-ups 50 times, so that the heart rate increases to 130-150 times/min or more. The ECG before and after exercise is recorded, and the number of contractions before and after the observation period is increased or decreased. In pediatric clinical practice, many doctors often mistake the premature contraction as a pathological premature contraction, and use the premature contraction on the electrocardiogram as the basis for the diagnosis of myocardial inflammation and other organic heart disease. This tendency needs attention, in fact Pre-contraction is not decisive for the diagnosis of myocarditis, nor can it be based on the presence or absence of pre-systolic contraction to assess whether the heart is normal. The nature of pre-systolic contraction and its prognosis can sometimes be determined by long-term follow-up observation. It is mainly necessary to identify the premature systolic contraction with indoor differential conduction. The latter has an atrial P' wave or retrograde P', which is hidden in the T wave of the previous sinus beat. The P' wave is unclear, and the esophageal electrocardiogram can be used to help identify. Second, the former compensatory interval is often complete, while the latter is incomplete.

3. The differentiation of atrial premature contraction with indoor differential conduction and ventricular premature contraction

The former has a P' wave, pay attention to identify the P' wave hidden in the T wave, and the compensatory interval is incomplete, which can be distinguished from the latter. In addition, when the atrial premature contraction, the QRS wave formed before the V1 lead is contracted. 85% showed right bundle branch block, and the QRS wave start vector was the same as the sinus, which could also help identify.

4. When the atrial premature contraction that has not been transmitted is overlapped with the ST segment or overlap with the T wave, the atrial premature contraction is not easy to identify, and is easily misdiagnosed as sinus block or sinus rest. When the second law changes, it is easy to be misdiagnosed as sinus bradycardia, or second degree atrioventricular block with ventricular sinus arrhythmia. The key to identification is to find atrial ectopic hidden in ST segment or T wave. P' wave, if necessary, esophageal electrocardiogram can help identify, according to the characteristics of typical ECG, the diagnosis of premature contraction in the junction area is generally no difficulty, but atypical should be differentiated from ventricular premature contraction and atrial premature contraction, due to the room Pre-sexual contraction and premature systolic contraction can be collectively referred to as supraventricular premature contraction. There is no recurrence of clinical significance between the two, and the premature contraction of the junction zone is associated with the differentiation of the indoor differential conduction and the ventricular premature contraction. Pre-sexual contraction with differential conduction, if there is retrograde P' wave before the diagnosis, there is no difficulty in diagnosis, but there is no retrograde P' wave before it is difficult to identify, but the following factors contribute to the diagnosis of premature contraction in the junction area :

1 There is a premature contraction in the same ECG;

The QRS wave formed by the contraction of the 2V1 lead in the mid-term is a right bundle branch block.

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