Arrhythmia in children

Introduction to pediatric arrhythmia The development of arrhythmias is closely related to abnormalities in the heart conduction system. Normal cardiac activation originates from the sinus node. Through the heart conduction system, spread at a certain frequency, sequence and speed, the heart undergoes contraction and relaxation activities, called normal sinus rhythm; if the formation, frequency or conduction of cardiac dysfunction is abnormal, arrhythmia can be formed (arrhythmia ). basic knowledge The proportion of illness: 0.02% Susceptible people: children Mode of infection: non-infectious Complications: heart failure, shock, syncope, cerebral embolism

Pediatric arrhythmia etiology

There are two kinds of cardiomyocytes: one is working cardiomyocytes, which has contractile function; the other is cardiac conduction system, including sinus node, internode bundle, atrioventricular junction, atrioventricular bundle (His bundle), left and right bundles Supporting the Puyun wild fiber, the cardiac conduction system has the function of forming a heart stimulating, that is, self-discipline, both cardiomyocytes have the function of receiving and transmitting cardiac agonism, respectively called stress and conduction, and the working cardiomyocytes are physiologically In the case of no self-discipline, but under pathological conditions, can also form agonism, myocardial self-discipline, stress and conduction changes, can lead to arrhythmia.

1 Self-discipline: Self-disciplined pacemaker cells derived from the heart conduction system. Their electrophysiological properties are different from those of normal cardiomyocytes. The resting potential is unstable, and automatic slow depolarization occurs. Once the threshold potential is reached, spontaneous depolarization can occur. The process is excited.

Under normal circumstances, the sinus node produces the highest frequency of activation, controlling the whole heart activity, forming the pacing point of the heart, forming a sinus rhythm. When the sinus node pacing function is impaired, the next level of conduction system is usually It is the junction area that can replace the sinus node as the heart's pacemaker to maintain systolic and diastolic activity, forming an escape or escape rhythm, such as the self-discipline of the pacing point beyond the sinus node, exceeding the sinus node And control part or the whole heart activity, that is, the formation of premature beat or ectopic tachycardia, in recent years, myocardial electrophysiology research, the chamber junction area can be divided into three parts from top to bottom: the housing area, the junction area and the end District, the junction area is not self-disciplined.

2 stress: myocardial stimulation of a certain intensity can cause a reaction, manifested as electrical activity and mechanical contraction, the myocardial after the stimulation of a series of changes in stress, after an excitement, the stimulation of the butt The reaction occurs, this period is called the refractory period. In the initial stage of the refractory period, no reaction is produced, and the absolute refractory period is called. In the short period of time, only strong stimulation can cause a weak reaction. The relative refractory period, the refractory period of different parts of the heart is different, the atrioventricular node is the longest, the ventricular muscle is the second, the atrium is the shortest, the right bundle is longer than the left bundle. Under normal circumstances, the ventricular muscle should not The period is roughly equivalent to the QT interval in the electrocardiogram. The peak of the T wave is the absolute refractory period, followed by the relative refractory period. The slower the heart rate, the longer the refractory period, the faster the heart rate, the shorter the refractory period. The relative refractory period of the ventricle begins, which is equivalent to the peak of the T wave, and its stress can be abnormally enhanced. The weaker stimulus can lead to a strong reaction, called the vulnerable period. For example, the ventricular premature beat occurs at the top of the T wave. , easy to cause ventricular tachycardia, should not After a short time period as supernormal period, threshold required for a relatively low potential of this reaction occurs.

3 Conductivity: Myocardium can transmit impulse to adjacent tissues, and the conduction velocity of different parts of the heart is different. The slowest compartment of the chamber is 50-200mm/s, the fastest of the Puye wild fiber is 4000mm/s, and the bundle of chambers is 1000-1500mm. /s, ventricular muscle 300 ~ 400mm / s, myocardial conductivity and stress are closely related, conduction interruption in the absolute refractory period of the myocardium, the conduction velocity is significantly slowed in the relative refractory period, this physiological phenomenon is called interference, When the refractory period is abnormally prolonged, conduction block occurs.

The electrical activity of cardiomyocytes is caused by the different distribution and transport of various ions inside and outside the cell. At rest, the K ion concentration is higher in the cell than in the cell, while the Na ion is opposite. The positively charged K ion is out of the cell. Exudation, while negatively charged proteins and C1- ions are left in the cells, thus forming a negative polarization in the cell membrane, and a positively polarized state outside the cell membrane. Most of the myocardial cell membranes have a potential difference of -80 to -90 mV, called Membrane resting potential, when the myocardial cells are stressed, the polarization state is transferred to the depolarization process, the membrane potential is reduced (in absolute terms, that is, the negative value becomes smaller), and once it reaches the threshold potential level, the action potential is triggered and excited. The myocardial cell membrane has its own channels of different ions. During the agonistic process, the channel opens and closes, forming ion transport, inserting the microelectrode into the cardiomyocytes, and the action potential curve can be recorded during the activation of the cardiomyocytes, which can be divided into the order of the curve changes. Five phases, taking the action potential curve of ventricular muscle working cells as an example.

10 phase (depolarization period): When the membrane potential -90mV is reduced to -60mV (threshold potential), the sodium channel (fast channel) of the membrane is open, Na rapidly influx into the cell, and the negative potential in the cell disappears rapidly and turns 20mV. The depolarization curve rises rapidly and the sodium channel is closed after 1 to 2 ms of opening.

21 phase (fast repolarization period): Before the end of phase 0, when the membrane potential reaches 0mV, the chloride channel is open, Cl- rapid inflow and K outflow cause repolarization, membrane potential decreases, and the curve decreases rapidly.

32 phase (slow repolarization): the calcium channel (slow channel) is open, with slow Ca2, Na influx and slow K outflow, and the membrane potential remains permanently at 0 mV, forming a curved platform, followed by calcium channel closure.

Phase 43 (terminal repolarization): The potassium channel is open, a large amount of K flows out from the cell, the membrane potential rapidly returns to the resting potential level, the curve decreases rapidly, and the cardiomyocytes return to the polarization state, starting from the 0 phase to the 3 phase. The end process is called the action potential time course, which is about 300 to 500 ms.

54 phase (resting period): The ion pump (Na, K-ATPase) on the cell membrane actively operates, and Na and Ca2 are discharged to ingest K, so that the concentration of various ions inside and outside the cell is restored to the level before the activation, and the curve is maintained at A horizontal line, also known as electric diastolic period.

The ventricular myocytes action potential curve phase is compared with the conventional body surface electrocardiogram, the QRS wave is equivalent to the 0 phase, the J point is equivalent to the 1 phase, the ST segment is equivalent to the 2 phase, the T wave is equivalent to the 3 phase, and the QT interval is equivalent to the QT interval. Action potential duration, in the autonomic cardiomyocytes in the sinus node and atrioventricular node, 4 phases still have slow efflux of K and slow influx of Ca2 and Na. When K efflux decreases, the level of diastolic potential gradually Decrease, the curve gradually rises, forming a slope, called diastolic autodepolarization, when the threshold potential level is reached, triggering a new action potential, is the electrophysiological basis of self-discipline of such cardiomyocytes, sinus node and atrioventricular junction The cell resting potential is low, ranging from -40 to -70 mV. When the depolarization reaches the threshold potential level (-30 to -40 mV), only the calcium channel is open, and Ca2 slowly flows into the cell, except for the extremely slow, so the 0 phase curve. The rising speed is slow, and the amplitude is small, the phase 1 is unclear, the boundary of 2 phases is unclear, the conduction of conduction is slow, and the conduction block is easy to occur, but the self-discipline is high, which is called slow response cell.

The action potential curves of atrial myocytes and Puye wild cells are the same as those of ventricular muscle. The resting potential of membrane is about -90mV, the threshold potential is -60~-70mV, the fast channel of 0 phase is open, and a large amount of Na flows into the cell rapidly. Therefore, the phase 0 rises quickly and the amplitude is large, the excitation is fast, and the conduction block is not easy to occur, but the self-discipline is very low, which is called fast-reacting cells.

The effect of neurohumoral factors on myocardial physiological function: The neuromodulation of the heart is mainly through the vagus nerve and sympathetic nerve.

1 The effect of the vagus nerve on the heart:

A. Inhibit the self-discipline of the sinus node, so that the activation of the agitation is slowed or even suspended, and the inhibition of the atrioventricular junction is less.

B. Extend the refractory period of the atrioventricular junction and shorten the refractory period of the atrium.

C. The conduction of the atrioventricular junction area is slowed down and the atrial conduction is accelerated.

2 The effect of sympathetic excitation on the heart: contrary to the vagus nerve:

A. Improve the self-discipline of the sinus node and increase the frequency of stimulating.

B. It also strengthens the self-discipline of the room junction area and the bundle branch.

C. Shorten the refractory period of the myocardium.

Electrolyte and acid-base balance disorders, hypoxia and catecholamines can affect myocardial electrophysiological function, hypokalemia, hypoxia and adrenaline increase, causing myocardial self-regulation; while hyperkalemia, low temperature effect is opposite Hypokalemia, myocardial stress and conductivity increased in hypocalcemia, and stress and conductivity decreased in hyperkalemia.

Arrhythmia often occurs in heart disease. Congenital heart disease such as tricuspid valve is often complicated by supraventricular arrhythmia, such as premature atrial pulsation, paroxysmal supraventricular tachycardia, atrial flutter, large Vascular dislocation often complicated by complete atrioventricular block, atrial septal defect often occurs first degree atrioventricular block and incomplete right bundle branch block, etc., congenital heart disease can be followed by severe arrhythmia, Such as complete atrioventricular block, ventricular tachycardia, sick sinus syndrome, etc., acquired rheumatic carditis, rheumatic valvular heart disease, infectious myocarditis is the most common in acquired heart disease, long QT syndrome And mitral valve prolapse often occur ventricular arrhythmia, due to arrhythmia on hemodynamics, can lead to heart failure, shock, syncope and cerebral embolism, etc., causing the original heart disease to aggravate, cause heart rhythm other than the heart The most common disorder is electrolyte imbalance.

Drug reaction or poisoning, endocrine and metabolic diseases, autonomic dysfunction and emotional agitation, hypokalemia, hypomagnesemia and hyperkalemia are most common in electrolyte disorders; in arrhythmias caused by drug reactions It is most important to poison with digitalis preparations. In hypokalemia or hypomagnesemia, it is more likely to induce arrhythmias caused by digitalis poisoning. Antiarrhythmic drugs have many arrhythmogenic side effects, and acute central nervous system diseases such as intracranial hemorrhage Arrhythmia can occur, cardiac surgery, cardiac catheterization and anesthesia often have arrhythmia, neonatal and early arrhythmia can be associated with maternal pregnancy diseases, medication and childbirth complications, mothers with systemic lupus erythematosus, Most of the neonates have atrioventricular block, and the paroxysmal supraventricular tachycardia in infants is often induced by respiratory infections. Some arrhythmias, especially pre-contraction, often have no obvious cause, neonatal cardiac conduction system. Not mature, perfected by the age of 2, the pacemaker cell structure of the neonatal sinus node is primitive, and the sinus node artery is weak. Regulating the release of sinus node sensation, the sinus rhythm fluctuation range is large, in addition, the atrioventricular node area during the shaping process, the self-discipline is increased, the conduction function is not uniform, and the residual beam chamber abundance (Mahaim bundle), It is easy to cause supraventricular premature contraction and tachycardia, and can self-heal with age.

Pathogenesis

1. Classification of arrhythmia

Arrhythmias can be divided into three main categories according to their causes:

(1) Disorders of agitation: can be divided into two categories: sinus arrhythmia and ectopic rhythm, sinus arrhythmia including sinus tachycardia, sinus bradycardia, sinus arrhythmia, migratory rhythm and sinus Sexual quiescence, ectopic rhythm refers to ectopic pacemakers other than sinus node, such as decreased sinus node autonomy or blocked conduction, secondary pacing point excites, prevents cardiac arrest, called passive Position rhythm, one to two times said that escape, more than three times for escape rhythm, such as the increase in the self-discipline of the secondary pace point, the frequency of excitement exceeds the frequency of the sinus node, the first step in the sinus node Excited before, called active ectopic heart rhythm, one or two times is called premature beat, three times more than three times called tachycardia, the frequency is faster and regular called flutter, more quickly and without The regularity is called tremor, and the ectopic heart rhythm can be divided into atrial, handicap and ventricular according to the different pace points.

(2) Asymmetric conduction disorder: conduction disorder caused by physiological refractory period is called disturbance, most commonly occurs in the atrioventricular junction area. If multiple consecutive excites occur in the atrioventricular junction area, interference is called interfering atrioventricular separation. Pathological conduction block can occur between the sinus node and the atria, in the atrium, in the junction area and in the ventricle, respectively, called sinus conduction block, intraventricular block, atrioventricular block and bundle branch conduction. Blocking, when the activation through the atrioventricular bypass makes part of the ventricle first excited, called pre-excitation syndrome, which is abnormal in the conduction pathway.

(3) Coexistence of agitation and conduction disorders: such as parallel heart rhythm, ectopic rhythm with external block.

The most common sinus arrhythmia in children with arrhythmia is sinus tachycardia, followed by sinus arrhythmia, which accounts for 78.6% of arrhythmia electrocardiogram. Most of them are physiological phenomena, Beijing In the electrocardiogram room of Children's Hospital, 1039 arrhythmia were detected from 1969 to 1974. There were 1196 cases of arrhythmia (excluding sinus tachycardia and sinus arrhythmia). The percentage of arrhythmia was compared. (Pre-contraction) the highest incidence, of which the most ventricular, the second block of atrioventricular block, to more than once, the incidence of pediatric arrhythmia and adults are different, mainly atrial fibrillation significantly reduced compared with adults, only 0.6 %, adult atrial fibrillation is second only to ventricular premature contraction.

Atopic tachyarrhythmia is mainly caused by the phenomenon of reentry, that is, during the conduction process, a local conduction delay or one-way block occurs, and another normal myocardium is formed through another part of the normal myocardium; then the myocardial block with conduction block occurs. Gradually restore stress, so that the excitability can pass through it. At this time, if the first excited heart muscle has left the refractory period, it can produce the second activation, which is the phenomenon of reentry. Single reentry causes pre-contraction, and continuous reentry causes cardiac motion. Overspeed, increased autonomicity can also lead to rapid arrhythmia, myocardial cell diastolic membrane potential decreased, threshold potential increase or 4-phase automatic depolarization speed, can cause autonomic increase, the mechanism of ectopic tachycardia There is also a trigger activity, which is triggered by a normal action potential, which occurs after a normal depolarization, also known as post-depolarization.

2. Arrhythmia pathogenesis

(1) Abnormal origin of agitation: There are self-disciplined cells in many parts of the heart, which are self-disciplined. The electrophysiological basis is the 4-phase diastolic autodepolarization activity. The normal sinus node is the most self-disciplined, and the frequency of impulse is the most. Fast, the following are the special conduction tissue of the atrium, the junction area, the His bundle, the bundle branch and the Purkinje fiber. Because of the fastest depolarization rate during the diastolic phase of the sinus node, the impulse is delivered earlier and reaches the threshold potential. Throughout the heart, other parts of the pacemaker cells have been excited by the impulse transmitted by the sinus node before the membrane potential rises to the threshold, so their self-discipline is inhibited, when the myocardial lesions, such as injury, ischemia, hypoxia When the sinoatrial node is inhibited, the underlying autonomic cells are forced to release impulses. This is a protective mechanism that can produce escape or escape rhythm. If the autonomicity of the diseased cardiomyocytes is abnormally increased, the impulse is released. When the frequency is faster than the sinus node, an active ectopic rhythm is generated. One or two consecutive episodes are pre-contraction, and three or more episodes are tachycardia. The ectopic beats occur continuously and the frequency is faster. But the ruler is fluttering, and the irregulars are shaking.

(2) Agitated conduction disorder:

1 conduction block: If the heart's excitement can not reach the various parts at normal speed and order, it is conduction abnormality, and can be divided into physiological and pathological. The former refers to the absolute refractory period of the conduction system in the conduction process. Or relative refractory period, when the absolute refractory period is encountered, the excitement can not be transmitted. When the relative refractory period is encountered, the conduction is slow, also called the interference. The most frequent part of the disturbance is the atrioventricular junction area, if it is 3 times in succession. The above interference occurs at the junction of the atrioventricular junction, which is called interfering atrioventricular septum. The pathological conduction disorder is caused by the organic change of the conduction system, and the conduction disorder caused by the pathological extension of the refractory period. It is also called pathological block. Most slow arrhythmias are caused by this.

2 fold back: reentry is a common mechanism of supraventricular tachyarrhythmia, especially in pre-excitation syndrome, the conditions for completing the reentry are: one-way block; conduction slowdown; reentry anterior myocardial recovery should be faster Excited, such excitement is blocked in the proximal end of the one-way block, and then passed down through another path, and then reversed through the one-way block, at this time, if the original excited part has been detached from the refractory period, the excitement can be Re-enter the loop, repeating the loop and creating a reentry rhythm.

(3) Agitated origin disorders with conduction disorders: belong to this type of parallel rhythm, repeated heart rhythm, ectopic heart rhythm combined with blockade.

1 Parallel heart rhythm: Parasystole refers to the ectopic pacemaker in the heart, in addition to the sinus pacemaker point, there is another ectopic pacemaker that is active; the ectopic pacemaker is surrounded by afferent block Protection, the sinus impulse is a complete afferent block, it can stimulate at its own frequency and is not affected by normal sinus stimuli. For this reason, the two pacemakers are excited in parallel, at the ectopic pacemaker. In the case of blockade, as long as the surrounding myocardium is not in the refractory period, it can be circulated, forming an ectopic premature contraction, and can also form a parallel heart rhythm tachycardia. The pairing time varies, often with fusion waves, and the long ectopic beat interval is a simple multiple of the short ectopic beat interval.

2 ventricular late potential: ventricular late potential (ventricular late potential) is a delayed fractionated electrical activity in a small myocardial part of the ventricle during the diastolic period; these fragmentation electrical activities generally appear in the ST segment Inside, it is called ventricular late potential, which is characterized by low amplitude, high frequency pleomorphic spikes, sometimes equipotential lines between sharp waves, and the appearance of ventricular late potentials indicates the muscles isolated from each other in small myocardial muscles. There are unsynchronized electrical activities in the bundle. Due to the unsynchronized electrical activity, it may provide conditions for the occurrence of reentry stimuli, or it may be due to too little connection between the myocardial fibers, causing slow conduction, which is reflexive It provides important factors, so it can not only produce premature contractions, but often malignant ventricular arrhythmias.

1 Parallel heart rhythm: Parasystole refers to the ectopic pacemaker in the heart, in addition to the sinus pacemaker point, there is another ectopic pacemaker that is active; the ectopic pacemaker is surrounded by afferent block Protection, the sinus impulse is a complete afferent block, it can stimulate at its own frequency and is not affected by normal sinus stimuli. For this reason, the two pacemakers are excited in parallel, at the ectopic pacemaker. In the case of blockade, as long as the surrounding myocardium is not in the refractory period, it can be circulated, forming an ectopic premature contraction, and can also form a parallel heart rhythm tachycardia. The pairing time varies, often with fusion waves, and the long ectopic beat interval is a simple multiple of the short ectopic beat interval.

2 ventricular late potential: ventricular late potential (ventricular late potential) is a delayed fractionated electrical activity in a small myocardial part of the ventricle during the diastolic period; these fragmentation electrical activities generally appear in the ST segment Inside, it is called ventricular late potential, which is characterized by low amplitude, high frequency pleomorphic spikes, sometimes equipotential lines between sharp waves, and the appearance of ventricular late potentials indicates the muscles isolated from each other in small myocardial muscles. There are unsynchronized electrical activities in the bundle. Due to the unsynchronized electrical activity, it may provide conditions for the occurrence of reentry stimuli, or it may be due to too little connection between the myocardial fibers, causing slow conduction, which is reflexive It provides important factors, so it can not only produce premature contractions, but often malignant ventricular arrhythmias.

Pediatric arrhythmia prevention

1. Stable emotions maintain a calm and stable mood, relax the spirit, and not be overly nervous. Avoid overjoy, sorrow, and anger. Don't watch nervous TV, ball games, etc.

2. Self-monitoring Some arrhythmia often have aura symptoms. If you can find timely measures to reduce or even avoid arrhythmia. Some patients have developed a self-control method for their arrhythmia treatment, which can control arrhythmia with previous experience when it occurs.

3. Regularly check the body for relevant items and rationally adjust the medication. Electrocardiogram, electrolytes, liver function, etc., because antiarrhythmic drugs can affect electrolyte and organ function. After medication, the patient should be reviewed regularly and the medication effect and dosage adjusted.

Pediatric arrhythmia complications Complications, heart failure, shock, syncope, cerebral embolism

The complications of this disease are generally heart failure, shock, syncope and cerebral embolism. The prognosis of arrhythmia and the cause of arrhythmia, the cause, the evolution trend is related to severe hemodynamic disorder, which occurs on the basis of no structural heart disease. Upper arrhythmia including premature beats, supraventricular tachycardia and atrial fibrillation, most of which have a good prognosis; but patients with QT prolongation syndrome develop ventricular premature beats, which tend to evolve into polymorphic ventricular tachycardia or ventricular fibrillation. The prognosis is poor; in patients with pre-excitation syndrome, when atrial flutter or atrial fibrillation occurs and the ventricular rate is very fast, in addition to causing severe changes in blood flow, there is also the possibility of ventricular fibrillation, but most of them can be converted by direct current. And medication to control the onset, so the prognosis is still good.

Ventricular tachyarrhythmia and complete atrioventricular block with extremely slow heart rate, ventricular arrhythmia, severe sick sinus syndrome, etc., can quickly lead to circulatory dysfunction and immediately threaten the patient's life, atrioventricular block There is a significant difference in the prognosis of atrioventricular block caused by double bundle branch (three branch) block. The former has a good prognosis and the latter has a poor prognosis. Arrhythmia occurs on the basis of organic heart disease, as it does not cause itself. Obvious blood flow disorder, but not easy to evolve into severe arrhythmia, the prognosis is generally good, but if the basic heart disease is serious, especially with cardiac insufficiency or acute myocardial ischemia, the prognosis is generally poor.

Symptoms of arrhythmia in children Common symptoms Arrhythmia pale complexion, palpitations, palpitations, palpitations, bradycardia, lethargy, premature convulsions

History

Arrhythmia causes hemodynamic changes due to excessive heart rate, too slow and inconsistent atrioventricular contraction. The degree of hemodynamic effects depends on whether the heart is normal and how the heart compensates function. Common symptoms Heart palpitations, fatigue, dizziness, severe coma, shock, heart failure, babies can suddenly appear pale, refusal to eat, vomiting, lethargy, etc., children with paroxysmal tachycardia often have a history of recurrent attacks.

2. Physical diagnosis

Normal sinus rhythm infants 100 ~ 140 times / min, 1 ~ 6 years old 80 ~ 120 times / min, 6 years old and above 60 ~ 100 times / min, according to the heart auscultation and pulse rhythm and frequency, can make the following preliminary judgment:

(1) Heart rate is fast and uniform: sinus tachycardia, supraventricular tachycardia, ventricular tachycardia, atrial flutter with 1:1 or 2:1 atrioventricular conduction.

(2) Heart rate is fast and not uniform: atrial fibrillation, atrial flutter accompanied by irregular atrioventricular conduction, sinus tachycardia with premature beats.

(3) Slow and uniform heart rate: sinus bradycardia, complete atrioventricular block, sick sinus syndrome.

(4) The heart rate is slow and not uniform: the pacing bradycardia is slow and uneven, the sinus bradycardia is accompanied by premature beats, and the second degree of atrioventricular block.

(5) Heart rate is normal and not uniform: sinus arrhythmia, frequent premature beats, first degree atrioventricular block.

Some arrhythmias may have changes in heart sounds. When the first degree of atrioventricular block is blocked, the first heart sound is often weakened. The paroxysmal supraventricular tachycardia is the first heart sound. When the atrial fibrillation is strong, the heart sounds are different. The first heart sound is sometimes called "cannon sound" when the sexual atrioventricular block is blocked.

Trial stimulation of the carotid sinus can help identify tachyarrhythmia, so that the child lies supine, lateral neck, first touch the carotid artery in front of the sternocleidomastoid muscle, press the cervical vertebrae at the beat point of the mandibular angle and Massage, first press the right side, about 5 ~ 15s, while monitoring heart rate, if the heart rate has no change, you can change the left side, but can not press both sides at the same time, sinus tachycardia can reduce the heart rate slightly by pressing the carotid sinus Slow, but restore the original heart rate after relaxation; paroxysmal supraventricular tachycardia can terminate the episode or no change; atrial flutter increases the atrioventricular block after stimulating the carotid artery, so the heart rate can be reduced to the original Some 1/2.

Pediatric arrhythmia examination

Depending on the cause of the arrhythmia, the electrolyte and acid-base balance should be routinely examined; thyroid function and renal function should be checked; blood sedimentation should be checked, anti-"O", immune function.

Electrocardiogram examination

It is the main method for diagnosing arrhythmia. Firstly, find a lead with obvious P wave in each lead of ECG, measure PP interval, determine atrial rate, observe the law of P wave, whether the shape of P wave is normal, and whether PP interval is normal. Consistently, identify abnormalities, premature occurrence, slowness, sinus block or arrest, secondly understand the regularity and morphology of QRS waves, QRS time is not wide, normal shape, indicating that excitability originates from the atrioventricular bundle Above, from the sinus node, atrium or junction area, collectively referred to as supraventricular; if the QRS is widened, the shape is singular, then the ventricular septum from the atrioventricular bundle branch, measuring whether the RR interval is equal, find out the premature beat or escape Beat, then analyze the relationship between P wave and QRS wave. After each P wave, whether it follows the QRS wave, whether the PR interval is fixed.

Through the above electrocardiogram analysis to determine the main rhythm, is sinus rhythm or ectopic heart rhythm, ectopic rhythm should be known to be active or passive, from the atrium, the junction or ventricle, while paying attention to whether there is interference or conduction block, etc. ECG fashion should pay attention to whether there is baseline instability, etc., so as to avoid false positives as arrhythmia. For complex arrhythmia, you should choose a longer P-wave trace for longer traces. Generally use II or aVF lead synchronization. It is convenient to analyze the regularity and shape of P wave. For example, the P wave of conventional ECG lead is not obvious. You can add S5 or CR1 lead to display P wave. The former negative (red) is placed on the sternum handle and the positive (yellow) is placed. In the 5th intercostal space on the right edge of the sternum, the lead selection button is dialed to the I lead position; the latter places the negative (red) on the right forearm and the positive (yellow) on the 4th intercostal space on the right edge of the sternum. I lead positional tracing.

2. 24h dynamic electrocardiogram

Also known as Holter monitoring, it is a method of recording ECG for 24 to 72 hours continuously under active conditions, which can improve the detection rate of arrhythmia. It has been widely used in the diagnosis of arrhythmia and the effect of drug treatment. It has been reported that normal electrocardiogram is normal. Of the 62 patients, after 24h dynamic electrocardiogram monitoring, 30 patients (48%) found a variety of arrhythmias, patients with palpitations, dizziness, syncope and other symptoms associated with arrhythmia, conventional electrocardiogram did not find arrhythmia, such as dynamic Electrocardiogram monitoring for 24h, may detect frequent premature contraction, paroxysmal tachycardia, intermittent arrhythmia such as conduction block, dynamic electrocardiogram can also be quantitative analysis to determine the number of abnormal heart rhythm; various pre-contraction The total number and the percentage of total heartbeat within 24h; the number of paroxysmal tachycardia; and the number of heartbeats that continue each time, in addition, asymptomatic arrhythmias can be found; observe the relationship between symptoms and arrhythmia And whether arrhythmia is induced by activity or appears in silence, and pediatrics are often used in the following situations:

(1) Prevention of sudden death caused by arrhythmia after congenital heart disease: 11 cases of aortic dislocation after dynamic electrocardiogram monitoring, 7 cases of sick sinus syndrome, timely application of pacemaker can prevent Sudden death after surgery.

(2) Diagnosis of sick sinus syndrome: It can be confirmed by dynamic electrocardiogram that there is severe sinus bradycardia or supraventricular tachycardia, thus avoiding sinus node function examination.

(3) to find the cause of syncope: bradycardia or tachycardia can cause syncope, unexplained syncope patients by dynamic electrocardiogram examination, found that 10% to 25% caused by arrhythmia.

(4) Evaluation of the efficacy of antiarrhythmic drugs: ventricular premature contraction itself varies greatly, conventional electrocardiogram can not reflect the real situation, it is generally believed that after 24h dynamic electrocardiogram examination, the ventricular premature contraction after taking the drug is reduced by more than 50% compared with before administration. To be effective, more than 90% is effective, and it can also guide reasonable dosage time, dosage, etc.

(5) Check for pacemaker failure: intermittent dysfunction occurs in the pacemaker, which can only be detected by dynamic ECG monitoring.

3. Exercise ECG

Exercise can induce arrhythmia that does not occur when you are quiet, or aggravate arrhythmia at rest. Generally, the sub-maximal exercise test is used. After exercise, the heart rate increases by 170 times/min. Exercise test is often used for the diagnosis of the following arrhythmia. :

(1) Examination of sinus node function: Patients with sick sinus syndrome have a heart rate that is not slow even after being quiet, but the heart rate cannot be increased to normal after exercise.

(2) Evaluation of complete atrioventricular block: complete ventricular block in patients with post-exercise ventricular rate increased less than 10 times / min, suggesting that the block is below the atrioventricular bundle; such as exercise-induced ventricular phase Pre-contraction, which is a sign of syncope, requires a pacemaker.

(3) Evaluation of the nature of ventricular premature contraction: normal heart, frequent occurrence in quiet, single-source ventricular premature contraction, disappeared with heart rate after exercise, appeared immediately after exercise stopped, and can be compared before exercise Increase, this pre-contraction is benign, no need to use anti-arrhythmia drugs, on the contrary, with the increase of heart rate, pre-systolic contraction frequently, or pleomorphic pre-pathological contraction, should be treated in time.

(4) Diagnosis of long QT syndrome: patients with normal QT interval at rest may have a prolonged QT interval after exercise, and have T-wave malformation, sometimes exercise can induce ventricular tachycardia, causing syncope, should pay attention .

4. Transesophageal atrial pacing check

The lower end of the esophagus is close to the left atrium, so the method is indirect left atrial pacing. In recent years, pediatrics has been widely used in cardiac electrophysiological examination, and the clinical application is as follows:

(1) examination of sinus node function: sinus node recovery time can be measured, corrected sinus node recovery time and sinus conduction time, the normal values of children are 913.3ms ± 139.7ms, 247.7ms ± 51.3ms and 102.5ms ± 18.6 Ms.

(2) evaluation of atrioventricular conduction function: can measure the Venturi block, 2:1 block point, atrioventricular function refractory period and effective refractory period.

(3) Detection of atrioventricular nodal pathway: 23.6% of normal children have atrioventricular nodal pathways.

(4) Study of the reentry mechanism of supraventricular tachycardia: transesophageal atrial pacing can induce sinus node, intraventricular, atrioventricular junction and atrioventricular bypass reentry supraventricular tachycardia, synchronous esophageal electrocardiogram And V1 lead ECG, can distinguish P wave morphology, atrial activation sequence, determine RP, PR interval and atrioventricular conduction curve, identify different reentry mechanisms of supraventricular tachycardia, and choose effective drug treatment.

(5) For the pre-excitation syndrome, the following examinations can be performed: the atrioventricular accessory pathway is detected, and the recessive pre-excitation syndrome is diagnosed; the bypass refractory period is measured, the high-risk patient is initially screened, and the child bypass refractory period is <220 ms. When the incidence of atrial fibrillation is high, it is easy to cause ventricular fibrillation and is a high-risk patient.

(6) termination of supraventricular tachycardia episodes: the use of esophageal atrial pacing overspeed suppression method.

(7) Study efficacy: study the electrophysiological effects of antiarrhythmic drugs and observe the efficacy.

5. His bundle electrogram and intracardiac electrophysiological examination

Traumatic examination, His's beam electrogram is the potential map generated by the atrioventricular bundle excitation. The electrode is inserted into the right heart chamber through the vein, directly contacts the atrioventricular bundle, and records the excited electric wave, which is the His bundle beam diagram.

(1) Significance of each interval: The meaning and measurement of each phase of the Histogram of the beam is as follows:

1P-A interval: the distance from the beginning of the P-wave of the surface electrocardiogram to the starting point of the high-definition wave of the A-wave of the Histz electrogram is called the PA interval, reflecting the activation from the upper part of the right atrium to the lower part of the right atrium. The conduction time near the junction of the atrioventricular node is 20 to 40 ms.

2A-H interval: The distance from the starting point of the high wave of the A wave to the starting point of the H wave is called the AH interval, reflecting the conduction time from the lower right atrium to the atrioventricular node to the His bundle, normal value It is 60 to 140ms.

3H wave: a narrow two-way or three-way wave that lasts for 20 ms, reflecting the conduction time in the His bundle.

4H-V interval: the distance from the start of the H wave to the start of the V wave or the surface of the QRS wave of the surface electrocardiogram, called the HV interval, reflecting the excitatory from the bundle of the bundle of the atrioventricular bundle, the Puye fiber to the ventricular muscle The conduction time, the normal value is 35 ~ 55ms, the HV interval is the Hepu transmission time.

(2) His's beam diagram is used to:

1 Determine the location of atrioventricular block, according to the characteristics of His bundle electrograms, the location diagnosis of atrioventricular block is divided into His bundle above (main atrioventricular node level), within the His bundle and below the His bundle .

2 to determine the origin of ectopic beats and ectopic heart rhythms.

3 Identification of supraventricular tachycardia with indoor differential conduction and ventricular tachycardia.

6. Intracardiac electrophysiological examination

Inserting a lead into the heart chamber to record and/or stimulate different parts of the heart for electrophysiological studies can determine the precise location of the conduction block and the mechanism of tachycardia. Currently, it is often used in combination with tachycardia for radiofrequency ablation. The exact diagnosis of the mechanism of occurrence, the indications for intracardiac electrophysiological examination are:

(1) Defining the pathogenesis of supraventricular tachycardia and ventricular tachycardia, understanding the reentry loop, abnormal bypass or autonomic lesions, facilitating treatment, atrioventricular reentry and atrioventricular nodal reentry type supraventricular tachycardia Atrial flutter caused by reentry, ectopic atrial tachycardia and idiopathic ventricular tachycardia can be cured by radiofrequency ablation.

(2) High-risk children with sudden death or severe arrhythmia: sudden death after several years of congenital heart disease, mostly caused by severe ventricular arrhythmia, such as postoperative rehabilitation of children with tetralogy of Fallot, hemodynamic examination Normal, intracardiac electrophysiological examination can induce ventricular tachycardia, prone to sudden death, and timely treatment with drugs.

(3) Evaluation of high-risk patients with pre-excitation syndrome: Pre-excitation syndrome bypass pre-transmission effective refractory period 220ms, or when atrial fibrillation occurs, ventricular rate up to 200 times / min, can predict sudden death or cardiac arrest.

(4) Patients with unexplained syncope: Intracardiac electrophysiological examination may indicate severe bradycardia or tachycardia, thus guiding specific treatment.

(5) Study anti-arrhythmia drugs: study the electrophysiological effects of anti-arrhythmia and observe the curative effect. Although intracardiac electrophysiological examination is relatively safe, the laboratory should have all emergency medicines and equipment, including cardiopulmonary resuscitation, defibrillator, etc. In case of any eventuality.

Diagnostic identification of pediatric arrhythmia

Arrhythmias are primarily diagnosed by electrocardiography, but most cases can be diagnosed by medical history and physical examination.

1. Arrhythmia classification

Arrhythmia can be classified according to physiological basis or anatomical basis. Clinically, a combination of two classification methods is used to classify arrhythmia according to electrophysiological characteristics:

1 The origin of the activation is abnormal.

2 conduction disorders.

3 abnormal origin of agitation with conduction disorders, and then indicate the location of arrhythmia according to the region where arrhythmia occurs, such as pre-contraction or tachycardia can be divided into atrial, borderline or ventricular; conduction block can be divided into sinus room, Conduction block between the rooms, bundles or ventricles.

(1) sinus arrhythmia: stimulating originates from sinus node, but the rate of stimulating conduction is outside the normal range, which can be divided into sinus tachycardia, sinus bradycardia, sinus arrhythmia, and walking rhythm. The sinus is still.

(2) ectopic rhythm: the heart beat caused by the excitement outside the sinus node, called ectopic rhythm; can be divided into two categories:

1 escape or escape heart rhythm.

Pre-systolic contraction and tachycardia, flutter and tremor caused by pre-systolic or rapid ectopic activation.

(3) conduction block: heart block can be temporary, intermittent or permanent, according to the location of conduction block, can be divided into sinus room, atrial, interventricular, intraventricular (including bundle Branch) conduction block.

2. Arrhythmia electrocardiogram diagnostic analysis method

Electrocardiogram is of great significance for the diagnosis of arrhythmia, and often plays a decisive role in diagnosis. However, some arrhythmia are complicated or mixed with several types of arrhythmia, which makes it difficult to diagnose. Therefore, analyzing the arrhythmia ECG must be progressive according to certain rules. If necessary, it is necessary to analyze by means of a ladder diagram.

(1) ECG analysis method:

1P wave: firstly determine whether there is P wave in the conventional lead, and then judge the source of the excitation according to the shape, direction, velocity and regularity of the P wave and the relationship with the QRS complex. The sinus P wave is obtusely round. In the I, II, aVF, V5 lead erect, the aVR lead is inverted, the V1 lead is bidirectional, the rate varies with age, and the normal range of heart rate per minute is as follows: 110 to 150 times under 1 year old, 1~ 3 years old 90 to 130 times, 3 to 6 years old 80 to 120 times, 6 years old and above 60 to 100 times.

2P-R interval: With age and heart rate changes, the younger the age, the faster the heart rate, the shorter the PR interval, the shortest is 0.08s, and the longest is 0.18s.

3QRS wave group: analysis of the shape and interval of QRS complexes, help to determine the location of ventricular impulse formation and the excitatory process in the ventricle. If the shape and time limit of the QRS complex are normal, it can be determined as supraventricular stimuli. Downstream, if the QRS complex is malformed, it may be ventricular rhythm, bundle branch block, indoor block, supraventricular ventricular ventricular differential conduction or pre-excitation syndrome.

Then further analysis of the QRS complex is intermittent or continuous occurrence, its relationship with the P wave and the PR interval, in order to determine the type of arrhythmia.

(2) Application of ladder diagram in the diagnosis of arrhythmia: In the analysis of more complicated arrhythmia, according to the characteristics of electrocardiogram, graphically illustrate the origin of the activation and the conduction process, and the ladder diagram is a horizontal diagram. A schematic diagram of lines drawn by vertical lines and diagonal lines, usually in three rows, representing the atrium (A), the atrioventricular junction (AV) and the ventricle (V), and the vertical lines in the A and V rows from top to bottom. The P-wave and the QRS complex are respectively aligned, the oblique line in the AV line indicates the conduction process of the impulse in the atrioventricular junction, and the oblique line to the lower right indicates the impulse forward conduction, indicating to the upper right oblique line.

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