For more than a decade, radiofrequency catheter ablation (RFCA) has been widely used to treat preexcitation syndrome, atrioventricular nodal tachycardia, atrial tachycardia, atrial flutter, idiopathic ventricular tachycardia, and frequent premature ventricular beats with excellent results. Because of its high success rate, low invasiveness and relative safety, it has become the method of choice for the eradication of these arrhythmias. Radiofrequency catheter ablation for the treatment of pediatric tachyarrhythmias has been reported both domestically and internationally, and although the number of cardiac centers performing pediatric radiofrequency procedures and the number of cases treated is much lower than that of adults, the success rate and complications are the same as those of adults. 2004 Van Hare et al [1] reported the results of radiofrequency ablation of 2,761 pediatric paroxysmal supraventricular tachycardias aged 0-16 years, with an overall success rate of 95.7% and no deaths. Kugler et al [2] compared the US pediatric radiofrequency catheter ablation registry data into two groups (1991-1995 and 1996-1999) and showed that the ablation failure rate improved from 9.6% in the early years to 4.8% in the recent past, and complications decreased from 4.2% to 3.0%. As RF ablation techniques mature and indications tend to be younger, there is controversy as to whether there is an increased risk of RF ablation procedures in infants and children. 2001 Blaufox et al [3] reviewed the results of RF ablation in 137 infants from birth to 1.5 years of age enrolled in 27 centers in the United States, with no significant difference in success rates or complications compared to 5,960 non-infants. Therefore, this data supports the choice of radiofrequency ablation by experienced electrophysiologists in infants with frequent episodes of tachycardia, when antiarrhythmic drugs are not effective or when tachycardia is life-threatening. 2005 Aiyagari et al [4] reviewed data from two major electrophysiology centers in the United States, and the immediate/distant success rates of radiofrequency ablation in the control weight group ≤15 kg and the weight group 15.1 to 20 kg and In October 1991, the electrophysiology department of the First Hospital of Peking University, where I work, was the first to successfully treat tachyarrhythmias in children with radiofrequency catheter ablation in China [5], and to date there have been more than 800 cases with a total success rate of >95% and complications <1%. It has been demonstrated that radiofrequency catheter ablation can also be used to treat tachyarrhythmias in children in a relatively safe and effective manner. < 1. Pre-excitation syndrome Pre-excitation syndrome is the most common form of supraventricular tachycardia in pediatric patients, which can occur since fetal life. Those <1 year of age often present with restless tachycardia that is difficult to control with antiarrhythmic drugs. Persistent tachycardia can lead to cardiac insufficiency. When combined with organic heart disease, the risk of sudden death is increased. Sudden onset of very rapid tachycardia can lead to syncope due to a sudden drop in cardiac output. In recent years, with the increasing sophistication of radiofrequency ablation methods for pediatric pre-excitation syndrome, the choice of radiofrequency ablation for school-age children with symptomatic paroxysmal tachycardia and for infants with poor pharmacologic outcomes is no longer controversial. Risk stratification for asymptomatic pediatric prodromal syndrome is difficult, and both retrospective and prospective studies have shown that the risk stratification criteria for asymptomatic prodromal syndrome in adults are not applicable to the pediatric population. Given the large amount of practical experience suggesting the safety of invasive electrophysiological examinations, more pediatric electrophysiologists are choosing to assess risk and select appropriate treatment with electrophysiological examinations [6]. 1.1 Evaluation Radiofrequency catheter ablation for pediatric preexcitation syndrome (atrioventricular bypass-induced atrioventricular fold tachycardia) is a well-established method with proven efficacy and an overall success rate of >95% [1,3,7], which is not significantly different from adult data. The location of the bypass affects the ablation success rate, with a higher success rate for left free wall bypass (97.8%) than for right free wall bypass (90.8%), and approximately 3% of ablations were abandoned due to interval bypass [1].The registry data of Blaufox et al [3] showed that the success rate of radiofrequency ablation for preexcitation syndrome in infants <1.5 years of age (weight 1.9-14.8 kg) was 94.5%, with major complications 4.6%, while the success rate for non-infants was 91.5% with major complications 2.1%, with no significant difference between the two. Radiofrequency catheter ablation has been shown to be safe and effective for the treatment of preexcitation syndrome in children and infants. < p=""> 1.2 Patient selection The age at which the procedure is selected depends on the clinical symptoms, the location of the bypass, and the experience of the operating surgeon: ① Radiofrequency ablation of the left atrioventricular bypass should be selected with extreme caution in children < 2 years of age because of the left heart catheter manipulation and the possible corresponding complications, such as arterial occlusion and aortic valve injury. ②The risk of third-degree atrioventricular block in right anterior and septal bypass ablation is high, and caution should be exercised in selecting patients of any age. ③The right free wall bypass and right posterior bypass are relatively safe to operate. If the clinical manifestation is restless tachycardia or frequent episodes of tachycardia, which cannot be easily controlled by antiarrhythmic drugs, in order to prevent the occurrence of cardiac insufficiency, ablation surgery can be selected in younger children according to the experience of the surgeon. 1.3 Methodology The electrophysiological characteristics of the atrioventricular bypass are now well understood, and the techniques for localizing the bypass are well established. Based on the characteristics of children, intraoperative attention should be paid to the selection of ablation electrode catheters of appropriate thickness and curvature according to the age of the child and the location of the bypass. Atrioventricular node regurgitation tachycardia caused by a dual atrioventricular node pathway is one of the most common supraventricular tachycardias in adults, and is relatively less common in children than in adults, with the incidence increasing with age. It is extremely rare in infancy, and the incidence in childhood is only 13%-16% of supraventricular tachycardia, with the peak of symptoms occurring after the age of 8 years and becoming the most common cause of supraventricular tachycardia by adolescence [8]. 2.1 Evaluation The application of radiofrequency ablation for the treatment of atrioventricular nodal fold tachycardia in children is increasingly reported. Early methods of modifying the fast pathway of the AV node by ablation are currently rarely used because of their high susceptibility to complete AV block. Instead, the slow AV node pathway has been modified by ablation with good results, and the risk of complications from complete AV block has been significantly reduced. The success rate of ablation of AV nodal fold tachycardia in children is 95.7% to 97%, with a recurrence rate of 5% to 10% [9,10]. 2.2 Patient selection Although the success rate of radiofrequency ablation for pediatric AV node folding tachycardia is not significantly different from that of adults, the recurrence rate and the risk of complications of complete AV block are relatively higher than those of adult patients, which may be related to the following factors: ? the immaturity of AVN development in childhood, and the intensity and timing of delivering RF ablation energy tend to be more conservative than in adults;? The relatively small size of the AV node in young children leads to a higher chance of complete AV block than in adults. Thus, RF ablation treatment should be taken with caution for AV node folding tachycardia in young children. For those with obvious symptoms, oral antiarrhythmic drugs can be taken to control the number of episodes, and then RF ablation treatment can be selected when appropriate after ageing (>7 years) and relative maturity of the AV node development [9]. 2.3 Methodology The 7F plus rigid ablation electrode catheter was selected, along the tricuspid annulus forward to around the coronary sinus orifice, and the small A and large V waves without H waves in between were marked and discharged at the A-wave fragmentation. The presence of intermittent premature junctional beats, escape beats or short paroxysmal junctional rhythms on discharge is a sign of possible successful ablation. In order to reduce/avoid the occurrence of complete AV block, the following points should be noted during ablation: ① Ablation in sinus rhythm; ② Trial discharge from 50℃/15-25W during discharge, and gradually and carefully increase the temperature and wattage according to the response, and multiple discharges for a short time; ③ If PR interval or AH interval, rapid junctional tachycardia with ventricular-atrial separation of heart rate or change of catheter position occurs during discharge, it should be immediately Ablation should be stopped immediately. 3. Atrial tachycardia Atrial tachycardia is referred to as atrial tachycardia, which is of great clinical significance in pediatrics. Atrial tachycardia is not uncommon in children, accounting for about 4% to 10% of supraventricular tachycardia in children. Atrial tachycardia can be characterized as short-onset self-limited, paroxysmal sustained, or sustained restless tachycardia. Continuous restless atrial tachycardia can cause cardiac dysfunction. 3.1 Classification of atrial tachycardia There are several ways to classify atrial tachycardia. Atrial tachycardia can be classified according to the mechanism by which it occurs: refractory, autoregulatory, and triggered activity. Lesh et al [12] classified atrial tachycardia into four major categories based on the basis of atrial tachycardia formation: focal atrial tachycardia, inappropriate sinus tachycardia, large folded atrial tachycardia (including typical atrial flutter, atypical atrial flutter and incisional folded atrial tachycardia) and atrial fibrillation. 3.2 Evaluation Radiofrequency ablation has become the method of choice for the nonpharmacologic treatment of atrial tachycardia. The success rate of ablation of focal atrial tachycardia is 60% to 100%, and the main factor affecting the success rate is the location of origin of atrial tachycardia [13]. Atrial tachycardia can originate in any part of the atrium or in anatomical structures connected to the atrium, such as pulmonary veins and coronary sinuses. In children, right atrial tachycardia and monogenic atrial tachycardia are more common, and the success rate of radiofrequency ablation is >90%. In experienced electrophysiologists, the success rate of left atrial tachycardia ablation is close to that of right atrial tachycardia. 3.3 Patient selection Currently, for atrial tachycardia, radiofrequency ablation is not used as first-line treatment, and antiarrhythmic drugs are mostly used for treatment, but the efficiency is low. For children with signs of cardiac insufficiency, radiofrequency ablation should be selected early or used as the first-line treatment option. 3.4 Methodology Atrial tachycardia can originate from almost any part of the left or right atrium, and left-sided atrial tachycardia mostly originates from the pulmonary vein port. For ablation of atrial tachycardia, marker electrodes need to be placed in the coronary sinus and the bundle of Hirschsprung, and HALO electrodes need to be placed in the right atrium if necessary to help localize the atrial tachycardia. The main marking method is excitation sequence marking, using the earliest A-wave lead of the ECG or intracardiac electrogram as the reference lead, and the earliest atrial excitation point is the target point for ablation. For left atrial tachycardia ablation, the ablation electrode catheter can reach the left atrium through the anatomically unclosed foramen ovale in a few children. If there is no unclosed foramen ovale or atrial septal defect, the atrial septum should be punctured to deliver the ablation electrode catheter into the left atrium. 4. Atrial flutter Atrial flutter (AF) is a relatively rare type of supraventricular tachycardia in adults, and its incidence is much lower than that of atrial fibrillation. The incidence of atrial flutter is higher in children than in adults and can occur from the fetal and neonatal period to older children, whereas atrial fibrillation is rare [14]. Atrial flutter in children is seen in: (i) congenital heart disease with valve anomalies complicated by right atrial enlargement; (ii) postoperative congenital heart disease, especially surgery involving right atriotomy; (iii) in combination with pathological sinus node syndrome; and (iv) in the absence of organic heart disease. The prognosis is good for those with normal cardiac structure. 4.1 Classification of atrial flutter The classification and nomenclature of atrial flutter has long been confusing. The Recommendations and Guidelines on the Treatment of Arrhythmias (2004) of the Chinese Society of Cardiac Electrophysiology and Pacing/Chinese Journal of Cardiac Arrhythmology recommends that atrial flutter be classified into two categories: (1) typical atrial flutter: including cis-clockwise (II, III, aVF leads negative, V1 leads positive flutter waves) and anticlockwise (II, III, aVF leads positive, V1 leads negative flutter waves) flutter waves. Atrial flutter associated with surgical incision or patch is classified as atrial tachycardia. 4.2 Evaluation ①Typical atrial flutter: linear ablation in the right atrial isthmus resulting in bidirectional block has a positive efficacy with a success rate of 90%-95% and a low recurrence rate, and has become the first-line treatment. ②Atypical atrial flutter or atrial tachycardia/atrial flutter: conventional electrophysiological labeling methods are difficult to successfully label and ablate. However, the new three-dimensional electroanatomical labeling system-Carto labeling system can display the cardiac cavity structure in three dimensions, show conduction pathways, localize memory and potential amplitude in two or three dimensions. Since its application, with the accumulation of experience, the success rate has significantly improved, the recurrence rate has decreased, and the X-ray burst time has been significantly shortened. 4.3 Patient selection ① Typical atrial flutter: except for the etiology of atrial volume overload due to structural abnormalities of the heart, such as ineffective electrical diversion or antiarrhythmic drugs, RF ablation can be selected in children aged >1 year (the minimum age for selecting the procedure is based on the experience of the electrophysiologist). In a small number of children, atrial flutter is due to pathological sinus node syndrome, which after successful ablation manifests as sinus arrest and/or sinus bradycardia and may require implantation of a permanent pacemaker, which needs to be explained to the child’s parents before the procedure. (2) Atypical atrial flutter or atrial folding atrial tachycardia/atrial flutter: RF ablation is not used as the first-line treatment because of the difficulty of successful labeling and ablation by conventional electrophysiological labeling methods. In the conditioned electrophysiology room, the application of 3D calibration system is optional. 4.4 Methodology ① Radiofrequency ablation of typical atrial flutter: typical atrial flutter has a clear fixed folding mechanism, and successful ablation depends on interrupting the large folding loop, and the most effective method at present is linear ablation of the right atrial isthmus. In the left anterior oblique position at 45°, the ablation electrode catheter is ablated from the tricuspid annulus below the coronary sinus orifice, marked to the small A large V as the starting point, with a preset temperature of 60°C. Each retraction of 2-3 mm is ablated for 20-30 s, and the ablation catheter is gradually retracted to the inferior vena cava. ② Radiofrequency ablation of atypical atrial flutter or atrial tachycardia/atrial flutter: the folding loop and the critical isthmus are not constant, and the location of the ablation line must be determined according to the specific conditions of different patients. The location of the foldback loop is difficult to define with conventional multipolar catheter landmarking techniques, especially in patients with complex post-operative precordial disease. The new three-dimensional electroanatomical marking system-Carto system and non-contact balloon catheter marking system can visualize the record of intracardiac electrical conduction and the key isthmus, and design their own unique ablation lines for different patients, and some experience has been accumulated. 5. Idiopathic ventricular tachycardia and premature ventricular contractions Ventricular tachycardia without organic heart disease, called idiopathic ventricular tachycardia (idiopathic ventricular tachycardia) is rare in children [15] and its epidemiological data are very limited. A total of 800 children and infants with tachycardia treated with radiofrequency ablation in the author’s electrophysiology unit, including 52 cases of idiopathic ventricular tachycardia, and idiopathic ventricular tachycardia accounted for 6.5% of tachycardia in children in our data. Pfammatter et al [15] reported 98 cases of pediatric idiopathic ventricular tachycardia with an age of onset of 5.4 (0.1-15.1) years, of which 27% occurred in infancy. 36% of the 98 children had clinically or echocardiographically confirmed left ventricular insufficiency, of which 1/3 (12% of all cases) had severe symptoms (heart failure or syncope). Most of the children (64.2%) were not taking antiarrhythmic drugs during follow-up, with a mean follow-up of 47 months, and no patient died. The rate of spontaneous recovery of ventricular tachycardia in infants was 89%, with a better prognosis than in those with onset after 1 year of age (56% spontaneous recovery rate of ventricular tachycardia). Premature ventricular contractions without organic heart disease are very common arrhythmias in childhood and most have a good prognosis. Occasional premature contractions are clinically asymptomatic and are often detected during physical examination or electrocardiogram. These premature beats, although benign, may manifest as antiarrhythmic drug tolerance and seriously affect the quality of life of the child. Prolonged and frequent premature beats, such as >10,000 beats/24hr or >20%, may also lead to left ventricular enlargement and cardiac insufficiency, and such patients selected for successful radiofrequency ablation therapy have been followed up with significant improvement in left ventricular function, with a significant reduction in left ventricular end-diastolic internal diameter (LVDd) and a significant increase in left ventricular ejection fraction (LVEF) [16,17]. 5.1 Evaluation Radiofrequency ablation for idiopathic ventricular tachycardia has been widely used with mature methods and high success rates. Among them, ventricular tachycardia with agonistic origin in the right ventricular outflow tract and ventricular tachycardia in the left ventricular septum are the most common and have a high success rate. Ventricular tachycardia originating from other sites has a lower success rate. Ventricular tachycardia complicated by organic heart disease is difficult to mark, has a low success rate, and has a high recurrence rate. Most ventricular tachycardias originate in the right ventricular outflow tract. Radiofrequency ablation is safe and effective for frequent monogenic ventricular premature beats originating in the right ventricular outflow tract without organic heart disease, with a success rate of 81% to 83%. The main factor affecting the success of ablation is that some patients have premature beats originating outside the epicardium or right ventricular outflow tract [16-18]. 5.2 Patient selection ① Idiopathic ventricular tachycardia: it has become the first-line clinical treatment because of the mature method and positive results. In pediatric idiopathic ventricular tachycardia, such as frequent episodes of ventricular tachycardia with significant symptoms and unsatisfactory control by antiarrhythmic drugs, radiofrequency ablation can be chosen. The procedure of radiofrequency ablation of right ventricular outflow tract ventricular tachycardia is relatively safe for pediatric patients, and the age of the procedure can be relatively relaxed. The minimum age of surgery for right ventricular idiopathic ventricular tachycardia in the author’s patient group was 1 year and 7 months. Ventricular tachycardia in the left ventricular septum should be selected with extreme caution in children < 2 years of age because of the risk of injury to the left bundle branch due to the left heart catheterization and possible complications associated with the procedure, especially at younger ages. Ventricular tachycardia originating from other sites, as well as ventricular tachycardia complicated by organic heart disease, is more difficult to speculate and has a lower success rate, so patients should be selected with care. In the electrophysiology room, we can choose to apply the three-dimensional labeling system, and the success rate is improved. ②Ventricular premature beats: frequent ventricular premature beats (>10,000 beats/24hr) originating from the right ventricular outflow tract or left ventricular mid-posterior septum, with obvious symptoms that affect life or study, and echocardiography or cardiac MRI showing left ventricular enlargement and reduced ejection fraction can be selected for radiofrequency ablation therapy. Ventricular premature beats originating from sites other than the right ventricular outflow tract and left ventricular septum have a relatively low success rate due to the difficulty of marker measurement, and those with severe symptoms may choose radiofrequency ablation therapy at the discretion of the electrophysiologist’s experience. 5.3 Methodology ①Ventricular tachycardia/premature ventricular contractions originating from the right ventricular outflow tract: the method of pacing calibration is used: the ablation catheter is used for point-by-point calibration in sinus rhythm, and the QRS wave group pattern in the 12 leads of pacing is recorded to be exactly the same as the QRS wave group pattern during ventricular tachycardia/premature ventricular contractions as the ablation target. Ventricular tachycardia/premature ventricular contractions originating from the left ventricular septum: the excitation sequence is used: ventricular tachycardia is induced, and the earliest point of ventricular excitation is found in the sustained state of ventricular tachycardia (during premature ventricular contractions and premature contractions) with the ablation catheter, and the local potential of the ablation target is 320 ms earlier than that of the body ECG, and a high-frequency, low-amplitude P-potential (Purkinje fiber potential) is seen in front of the V-wave of the target.