Radiofrequency catheter ablation (RFCA) is a new interventional method used to treat cardiac arrhythmias in recent years. The application of this method has accumulated considerable experience in adults, but it has not been reported in pediatrics in China. In our hospital, 9 cases of pediatric supraventricular tachycardia (SVT) were treated with RFCA from August 1998 to December 1999, and we report them as follows. Data and methods 1. Case selection All 9 cases were inpatients of our cardiovascular hospital. There were 7 male cases and 2 female cases. The ages ranged from 8 to 14 years, and the weights ranged from 18 to 54 kg. All of them had repeated episodes of SVT clinically, confirmed by ECG or multiple episodes affecting study, and required radical treatment. After admission, no organic heart disease was detected by routine physical examination, X-ray chest radiograph and echocardiography. Routine body electrocardiogram showed typical pre-excitation syndrome in 6 cases (3 cases of type A and 3 cases of type B), chronic atrial tachycardia in 1 case and normal in 2 cases. 2. Intracardiac electrophysiological examination According to the age and degree of cooperation, bupivacaine sacral block or lidocaine local anesthesia was used in this group. The right internal jugular vein and femoral vein were punctured percutaneously, and three to four 6F quadrupole electrode catheters were inserted and placed in the coronary sinus, high right atrium, bundle of Hitchcock, and right ventricle, respectively. In case of left-sided collateral tracts, the femoral artery was punctured and the large-tipped catheter was inserted retrogradely to the mitral valve. A multi-channel physiological recorder was used to record the I, II and IV leads of the ECG and the intracardiac high right atrium, coronary sinus, Hirschsprung’s bundle and right ventricle electrograms simultaneously with a recording paper speed of 100 mm/s. SVT was induced by graded incremental stimulation and S1S2 programmed stimulation in the atria, and SVT was induced again with isoproterenol drip if necessary to clarify the electrophysiological mechanism of SVT. The left bypass was taken under right anterior oblique fluoroscopy, and the large-headed catheter was used to precisely mark the bypass position on the mitral annulus, looking for small A and large V waves, with AV fusion as the ablation target. For the right bypass, the left anterior oblique fluoroscopy was taken, and the large-headed catheter was passed over the tricuspid annulus, and the left upper part of the Hirschsprung electrode was used to mark the bypass point by point at 12 o’clock in the clockwise direction, looking for small A and large V. The AV fusion was selected as the target point. In the case of dual atrioventricular node pathway (DAVNP), the large-headed catheter is used to find small A and large V waves between the Hirschsprung bundle and coronary sinus electrodes, with no H waves in between as the target point. 4. Judgment of treatment success After we find the target point, we start RF discharge ablation with low energy under cardiac monitoring until it is effective. If there is ventricular-atrial separation or V and A distance pulling apart, ventricular pacing shows decreasing ventricular-atrial conduction, and the earliest appearance of A wave in Hirschsprung’s beam electrogram indicates successful ablation. After the ablation, observe for 10 minutes, and then perform the evoked SVT and related electrophysiological examination. The specific criteria for judging the efficacy are referred to the Proceedings of the National Symposium on Non-pharmacological Treatment of Rapid Arrhythmias. Postoperative cardiac monitoring was performed for 24 hours, and all vital signs and related post-catheterization complications were noted. Results In this group of 9 pediatric patients, 7 cases of WPW were diagnosed by intracardiac electrophysiological examination. Among them, there were 3 cases each of left and right dominant bypass; 1 case of occult bypass; and 1 case of dual atrioventricular node pathway (slow and fast type). Persistent junctional zone recurrent tachycardia (PJRT) was diagnosed in 1 case. Pre-excited syndrome ablation bypass, AVNDP ablation slow pathway. 9 cases were treated radically and 1 case of PJRT recurrence. No serious complications occurred in any of them. One case had first-degree AVB, which was normalized intraoperatively. The other case had postoperative incomplete left bundle branch block, which returned to normal after 1 month in follow-up. Discussion 1. The electrophysiological mechanisms of supraventricular tachycardia are folding, ectopic autoregulation and triggered excitation, of which folding is the most common. In this group, 8 cases could be induced and terminated by programmed stimulation through intracardiac electrophysiological examination. All of them were confirmed to be caused by the folding mechanism. Based on clinical symptoms, body surface ECG manifestations and esophageal atrial pacing examination, the diagnosis of both preexcitation syndrome and atrioventricular node double pathway was not difficult. In a patient with PJRT, the clinical manifestation was chronic atrial tachycardia, which started 17 days after birth, and the attack was controlled by clinical application of acetaminophen iodofurazone, but recurred when the drug was stopped. Esophageal pacing can clarify the pathogenesis of most SVTs, while more complex patients can be diagnosed only by intracardiac electrophysiological examination. RFCA is superior to the earlier high-voltage DC ablation method. It is safe and reliable, can be repeatedly applied, without opening the chest, less painful for patients, less complications, and acceptable for adults and children. Because of the small extent of RF ablation, intracardiac electrophysiological examination and precise lesion localization are crucial. The dominant preexcitation bypass is located around the mitral or tricuspid annulus, and a Webster Halo catheter can be used to record the peri-tricuspid potential. For recording of pericuspid potentials, an electrode catheter can be left in the coronary sinus to determine the site of the bypass. In addition to finding the shortest time of AV in the dominant preexcitation syndrome, the recording of monopolar induction is also important, and the disappearance of the Δ wave and prolongation of AV time after discharge in sinus rhythm suggest the success of RFCA. rFCA has accumulated rich experience in adults, and has been carried out in pediatrics in Beijing, Guangzhou, and Wuhan in China since 1991, with a success rate of 83.6% to 97.8% without serious complications There were no serious complications. This case is a rare case of PJRT, with clinical manifestation of chronic supraventricular tachycardia, long-term use of antiarrhythmic drugs, and recurrence when the drugs are discontinued, so it is necessary to use RFCA again to achieve radical treatment and prevent the development of arrhythmogenic cardiomyopathy. In conclusion, RFCA is effective in the treatment of SVT in children without serious complications. However, further data are needed on its long-term effects on the myocardium of young infants.