Supraventricular tachycardia (SVT) is one of the common arrhythmic emergencies in pediatrics, and its diagnosis and treatment have become more and more perfect due to the widespread use of transcatheter intracardiac electrophysiological examination and radiofrequency ablation, but its application is often limited in infants and children due to age and physiological peculiarities. Therefore, how to give timely and effective diagnosis and treatment in the shortest possible time has been a problem for pediatricians. In this paper, we summarize our experience in treating 43 cases of infants and children under 2 years old with SVT by transesophageal atrial pacing (TEAP) from 2000 to 2009, and emphasize the unique application value of TEAP in infants and children with SVT, in order to raise the awareness of primary pediatricians.
1. Materials and methods
1.1 Subjects A total of 43 cases of infants and toddlers under 2 years old with SVT rescued in our hospital from 2000 to 2009 were selected. There were 23 male cases and 20 female cases, with a sex ratio of 1.15:1; age 7.59±9.80 months (1 day-2 years), including 13 neonates.
1.2 Clinical diagnosis
There were 20 cases of simple SVT episodes, 16 cases of bronchopneumonia and other infections, 3 cases of postoperative precordial disease (TOF 1, VSD 1, VSD+PDA 1), 2 cases of fulminant myocarditis, and 1 case of muffled syndrome.
1.3 Diagnosis of body surface electrocardiogram
There were 29 cases of SVT, 14 cases of atrial flutter (including 3 cases of SVT alternating with atrial flutter), 1 case of junctional tachycardia, and 2 cases of suspected ventricular tachycardia. After termination of tachycardia, 8 cases showed typical pre-excitation syndrome.
1.4 Methods
All children underwent electrophysiological examination by TEAP, and the instrument was a DF-5A cardiac electrophysiological stimulator manufactured by Suzhou Oriental Electronic Instrument Factory. 6F quadrupole esophageal electrodes were inserted through the nasal cavity and fixed when the esophageal ECG showed bidirectional high P waves, and the cannula was inserted at a depth of 20-30 cm. Subsequently, the esophageal ECG was recorded for typing diagnosis, and after it was clearly identified as folded tachycardia, atrial tachycardia, and atrial flutter Tachycardia is terminated immediately with overdrive inhibition. If the child’s condition allows, a full set of esophageal electrophysiological examination can be performed again, and a total of 18 cases were completed.
2. Results
The mean ventricular rate was 233.31±46.79 beats/min faster during tachycardia episodes in this group of children.
2.1 Esophageal electrocardiography diagnosis
2.1.129 children with body surface ECG diagnosis of SVT, 23 cases were in folding tachycardia, 3 cases were in atrial tachycardia, and 3 cases were in sinus rhythm.
In 23 children with fold tachycardia, the esophageal ECG showed RP’
Three children in sinus rhythm with a mean ventricular rate of 245.8±24.15 beats/min had SVT-like phenomena due to P-T fusion on the body electrocardiogram caused by an overly fast heart rate. The esophageal ECG showed a normal P-R interval in one case and a prolonged P-R interval in two cases, with the diagnosis of I-AVB.
2.1.2 The esophageal ECG of 2 children with atrial flutter showed a mean atrial rate of 384.25 ± 47.73 beats/min and a mean ventricular rate of 190.83 ± 41.88 beats/min.
2.1.3 One child with junctional tachycardia was postoperative for precordial disease and had a ventricular rate of 188 beats/min.
2.1.4 Among the 2 children with suspected ventricular tachycardia, 1 case of esophageal ECG showed prolonged P-R interval and widened QRS, which was diagnosed as I-AVB combined with intraventricular conduction block, and the diagnosis was supported by body ECG after control of tachycardia with treatment. In another case, the esophageal ECG showed separation of P and QRS waves, and the atrial rate was greater than the ventricular rate, so the diagnosis was ventricular tachycardia, but after follow-up, it was found that the correct diagnosis for this child was junctional tachycardia with intraventricular conduction block.
2.2 Conversion therapy
Among the 23 children with fibrillation tachycardia, 20 cases of sinus rhythm were reversed by oesophageal pacing with overdrive inhibition, of which 5 cases had recurrent episodes after reversal and were discharged after combining anti-infection and antiarrhythmic drugs; 3 cases of atrial tachycardia were reversed in 2 cases, and 1 case resumed atrial tachycardia within seconds after reversal; 14 cases of atrial flutter were successfully reversed in 12 cases (including 2 cases after preoperative heart disease); 1 case of junctional tachycardia (after preoperative heart disease) was reversed by overdrive inhibition. One case of junctional tachycardia (post-operative) resumed within seconds of the conversion of sinus rhythm by tachy suppression, which was considered to be due to increased autoregulation. The success rate of transesophageal atrial pacing was 83% (34/41).
In two children with fulminant myocarditis, because of poor cardiac function and ineffective antiarrhythmic drugs, esophageal electrodes were left in place for 24-72 hours to stop recurrent episodes of tachycardia in time until cardiac function improved, which played a very important role in the rescue of the children.
3. Discussion
SVT is an episode of tachycardia involving the conduction system of the bundle of Hirschsprung or above, and its mechanism of occurrence is mainly folding and, in a few cases, abnormally increased autoregulation. The main manifestations are folding tachycardia, atrial tachycardia, atrial flutter, and junctional tachycardia involving the atrioventricular bypass and dual pathways. In infants and children, SVT often has a faster ventricular rate, so a significant proportion of children with atrial wave relationships cannot be clearly shown on the surface ECG, and the fusion of P and T waves cannot be clearly shown, whereas the esophageal ECG can clearly show the P waves that cannot be shown on the surface ECG and help to diagnose the staging of tachycardia. Most of the cases in this group could be clearly typed by esophageal electrophysiological examination, and only one case of crossover tachycardia with intraventricular block was misdiagnosed as ventricular tachycardia, which was clearly diagnosed after follow-up, suggesting that both the body surface ECG and esophageal ECG cannot show H waves of the Hirschsprung bundle, which has some limitations in diagnosis and cannot completely replace intracardiac electrophysiological examination. In our group, 14 cases of atrial flutter were clearly diagnosed by body surface ECG showing sawtooth waves, but some children with 1:1 or 2:1 atrioventricular conduction rule with fusion of P and T waves were reported to be easily misdiagnosed, which also required esophageal ECG for differentiation.
The literature reports an increased risk of acute heart failure if the heart rate is greater than 250 beats/min in the first year of life and greater than 220 beats/min in childhood, especially in infants under 4 months of age, with an incidence as high as 35% [4, 5]. In our group, all infants and children younger than 2 years of age had a mean ventricular rate of 233.31±46.79 beats/min. The relatively rapid heart rate is very likely to cause cardiac insufficiency, which is more likely to lead to heart failure if accompanied by organic heart disease. Clinically, SVT in infants and children is a difficult therapeutic choice considering the negative inotropic force of antiarrhythmic drugs and the inadvisability of electrical cardioversion, which has become a problem for pediatricians. In this regard, the advantages of TEAP are obvious, and since the folding mechanism causes more than 96% of SVT, the tachycardia of most children can be induced and terminated by esophageal pacing program control. Oesophageal overdrive pacing is not only effective and rapid in terminating tachycardia and making preliminary typing diagnosis, but also simple, safe and repeatable, especially in rescuing children with fulminant myocarditis, whose timely and effective performance cannot be ignored. The success rate of transesophageal atrial pacing in this group was 83% (34/41), and the application of indwelling esophageal electrodes in two children with fulminant myocarditis effectively controlled the onset of arrhythmia and bought time for resuscitation, suggesting that esophageal atrial pacing has good application value in infants and children with SVT.
As a noninvasive cardiac electrophysiological examination technique, it is more operable and timely than intracardiac electrophysiological examination, and is suitable for pediatric professionals in primary care units to master and apply, and should be further popularized.