Koch's triangle in pediatric age: correlation with extra- and intracardiac parameters.

The atrioventricular node is situated in the lower atrial septum, at the apex of the Koch's triangle. The dimensions of the Koch's triangle are studied in adult humans, while no data exist about them in pediatric age. The knowledge of the dimensions of Koch's triangle in childhood is very important for safe and correct application of radiofrequency energy during transcatheter ablation. The dimensions of Koch's triangle were determined in 69 human pediatric hearts. The median age of the children was 3 months, with a range from 1 day to 14 years, 30 were female and 39 were male. Relations between body weight (extracardiac parameter) and tricuspid valve diameter (intracardiac parameter) were determined in all hearts to show morphometric modifications with growth. The distribution of body weight was not Gaussian and no correlation could be obtained between Koch's triangle dimensions and body weight. However, it was possible to identify that the mean ratio between the cathetus of the Koch's triangle corresponding to the annulus of the tricuspid valve and the tricuspid valve diameter was 0.45 +/- 0.16, with a highly significant correlation coefficient (r = 0.653, P < 0.001). Therefore, by knowing: (1) the diameter of the tricuspid valve, and (2) the constant ratio between the cathetus of the Koch's triangle and the tricuspid valve diameter, it is possible to calculate the length of the segment of the tricuspid annulus along which the transcatheter application of radiofrequency current can be applied to ablate the slow-pathway, thus reducing the risks of damage of the atrioventricular node.

[Mid-term clinical condition and prognosis in adrenergic ventricular tachycardia in children with apparently normal hearts]. / Clinica e prognosi a medio termine delle tachicardie ventricolari adrenergiche in bambini con cuore apparentemente sano.

INTRODUCTION: Ventricular tachycardia is the most common diagnosis among children with exercise or emotion-related syncope. The aim of the study was to assess the prognosis and the clinical course of children, without long QT syndrome, with exercise-related ventricular tachycardia and apparently normal heart. METHODS: Since January 1984, we studied 14 children (mean age 9.7 +/- 3.8 years) with exercise-related ventricular tachycardia, and, at the initial detection, without demonstrable heart disease, as assessed by clinical evaluation, electrocardiogram and mono-bidimensional echocardiogram. Six patients had exercise related syncope, 1 exercise intolerance and 7 were asymptomatic. All patients underwent exercise testing on treadmill and 24-hour ECG monitoring. All patients were treated with antiarrhythmic drugs. All patients were tested by exercise testing and 24 hour ECG monitoring, alternatively, every six months, during therapy or after complete wash-out of the drug used. RESULTS: Ventricular tachycardia, detected by exercise testing and Holter monitoring, was polymorphic in 4 symptomatic patients, monomorphic with left bundle branch block morphology and inferior axis in the others. The mean rate of monomorphic ventricular tachycardia was 224 +/- 35 bpm in the symptomatic children and 180 +/- 33 bpm in the others (p = 0.03). Successful chronic treatment was achieved with beta-blockers in 5 cases, propafenone in 6, sotalol in 2 and flecainide plus metoprolol in 1. During follow-up (6 +/- 2.7 years), 1 patient with polymorphic ventricular tachycardia, on therapy, suddenly died during exercise, the other symptomatic patients had no variation of their arrhythmia on routine tests, except 1 who, after propafenone was stopped, had ventricular fibrillation during exercise testing. Among the 7 asymptomatic patients, 5 had no evidence of ventricular tachycardia on routine test after 2 +/- 3 years; the others had no variation of their treatment. CONCLUSION: Exercise related ventricular tachycardia in children seems: 1) to have more severe prognosis if symptomatic or polymorphic; 2) mostly to arise from right ventricle; 3) to be successfully treated by antiarrhythmic drugs with beta-blocking activity.

Permanent overdrive atrial pacing in the chronic management of recurrent postoperative atrial reentrant tachycardia in patients with complex congenital heart disease.

This study investigated the value of permanent atrial pacing as an adjunct to the current therapy in the chronic management of recurrent postoperative atrial reentrant tachycardia in patients with complex congenital heart disease. We studied the postpacing clinical course in 18 patients with recurrent atrial reentrant tachycardias unresponsive to conventional therapy who had an implanted atrial pacemaker. The pacemaker was programmed at a lower pacing rate 20% faster than the spontaneous mean daily rate previously determined with 24-hour Holter monitoring. Serial Holter recordings and pacemaker programming sessions were subsequently performed trying to maintain a paced atrial rhythm overdriving the spontaneous rhythm as long as possible. Twenty-four hour Holter monitoring documented a prevalent (> 80%) paced rhythm during the daily hours in all patients during the follow-up; all patients, however, required at least once a variation in programmed mode and pacing rate. Antiarrhythmic medications were discontinued after 6 months if the patient remained arrhythmia free while on pacing. Recurrences of atrial reentrant tachycardia occurred in five patients (29%) during the initial 6 months interval after the pacemaker implantation, while late recurrences occurred in only two patients (11%). One patient died suddenly 10 months after the pacemaker implant. At the end of the follow-up, 15 patients (83%) were arrhythmia-free and only 2 of them were still on antiarrhythmic drugs. We conclude that permanent atrial overdrive pacing can be an important tool in the management of patients with atrial reentrant tachycardia following repair of congenital heart disease.

[Transcatheter radiofrequency ablation in supraventricular tachycardia in children: immediate results and mid-term follow-up]. / Ablazione transcatetere con radiofrequenza delle tachicardie sopraventricolari in età pediatrica: risultati immediati e di un follow-up a medio termine.

OBJECTIVES: The purpose of this study was to evaluate the efficacy and safety of radiofrequency ablation of supraventricular tachycardias due to a reentry circuit in a group of closely followed-up pediatric patients. PATIENTS: Forty-six pediatric patients (mean age 12.6 years, range 3-18) underwent a total of 48 radiofrequency ablation procedures for reciprocating supraventricular tachycardia. Thirty-nine had an orthodromic reentry tachycardia, 6 an atrioventricular node reentry tachycardia and 1 a permanent junctional reciprocating tachycardia. METHODS: To ablate the overt accessory pathways, the Kent potential (K) was identified and then the shortest A-K, and delta wave-K intervals were measured. The shortest V-A interval was identified for those concealed. For the left-sided accessory pathways, we used the retrograde transaortic approach in 10 procedures and the transseptal approach in 18. Atrioventricular node reentry tachycardia was ablated at the site where the slow-pathway electrogram was recorded. Follow-up clinical data, electrocardiogram, 24-hours Holter monitoring and transesophageal atrial stimulation were obtained and evaluated. RESULTS: Early: We performed a total of 48 procedures. Among 41 procedures performed in the 39 patients with accessory pathway, 38 were successful (92,6%). Mean fluoroscopy time was 31 +/- 18 min. For left sided accessory pathways, mean fluoroscopy time of procedures with retrograde approach was 45 +/- 10 min and with transseptal 23 +/- 12 min (p < 0.01). Ablation of slow-pathway in patients with intranodal reentry tachycardia was successful in 3/6 cases (50%). The patient with permanent junctional reciprocating tachycardia was successfully ablated. Late: All patients are alive and none was lost during the follow-up after a mean time of 12.9 months (range 5-33). Success at last follow-up was 100% in patients with an accessory pathway and 33% in patients with atrioventricular node reentry. In patient with permanent junctional reciprocating tachycardia, the arrhythmia appeared again one month after the procedure, thus a second successful attempt was performed. COMPLICATIONS: Major complications (6,5%) including a right femoral vein thrombosis (one patient), an hematoma without pulse loss (one patient) and a non-sustained monomorphic ventricular tachycardia (one patient). CONCLUSIONS: Our data show high efficacy of radiofrequency ablation in pediatric patients with accessory pathways. The risks are low at follow-up evaluation, but might be helpful a longer-term follow-up in order to evaluate the risk of a long fluoroscopy time and the arrhythmogenic effect of the scar.