A Dutch MYH7 founder mutation, p.(Asn1918Lys), is associated with early onset cardiomyopathy and congenital heart defects.

BACKGROUND: Mutations in the myosin heavy chain 7 (MYH7) gene commonly cause cardiomyopathy but are less frequently associated with congenital heart defects. METHODS: In this study, we describe a mutation in the MYH7 gene, c. 5754C > G; p. (Asn1918Lys), present in 15 probands and 65 family members. RESULTS: Of the 80 carriers (age range 0-88 years), 46 (57.5%) had cardiomyopathy (mainly dilated cardiomyopathy (DCM)) and seven (8.8%) had a congenital heart defect. Childhood onset of cardiomyopathy was present in almost 10% of carriers. However, in only a slight majority (53.7%) was the left ventricular ejection fraction reduced and almost no arrhythmias or conduction disorders were noted. Moreover, only one carrier required heart transplantation and nine (11.3%) an implantable cardioverter defibrillator. In addition, the standardised mortality ratio for MYH7 carriers was not significantly increased. Whole exome sequencing in several cases with paediatric onset of DCM and one with isolated congenital heart defects did not reveal additional known disease-causing variants. Haplotype analysis suggests that the MYH7 variant is a founder mutation, and is therefore the first Dutch founder mutation identified in the MYH7 gene. The mutation appears to have originated in the western region of the province of South Holland between 500 and 900 years ago. CONCLUSION: Clinically, the p. (Asn1918Lys) mutation is associated with congenital heart defects and/or cardiomyopathy at young age but with a relatively benign course.

Fetal cardiac output in monochorionic twins.

OBJECTIVES: To compare fetal cardiac output (CO) in donor and recipient twins of twin-twin transfusion syndrome (TTTS) pregnancies after laser therapy with that of monochorionic twins without TTTS and normal singletons. METHODS: In a longitudinal, prospective study, we sonographically assessed fetal CO in donors (n = 10) and recipients (n = 10) with TTTS after fetoscopic laser therapy, in monochorionic twins without TTTS (n = 20) and in normal singleton pregnancies (n = 20). The fetal CO of TTTS twins was determined 1 day and 1 week after laser treatment, and from then on every 2-4 weeks until birth. Twins without TTTS were examined biweekly until birth. Singletons were examined twice, with an 8-week interval, at different gestational ages between 17 and 35 weeks. RESULTS: Absolute CO increased exponentially with advancing gestational age (P < 0.0001), and was significantly related to fetal weight in all groups (P < 0.0001). The median CO/kg in donors after laser therapy, recipients after laser therapy and non-TTTS monochorionic twins was significantly higher than that in singletons (all P < 0.001). Median CO/kg in donors after laser therapy, recipients after laser therapy, and non-TTTS monochorionic twins was not significantly different between groups. CONCLUSIONS: Monochorionic twins with TTTS have higher CO after laser therapy than normal singletons.

[Percutaneous implantation of a pulmonary valve in 3 children with surgically corrected cardiac anomalies]. / Percutane implantatie van een pulmonalisklep bij 3 kinderen met chirurgisch gecorrigeerde hartafwijkingen.

An 11-year-old girl, a 15-year-old boy and a 12-year-old girl all underwent percutaneous implantation of a Melody pulmonary valve prosthesis to replace a stenotic and insufficient homograft in the pulmonary artery. Preoperatively, 2 of the children suffered from fatigue and dyspnoea on exertion The homografts had been implanted between the ages of 1-2, to establish surgical continuity between the right ventricle and the pulmonary artery. The anomalies were tetralogy of Fallot, pulmonary atresia with intact ventricular septum and pulmonary atresia with a ventricular septum defect. Percutaneous pulmonary valve replacement was successful in all 3 patients. After implantation, right ventricular pressure decreased to 30% of systemic pressure and regurgitation was not observed. All patients were discharged in a good condition on the day after the implantation. Percutaneous pulmonary valve replacement is a promising technique with good short-term results. In selected patients this percutaneous technique can substitute or postpone the surgical replacement ofa stenotic or insufficient homograft.

Coronary artery stenosis after radiofrequency catheter ablation of accessory atrioventricular pathways in children with Ebstein's malformation.

BACKGROUND: Complications concerning the coronary arteries that are directly related to radiofrequency catheter ablation procedures have not been reported in children. Coronary artery lesions, however, have been demonstrated after the endocardial application of radiofrequency current in young animals. METHODS AND RESULTS: Two boys with Ebstein's anomaly of the tricuspid valve developed clinically asymptomatic coronary artery stenosis after radiofrequency catheter ablation of right-sided accessory atrioventricular pathways with standard catheter technology. CONCLUSIONS: The complication of coronary artery stenosis demonstrates a substantial risk after right atrial free wall radiofrequency current application in children. The risk of late coronary alterations should be considered when the use of catheter ablation procedures to young patients is proposed.

[Radiofrequency catheter ablation for treating children with cardiac arrhythmias: favourable results after a mean of 4 years]. / Katheterablatie met radiofrequente energie ter behandeling van kinderen met hartritmestoornissen: gunstige resultaten na gemiddeld 4 jaar.

OBJECTIVE: Analysis of long-term results with radiofrequency catheter ablation (RF ablation) in children. DESIGN: Retrospective. METHOD: Data were analysed from all 118 paediatric patients < or =18 years old who underwent RF ablation at the Leiden University Medical Centre (LUMC), the Netherlands, during the period 1 December 1992-31 May 2004. RESULTS: The group consisted of 6o boys and 58 girls with a mean age of 12.7 years (SD: 4.6). They underwent 140 RF ablation procedures for 122 disorders. Indications for RF ablation were: failure or side-effects of antiarrhythmic medication (45%), patient/parent choice (45%), cardiomyopathy or life-threatening arrhythmia (8%), and impending surgery for a congenital heart defect (2%). The mean follow-up interval was 4 years (SD: 3.2; range: 1.2 months-11.3 years). The final total success rate for RF was 93% (n = 110). 19 patients (16%) underwent a total of 22 repeat procedures. Recurrences occurred after a mean period of 2.3 months (SD: 2.5) following successful RF ablation. Major complications (2nd degree AV block) occurred in 2 patients. During follow-up, no evidence was found of new arrhythmias or of coronary artery lesion development as the result ofRF ablation. There was no difference between the < 10 years of age group and the > or = 10 years of age group in terms of final success rate (93% vs. 93%; p = 0.914) and complication rate (3% vs. 7%, p = 0.680). CONCLUSION: The long-term outcome of paediatric patients who underwent RF ablation was good. RF ablation in young children (< 10 years) was found to be safe and effective. These results demonstrate that it is also possible to curatively treat this group of patients with RF ablation in specialized centres.

Common arterial trunk, uncommon coronary arterial anatomy.

Macroscopic investigation was done in 44 postmortem specimens of hearts with common arterial trunk. In 38 hearts, the normal distribution in left and right coronary arteries was found. Of the coronary orifices, five were pinpoint and three showed a double orifice. The left coronary orifice was positioned in the posterior part of the truncus (p < 0.0001); the right coronary orifice was positioned in the right anterior and lateral part (p < 0.0001). In 19 hearts, coronary orifices were found above sinus level, left coronary orifices more often than right coronary orifices (p < 0.001). In seven hearts, type I truncus was found, in seven type II truncus was found, in 17 the truncus was intermediate between types I and II, in two type III truncus was found. In 11 hearts, the pulmonary artery distribution could no longer be identified. The truncal valve was bicuspid in 11 hearts, tricuspid in 25 hearts, and quadricuspid in eight hearts. The truncal valve showed overriding of 5% to 100%. Malformations of the coronary arteries were found in 28 hearts (64%). In 27 hearts (61%), the coronary arterial anatomy might have had clinical consequences. In nine hearts, coronary arterial orifices were at risk in excision of the pulmonary arteries from the common arterial trunk. The role of the neural crest as an etiologic factor of coronary arterial malformations in common arterial trunk should be taken into account.

Supraventricular tachycardia in infants, children and adolescents: diagnosis, and pharmacological and interventional therapy.

Supraventricular tachycardia is the most frequent form of symptomatic tachydysrhythmia in children. Neonates and infants with paroxysmal supraventricular tachycardias generally present with signs of acute congestive heart failure. In school-aged children and adolescents, palpitations are the leading symptom. Chronic-permanent tachycardia results in a secondary form of dilated cardiomyopathy. Therapy for episodes of tachycardia depends on the individual situation. In severe haemodynamic compromise, or if ventricular tachycardia is suspected, tachycardia should immediately be terminated by external cardioversion during deep sedation. Vagal manoeuvres are effective in patients with atrioventricular reentrant tachycardias. Adenosine is the drug of first choice in any age group for tachycardias involving the atrioventricular node; its advantages include short half-life and minimal or absent negative inotropic effects. Adenosine may also be used in patients with wide QRS complex tachycardia. Intravenous verapamil is contraindicated in neonates and infants because of the high risk of electromechanical dissociation. In older children (>5 years) and adolescents, verapamil may be administered with the same restrictions as in adult patients (wide QRS complex tachycardia, significant haemodynamic compromise). Spontaneous cessation of tachycardia can be expected in most neonates and infants during the first year of life. Prophylactic pharmacological treatment in this age group is advisable because recognition of tachycardia is often delayed until the occurrence of symptoms. Withdrawal of drug treatment should be attempted around the end of the first year. However, in older children, spontaneous cessation of tachycardia is rare. Prophylactic drug therapy is performed on an empirical basis. Digoxin may be administered in all forms of supraventricular tachycardia in which the atrioventricular node is involved, except in patients with pre-excitation syndrome aged >1 year. In patients with atrioventricular reentrant tachycardia, class IC drugs such as flecainide and propafenone are effective. Sotalol is also effective in atrioventricular reentrant tachycardia, as well as in primary atrial tachycardia. Although amiodarone has the highest antiarrhythmic potential, it should be used with caution because of its high rate of adverse effects. In school-aged children and adolescents, radiofrequency catheter ablation of the anatomical substrate is an attractive alternative to drug therapy, with a rate of permanent cessation of the tachycardia of up to 90%. Despite the clear advantages of this procedure, it should be performed only with unquestionable indication; the long term morphological and electrophysiological sequelae on the growing atrial and ventricular myocardium are still unknown.

Alpha-motoneuron excitability at high altitude.

It has been hypothesized that chronic hypobaric hypoxia could lead to inhibition of the alpha-motoneuron pool, thus limiting the maximal activation of working skeletal muscles. To test this hypothesis six subjects [32 (SEM 2) years] were evaluated in resting conditions, at sea level and after acclimatization at 5,050 m. The recruitment curves of the Hofmann-reflex (H-) and the direct muscle-response. (M-) of the right soleus muscle were obtained by stimulating the posterior tibial nerve with different intensities while recording the electromyogram of the soleus muscle. From the recorded data the net alpha-motoneuron excitability (ratio of maximal H-reflex to M-response Hmax:Mmax ratio), the threshold and gain for both responses, obtained from linear regressions through the rising phase of the recruitment curves of both responses, as well as the latency times of both responses were determined. The latency times and the Hmax:Mmax ratio were unchanged at altitude. The thresholds of both responses and the gain of the M-response were unaltered. The gain of the H-response was significantly higher at altitude when compared to sea level.(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary artery involvement early and late after radiofrequency current application in young pigs.

Radiofrequency current (500 kHz) was delivered by temperature guidance (75 degrees C) over a 30-second period in 10 young piglets with a steerable 6F electrode catheter equipped with a thermistor at the 4 mm tip electrode. Lesions were created at the right atrial aspect of the tricuspid valve anulus, at the left ventricular myocardium under the lateral mitral valve anulus, and at the left ventricular apex. After 48 hours, five animals were randomly sacrificed. Lesions in the five animals appeared as transmural gray-white coagulation necrosis. Lymphocytic infiltration around the right atrial lesions extended into the layers of the right coronary artery in four of five animals. After 6 months, lesions consisted of compact fibrous tissue in the remaining five animals. Right atrial lesions extended to the layers of the right coronary artery in four of five pigs. In two animals the lumen of the right coronary artery was narrowed because of intimal thickening by 25% and 40%, respectively. No increase in the lesion size was observed with the growth of the animals. Effects on the right coronary artery as a late sequela after radiofrequency current application may also be possible in human beings and should be considered when radiofrequency current ablation procedures are proposed in infants and young children.

Stepwise interventional approach in a neonate with pulmonary valve atresia and intact ventricular septum.

UNLABELLED: In neonates with pulmonary atresia and intact ventricular septum the aims of therapy are maintenance of pulmonary blood flow and right ventricular decompression in order to achieve right ventricular support of the pulmonary circulation. Recent developments in interventional heart catheterization with pulmonary radiofrequency-assisted balloon valvuloplasty and ductal stent implantation offer an alternative to the classical surgical approach. We report on a neonate with membranous pulmonary atresia and intact ventricular septum, in whom a large interatrial right-to-left shunt via the foramen ovale persisted after radiofrequency-assisted pulmonary balloon valvuloplasty on the 2nd day of life. The interatrial shunt prevented adequate right ventricular filling and antegrade pulmonary perfusion leading to severe cyanosis (transcutaneous oxygen saturation 40%). In order to increase pulmonary blood flow and raise left atrial pressure, the arterial duct was stented. After ductal stenting, prostaglandin was discontinued and the transcutaneous oxygen saturation remained stable around 89%. At follow up after 7 weeks the foramen ovale had decreased in size and only a small left-to-right shunt was present, documenting the effectiveness of this approach. CONCLUSION: Based on the present case we propose a stepwise interventional approach for the neonate with pulmonary atresia and intact ventricular septum. If cyanosis persists after isolated pulmonary valvuloplasty despite adequate right ventricular function, ductal stent implantation can reduce interatrial shunting and thus improve oxygen saturation.

Incidence and time course of intimal plaque formation in the right coronary artery after radiofrequency current application detected by intracoronary ultrasound.

BACKGROUND: Despite the current clinical use of radiofrequency (RF) catheter ablation in infants and children, the late effects of RF current application at immature myocardium remain unclear. The purpose of this study was to investigate incidence and time course of coronary lesions after RF current application at developing myocardium in an animal model. RESULTS: In 10 pigs, 6 weeks of age (13+/-2 kg), RF current (500 kHz) was delivered by temperature guidance (75 degrees C) using a steerable electrode catheter (4 mm tip electrode) over 30-second periods. RF lesions were created at the lateral right atrial wall at the tricuspid valve annulus and the lateral left atrial and ventricular wall at the mitral valve annulus. Subsequent coronary angiography and intracoronary ultrasound (ICUS) of the right coronary artery (RCA) and the left circumflex artery (CX) were performed 3, 6, 9 and 12 months after RF current application. Quantitative coronary angiography did not exhibit any significant stenosis of the vessels during the study period. Intimal lesions of the RCA were documented for the first time at the 6-month study in 3 animals by ICUS (mean plaque area 2.2+/-0.2 mm(2), mean area stenosis 30.4+/-4.0%). There was no significant change in lesion length, area stenosis and plaque area at the 9- and 12-month studies. All 3 coronary artery lesions were confirmed in close proximity to myocardial RF lesions by histological examination 12 months after RF delivery. No intimal plaque formation of the CX was observed. CONCLUSIONS: Affection of the RCA as a late sequel after RF current application at the lateral right atrial wall occurred in 3 out of 8 long-term surviving pigs. Three to six months seem to be the time frame for the development of intimal lesions after RF delivery. In this experimental setting, angiography failed to detect these intimal changes. The potential risk of coronary affection may be important for catheter ablation procedures at the right atrial myocardium in infants and small children.

Radiofrequency current application on immature porcine atrial myocardium: no evidence of areas of slow conduction after 12-month follow-up.

INTRODUCTION: Radiofrequency current (RFC) application is a widely used procedure for treatment of supraventricular arrhythmias. The purpose of this study was to investigate late electrophysiologic sequelae of RFC lesions at immature atrial myocardium in pigs, as they have not yet been systematically investigated in vitro. METHODS AND RESULTS: RFC application (temperature guided) was performed in seven piglets (mean age 6 weeks) by a steerable 6-French electrode catheter positioned at the lateral aspect of the tricuspid valve annulus. After 12 months, hearts were removed, and lesions with surrounding tissue were isolated. The viable tissue at the border of the specimen was paced with a cycle length of 500 and 600 msec. One hundred fifty impalements were performed on each specimen using capillary microelectrodes to record action potential characteristics from the lesion's surface and the surrounding tissue. In all seven specimens, no transmembrane action potentials from the fibrotic surface of each of the lesions could be recorded. The surrounding viable tissue was sharply demarcated electrically. No areas of slow conduction were detected. Action potential characteristics as mean maximum diastolic transmembrane potential, mean action potential duration at 90% repolarization, and upstroke velocity of phase 0 of the action potential were all normal. CONCLUSION: No evidence of areas of slow conduction 12 months after RFC application at immature atrial myocardium suggests that this technique is safe regarding occurrence of late atrial tachyarrhythmias after the procedure.

[High frequency catheter ablation in young patients with permanent junctional reentry tachycardia and ectopic atrial tachycardia]. / Hochfrequenzstrom-Katheterablation bei jungen Patienten mit permanenter junktionaler Reentry-Tachykardie und atrialer ektoper Tachykardie.

Ten young patients with a median age of 10.5 (range: 6 to 31) years suffering from the permanent form of junctional reciprocating tachycardia (PJRT; n = 7) and ectopic atrial tachycardia (AET; n = 3) were treated by transcatheter radiofrequency current application. Indications for interventional therapy were failure of medical therapy after a median of 3 antiarrhythmic drugs in all patients, syncope in 1, and impaired left ventricular function in 4 patients (PJRT n = 3, AET n = 1). The intervention was primarily successful in all patients. Median fluoroscopy time during the ablation procedure was 17 (10 to 70) minutes. A median of 3 (1 to 14) radiofrequency (500 kHz) pulses was delivered at a target temperature of 70 degrees C or with 30 W for 30 s. One patient had a recurrence of PJRT and was successfully treated by a repeat ablation. After a median follow-up of 14 (2 to 61) months, all patients are free of drug treatment and in normal sinus rhythm. Left ventricular function has normalized in patients with follow-up > 6 months. Radiofrequency catheter ablation was a safe and effective therapy in young patients with drug-resistant forms of chronic-permanent supraventricular tachycardia.

Development of the cardiac coronary vascular endothelium, studied with antiendothelial antibodies, in chicken-quail chimeras.

The endothelium of the coronary vascular system has been described in the literature as originating from different sources, varying from aortic endothelium for the main coronary stems, endocardium for the intramyocardial network, and sinus venosus lining for the venous part of the coronary system. Using an antibody against quail endothelial cells (alpha-MB1), we investigated the development of the coronary vascular system in the quail (Hamburger and Hamilton stages 15 to 35) and in a series of 36 quail-chicken chimeras. In the chimeras, pieces of quail epicardial primordium and/or liver tissue were transplanted into the pericardial cavity of a chicken host. The results showed that the coronary vascular endothelial distribution closely followed the formation of the epicardial covering of the heart. However, pure epicardial primordium transplants did not lead to endothelial cell formation, whereas a liver graft with or without an epicardial contribution did have this capacity. The first endothelial cells were seen to reach the heart at the sinus venosus region, subsequently spreading through the inner curvature to the atrioventricular sulcus and the outflow tract and, last of all, over the ventricular surfaces. At these sites, the precursor cells and small vessels were seen to invade the sinus venosus wall, the ventricular and atrial myocardium, and the mesenchymal border of the aortic orifice. Connections with the endocardium of the heart tube were only observed in the right ventricular outflow region. Initially, the connections with the aortic endothelium were multiple, but later in development only two of these connections persisted to form the proximal part of the two main coronary arteries. Connections to the pulmonary orifice were never observed. Our transplantation data showed that the entire coronary endothelial vasculature originated from an extracardiac source. Moreover, using the developing subepicardial layer as a matrix, we showed that the endothelial cells reached the heart from the liver region. Ingrowth into the various cardiac segments was also observed. Implications for the relation to specific congenital cardiac malformations are discussed.

[Arrhythmogenic right ventricular dysplasia/cardiomyopathy - diagnosis in childhood]. / Arrhythmogene rechtsventrikuläre Dysplasie/Cardiomyopathie. Diagnostik im Kindesalter.

Arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) is a rare, but important cause for sudden death in adolescents and young adults. Part of the patients affected show the pattern of autosomal-dominant inheritance. Two pediatric patients with ARVD/C are presented who may reflect the spectrum of clinical presentation of ARVD/C in childhood resulting in difficulties or even delay to establish the correct diagnosis. One patient with a sporadic form of ARVD/C presented with a syncope and spontaneous as well as inducible ventricular tachycardia. On the ECG, an epsilon wave could be identified. An automatic cardioverter defibrillator was implanted. The second patient had a familiar form of ARVD/C with no symptoms. There was a history of frequent sudden deaths in this family. Biopsies of the right ventricular myocardium showed fibrosis with deposition of fatty tissue. There was clear evidence of ARVD/C in the necropsy of the patient's aunt. Therapy with propanolol was started in this patient.

Lack of evidence of areas of slow conduction early after radiofrequency current application at porcine atrial myocardium.

Electrophysiological sequelae after creation of atrial myocardial lesions by radiofrequency current (RFC) application have not been studied in vitro. During general anesthesia, a steerable 6 French electrode catheter, equipped with a thermistor at the 4-mm tip electrode, was positioned at the lateral atrial aspect of the tricuspid valve annulus in 5 piglets (German Landrace, mean body weight 12.5 kg). Temperature-guided (75 degrees C) RFC (500 kHz) was delivered over 30 seconds. Forty-eight hours later, the hearts were removed and placed in ice-cold Turner's solution. The right atria were dissected, and the RFC lesions with surrounding tissue were cut out and transferred to an organ bath according to Steiert. Preparations were superfused with Turner's solution at 37 degrees C. Pacing of the viable tissue at the border of the preparations was accomplished at a cycle length of 500 ms. Whole atrial preparations were impaled (76 to 150 impalements per specimen) with KCl capillary microelectrodes containing 3 MKCl. In the surrounding viable tissue of the five preparations, mean maximum diastolic transmembrane potential ranged from -61.3 to -63.7 mV, mean action potential duration at 90% repolarization ranged from 135.2 to 156.1 ms, and mean maximum upstroke velocity of phase 0 of the action potential was between 104.7 and 112.9 V/sec. Statistical analysis revealed no significant differences among all 3 variables. No intracellular action potential was recorded from the surface of all 5 lesions. The surrounding tissue was sharply demarcated, with unaltered transmembrane action potential characteristics in the vicinity of the lesions. Areas of slow conduction were not observed. Lack of evidence of areas of slow conduction after RFC application to the atrial myocardium may imply that this technique is safe regarding occurrence of atrial tachyarrhythmias.

Effects of intracardiac radiofrequency current application on coronary artery vessels in young pigs.

INTRODUCTION: Radiofrequency current is widely used in children to ablate accessory AV pathways. Previous data in a pig model demonstrated coronary artery obstruction adjacent to radiofrequency current lesions 48 hours and 6 months after energy delivery. In the present study, the long-term effects (>6 months) of radiofrequency current application on coronary artery vessels in young pigs are assessed. METHODS AND RESULTS: Radiofrequency current (500 kHz) was delivered over 30 seconds in ten piglets (mean body weight 12.8 kg) using a steerable 6-French catheter with a 4-mm thermistor tip electrode (target temperature 75 degrees C). Lesions were created under fluoroscopic and electrocardiographic guidance at the lateral right atrial (RA) wall above the tricuspid valve orifice, and at the lateral left atrial and left ventricular wall adjacent to the mitral valve orifice. Selective coronary angiography and intravascular ultrasound (IVUS) studies were performed 3, 6, 9, and 12 months after energy application. After 12 months, the lesions were studied pathohistologically. All lesions consisted of compact fibrous tissue. RA lesions extended to the adjacent right coronary artery and led to coronary artery involvement with increased fibrous tissue in the adventitia and media and intimal thickening in three animals. Coronary arterial narrowing was documented by IVUS during follow-up in all three cases 9 months after energy application. Angiography failed to demonstrate coronary pathology in any of the three animals. CONCLUSION: The risk of late coronary artery lesions must be considered when catheter ablation at the RA wall is planned in children with free-wall accessory AV pathways.

Abbreviated combined anatomical/electrophysiological approach for catheter ablation of atrioventricular nodal reentrant tachycardia in children.

Atrioventricular nodal reentrant tachycardia was proven during electrophysiologic study in 41 children, aged from 3.7 to 16 years, who were referred for catheter ablation of symptomatic supraventricular tachycardia. Using an abbreviated combined anatomical and electrogram-guided approach for selective ablation of the slow pathway, a steerable ablation catheter was placed at the inferior region of the vestibule of the tricuspid valve close to the orifice of the coronary sinus, with the intention of recording a multicomponent local atrial electrogramm during sinus rhythm. If application of radiofrequency current of 500 kHz at 70 degrees C at this site did not result in a slowly accelerated junctional rhythm, at a rate of less than 120 beats per minute, the catheter was stepwise advanced up to a position midway towards the apex of the triangle of Koch for additional applications of energy. Ablation was achieved in 35 of the patients. In 6 patients, the slow pathway was modulated such that the tachycardia could no longer be induced. The number of applications of energy ranged from 1 to 19, with a median of 6 applications. The mean period of fluoroscopy was reduced to 15.6 (4.3 to 39.8) minutes, while the overall duration of the catheterization procedures ranged from 88 to 280 (mean 173.2) minutes. In none of the patients did we observe permanent high grade atrioventricular block. During follow-up over a mean of 4.1 years, two patients had recurrence of tachycardia, corresponding to a 95% rate of success in the midterm. We conclude that selective radiofrequency ablation of the slow pathway using the abbreviated anatomical and electrophysiological approach is a safe and curative therapeutic approach in children with atrioventricular nodal reentrant tachycardia. Periods required for fluoroscopy can be significantly reduced, and mid-term results are excellent.

[Atrioventricular nodal reentry tachycardia in children: curative treatment by high frequency catheter ablation]. / AV-Knoten-Reentry-Tachykardien im Kindesalter: Kurative Behandlung durch Hochfrequenzstromablation.

BACKGROUND: Atrioventricular nodal reentrant tachycardia (AVNRT) is one of the most common forms of supraventricular tachycardia in the pediatric population. PATIENTS AND METHODS: 41 children with a mean age of 9.6 (3.7-16) years with recurrent atrioventricular nodal reentrant tachycardia (AVNRT) refractory to medical treatment (n = 38) and recurrent syncope (n = 3) underwent electrophysiologic (EP) study. In all patients dual AV-nodal physiology could be demonstrated during EP study and typical form of AVNRT (mean heart rate 220/min) could be induced by programmed atrial stimulation. A steerable 7 F ablation catheter was placed at the inferoparaseptal region of the tricuspid valve annulus close to the orifice of the coronary sinus with the intention to record a late fractionated local atrial electrogram during sinus rhythm. Starting at this point radiofrequency current (500 kHz) with a target temperature of 70 degrees C was delivered with the intention to ablate the slow pathway. If a slowly accelerated junctional rhythm (< 120/min) occurred during energy discharge, programmed atrial stimulation was repeated. Otherwise radiofrequency current was delivered step by step up to a septal position next to the tricuspid valve annulus. Slow pathway ablation was defined as lack of evidence of dual AV nodal pathways during repeated atrial stimulation. Slow pathway modulation was defined as maximal one atrial echoimpulse after ablation. RESULTS: The number of energy applications ranged from 1-19 (median 6). In 35/41 patients slow pathway ablation could be achieved; in six patients the slow pathway was modulated. In none of the patients permanent high grade AV block was observed. During follow-up (mean 4.1 years) two patients had a recurrent episode of AVNRT after slow pathway modulation. All other patients are still free of AVNRT without medical treatment. CONCLUSION: Selective radiofrequency current ablation/modulation of the slow pathway is a safe and curative treatment of AVNRT in young patients.