Long-term efficacy and safety of atenolol for supraventricular tachycardia in children

Propranolol, a first-generation nonselective β-adrenoceptor blocking agent, is commonly used to treat pediatric arrhythmias. Atenolol, relatively longacting, cardioselective β-adrenoceptor blocking agent, has been successfully used in adults with supraventricular tachycardia (SVT). There is only one report on the use of atenolol in children with SVT, and our report is on the first long-term prospective study to evaluate the use of atenolol in children. A group of 22 children <18 years of age with clinical SVT were enrolled in the study. The tachycardia was documented on electrocardiograms in each case and was confirmed by electrophysiologic studies in some. Once-a-day oral atenolol was started as a monotherapy. Of the 22 children with various types of SVT, 13 (59%) were well controlled on long-term oral atenolol therapy. The effective dose of atenolol ranged between 0.3 and 1.3 mg/kg/day (median effective dose 0.7 mg/kg/day). Five children had some adverse effects. However, none in the successful group of 13 patients required drug discontinuation because of such effects. Once-a-day oral atenolol as a monotherapy is effective and relatively safe for long-term management of SVT during childhood. It is an attractive alternative β-adrenoceptor blocking agent for the management of pediatric arrhythmias.     

New antiarrhythmic drugs in pediatric use: Propafenone

Summary Propafenone hydrochloride, a class IC antiarrhythmic agent, combines sodium channel-blocking effects with -blocking capacities and a weak calcium antagonism. The drug exerts marked electrophysiologic effects on accessory atrioventricular pathways. In patients with atrioventricular nodal reentry tachycardia, propafenone is able to block conduction in the fast conducting pathway. In addition, propafenone is very effective in young patients with supraventricular tachycardia based on enhanced abnormal automaticity. In pediatric patients, left ventricular performance remains unimpaired. Proarrhythmic events have been noted in children only occasionally. In accordance with the electrophysiologic profile, intravenous and oral propafenone is an effective agent for treatment of supraventricular tachycardia based on a reentry mechanism and due to abnormal automaticity (i.e., supraventricular tachycardia based on an accessory atrioventricular pathway, atrioventricular nodal reentry tachycardia, junctional ectopic tachycardia, and atrial ectopic tachycardia). In children with ventricular dysrhythmias, efficacy seems to be related to the underlying cardiac diagnosis. Propafenone is well tolerated in the majority of young patients. Incidence of proarrhythmic events seems to be lower with propafenone than with other class 1C agents. However, the risk of these serious adverse events should be taken into account when therapy with propafenone is considered, particularly in patients with structural heart disease.     

Re-entrant supraventricular tachycardia in infancy: current role of prophylactic digoxin treatment

Re-entrant supraventricular tachycardia is the most common cardiac arrhythmia in infancy. Pharmacological prevention of recurrencies is a standard recommendation for infants less than 1 year of age. In view of the often benign spontaneous clinical course of the disease, the risk-benefit analysis of any antiarrhythmic agent given is important. It was the aim of this retrospective study, to assess the value of oral long-term digoxin given to paediatric patients with supraventricular tachycardia with onset in the first 4 months of life. Twenty-six newborns and infants fulfilled the inclusion criteria. Median age at first presentation of the patients was 7 days. Eight patients (31%) had structural heart disease, 9 patients had a pre-excitation syndrome, and the other 17 children had a concealed accessory atrioventricular pathway. Long-term prophylaxis with oral digoxin was considered successful in 17 children (65%). In 2 patients therapy with digoxin was considered partially effective and in 7 patients (27%) failure of digoxin to improve symptoms led to the introduction of other anti-arrhythmic agents. Serum digoxin levels were no different in the patients with successful therapy as compared to those with treatment failure. No side-effects due to digoxin were noted in all the patients treated. After a mean followup of 54 months (12–130 months), 19 children (73%) were free of recurrencies and on no medication, 5 children were free of recurrencies but had anti-arrhythmic therapy. Only 2 patients, both on anti-arrhythmic therapy, were still suffering from tachycardia. Conclusion Digoxin remains an effective treatment option in infants with supraventricular tachycardia and it helped to avoid the long-term use of other anti-arrhythmic drugs with potentially more serious side-effects (pro-arrhythmia) in a considerable proportion of infants treated. Received: 29 April 1997 / Accepted in revised form: 31 July 1997     

A Multicenter, Long-Term Study on Arrhythmias in Children with Ebstein Anomaly

To assess the prevalence, history, and treatment of arrhythmias, in particular preexcitation and Wolff–Parkinson–White (WPW) syndrome, in patients with Ebstein anomaly (EA) during childhood and adolescence, we performed a multicenter retrospective study of all consecutive live-born patients with EA, diagnosed, and followed by pediatric cardiologists between 1980 and 2005 in The Netherlands. During a follow-up after EA diagnosis of 13 years 3 months (range: 6 days to 28 years 2 months), 16 (17%) of the 93 pediatric EA patients exhibited rhythm disturbances. Nine patients showed arrhythmic events starting as of the neonatal period. Supraventricular tachycardia was noted in 11 patients. One patient died in the neonatal period due to intractable supraventricular tachycardia resulting in heart failure and one patient died at 5 weeks of age most probably due to an arrhythmic event. The 14 surviving patients all show preexcitation, albeit 4 of them intermittently, and all have a right-sided accessory pathway location. Nine patients underwent catheter ablation of an accessory pathway. Only four patients are currently on antiarrhythmic drugs. The 17% prevalence of rhythm disturbances in pediatric EA patients, most commonly supraventricular arrhythmias, is significantly lower than in adult EA patients. Life-threatening rhythm disturbances are not frequent early in life. Symptomatic patients are well treated with radiofrequency catheter ablation.     

Treatment of refractory supraventricular arrhythmias with flecainide acetate.

We treated 13 children aged 0.2 years to 15.7 years (median 7.1 years) with flecainide acetate for refractory symptomatic supraventricular tachycardia. Six children had direct atrioventricular accessory pathways, of whom four had overt Wolff-Parkinson-White syndrome on the 12 lead electrocardiogram, while in the other two the accessory pathway was concealed. Three children had nodal atrioventricular re-entrant tachycardia, two had a re-entrant tachycardia, the exact mechanism of which was not known, one child had ectopic atrial tachycardia, and one had atrial flutter associated with an atrial septal defect. The remaining 12 children had structurally normal hearts. Flecainide (2 mg/kg intravenously) resulted in termination of the tachycardia in 11 of the 12 children treated during tachycardia. In 11 of the children successful prophylaxis was achieved with oral flecainide. Side effects occurred in two children during intravenous administration, but there were no side effects with oral treatment. This experience indicates that flecainide, which has not been used extensively in children, is an effective and safe antiarrhythmic agent, capable of terminating and controlling supraventricular tachycardia in children. Furthermore, flecainide may be successful where conventional agents fail.     

Efficacy and safety of intravenous amiodarone for short-term treatment of paroxysmal supraventricular tachycardia in children

The use of intravenous amiodarone was assessed during 23 episodes of paroxysmal supraventricular tachycardia in 15 children aged 9 days to 11 years. Five of the fifteen patients had congenital structural heart disease, and three had Wolf-Parkinson-White syndrome. Tachyarrhythmias were returned to sinus rhythm during 20 of the 23 episodes (87%). No major adverse effects occurred. Recurrence of tachycardia was not observed during short-term follow-up. In conclusion, intravenous amiodarone is an effective, safe antiarrhythmic drug for short-term treatment of supraventricular tachycardia in children.     

Impact of Transesophageal Electrophysiologic Study to Elucidate the Mechanism of Arrhythmia on Children With Supraventricular Tachycardia and No Preexcitation

An electrophysiologic study (EPS) of children and teenagers with paroxysmal supraventricular tachycardia (SVT) and normal electrocardiography (ECG) in sinus rhythm was evaluated. Generally, EPS is performed only before paroxysmal SVT ablation in these patients. In this study, 140 patients (mean age, 15 ± 3 years) with normal ECG in sinus rhythm were studied for SVT by a transesophageal route in baseline state and after isoproterenol. Idiopathic left or right ventricular tachycardia was diagnosed in four patients (3 %). Anterograde conduction over an atrioventricular (AV) left lateral (n = 10) or septal (n = 9) accessory pathway (AP) was noted in 19 patients (13.5 %) at atrial pacing. Orthodromic AV reentrant tachycardia (AVRT) was induced in these children. Five of the patients had a high rate conducted over AP (>240 bpm in baseline state or >290 bpm after isoproterenol). Two of the patients (a 10-year-old girl with well-tolerated SVT and a 17-year-old with syncope-related SVT) had the criteria for a malignant form with the induction of atrial fibrillation conducted over AP at a rate exceeding 290 bpm in baseline state. Of the 140 patients, 74 (53 %) had typical AV node reentrant tachycardia (AVNRT), nine had atypical AVNRT (6 %), 1 had atrial tachycardia (0.7 %), and 33 (23.5 %) had AVRT related to a concealed AP with only retrograde conduction. Electrophysiologic study is recommended for children with paroxysmal SVT and normal ECG in sinus rhythm. The data are helpful for guiding the treatment. Ventricular tachycardia or atrial tachycardia can be misdiagnosed. Masked preexcitation syndrome with anterograde conduction through AP was present in 13.5 % of the patients, and 1.4 % had a malignant preexcitation syndrome.     

Tachykarde Herzrhythmusstörungen im Kindes- und Jugendalter

Paroxysmal supraventricular tachycardia (SVT) is the most common type of tachyarrhythmia occurring with an incidence of 0.1–0.4%. The occurrence of ventricular tachycardia is significantly lower in children and adults. The most frequent types of SVT in children are atrioventricular reentry tachycardia (AVRT) mediated by an accessory pathway and AV-nodal reentry tachycardia (AVNRT) using fibres with different conduction capacities (dual physiology of the AV-node). Both types can be successfully terminated with adenosine which selectively blocks conduction through the AV-node. Long-term pharmacological therapy represents one therapeutic option for recurrent episodes of SVT but it is increasingly being replaced by radiofrequency catheter ablation, which represents a curative treatment of SVT with success rates between 86% and 97%, especially when applied in children older than 5 years. Thus, long-term management of children with tachyarrhythmias should include early contact with pediatric electrophysiological centres.     

The treatment of arrhythmias in infants and children using propafenone

Antiarrhythmic treatment was required in 35 patients aged one day to 11 8/12 years (average 5 7/12 years) for one or several of the following arrhythmias: paroxysmal supraventricular tachycardia (17), ventricular extrasystole (16), ventricular tachycardia (17), ventricular extrasystole (16), ventricular tachycardia (4), junctional tachycardia (4), and atrial flutter (3). 300 mg/m2/day oral propafenone was administered in 3 to 4 divided doses. The arrhythmia in 21 of the 35 patients had been unsuccessfully treated by digoxin (6), verapamil (5), ajmalin (4), propranolol (3), spartein (1), phenytoin (1), and lidocain (1) prior to the propafenone therapy. However, the arrhythmias could be abolished or reduced in 30 patients (85.7%) by Propafenone. In 5 patients with supraventricular tachycardia (2), junctional tachycardia (2), or ventricular extrasystole (1), propafenone therapy had no effect. In two other patients propafenone led to atrioventricular conduction disturbances and had to be discontinued. Propafenone is an effective well tolerated antiarrhythmic drug without major side effects in pediatric patients.     

Use of a Cardioselective Beta-Blocker for Pediatric Patients With Prolonged QT Syndrome

The data on the efficacy of atenolol for long-QT syndrome (LQTS) are controversial. This study aimed to evaluate the efficacy of atenolol for pediatric patients with LQTS. A retrospective observational study investigating all patients who had LQTS treated with atenolol at two institutions was performed. The study identified 57 patients (23 boys and 34 girls) with a mean QT corrected for heart rate (QTc) of 521 ± 54 ms. The mean age of these patients at diagnosis was 9 ± 6 years. Their clinical manifestations included no symptoms (n = 33, 58%), ventricular tachycardia (n = 10, 18%), syncope (n = 6, 10%), resuscitated sudden cardiac death (n = 4, 7%), atrioventricular block (n = 2, 4%), and bradycardia or presyncope (n = 2, 3%). Of the 57 patients, 13 (22%) had a family history of sudden death. The follow-up period was 5.4 ± 4.5 years. Atenolol at a mean dose of 1.4 ± 0.5 mg/kg/day was administered twice a day for all the patients. The mean maximum heart rate was 132 ± 27 bpm on Holter monitors and 155 ± 16 bpm on exercise treadmill tests, with medication doses titrated up to achieve a maximum heart rate lower than 150 bpm on both tests. During the follow-up period, one patient died (noncompliant with atenolol at the time of death), and the remaining patients had no sudden cardiac death events. Four patients (8%) had recurrent ventricular arrhythmias, three of whom received an implantable cardioverter defibrillator (all symptomatic at the time of diagnosis). For three patients (6%), it was necessary to rotate to a different beta-blocker because of side effects or inadequate heart rate control. Atenolol administered twice daily constitutes a valid and effective alternative for the treatment of pediatric patients with LQTS.     

Treatment with flecainide for symptomatic and refractory tachyarrhythmias in children

Nine children, aged 2.5 months to 16 years, presenting with tachyarrhythmias were treated with intravenous (i.v.) flecainide, a type 1C antiarrhythmic drug. There were four boys and five girls; seven were supraventricular and two ventricular tachycardias and three had structural cardiac abnormalities. The i.v. dose required to terminate the arrhythmias ranged from 1.0 to 2.4 mg/kg (mean 1.55 mg/kg) although a mean of 1.94 mg/kg per dose was required to maintain sustained sinus rhythm after a single i.v. dose. Eight of the patients — six supraventricular and two ventricular tachyarrhythmias, required maintenance oral flecainide. Oral dosages of 6.7–9.5 mg/kg per day (mean of 7.97 mg/kg per day in three divided doses) were required to effectively prevent the tachyarrhythmias. Intravenous and oral flecainide are safe and effective in terminating supraventricular and ventricular tachyarrhythmias. No evidence of proarrhythmia was found in the patients during follow up of between 5 and 9 months. The present limitation of performing radiofrequency ablation on infants and small children justifies the important place of medical therapy for re-entrant supraventricular tachyarrhythmias.     

Transesophageal Electrophysiological Evaluation of Children with a History of Supraventricular Tachycardia in Infancy

Supraventricular tachycardia (SVT) presenting in the neonatal period may resolve by 1 year of age. Predicting which patients require therapy beyond 1 year of age is desirable. Pediatric electrophysiology databases from two institutions were reviewed for patients with a history of infant SVT who underwent transesophageal electrophysiology study (TEEPS) after initial SVT and before 2 years of age. All patients were tested off medications and followed for clinical recurrence. Forty-two patients presented with SVT at median age of 4 days (0–300 days). Initial control was achieved with one drug in 31 patients and multiple drugs in 11 patients. Prior to TEEPS, nine patients had clinical recurrence in the first year of life after initial control had been previously achieved. For all patients, TEEPS was performed, without complications, at median 13 months (9–22 months) of age and at median of 13 months (6–22 months) following the initial SVT episode. SVT was inducible in 27/42: 8 atrio-ventricular nodal reentry tachycardia (AVNRT) and 19 atrio-ventricular reciprocating tachycardia (AVRT). Inducibility was not associated with age at presentation, age at TEEPS, ventricular dysfunction at presentation, presence of structural congenital heart disease, number of drugs required to initially control SVT, or SVT recurrence after initial control. Of 15 not inducible at TEEPS, none had known SVT recurrence off medications at median follow-up of 27 months (6–37 months). In conclusion, among patients having SVT in early infancy, (1) TEEPS results are not associated with clinical variables, (2) non-inducibility is a good indicator of lack of clinical recurrence at intermediate follow-up, and (3) AVNRT may be more prevalent in infancy than previously reported.     

Adherence to isoniazid preventive chemotherapy: a prospective community based study

Background

Current international guidelines recommend 6–9 months of isoniazid (INH) preventive chemotherapy to prevent the development of active tuberculosis in children exposed to a susceptible strain of M tuberculosis. However, this is dependent on good adherence and retrospective studies have indicated that adherence to unsupervised INH preventive chemotherapy is poor.

Aim

To prospectively document adherence to six months of unsupervised INH monotherapy and outcome in children with household exposure to an adult pulmonary tuberculosis index case.

Methods

From February 2003 to January 2005 in two suburbs of Cape Town, South Africa, all children <5 years old in household contact with an adult pulmonary tuberculosis index case were screened for tuberculosis and given unsupervised INH preventive chemotherapy once active tuberculosis was excluded. Adherence and outcome were monitored.

Results

In total, 217 index cases from 185 households were identified; 274 children <5 years old experienced household exposure, of whom 229 (84%) were fully evaluated. Thirty eight children were treated for tuberculosis and 180 received preventive chemotherapy. Of the children who received preventive chemotherapy, 36/180 (20%) completed ⩾5 months of unsupervised INH monotherapy. During the subsequent surveillance period six children developed tuberculosis: two received no preventive chemotherapy, and four had very poor adherence.

Conclusion

Adherence to six months of unsupervised INH preventive chemotherapy was poor. Strategies to improve adherence, such as using shorter duration multidrug regimens and/or supervision of preventive treatment require further evaluation, particularly in children who are at high risk to progress to disease following exposure.     

经食管心房调搏在儿童阵发性室上性心动过速机制研究中的价值

目的探讨经食管心房调搏(TEAP)在儿童阵发性室上性心动过速(PSVT)机制研究中的价值。方法回顾性分析2008年1月至2013年12月行TEAP检查且后期行射频消融术(RFCA)的50例PSVT患者的电生理资料。结果以经心内电生理检查(IEPS)为诊断金标准,TEAP对房室结折返性心动过速(AVNRT)、左侧房室旁道(LAP)、右侧房室旁道(RAP)的灵敏度分别为92.9%、83.1%、90%,特异度为86.4%、100%、95%,准确性为90%、96%和94%。TEAP对AVNRT诊断符合率为92.9%(26/28),其中对慢快型AVNRT的诊断符合率为100%,而2例快慢型的AVNRT均被误诊为房室折返性心动过速(AVRT)。TEAP对AVRT诊断的符合率为86.4%(19/22),3例被诊断为慢快型的AVNRT。结论 TEAP对儿童PSVT发生机制的判定及初步定位具有很好的临床实用价值,但对少数PSVT发生机制的判定具有一定的局限性。     

Effectiveness and safety of intravenous amiodarone in drug-resistant tachyarrhythmias of children

Background: Experience with pediatric use of intravenous amiodarone is limited. In this study, our experiences with intravenous amiodarone in children with acute life-threatening or chronic tachyarrhythmias are reviewed. Methods and Results: Twelve patients, with a mean age of 3.4 ± 3.1 years, range 9 months-10 years (two with incessant ventricular tachycardia, one with ectopic atrial tachycardia, two with atrioventricular re-entrant tachycardia (three episodes), four with postoperative or congenital junctional ectopic tachycardia, two with bradycardia-tachycardia syndrome, one with atrial tachycardia) were treated with intravenous amiodarone during 13 tachycardia episodes. Left ventricular systolic functions were depressed in six patients. In 11 patients, a median of two drugs (range one-four), including adenosine infusion and in five cases direct current cardioversion were tried without success prior to intravenous amiodarone. The loading dose of amiodarone was 5 mg/kg in all episodes, infused over 1 h. Maintenance infusion was required in 12 episodes. In 10 episodes (77%), amiodarone was considered effective, in one (7.6%) partially effective (junctional ectopic tachycardia) and in two (15.4%) ineffective (sick sinus syndrome, atrial tachycardia). Therapeutic effect was obtained in a median period of 30 h (range1–103 h). The mean effective maintenance dose was 10 ± 4.7μg/kg per min (range5–15 Hg/kg per min). In one patient, mild hypotension, and in three patients cellulitis occurred, but none of them necessitated termination of treatment. Conclusions: Intravenous amiodarone is found to be an effective and safe antiarrhythmic agent for children with acute life-threatening and chronic tachyarrhythmias and depressed left ventricular systolic functions.     

Elektrophysiologische Untersuchung und Katheterablation

Background

In the last 20 years, significant progress could be achieved in the diagnosis and therapy of tachyarrhythmias in children and adolescents. Electrophysiological study and catheter ablation of supraventriuclar tachycardia have proved to be extremely effective and safe procedures. Therefore, this therapy can be offered today as first-line therapy to families with symptomatic older children and adolescents.

Aim of article

This report briefly illustrates symptoms and natural course of paroxysmal supraventricular tachycardia in the young. Subsequently, principles of electrophysiological study and catheter ablation including the results as achieved so far in children are presented. Typical clinical situations are discussed according to the current guidelines of the German Society for Pediatric Cardiology. Finally, for pediatric patients with asymptomatic ventricular preexcitation current guidelines are discussed.     

Recurrent ventricular tachycardia in asymptomatic young children with an apparently normal heart

Abstract Ventricular tachycardia without underlying heart disease is rare in infancy and childhood. Four young children (median age 8 months at initial presentation) with frequently recurrent episodes of asymptomatic and self-limiting ventricular tachycardia are reported. By noninvasive investigation no apparent heart disease has been found in all patients. Initially three of the four children had been treated with an anti-arrhythmic drug. Treatment was soon stopped in two patients for lack of symptoms and for lack of efficacy of therapy; one patient remained on beta-blocker therapy. One child did not receive anti-arrhythmic therapy. After a mean follow up of 32 months all patients continued to be asymptomatic despite frequently recurrent episodes of self-limiting ventricular tachycardia.Conclusion Ventricular tachycardia in asymptomatic children with an otherwise normal heart carries a good prognosis. Invasive investigation (cardiac catheterization with electrophysiological study and right ventricular biopsy) can be with-hold, as long as there are no symptoms. For lack of efficiency of antiarrhythmic drugs in suppressing ventricular tachycardia in asymptomatic children with apparently normal hearts, these patients may be left without therapy but have to be followed closely.     

CHRONIC SUPRAVENTRICULAR TACHYCARDIA IN INFANCY AND CHILDHOOD

ABSTRACT: Jacobsen, J. R., Andersen, E. D., Sandøe, E., Videbeek, J. and Wennevold, A. (Medical Department B and Department of Paediatrics, Rigshospitalet, Queen Louise's Hospital for Children, Copenhagen, and Departments of Cardiology and Paediatrics, århus Kommunehospital, århus, Denmark). Chronic supraventricular tachycardia in infancy and childhood. Acta Paediatr Scand, 64:597, 1975.–The results of a one to 19 year follow-up study of 9 children with supraventricular tachycardia of more than one month's duration are reported. The ECG diagnosis of tachycardia was made before birth in one patient and between the ages of 8 months and 12 years in 8. Four had sustained and 4 had repetitive tachycardia, while one patient had both patterns at different times. Reciprocal rhythm was diagnosed in 3 patients and exit block in 2. Severe symptoms had occurred in 2 patients, but as a rule symptoms were mild or absent. No treatment abolished the arrhythmias but digitalis reduced the overall ventricular rate in 6 patients. After a duration of 1–7 years, 3 patients still had tachycardia at the follow-up. In the remaining 6 patients the tachycardia had subsided 7 months to 10 years after the onset.     

Virus myocarditis in a 1‐month‐old boy presenting as two types of paroxysmal supraventricular tachycardia

Herein we describe the case of a 1‐month‐old boy with acute viral myocarditis, who presented with two kinds of paroxysmal supraventricular tachycardia, and who was cured after medical treatment. He was brought to the emergency room with poor feeding due to fever. On the third day of hospitalization, a narrow QRS tachycardia (180–200 beats/min) was detected. Echocardiography showed a high echoic area at the atrial septum around the atrioventricular node. The patient was clinically diagnosed with acute myocarditis. The narrow QRS tachycardia was diagnosed as incessant junctional ectopic tachycardia. The patient was treated with propranolol and landiolol. The frequency of the tachycardia decreased, but a different narrow QRS tachycardia was detected on the 15th day of hospitalization on electrocardiogram (220 beats/min), which was ascribed to atrioventricular nodal re‐entrant tachycardia. Atenolol was effective for the tachycardia. At 2 years follow up, cardiac function was normal and tachycardia had not recurred.     

Dysrhythmias after the modified Fontan procedure

Summary The cardiac rhythm before and after the modified Fontan procedure was reviewed in 24 patients. Transient atrial dysrhythmias were common in the immediate postoperative period. Late postoperative premature atrial contractions were detected by ambulatory monitoring in 20 of 23 patients; eight (34.8%) had supraventricular tachycardia. Late ventricular dysrhythmia was detected in 18 of 23 patients: ten had low-grade ventricular dysrhythmias and eight (34.8%) had multiform premature ventricular contractions. Five of the latter had couplets and one of these five plus another had ventricular tachycardia. Seven patients with supraventricular tachycardia and five patients with ventricular dysrhythmia required antiarrhythmic medication. Asymptomatic bradycardia was detected in five patients (21.7%). One patient had intermittent second-degree atrioventricular block. No specific risk factors predicted dysrhythmias. Thus, cardiac dysrhythmias were common in patients after the modified Fontan procedure, but were well tolerated in most patients. No sudden deaths or syncopal episodes have occurred during a mean follow-up of 5 years. One patient's death was related to severe left ventricular dysfunction. Permanent pacing has not been required in any patient.