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Objectives: We sought to determine the implications of implantable cardioverter-defibrillator (ICD) placement in children and patients with congenital heart disease (CHD)., Background: There is increasing frequency of ICD use in pediatric and CHD patients. Until recently, prospective registry enrollment of ICD patients was not available, and children and CHD patients account for only a small percentage of ICD recipients. Therefore, we retrospectively obtained collaborative data from 4 pediatric centers, aiming to identify implant characteristics, shock frequency, and complications in this unique population., Methods: Databases from 4 centers were collated in a blinded fashion. Demographic information, implant electrical parameters, appropriate and inappropriate shock data, and complications were recorded for all implants from 1992 to 2004., Results: A total of 443 patients were included, with a median age of 16 years (range 0 to 54 years) and median weight of 61 kg (range 2 to 130 kg), with 69% having structural heart disease. The most common diagnoses were tetralogy of Fallot (19%) and hypertrophic cardiomyopathy (14%). Implant indication was primary prevention in 52%. Shock data were available on 409 patients, of whom 105 (26%) received appropriate shocks (mean 4 shocks/patient, range 1 to 29 shocks/patient). Inappropriate shocks occurred in 87 of 409 patients (21%), with a mean of 6 per patient (range 1 to 60), mainly attributable to lead failure (14%), sinus or atrial tachycardias (9%), and/or oversensing (4%)., Conclusions: Children and CHD ICD recipients have significant appropriate and inappropriate shock frequencies. Optimizing programming, medical management, and compliance may diminish inappropriate shocks. Despite concerns regarding generator recalls, lead failure remains the major cause of inappropriate shocks, complications, and system malfunction in children. Prospective assessment of ICD usage in this population may identify additional important factors in pediatric and CHD patients.

Objectives: We sought to characterize the clinical nature of atrial flutter (AFL) in a large cohort of infants., Background: There are no large studies describing the natural history of AFL in infants. Previous studies vary in the therapy used and expected prognosis., Methods: We reviewed the records of all children younger than 1 year of age who were diagnosed with AFL at our hospital during the past 25 years, excluding those with previous cardiac surgery., Results: We identified 50 infants with AFL. Most, 36 (72%), presented within the first 48 h of life. Congestive heart failure was evident in 10 infants, with 6 presenting at 1 day of age, and 4 presenting beyond 1 month of age. The remainder were asymptomatic. A large atrial septal defect was the only structural heart disease. Spontaneous conversion to sinus rhythm occurred in 13 (26%) infants. Sinus rhythm was restored in 20 of 23 (87%) attempts at direct current cardioversion and 7 of 22 (32%) attempts at transesophegeal pacing; 7 required antiarrhythmic therapy. An additional arrhythmia, all supraventricular, appeared in 11 (22%) infants. The recurrence of AFL developed in 6 infants; 5 of 6 of these incidents occurred within 24 h of the first episode. All patients with recurrence had an additional arrhythmia., Conclusions: Infants with AFL usually present within the first 2 days of life. No association was found with structural heart disease. Direct current cardioversion appears to be most effective at establishing sinus rhythm. Chronic AFL has the potential to cause cardiovascular compromise. Atrial flutter in the absence of other arrhythmias has a low risk of recurrence. Once in sinus rhythm, infants with AFL have an excellent prognosis and may not require chronic antiarrhythmic therapy.

Objectives: We assessed the clinical presentation, natural history, and treatment response of atrial ectopic tachycardia (AET) in children <3 years of age (group 1) compared with those > or =3 years of age (group 2)., Background: Atrial ectopic tachycardia is a common cause of chronic supraventricular tachycardia in children and can be resistant to pharmacologic therapy. Radiofrequency ablation (RFA) can eliminate AET arising from a single focus., Methods: A retrospective review identified all children at Texas Children's Hospital diagnosed with AET from March 1991 to November 2000. Data obtained included clinical presentation, echocardiographic evaluation, response to antiarrhythmic therapy, spontaneous resolution, and outcomes of radiofrequency and surgical ablation., Results: Sixty-eight children were identified (22 children <3 years and 46 children > or =3 years of age). Control of AET with antiarrhythmic therapy was achieved in 91% of the younger children but only 37% of the older children (p < 0.001). There was a higher rate of spontaneous resolution in the younger group (78%) compared with the older group (16%) (p < 0.001). Radiofrequency ablation was performed in 35 of the older children, with ultimate success in 74%. Surgical intervention was required for six children., Conclusions: Younger children respond to antiarrhythmic therapy and have a high incidence of AET resolution, thus warranting a trial of antiarrhythmic therapy. In children > or =3 years, AET is unlikely to resolve spontaneously, and antiarrhythmic medications are frequently ineffective. Thus, RFA should be considered early in the course of treatment for these children; however, surgical intervention may be necessary.

Objectives: The goal of this study was to assess the efficacy and safety of the combination therapy of flecainide and sotalol for the treatment of refractory supraventricular tachycardia (SVT) in children <1 year of age., Background: Supraventricular tachycardia in infants can be refractory to single-drug as well as standard combination medical therapy. Radiofrequency ablation (RFA) is the definitive treatment of refractory SVT; however, interventional therapy poses a high risk of morbidity and mortality in this age group., Methods: A retrospective review was performed identifying infants who required flecainide and sotalol to control refractory SVT. Patient age, previous drug therapy, duration of treatment, flecainide levels and corrected QT intervals were recorded; 24 h Holter monitoring was utilized to gauge efficacy of treatment. Efficacy was defined as suppression of SVT to no more than rare nonsustained episodes or slowing of SVT to a clinically tolerable rate., Results: Ten patients (median age: 29 days, range: 1 to 241 days) failed at least two antiarrhythmic agents including either flecainide or sotalol as single agents before initiating combination therapy. Efficacy was achieved in all patients. The failure rate for therapy was reduced from 100% to 0% (95% confidence interval: 0% to 26%). The median doses used were: flecainide 100 mg/m(2)/day (range: 40 to 150 mg/m(2)/day) and sotalol 175 mg/m(2)/day (range: 100 to 250 mg/m(2)/day). Median duration of therapy was 16 months (range: 5 to 35 months). No proarrhythmia occurred., Conclusions: The combination of flecainide and sotalol can safely and effectively control refractory SVT and may obviate the need for RFA in children <1 year.

Objective: We report 16 infants with complete congenital heart block (CHB) who developed late-onset dilated cardiomyopathy despite early institution of cardiac pacing., Background: Isolated CHB has an excellent prognosis following pacemaker implantation. Most early deaths result from delayed initiation of pacing therapy or hemodynamic abnormalities associated with congenital heart defects., Methods: A multi-institutional study was performed to identify common clinical features and possible risk factors associated with late-onset dilated cardiomyopathy in patients born with congenital CHB., Results: Congenital heart block was diagnosed in utero in 12 patients and at birth in four patients. Ten of 16 patients had serologic findings consistent with neonatal lupus syndrome (NLS). A pericardial effusion was evident on fetal ultrasound in six patients. In utero determination of left ventricular (LV) function was normal in all. Following birth, one infant exhibited a rash consistent with NLS and two had elevated hepatic transaminases and transient thrombocytopenia. In the early postnatal period, LV function was normal in 15 patients (shortening fraction [SF] = 34 +/- 7%) and was decreased in one (SF = 20%). A cardiac pacemaker was implanted during the first two weeks of life in 15 patients and at seven months in one patient. Left ventricular function significantly decreased during follow-up (14 days to 9.3 years, SF = 9% +/- 5%). Twelve of 16 patients developed congestive heart failure before age 24 months. Myocardial biopsy revealed hypertrophy in 11 patients, interstitial fibrosis in 11 patients, and myocyte degeneration in two patients. Clinical status during follow-up was guarded: four patients died from congestive heart failure; seven required cardiac transplantation; one was awaiting cardiac transplantation; and four exhibited recovery of SF (31 +/- 2%)., Conclusions: Despite early institution of cardiac pacing, some infants with CHB develop LV cardiomyopathy. Patients with CHB require close follow-up not only of their cardiac rate and rhythm, but also ventricular function.

Objective: The purpose of this study was to analyze the efficacy and safety of intravenous amiodarone in young patients with critical, drug-resistant arrhythmias., Background: Intravenous amiodarone has been investigated in adults since the early 1980s. Experience with the drug in young patients is limited. A larger pediatric study group was necessary to provide responsible guidelines for the drug's use before its market release., Methods: Eight centers obtained institutional approval of a standardized protocol. Other centers were approved on a compassionate use basis after contacting the primary investigator (J.C.P)., Results: Forty patients were enrolled. Standard management in all failed. Many patients had early postoperative tachyarrhythmias (25 of 40), with early successful treatment in 21 (84%) of 25. Twelve patients had ventricular tachyarrhythmias: seven had successful therapy, and six died, none related to the drug. Eleven patients had atrial tachyarrhythmias: 10 of 11 had immediate success, but 3 later died. Fourteen patients had junctional ectopic tachycardia, which was treated with success (sinus rhythm or slowing, allowing pacing) in 13 of 14, with no deaths. Three other patients had supraventricular tachycardias, with success in two and no deaths. The average loading dose was 6.3 mg/kg body weight, and 50% of patients required a continuous infusion. Four patients had mild hypotension during the amiodarone bolus. One postoperative patient experienced bradycardia requiring temporary pacing. There were no proarrhythmic effects. Deaths (9 [23%] of 40) were not attributed to amiodarone., Conclusions: Intravenous amiodarone is safe and effective in most young patients with critical tachyarrhythmia. Intravenous amiodarone can be lifesaving, particularly for postoperative junctional ectopic tachycardia, when standard therapy is ineffective.

Objectives: This study assessed the safety and efficacy of combined flecainide and amiodarone therapy in controlling refractory tachyarrhythmias in infants., Background: Single-drug as well as standard combination medical therapy for tachyarrhythmias in infants sometimes fails. In those cases, one may consider interventional therapy. However, this option may carry a high risk of morbidity and mortality in infants. The natural history of tachyarrhythmias in infants often favors eventual resolution and reinforces the importance of selecting an effective medical regimen., Methods: We performed a retrospective analysis of nine infants (median age 2 months) who received combined flecainide and amiodarone therapy for attempted control of refractory tachyarrhythmias. Trough serum drug levels of flecainide were monitored, and 24-h ambulatory electrocardiographic monitoring was used to determine efficacy of therapy., Results: Single-drug treatment with flecainide or amiodarone failed in all of the infants studied. An average of four drugs failed (range one to six) before administration of combined flecainide and amiodarone therapy. During combined therapy, the flecainide dose was 70 to 110 mg/m2 per day, and that for amiodarone was 7.5 to 13.5 mg/kg per day for a mean (+/- SD) of 9 +/- 2 days to load and 5 to 12 mg/kg per day as maintenance. Successful control of tachyarrhythmias was demonstrated in seven (78%) of nine infants (95% confidence interval 46% to 99%) (three of three with congenital junctional ectopic tachycardia, three of three with supraventricular tachycardia and one of three with ventricular tachycardia). During combined therapy, flecainide trough levels ranged from 350 to 731 ng/ml. Corrected QT intervals varied from 0.440 to 0.488 ms. No proarrhythmia occurred. None of the infants required a pacemaker, and all had normal left ventricular dimensions and fractional shortening by echocardiography. Eight of nine infants had a structurally normal heart. One infant had surgical correction of an atrioventricular septal defect., Conclusions: Combination therapy with flecainide and amiodarone appears to be safe and effective in controlling refractory tachyarrhythmias in infants. The combination of flecainide and amiodarone may obviate the need for early interventional therapy or may allow delay until the child is older.

Objectives: We hypothesized an association between atrial thrombi and nonfibrillation atrial tachyarrhythmias in patients with congenital heart disease., Background: We observed a fatal thromboembolus after direct current cardioversion in an adolescent with atrial flutter and repaired tetralogy of Fallot., Methods: Using transesophageal echocardiography, we prospectively studied 19 consecutive patients with congenital heart disease with nonfibrillation atrial tachyarrhythmia (atrial flutter in 18, primary atrial tachycardia in 1) undergoing electrophysiologic procedures (median age 19.6 years, range 7.0 to 53.8; 11 male, 8 female). Transthoracic echocardiograms were available for 17 patients., Results: All transesophageal examinations were performed without incident. No atrial thrombi were detected in 11 patients who subsequently had uncomplicated direct current cardioversion. Eight solitary atrial thrombi were detected (incidence 42%). Six thrombi were located in the right atrium (Fontan repair in four patients, Ebstein's malformation repair in two), and two were noted in the left atrium (congenital hypertrophic cardiomyopathy and atrial septal defect repair in one patient each). Transthoracic echocardiograms were available in seven of eight patients with thrombus detected by transesophageal echocardiography, with only one study conclusive for an atrial thrombus. Cardioversion was deferred in six of eight patients with thrombus, and anticoagulation therapy was initiated. Uncomplicated electrophysiologic procedures were conducted in two patients at the time of detection of right atrial thrombus (atrioventricular node ablation in one patient, direct current cardioversion in the other)., Conclusions: Prothrombin conditions exist in patients with congenital heart disease with nonfibrillation atrial tachyarrhythmias, as indicated by a significant incidence of transesophageally detected atrial thrombi. The need for prophylactic anticoagulation and the safety of pharmacologic or direct current cardioversion are issues that remain unresolved.

Objectives: We sought to examine whether resolution of occult myocarditis in children with associated ventricular arrhythmia correlated with the presence of arrhythmia at late follow-up., Background: Complex ventricular arrhythmias have been documented in children with myocarditis. Therapy is aimed at controlling the arrhythmia and any associated ventricular dysfunction. However, no reported studies have documented whether resolution of myocarditis in children is associated with resolution of the associated arrhythmias., Methods: We performed a retrospective analysis of 12 patients (mean age 12 years) with myocarditis. Ambulatory electrocardiographic (Holter) monitors were reviewed for ventricular arrhythmias at presentation and follow-up. Patients were assigned to Group I if they received corticosteroids in addition to any antiarrhythmic agents and to Group II if they did not receive steroids. Follow-up endomyocardial biopsy was performed in some patients, and results were analyzed in relation to the presence of arrhythmias at follow-up., Results: Eleven patients had ventricular tachycardia, and one had multiform couplets. Corticosteroids were given to seven patients (Group I). Follow-up biopsy was performed in seven patients (six received steroids), with resolution of inflammation in all; four of the seven still had ventricular arrhythmias but with improved control. Of the five patients without follow-up biopsy, three had persistent arrhythmia. Absence of inflammation at follow-up biopsy did not correlate with loss of ventricular arrhythmias, and there was no difference between Group I and II patients with respect to resolution of arrhythmia (Fisher exact test, p = 0.70, power 11%)., Conclusions: Complex ventricular arrhythmias persist after apparent resolution of occult myocarditis in children. Although these arrhythmias are easier to control after such resolution, the patients may require long-term antiarrhythmic therapy.

Objectives: The purpose of this study was to evaluate the efficacy of intravenous amiodarone in young patients., Background: Oral amiodarone therapy has proved useful for problematic arrhythmias in children, but its pharmacokinetics with the oral route preclude its use in several acute settings., Methods: Intravenous amiodarone was administered in 1-mg/kg body weight aliquots followed by continuous infusion to patients with potentially life-threatening tachyarrhythmias that had not been abolished by standard therapies., Results: Ten patients (mean age 6.8 years) received intravenous amiodarone: for ventricular tachycardia in seven patients and for atrial tachycardia, junctional tachycardia and multiple arrhythmias in one patient each. Surgery for congenital heart defects had been performed previously in six patients. Two patients had a hamartoma causing ventricular tachycardia. Six of 10 patients had complete resolution of arrhythmia with intravenous amiodarone: 4 of 7 with ventricular tachycardia, 1 of 1 with atrial tachycardia and 1 of 1 with postoperative junctional ectopic tachycardia. Intravenous amiodarone was not successful in the two patients with a hamartoma but slowed ventricular tachycardia in one, allowing successful surgical cure. Average drug load at the time of effect was 4.8 mg/kg body weight. Four patients had transient hypotension during loading, corrected with volume or low dose calcium. Intravenous infusion of amiodarone, 10 mg/kg per day, continued an average of 3 days. Four of 10 patients died, all of nonarrhythmic causes not attributable to intravenous amiodarone., Conclusions: Intravenous amiodarone was well tolerated in this small series of patients. Postoperative ventricular tachycardia was responsive to intravenous amiodarone in 80% (8 of 10) of the patients (95% confidence interval 40% to 99%). Use of this drug in acute, postoperative tachyarrhythmias may be lifesaving in some patients when standard intravenous therapies fail.

Objectives: The purpose of this report is to summarize our entire surgical experience in the treatment of tachyarrhythmias in children. We emphasize our application of a newer computerized mapping system for use in both the electrophysiology laboratory and the operating room to localize points of activation of the tachyarrhythmias., Background: A retrospective review was undertaken to examine the results of operative procedures in 290 children undergoing surgical treatment for tachyarrhythmias from 1977 to the present., Methods: Operative procedures were performed in 290 children and consisted of the following: surgical ablation of accessory pathways of the Kent bundle type (210 children); surgery with cryoablation for atrial ectopic tachycardia (35 children); surgical excision or cryoablation, or both, for ventricular tachycardia (26 children); cryoablation for the permanent form of junctional reciprocating tachycardia (15 children) and atrioventricular (AV) node reentrant tachycardia (4 children)., Results: The surgical cure rate for accessory pathway tachycardia in the era before computerized mapping was 80% (41 patients) in the period from 1977 to 1982 and 95% (86 patients) in the period from 1982 to 1988. This rate improved to 100% (83 patients) after the advent of the computerized mapping technique. These improved results are probably due to a combination of factors, including increasing experience in electrophysiologic mapping and surgery, and cannot be attributed to the computerized mapping system alone. Surgical cure or major improvement in symptoms was documented in 33 (94%) of 35 patients with atrial ectopic tachycardia. Surgical cure was accomplished in 25 (96%) of 26 patients with the complex form of ventricular tachycardia. In 19 patients with the permanent form of junctional reciprocating tachycardia and the more typical AV node reentrant tachycardia, the surgical cure rate was 100%., Conclusions: In all forms of supraventricular reentrant tachycardia that occur in children, preoperative computerized mapping techniques combined with intraoperative computerized mapping and surgical ablation can eliminate tachycardia at a success rate of close to 100%. Computerized mapping techniques are less accurate in patients with atrial ectopic tachycardia because of multiple foci and a broader surface area to be mapped. This experience demonstrates that excellent results can be achieved in the surgical treatment of tachyarrhythmias in children.

Previous studies in adults with dilated cardiomyopathy suggest that the presence of arrhythmia, especially ventricular tachycardia, correlates with increased mortality. We performed a retrospective analysis of 63 children with idiopathic dilated cardiomyopathy to determine the prognostic significance of arrhythmias and other findings with respect to mortality. The mean age at diagnosis of the cardiomyopathy was 4.96 +/- 5.3 years. The overall mortality rate was 16% over a 10 year follow-up period. Persistent congestive heart failure and ST-T wave changes correlated with increased mortality (p less than 0.05). No other variables affected outcome. Arrhythmias were found in 46% of the patients; of the arrhythmias, 48% were atrial arrhythmias. Ventricular tachycardia was present in six patients. Death occurred in 4 (14%) of 29 patients with known arrhythmia; 1 of the 5 died suddenly. The remaining 6 deaths in the series occurred in the 34 patients without a documented arrhythmia. It is concluded that 1) arrhythmias are frequently seen in children with dilated cardiomyopathy but are not predictive of outcome; 2) sudden death in children with this disease is rare; and 3) persistent congestive heart failure portends a poor prognosis.