Radiofrequency catheter ablation for tachyarrhythmias in children and adolescents. The Pediatric Electrophysiology Society

Acute coronary artery stenosis during slow pathway ablation for atrioventricular nodal reentrant tachycardia in a child

Coronary injury during radiofrequency ablation is a rare but n. potentially life-threatening complication that has been reported for attempted elimination of accessory pathways. This is the first report of coronary artery injury during slow pathway ablation for AV nodal reentrant tachycardia. Manifest signs of injury may be transient or nonexistent and easily missed. Controlled studies are needed to determine the true risk of coronary artery injury during radiofrequency ablation for supraventricular tachycardia, particularly in small children.

Clinical course of atrial ectopic tachycardia is age-dependent: results and treatment in children < 3 or > or =3 years of age

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.

Radiofrequency Catheter Ablation in Small Children:. Relationship of Complications to Application Dose

Little data exists to support the use of procedural modifications during radiofrequency catheter ablation (RFCA) in small children. A single institution database was reviewed for patients under 15 kg undergoing RFCA from January 1998 to August 2001. Of 268 RFCA procedures, 18 were done in 14 patients under 15 kg (median weight 5.7 kg, 3.5-13.7; age 5.8 months, 1.2-19.8). Six patients had normal hearts, 4 had congenital heart disease, and 4 patients had cardiomyopathy. Diagnoses were orthodromic reciprocating tachycardia (ORT) in nine patients/nine studies, chaotic atrial tachycardia (CAT) in one patient/two studies, and VT in four patients/seven studies. RFCA variables included maximum temperature (69 degrees C, 50-78), total applications (10, 2-21), applications > 20 seconds (5, 0-15), and total application time (331 s, 26-1,006 s). Complications were pericardial effusion in 1 patient, mild mitral regurgitation in 1, and myocardial infarction in 1 patient. When indexed for weight, the number of applications with a duration > 20 seconds in the ORT group was significantly greater in complicated versus uncomplicated procedures (0.7 applications/kg vs 0.16 applications/kg, P = 0.05). In addition, for the ORT subgroup, the indexed total application time trended higher in complicated versus uncomplicated procedures (40.6 s/kg, vs 6.6 s/kg, P = 0.1). RFCA success was 9/9 in ORT, 6/7 in VT, and 0/2 in CAT. RFCA can be successful in small children; however, complications appear to be related to RF dose indexed for body size. Thus, the decision to proceed with RFCA, and the application duration and number should be guided by patient size, balanced against the risks of the arrhythmia, and reserved for dire circumstances.

Ablation of tachyarrhythmias in pediatric patients

PURPOSE OF REVIEW

Radiofrequency (RF) ablation treatment for tachyarrhythmias has been available only for the past 15 years. The success rates have been excellent with a very low frequency of complications. Because of this efficacy, the use of RF ablation in children has become standard of care even though long-term data are unavailable. In this review, common tachyarrhythmias and their current treatments in children will be discussed.

RECENT FINDINGS

Novel electrophysiology technologies such as electroanatomic mapping and sophisticated ablating catheters have improved success rates and decreased complications. The improvement is also due to better understanding of the mechanisms and etiologies of tachyarrhythmias. Both have positively impacted success rates and have made more complicated tachyarrhythmias treatable with ablation.

SUMMARY

The technologic advances in ablation and improved understanding of tachyarrhythmias over the past 15 years have greatly improved outcomes in ablative treatment of tachyarrhythmias in children. In most cases this method of treatment is the preferred first-line approach to symptomatic tachyarrhythmias in children.

[15-year-old patient with decompensated heart failure and tachycardia with negative P-waves in inferior ECG recordings. An indication for heart transplantation?]

A 15-year-old girl was admitted with signs of severe cardiac failure. There were no symptoms of cardiac insufficiency 4 weeks before hospital admission. She presented with permanent supraventricular tachycardia with negative P-waves in leads II, III and aVF, the heart rate was 150 beats per minute. The electrophysiological examination showed a permanent junctional reentry tachycardia. A postero-septal accessory pathway could be eliminated successfully by radiofrequency catheter ablation. Immediately after the procedure cardiac function deteriorated with slight decrease of the strongly reduced cardiac output. Intensive care and application of dobutamine led to clinical stability. During a follow-up of two years the young patient showed permanent sinus rhythm and an age related physical strain. This case report documents the rapid and severe manifestation of cardiac failure owing to permanent junctional reentry tachycardia in a 15-year-old girl. She was referred for consideration of heart transplantation. Invasive electrophysiological treatment led to permanent sinus rhythm with improvement of left ventricular function.

Radiofrequency catheter ablation of septal accessory pathways in the pediatric age group

Radiofrequency catheter ablation (RCA) of septal accessory pathways may be technically challenging in children due to the risk of inadvertent atrioventricular (AV) block in the setting of small cardiac dimensions. Outcomes were reviewed for all patients aged < or =19 years with manifest and concealed septal accessory pathways undergoing RCA since 1990 at a single institution. One hundred forty-five procedures were performed in 127 patients (mean age 11.6 years). The number of studies according to accessory pathway location were: anteroseptal (n = 36), midseptal (n = 20), mouth of coronary sinus (n = 40), middle cardiac vein (n = 6), right posteroseptal (n = 21), and left posteroseptal (n = 22). Ablation was deferred for 9 patients (6 anteroseptal and 3 midseptal) in favor of additional pharmacologic trials. Acute success rates for targeted accessory pathways were: anteroseptal (96%), midseptal (94%), mouth of coronary sinus (88%), middle cardiac vein (100%), right posteroseptal (100%), and left posteroseptal (96%). Recurrence rates during follow-up were: anteroseptal (14%), midseptal (12%), mouth of coronary sinus (3%), right posteroseptal (4%), and left posteroseptal (4%). Permanent second or third degree AV block occurred in 4 of 136 RCA attempts (3%), involving 2 anteroseptal and 2 midseptal pathways. In 3 of these 4 cases, a high probability of block was anticipated from prior ablation efforts, prompting pacemaker insertion before or in conjunction with RCA. Thus, in the pediatric age group, acute RCA success rates for septal accessory pathways can exceed 90%. The risks of AV block and accessory pathway recurrence are most relevant to anteroseptal and midseptal pathways. These data may be factored into patient selection and the decision whether to ablate.

Complete occlusion of the left circumflex coronary artery after radiofrequency catheter ablation in an infant

Radiofrequency catheter ablation of a left lateral accessory atrioventricular pathway was performed in a 5-week-old infant with drug-refractory supraventricular tachycardia. Energy application via a 5-French mapping and ablation catheter in the temperature-controlled mode (60 degrees C, 30 W) at the atrial aspect of the mitral valve annulus repeatedly resulted in termination of the tachycardia by conduction block within the pathway. Tachycardia remained inducible subsequently. After a safety energy application during sinus rhythm, significant ST-segment elevation in the inferior, mid precordial, and left lateral leads was noted. Selective left coronary angiography revealed complete occlusion of the circumflex coronary artery. Moderate-to-severe mitral valve regurgitation developed, finally requiring mitral valve replacement.

The role of isoproterenol testing following radiofrequency catheter ablation of accessory pathways in children

Isoproterenol (ISO) testing following radiofrequency catheter ablation (RFCA) of accessory pathways (APs) in children is often performed to assess efficacy. However, its role in postablative testing for this indication has not been previously studied. In view of a recent national shortage of ISO, this study reviewed the results of ISO testing in pediatric patients after acutely successful RFCA to evaluate its role in postablative testing. Seventy patients (median age 13.0 years, range 2.8-24 years) underwent acutely successful RFCA for APs. If AP conduction was not present and tachycardia was not inducible with programmed stimulation 30 minutes following RFCA, repeat testing was performed during continuous infusion ISO. ISO infusion resulted in the induction of arrhythmias in 3 (4%) of 70 patients that required further ablative therapy. None of these patients had inducible arrhythmias or AP conduction during postablative testing without ISO infusion. One patient, with the permanent form of junctional reciprocating tachycardia (PJRT), had persistence of AP conduction requiring further RFCA applications. Two patients had inducible AV nodal reentrant tachycardia (AVNRT) that was treated with slow pathway modification. At a median follow-up of 7.3 months, two (3%) patients had recurrence of tachycardia. These patients did not have inducible tachycardia, AP conduction, or dual AVN physiology with ISO testing. Although ISO may improve AP conduction in patients with PJRT and uncover AVNRT, these results suggest that ISO testing after an apparently successful AP ablation may not be necessary to confirm acute success. In addition, lack of AP conduction on ISO did not rule out the possibility of medium-term recurrence.

[Spanish registry on catheter ablation. 1st official report of the working group on electrophysiology and arrhythmias of the Spanish Society of Cardiology (year 2001)]

BACKGROUND AND OBJECTIVES

The information about the practice and results of catheter ablation of cardiac arrhythmias in Europe is limited and there is a lack of multicenter studies and registries. The Spanish Society of Cardiology developed a national registry to define the results of this procedure and the characteristics of the laboratories where it is performed.

METHODS

A list of electrophysiology laboratories in Spain was prepared and questionnaires were sent to each of them. The questionnaires were completed with retrospective data about the characteristics of each center, their general activities, and ablation procedures performed during 2001. Data were collected on the results and complications in relation to the arrhythmic substrate or mechanism treated.

RESULTS

Forty-three centers, out of a possible 48, voluntarily participated in the registry. A total of 4,374 ablation procedures were performed in 41 centers. The average number of procedures per center was 106 84 and the rates of success, major complications, and mortality were, respectively, 93%, 1.5%, and 0.1%. About 70% of the procedures were performed to treat patients with AV nodal reentrant tachycardias and accessory pathways or to abolish AV conduction.

CONCLUSIONS

The 2001 Spanish National Catheter Ablation Registry is one of the largest reported series of ablation procedures. The results of the registry demonstrate a high success rate and low complication and mortality rates in the practice of catheter ablation in Western Europe.

Role of catheter and surgical ablation in congenital heart disease

The role of surgery and radiofrequency current ablation for the treatment of tachycardias in patients with congenital heart disease The use of radiofrequency current application as a treatment strategy has stimulated a revolution in our understanding of tachycardia mechanisms. The extension of its use to patients with congenital heart defects and tachyarrhythmias has opened the door to new treatments with known success rates and known risks for mortality and morbidity. Antiarrhythmic surgery aims to dissect or excavate a responsible substrate and is especially worth considering if cardiac surgery is being undertaken for other reasons. With suitable surgical skill and interest, and with strong electrophysiologic support, high success rates have been documented. Antiarrhythmic surgical incisions have the advantage of being visually controllable regarding the extent and location of damage to myocardial tissue. In other situations, radiofrequency current ablation is preferred because of its less-invasive character, its use of local anesthesia, and the avoidance of surgical trauma. Both surgery and catheter ablation require precise clarification of the tachycardia mechanism and precise localization of the underlying substrate. The importation of such techniques into the realm of open chest surgery would be difficult in light of the need for multiple intracardiac catheters and repeated fluoroscopically guided catheter positioning. Electrophysiologic studies performed during the antiarrhythmic surgical procedure cannot provide complete information, and their use is thus restricted to the arrhythmogenic myocardial target only [32,45]. In contrast, catheter-mediated electrophysiologic studies offer the option of exact diagnosis, precise substrate localization, and interventional treatment in a single session. Moreover, validation of the linear lesion's completeness has become a reliable predictor for mid- and long-term success in avoiding recurrences. As a result, the application of catheter-mediated ablation has exploded within the past 15 years. Antiarrhythmic surgery has survived as a discipline in a decreasing number of experienced hands [43,44]. As a result of recent experiences and modern technology, success rates above 90% [74-76, 81,88] for the interventional treatment of congenital tachycardias have become comparable to those reported in patients with "normal" hearts. For acquired tachycardias, acute success rates today range about 80% at the atrial level. The rate of recurrence is still relatively high at about 10-25% [73,76,77,79,91,96,102]. Further improvements are being pursued. Data on the treatment of acquired tachycardias at the ventricular level is largely anecdotal. Good early success rates are combined with a tendency to recurrence in longer-term follow-up [50,76,103-108]. Some of the late VT ablation recurrences may be explained by the fact that fibrotic, scarred, and hypertrophic myocardial tissue at the targeted site often prevents effective radiofrequency current application and lesion generation. In order to improve RF lesion depth and continuity, newly designed technologies for radiofrequency current ("cooled tip electrode", Cordis Webster, Baldwin Park, CA), and alternative energy sources (cryo-ablation, micro-wave, or ultrasound) are being readied for introduction in the very near future. For patients suffering from recurrent tachycardias and having other reasons for open-heart surgery, a hybrid concept can be created, utilizing modern 3-D electro-anatomical reconstruction as a basis for an electrophysiologically informed surgical procedure. Following such a concept, a hemodynamic catheterization can be combined with an electrophysiologic study to define critical myocardial zones for induced macro-re-entry tachycardias, or of those zones expected to play an arrhythmogenic role in the future. With such information, surgical incisions for cardiac access and repair can be planned and performed. The role of surgery in antiarrhythmic treatment can become preventive. Myocardial tissue is incised for cannulation and repair in a way that can reduce the chance of later scar-associated tachycardias [109]. The extension of surgical cuts to physiologic barriers of electrical conduction is a major strategy for the primary prevention of postsurgical or incisional arrhythmias. In addition, the simultaneous treatment at heart surgery of already existing tachycardias can be offered within the same session as a secondary preventive concept. Despite the immense growth of knowledge and experience in recent years, there is still a need for more knowledge about the factors causing arrhythmogenesis and their interactions. Prospective and randomized studies are needed to show the most effective strategies to prevent arrhythmia-mediated death. The future of antiarrhythmic treatment will less be directed by the limitations of current interventional tools, which will be improved, and more by an evolutionary process in philosophy regarding the understanding of arrhythmogenesis in these patients as the basis for new concepts of arrhythmia prevention and treatment.

Techniques to avoid atrioventricular block during radiofrequency catheter ablation of septal tachycardia substrates in young patients

Radiofrequency catheter ablation (RFCA) has proven safe for most young patients, but the risk of inadvertent atrioventricular (AV) block remains. The purpose of this report is to describe techniques to avoid inadvertent AV block during effective RFCA in young patients with septal tachycardia substrates.

METHODS

The techniques included intubation and apnea during RFCA, coronary sinus pacing during RFCA to observe intact AV conduction during junctional ectopy, localizing the optimal His electrogram prior to RFCA, not ablating during tachycardia and titrating power output with temperature monitoring.

RESULTS

In the period January 1995-June 2001, RFCA of 424 tachycardia substrates was performed. A total of 217 consecutive septal tachycardia substrates are included in this report. Apnea eliminated a mean catheter tip displacement of 5.4 +/- 2.5 mm seen during respiration. No patient experienced transient or permanent complete AV block after any of the 217 substrate ablation procedures. All of the patients had normal PR intervals following ablation without development of any degree of AV block in 194 patients at latest follow-up. RFCA success for substrates with septal accessory pathways was 87/96 (91%), permanent junctional reciprocating tachycardia (PJRT) 15/16 (94%), typical atrioventricular node reentry tachycardia (AVNRT) 82/85 (96%), atypical AVNRT 6/7 (86%) and intra-atrial reentry tachycardia (IART) 10/13 (77%). Fluoroscopy time averaged 10.8 minutes. For patients with accessory pathway, 8 (7.9%) developed a recurrence.

CONCLUSION

Catheter stability is paramount to safe and effective RFCA in septal locations. Use of these techniques resulted in acceptable success rates and low recurrence rate for RFCA of septal tachycardia substrates while avoiding inadvertent AV block in these young patients.

[Indications for catheter ablation and results in Andalusia, Spain]

INTRODUCTION AND OBJECTIVES

We report the results of the first Catheter Ablation Registry of the Arrhythmia Working Group of the Andalusian Society of Cardiology (AWGASC) for 2000.

METHODS

The register includes information about the ablation procedures performed in 2000, which was collected retrospectively and submitted voluntarily by four out of six cardiac electrophysiology laboratories of the AWGASC. A total of 424 patients (mean age 45 18 years; 50% men) were included. Twelve patients underwent two different ablation procedures, bringing the total number of procedures to 436. The overall success rate (based on current criteria), success rate by procedure, in-hospital mortality, and major complications are reported.

RESULTS

The type and distribution of the ablation procedures were atrioventricular nodal re-entry tachycardia ablation, 34%; accessory pathway ablation, 39%; ventricular tachycardia ablation, 8%; atrial tachycardia ablation, 3%; atrioventricular junctional ablation, 9%, and cavo-tricuspid isthmus ablation, 9%. The overall success rate was 94% (range 97.8% to 87.4% in different laboratories), rate of major complications 1.1% (range 0% to 3.7%), and overall mortality 0.23% (1 patient).

CONCLUSIONS

These findings summarize the indications and results of catheter ablation procedures performed in 2000 at four cardiac electrophysiology laboratories in Andalusia. This is the first multicenter registry in Spain.

Flecainide and sotalol: a new combination therapy for refractory supraventricular tachycardia in children <1 year of age

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.

Radiofrequency catheter ablation in infants </=18 months old: when is it done and how do they fare?: short-term data from the pediatric ablation registry

BACKGROUND

The objective of this study was to determine the indications, the safety, and the efficacy of pediatric radiofrequency catheter ablation (RFCA) in infants.

METHODS AND RESULTS

Data from the pediatric RFCA registry were reviewed. Between August 1989 and January 1999, 137 infants, defined by age 0 to 1.5 years (median 0.7 years; weight 1.9 to 14.8 kg, median 10 kg), underwent 152 procedures in 27 of 49 registry centers (55%), compared with 5960 noninfants undergoing 6610 procedures during a comparable period. Structural heart disease was present in 36% of infants, compared with 11.2% of noninfants (P<0.0001). RFCA in infants was performed more commonly for drug resistance or life-threatening arrhythmias than in noninfants. No differences were found between infants and noninfants in success for all tachycardia substrates (87.6% versus 90.6%, P=0.11), for single accessory pathways (94.5% versus 91.5%, P=0.4), or for total (7.8% versus 7.4%, P=1) and major (4.6% versus 2.9%, P=0.17) complications. Neither success for infants with a single accessory pathway nor complications for the entire infant group were related to weight, age, center size, or the presence of structural heart disease. Centers that performed infant procedures, however, enrolled more patients overall in the registry than those that did not perform infant procedures, and successful procedures in infants were performed by more experienced physicians than failed procedures.

CONCLUSIONS

Compared with noninfants, RFCA in infants is usually performed for drug resistance or life-threatening arrhythmias, often in the presence of structural heart disease. The data support the use of RFCA by experienced physicians in selected infants.

Radiofrequency ablation in pediatric and adult patients: comparative results

BACKGROUND

Radiofrequency (RF) catheter ablation has been widely and successfully employed to cure adult and pediatric patients of a variety of arrhythmias. Only limited data exist which compare the results in these two groups. The aim of this study was to compare the efficacy and safety of RF catheter ablation in pediatric versus adult patients performed by an adult electrophysiology (EP) team.

METHODS

The study group included 327 consecutive pediatric (n=47) and adult (n=280) patients, aged 7-82 years (mean 40+/-19), with symptomatic tachyarrhythmias, who underwent RF ablation during the last 6 years. All but ten patients underwent a full EP study during the same session. Procedures were performed in all but five patients with use of local anesthesia and deep or light sedation. The left heart was approached with use of transaortic (n=36) or transseptal (n=55) or both (n=6) techniques. RF ablation was performed for manifest or concealed accessory pathways in 132 patients, AV nodal slow pathway in 119, atrial tachycardia in 24, atrial flutter in 15, atrial fibrillation in one, ventricular tachycardia in 29, and AV node/His bundle in 7 patients.

RESULTS

RF ablation was successful in 271 (96.8%) patients in the adult group and in all patients (100%) in the pediatric group, with a mean of 15+/-18 (median: 8) vs 12+/-10 (median: 8) RF applications respectively (P=NS). Complications occurred in four patients (1.4%) in the adult group and in one patient (2.1%) in the pediatric group (P=NS). Fluoroscopy time averaged 43+/-40 min vs 39+/-27 min and procedures lasted for 3.0+/-1.9 hours vs 2.8+/-1.4 hours respectively (P=NS). During long-term follow-up of 25+/-19 months, there were 12 (4.4%) recurrences among the adult patients, and three (6.4%) recurrences in children, with nine of them successfully treated with repeat RF ablation. Procedural variables were dependent on the type of arrhythmia ablated, rather than on patient's age. Patients with multiple accessory pathways or atrial flutter required the greatest number of RF applications and the longest fluoroscopy exposure and duration of the procedure; the lowest values of these variables concerned ablation of the slow AV nodal pathway or the AV node/His bundle.

CONCLUSION

RF ablation in adult and pediatric patients performed by an adult EP team is equally efficacious and safe offering cure of symptomatic cardiac tachyarrhythmias in both patient populations.

Pediatric arrhythmias

During the past decade, our awareness and understanding of arrhythmias in children has expanded immensely. This report discusses the more commonly encountered pediatric rhythm disturbances, including sinus node dysfunction, the various forms of supraventricular tachycardia, ventricular tachycardia, long QT syndrome, and the atrioventricular blocks. The electrocardiographic characteristics, electrophysiological mechanisms, clinical presentation, and current acute and chronic management options for each are described.

Evaluation and treatment of other arrhythmic causes of syncope in children and adolescents with an apparently normal heart: Wolff-Parkinson-White syndrome and right ventricular cardiomyopathy

Syncope could be a symptom of tachyarrhythmias related to the Wolff-Parkinson-White syndrome, or the consequence of the ventricular tachycardias seen in patients with Arrhythmogenic Right Ventricular Cardiomyopathy. Syncope should be considered the consequence of atrial fibrillation or flutter, with rapid conduction over the accessory atrioventricular connection in Wolff-Parkinson-White syndrome, and these patients are at risk of presenting with ventricular fibrillation and sudden death. Radiofrequency ablation of the anomalous, accessory connection, which can be performed with high success and low complication rates, should be the first line of treatment for symptomatic children and adolescents with Wolff-Parkinson-White. Arrhythmogenic Right Ventricular Cardiomyopathy is a rare disorder of the cardiac muscle affecting predominantly, although not exclusively, the right ventricle. Clinical presentation varies from asymptomatic cases to patients with severe symptoms related to life-threatening arrhythmias, right ventricular failure, or congestive heart failure with involvement of both ventricles. The clinical diagnosis is difficult. A set of major and minor criteria has been proposed to help to identify patients with this disease. Without an identified cause, the treatment of patients with Arrhythmogenic Right Ventricular Cardiomyopathy is symptomatic. Medical management of the associated congestive heart failure, pharmacologic treatment of the arrhythmias, radiofrequency ablation and implantable cardioverter-defibrillator therapy should all be considered.

[Infectious mitral endocarditis after radiofrequency catheter ablation of a left lateral accessory pathway]

A 2-years-old child with Wolff-Parkinson-White syndrome associated with life-threatening symptoms underwent radiofrequency ablation of a left lateral accessory pathway. A deflectable 5F bipolar electrode catheter positioned above the atrioventricular groove by transeptal approach was used for ablation. The catheters were repeatedly used after ethylene oxide sterilisation. Although immediate post-ablation echocardiography demonstrated no complications, the patient was readmitted two days later with fever and a new mitral murmur. Penicillin-susceptible Staphylococcus aureus was isolated and intravenous antibiotics were administered. In the following weeks, the patient developed constrictive pericarditis requiring surgical treatment and acute hemiplegia caused by brain embolism arising from valvular vegetation. At 5 years of follow-up the patient presents residual hemiparesia and grade II/IV mitral insufficiency.

Atrioventricular node reentry tachycardia in pediatric patients

Atrioventricular node reentry tachycardia (AVNRT) is a significant cause of paroxysmal supraventricular tachycardia (SVT) in the pediatric population. Symptoms can include palpitations, chest pain, fatigue, light-headedness and syncope. AVNRT is a reentry tachycardia that is comprised of dual conduction pathways through the AV node. On electrocardiogram, AVNRT usually manifests as a regular tachycardia with a narrow QRS complex and P waves that are either absent or distort the terminal portion of the QRS complex. Electrophysiology study will reveal dual AV node pathways: a fast pathway with a short AH interval and a long effective refractory period (ERP); and a slow pathway with a longer AH interval and a shorter ERP. During tachycardia, electrophysiologic signals will reveal conduction up the midline. Introduction of premature ventricular contractions and measurement of the HA interval during SVT can help distinguish AVNRT from a SVT utilizing an accessory pathway. Radiofrequency catheter ablation (RFA) has been used increasingly in children as treatment for AVNRT. The initial approach to RFA of AVNRT was modification of AV fast pathway conduction by lesions placed near the anterosuperior aspect of the triangle of Koch, known as the anterior approach method. However, this technique was associated with a significant risk of complete AV block. Now, the posterior approach slow pathway modification is used more commonly, which positions the ablation catheter along the tricuspid annulus immediately anterior to the coronary sinus ostium. This has been associated with a lower risk of complete AV block. Using this technique, RFA should be considered the method of choice for curative therapy of AVNRT in pediatric patients.

Radiofrequency catheter ablation of left-sided accessory pathways in pediatric patients

In many cases, radiofrequency catheter ablation has replaced the long-term use of antiarrhythmic medication for symptomatic tachycardia, and has all but eliminated arrhythmia surgery. The most common substrate for radiofrequency catheter ablation in pediatric patients is atrioventricular (AV) reentry tachycardia due to a concealed or manifest accessory pathway. Accessory pathways are distributed unevenly along the right and left atrioventricular valve annuli, and left-sided accessory pathways are most common. Although some centers advocate an abbreviated diagnostic and mapping approach to both concealed and manifest left-sided accessory pathways, most still use a complete electrophysiological evaluation and complex catheter manipulation for mapping, followed by the application of radiofrequency energy. Left-sided accessory pathways may be approached from the transatrial approach, the retrograde aortic approach, or less commonly from within the coronary sinus. Each approach has proven to be associated with success, but also with a distinct set of risks. Possibly because left-sided accessory pathways are most common, catheter ablation of this substrate has proven highly successful and has the lowest risk of recurrence. However, recent data also suggest that this substrate is associated with greater risk of complications than of right-sided accessory pathways or pathways located in the posteroseptal region. The following report reviews some of the recently described diagnostic and mapping techniques, success rates, risks and follow-up data in pediatric patients undergoing radiofrequency catheter ablation of left-sided accessory pathways.

Radiofrequency ablation of right-sided accessory pathways in pediatric patients

Right free-wall and septal accessory pathways encompass the full spectrum of accessory pathway electrophysiology and are situated in complex anatomical arrangements. Understanding this diversity of physiology is necessary for the successful and safe elimination of these connections with transcatheter radiofrequency ablation. When radiofrequency catheter ablation of these pathways is attempted in children, anatomical relationships often become more complex, and spatial constraints require more adaptive techniques than in adults. It is clear that considerable progress has been made with radiofrequency catheter ablation, such that it is now first-line therapy for most children who have been diagnosed with one of the broad spectrum of clinical manifestations that result from the presence of these accessory connections. This review will discuss how accessory pathway electrophysiology and anatomy impact the clinical syndromes observed in children, and how these factors, as well as others particular to children, determine the approach, results and potential long-term consequences of radiofrequency catheter ablation of right-sided accessory pathways in the pediatric population.

Complications associated with radiofrequency catheter ablation of cardiac arrhythmias

Catheter ablation using radiofrequency energy has evolved as a safe and effective means for the treatment of various supraventricular and ventricular arrhythmias. Despite the overall efficacy of radiofrequency catheter ablation, cardiovascular complications can occur in a small number of patients. The purpose of this article is to review the current understanding of the risks and complications that can occur during catheter ablation procedures.

Use of the His/RVA electrode catheter in children

Comprehensive electrophysiologic study with radiofrequency ablation requires a number of intracardiac catheters. To reduce the number of catheters placed in children, the authors evaluated a series of customized catheters that combined the functions of two catheters. The customized 6F catheter contains eight electrodes placed in pairs at 4, 5, 6, 7, or 8 cm from the tip for recording the His electrogram and at the tip for right ventricular pacing. The amplitude of the bundle of His potential recorded through the His right ventricular apex (RVA) catheter (n = 63) and the ventricular pacing threshold (in mA) (n = 48) were measured and compared to the maximal bundle of His potential recorded with a 6F hexapolar catheter in 24 and 13 other patients, respectively. The relationship between the distance from the distal electrode pair at the tip and the third electrode from the tip (the His/RVA distance) and patient size was analyzed in 42 patients. Following the initial study in the 90 patients, the selection of the optimal His/RVA catheter for 19 patients was determined by examining the regression plots derived from the first group of 90 patients. The measured His/RVA distance was then determined by noting the His/RVA distance of the catheter used. Regression analysis was then used to evaluate the fit between the predicted His/RVA distance based on weight, height, or body surface area (BSA) and the observed His/RVA distance. The maximal bundle of His electrogram measured in the two groups using the His/RVA catheter was compared. To evaluate catheter stability during the study, the amplitude of the maximal His potential was measured in the 19 patients at the onset, midpoint, and end of the study. The maximal His potential recorded through the octapolar catheter (0.21 mV) was significantly (P < .04) greater than that recorded through the hexapolar catheter (0.10 mV). The mean ventricular threshold measured through the octapolar catheter (0.44 mA) was significantly (P < .001) less than that measured through the hexapolar catheter (1.13 mA). There was a significant (P < .0001) correlation between BSA, weight, and height and the His/RVA distance. There was no significant difference in the mean maximal amplitude of the His potential (0.21 +/- 0.31 mV vs 0.15 +/- 0.12 mV) recorded through the His/RVA catheter between the two groups. The His/RVA distance estimated by weight, when plotted against the measured distance, demonstrated a good correlation (r = .84) between the expected His/RVA distance based on the subject's weight and that actually observed. In 18 of 19 subjects, the first catheter based on the patient's weight (in kilograms) predicted the appropriate and only catheter used. There was no significant difference in the mean maximal bundle of His electrogram recorded at the beginning of the study (0.15 +/- 0.12 mV), midway into the study (0.15 +/- 0.11 mV), and at the end (0.13 +/- 0.13 mV); however, there was extensive variation within individuals and over time. These data support the recording of a stable, high-quality bundle of His electrogram and RVA pacing through a single catheter system and, hence, have important, practical implications for invasive electrophysiologic studies in children.

Pediatric Cardiac Electrophysiology

The rapid development of invasive cardiac electrophysi ologic procedures, including the insertion of rate-responsive pacemakers, radiofrequency catheter ablation (RFA), and the implantation of cardiac defibrillators has given pediatric cardiac electrophysiologists better techniques to treat in fants and children with arrhythmias. Expertise on the basic pathophysiologic mechanisms of arrhythmias is a requisite in performing invasive intracardiac electrophysiologic pro cedures. Techniques for invasive cardiac electrophysiologic procedures (EPS) in pediatric patients are similar to those for diagnostic cardiac catheterization. The choice of anes thesia is determined by institutional preference, patient's age, anticipated sites of intravascular access, and type of procedure. The goal is to avoid agents that depress myocar dial contractility or affect cardiac conduction or refractori ness. EPS equipment includes multielectrode catheters, a multichannel recording system, an electrical stimulator, and a fluoroscopy unit. EPS require the ability to induce, termi nate, and modify cardiac arrhythmias. The objectives of the EPS include definition of the mechanisms of observed and induced cardiac arrhythmias, determination of risk for sudden cardiac arrhythmic death, investigation of antiar rhythmic drug efficacy, and ablation of tachyarrhythmia sub strates. This is accomplished by evaluating electrophysi ologic properties, such as automaticity, conduction, and refractoriness; by initiating and terminating tachycardias; by mapping sequence of activation; and by evaluating patients for various forms of therapy and judging the response to therapy. Though generally quite low, the associated morbid ity and mortality in performing EP study and RFA in pediatric patients varies considerably, depending on the patient's age and size, diagnosis, associated cardiac defects, and prepro cedure condition.

Idiopathic sustained left ventricular tachycardia in pediatric patients

BACKGROUND

Idiopathic sustained ventricular tachycardia originating from the left ventricle (ILVT) has been an indication for catheter ablation. The present study evaluated the clinical features, long-term prognosis and indications for treatment in pediatric patients with ILVT.

METHODS

The subjects of the present study were eight patients (four males and four females) with a mean age at onset of 11.0 years (range 3-15 years). The mean follow-up period was 7.7 years (range 2.1-11.3 years).

RESULTS

In electrophysiologic studies, intravenously administered verapamil was effective for the termination of tachycardia in all six patients who received this treatment and for the prevention of tachycardia in four of five patients. Oral administration of verapamil was effective in five of seven patients. Propranolol or flecainide was added to the treatment protocol for two patients who did not respond to verapamil alone. Tachycardia disappeared without drugs in four patients during the follow-up period and became non-sustained in another patient. Two of three patients with persistent tachycardia underwent catheter ablation. Pharmacologic treatment was very effective for ILVT among these patients.

CONCLUSIONS

Pharmacologic therapy, such as with verapamil, is still the treatment of choice for ILVT because of a good long-term prognosis and potential risks and complications by manipulation of catheter ablation.

[Clinical guidelines of the Spanish Society of Cardiology for the most frequent congenital cardiopathies]

The use of diagnostic and therapeutic techniques is very important to ensure optimum, effective treatment in patients with heart disease to thereby obtain an adequate cost-benefit relationship. The aim of establishing guidelines for the evaluation and management is to achieve this relationship, but these guidelines are difficult to establish in pediatric cardiology despite 50 years of experience in this field. At present a large group of patients may benefit from these guidelines due to the improvement in the diagnostic techniques and better treatment results in congenital heart disease in the newborn. Protocols have been established in some groups and in others in which this is not possible, descriptive analysis and therapeutic schedules have been determined.

Amiodarone is safe and highly effective therapy for supraventricular tachycardia in infants

BACKGROUND

The clinical effectiveness of amiodarone must be weighed against the likelihood of adverse effects. Adverse effects are less common in children than in adults, yet there have been no large studies assessing the efficacy and safety of amiodarone in the first 9 months of life. We sought to assess the safety and efficacy of amiodarone as primary therapy for supraventricular tachycardia in infancy.

METHODS

We evaluated the clinical course of 50 consecutive infants and neonates (1.0+/-1.5 months, 35 male) treated with amiodarone for supraventricular tachyarrhythmias between July 1994 and July 1999. At presentation, congenital heart disease, congestive heart failure, or ventricular dysfunction were present in 24%, 36%, and 44% of the infants, respectively. Infants received a 7- to 10-day load of amiodarone at either 10 or 20 mg/kg/d. If this failed to control the arrhythmia, oral propranolol (2 mg/kg/d) was added. Patients were followed up for 16.0+/-13.0 months, and antiarrhythmic drugs were discontinued as tolerated.

RESULTS

Rhythm control was achieved in all patients. Of the 34 patients who have reached 1 year of age, 23 (68%) have remained free of arrhythmia, despite discontinuation of propranolol and amiodarone. Growth and development remained normal for age. Higher loading doses of amiodarone were associated with an increase in the corrected QT interval, but no proarrhythmia was seen. There were no side effects necessitating drug withdrawal.

CONCLUSIONS

Amiodarone is an effective and safe therapy for tachycardia control in infancy.

Supraventricular Tachycardia in Children

A reasonably precise and mechanistic diagnosis of the cause of supraventricular tachycardia (SVT) can be made using noninvasive tests such as an electrocardiogram, Holter monitoring, or cardiac event recorder and by determining the response to vagal maneuvers (or intravenous adenosine). Therapy options include prophylactic drug therapy, catheter ablation, and doing nothing (for those with infrequent and non-life-threatening symptoms). Drug therapy attempts to suppress the arrhythmia rather than to cure it and could cause side effects. The success of pharmacologic treatment depends on patient compliance and is costlier than catheter ablation in the long run. Catheter ablation has a high success rate and low complication rate in patients with the common forms of SVT (Wolff-Parkinson-White syndrome, concealed accessory pathways, and atrioventricular nodal reentrant tachycardia ) and is the first choice therapy in children beyond 6 to 7 years of age. In younger patients (less than 5 years), although feasible, catheter ablation is reserved for patients with life-threatening arrhythmia or those failing drug therapy. There is a small risk of sudden death in patients with Wolff-Parkinson-White syndrome, whether symptomatic with SVT or not. Management of asymptomatic patients with Wolff-Parkinson-White syndrome is controversial. Noninvasive (Holter monitoring, exercise tests) and if necessary, invasive (electrophysiology study) assessment may help refine the risk for the individual patient.

Initial low temperature setting in radiofrequency catheter ablation of Wolff-Parkinson-White syndrome

Previous studies have shown that with low temperature testing for RF ablation of arrhythmias, unnecessary irreversible myocardial lesions may be avoided. In children admitted for RF ablation from June 1996 to May 1999, we evaluated the method of an initial temperature setting of 50 degrees C for a maximum of 10 seconds. If accessory pathway block occurred, the temperature setting was immediately increased to 70 degrees C and continued for 45-120 seconds (group 1). If accessory pathway block did not occur after several attempts, subsequent attempts were made with initial settings at 70 degrees C-80 degrees C at the same or different sites (group 2). Eighty patients with Wolff-Parkinson-White syndrome (mean age 11 +/- 4 years) were treated using this method. Twelve patients were excluded for various reasons. Of the remaining 68 patients, 52 (76%) had successful block of the pathway at 50 degrees C; 16 patients demonstrated block only at the higher temperature setting of 70 degrees C-80 degrees C. There were no statistically significant differences between these two groups in terms of age, weight, and location of accessory pathways. Unsuccessful 50 degrees C test ablation attempts were 1.6 +/- 2.4 in group 1 and 3.1 +/- 2.9 in group 2 (P = 0.04). Total unsuccessful attempts were 1.6 +/- 2.4 in group 1 and 8.1 +/- 7.1 in group 2 (P = 0.001). The time from application of RF energy to the time of AP block in group 1 was not significantly different from group 2. In the majority of children, successful RF ablation can be achieved by using a temperature setting of 50 degrees C, then 70 degrees C. This will prevent unnecessary permanent injury at unsuccessful attempt sites.

Mortality following radiofrequency catheter ablation (from the Pediatric Radiofrequency Ablation Registry). Participating members of the Pediatric Electrophysiology Society

Deaths have been reported following radiofrequency catheter ablation (RFCA), but the mortality rate in children has not been defined. This study sought to analyze the incidence and the factors associated with mortality related to RFCA. Ten of 4,651 cases (0.22%) reported to the Pediatric RFCA Registry resulting in death were reviewed and compared with a matched control group (n = 18). Death occurred in 5 of 4,092 children (0.12%, ages 0.1 to 13.3 years) with structurally normal hearts. Death was related to traumatic injury, myocardial perforation and hemopericardium, coronary or cerebral thromboembolism, and ventricular arrhythmia. All cases were left-sided (p = 0.019 vs right or septal) supraventricular arrhythmias with radiofrequency applications in the systemic atrium and/or ventricle, and all procedures were successful. Mortality occurred in 5 of 559 children (0.89%, p = 0.001 vs normals, ages 1.5 to 17.4 years) with structural heart disease. No new pathology except the mural radiofrequency lesions was seen at autopsy. Those with structurally normal hearts who died were smaller (32.7 vs 55.6 kg, p = 0.023) and had more radiofrequency applications (26.3 vs 8.7, p = 0.019) than those who survived. No differences were demonstrated for those with abnormal hearts. Operator experience was not different (deaths 103 +/- 106 vs controls 117 +/- 125, p = 0.41). Mortality associated with pediatric RFCA is rare, but is more frequent when there is underlying heart disease, lower patient weight, greater number of radiofrequency energy applications, and left-sided procedures. Operator experience does not appear to be a factor leading to mortality.

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.

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.

Congenital Heart Surgery Nomenclature and Database Project: arrhythmias

This discussion of arrhythmia terminology attempts to classify rhythm disorders for which surgical therapy may be necessary. The subject was debated and reviewed by members of the STS-Congenital Heart Surgery Database Committee and representatives from the European Association for Cardiothoracic Surgery, for the purpose of establishing a unified reporting system. Efforts were made to include all relevant nomenclature categories, using synonyms where appropriate. Extant surgical ablative procedures, detailed methods of pacemaker insertion, and AICD technology are discussed. A comprehensive database set is presented that is based on a hierarchical scheme. Data are entered at various levels of complexity and detail, which can be determined by the clinician. These data can lay the foundation for comprehensive risk stratification analyses. A minimum database set is also presented, which will allow for data sharing and will lend itself to basic interpretation of trends. Outcome tables relating diagnoses, procedures, and various risk factors are presented.

Radiofrequency catheter ablation of supraventricular tachycardia substrates after mustard and senning operations for d-transposition of the great arteries

OBJECTIVES

The purpose of this study was to determine the efficacy and risks of radiofrequency ablation of various forms of supraventricular tachycardia after Mustard and Senning operations for d-transposition of the great arteries.

BACKGROUND

In this patient group, the reported success rate of catheter ablation of intraatrial reentry tachycardia is about 70% with a negligible complication rate. There are no reports of the use of radiofrequency ablation to treat other types of supraventricular tachycardia.

METHODS

Standard diagnostic criteria were used to determine supraventricular tachycardia type. Appropriate sites for attempted ablation included 1) intraatrial reentry tachycardia: presence of concealed entrainment with a postpacing interval similar to tachycardia cycle length; 2) focal atrial tachycardia: a P-A interval < or =-20 ms; and 3) typical variety of atrioventricular (AV) node reentry tachycardia: combined electrographic and radiographic features.

RESULTS

Nine Mustard and two Senning patients underwent 13 studies to successfully ablate all supraventricular tachycardia substrates in eight (73%) patients. Eight of eleven (73%) patients having intraatrial reentry tachycardia, 3/3 having typical AV node reentry tachycardia, and 2/2 having focal atrial reentry tachycardia were successfully ablated. Among five patients having intraatrial reentry tachycardia (IART) and not having ventriculoatrial (V-A) conduction, two suffered high-grade AV block when ablation of the systemic venous portion of the medial tricuspid valve/inferior vena cava isthmus was attempted.

CONCLUSIONS

Radiofrequency catheter ablation can be effectively and safely performed for certain supraventricular tachycardia types in addition to intraatrial reentry. A novel catheter course is required for slow pathway modification. High-grade AV block is a potential risk of lesions placed in the systemic venous medial isthmus.

Successful radiofrequency ablation in an infant with drug-resistant permanent junctional reciprocating tachycardia

Over the past decade, the technique of radiofrequency ablation has evolved substantially. Currently, most forms of cardiac arrhythmias seen in children can be treated with good long-term results and low risk of adverse outcome. Curative arrhythmia treatment with this technique, however, is still uncommon in neonates and infants. Reported here is our experience in the management of an 8-week-old with drug-resistant permanent junctional reciprocating tachycardia.

Radiofrequency catheter ablation in a haemodynamically compromised premature neonate with hydrops fetalis

A preterm infant was born at 35 weeks gestation after failed antenatal antiarrhythmic therapy. The infant had an incessant supraventricular tachycardia, impaired ventricular function and hypotension and failed to respond to adenosine, cardioversion and intravenous amiodarone. After resuscitation from cardiovascular collapse, a successful radiofrequency catheter ablation (RFA) of a left free wall atrioventricular pathway was performed at 24 h of age without extracorporeal support. The infant is normal on follow up at 12 months of age. Whilst most fetal and neonatal supraventricular tachyarrhythmias respond to antiarrhythmic medications and RFA is not required, this is the earliest RFA to be performed on a premature infant when antiarrhythmics have failed.

Effect of radiofrequency catheter ablation of accessory pathways on autonomic tone in children

BACKGROUND

Radiofrequency catheter ablation is standard treatment for children with re-entrant supraventricular tachycardias. Autonomic changes have been noted after such ablation for atrioventricular nodal re-entry tachycardia, but not as well documented with atrioventricular re-entry over an accessory pathway.

METHODS AND RESULTS

In 10 normal paediatric volunteers and 12 children referred for electrophysiologic testing and radiofrequency ablation of supraventricular tachycardia, non-invasive autonomic function tests and tilt-table testing were performed, and the variability in 24-h heart rate was analysed. Patients with supraventricular tachycardia underwent these tests both 24-72 h before and 24 h after ablation. Patients with tachycardia underwent additional autonomic testing to assess the sensitivity of baroreceptors and the intrinsic heart rate with autonomic blockade immediately before and after ablation. One non-invasive autonomic function test, namely handgrip, demonstrated significant differences (p < 0.05) in diastolic blood pressure before and after ablation, though these values did not differ from controls. Significant decreases were noted in two indexes of the variability of heart rate before and after ablation (p < 0.05). Certain tilt test variables also demonstrated significant differences between controls and those with tachycardia subsequent to ablation. Intracardiac testing demonstrated changes (p < 0.05) in sinus cycle lengths, effective refractory periods and/or blood pressures at baseline and during testing of the sensitivity of baroreceptors before and after ablation. These changes were consistent with increased sympathetic or decreased parasympathetic tone. With autonomic blockade, these differences were abolished.

CONCLUSIONS

Catheter ablation of accessory pathways in children was associated with changes consistent with increased sympathetic or decreased parasympathetic tone. These autonomic changes persisted 24 h after the ablation procedure.

Low incidence of significant valvar insufficiency following retrograde aortic radiofrequency catheter ablation in young patients

The incidence of significant valvar insufficiency at late (<6 month) follow-up was retrospectively evaluated in 27 young patients (age 4. 0-18.0 years) undergoing 29 ablation procedures via the retrograde aortic approach for left-sided accessory connections in whom pre-ablation and post-ablation echocardiograms were available for review. Valvar insufficiency was graded using color flow techniques as absent, trivial, mild, moderate, or severe by blinded reviewers. Ablation was acutely successful via the retrograde approach in 25 of 29 procedures among these 27 patients. Successful ablation was ultimately achieved in all 27 patients. At baseline, 7 patients had evidence of trivial or mild mitral insufficiency, and no patient had aortic insufficiency. Three patients had evidence of impaired left ventricular systolic performance in the presence of manifest pre-excitation. At follow-up, pre-existing mitral insufficiency resolved in 5/7 patients, and persisted in 2 patients. New mitral insufficiency was evident in 3 patients, and new aortic insufficiency was transiently evident in 1 patient following ablation (all trivial). Institutional experience (mean rank 10 cases vs. 33 cases, p <.0005), and lower patient weight (29.7 vs. 56.3 kilograms, p =.01) were the only factors associated with the development of new valvar insufficiency. Valvar insufficiency could not be detected by careful auscultation in any patient and was deemed clinically insignificant in all patients. We conclude that ablation of left-sided accessory connections can be performed via the retrograde aortic approach without creating clinically significant valvar insufficiency.

Low temperature and low energy radiofrequency modification of atrioventricular nodal slow pathways in pediatric patients

OBJECTIVES

To report our experience using low temperature and energy in the modification of the slow pathway in pediatric patients with atrioventricular nodal reentrant tachycardia.

BACKGROUND

A concern in performing a slow pathway modification is the possible damage of the normal AV conduction system. Lesion size has been shown to have a linear relationship with temperature. Previous reports have used energy of 25-50 W that generate temperatures of 60 degrees C -70 degrees C for successful procedures.

METHODS

Report of results of attempted AV nodal slow pathway modification in 17 consecutive pediatric patients < 15 years of age at The Children's Hospital of Philadelphia from April 1995 to November 1997 using low temperature and energy.

RESULTS

There were 18 successful slow pathway modifications with 1 recurrence in 17 patients. The maximum energy used during successful lesions was 32.7 +/- 13.8 W (range 15-50 W) with a mean energy of 26.4 +/- 13.3 W (range 12-48 W). The peak temperature during these lesions was 55.1 degrees C +/- 4.1 degrees C (range 48 degrees C-64 degrees C) with a mean temperature of 47.9 degrees C +/- 2.7 degrees C (range 44 C-540C). The mean number of radiofrequency lesions required for a successful modification was 5.8 +/- 6.7 (median 4.0, range 1-26). Patients have been followed for 2.08 +/- 0.79 years.

CONCLUSIONS

Slow pathway modification can be performed successfully with a low incidence of recurrence in the pediatric patient using low energy and temperature. It is possible that this may lead to smaller lesions.

Electrophysiologic procedures and activation of the hemostatic system

BACKGROUND

Thromboembolism occurs in 0.4% to 2% of the subjects undergoing radiofrequency ablation (RFA), but its mechanisms remain unclear. Our aim was to evaluate several parameters of the hemostatic system in relation to the electrophysiologic procedure.

METHODS

Thirty consecutive patients were enrolled in the study. Fifteen underwent electrophysiologic study and 15 underwent radiofrequency ablation. Before the ablation procedure, all subjects were given an intravenous heparin bolus (2500 IU). Blood samples were drawn immediately before, at the end of, and 24 hours after the procedures. Spontaneous platelet aggregation in whole blood and in platelet-rich plasma, markers of clotting activation (prothrombin fragment 1+2 and the thrombin-antithrombin complex) and the fibrinolytic system (plasminogen activator inhibitor and D-dimer) levels were evaluated.

RESULTS

At the end of the procedure, spontaneous platelet aggregation in whole blood, prothrombin fragment 1+2, thrombin-antithrombin complex, and D-dimer levels increased significantly in all patients. The hemostatic changes were more marked after RFA than after electrophysiology. Spontaneous aggregation in whole blood, prothrombin fragment 1+2, and thrombin-antithrombin complex levels at 24 hours after the procedure were similar to those observed before the procedure in both groups; D -dimer levels were still elevated with respect to preprocedure levels, with a trend toward higher levels in patients undergoing RFA rather than electrophysiology. A significantly more marked activation of coagulation (prothrombin fragment 1+2, P <.005) was found in patients in whom the mean duration of energy application was higher than 23.5 seconds.

CONCLUSIONS

Our data suggest that antithrombotic prevention with a prolonged administration of heparin and/or the association of antiplatelet agents should be considered in patients undergoing RFA.

[Catheter ablation of accessory pathways in infants and children weighing less than 10 kg]

INTRODUCTION

Low weight is considered an independent risk factor for the appearance of complications in radiofrequency catheter ablation of accessory pathways in children.

OBJECTIVES

The purpose of this study was to evaluate the results and long term follow-up of radiofrequency catheter ablation in eight infants and small children of accessory pathways of less than 10 kg in weight.

METHODS AND RESULTS

There were 3 boys and 5 girls with a mean age of 6.3 +/- 5 months (range, 2.5 to 17) and an average weight of 6.2 +/- 1.9 kg (range, 3.5 to 9). The eight patients underwent a single successful ablation procedure. Five left free wall pathways were ablated by transseptal approach, two right posteroseptal pathways were ablated from the inferior vena cava and a left posteroseptal was approached from the inferior vena cava into the coronary sinus. A deflectable 5F bipolar electrode catheter with a 3 mm tip was used in the first five patients and a deflectable 5F tetrapolar catheter with a 4 mm tip and temperature monitoring using closed loop control in the 3 remaining patients. An abrupt increment in impedance due to the development of a coagulum was observed in 2 procedures. One patient developed an acute ischemic complication during ablation of a left lateral accessory pathway by transseptal approach. This patient had mild pericardial effusion after the procedure. Moderate pericardial effusion was also noted in another patient after radiofrequency ablation that resolved itself spontaneously. In the remainder of the procedures there were not complications. After a mean follow-up of 32.3 +/- 22.1 months (median 42) all patients are asymptomatic without antiarrhythmic treatment.

CONCLUSIONS

a) radiofrequency catheter ablation can be performed successfully in infants and small children weighing less than 10 kg, and b) echocardiography must be performed inmediately after the procedure in infants to investigate pericardial effusion.

[Arrhythmias in patients with congenital heart disease and their impact on prognosis]

Patients with congenital heart disease have an increased chance to suffer from brady- as well as tachyarrhythmias. The impact of these on quality of life, morbidity and mortality is more often imperative as compared to heart-healthy individuals. The substrate for these may be either congenital or acquired. Improvements of the surgical management of these patients have led, on the one hand, to improved survival rates with prolonged life expectancy within the last 2 decades, which on the other hand provided the basis for a higher rate of acquired cardiac arrhythmias. Together, this not only challenges diagnostics and therapy but also the prognostic relevance of these arrhythmias. The therapeutic strategies and prognostic markers have until now mostly been based on retrospective studies limited by the low number of patients and inhomogeneous patient selection. Despite these limitations, an increased risk of sudden cardiac death has been substantiated for certain patient groups, e.g., those operated on by the Mustard- or Senning procedures in patients with transposition of the great arteries and patients operated on with correction of the tetralogy of Fallot. However, until now it has not been possible to identify reliable markers for establishing the risk on an individual basis within these patient cohorts. For achieving reliable data on the symptomatic and prognostic effects of present-day--as well as new-coming--therapeutic strategies, it is mandatory to perform prospectively based, randomized multicenter studies. Furthermore, the well-appreciated synergism of hemodynamically and primarily of arrhythmia-based effects on prognosis could potentially be divided into their relative weight to better guide appropriate, substrate-related therapy. In addition, this should help to get better estimates of the risk for sudden cardiac death in different, etiologically homogeneous, groups of patients with congenital heart disease.

The activation of platelet function, coagulation, and fibrinolysis during radiofrequency catheter ablation in heparinized patients

INTRODUCTION

Catheter ablation may be complicated by clinical thromboembolism in about 1% of patients.

METHODS AND RESULTS

We studied the activation of coagulation (prothrombin fragment 1+2 [PF1+2]), platelets (beta-thromboglobulin [beta-TG])) and fibrinolysis (plasmin-antiplasmin complexes [PAP] and D-dimer) during radiofrequency (RF) ablation in 13 patients. They received heparin 100 U/kg intravenously after the initial electrophysiologic study, prior to the delivery of RF current; thereafter 1,000 U/hour throughout the procedure. PF1+2 increased fourfold (P < 0.001) during the diagnostic study, but gradually declined to upper reference value during heparin administration. There was a strong correlation between procedure duration prior to heparin bolus (range 39 to 173 min); and (a) the maximal rise of PF1+2 (r = 0.83, P < 0.001) and (b) the increase of PF1+2 from baseline to end of the procedure (r = 0.74, P = 0.004). There was no correlation between postheparin changes of PF1+2 and (a) postheparin procedure duration (range 40 to 317 min), (b) number of RF pulses (range 1 to 16), or (c) RF current duration (range 46 to 687 sec). Plasma beta-TG concentration showed similar trends. Fibrinolytic activity increased moderately from baseline until heparin administration; then remained around the upper reference values. PAP at the end of procedure and D-dimer at the time of heparin administration both correlated with preheparin procedure duration (r = 0.70, P = 0.007 and r = 0.69, P = 0.01, respectively). All parameters were normal the next morning.

CONCLUSION

Procedure duration prior to heparin administration, and not the delivery of RF current per se, determines activation of hemostasis and fibrinolysis during RF ablation.