Follow-up of radiofrequency catheter ablation in children: results in 100 consecutive patients

Tachycardia-Induced Cardiomyopathy in an Infant with Atrial Flutter and Prolonged Recovery of Cardiac Function

Background: Tachycardia-induced cardiomyopathy (TIC) is caused by prolonged tachycardia, leading to left ventricular dilatation and systolic dysfunction with heart failure. Although TIC is more common in adults, it is rare in early infancy. Methods: Clinical testing was performed as part of medical evaluation and management. Next-generation sequencing (NGS) was conducted for a patient with TIC. A literature review on TIC was also conducted. Results: The case involved a 5-month-old infant referred to the hospital due to symptoms of heart failure lasting at least two months. The infant's heart rate was 200 beats per minute, the left ventricular ejection fraction fell below 14%, and electrocardiograms showed atrial flutter, suggesting TIC. After cardioversion, there was no recurrence of atrial flutter, and cardiac function improved 98 days after tachycardia arrest. The NGS did not identify any pathogenic variants. The literature review identified eight early infantile cases of TIC. However, no previous reports described a case with such a prolonged duration of TIC as ours. Conclusions: This is the first report of a case of prolonged TIC in a child with the documented time to recover normal cardiac function. The improvement of cardiac function depends on the duration of TIC. Early recognition and intervention in TIC are essential to improve outcomes for infantile patients, as timely treatment offers the potential for recovery.

Catheter ablation of typical atrial flutter improves cardiac chamber size and function

INTRODUCTION

Cavo-tricuspid isthmus (CTI) dependent atrial flutter (AFL) is one of the most common atrial arrhythmias involving the right atrium (RA) for which radiofrequency catheter ablation has been widely used as a therapy of choice. However, there is limited data on the effect of this intervention on cardiac size and function.

METHODS

A retrospective study was conducted on 468 patients who underwent ablation for CTI dependent typical AFL at a single institution between 2010 and 2019. After excluding patients with congenital or rheumatic heart disease, heart transplant recipients, or those without baseline echocardiogram, a total of 130 patients were included in the analysis. Echocardiographic data were analyzed at baseline before ablation, and at early follow-up within 1-year postablation. Follow-up echocardiographic data was available for 55 patients.

RESULTS

Of the 55 patients with CTI-AFL, the mean age was 64.2 ± 14.8 years old with 14.5% (n = 8) female. The average left ventricular ejection fraction (LVEF) significantly improved on follow-up echo (40.2 ± 16.9 to 50.4 ± 14.9%, p < .0001), of which 50% of patients had an improvement in LVEF of at least 10%. There was a significant reduction in left atrial volume index (82.74 ± 28.5 to 72.96 ± 28 mL/m2 , p = .008) and RA volume index (70.62 ± 25.6 to 64.15 ± 31 mL/m2 , p = .046), and a significant improvement in left atrial reservoir strain (13.04 ± 6.8 to 19.10 ± 7.7, p < .0001).

CONCLUSIONS

Patients who underwent CTI dependent AFL ablation showed an improvement in cardiac size and function at follow-up evaluation. While long-term results are still unknown, these findings indicate that restoration of sinus rhythm in patients with typical AFL is associated with improvement in atrial size and left ventricular function.

Efficacy of radiofrequency catheter ablation for premature ventricular contractions in children

PURPOSE

This study evaluated the efficacy and safety of transcatheter radiofrequency ablation (RFCA) in treating ventricular premature contractions (PVCs) in children, summarized the countermeasures during intraoperative ventricular fibrillation (VF), and improved the safety of ventricular premature treatment.

METHODS

A retrospective analysis was conducted on 75 children with PVCs who received RFCA in the Second Affiliated Hospital of Wenzhou Medical University from January 2010 to April 2019. Data including age, sex, body weight, ejection fraction, left ventricular end diastolic diameter, burden and number of PVCs/24 h, origin of PVCs, and its complications were collected. Paired t test was used to compare changes in cardiac function before and after surgery.

RESULTS

Among the 75 cases treated with RFCA, 68 were successfully ablated, giving a success rate of 90.67%. After ablation, the left ventricular ejection fraction (LVEF) of the children was 69.13 ± 3.81%, which was significantly higher than that before surgery (69.13 ± 3.81% vs. 66.21 ± 3.22%, P = 0.012). One of the patients experienced VF during the operation, with no other complications. The initial locus of origin was the anterior septum of the right ventricular outflow tract, but VF occurred during the ablation process. Mean follow-up time was 39 ± 33 months, with two recurrent cases (2.94%).

CONCLUSIONS

Performing RFCA in children is safe and effective, with a low recurrence rate and few complications. VF is not an indication to cease surgery; the key to eliminating complications is repositioning the catheter and finding a more accurate origin point.

Development of paediatric electrophysiology standards for Florida Children's Medical Services

The Florida Children's Medical Services (CMS) has a long-standing history of ensuring that providers of multiple paediatric subspecialties abide by the highest standards. The cardiac sub-committee has written quality standard documents that participating programmes must meet or exceed. These standards oversee paediatric cardiology services including surgery, catheterisations, and outpatient services. On April, 2012, the cardiac sub-committee decided to develop similar standards in paediatric electrophysiology. A task force was created and began this process. These standards include a catalogue of required and optional equipment, as well as staff and physician credentials. We sought to establish expectations of procedural numbers by practitioner and facility. The task force surveyed the members of the Pediatric and Congenital Electrophysiology Society. Finding no consensus, the task force is committed to generate the data by requiring that the CMS participating programmes enrol and submit data to the Multicenter Pediatric and Adult Congenital EP Quality (MAP-IT™) Initiative. This manuscript details the work of the Florida CMS Paediatric Electrophysiology Task Force.

Current Management of Focal Atrial Tachycardia in Children

Background—

Focal atrial tachycardia (FAT) is an uncommon cause of supraventricular tachycardia in children. Incessant FAT can lead to tachycardia-induced cardiomyopathy. There is limited information regarding the clinical course and management of FAT. This study characterizes current management strategies for FAT in children including the prevalence of spontaneous resolution and the role of catheter ablation.

Methods and Results—

This is a retrospective chart review of pediatric patients with FAT managed between January 2000 and November 2010 at 10 pediatric centers. There were 249 patients with a median age at diagnosis of 7.2 (95% confidence interval, 5.8–10.4) years. Cardiomyopathy was observed in 28%. Resolution of FAT occurred in 89%, including spontaneous resolution without catheter ablation in 34%. Antiarrhythmic medications were used for initial therapy in 154 patients with control of FAT in 72%. Among first-line medications, β-blockers were the most common (53%) and effective (42%). Catheter ablation was successful in 80% of patients. FAT recurrence was less common with electroanatomic mapping compared with conventional mapping techniques (16% versus 35%; P =0.02). Patients were followed for a median of 2.1 (95% confidence interval, 1.8–2.6) years.

Conclusions—

FAT is managed successfully in most children. Current approaches are variable. Many patients have control of FAT with medications; however, catheter ablation is used for most patients. Spontaneous resolution is common for young children, emphasizing the role for delayed ablation in this group. Ablation is successful for all ages. Lower recurrence occurs when electroanatomic mapping techniques are used.

Radiofrequency catheter ablation therapy in the young: current status

Since 1989, when radiofrequency ablation was introduced into clinical practice for pediatric patients with supraventricular tachycardias, radiofrequency catheter ablation techniques have evolved as the treatment of choice for many forms of tachycardia in young patients. This review discusses the current status of ablation therapy for the four most common forms of supraventricular tachycardias in children, including tachycardias based on accessory atrioventricular pathways, atrioventricular nodal reentrant tachycardia, atrial ectopic tachycardia and the permanent form of junctional reciprocating tachycardia. In addition, the report will focus on the current status and limitations of ablation therapy of ventricular tachycardias and atrial reentry tachycardias in patients after surgical correction of congenital heart defects.

Radiofrequency ablation in children and adolescents: results in 154 consecutive patients

AIMS

The experience of using radiofrequency ablation (RFA) for the treatment of arrhythmias in children and adolescents is still limited. This study aimed to review the most recent results of RF ablation in children and adolescents in a highly experienced centre with access to both conventional techniques and non-fluoroscopic electroanatomic mapping (CARTO).

METHODS AND RESULTS

A total of 154 consecutive patients younger than 19 years treated with RFA during the period 2000-04 were included. Numbers (%) or median (quartiles) are reported. Age was 15 (12-17) years, 70 (45%) were males. Five patients (3%) had congenital heart disease. RFA was successful in 147/154 patients (95%). Arrhythmia recurrence occurred in 11 patients (7%). Procedure time was 55 (35-90) min and fluoroscopy time was 8.8 (4-19) min. Number of RF applications was 4 (2-10) and number of RF applications >20 s was 2 (1-7). One patient (0.7%) had complicating high-grade atrioventricular block. CARTO was used in 18 RF ablation procedures (11%) performed in 15 patients.

CONCLUSION

RF ablation can be undertaken in children and adolescents with a high success rate, few recurrences and complications, very short procedure times, and acceptable fluoroscopy times. Non-fluoroscopic electroanatomic mapping is helpful in selected patients.

Pediatric radiofrequency catheter ablation: results of initial 100 consecutive cases including congenital heart anomalies

Radiofrequency catheter ablation (RFCA) has recently become a management option for pediatric tachycardia. We reviewed the records of a total of 100 patients (aged 10 months to 19 yr) who had undergone RFCA, from March 2000 to June 2004. Types of arrhythmia (age, acute success rate) were as follows: atrioventricular reentrant tachycardia (AVRT, 9.0+/-3.7 yr, 66/67), atrioventricular nodal reentrant tachycardia (AVNRT, 13+/-2.5 yr, 16/16), ectopic atrial tachycardia (6.4+/-3.3 yr, 5/5), junctional ectopic tachycardia (10 month, 1/1), ventricular tachycardia (12+/-4.9 yr, 6/6), postsurgical intraatrial reentrant tachycardia (15.6+/-4.1 yr, 2/3), twin node tachycardia (4 yr, 0/1), and His bundle ablation (9 yr, 1/1). The age of AVNRT was older than that of AVRT (p=0.002). Associated cardiac disease was detected in 17 patients, including 6 univentricular patients, and 3 Ebstein's anomaly patients. RFCA for multiple accessory pathways required longer fluoroscopic times than did the single accessory pathway (53.9+/-4.8 vs. 36.2+/-24.1 min; p=0.03), and was associated with a higher recurrence rate (3/9 vs. 3/53; p=0.03). Regardless of the presence or absence of cardiac diseases, the overall acute success rate was 97% without major complications, the recurrence rate was 8.2%, and the final success rate was 97%. This experience confirmed the efficacy and safety of RFCA in the management of tachycardia in children.

Radiofrequency ablation for supraventricular tachycardia in children < or =15 kg is safe and effective

Risks associated with radiofrequency ablation (RFA) have been reported to be increased in children < or =15 kg. We sought to compare the safety and efficacy of RFA in children <15 kg with those between 15.1 and 20 kg. Clinical, electrophysiologic, and RFA data for all patients < or =20 kg who underwent RFA for supraventricular tachycardia between January 1994 and January 2003 were reviewed. Patients were divided into those < or =15 kg (group 1, n = 25) and those between 15.1 and 20 kg (group 2, n = 44). The two groups differed significantly in age and weight by design (group 1: mean weight, 11.9 +/- 3.0 kg; age, 2.8 +/- 1.9 years; group 2: weight, 18.0 +/- 1.5 kg; age, 5.1 +/- 1.1 years). There were no significant differences in other baseline characteristics except for incidence of structural heart disease (28% group 1 vs 7% group 2, p < 0.01). No significant differences in mechanism of tachycardia, arrhythmia cycle length, number of total and brief RFA applications, total RFA time, average and maximum RFA temperatures, total procedure duration, short-term success rate (96% group 1 vs 86% group 2, p = 0.17), long-term success rate (91% group 1 vs 89% group 2, p = 0.76), or major complications (8.0% group 1 vs 2.3% group 2, p = 0.39) were found. There were no procedure-related deaths in either group. These data suggest that, in two large volume electrophysiology centers, the procedural risks and outcomes of RFA are similar between patients weighing less than 15 kg and those between 15.1 and 20 kg.

Prospective assessment after pediatric cardiac ablation: recurrence at 1 year after initially successful ablation of supraventricular tachycardia

OBJECTIVES

A multicenter prospective study was performed to assess the results and risks associated with radiofrequency ablation in children. This report focuses on recurrences following initially successful ablation.

METHODS

Patients recruited for the study were aged 0 to 16 years and had supraventricular tachycardia due to accessory pathways or atrioventricular nodal reentrant tachycardia (AVNRT), excluding patients with more than trivial congenital heart disease. A total of 481 patients were recruited into the prospective cohort and were followed at 2, 6, and 12 months following ablation.

RESULTS

There were 517 successfully ablated substrates out of 540 attempted (95.7%). Loss to follow-up for individual substrates was 3.3%, 10.6%, and 21.2% at 2, 6, and 12 months, respectively. Recurrence was observed in 7.0%, 9.2%, and 10.7% of these substrates at 2, 6, and 12 months, respectively (adjusted for loss to follow-up as an independent source of data censoring). Recurrence rate varied by substrate location (24.6% for right septal, 15.8% for right free wall, 9.3% for left free wall, and 4.8% for left septal), as well as for AVNRT versus all others (4.8% vs 12.9%) at 12 months. The recurrence rate was higher for substrates ablated using power control but was not a function of whether isoproterenol was used for postablation testing.

CONCLUSIONS

Recurrence after initially successful ablation occurs commonly in children. It is least common after AVNRT ablation and most common following ablation of right-sided pathways. These results serve as a benchmark for the time course of recurrence following initially successful ablation of supraventricular tachycardia in children.

Permanent junctional reciprocating tachycardia in children: a multicentre study on clinical profile and outcome

OBJECTIVES

To investigate the clinical profile, natural history, and optimal management of persistent or permanent junctional reciprocating tachycardia (PJRT) in children.

METHODS AND RESULTS

85 patients meeting the ECG criteria for PJRT were enrolled in a retrospective multicentre study. Age at diagnosis varied from birth to 20 years (median 3 months). Follow up ranged from 0.1 to 26.0 (median 8.2) years. At the time of referral, 24 of 85 patients (28%) had congestive heart failure that was resolved with medical treatment in all patients. Eighty three patients received drug treatment initially. Amiodarone and verapamil were the most effective with a success rate of 84-94% alone or in association with digoxin. Radiofrequency ablation of the accessory pathway was performed in 18 patients. There was a trend for a relation between age at ablation and the result of the procedure, failures being more common in younger patients (three of six procedures in younger and 15 of 18 in older children were successful; p = 0.14). Two patients with persistent left ventricular dysfunction on echocardiography but with no symptoms of congestive heart failure died suddenly one month and three years after diagnosis. PJRT resolved spontaneously in 19 patients (22%). Age at diagnosis of PJRT was not a predictor of spontaneous resolution.

CONCLUSIONS

PJRT is a potentially lethal arrhythmia in children with tachycardia induced cardiomyopathy. Spontaneous resolution of tachycardia is not uncommon. Antiarrhythmic treatment is often effective. Radiofrequency ablation should be performed in older children or when rate is not controlled, especially in patients with persistent left ventricular dysfunction.

Prospective Assessment after Pediatric Cardiac Ablation:. Demographics, Medical Profiles, and Initial Outcomes

INTRODUCTION

A multicenter prospective study was designed and implemented to assess the short- and longer-term results and risks associated with radiofrequency (RF) ablation in children.

METHODS AND RESULTS

Patients recruited for the study were aged 0 to 16 years with supraventricular tachycardia due to accessory pathways or AV nodal reentrant tachycardia (AVNRT), excluding patients with nontrivial congenital heart disease. A national registry also was established, and contributing centers were encouraged to enroll all pediatric patients, aged 0 to 21 years, undergoing ablation at their center. This report summarizes acute results of these procedures. For analysis, subjects were divided into three groups: the prospective cohort (n = 481), cohort-eligible registry participants (n = 504), and not cohort eligible registry participants (n = 1,776). Prospectively enrolled cohort patients were similar to cohort-eligible patients in terms of demographic and other patient characteristics. Overall success rates for RF ablation were high (95.7%), with higher success rates for left-sided and particularly left free-wall pathways (97.8%) than right free-wall pathways (90.8%). Complications of both electrophysiologic study and RF ablation were infrequent (4.2% and 4.0%, respectively), and there were no deaths. AV block was uncommon overall (1.2%) and was limited to ablation in AVNRT (2.1%) and septal accessory pathways (3.0%).

CONCLUSION

Despite the multicenter and prospective design, the study demonstrates high success rates and low complication rates, which are comparable to prior single-center retrospective studies. These results may serve as the current best benchmark for expected results in the pediatric population, aged 0 to 16 years, both in terms of acute success rates and the occurrence of complications.

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.

Multiple accessory pathways in pediatric patients with Wolff-Parkinson-White syndrome

The characteristics of multiple accessory pathways in children have not been previously studied. Records were reviewed of 317 consecutive pediatric patients with Wolff-Parkinson-White syndrome who underwent electrophysiologic study and radiofrequency catheter ablation at our institution. Twenty-eight patients (9%) had multiple pathways (a total of 64 pathways: 21 patients had 2, 6 had 3, and 1 patient had 4 pathways). The locations were left free wall (22 pathways), right free wall (19 pathways), posteroseptal (17 pathways), and anteromidseptal (6 pathways). Of these 64 pathways, 55 were ablated successfully without complications, 5 failed ablation, and 4 fasciculoventricular fibers did not require treatment. Three patients had a newly found pathway at the repeat session. Three patients had atrioventricular nodal reentrant tachycardia and the slow pathway area was modified. One patient had failed initial ablation and had a successful ablation using a 3-dimensional electroanatomic mapping system. Compared with patients with a single pathway, those with multiple pathways exhibited a higher incidence of antidromic tachycardia, a shorter anterograde accessory pathway effective refractory period (<250 ms), a longer fluoroscopic time (65 +/- 43 vs 39 +/- 46 minutes, p <0.05), and a larger number of unsuccessful attempts (9 +/- 16 vs 5 +/- 8, p <0.05). Success rate (92% vs 93%) and recurrence rate (1.7% vs 2.1%) were similar in both groups. This study demonstrates that multiple pathways are not rare in pediatric patients and that multiple pathways contrast with a single pathway in a variety of conduction properties.

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.

[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.

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.

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.

Clinical and electrophysiologic evolution of the Wolff-Parkinson-White syndrome in children: impact on approaches to management

There is less certainty about the recommendations for radio-frequency ablation as a therapeutic option for Wolff-Parkinson-White syndrome in children as opposed to adults because of the different natural history and the age-related risks of ablation. To help decision-making, we evaluated the long term clinical evolution and electrophysiologic characteristics of pre-excitation in our series of children and young adults. We reviewed the clinical course of 109 patients below the age of 18 years who had been followed up over a period of 9+4 years, with a range from one to 27 years. This corresponded to 986 patient-years. We examined also the electrophysiologic data from 98 of those patients who underwent a transesophageal study. At the discovery of pre-excitation, 59% of patients were asymptomatic, while 29% developed supraventricular tachycardia during follow-up. The peak incidence of the onset of supraventricular tachycardia occurred during infancy. These patients had the highest incidence of subsequent spontaneous disappearance of the tachycardia (53%), such a favourable evolution being encountered in only 12% of patients in whom the abnormal rhythm first appeared after 12 years of age. Chronic medical treatment was required in 47% of patients, and proved completely effective in 45% of cases. The potential to induce atrial fibrillation, and the incidence pre-excitation considered to be high risk, with the shortest pre-excited RR interval equal to or less than 220 msec, was lowest in the group of patients aged less than 6 years of age, and highest in those older than 12 years of age (p <0.001). Pathways producing arrhythmia with high risk were more common in symptomatic (29%) than in asymptomatic patients (7%) (p<0.001). No mortality occurred. On the basis of our findings, we suggest that ablation should be avoided before the age of 5 or 6 years. Thereafter, the procedure should become the first line of treatment for symptomatic patients older than 12 years of age.

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.

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.

[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.

Radiofrequency ablation in older children and adolescents by an adult electrophysiology team

BACKGROUND

Radiofrequency (RF) catheter ablation has been widely and successfully employed to cure adult patients of a variety of arrhythmias. Only a few centers have a pediatric electrophysiology (EP) service available and have presented similar results in children. The aim of this study was to investigate the efficacy and safety of RF ablation in pediatric patients performed by an adult EP team.

PATIENTS AND METHODS

The study group included 33 consecutive pediatric patients, aged 7-18 years (mean 14.1 +/- 3.1), with symptomatic supraventricular tachyarrhythmias, who underwent RF ablation during the last 3 years. All but two 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 = 3) or transseptal (n = 7) techniques. RF ablation was performed for manifest (n = 11) or concealed (n = 9) (9 left, 4 anteroseptal, 3 midseptal, and 4 posteroseptal) or right atriofascicular (Mahaim) (n = 1) accessory pathways in 19 patients, 12 slow AV nodal pathways and 2 atrial tachycardia foci in the other 14 patients.

RESULTS

RF ablation was successful in all patients (100%) with 1-27 RF applications (mean: 10 +/- 7). There was one complication in a patient with 2 accessory pathways; after RF ablation of a posteroseptal accessory pathway, complete heart block occurred during successful ablation of a second midseptal accessory pathway. Fluoroscopy time averaged 35 +/- 23 min and procedure duration 2.8 +/- 1.4 hours. During long-term follow-up of 19 +/- 10 months, there was one AV nodal tachycardia recurrence at 2.5 months, successfully treated with repeat RF ablation.

CONCLUSION

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

Controlled ventilation enhances catheter stability during radiofrequency ablation

Variations in the amplitude of the atrial and ventricular depolarization waves of the intracardiac electrogram occur during different phases of respiration. Therefore, we tested whether controlled ventilation would reduce ablation attempts and increase the rate of success in patients undergoing radiofrequency ablation with general anesthesia. Thirty-eight children were divided into two groups: (1) controlled and (2) noncontrolled or cyclic ventilation. In the controlled ventilation group, the mapping electrogram was recorded during sustained inspiration, sustained expiration, and cyclic ventilation. Ablation was done in the phase of ventilation that had the least variability in atrial and ventricular amplitudes. Seventeen patients in the controlled ventilation group had tracings adequate for review. In eight patients, ablation was done during sustained inspiration with the percentage change of atrial and ventricular amplitudes (15% +/- 16% and 13% +/- 16%, respectively) being < that during sustained expiration (38% +/- 27%, P = 0.04 and 20% +/- 21%) or during cyclic ventilation (57% +/- 27%, P < 0.01 and 54% +/- 26%, P = 0.003). In nine patients, ablation was done during sustained expiration with the percentage change of atrial and ventricular amplitudes (5% +/- 5% and 5% +/- 2%) being less than that during sustained inspiration (21% +/- 14%, P = 0.01 and 11% +/- 6%, P = 0.01) or during cyclic ventilation (68% +/- 23%, P < 0.001 and 48 +/- 26%, P = 0.001). We achieved success with each patient in both groups, but the number of ablation attempts were less in the controlled ventilation group 1 (3 +/- 2), as compared to the cyclic ventilation group 2 (8 +/- 8; P < 0.02). We concluded that controlled ventilation reduced the number of ablation attempts and facilitated the ablation procedure.

Right coronary artery occlusion as a complication of accessory pathway ablation in a 12-year-old treated with stenting

We describe a complication of radiofrequency ablation of a posteroseptal pathway that resulted in acute occlusion of a distal right coronary artery in a pediatric patient. The complication was treated with coronary stenting after unsuccessful angioplasty.

[Coronary ischemia during radiofrequency ablation of left lateral accessory pathway in an infant]

Acute coronary ischaemic complications are uncommon following catheter ablation of accessory pathways. Only isolated cases have been previously reported in adult patients during ablation of left free-wall accessory pathways by retrograde or anterograde approach. We report a transient ischaemic complication after catheter ablation of a left free wall accessory pathway by transseptal approach in an infant.

Five-year experience with radiofrequency catheter ablation: implications for management of arrhythmias in pediatric and young adult patients

OBJECTIVE

A review of the results of the first 5 years of radiofrequency catheter ablation procedures performed at Children's Hospital, Boston, a large tertiary referral center for patients with congenital heart disease and arrhythmias common to the infant, child, and young adult.

STUDY DESIGN

A retrospective review of 410 consecutive procedures in 346 patients who underwent at least one application of radiofrequency energy for the treatment of recurrent supraventricular or ventricular tachycardia.

RESULTS

The overall final success rate for all diagnoses was 90%, with a higher success rate in patients with an accessory pathway (96%). During the 5-year study period, the success rate improved while the rates of failures and late recurrences declined. The incidence of serious complications was 1.2% (1 late death, 1 ventricular dysfunction, 1 complete heart block, 1 cardiac perforation, and 1 cerebrovascular accident).

CONCLUSIONS

This report of a large series of radiofrequency catheter ablation procedures performed at an institution committed to treating congenital heart disease and pediatric arrhythmias confirms the safety and efficacy of this procedure. The pediatric cardiologist/electrophysiologist treating such patients must be aware of specific technical, anatomic, and electrophysiologic variations in the pediatric patient that are critical to the success of this therapy.

Radiofrequency catheter ablation of accessory pathways in infants

OBJECTIVE

To evaluate the indications, results and complications of radiofrequency catheter ablation in small infants with supraventricular tachycardia due to an accessory atrioventricular pathway.

METHODS

Five infants less than 9 months old underwent radiofrequency catheter ablation of accessory pathways. Ablation was done for medically refractory tachyarrhythmia associated with aborted sudden death in two patients, left ventricular dysfunction in one, failure of antiarrhythmic drugs in one, and planned cardiac surgery in one. All five patients underwent a single successful procedure. Three left free wall pathways were ablated by transseptal approach, a right posteroseptal pathway was ablated from the inferior vena cava, and a left posteroseptal pathway was approached from the inferior vena cava into the coronary sinus. A deflectable 5F bipolar electrode catheter with a 3 mm tip was used.

RESULTS

A sudden increment in impedance indicative of coagulum formation was observed in two procedures. One patient developed a transient ischaemic complication after 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 a mean follow up of 18.4 months all patients are symptom free without treatment.

CONCLUSIONS

Radiofrequency catheter ablation can be performed successfully in infants. Temperature monitoring in 5F ablation catheters would be desirable to prevent the development of coagulum. Echocardiography must be performed after the ablation procedure to investigate pericardial effusion.

Acute radiodermatitis after radiofrequency catheter ablation

Radiofrequency (RF) catheter ablation is used in the treatment of a variety of arrhythmias. This report describes the development of acute radiodermatitis after two prolonged RF catheter ablation procedures for supraventricular tachycardia. It also reviews the characteristics and treatment of radiation-induced skin reactions.

Radiofrequency ablation in children

Radiofrequency (RF) catheter ablation has ushered in a new era in the management of patients with symptomatic tachyarrhythmias. By providing the ability to cure the underlying arrhythmic substrate, RF catheter ablation obviates the need for life-long antiarrhythmic drugs. In the reported series, the success has been high and the complications have been infrequent and relatively minor. Not unexpectedly, RF catheter ablation has become the treatment of choice for patients with symptomatic paroxysmal tachyarrhythmias. The role of radiofrequency catheter ablation in infants and small children remains controversial, and awaits a larger experience and longer follow-up data.

Lack of proarrhythmia as assessed by Holter monitor after atrial radiofrequency ablation of supraventricular tachycardia in children

The purpose of this study was to assess the short-term arrhythmogenicity of atrial radiofrequency (RF) ablation lesions in children. Patients with the greatest exposure to RF energy comprised the study group. Holter data on 35 RF ablation procedures in 31 patients with a median age of 13.2 years (range 3 months to 20 years) was retrospectively analyzed. Patients received an average of 19.9 (SD = 13.6) RF lesions, all delivered by an atrial approach. Supraventricular ectopy and ventricular ectopy were compared immediately before and after and 4 to 9 weeks after RF ablation by serial Holter monitoring. Factors thought to possibly predispose patients to a proarrhythmic effect were used to define subgroups for separate analysis. No increase in ambient supraventricular ectopy or ventricular ectopy was observed either immediately after or 4 to 9 weeks after RF ablation compared with the baseline Holter recordings. Children exposed to relatively large doses of RF energy may demonstrate transient and asymptomatic nonsustained tachycardias in the short term. However, no new sustained tachycardias and no increase in supraventricular or ventricular ambient ectopy are detected by short-term Holter monitoring.

Mapping and radiofrequency ablation of intraatrial reentrant tachycardia after the Senning or Mustard procedure for transposition ofthe great arteries

The Senning and Mustard procedures are often associated with the development of atrial tachyarrhythmias, which may be a cause of sudden death. We hypothesized that atrial surgery creates barriers to impulse propagation, establishing potential routes for atrial reentry, and that mapping combined with knowledge of the surgical anatomy could identify zones that are critical to the tachycardia to be targeted for radiofrequency catheter ablation. Patients underwent mapping to identify early sites of atrial activation that were related to anatomic or surgically created obstacles, with confirmation by pacing to demonstrate concealed entrainment. Radiofrequency lesions were placed to connect these obstacles, while observing for tachycardia termination. Thirteen tachycardias were attempted in 10 patients, 10 successfully. Three patients had 2 distinct tachycardias. Successful sites were in right atrial tissue, although in many, a retrograde approach to the pulmonary venous atrium was necessary. Ablation of the clinically documented tachycardia was successful in 9 of 10 patients. The most common successful site was the region of the coronary sinus mouth, approached antegrade or retrograde. Ablation of intraatrial reentrant tachycardias after the Senning or Mustard procedure is feasible using concealed entrainment mapping techniques, but requires a detailed knowledge of the individual surgical anatomy and the ability to approach the pulmonary venous atrium. Radiofrequency ablation offers significant advantages over other management modalities in this patient group.

Learning curve for radiofrequency catheter ablation in pediatrics at a single institution

We examined the learning curve for radiofrequency ablation in pediatrics at a single institution. The first 146 cases were retrospectively reviewed, including patients < or = 21 years old with a single tachycardia diagnosis who were undergoing radiofrequency ablation for the first time. Data regarding demographics, electrophysiologic properties of the tachycardia, and procedural characteristics were tabulated. Data were then analyzed for evidence of association between these characteristics, success, and experience. Results revealed that success rates improved significantly with experience, reaching 85% success for all cases after < 100 cases attempted. Success for accessory pathway tachycardias alone reached > 93%. The number of cases of nonpathway tachycardias undertaken significantly increased as experience was gained. Fluoroscopy time improved to 34 +/- 27 minutes after < 100 cases. In conclusion, as experience was gained, (1) success rates showed a steep improvement; (2) the population undergoing radiofrequency ablation clearly shifted to include more difficult diagnoses; and (3) fluoroscopy time significantly decreased.

Radiofrequency ablation for supraventricular and ventricular tachycardia in young patients

Radiofrequency ablation therapy was conducted in 86 consecutive children and young patients with a mean age of 14 +/- 3 years (range = 3-18). Fifty-two patients had Wolff-Parkinson-White syndrome, one had re-entry tachycardia incorporating a nodoventricular fiber, 22 had atrioventricular node re-entry tachycardia, two had atrial tachycardia and nine had idiopathic ventricular tachycardia. Radiofrequency ablation was successful in 50 of the 52 patients (96%) with Wolff-Parkinson-White syndrome and the one with nodoventricular fiber. Radiofrequency modification of the atrioventricular node using the inferior approach was successful in eliminating atrioventricular node re-entry tachycardia in 20 of the 22 patients (91%). Radiofrequency ablation in the two patients with atrial tachycardia was unsuccessful. Of the nine patients with idiopathic ventricular tachycardia, eight from the left ventricle and one from the right ventricular outflow tract, eight were successfully ablated (88%). Follow-up over a period ranging from 1 to 46 months (21 +/- 13) revealed a recurrence of tachycardia in seven patients; a late electrophysiological study in 38 patients revealed the induction of tachycardia in 11 patients (seven with accessory pathway-mediated tachycardia, three with atrioventricular node re-entry tachycardia and one with idiopathic ventricular tachycardia). All 11 patients were successfully ablated by a second trial. In conclusion, radiofrequency ablation therapy is effective and safe in pediatric patients with supraventricular and ventricular tachycardia and should be considered as the therapy of choice in this group of patients.

Radiofrequency catheter ablation of right ventricular outflow tachycardia in children and adolescents

OBJECTIVES

The current study reviews the safety and efficacy of radiofrequency catheter ablation for the treatment of right ventricular outflow tachycardia in children and adolescents and describes a modified method for mapping the tachycardia focus.

BACKGROUND

Although radiofrequency catheter ablation has proved highly effective for the treatment of supraventricular tachycardia during childhood and adolescence, its application in children with idiopathic right ventricular outflow tachycardia has been limited.

METHODS

Six children (mean [+/- SD] age 10.6 +/- 2.4 years, range 6 to 16) with right ventricular outflow tachycardia underwent seven radiofrequency catheter ablation procedures. The mean tachycardia cycle length was 323 +/- 24 ms (range 300 to 360). Two multipolar catheters were positioned in the right ventricular outflow tract to map the tachycardia focus.

RESULTS

Radiofrequency catheter ablation was successful in five (83%) of the six children (95% confidence interval 36% to 99%). At successful ablation sites, local endocardial activation time preceded the surface QRS onset by 46 +/- 5 ms (range 37 to 57), and there was concordance of the 12-lead pace map and the electrocardiogram (ECG) in 11 (one patient) to 12 ECG leads (four patients). One patient developed complete right bundle branch block during radiofrequency catheter ablation. There were no additional complications and no clinical recurrences over a mean follow-up period of 12.7 +/- 3.8 months (range 9 to 22).

CONCLUSIONS

These results suggest that radiofrequency catheter ablation is a safe and effective treatment for right ventricular outflow tachycardia during childhood and adolescence. In addition, tachycardia mapping may be enhanced by use of a multipolar right ventricular outflow catheter technique.

Reversibility of tachycardia-induced cardiomyopathy after radiofrequency ablation of incessant supraventricular tachycardia in infants

Tachycardia-induced cardiomyopathy developed in a 3 month old infant with permanent junctional reciprocating tachycardia, which was incessant despite medical treatment. The patient underwent transcatheter radiofrequency ablation. There were no complications and 8 months after the procedure the patient was symptom free without medication.

Supraventricular tachyarrhythmias. Pharmacologic versus nonpharmacologic approaches

Nonpharmacologic approaches to the long-term management of SVTs have evolved rapidly and now offer to patients a safe, effective alternative for symptomatic relief from many SVTs. By far, radiofrequency catheter ablation, a technology less than 10 years old, offers the least invasive and most cost-effective nonpharmacologic alternative for many SVTs. Knowledge gained through electrophysiologic and ablation studies has enlarged the understanding of SVTs and may enable electrophysiologists to approach the more common and morbid condition of atrial fibrillation. From a societal standpoint, catheter ablation can remain a cost-effective mode of treatment if patient selection is stringent. The next 10 years should see further refinement in technique and in understanding of SVTs, improved technology, and enlarging applications of radiofrequency energy to cure or modify cardiac arrhythmias.

Clinical anatomy of the atrioventricular junctions

OBJECTIVES

This study reevaluated the anatomy of the areas anterior and posterior to the atrioventricular (AV) septal structures, previously said to represent anterior and posterior septal areas.

BACKGROUND

In descriptions of the locations of accessory AV pathways within the AV junctions, four regions have been recognized: the left and right free walls and the anterior and posterior septums. On the basis of known facts concerning cardiac structure, it is questionable whether these so-called septums are truly septal.

METHODS

Ten human hearts were dissected to elucidate the clinical anatomy of these purportedly septal regions, together with the overall arrangement of the AV junctions.

RESULTS

The true septal components of the AV junctions are the muscular and membranous AV septal areas. These separate the cavity of the right atrium from that of the left ventricle. The region previously designated as the anterior septum is part of the right parietal junction. It is contiguous with the membranous part of the septum but extends anteriorly and laterally from the septum as part of the supraventricular crest of the right ventricle ("crista supraventricularis"). In the region posterior to and beneath the mouth of the coronary sinus, only the most anterior extent, in continuity with the central fibrous body, is part of the muscular AV septum. The posterior extent of this area roofs over the diverging right and left ventricular walls and is filled in with fibroareolar tissue of the AV groove.

CONCLUSIONS

The larger part of the regions anterior and posterior to the true AV septal areas are not septal but are parts of the parietal AV junctions. An understanding of these anatomic relations is essential for those wishing to modify conduction across the AV junctions.