Comparison of transesophageal and intracardiac electrophysiologic studies in characterization of supraventricular tachycardia in pediatric patients

Is transesophageal electrophysiologic study valuable in children with successful radiofrequency ablation of supraventricular tachycardia on follow-up for recurrence?

Objective:

The aim of this study was to evaluate the efficacy of transesophageal electrophysiologic study (TEEPS) for the determination of supraventricular tachycardia (SVT) recurrences in symptomatic and asymptomatic children after successful radiofrequency ablation (RFA) for SVT.

Methods:

A total of 66 patients who underwent TEEPS after successful RFA were included. The demographic features, symptoms of the patients, and the characteristics of the recurrences induced by TEEPS were evaluated. The arrhythmia types induced during RFA were compared with those induced by TEEPS in terms of the compatibility of the diagnosis.

Results:

Forty-two (63.6%) girls and 24 (36.4%) boys with a mean age of 11.8±3.4 years were followed-up for 44.1±15.7 months. The average time between RFA and TEEPS was 5.2±5.9 months. The diagnoses during RFA were atrioventricular nodal reentrant tachycardia (AVNRT) in 47 of 66 patients, atrioventricular reentrant tachycardia (AVRT) in 18 of 66 patients, and ectopic atrial tachycardia in 1 of 66 patients. SVT was induced by TEEPS in 2 of 25 symptomatic and 5 of 41 asymptomatic patients. The SVT inducibility rate was 5.5% (1/18) and 12.7% (6/47) in patients with AVRT and AVNRT, respectively. In addition, 85.7% (6/7) of all recurrences occurred within 3.5 months. The recurrences as AVNRT in 2 of 25 symptomatic patients occurred in the first month after RFA. AVNRT in 4 of 41 and AVRT in 1 of 41 asymptomatic patients were induced within 3.5 months and 15 months, respectively.

Conclusion:

TEEPS seems to be a valuable screening and diagnostic method for the determination of recurrence in symptomatic and asymptomatic children who underwent successful RFA.

Comparison of Transesophageal and Intracardiac Electrophysiologic Studies for the Diagnosis of Childhood Supraventricular Tachycardias

In this study, we aimed to compare the results of transesophageal electrophysiologic studies (TEEPS) and intracardiac electrophysiologic studies (IEPS) in a cohort of pediatric patients with SVTs. The medical records of children aged between 0 and 18 years who underwent TEEPS between January 2007 and June 2012 were systematically reviewed, and those without pre-excitation and who underwent subsequent IEPS were identified. Post-procedural diagnoses were compared for compatibility. A total of 162 patients were included in the study with a mean age at diagnosis 11.6 ± 3.6 years. Tachycardia was induced in 152 patients by TEEPS and in 154 patients by IEPS. Overall, in 147 patients, tachycardia was induced by both TEEPS and IEPS. Diagnoses were compatible in 135 out of 147 patients (91.8 %). Nine out of the 12 patients with discrepant results were diagnosed with atrioventricular-reentrant tachycardia (AVRT) and three with atrioventricular nodal reentrant tachycardia (AVNRT) after TEEPS. Following IEPS, TEEPS diagnosis of AVRT was revised to typical AVNRT in 5 patients and atypical AVNRT in 4 patients. Two of the 3 patients who were diagnosed as having AVNRT following TEEPS were confirmed to have atrial tachycardia after IEPS, while the other patient was diagnosed with AVRT. Tachycardia terminated spontaneously in 3 patients, while overdrive pacing was attempted to terminate the tachycardia in 149 patients, with a success rate of 93.2 % (139/149). The diagnostic compatibility between TEEPS and IEPS is quite high. A diagnostic discrepancy mostly occurs in patients diagnosed with AVRT by TEEPS, and the possibility of atypical AVNRT should be considered in patients with a VA ≥70 ms to avoid such discrepancies.

Factors of negativity of electrophysiological study in children and teenagers complaining of tachycardia and prognostic significance

When non-invasive studies remain negative, the diagnosis of unexplained tachycardia in the young is a dilemma. The purpose of the study was to determine the factors of negativity of transesophageal electrophysiological study (EPS) in children/teenagers complaining of tachycardia and the prognostic value. Two hundred and seventy-three children with a normal ECG in sinus rhythm, aged from 6 to 19 years (15 ± 3), complained of tachycardia. Transesophageal EPS consisted of atrial stimulation in control state and after isoproterenol. Supraventricular tachycardia (SVT) was induced in 149 patients (group I) and EPS remained negative in 124 (group II). Age did not differ (15 ± 3 vs 15 ± 3). Female gender and familial history of SVT were as frequent in group I (47, 11%) than in group II (55%, p = 0.15; 7%;p = 0.2). Feeling of dizziness/syncope with tachycardia was less frequent in group I (12%) than in group II (48%) (p < 0.0001). Feeling of chest pain with tachycardia was less frequent in group I (2%) than in group II (28%) (p < 0.0001). The presence of non-cardiac disease was less frequent in group I (1.3%) than in group II (6.4%) (p < 0.025). Patients with negative study remained free of SVT after a follow-up of 3.5 ± 3 years, but one had a complete AV block. In children with apparently normal ECG in sinus rhythm, who complained of tachycardia clinical history (association with syncope, chest pain, or the presence of another disease) can predict negativity of EPS with a relatively high accuracy; EPS may not be necessary. In very symptomatic patients, transesophageal EPS, which is inexpensive and non-invasive, might be performed to stop investigations.

Sensitivity of transesophageal electrophysiologic study in children with supraventricular tachycardia on electrocardiography

INTRODUCTION

The aim of this study was to evaluate the inducibility of tachycardia by transesophageal electrophysiologic study (TEEPS) in patients with documented supraventricular tachycardia (SVT) on electrocardiography and to investigate the accuracy of TEEPS records by comparing with intracardiac electrophysiologic study (IEPS).

MATERIAL AND METHODS

The TEEPS records of patients having documented electrocardiography during SVT were reviewed. The results of TEEPS in 43 of 85 patients were compared with results of IEPS for compatibility of diagnosis.

RESULTS

A total 85 patients, 46 male and 39 female, mean weight 35.1 kg (36-87), aged 1 month-17 years, were included. Tachycardia was induced by TEEPS in 79 of 85 patients with documented electrocardiography (sensitivity 92.9%). IEPS for diagnosis or ablation was conducted in 40 patients having inducible tachycardia and three of six who had no inducible tachycardia by TEEPS. Tachycardia was induced by IEPS in 39 of 40 (97.5%) patients who had inducible tachycardia and two of three who had no inducible tachycardia by TEEPS. Mechanisms of tachycardias were similar in 97.5% of patients (37/39) who had inducible tachycardia in TEEPS and IEPS. One of the patients with atrioventricular reentry tachycardia by TEEPS was diagnosed as atrioventricular nodal reentry tachycardia (AVNRT) and the other one was diagnosed as atypical AVNRT and atrial tachycardia by IEPS.

CONCLUSION

The rates of inducibility and mechanisms of tachycardias by TEEPS in children having documented SVT were similar with those obtained from IEPS.

Prevalence, causes of reappearance of symptoms or preexcitation syndrome after ablation of accessory pathway and management

AIM

The purpose of the study was to look for the prevalence, significance and management of preexcitation syndrome (PS) or symptoms reappearance after accessory pathway (AP) ablation. AP ablation actually is the first treatment of PS.

METHODS

Successful AP ablation was performed in 261 patients; reappearance of symptoms or PS on ECG occurred in 47 patients (18%) from 20minutes to several years. Their data were compared with remaining patients.

RESULTS

Recurrences were more frequent in patients with spontaneous malignant form (34 vs. 21%), in congenital heart disease (4.2 vs. 0%) (P<0.002), in case of complication (11 vs. 2%) (P<0.007) and of a longer duration of applications (304±209 vs. 188±182sec) (P<0.019). Forty percent of patients had the same symptoms and electrophysiological data as before ablation. Twenty-four percent had an improvement of symptoms and/or electrophysiological data. However, 3 initially asymptomatic patients became symptomatic after ablation. Twenty-six percent had another AP or another rhythm disorder. We recommend transesophageal electrophysiological study for the control because only 40% of patients required second ablation.

CONCLUSIONS

Reappearance of symptoms or a PS on ECG after AP ablation was not rare (18%) and was inconsistently associated with the reappearance of all initial AP electrophysiological properties. Only 40% of patients required a second AP ablation. Another arrhythmia was possible. Non-invasive second evaluation should be preferred. However, asymptomatic patients before ablation could become symptomatic.

Impact of transesophageal electrophysiologic study to elucidate the mechanism of arrhythmia on children with supraventricular tachycardia and no preexcitation

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

Age-related prognosis of syncope associated with a preexcitation syndrome

BACKGROUND

Syncope in Wolff-Parkinson-White syndrome (WPW) is without relationship with WPW or reveals a poorly tolerated arrhythmia. Electrophysiologic study (EPS) is recommended. The purpose of the study was to evaluate the influence of the patient's age on the causes and prognosis of syncope.

METHODS

A total of 98 patients, mean age 35 ± 18 years, with WPW were admitted for syncope. Note that 29 were aged between 9 and 19 years (mean 15 ± 3) (children and teenagers/group I), 45 between 20 and 49 years (mean 34 ± 8) (adults/group II), and 24 between 50 and 70 years (mean 60 ± 8) (elderly/group III). EPS consisted of atrial pacing and programmed atrial stimulation in control state and after isoproterenol.

RESULTS

Potentially malignant form (rapid conduction in accessory pathway >240 beats/min in control state or >300 beats/min after isoproterenol and atrial fibrillation [AF] induction) was more frequent in group I (34%) than in groups II (7%) (P < 0.002) and III (0%) (P < 0.001). Orthodromic atrioventricular reentrant tachycardia (AVRT) and AF were induced as frequently in groups I (59, 34%), II (47, 15.5%), and III (54, 17%). AVRT was induced in all but one patient with malignant form. EPS was as frequently negative in groups I (27.5%), II (44%), and III (37.5%). Natural follow-up (mean 8 ± 6 years) indicated a favorable prognosis, only related to AVRT induction. Induced AF was without significance.

CONCLUSIONS

Data in syncope and WPW syndrome depended on age: electrophysiological malignant form was frequent in children/teenagers, rare in adults, and absent in elderly. AVRT, the main cause of syncope, was as frequent in all ranges of age. AF's induction alone had no significance. Final prognosis was favorable.

Transesophageal evaluation of asymptomatic Wolff-Parkinson-White syndrome

BACKGROUND

Risk stratification for Wolff-Parkinson-White (WPW) by intracardiac electrophysiology study (ICEPS) carries risks related to catheterization. We describe an alternative approach by using transesophageal electrophysiology study (TEEPS).

METHODS

The pediatric electrophysiology database was reviewed for patients with WPW and no documented clinical supraventricular tachycardia (SVT) who underwent risk stratification by TEEPS from October 2005 to November 2010. Of those who underwent subsequent ICEPS, only those with data available to compare accessory pathway (AP) conduction during ICEPS and TEEPS were included.

RESULTS

Of 65 patients who underwent TEEPS, 42 were found to have an indication for ablation. The most common indication for ICEPS was inducible SVT, which was induced in 67% of patients. Of 42 patients who underwent subsequent ICEPS, 23 had sufficient data for comparison of AP conduction between ICEPS and TEEPS. There was no difference between the baseline minimum 1:1 antegrade conduction through the accessory pathway found at TEEPS versus ICEPS (312 ± 51 ms vs 316 ± 66 ms, P = 0.5). There was no significant difference between the baseline antegrade AP-effective refractory period found at TEEPS versus ICEPS (308 ± 34 ms vs 297 ± 37 ms, P = 0.07). There were no complications related to TEEPS or ICEPS.

CONCLUSION

TEEPS is a safe and feasible alternative to ICEPS for risk stratification in patients with asymptomatic WPW and should be considered before ICEPS and ablation.

Transesophageal electrophysiological evaluation of children with a history of supraventricular tachycardia in infancy

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

Transesophageal electrophysiologic study to determine the inducibility after successful ablation of supraventricular tachycardia in children

BACKGROUND

Radiofrequency ablation has become first-line therapy for supraventricular tachycardia in all age groups, but there has been a concern regarding the long-term effectiveness of the procedure in children. This study aimed to determine the inducibility after successful ablation of supraventricular tachycardia in children; assessment was performed using a transesophageal electrophysiologic study.

RESULTS

A total of 63 patients who had been treated successfully for supraventricular tachycardia with radiofrequency ablation were included in the study. A transesophageal electrophysiologic study was performed 2 months after radiofrequency ablation. Tachycardia was induced in nine of 34 symptomatic and five of 29 asymptomatic patients by a transesophageal electrophysiologic study. Ten patients had recurrence of the same type of supraventricular tachycardia seen previously, and two had a new type of arrhythmia during a transesophageal electrophysiologic study. Tachycardia inducibility rate was 16% in all patients, 22.8% in patients with atrioventricular reentrant tachycardia, and 8% in patients with atrioventricular nodal reentrant tachycardia.

CONCLUSION

Radiofrequency ablation is a safe and effective method to manage children with supraventricular tachycardia, but patients must be observed for recurrence and new arrhythmias. Sustained tachycardia may also be induced in asymptomatic patients. A transesophageal electrophysiologic study is effective and safe for follow-up of radiofrequency ablation for assessment, diagnosis, and treatment of patients.

[Transesophageal electrophysiological study in non sedated children younger than 11 years with a Wolff-Parkinson-White syndrome]

The electrophysiological evaluation of Wolff-Parkinson-White syndrome (WPW) is recommended in children aged more than five years to detect a risk of life-threatening arrhythmia. The purposes of the study were to determine the feasibility of transesophageal EPS in a child between six and 10 years in out-patient clinic.

METHODS

Electrophysiological study (EPS) was indicated in 22 children, aged six to 10 years, with a manifest WPW either for no documented tachycardia (n=7), unexplained dizziness (n=2) or for a sportive authorization in 10 asymptomatic children. Two of the last children had a history of permanent tachycardia after the birth but were asymptomatic since the age of one year without drugs.

RESULTS

EPS was performed in all children. The main difficulty lied in passing the catheter through the mouth. Programmed stimulation at cycle length of 380 ms was performed in all children to avoid high rates of pacing when the conduction through the accessory pathway (AP) and normal AV system was evaluated. Isoproterenol was not required in five children, because they developed a catecholaminergic sinus tachycardia. The AP refractory period was determined in all children between 200 and 270 ms. Orthodromic reentrant tachycardia (RT) was induced in 11 children, three asymptomatic children (27%), seven complaining of tachycardia and one with syncope. Rapid antidromic tachycardia was induced in this last child with dizziness. Atrial fibrillation was never induced.

CONCLUSIONS

Esophageal EPS can be performed without sedation in a young child six to 10-year-old with a shortened protocol of stimulation, which was capable to clearly evaluate the WPW-related risks.

Clinical and electrophysiological characteristics, and relatively benign outcome, of typical atrioventricular nodal reentrant tachycardia in children and adolescents

BACKGROUND

Atrioventricular nodal re-entrant tachycardia is an uncommon arrhythmia in children. The natural history of this disturbance is poorly known in young patients.

METHODS

We analyzed the clinical and electrophysiological features, and the final outcome, in 19 children affected by typical atrioventricular nodal re-entrant tachycardia diagnosed by a transoesophageal electrophysiological study.

RESULTS

Of the cohort, 12 patients were female and 7 male, with a mean age of 11 years. Dual atrioventricular nodal physiology was demonstrated in 14 children (73%). The mean length of the tachycardia cycle was 297 milliseconds, with periods of 2 to 1 atrioventricular block during tachycardia noted in 5 children (26%). The mean cycle length was significantly shorter in the children who presented episodes of 2 to 1 atrioventricular block than in those who did not. After diagnosis, 12 children were not treated, 6 were treated with medical therapy, and 1 was submitted to radiofrequency transcatheter ablation. During a mean follow-up period of 41 months, 2 children with rare, but sustained, episodes of tachycardia that initially had not been treated were submitted to radiofrequency transcatheter ablation. Among children treated pharmacologically, 1 teenager was submitted to radiofrequency transcatheter ablation on the basis of parental choice, 3 children have discontinued medical therapy recording only sporadic episodes of tachycardia, and 2 children are still treated with antiarrhythmic drugs. At the last follow-up visit, 13 children (68%) were without any treatment, 4 had been successfully ablated, and 2 were still on medical treatment.

CONCLUSIONS

Our data indicates a relatively benign outcome in this group of children and adolescents with atrioventricular nodal re-entrant tachycardia.

Perinatal arrhythmias: diagnosis and management

The final common pathway to death in all of us is an arrhythmia, yet we still know far too little about the contribution of conduction abnormalities and arrhythmias to the compromised states of the human fetus. At no other time in the human life cycle is the human being at more risk of unexplained and unexpected death than during the prenatal period. The risk of sudden death from 20-40 weeks gestation is 6-12 deaths/1000 fetuses/year. This is equal to, and in some ethnic groups HIGHER than, the risk of death in the adult population with known coronary artery disease over the same time frame (6-12 deaths/1000 patients/year). Because only a small percentage of the United States population is pregnant each year, because fetal demise is not often acknowledged through public displays such as funerals, and finally because fetal death is culturally accepted to a much greater extent than it should be, this critically important area of women's healthcare has not had the technological advances that have been seen in adult cardiac intensive care and other areas of medicine. Fetal cardiac deaths may be preventable and the diseases that lead to these deaths are often treatable, especially if the sophistication of our modern ICU's could somehow be translated to the prenatal monitoring arena. This review article will outline recent advances in evaluating fetal electrophysiology, helping the perinatologist to better understand the nuances of fetal arrhythmias.

Differential diagnosis and management of the fetus and newborn with an irregular or abnormal heart rate

This article separately discusses the differential diagnosis and management of irregular or abnormal heart rate in both the fetus and the newborn. Conditions covered include ectopic beats, tachyarrythmias,atrial flutter, bradyarrythmias, tachycardia, congenital atrioventricular block, long QT syndrome, and bradycardias,among others.

Amiodarone Therapy for Drug-Refractory Fetal Tachycardia

Background— Fetal tachycardia complicated by ventricular dysfunction and hydrops fetalis carries a significant risk of morbidity and mortality. Transplacental digoxin is effective therapy in a small percentage, but there is no consensus with regard to antiarrhythmic treatment if digoxin fails. This study evaluates the safety, efficacy, and outcome of amiodarone therapy for digoxin-refractory fetal tachycardia with heart failure.

Methods and Results— Fetuses with incessant tachycardia and either hydrops fetalis (n=24) or ventricular dysfunction (n=2) for whom digoxin monotherapy and secondary antiarrhythmic agents (n=13) were not effective were treated transplacentally with a loading dose of oral amiodarone for 2 to 7 days, followed by daily maintenance therapy for <1 to 15 weeks. Digoxin therapy was continued throughout gestation. Newborns were studied by transesophageal pacing or ECG monitoring to determine the mechanism of tachycardia. Three fetuses were delivered urgently in tachycardia during amiodarone loading, and 3 required additional antiarrhythmic agents for sustained cardioversion. Amiodarone or amiodarone combinations converted 14 of 15 (93%) with reentrant supraventricular tachycardia, 2 of 2 with ventricular or junctional ectopic tachycardia, and 3 of 9 (33%) with atrial flutter. Amiodarone-related adverse effects were transient in 5 infants and 8 mothers. Mean gestational age at delivery was 37 weeks, with 100% survival.

Conclusions— Orally administered amiodarone is safe and effective treatment for drug-refractory fetal tachycardia, specifically reentrant supraventricular tachycardia, junctional ectopic, or ventricular tachycardia, even when accompanied by hydrops fetalis or ventricular dysfunction.

Use of Transesophageal Atrial Pacing for Documentation of Arrhythmias Suspected in Infants and Children

Transesophageal atrial pacing study was used to document arrhythmias in 67 infants and children age 2 months to 16 years (mean, 8.3 years), who had palpitations or symptoms suggesting tachyarrhythmias but had no electrocardiographic documentation of cardiac dysrhythmias. The transesophageal pacing and medical records were reviewed retrospectively. In 47 of 67 (70%) of the infants and children with suspected tachyarrhythmias, transesophageal atrial pacing induced various tachycardias, which may be the cause of symptoms. In 10 of 67 patients, tachycardia was induced during infusion of isoproterenol. During the study, tachycardia was initiated in 14 of 15 patients less than < 6 years-old and in 33 of 52 patients > or = 6 years-old (P < 0.05). Of these induced tachycardias, 25 of 47 were atrioventricular reciprocating tachycardia, 16 atrioventricular nodal reentrant tachycardia, and 6 idiopathic left ventricular tachycardia. Both transesophageal study and invasive electrophysiologic study were performed in 10 patients. The mechanisms of tachycardia in the invasive study and transesophageal study were identical except for one patient. In conclusion, transesophageal atrial pacing and recording was less invasive, safe and useful for documenting arrhythmias in infants and children who had symptoms suggesting tachyarrhythmias, especially in patients < 6 years of age. Evaluation of the mechanism of induced tachycardia provided useful information regarding the prognosis and therapeutic options in infants and children.

Inducible atrioventricular nodal reentry tachycardia in infants with a history of neonatal orthodromic reciprocating tachycardia

Atrioventricular nodal reentry tachycardia (AVNRT) is an uncommon mechanism of supraventricular tachycardia in neonates in whom orthodromic reciprocating tachycardia (ORT) predominates. We report three patients with structurally normal hearts who presented with neonatal ORT, documented by transesophageal electrophysiology studies at 2 to 3 weeks of age. At follow-up study at 8-12 months of age, no infant had inducible ORT, suggesting spontaneous regression of congenital accessory pathways; however, each had inducible tachycardia consistent with the typical form of AVNRT. The clinical significance of this finding is unknown and warrants further study.

Fetoscopic transesophageal electrocardiography and stimulation in fetal sheep: a minimally invasive approach aimed at diagnosis and termination of therapy-refractory supraventricular tachycardias in human fetuses

BACKGROUND

Therapy-refractory supraventricular tachycardia commonly results in hydrops and death in human fetuses. The purpose of this study in fetal sheep was to assess the feasibility of a minimally invasive fetoscopic approach for fetal transesophageal electrocardiography and stimulation aimed at diagnosis and termination of these tachycardias.

METHODS AND RESULTS

We studied a total of 10 fetal sheep (87 to 103 days of gestation; term=145 days). We entered the amniotic cavity using a percutaneous fetoscopic approach and placed various electrophysiology catheters into the fetal esophagus. We recorded the number of animals in which fetoscopic transesophageal electrocardiography and stimulation were successful and assessed pacing success and thresholds for different catheters. In addition, we monitored for potential adverse effects from stimulation and for other complications of the operation. Recording of transesophageal electrocardiograms was successful in all fetal sheep. Capture during stimulation was successfully documented by additional fetal bipolar surface electrocardiograms in 7 fetuses. In fetuses in which fetal surface electrocardiograms were not recorded, pacing stimulus artifacts interfered with documentation of capture. Although stimulation thresholds were high, the maternal rhythm was not affected by fetal stimulation.

CONCLUSIONS

Fetoscopic fetal transesophageal electrocardiography and stimulation are feasible in fetal sheep. This minimally invasive approach might have the potential to improve diagnosis and management of therapy-refractory supraventricular tachycardias in human fetuses.

Assessment of accessory pathway and atrial refractoriness by transoesophageal and intracardiac atrial stimulation: an analysis of methodological agreement

AIMS

Measurement of the refractory properties of asymptomatic overt accessory pathways is performed to assess the risk for significant arrhythmias. We hypothesized that a transoesophageal atrial stimulation (TAS) protocol would accurately predict simultaneously measured invasive intra cardiac stimulation (ICS) of the anterograde effective refractory period of the accessory pathway (AP-ERP) METHODS AND RESULTS: Fourteen single pathway Wolff-Parkinson-White (WPW) syndrome patients underwent TAS during ICS and 24 h prior to it. The AP-ERP was measured using incremental atrial extra stimuli from TAS, the right atrium (RA) and the coronary sinus (CS) using drive trains of 500 and 600 ms. Stimulus latency was measured from intracardiac electrocardiograms. For methodological comparison, Altman-Bland analysis was used to create the limits of agreement (within-patient mean of differences +/- two standard deviations). There were no or small differences in the AP-ERP, as assessed by TAS, compared to RA and CS. Methodological disagreement between the three sites were common, however, and the limits of agreement ranged from +/- 30 to +/- 76 ms. The concordance between TAS and RA, with regards to the AP-ERP value of 270 ms, was 63% when measured as S1S2 and was 67% when measured as A1A2. The stimulation site delay was significantly shorter for TAS compared to RA and CS sites. The two TAS procedures performed a day apart, revealed a coefficient of variation of 9% and a coefficient of reproducibility of 63 ms.

CONCLUSIONS

Despite adequate reproducibility, TAS fails to predict the AP-ERP by ICS. Differences in stimulus latency is responsible, in part, for the disagreement. Invasive ICS cannot be replaced by TAS for risk stratifying WPW patients.

Characteristics, management, and midterm outcome in infants with atrioventricular nodal reentry tachycardia

Atrioventricular nodal reentry is a commonly recognized mechanism of supraventricular tachycardia (SVT) in adults, but is only rarely documented in the first year of life. The aim of this study was to elucidate characteristics, management, and outcome in infants with atrioventricular nodal reentrant tachycardia (AVNRT). Electrophysiologic studies performed between January 1988 and June 1996 were reviewed. Fifteen infants with AVNRT at 58 +/- 27 days (mean +/- SEM) were identified. Five had AVNRT detected following palliation of structural cardiac anomalies, including 4 with critical obstructions to left ventricular outflow. Typical AVNRT (ventriculoatrial interval 49 +/- 5 ms) was observed in 14 of 15 patients and atypical AVNRT (ventriculoatrial interval 191 +/- 22 ms) in 4 of 15. All patients received long-term therapy, beginning with digoxin in 13. Eight had symptomatic recurrences on digoxin and 6 of these were given beta blockers, with satisfactory control in 4. Three patients were controlled with class III agents, and 2 underwent slow pathway radiofrequency modification at ages 4.1 and 6.7 years, respectively. AVNRT was still inducible in 6 of 6 asymptomatic patients who underwent follow-up atrial stimulation studies after discontinuation of medical therapy. All 15 patients were alive with either absent or well-controlled AVNRT at age 45 +/- 7 months. We conclude that the course and outcome of AVNRT diagnosed in the first year of life are generally benign, but that a minority of patients have symptoms persisting beyond infancy. Digoxin is of questionable benefit in long-term control. AVNRT often remains inducible in asymptomatic patients, although the significance of this finding remains to be determined by long-term follow-up.

Overdrive atrial stimulation during transesophageal electrophysiological study: usefulness of post-pacing VA interval analysis in differentiating supraventricular tachycardias with 1:1 atrio-ventricular relationship

We evaluated the feasibility and usefulness of overdrive atrial pacing to identify the relationship between atrial and ventricular activation in supraventricular tachycardias with a stable 1:1 atrio-ventricular (AV) conduction ratio during a transesophageal electrophysiological investigation. Overdrive atrial stimulation was performed in 42 consecutive patients (11 males and 31 females; mean age 49 +/- 17 years) during AV junctional reentrant tachycardia, orthodromic AV reentrant tachycardia and ectopic atrial tachycardia (22, 13 and seven subjects, respectively). Trains of 12 stimuli at a constant rate were introduced starting at a cycle length 10 ms shorter than the tachycardia cycle length; stimulation was repeated with a 10-ms decrement in pacing cycle length at each step until tachycardia terminated and/or second-degree AV block occurred. The difference between the VA interval duration at baseline and in the first post-pacing tachycardia beat was measured at each step and provided identification of the AV relationship. At least one post-pacing VA interval was evaluable in 90% of the cases and measured 2 +/- 4 and 1 +/- 3 ms in AV junctional and AV reentrant tachycardia groups, respectively, and 83 +/- 42 ms in the ectopic atrial tachycardia group (P < 0.0000001 ectopic atrial tachycardia group vs. others). When three or more post-pacing VA intervals were obtained during the same tachycardia, a curve was constructed by plotting their values against the corresponding pacing cycle lengths. A curve could be constructed in 36% of the cases and was flat in all patients with AV junctional and AV reentry, while it was completely irregular in the ectopic atrial tachycardia group (P < 0.003). The analysis of post-pacing VA interval behaviour in response to overdrive atrial stimulation provides a rapid and reliable differentiation between supraventricular tachycardias with 1:1 AV conduction ratio during a transesophageal electrophysiological study.

Indications for radiofrequency ablation in the pediatric population

Pediatric radiofrequency ablation procedures have become commonplace since their introduction to clinical practice 6 years ago. Excellent success rates coupled with low complication rates have allowed these procedures to be offered as first-line therapy to many children. This review focuses on the current indications for radiofrequency ablation in children. These indications are not the same as for adults. They are based on the natural history of various forms of arrhythmias, the risks of the procedure, and the current success rates of the procedures, all of which are dependent upon the age of the patient.