Difficulties with invasive risk stratification performed under anesthesia in pediatric Wolff-Parkinson-White Syndrome.

BACKGROUND: Children with Wolff-Parkinson-White Syndrome (WPW) are at risk for sudden death. The gold standard for risk stratification in this population is the shortest pre-excited RR interval during atrial fibrillation (SPERRI). OBJECTIVE: The purpose of this study was to determine how closely measurements made in the electrophysiology laboratory in patients with WPW compared to SPERRI obtained during an episode of clinical pre-excited atrial fibrillation (Clinical-SPERRI). METHODS: This was a subgroup analysis of a multicenter study of children with WPW. Subjects in our study (N = 49) were included if they had Clinical-SPERRI measured in addition to 1 or more of 3 surrogate measurements: SPERRI obtained during electrophysiological study (EP-SPERRI), accessory pathway effective refractory period (APERP), or shortest pre-excited paced cycle length with 1:1 conduction (SPPCL). RESULTS: Seventy percent of electrophysiological measurements were made with patients under general anesthesia. Clinical-SPERRI moderately correlated with EP-SPERRI (r = 0.495; P = .012). However, 24% of our patients with Clinical-SPERRI ≤250 ms would have been misclassified as having a low-risk pathway based on EP-SPERRI >250 ms. Clinical-SPERRI did not correlate with APERP or SPPCL (r < 0.3; P >.1). Mean EP-SPERRI, APERP, and SPPCL all were greater than Clinical-SPERRI. CONCLUSION: Electrophysiology laboratory measurements of pathway characteristics made with patients under general anesthesia do not correlate well with Clinical-SPERRI. Of APERP, SPPCL, and EP-SPERRI, only EP-SPERRI had moderate correlation with Clinical-SPERRI. This study questions the predictive ability of invasive risk stratification with patients under general anesthesia, given that 24% of patients with high-risk Clinical-SPERRI (≤250 ms) had EP-SPERRI that may be considered low risk (>250 ms).

Validation of a novel automated signal analysis tool for ablation of Wolff-Parkinson-White Syndrome.

BACKGROUND: In previous pilot work we demonstrated that a novel automated signal analysis tool could accurately identify successful ablation sites during Wolff-Parkinson-White (WPW) ablation at a single center. OBJECTIVE: We sought to validate and refine this signal analysis tool in a larger multi-center cohort of children with WPW. METHODS: A retrospective review was performed of signal data from children with WPW who underwent ablation at two pediatric arrhythmia centers from 2008-2015. All patients with WPW ≤ 21 years who underwent invasive electrophysiology study and ablation with ablation signals available for review were included. Signals were excluded if temperature or power delivery was inadequate or lesion time was < 5 seconds. Ablation lesions were reviewed for each patient. Signals were classified as successful if there was loss of antegrade and retrograde accessory pathway (AP) conduction or unsuccessful if ablation did not eliminate AP conduction. Custom signal analysis software analyzed intracardiac electrograms for amplitudes, high and low frequency components, integrated area, and signal timing components to create a signal score. We validated the previously published signal score threshold 3.1 in this larger, more diverse cohort and explored additional scoring options. Logistic regression with lasso regularization using Youden's index criterion and a cost-benefit criterion to identify thresholds was considered as a refinement to this score. RESULTS: 347 signals (141 successful, 206 unsuccessful) in 144 pts were analyzed [mean age 13.2 ± 3.9 years, 96 (67%) male, 66 (45%) left sided APs]. The software correctly identified the signals as successful or unsuccessful in 276/347 (80%) at a threshold of 3.1. The performance of other thresholds did not significantly improve the predictive ability. A signal score threshold of 3.1 provided the following diagnostic accuracy for distinguishing a successful from unsuccessful signal: sensitivity 83%, specificity 77%, PPV 71%, NPV 87%. CONCLUSIONS: An automated signal analysis software tool reliably distinguished successful versus unsuccessful ablation electrograms in children with WPW when validated in a large, diverse cohort. Refining the tools using an alternative threshold and statistical method did not improve the original signal score at a threshold of 3.1. This software was effective across two centers and multiple operators and may be an effective tool for ablation of WPW.

A novel pacing maneuver to verify the postpacing interval minus the tachycardia cycle length while adjusting for decremental conduction: Using "dual-chamber entrainment" for improved supraventricular tachycardia discrimination.

BACKGROUND: The postpacing interval (PPI) minus the tachycardia cycle length (TCL) is frequently used to investigate tachycardias. However, a variety of issues (eg, failure to entrain, decremental conduction, and oscillating TCLs) can make interpretation of the PPI-TCL challenging. OBJECTIVE: The purpose of this study was to investigate a novel maneuver to confirm the PPI-TCL value without using either the ventricular PPI or the TCL interval and to assess the ability of this maneuver to identify decremental conduction and differentiate supraventricular tachycardias. METHODS: We analyzed 77 intracardiac recordings from patients (age 25 ± 20 years; 40 female) who underwent catheter ablation of atrioventricular nodal reentrant tachycardia (AVNRT) or orthodromic reciprocating tachycardia (ORT) with a concealed pathway. We calculated the PPI-TCL, the AH-corrected PPI-TCL, and estimated the PPI-TCL using "dual-chamber entrainment" calculated as [PPIV - TCL = Stim(A→V) + Stim(V→A) - PPIA]. RESULTS: The PPI-TCL calculated by dual-chamber entrainment highly correlated with the observed and AH-corrected PPI-TCL (R2 = 0.79 and 0.96, respectively; P <.001]. A dual-chamber entrainment PPI-TCL value of 80 ms correctly differentiated all AVNRT from septal ORT cases, whereas the standard PPI-TCL and AH-corrected PPI-TCL methods were incorrect in 14% and 6% of cases, respectively. Dual-chamber entrainment identified 3 ± 10 ms of additional decremental conduction beyond AH prolongation, including 4 pathways with significant (>10 ms) decrement. CONCLUSION: Dual-chamber entrainment estimates the PPI-TCL value without using either the ventricular PPI or the TCL interval. This maneuver adjusts for all decremental conduction, including within concealed pathways, where a dual-chamber entrainment PPI-TCL value >80 ms favors AVNRT over ORT. This maneuver can be used to verify the observed PPI-TCL value in challenging cases.

A multicenter review of ablation in the aortic cusps in young people.

BACKGROUND: Ablation within the aortic cusp is safe and effective in adults. There are little data on aortic cusp ablation in the pediatric literature. We investigated the safety and efficacy of aortic cusp ablation in young patients. METHODS: A retrospective, descriptive study of aortic cusp ablation in five pediatric electrophysiology centers from 2008 to 2014 was performed. All patients <21 years of age who underwent ablation in the aortic cusps were included. Factors analyzed included patient demographics, procedural details, outcomes, and complications. RESULTS: Thirteen patients met inclusion criteria (median age 16 years [range 10-20.5] and median body surface area 1.58 m2 [range 1.12-2.33]). Substrates for ablation included: nine premature ventricular contractions or sustained ventricular tachycardia (69%), two concealed anteroseptal accessory pathways (APs) (15%), one Wolff-Parkinson-White with an anteroseptal AP (8%), and one ectopic atrial tachycardia (8%). Three-dimensional electroanatomic mapping in combination with fluoroscopy was used in 12/13 (92%) patients. Standard 4-mm-tip radiofrequency (RF) current was used in 11/13 (85%) and low-power irrigated-tip RF in 2/13 (15%). Angiography was used in 13/13 and intracardiac echocardiography was additionally utilized in 3/13 (23%). Ablation locations included: eight noncoronary (62%), three left (23%), and two right (15%) cusps. Ablation was acutely successful in all patients. At median follow-up of 20 months, there was one recurrence of PVCs (8%). There were no ablation-related complications and no valvular injuries observed. CONCLUSION: Arrhythmias originating from the coronary cusps in this series were successfully and safely ablated in young people without injury to the coronary arteries or the aortic valve.

Electrocardiographic repolarization abnormalities and increased risk of life-threatening arrhythmias in children with dilated cardiomyopathy.

BACKGROUND: Life-threatening arrhythmia events (LTEs) occur in ~5% of children with dilated cardiomyopathy (DCM). While prolonged QRS duration has been shown to be associated with LTEs, electrocardiographic (ECG) repolarization findings have not been examined. OBJECTIVE: We sought to determine the associations between ECG repolarization abnormalities and LTEs in children with DCM. METHODS: A single-center retrospective review of children with DCM was performed. LTEs were defined as documented ventricular tachycardia or fibrillation requiring medical intervention. Three pediatric cardiologists, blinded to clinical events, evaluated ECGs obtained at the time of initial referral. Kaplan-Meier survival and Cox proportional hazards analyses were used to evaluate time to LTEs. RESULTS: A total of 137 patients (mean age 7.8 ± 6.7 years; 75(55%) male patients) with DCM (mean ejection fraction 35% ± 16%) were included; 67 patients (49%) had a corrected JT (JTc) interval of ≥340 ms, 72 (53%) had a corrected QT (QTc) interval of ≥450 ms, and 41 (30%) had abnormal T waves. LTEs occurred in 15 patients at a median of 12 months (interquartile range 3-36 months) after the initial ECG. Patients with LTEs had a longer JTc interval (371 ± 77 ms vs 342 ± 41 ms; P = .02) and a longer QTc interval (488 ± 96 ms vs 453 ± 44 ms; P = .01). In survival analysis, a JTc interval of ≥390 ms (hazard ratio [HR] 4.07; 95% confidence interval [CI] 1.12-14.83; P = .03), a QTc interval of ≥510 ms (HR 6.95; 95% CI 1.53-31.49; P = .01), abnormal T-wave inversion (HR 11.62; 95% CI 2.75-49.00; P = .001), and ST-segment depression (HR 6.91; 95% CI 1.25-38.27; P = .03) were associated with an increased risk of LTEs, even after adjusting for QRS duration and amiodarone use. CONCLUSION: Repolarization abnormalities are common in children with DCM. Certain ECG repolarization abnormalities, such as significantly prolonged JTc and QTc intervals, may be useful in identifying patients at risk of LTEs.

The precise timing of tachycardia entrainment is determined by the postpacing interval, the tachycardia cycle length, and the pacing rate: Theoretical insights and practical applications.

BACKGROUND: Previous observations have reported that the number of pacing stimuli required to entrain a tachycardia varies on the basis of arrhythmia type and location, but a quantitative formulation of the number needed to entrain (NNE) that unifies these observations has not been characterized. OBJECTIVE: We sought to investigate the relationship between the number of pacing stimulations, the tachycardia cycle length (TCL), the overdrive pacing cycle length (PCL), and the postpacing interval (PPI) to accurately estimate the timing of tachycardia entrainment. METHODS: First, we detailed a mathematical derivation unifying electrophysiological parameters with empirical confirmation in 2 patients undergoing catheter ablation of typical atrial flutter. Second, we validated our formula in 44 patients who underwent various catheter ablation procedures. For accuracy, we corrected for rate-related changes in conduction velocity. RESULTS: We derived the equations NNE = |(PPI - TCL)/(TCL - PCL)| + 1 and Tachycardia advancement = (NNE - 1) × (TCL - PCL) - (PPI - TCL), which state that the NNE and the amount of tachycardia advancement on the first resetting stimulation are determined using regularly measured intracardiac parameters. In the retrospective cohort, the observed PPI - TCL highly correlated with the predicted PPI - TCL (mean difference 5.8 ms; r = 0.97; P < .001), calculated as PPI - TCL = (NNE - 1) × (TCL - PCL) - tachycardia advancement. CONCLUSION: The number of pacing stimulations required to entrain a reentrant tachycardia is predictable at any PCL after correcting for cycle length-dependent changes in conduction velocity. This relationship unifies established empirically derived diagnostic and mapping criteria for supraventricular tachycardia and ventricular tachycardia. This relationship may help elucidate when antitachycardia pacing episodes are ineffective or proarrhythmic and could potentially serve as a theoretical basis to customize antitachycardia pacing settings for improved safety and effectiveness.

50 is the new 70: Short ventriculoatrial times are common in children with atrioventricular reciprocating tachycardia.

BACKGROUND: One of the basic electrophysiological principles of atrioventricular reciprocating tachycardia (AVRT) is that ventriculoatrial (VA) times during tachycardia are >70 ms. We hypothesized, however, that children may commonly have VA times <70 ms in AVRT. OBJECTIVE: This study sought to determine the incidence and characteristics associated with short-VA AVRT in children. METHODS: A retrospective single-center review of children with AVRT from 2000 to 2014 was performed. All patients ≤18 years of age with AVRT at electrophysiology study were included. Patients with persistent junctional reciprocating tachycardia, atrioventricular nodal reentry tachycardia, and tachycardia not unequivocally proven to be AVRT were excluded. VA time was defined as the time between earliest ventricular activation and earliest atrial activation in any lead and was confirmed by 2 electrophysiologists. Patients with VA times <70 ms (SHORT-VA) and those with standard VA times ≥70 ms (STD-VA) were compared. Logistic regression analysis identified characteristics of SHORT-VA patients. RESULTS: A total of 495 patients with AVRT were included (mean age 11.7 ± 4.1 years). There were 265 patients (54%) with concealed accessory pathways (APs) and 230 (46%) with Wolff-Parkinson-White syndrome. AP location was left-sided in 301 patients (61%) and right-sided in 194 (39%). The mean VA time in AVRT was 100 ± 33 ms. A total of 63 patients (13%) had VA times <70 ms (SHORT-VA). The shortest VA time during AVRT was 50 ms. There was no difference in age, AV nodal block cycle, or body surface area between SHORT-VA and STD-VA patients, but SHORT-VA patients had lower weight (43 ± 17 vs 51 ± 23 kg, P = .02), lower AV nodal effective refractory period (AVNERP; 269 ± 50 vs 245 ± 52 ms, P < .01), and more left-sided APs (50 [79%] vs 251 [58%]; P < .01]. On multivariate logistic regression, factors associated with SHORT-VA included left-sided AP (odds ratio [OR] 5.79, confidence interval [95% CI] 2.21-15.1, P < .01), shorter AVNERP (OR 0.99, CI 0.98-0.99, P < .01), and lower weight (OR 0.97, CI 0.95-0.99, P < .01). CONCLUSIONS: Children with AVRT can frequently have VA times <70 ms, with 50 ms being the shortest VA time. This finding debunks the classic electrophysiology principle that VA times in AVRT must be >70 ms. SHORT-VA AVRT was more common in children with left-sided APs.

Success rates in pediatric WPW ablation are improved with 3-dimensional mapping systems compared with fluoroscopy alone: a multicenter study.

INTRODUCTION: Three-dimensional mapping (3-D) systems are frequently used for ablation of supraventricular tachycardia. Prior studies have demonstrated radiation dosage reduction with 3-D, but there are no data on whether 3-D improves the efficacy of ablation of Wolff-Parkinson-White syndrome (WPW). We sought to determine if 3-D improves the success rate for ablation of WPW in children. METHODS: Multicenter retrospective study including patients ≤21 years of age with WPW undergoing ablation from 2008 to 2012. Success rates using the 2 techniques (3-D vs. fluoroscopy alone [FLUORO]) were compared. RESULTS: Six hundred and fifty-one cases were included (58% male, mean age 13 ± 4 years, 366 [56%] 3-D). Baseline characteristics including gender, weight, accessory pathway (AP) location, number of APs, and repeat ablation attempts were similar between the 2 groups (3-D and FLUORO) The 3-D group was slightly younger (12.7 ± 4.0 vs. 13.3 ± 4.0 years; P = 0.04) and less likely to undergo ablation utilizing cryoenergy (38 [10%] vs. 56 [20%]; P < 0.01). The 3-D group had a higher acute success rate of ablation (355 [97%] vs. 260 [91%]; P < 0.01). No differences were seen in recurrence (16 [5%] vs. 26 [9%]; P = 0.09) or complication rates (1 [0.3%] vs. 1 [0.4%]; P = 0.86) between the groups. On multivariable analysis, 3-D was shown to significantly improve success at ablation with an odds ratio of 3.1 (95% CI 1.44-6.72; P < 0.01). CONCLUSIONS: Use of 3-D significantly improved success rates for ablation of WPW in children. The increase in acute success associated with 3-D suggests it is an important adjunct for catheter ablation of WPW in children.

Diagnosis and management of pediatric brugada syndrome: a survey of pediatric electrophysiologists.

BACKGROUND: Brugada syndrome (BrS) can be difficult to diagnose and treat, especially in the young patient. As there is currently no consensus on the evaluation and treatment of BrS in the pediatric population, we sought to describe the current practice for the diagnosis and treatment of BrS among pediatric electrophysiologists. METHODS: A web-based survey was distributed to 204 physician members (MDs) of The Pediatric and Adult Congenital Electrophysiology Society (PACES). Practice characteristics, BrS patient attributes, and diagnostic and therapeutic preferences were collected. RESULTS: Responses were obtained from 83 pediatric electrophysiologists. The most common initial presentation was family history. There is a large variation in testing, particularly in the use of electrophysiology (EP) studies, drug challenge testing, and genetic testing. Despite limited treatment options, there is only consensus in the therapeutic approach to the pediatric patient with symptomatic BrS with 97% of physicians recommending an implantable cardioverter defibrillator (ICD). In the asymptomatic patient, a wide variation in therapy was seen with only 27% of physicians recommending an ICD CONCLUSIONS: Significant practice variation exists among pediatric electrophysiologists with deviation from accepted diagnostic and therapeutic practices for adult BrS patients. Further studies are necessary to establish best practice guidelines for BrS in the pediatric EP community.

Diagnostic tools for arrhythmia detection in adults with congenital heart disease and heart failure.

As patients with congenital heart disease age with increasingly complex lesions, heart failure and arrhythmias have emerged as leading sources of morbidity and mortality. The two are intertwined, as one may herald, beget, or aggravate the other. Moreover, arrhythmias in adults with congenital heart disease and heart failure can be poorly tolerated or life threatening. There is, therefore, much interest in promptly and accurately diagnosing arrhythmias and identifying risk factors for sudden death. This article appraises current knowledge regarding diagnostic tools for arrhythmias in adults with congenital heart disease and heart failure and comments on their prognostic value where relevant.

Electrophysiologic therapeutics in heart failure in adult congenital heart disease.

Arrhythmias have long been recognized as a major cause of morbidity and mortality in the adult with congenital heart disease. It is important that the clinician accurately diagnoses these disturbances and is cognizant of the full array of antiarrhythmic agents and devices available to treat these conditions. This review discusses the most common arrhythmias encountered in this population and the therapeutic options available. Specific issues unique to this population are also addressed.

Pediatric cardiovascular safety: challenges in drug and device development and clinical application.

Development of pediatric medications and devices is complicated by differences in pediatric physiology and pathophysiology (both compared with adults and within the pediatric age range), small patient populations, and practical and ethical challenges to designing clinical trials. This article summarizes the discussions that occurred at a Cardiac Safety Research Consortium-sponsored Think Tank convened on December 10, 2010, where members from academia, industry, and regulatory agencies discussed important issues regarding pediatric cardiovascular safety of medications and cardiovascular devices. Pediatric drug and device development may use adult data but often requires additional preclinical and clinical testing to characterize effects on cardiac function and development. Challenges in preclinical trials include identifying appropriate animal models, clinically relevant efficacy end points, and methods to monitor cardiovascular safety. Pediatric clinical trials have different ethical concerns from adult trials, including consideration of the subjects' families. Clinical trial design in pediatrics should assess risks and benefits as well as incorporate input from families. Postmarketing surveillance, mandated by federal law, plays an important role in both drug and device safety assessment and becomes crucial in the pediatric population because of the limitations of premarketing pediatric studies. Solutions for this wide array of issues will require collaboration between academia, industry, and government as well as creativity in pediatric study design. Formation of various epidemiologic tools including registries to describe outcomes of pediatric cardiac disease and its treatment as well as cardiac effects of noncardiovascular medications, should inform preclinical and clinical development and improve benefit-risk assessments for the patients. The discussions in this article summarize areas of emerging consensus and other areas in which consensus remains elusive and provide suggestions for additional research to further our knowledge and understanding of this topic.

Arrhythmogenic forms of heart failure in children.

There are various underlying causes of tachycardia-induced cardiomyopathy (TIC), and it is critical that it be considered in any patient who presents with a newly diagnosed dilated cardiomyopathy. Unlike most other forms of cardiomyopathy, TIC should be considered a treatable form of cardiomyopathy and it is imperative that the diagnosis be fully considered. A 12-lead ECG should be obtained in all patients with a dilated cardiomyopathy. Prompt diagnosis and therapy of this relatively uncommon cause of heart failure is critical and has the potential to completely reverse the ventricular dysfunction that may be present in this abnormality.

Acute effects of single-site pacing from the left and right ventricle on ventricular function and ventricular-ventricular interactions in children with normal hearts.

OBJECTIVE: We studied, as a physiological benchmark, acute effects of right ventricular (RV) apical, RV outflow, and left ventricular (LV) pacing in children with normal cardiac function on LV and RV function and ventricular-ventricular interactions. DESIGN: The design of the study was a prospective, acute intervention. SETTING: The study was conducted in a tertiary care electrophysiology laboratory. Population and Methods. Seven children (mean +/- SD, 12 +/- 4 years) were paced after accessory pathway ablation, at baseline (AOO), and with atrioventricular pacing (DOO) from the RV apex, RV outflow, and left ventricle. OUTCOME MEASURES: Right ventricular dP/dT(max) and RV dP/dT(neg) (high-fidelity transducer-tipped catheters, Millar Instruments, Houston, TX, USA), cardiac index (Fick), blood pressure, and QRS duration were measured at each pacing condition. Intra- and interventricular mechanical dyssynchrony, systolic- and diastolic peak tissue velocities, and isovolumic acceleration were recorded by tissue Doppler imaging at the lateral mitral, septal, and tricuspid annuli at each condition. Results at each pacing condition were compared by repeated-measures analysis of variance. Results. Pacing prolonged QRS duration, causing electrical dyssynchrony (86 +/- 19 ms [baseline], 141 +/- 44 ms [RV apex], 121 +/- 18 ms [RV outflow], and 136 +/- 34 ms [LV], P < .01). Right ventricular outflow pacing caused LV intraventricular delay (63 +/- 52 vs. 12 +/- 7 ms, P < .05). Right ventricular apical pacing caused interventricular delay (61 +/- 29 vs. 25 +/- 18 ms, P < .05). There were no significant changes in blood pressure, cardiac index, RV dp/dT(max), RV dP/dT(neg), regional tissue velocities, or isovolumic acceleration during any of the pacing conditions, indicating preserved ventricular function and hemodynamics. No important ventricular-ventricular interactions were seen. CONCLUSIONS: In children with normal cardiac anatomy and function, single-site RV apical, RV outflow, and LV pacing induce electromechanical dyssynchrony without significantly changing ventricular function or hemodynamics, or adversely affecting ventricular-ventricular interactions.

The effects of dexmedetomidine on cardiac electrophysiology in children.

BACKGROUND: Dexmedetomidine (DEX) is an alpha2-adrenergic agonist that is approved by the Food and Drug Administration for short-term (<24 h) sedation in adults. It is not approved for use in children. Nevertheless, the use of DEX for sedation and anesthesia in infants and children appears to be increasing. There are some concerns regarding the hemodynamic effects of the drug, including bradycardia, hypertension, and hypotension. No data regarding the effects of DEX on the cardiac conduction system are available. We therefore aimed to characterize the effects of DEX on cardiac conduction in pediatric patients. METHODS: Twelve children between the ages of 5 and 17 yr undergoing electrophysiology study and ablation of supraventricular accessory pathways had hemodynamic and cardiac electrophysiologic variables measured before and during administration of DEX (1 microg/kg IV over 10 min followed by a 10-min continuous infusion of 0.7 microg x kg(-1) x h(-1)). RESULTS: Heart rate decreased while arterial blood pressure increased significantly after DEX administration. Sinus node function was significantly affected, as evidenced by an increase in sinus cycle length and sinus node recovery time. Atrioventricular nodal function was also depressed, as evidenced by Wenckeback cycle length prolongation and prolongation of PR interval. CONCLUSION: DEX significantly depressed sinus and atrioventricular nodal function in pediatric patients. Heart rate decreased and arterial blood pressure increased during administration of DEX. The use of DEX may not be desirable during electrophysiology study and may be associated with adverse effects in patients at risk for bradycardia or atrioventricular nodal block.

Cryoablation of accessory pathways in the coronary sinus in young patients: a multicenter study from the Pediatric and Congenital Electrophysiology Society's Working Group on Cryoablation.

INTRODUCTION: This is a multicenter retrospective study evaluating the immediate- and mid-term outcomes of cryoablation of accessory pathways in the coronary sinus in children or in patients with congenital heart disease. METHODS AND RESULTS: Twenty-one patients (median age 13.0 years, range 2-40) from six institutions were included. The accessory pathways were concealed in 11 and manifest in 10. Of 12 patients who had coronary sinus angiography, two had large coronary sinus diverticula, one had a dilated coronary sinus due to a left superior vena cava to coronary sinus, and one had a "pouch" at the mouth of the coronary sinus. Six patients underwent ablation procedures with cryoablation alone, while in the remaining 15 patients, both cryoablation and radiofrequency ablation were utilized. The ablation procedure included left-sided endocardial mapping via a retrograde or transseptal approach in 13 (62%). Procedural success was achieved with cryoablation in the coronary sinus in 15/21 (71%). Four patients (19%) had successful radiofrequency ablation at the right or left posterior septum. Two patients (10%) had unsuccessful procedures. Of the 15 patients with initially successful cryoablation procedures, six (40%) had arrhythmia recurrences at a median of 17 days (range 1-120). Recurrences could not be explained by differences in patient or procedural variables. CONCLUSION: Cryoablation in the coronary venous system in young patients is feasible but associated with a high arrhythmia recurrence rate. Cryoablation techniques and/or equipment need to be improved in order to safely create more permanent lesions in this arrhythmia substrate.

Electrophysiological interventions for treatment of congestive heart failure in pediatrics and congenital heart disease.

Heart failure therapy, while well tested in the adult population, therapeutic interventions are less well defined in the pediatric population. Several treatment strategies are available for the adult patient with heart failure, thought few of these therapies have been proven in children. Morbidity and mortality in the pediatric population with a failing heart is significant, and rhythm management as well as strategies to improve hemodynamics are important in the care of these children. This review will address issues of rhythm management and resynchronization therapy in pediatric and congenital heart disease patients with heart failure.

Characterizing dual atrioventricular nodal physiology in pediatric patients with atrioventricular nodal reentrant tachycardia.

INTRODUCTION: Dual atrioventricular (AV) nodal physiology, defined as an AH jump > or =50 msec with a 10 msec decrease in A1A2, is the substrate for atrioventricular nodal reentrant tachycardia (AVNRT) and yet it is present in a minority of pediatric patients with AVNRT. Our objective was to characterize dual AV nodal physiology as it pertains to a pediatric population. METHODS/RESULTS: We retrospectively reviewed invasive electrophysiology studies in 92 patients with AVNRT (age12.1 +/- 3.7 yrs) and in 46 controls without AVNRT (age 13.3 +/- 3.7 yrs). Diagnoses in controls: syncope (N = 31), palpitations (N = 6), atrial flutter (N = 3), history of atrial tachycardia with no inducible arrhythmia (N = 3), and ventricular tachycardia (N = 3). General anesthesia was used in 49% of AVNRT and 52% of controls, P = 0.86. There were no differences in PR, AH, HV, or AV block cycle length. With A1A2 atrial stimulation, AVNRT patients had a significantly longer maximum AH achieved (324 +/- 104 msec vs 255 +/- 67 msec, P = 0.001), and a shorter AVNERP (276 +/- 49 msec vs 313 +/- 68 msec P = 0.0005). An AH jump > or =50 msec was found in 42% of AVNRT versus 30% of controls (P = 0.2). Using a ROC graph we found that an AH jump of any size is a poor predictor of AVNRT. With atrial overdrive pacing, PR > or = RR was seen more commonly in AVNRT versus controls, (55/91(60%) vs 6/46 (13%) P = 0.000). CONCLUSIONS: Neither the common definition of dual AV nodes or redefining an AH jump as some value <50 msec are reliable methods to define dual AV nodes or to predict AVNRT in pediatric patients. PR > or = RR is a relatively good predictor of AVNRT.