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Objective: The purpose of this study is to describe the outcomes of cardiac catheterizations performed by pediatric interventional cardiologists in an adult catheterization laboratory on adult patients with congenital heart disease (CHD)., Background: With improved survival rates, the number of adults with CHD increases by ∼5%/year; this population often requires cardiac catheterization., Methods: From January 2005 to December 2009, two groups of patients were identified, an adult group (>21 years) and an adolescent group (13-21 years), who had catheterizations performed by pediatric interventional staff., Results: Fifty-seven catheterizations were performed in 53 adults, while 59 were performed in 47 adolescents. The male to female ratio differed significantly between groups; only 15/53 (28%) of adults were male vs. 26/47 (55%) of adolescents (P =.006). Among adults, 27 had previously corrected CHD, 16 with atrial septal defect (ASD), and six with patent foramen ovale (PFO). This differed significantly from the adolescents, where only 30 had previously corrected CHD, seven with ASD, and one with PFO (P =.012). Among adults who were catheterized, interventions were performed on 28/53 (53%). All interventions were successful and included ASD/PFO closure, patent ductus arteriosus occlusion, coarctation dilation, pulmonary artery dilations, and one saphenous vein graft aneurysm closure. Nineteen adults had coronary angiography performed by adult interventionalists in consult with pediatric interventionalists. Two complications occurred among adults (3.8%) vs. one complication (2%; P = 1) among adolescents. No femoral vessel complications or catheterization-associated mortality occurred., Conclusions: Cardiac catheterizations can be performed effectively and safely in adults with CHD by pediatric interventional cardiologists in an adult catheterization laboratory., (© 2012 Wiley Periodicals, Inc.)

Understanding the basis for differential responses to drug therapies remains a challenge despite advances in genetics and genomics. Induced pluripotent stem cells (iPSCs) offer an unprecedented opportunity to investigate the pharmacology of disease processes in therapeutically and genetically relevant primary cell types in vitro and to interweave clinical and basic molecular data. We report here the derivation of iPSCs from a long QT syndrome patient with complex genetics. The proband was found to have a de novo SCN5A LQT-3 mutation (F1473C) and a polymorphism (K897T) in KCNH2, the gene for LQT-2. Analysis of the biophysics and molecular pharmacology of ion channels expressed in cardiomyocytes (CMs) differentiated from these iPSCs (iPSC-CMs) demonstrates a primary LQT-3 (Na(+) channel) defect responsible for the arrhythmias not influenced by the KCNH2 polymorphism. The F1473C mutation occurs in the channel inactivation gate and enhances late Na(+) channel current (I(NaL)) that is carried by channels that fail to inactivate completely and conduct increased inward current during prolonged depolarization, resulting in delayed repolarization, a prolonged QT interval, and increased risk of fatal arrhythmia. We find a very pronounced rate dependence of I(NaL) such that increasing the pacing rate markedly reduces I(NaL) and, in addition, increases its inhibition by the Na(+) channel blocker mexiletine. These rate-dependent properties and drug interactions, unique to the proband's iPSC-CMs, correlate with improved management of arrhythmias in the patient and provide support for this approach in developing patient-specific clinical regimens.

Purpose: Ablation of anteroseptal accessory pathways have historically been associated with lower success rates and a higher risk of AV nodal injury due to close proximity to the compact AV node. We describe the technique of ablation of anteroseptal APs via the right internal jugular vein (RIJV)., Methods: A retrospective analysis of all patients undergoing EP study and ablation at the Children's Hospital at Montefiore from 2008 to 2011 for SVT and/or WPW was performed. All patients less than 21 years of age who underwent ablation from the RIJV for either WPW or a concealed accessory pathway located in the anteroseptal region were included., Results: A total of 16 patients met inclusion criteria and were the subject of this analysis. Twelve patients had WPW (75%) and four had a concealed AP (25%). Ablation was acutely successful in 94% of patients (15/16). In one patient, ablation was deferred due to close proximity to the compact AV node and risk of AV nodal injury. Radiofrequency (RF) was used in 14 patients and cryoenergy in two patients. There was no difference in WB CL pre- and post-ablation (p = 0.19). There were no complications encountered. At a mean follow-up of 15 ± 12 months, there were no recurrences., Conclusion: Ablation of APs in the right anteroseptal region can safely and effectively be performed via the RIJV with a success rate of 94%. This technique should be considered for ablation of APs located in the anterior septum.

Myocardial infarction in a neonate is rare. We describe the case of a full-term male who presented with respiratory distress. A chest radiograph demonstrated cardiomegaly. An electrocardiogram revealed ST segment changes suggestive of ischemia. Cardiac enzymes were elevated and an echocardiogram revealed a regional wall motion abnormality. Cardiac catheterization was performed demonstrating occlusion of the ramus intermedius branch of the left main coronary artery. The patient decompensated, requiring extracorporeal membrane oxygenation (ECMO). The infant was able to be decannulated from ECMO support in 5 days and was ultimately discharged on hospital day 25. We review this case as well as the literature on neonatal myocardial infarction., (© 2012 Wiley Periodicals, Inc.)

Background: Orienting the left atrial disc of an atrial septal defect (ASD) closure device parallel to the septum is important, particularly in cases of ASD with deficient retroaortic rim. Standard vascular sheaths can make this challenging. We report the use of an electrophysiologic sheath, the SL2™ St. Jude Vascular sheath (St. Jude Medical, St. Paul, MN) for closure of ASD., Methods: All patients undergoing ASD closure between July 2010 and February 2011 at The Children's Hospital at Montefiore in which the SL2 sheath was used were reviewed., Results: Nine patients underwent transcatheter ASD or PFO (1/9) closure with the SL2 sheath. Mean age was 22.7 years (range, 3-58); weight was 46.5 kg (range, 14.7-78.6). The Amplatzer ASD Occluder (AGA Medical Corp., Plymouth, MN) was used in all cases. The mean measurement of the ASDs via "stop-flow" technique was 13.3 mm (range, 4-19). The mean device size was 13.9 mm (range, 5-20) or 105% the size of the defect. The retroaortic rim was deficient (<2 mm) in 3 of 9. ASD closure was achieved in 9 of 9. In all, the left atrial disk was brought toward the atrial septum parallel to the atrial septum, and repositioning or recapturing of the device was unnecessary in any case. Mean fluoroscopy time was 9.3 min (range, 2.2-18). No significant complications., Conclusions: The SL2 sheath was useful to position the ASD device parallel to the atrial septum, eliminating the need for redeployment during the procedure. This sheath was useful in those cases of deficient retroaortic rim in this study., (Copyright © 2012 Wiley Periodicals, Inc.)

Introduction: Ventricular tachycardia (VT) arising from the right ventricular inflow (RVI) region is uncommon. There is minimal literature on the clinical and electrocardiographic characteristics of RVI VT., Methods: A retrospective analysis of patients with RVI VT who underwent electrophysiology study between 2006 and 2011 was performed. Patients with structural heart disease (including arrhythmogenic right ventricular dysplasia) were excluded., Results: Seventy patients underwent an electrophysiology study for VT arising from the right ventricle during the study period. Nine patients (13%) met the inclusion criteria for RVI VT and were the subject of this analysis. The median age was 46 years (range, 14-71), and VT cycle length was 295 milliseconds (range, 279-400 milliseconds). All VTs had an left bundle-branch block morphology. An inferiorly directed QRS axis was noted in 7 (78%) of 9 patients and a left superior axis in 2 (22%) of 9 patients. A QS or rS pattern was noted in all patients in aVR and V(1). A transition from S to R wave occurred in V(3) to V(5) in all patients, with 78% of the patients transitioning in V(4) or V(5). Ablation was attempted in 8 (89%) of 9 patients and was successful in 6 (67%) of 9 patients. Ablation was limited in all unsuccessful patients due to the proximity to the His and risk of complete heart block., Conclusions: Electrocardiographic findings of a left bundle-branch block with a normal QRS axis, QS or rS patterns in aVR and V(1), and late S to R transition (V(4)/V(5)) are commonly found in RVI VT. Because of the proximity to the His, ablation of RVI VT may be more challenging than that of right ventricular outflow tract VT., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Background: Antidromic reciprocating tachycardia (ART) is a rare form of wide complex tachycardia in children with Wolff-Parkinson-White syndrome (WPW). The incidence and electrophysiologic characteristics of ART in children with WPW have not been well described., Methods: A multicenter retrospective analysis of all patients with WPW undergoing electrophysiology (EP) study from 1990 to 2009 was performed. Patients with clinical or inducible ART were included., Results: A total of 1,147 patients with WPW underwent EP study and 30 patients had ART (2.6%) and were the subject of this analysis. The mean age was 16±3 years, weight was 65±16 kg, and tachycardia cycle length was 305±55 ms. There were two patients (7%) with congenital heart disease (both with Ebstein's anomaly). Four patients (13%) had more than one accessory pathway (AP). The location of the AP was left sided in 53% of patients and right sided in 47%, with septal location and left lateral pathways most commonly involved. AP conduction was found to be high risk in 17 patients (57%). Ablation was not attempted in two patients (7%) due to proximity to the HIS and risk of heart block. Ablation was acutely successful in 93% of the patients in whom it was attempted., Conclusions: ART is a rare finding in children undergoing EP study. Over half of the patients with ART were found to be high risk and multiple AP were uncommon. Unlike the adult population, ART occurred commonly with septal APs., (©2012, The Authors. Journal compilation ©2012 Wiley Periodicals, Inc.)

Juvenile polyarteritis nodosa (PAN) is a rare, necrotizing vasculitis, primarily affecting small to medium-sized muscular arteries. Cardiac involvement amongst patients with PAN is uncommon and reports of coronary artery aneurysms in juvenile PAN are exceedingly rare. We describe a 16 year old girl who presented with fever, arthritis and two giant coronary artery aneurysms, initially diagnosed as atypical Kawasaki disease and treated with IVIG and methylprednisolone. Her persistent fevers, arthritis, myalgias were refractory to treatment, and onset of a vasculitic rash suggested an alternative diagnosis. Based on angiographic abnormalities, polymyalgia, hypertension and skin involvement, this patient met criteria for juvenile PAN. She was treated with six months of intravenous cyclophosphamide and high dose corticosteroids for presumed PAN related coronary vasculitis. Maintenance therapy was continued with azathioprine and the patient currently remains without evidence of active vasculitis. She remains on anticoagulation for persistence of the aneurysms. This case illustrates a rare and unusual presentation of giant coronary artery aneurysms in the setting of juvenile PAN.

Background: Identification of the site of successful radiofrequency catheter ablation (RFCA) for Wolff-Parkinson-White (WPW) syndrome may be subjective., Objective: The purpose of this study was to develop an automated signal analysis program to predict a successful ablation site., Methods: Patients who underwent successful RFCA for WPW from 2008- 2010 at our center were analyzed. Inclusion criteria were age <21 years, loss of preexcitation in <5 seconds, and sustained success at 3 months. Exclusion criteria were congenital heart disease and pacing during RFCA. The standard recording system signal was filtered into low frequency (LF 0-≤0.02 Hz) and high frequency (HF >0.02-≤0.45 Hz). Software identified the beginning of the HF signal, LF and R-wave peaks, LF/HF signal amplitude, and area under the HF/LF signals. Successful and unsuccessful (radiofrequency energy applied without accessory pathway block) signals were compared., Results: Thirty patients were analyzed; 16 had both successful and unsuccessful signals, and 14 had a successful ablation with 1 radiofrequency application. Mean age was 13.7 ± 3.1 years, weight 54.9 ± 22.4 kg, and time to accessory pathway ablation 1.7 ± 1.4 seconds. Significant differences were found between successful and unsuccessful signals in area under HF signal, LF amplitude, LF to R time, HF ratio, and HF area × HF ratio. A receiver operating curve of HF area × HF ratio produced an area under the curve of 0.89. An HF area × HF ratio of 3.1 distinguished successful from unsuccessful signals with 100% specificity and 81% sensitivity., Conclusion: Automated signal analysis retrospectively differentiated successful from unsuccessful signals in patients undergoing RFCA for WPW. This software may improve the safety and efficacy of RFCA in children., (Copyright © 2012 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: Electrocardiograms (ECGs) are sent via facsimile by pediatricians and psychiatrists to cardiologists for assessment. The validity of this method of transmission has not been established., Methods:  ECGs were collected from 100 consecutive patients from the cardiology clinic of the Children's Hospital at Montefiore. The ECGs were faxed and also electronically faxed (efax) and printed. Two electrophysiologists (EP1 and EP2) interpreted the intervals on original, faxed, and efaxed ECGs and intervals (RR, PR, and QT) were compared. A three-way analysis of variance to examine differences between raters, among ECG intervals, and among methods (repeated factor) was performed. Because no interaction terms were significant, a Duncan's multiple range test was used to evaluate where differences occurred among the three intervals and three methods, given these main effects were significant., Results:  The difference between raters EP1 and EP2 was not significant (P = 0.6681). Although the interval measurements of the faxed and efaxed ECGs were not significantly different from each other (P > 0.05), each was significantly different from the original across all three ECG intervals and both raters (P = 0.0138). The RR interval yielded mean (SD) values for the original, faxed, and efaxed methods of 0.6986 seconds (0.2074), 0.6646 seconds (0.1938), and 0.6838 seconds (0.1935), respectively. For the QT interval, the mean (SD) values for the original, faxed, and efaxed methods were 0.3370 seconds (0.0524), 0.32134 seconds (0.0466), and 0.3284 seconds (0.0515), respectively., Conclusions:  ECG transmission via facsimile or efax may introduce significant distortion of the intervals. Alternative means of sending ECGs for interpretation should be considered., (©2011, The Authors. Journal compilation ©2011 Wiley Periodicals, Inc.)

This report describes the use of a donor heart with ventricular pre-excitation for pediatric orthotopic heart transplantation and the successful surgical cryoablation of the donor heart prior to transplantation. The issues related to the preoperative evaluation and surgical management of the donor heart with Wolff-Parkinson White syndrome are discussed., (© 2011 The Authors Journal compilation © 2011 The American Society of Transplantation and the American Society of Transplant Surgeons.)

Objectives: Temporary epicardial pacing wires are commonly placed during pediatric cardiac surgery. Data are sparse on postoperative pacing in this population. The objective of this study was to determine the frequency of use and identify predictors for the use of temporary epicardial pacing wires., Methods: Perioperative data were prospectively collected on all patients who underwent cardiac surgery at our institution (n = 162)., Results: A total of 117 (72%) patients had temporary epicardial pacing wires placed. Postoperatively, 23 (20%) of 117 patients had hemodynamic improvement with the use of temporary epicardial pacing wires. Indications for pacing were slow junctional rhythm (11/23 [48%]), junctional ectopic tachycardia (7/23 [31%]), pace termination of supraventricular tachycardia (3/23 [13%]) and atrial flutter (1/23 [4%]), and complete heart block (1/23 [4%]). By using univariate analysis, single-ventricle anatomy, heterotaxy, the Fontan procedure, use of circulatory arrest, intraoperative arrhythmia, pacing in the operating room, and use of vasoactive medications were predictors for hemodynamic improvement with the use of temporary epicardial pacing wires (P < .05). On multivariate analysis, the Fontan procedure, circulatory arrest, and intraoperative arrhythmias were independent predictors (P < .01). When excluding all patients with any of these 3 risk factors, only 2% were paced. Patients with clinically significant pacing had longer chest tube drainage (P < .01) and intensive care unit length of stay (P < .01). There were no complications associated with temporary epicardial pacing wires., Conclusions: The Fontan procedure, use of circulatory arrest, and intraoperative arrhythmias were associated with hemodynamic improvement with postoperative pacing and might represent indications for empiric intraoperative placement of temporary epicardial pacing wires. Patients without these risk factors were less likely to require pacing. Temporary epicardial pacing wires were safe and useful in the management of arrhythmias after pediatric cardiac surgery., (Copyright © 2011 The American Association for Thoracic Surgery. Published by Mosby, Inc. All rights reserved.)

Remifentanil is commonly used during anesthesia in pediatric electrophysiologic studies (EPS). The purpose of this study is to determine the effects of remifentanil on the cardiac electrophysiologic properties of children undergoing ablation of supraventricular tachycardia (SVT). A prospective study was performed in patients undergoing EPS before ablation of SVT. Each patient received two different anesthetic protocols: protocol 1 = propofol (200 mcg/kg/min) and protocol 2 = propofol (120 mcg/kg/min) plus remifentanil (0.3 mcg/kg/min). EPS data were measured during the steady state of each protocol. Paired Student t test was performed for analysis of continuous data. All p values <0.05 were considered statistically significant. Fifteen patients were enrolled between April 2005 and January 2006. The mean age was 13.3 ± 2.9 years (range 6.7 to 17.7). Seven patients had atrioventricular (AV) nodal re-entry tachycardia; 5 patients had Wolff-Parkinson-White syndrome; 2 patients had a concealed accessory pathway; and 1 patient was not inducible. Of the 14 patients who underwent ablation, 13 (93%) achieved successful. The baseline sinus cycle length extended from 884 ± 141 ms during protocol 1 to 980 ± 165 ms during protocol 2 (p = 0.01), and the Wenckebach cycle length lengthened from 377 ± 96 ms to 406 ± 109 ms (p = 0.01). No other variables measured (atrial-His (AH) and His-ventricular (HV) interval, atrioventricular node (AVN), and atrial, ventricular, and accessory pathway effective refractory periods) changed significantly between the two different protocols. In pediatric patients undergoing EPS before ablation of SVT, remifentanil appears to slow both sinus and AV nodal function. These effects should be taken into consideration when performing EPS.

We report the hematologic and invasive electrophysiologic management of a 12-year-old boy with mild hemophilia A (factor VIII deficiency) and atrioventricular nodal reentrant tachycardia. Thoughtful preparation with detailed input from the patient's comprehensive hemophilia center combined with vigilant pericatheterization hematologic management allowed for safe and successful cryoablation of this arrhythmia. Strategies for the management of patients with bleeding disorders who require invasive cardiac catheterization or surgery are reviewed.

Background: Previous studies of patients with long QT syndrome (LQTS) and 2:1 atrioventricular block (AVB) have reported a mortality rate greater than 50% during infancy., Objective: The purpose of this study was to determine the outcome of this high-risk population in the current era., Methods: A retrospective study from four tertiary care pediatric centers assessed patients with congenital LQTS and 2:1 AVB from January 2000 to January 2009. All neonates who presented with 2:1 AVB and prolonged QTc unrelated to medication were included in the study. Statistical analysis was performed using a paired t-test. Medical records were reviewed for ECG findings, genotype, medications, and device therapy., Results: Twelve patients that met the inclusion criteria were identified. All patients underwent diagnostic ECG in the first 24 hours of life. The average QTc interval prior to therapy was 616 +/- 99 ms (range 531-840 ms). Over a follow-up period of 71 +/- 45 months (range 15-158 months), 11 of 12 patients received devices (8 permanent pacemaker, 3 implantable cardioverter-defibrillator). Average age of device placement was 48 months (median 2 months, range 3 days to 10.5 years). All patients were treated with beta-blockers; mexiletine was added in three patients, and mexiletine and flecainide were added in one patient. Three (25%) patients experienced torsades de pointes while receiving beta-blockers, one of which was refractory to medical therapy. This patient underwent left cardiac sympathetic denervation and implantable cardioverter-defibrillator placement. Genotyping was available for 6 (50%) patients (2 SCN5A mutation, 4 KCNH2 mutation). At last follow-up, no mortality was observed. Follow-up QTc intervals had decreased (mean 480 +/- 20 ms, range 450-507 ms, P <.002)., Conclusion: Management of patients with LQTS and 2:1 AVB presents unique challenges. Despite historical data indicating poor prognosis, our study represents a cohort of high-risk LQTS patients with a relatively optimistic outcome. This finding reflects early diagnosis and intervention, coupled with improved management strategies, in the current era., (Copyright (c) 2010 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

We present the case of an 11-year-old with D-transposition, double inlet left ventricle, and dextrocardia 8 years following an extracardiac Fontan with supraventricular tachycardia mediated by a concealed accessory pathway. A transbaffle puncture was performed with fluoroscopic and transesophageal echocardiography guidance and the pathway location as well as its proximity to the HIS bundle were identified. The pathway was successfully ablated and the patient is asymptomatic for 12 months postablation.

Background: In adults, transvenous implantable cardioverter defibrillator (ICD) lead failure rates are significant, and their occurrence increases with time from implant. There are limited data in children. The goal of this study was to assess lead survival in young patients undergoing ICD implantation at a single center., Methods: Records of patients under 21 years old with transvenous ICD leads implanted at our center from June 1997 to August 2007 were retrospectively reviewed. Age, weight, height, diagnosis, lead and generator model, venous access technique, generator position, pacing thresholds, lead impedance, and R wave size were recorded. "Lead failure" was defined as any lead problem requiring surgical intervention to restore proper function to the ICD system., Results: Seventy-one transvenous leads were included (70 patients). Average age at implant was 14.8 years (range 5.7-19.5). All the devices were implanted by a single operator (HMS). Venous access was obtained via cephalic cutdown in 66/71. Mean follow-up time was 2.8 years (range 0.2-7.8 years, median 2.3 years). There were no infections requiring explantation. There were four lead failures. Three were lead fractures, occurring 12, 13, and 19 months after implant. The fourth lead failed when an arrhythmia was not appropriately detected, and a second dedicated rate-sensing lead was thus implanted. Univariate analysis did not identify any variable to be a significant predictor of lead failure. Kaplan-Meier survival analysis demonstrated 5-year lead survival at 89.6%., Conclusions: ICD lead survival in children, when performed by an experienced operator, is similar to that found in adults.

In patients with pre-excitation, a short PR interval and a delta wave are not always clearly seen, particularly if the pre-excitation is mild. Absent septal Q waves have been used as additional evidence suggestive of pre-excitation. The purpose of the present study was to determine the incidence of normalization of septal Q waves after successful ablation of a manifest accessory pathway in pediatric patients with normal hearts. We performed a retrospective review of electrocardiograms (ECGs) obtained before and after successful catheter ablation of a single manifest accessory pathway in patients <21 years old (84 pairs of ECGs). The ECGs obtained in patients before ablation for atrioventricular nodal re-entry tachycardia were used as controls (n = 62). The absence of Q waves in the lateral leads (V(5) to V(7)) and inferior leads (II, III, aVF) were determined. p Values <0.05 were considered significant. Before the ablation, 72 ECGs (85%) demonstrated absent Q waves in the lateral leads, and only 17 (20%) did not show evidence of Q waves after successful ablation of the accessory pathway (p <0.001). On the inferior leads, 37 ECGs (44%) showed no evidence of Q waves before ablation compared to 24 (29%) after ablation (p <0.05). The findings on the postablation ECG were not statistically different from the findings on the ECGs of the control patients. In conclusion, Q waves in the lateral and inferior leads are often absent in patients with manifest pre-excitation. Absent septal Q waves in the lateral and inferior leads frequently normalize after successful ablation of an accessory pathway., (Copyright 2010 Elsevier Inc. All rights reserved.)

Epicardial pacing is the standard approach for permanent pacing in small children and patients with functionally univentricular physiology. The longevity of epicardial leads, however, is compromised by increased occurrences of exit block and lead fractures. We report our experience with a technique of placing a second ventricular lead, and attaching it to the atrial port of a dual chamber pacemaker to prevent the need for early re-operation in the event of failure of the primary epicardial lead. A retrospective review showed that, over the period from 2001 through 2007, epicardial ventricular pacemakers had been placed in 88 patients. In 6 of these, we had placed 2 ventricular leads, their median weight being 8.0 kilograms, with a range from 4.2 to 31.8 kilograms. Fracture of a lead occurred in 1 of the patients (17%) 8 months after placement, requiring reprogramming to pace from the atrial port. This possibility avoided the need for repeated emergent surgery. At a median follow-up of 1.5 years, with a range from 0.3 to 4.4 years, there have been no complications. During the same time period, overall failure of epicardial leads at our institution was 13%. Placement of a second ventricular epicardial pacing lead, attached to the atrial port of a dual chamber pacemaker, therefore, may provide a safe and effective means of ventricular pacing in the setting of epicardial lead failure, and may obviate the need for repeat, potentially urgent, pacemaker surgery.

Direct-current cardioversion is a common treatment modality for acute termination of atrial flutter in neonates. Studies in children have demonstrated that cardioversion is often successful with as little as 0.25-0.5 J/kg with the current biphasic devices. We hypothesize that during cardioversion of atrial flutter in neonates, however, the impedance may be high and more energy may be required for successful cardioversion. A retrospective chart review of our institutional experience from 2005 through 2008 was performed. Neonates with atrial flutter requiring cardioversion who had strips available for review were included. Six patients met the inclusion criteria. The median age at the time of cardioversion was 2.6 h (range, 1.3-336 h) and the mean weight was 3.22 +/- 0.4 kg (SD). The mean electrical impedance of the successful shocks was elevated, at 234 +/- 136 Omega. The mean energy delivered for successful cardioversion was 0.9 +/- 0.3 J/kg, and the current was 1 A in all patients. In conclusion, the shock impedance was elevated in the neonates studied during cardioversion of atrial flutter. Low current was sufficient for successful cardioversion. Further studies are needed in this specific population.

Objective: To report our experience with transcatheter occlusion of antegrade pulmonary blood flow (APF) for postoperative complications of cavopulmonary anastomosis (BCPA)., Background: It has been suggested that limited APF enhances pulmonary arterial growth in patients undergoing BCPA. However, APF may result in suboptimal postoperative hemodynamics and sequelae such as SVC syndrome or prolonged chest tube drainage. For this subgroup, closure of APF may alleviate these problems., Methods: All BCPA procedures where APF was left open from 1995-2005 were reviewed. Symptomatic patients with APF who underwent a cardiac catheterization in the postoperative period comprised the study cohort., Results: 179 BCPA procedures were performed during the study period. APF was left patent in 29/179. 6/29 patients (age 10-28 months, median 14 months) presented 12 to 130 day; (median 31 days) with persistent pleural effusions (5) or SVC syndrome (1, Five had a history of a previous pulmonary arterial band (PAB) and one pulmonary stenosis. PA pressure was elevated in all (range 17-27 mmHg; median 22 mmHg). Hemodynamic evaluation with temporary APF occlusion was repeated in all patients. APF was successfully closed in 4/6 patients. The Amplatzer POA occluder was used in 3 and the Amplatzer ASD occluder in 1. Pulmonary effusions resolved in all the patients who had transcatheter APF closure as did the case of SVC syndrome. There were no complications., Conclusion: Transcatheter APF occlusion seems both safe and feasible in patients with hemodynamic compromise following BCPA with residual APF. Temporary occlusion testing prior to permanent device closure is recommended., (Copyright 2008 Wiley-Liss, Inc.)

Background: The traditional first stage of palliation for functional single-ventricle lesions with transposition of the great vessels and systemic outflow tract obstruction has been either the Norwood or Sano procedure or the Damus-Kaye-Stansel procedure. There is limited literature on the use of an arterial switch procedure as the initial staged palliation for functional single ventricles in this setting. This study is an examination of our institutional experience with performing the palliative switch procedure with examination of suitability for Fontan completion and midterm outcome in these patients., Methods: This is a retrospective review of our institutional experience from October 1991 through August 2006 on single-ventricle patients with transposition of the great vessels and systemic outflow tract obstruction who underwent a palliative arterial switch procedure., Results: Nine patients underwent an initial palliative switch procedure. Six of 9 patients underwent completion of palliation with the Fontan procedure and are alive and well. One patient is well and is awaiting the next stage of palliation (78%). There was 1 early operative death (11%) and 1 late death (11%). There was 1 case of recoarctation (11%)., Conclusions: The palliative switch procedure appears a reasonable surgical option for patients with functional single-ventricle lesions, transposition of the great vessels, and systemic outflow tract obstruction. Patients who have undergone a palliative switch procedure are suitable candidates for completion of palliation with the Fontan procedure.

Background: Syncope due to episodes of paroxysmal atrioventricular (AV) block, defined as transient advanced second or third-degree block, is rarely reported in pediatric patients without congenital heart disease., Methods: We reviewed our institutional arrhythmia database from January 1988 to January 2007 to identify all patients less than 18 years of age with normal cardiac anatomy and episodes of syncope associated with paroxysmal AV block. Demographic and clinical information was collected., Results: Six patients were identified (Table I). Five of the six patients were female, with an average age of 9.3 +/- 4.4 years. Patients had episodes of syncope for an average of 5.6 +/- 3.3 years prior to diagnosis. All patients had normal physical examinations, electrocardiograms, and echocardiograms. None were on medications known to interfere with AV nodal function, and laboratory evaluation including Lyme titers were negative. Five of the six patients' episodes were atypical for vasovagal syncope (except patient 6). All patients had documented paroxysmal AV block on either inpatient cardiac monitor, Holter monitor, or event recorder at the time of syncope. There was maintenance or acceleration of the sinus rate during episodes of syncope in all patients (mean atrial rate 107 +/- 37 bpm). All six patients had permanent transvenous pacemakers implanted with resolution of symptoms over a mean follow-up of 5.2 +/- 6.3 years., Conclusion: Paroxysmal AV nodal block is a rare finding in pediatric patients, but should be considered as a possible etiology in patients presenting with episodes atypical for vasovagal syncope. Pacemaker therapy prevented future episodes in all six of our patients.

We report a case of an infant who developed transient complete heart block following aortic and mitral valve surgery. In the course of his recovery, he developed a variable morphology wide complex rhythm with intermittent narrow complex beats. Review of his initial postoperative electrocardiogram (ECG), which demonstrated a right bundle branch block, helped to clarify the rhythm.

Late onset of complete heart block is a potentially dangerous complication after open heart surgery for congenital heart disease. The characteristics of patients with late-onset heart block have not been well described. A retrospective review of a pacemaker database was done to identify patients who presented with new onset heart block between 1988 and 2006, after they had been discharged from the hospital after open heart surgery with normal AV conduction. Fifteen patients were identified. The age at the time of the last surgery before the onset of heart block was 2.0 +/- 3.2 years (range: 3 days to 10 years). Nine had a ventricular septal defect repair, four had an atrioventricular canal, and two other patients had other types of heart defect. The last EKG available for analysis before the onset of heart block had been obtained 5.1 +/- 6.5 years (range: 7 days to 16 years) after surgery. The symptoms at the time of presentation were variable. Four patients presented with fatigue or exercise intolerance, two with syncope, two with congestive heart failure, and one with irritability, and the remaining six patients were diagnosed during routine follow-up. The time between open heart surgery and placement of a permanent pacemaker was 6.8 +/- 7.3 years (range: 2 months to 19 years). There were seven patients in whom the onset of heart block was more than 6 years after surgery. Late onset of complete heart block after open heart surgery could be dangerous when presenting without warning. These data would support the notion that patients should be followed for life after repair of congenital heart defects, with special attention to the conduction system, particularly after repair of septal defects.

Background: SCN5A encodes the alpha-subunit (Na(v)1.5) of the principle Na(+) channel in the human heart. Genetic lesions in SCN5A can cause congenital long QT syndrome (LQTS) variant 3 (LQT-3) in adults by disrupting inactivation of the Na(v)1.5 channel. Pharmacological targeting of mutation-altered Na(+) channels has proven promising in developing a gene-specific therapeutic strategy to manage specifically this LQTS variant. SCN5A mutations that cause similar channel dysfunction may also contribute to sudden infant death syndrome (SIDS) and other arrhythmias in newborns, but the prevalence, impact, and therapeutic management of SCN5A mutations may be distinct in infants compared with adults., Methods and Results: Here, in a multidisciplinary approach, we report a de novo SCN5A mutation (F1473C) discovered in a newborn presenting with extreme QT prolongation and differential responses to the Na(+) channel blockers flecainide and mexiletine. Our goal was to determine the Na(+) channel phenotype caused by this severe mutation and to determine whether distinct effects of different Na(+) channel blockers on mutant channel activity provide a mechanistic understanding of the distinct therapeutic responsiveness of the mutation carrier. Sequence analysis of the proband revealed the novel missense SCN5A mutation (F1473C) and a common variant in KCNH2 (K897T). Patch clamp analysis of HEK 293 cells transiently transfected with wild-type or mutant Na(+) channels revealed significant changes in channel biophysics, all contributing to the proband's phenotype as predicted by in silico modeling. Furthermore, subtle differences in drug action were detected in correcting mutant channel activity that, together with both the known genetic background and age of the patient, contribute to the distinct therapeutic responses observed clinically., Significance: The results of our study provide further evidence of the grave vulnerability of newborns to Na(+) channel defects and suggest that both genetic background and age are particularly important in developing a mutation-specific therapeutic personalized approach to manage disorders in the young.

Carditis is a common manifestation of adult patients with Lyme disease affecting 4-10% of Lyme patients in the United States. However, children with Lyme disease rarely present with acute carditis. The management of pediatric patients with complete heart block (CHB) secondary to Lyme carditis has not been well described. We report the acute management of 2 pediatric patients that presented in CHB secondary to Lyme disease.

Background: Catheter ablation is the treatment of choice for atrioventricular nodal reentrant tachycardia (AVNRT) with a success rate of 95-98%. The appearance of junctional rhythm during radiofrequency (RF) application to the slow pathway has been consistently reported as a marker for the successful ablation of AVNRT. Ventriculoatrial (VA) conduction during junctional rhythm has been used by many as a surrogate marker of antegrade atrioventricular nodal (AVN) function. However, VA conduction may not be an accurate or consistent marker for antegrade AVN function and reliance on this marker may leave some patients at risk for antegrade AVN injury., Objective: The purpose of this study is to describe a technique to ensure normal antegrade AVN function during junctional rhythm at the time of RF catheter ablation of the slow pathway., Methods: Retrospective review of all patients less than 21 years old who underwent RF ablation for AVNRT at our institution from January 2002 to July 2005. During RF applications, immediately after junctional rhythm was demonstrated, RAP was performed to ensure normal antegrade AVN function. Postablation testing was performed to assess AVN function and tachycardia inducibility., Results: Fifty-eight patients underwent RF ablation of AVNRT during the study period. The mean age +/- SD was 14 +/- 3 years (range: 5-20 years). The weight was 53 +/- 15 Kg (range: 19-89 Kg). The preablation Wenckebach cycle length was 397 +/- 99 msec (range: 260-700 msec). Fifty-four patients had inducible typical AVNRT, and four patients had atypical tachycardia. The mean tachycardia cycle length +/- SD was 323 +/- 62 msec (range: 200-500 msec). Patients underwent of 8 +/- 7 total RF applications (median: 7; range 1 to 34), for a total duration of 123 +/- 118 seconds (median: 78 sec, range: 20-473 sec). Junctional tachycardia was observed in 52 of 54 patients. RAP was initiated during junctional rhythm in all patients. No patient developed any degree of transient or permanent AVN block. Following ablation, the Wenckebach cycle length decreased to 364 +/- 65 msec (P < 0.01). Acutely successful RF catheter ablation was obtained in 56 of 58 patients (96%)., Conclusion: Rapid atrial pacing during radiofrequency catheter ablation of the slow pathway is a safe alternative approach to ensure normal AVN function.

Background: Low-dose biphasic waveform cardioversion has been used for the termination of atrial arrhythmias in adult patients. The energy required for termination of atrial arrhythmias in pediatric patients is not known. The objective of this study is to determine the minimum energy required for successful external cardioversion of atrial arrhythmias in pediatric patients using biphasic waveform current., Methods: Prospective study of all patients less than 24 years of age with and without congenital heart disease undergoing synchronized cardioversion for atrial arrhythmias. Patients were assigned to receive an initial biphasic energy shock of 0.2-0.5 J/kg and if unsuccessful in terminating the arrhythmia, subsequent sequential shocks of 1 and 2 J/kg would be administered until cardioversion was achieved. The end point of the cardioversion protocol was successful cardioversion or delivery of three shocks., Results: Between June 2005 and June 2006, 16 patients underwent biphasic cardioversion for atrial flutter or fibrillation. The mean age was 14.7 +/- 6.4 years (range: 2 weeks to 24 years). The mean weight was 51 +/- 21 kg (range: 3.8-82 kg). Seven patients had normal cardiac anatomy, three had a single ventricle (Fontan), two had a Senning operation; the remaining four patients had varied forms of congenital heart disease. The median length of time that the patients were in tachycardia was 12 hours (range: 5 minutes to 2 months). Using either transthoracic echocardiography (TTE) or transesophageal echocardiography (TEE), no thrombi were identified in any patient. All patients were successfully cardioverted with biphasic waveform energy. The successful energy shock was 0.35 +/- 0.19 J/kg (range: 0.2-0.9 J/kg). All but one patient were successfully cardioverted with less than 0.5 J/kg. The transthoracic impedance range was between 41 and 144 Omega; one patient had an impedance of 506 Omega (2-week-old infant with a weight of 3.8 kg). The mean current delivered was 5.4 +/- 2.2 A (range: 1-11 A)., Conclusion: Low-dose energy using biphasic waveform shocks can be used for successful termination of atrial arrhythmias in pediatric patients with and without congenital heart disease.

Tracheal hemorrhage is a common occurrence in pediatric patients with long-term tracheotomies. The majority of these events are related to self-limited etiologies, such as granulation tissue or suction trauma. Tracheo-arterial fistula, however, represents a frequently fatal form of tracheal hemorrhage that may initially be difficult to distinguish from other causes. Previous reports have described the pathophysiology, presentation and management of tracheo-arterial fistula involving the innominate artery. We describe a case of a 21-month-old male with a history of significant congenital cardiac malformations and chronic tracheotomy tube dependence who presented with intermittent, brisk bleeding from the tracheotomy tube. He was ultimately diagnosed with and treated for an arterio-bronchial fistula from a major aorto-pulmonary collateral artery. We review the etiology and management of this disorder.

The Amplatzer Duct Occluder is a novel device designed to allow for the transcatheter closure of virtually all sized patent ductus arteriosuses. Prior technologies have been cumbersome and challenging to deploy with somewhat less than ideal closure rates associated with their use. This article summarizes the present knowledge about the Amplatzer Duct Occluder device and its various indications. With the introduction of this device as well as the use of embolization coils, all but the neonatal patent ductus arteriosuses can now be safely, consistently and successfully closed in the cardiac catheterization laboratory.

Epicardial pacing is frequently used in pediatric patients with congenital heart disease. Automatic threshold determination has been reported to be safe in epicardial lead systems. We report a case of falsely low ventricular thresholds determined by automatic capture verification in a patient with complete loss of capture due to a lead fracture.

Anomalous origin of the left coronary artery is a cause of sudden death in adolescents and young adults. Most commonly, it originates from the right coronary sinus or the pulmonary artery. Origin of the left main coronary artery from the non-coronary sinus of Valsalva is extremely rare. We report a case of a child with anomalous origin of the left main coronary artery from the non-coronary sinus diagnosed during the evaluation of a ventricular arrhythmia.

Objectives: We sought to review and report initial and one-year efficacy and safety results of the multicenter USA Amplatzer ductal occluder (ADO) device trial., Background: Transcatheter closure of a moderate to large patent ductus arteriosus (PDA) using conventional techniques is challenging. The ADO can close a PDA up to 12 mm in diameter., Methods: From September 1999 to June 2002, 484 patients were enrolled in 25 U.S. centers. Forty-five (9%) of 484 patients did not have ADO implantation, because the PDA was too small or because of elevated pulmonary resistance. The median age of the patients at catheterization was 1.8 years (range 0.2 to 70.7 years), and weight was 11 kg (range 4.5 to 164.5 kg)., Results: The median PDA minimal diameter was 2.6 mm (range 0.9 to 11.2 mm); 76 (17%) of 439 were larger than 4.0 mm. Median pulmonary artery mean pressure was 20 mm Hg (range 7 to 80 mm Hg). The ADO was implanted successfully in 435 (99%) of 439 patients, with a median fluoroscopy time of 7.1 min (range 2.9 to 138.4 min). Angiographic demonstration of occlusion was seen in 329 (76%) of 435. This increased to 384 (89%) of 433 on post-catheterization day 1, with occlusion documented in 359 (99.7%) of 360 at one year. At the last evaluation in all patients at any time, PDA closure was documented in 428 (98%) of 435 patients. There have been two cases of partial left pulmonary artery occlusion after ADO implantation and no cases of significant aortic obstruction., Conclusions: Moderate to large PDAs can be effectively and safely closed using the ADO device, with excellent initial and one-year results. This device should obviate the need for multiple coils or surgical intervention for these defects.

Successful transcatheter closure of a large PDA in a pregnant patient is reported using the Amplatzer ductal occluder device. This procedure was safe and uncomplicated, obviating the need for surgery in this high risk patient., (Copyright 2004 Wiley-Liss, Inc.)

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

Survival following cardiac transplantation in children and adults, including the group with complex congenital heart disease, has improved over the last decade secondary to medical and surgical advances in management. There have been rare reports of superior vena cava obstruction at anastomotic sites following transplantation. In patients following heart transplantation, venous stenosis can limit the ability to perform endomyocardial biopsies. We reviewed our experience in three patients who underwent cardiac transplantation and developed significant venous stenosis requiring intervention. All three were successfully treated by transcatheter implantation of endovascular stents. Endovascular stent implantation for venous obstruction in patients following cardiac transplantation was safe and effective, allowing improved ease of catheterization for future posttransplantation monitoring and surveillance., (Copyright 2002 Wiley-Liss, Inc.)

Endovascular stent implantation for pulmonary artery stenosis requires the use of a long, large-bore vascular sheath to insure precise implantation without embolization or malposition. A long vascular sheath may be difficult to position and usage may be associated with vascular compromise and/or hemodynamic embarrassment, especially in infants and small children. We report a new technique for pulmonary artery endovascular stent implantation without the use of a long sheath. From December 2000 to May 2001, 10 patients underwent implantation of 13 Palmaz Corinthian premounted biliary transhepatic stents for pulmonary artery stenosis. Median age was 0.8 years (range, 0.5-18.5) and median weight was 11.8 kg (range, 4.6-65). Patient diagnoses were tetralogy of Fallot (five), double outlet right ventricle (three), branch peripheral pulmonary artery stenosis (two), single ventricle s/p cavopulmonary shunt (one), and truncus arteriosus (one). All Palmaz Corinthian stents were delivered uncovered on Cordis Opta LP balloon catheters via short sheaths (6-7 Fr); super-stiff guidewires were not always necessary. These stents, with a maximal expanded diameter of 12 mm, were placed for peripheral pulmonary artery stenosis as a definitive procedure or at the pulmonary artery bifurcation in patients who were expected to undergo future open heart surgery. The stents were initially implanted on 4, 6, or 8 mm balloon catheters and further expanded if needed. Stents were placed in the right pulmonary artery alone in three patients, left pulmonary artery alone in four patients, and side-by-side stents were implanted simultaneously in three patients. All thirteen stents were implanted successfully in the desired location without stent malposition or embolization. Mean angiographic diameter increased from 2.5 +/- 1.5 to 5.7 +/- 1.4 mm (P < 0.01) and peak systolic ejection gradients decreased from 44 +/- 22 to 14 +/- 11.6 mm Hg (P < 0.01). The uncovered delivery of the premounted Palmaz Corinthian stent allowed for precise and safe endovascular stent implantation without the hemodynamic and technical problems associated with long vascular sheath usage. This technique is useful for the palliation of proximal pulmonary artery stenosis and is effective definitive treatment for peripheral pulmonary artery stenosis in small infants and children., (Copyright 2002 Wiley-Liss, Inc.)

Percutaneous access of the right internal jugular vein for coronary sinus cannulation in pediatric patients undergoing electrophysiologic studies may be technically difficult. We report the use of an ultrasound-guided technique for obtaining jugular venous access. Forty-five pediatric patients who underwent electrophysiologic study were analyzed. Access was obtained in 100 % of the patients using this technique with no major complications. Ultrasound guidance for access of the internal jugular vein for coronary sinus cannulation during electrophysiologic studies in pediatric patients, may increase the success rate and prevent the development of complications.

Background: The two major surgical approaches to the relief of bulboventricular foramen (BVF) obstruction in patients with single left ventricle (LV) are the Damus-Kaye-Stansel (DKS) procedure or direct BVF resection. Theoretical advantages of the DKS include better out-flow gradient relief, lower potential incidences of postoperative heart block and lower incidences of reoperation. Potential disadvantages of this approach include increased semilunar valvar insufficiency, lack of feasibility when attempting septation-type operations for univentricular hearts, and a technically more difficult operation. We report the results of direct surgical BVF resection., Methods: From June 1990 to June 1999, 9 patients had direct BVF resection performed at our institution. The median age at surgery was 16.5 years (range 1 month to 27 years). Diagnoses in these patients were [S,L,L] single LV (n = 8) and [S,D,D] single LV tricuspid atresia (n = 1). Eight of 9 patients had pulmonary artery bands placed either before BVF resection or at the same time as this procedure. Three patients required reoperation for reobstruction at the BVF (12 total operations in 9 patients)., Results: Median preoperative peak systolic gradient across the BVF measured at cardiac catheterization was 47 mm Hg (range 10 to 63 mm Hg). The median peak gradient measured by Doppler echocardiography was 44 mm Hg (range 5 to 125 mm Hg). Eight of 9 patients survived the operation to discharge from the hospital and 7 of 9 are alive at follow-up. At a median follow-up of 22 months (range 5 to 76 months), 8 of 8 surviving patients had an unobstructed BVF as determined by qualitative two-dimensional echocardiography and Doppler color flow imaging. There was one perioperative and one late death 5 months postoperatively (secondary to fungal sepsis). No patient developed new or worsened aortic insufficiency after BVF resection. Eight of 9 patients had no change in AV nodal conduction after surgery. One patient developed Mobitz II heart block requiring postoperative implantation of a pacemaker., Conclusions: Direct resection of an obstructive BVF can be performed with total relief of obstruction although reoperation may be required. Atrioventricular nodal function can be preserved in most patients with this operative approach, including those with [S,L,L] segmental anatomy.

Ventricular arrhythmias are uncommon in acute rheumatic carditis. We report the case of a child who presented with rheumatic carditis, prolonged corrected QT interval, and torsade de pointes. The episodes of torsade were controlled with beta-blockade and cardiac pacing. The child subsequently died as a result of brain injury; the autopsy revealed classic findings of acute rheumatic carditis.

Intravenous diltiazem was administered to 10 pediatric patients with primary atrial tachyarrhythmias with rapid ventricular response. Rapid, consistent, and safe temporary ventricular rate control was obtained in all patients given this medication.

Endomyocardial biopsy (EMB) is usually performed from the femoral veins in infants and small children. This requires the use of a long vascular sheath to direct a bioptome to the ventricular septum. We describe a technique of EMB in this population that obviates the need for the use of a long vascular sheath. A 5 Fr 0.038" internal diameter, no-sideholes Cobra catheter (Cook, Bloomington, IN) introduced via a 5 Fr short sheath was used to direct a 3 Fr, 60-cm-length Cook bioptome to the ventricular septum. From January 1998 to August 1999, this technique was used 22 times in seven patients for EMB (median, age 13 months; range, 1-72 months). Indications for EMB in this group were posttransplantation surveillance (21 times) and evaluation for cardiomyopathy/myocarditis (1). Median number of EMB specimens obtained per procedure was 6 (range, 5-9). There was one pneumopericardium seen post-EMB with this technique without hemodynamic embarrassment. EMB in infants and small children can be performed successfully, safely, and repeatedly from the femoral veins without the need for a long sheath.

Supraventricular tachyarrhythmias following the Fontan procedure can be life-threatening. Though most are commonly due to intraatrial reentry, orthodromic reentrant tachycardia may also be present. Atrioventricular accessory pathways may develop across suture lines following right atrial to right ventricular anastomosis in patients with tricuspid atresia. We report a case of a patient who underwent this type of Fontan who developed orthodromic reentrant tachycardia and heart failure. An electrophysiological study revealed the presence of an atrioventricular accessory pathway traversing the Fontan anastomosis suture line. Successful radiofrequency ablation of the accessory pathway led to control of the tachyarrhythmia and improvement of heart failure.