A Prospective Management Strategy for Heterotaxy Syndrome with Intestinal Rotation Abnormalities: Imaging Does Not Predict Need for Surgery.

PURPOSE: Heterotaxy syndrome (HS) affects right-left anatomical development in 3% of children with congenital heart disease. Commonly, these patients have intestinal rotation abnormalities (IRA) that differ from typical malrotation. In this prospective study, we examine the development of a management pathway, imaging findings, and clinical course of patients with HS and IRA. METHODS: After literature review, a multispecialty focus group designed a pathway for HS. Participants from a single institution were prospectively enrolled from 2016 to 2019. They underwent an abdominal ultrasound and UGI, however timing was variable based on symptoms. Symptomatic IRA was defined as feeding intolerance, bilious or non-bilious vomiting, bloating, severe reflux, and intermittent pain or abdominal distention. Screening for symptoms occurred every three months for the first two years and then annually. RESULTS: 18 participants were followed for a median of 5.0 years. Three clinical categories were identified: 1) asymptomatic, not requiring intestinal surgery, 72.2%, 2) symptomatic with feeding intolerance or failure to thrive requiring gastrostomy placement and diagnostic laparoscopy with Ladd procedure, 16.7%, and 3) symptomatic requiring urgent exploration for suspicion of volvulus, 11.1%. Need for surgery did not necessarily correlate with US and/or UGI findings. CONCLUSIONS: In children with HS and IRA, postnatal imaging did not inform the need for intestinal surgery. Although rare, volvulus or other forms of proximal obstruction can be anticipated, and symptomatic patients should be offered surgical intervention. A multidisciplinary care pathway for patients with HS and IRA can coordinate care and help counsel families on the likelihood of needing intestinal surgery for IRA. LEVEL OF EVIDENCE: Level II. TYPE OF STUDY: Prospective Cohort Study.

Ablation of intra-atrial reentrant tachycardias in adults with congenital heart disease: islands, isthmuses, channels, and walls.

PURPOSE OF REVIEW: The adult congenital heart patient population is rapidly growing due to increasing survival rates, and they often face chronic physiologic challenges as sequalae of both their defects and repairs. Among the most common sequalae are arrhythmias. Here we describe intra-atrial reentrant tachycardia (IART), one of the most commonly seen arrhythmias in the adult congenital heart population, and the approaches to successful ablation in adult congenital heart patients. RECENT FINDINGS: IART has increasing ablation success rates due to the increasing exposure of electrophysiologists to congenital cases, advances in technology, and the increasing application of both our pediatric congenital knowledge and adult acquired knowledge to the adult congenital population. SUMMARY: IART is a frequently seen arrhythmia in the adult congenital population, and it can have life-threatening consequences in the setting of congenital disease. Ablation techniques and treatment rates have improved over time, despite the challenges these cases present to clinicians; success of the ablation depends on careful, often creative, preplanning, and understanding of the complex individualized anatomy and circuits of the patient.

Atrial Fibrillation in Patients with Congenital Heart Disease.

Advances in surgical techniques have led to the survival of most patients with congenital heart disease (CHD) up to their adulthood. During their lifetime, many of them develop atrial tachyarrhythmias due to atrial dilatation and scarring from surgical procedures. More complex defects and palliative repairs are linked to a higher incidence and earlier occurrence of arrhythmias. Atrial fibrillation (AF) is common in patients who have atrial septal defects repaired after age 55 and in patients with tetralogy of Fallot repaired after age 45. Patients with dextrotransposition of the great arteries who undergo Mustard or Senning atrial switch procedures have an increased risk of atrial flutter due to atrial baffle suture lines. Patients with Ebstein's anomaly are also prone to supraventricular tachycardias caused by accessory bypass tracts. Patients with a single ventricle who undergo Fontan palliation are at risk of developing persistent or permanent AF due to extreme atrial enlargement and hypertrophy. In addition, obtaining vascular access to the pulmonary venous atrium can present unique challenges during radiofrequency ablation for patients with a Fontan palliation. Patients with cyanotic CHD who develop AF have substantial morbidity because of limited hemodynamic reserve and a high viscosity state. Amiodarone is an effective therapy for patients with arrhythmias from CHD, but its use carries long-term risks for toxicity. Dofetilide and sotalol have good short-term effectiveness and are reasonable alternatives to amiodarone. Pulmonary vein isolation is associated with better outcomes in patients taking antiarrhythmic medications. Anticoagulants are challenging to prescribe for patients with CHD because of a lack of data that can be extrapolated to this patient population. Surgical ablation is the gold standard for invasive rhythm control in patients with CHD and should be considered at the time of surgical repair or revision of congenital heart defects. When possible, patients with complex CHD should be referred for care to an adult congenital heart disease center of excellence.

Management of pediatric tachyarrhythmias on mechanical support.

BACKGROUND: Pediatric patients with persistent arrhythmias may require mechanical cardiopulmonary support. We sought to classify the population, spectrum, and success of current treatment strategies. METHODS AND RESULTS: A multicenter retrospective chart review was undertaken at 11 sites. Inclusion criteria were (1) patients <21 years, (2) initiation of mechanical support for a primary diagnosis of arrhythmias, and (3) actively treated on mechanical support. A total of 39 patients were identified with a median age of 5.5 months and median weight of 6 kg. A total of 69% of patients were cannulated for supraventricular tachycardia with a median rate of 230 beats per minute. A total of 90% of patients were supported with extracorporeal membrane oxygenation for an average of 5 days. The remaining 10% were supported with ventricular assist devices for an average of 38 (20-60) days. A total of 95% of patients were treated with antiarrhythmics, with 43% requiring >1 antiarrhythmic. Amiodarone was the most frequently used medication alone or in combination. A total of 33% patients underwent electrophysiology study/transcatheter ablation. Radiofrequency ablation was successful in 9 patients on full flow extracorporeal membrane oxygenation with 3 radiofrequency-failures/conversion to cryoablation. One patient underwent primary cryoablation. A total of 15% of complications were related to electrophysiology study/ablation. At follow-up, 23 patients were alive, 8 expired, and 8 transplanted. CONCLUSIONS: Younger patients were more likely to require support in the presented population. Most patients were treated with antiarrhythmics and one third required electrophysiology study/ablation. Radiofrequency ablation is feasible without altering extracorporeal membrane oxygenation flows. There was a low frequency of acute adverse events in patients undergoing electrophysiology study/ablation, while on extracorporeal membrane oxygenation.

Wearable cardioverter-defibrillator use in patients perceived to be at high risk early post-myocardial infarction.

OBJECTIVES: The aim of this study was to describe usage of the wearable cardioverter-defibrillator (WCD) during mandated waiting periods following myocardial infarction (MI) for patients perceived to be at high risk for sudden cardiac arrest (SCA). BACKGROUND: Current device guidelines and insurance coverage require waiting periods of either 40 days or 3 months before implanting a cardioverter-defibrillator post-myocardial infarction (MI), depending on whether or not acute revascularization was undertaken. METHODS: We assessed characteristics of and outcomes for patients who had a WCD prescribed in the first 3 months post-MI. The WCD medical order registry was searched for patients who were coded as having had a "recent MI with ejection fraction ≤35%" or given an International Classification of Diseases, Ninth Revision 410.xx diagnostic code (acute MI), and then matched to device-recorded data. RESULTS: Between September 2005 and July 2011, 8,453 unique patients (age 62.7 ± 12.7 years, 73% male) matched study criteria. A total of 133 patients (1.6%) received 309 appropriate shocks. Of these patients, 91% were resuscitated from a ventricular arrhythmia. For shocked patients, the left ventricular ejection fraction (LVEF) was ≤30% in 106, 30% to 35% in 17, >36% in 8, and not reported in 2 patients. Of the 38% of patients not revascularized, 84% had a LVEF ≤30%; of the 62% of patients revascularized, 77% had a LVEF ≤30%. The median time from the index MI to WCD therapy was 16 days. Of the treated patients, 75% received treatment in the first month, and 96% within the first 3 months of use. Shock success resulting in survival was 84% in nonrevascularized and 95% in revascularized patients. CONCLUSIONS: During the 40-day and 3-month waiting periods in patients post-MI, the WCD successfully treated SCA in 1.4%, and the risk was highest in the first month of WCD use. The WCD may benefit individual patients selected for high risk of SCA early post-MI.

Unusually high association of hypertrophic cardiomyopathy and complex heart defects in children with fasciculoventricular pathways.

INTRODUCTION: Fasciculoventricular pathways (FVPs) are rare causes of preexcitation that do not mediate tachycardias. We report a two-center experience of pediatric patients with FVP and an unexpectedly high association of complex congenital heart defects (CHDs), chromosomal anomalies, and hypertrophic cardiomyopathy. METHODS: A retrospective review of the electrophysiology database at two institutions was performed to identify patients with FVP from January 2000 to January 2011. Medical records of these patients were reviewed for clinical history and course, presence of comorbidities, and details of intracardiac electrophysiology (EP) study. RESULTS: A total of 17 patients were identified. The primary indication for EP study was a preexcitation pattern on electrocardiogram. The majority of patients, 12/17 (71%), were found to have associated cardiac and genetic anomalies. Hypertrophic cardiomyopathy was found in 5/17 (29%) patients, with genetic testing in two patients demonstrating the lysosomal-associated membrane protein 2 mutation (Danon syndrome). Underlying complex CHDs were present in 3/17 (18%) patients. One patient (6%) was status post (s/p) cardiac transplant, one patient had hypertension, and another had Trisomy 21. Other electrophysiologic substrates mediating tachycardia were found in 3/17 (18%) patients. Only 5/17 patients (29%) were otherwise healthy with structurally normal hearts. CONCLUSIONS: In this largest reported series of FVP in children, there is an unusually high association of FVP with complex CHDs, chromosomal anomalies, and hypertrophic cardiomyopathy. Any patient with such disorders and manifest preexcitation should be evaluated with a high index of suspicion for a FVP.

Electrophysiologic substrate and intraventricular left ventricular dyssynchrony in nonischemic heart failure patients undergoing cardiac resynchronization therapy.

BACKGROUND: Electrocardiographic imaging (ECGI) is a method for noninvasive epicardial electrophysiologic mapping. ECGI previously has been used to characterize the electrophysiologic substrate and electrical synchrony in a very heterogeneous group of patients with varying degrees of coronary disease and ischemic cardiomyopathy. OBJECTIVE: The purpose of this study was to characterize the left ventricular electrophysiologic substrate and electrical dyssynchrony using ECGI in a homogeneous group of nonischemic cardiomyopathy patients who were previously implanted with a cardiac resynchronization therapy (CRT) device. METHODS: ECGI was performed during different rhythms in 25 patients by programming their devices to biventricular pacing, single-chamber (left ventricular or right ventricular) pacing, and native rhythm. The electrical dyssynchrony index (ED) was computed as the standard deviation of activation times at 500 sites on the LV epicardium. RESULTS: In all patients, native rhythm activation was characterized by lines of conduction block in a region with steep activation-recovery interval (ARI) gradients between the epicardial aspect of the septum and LV lateral wall. A native QRS duration (QRSd) >130 ms was associated with high ED (≥30 ms), whereas QRSd <130 ms was associated with minimal (25 ms) to large (40 ms) ED. CRT responders had very high dyssynchrony (ED = 35.5 ± 3.9 ms) in native rhythm, which was significantly lowered (ED = 23.2 ± 4.4 ms) during CRT. All four nonresponders in the study did not show significant difference in ED between native and CRT rhythms. CONCLUSION: The electrophysiologic substrate in nonischemic cardiomyopathy is consistent among all patients, with steep ARI gradients co-localizing with conduction block lines between the epicardial aspect of the septum and the LV lateral wall. QRSd wider than 130 ms is indicative of substantial LV electrical dyssynchrony; however, among patients with QRSd <130 ms, LV dyssynchrony may vary widely.

Use of a wearable automated defibrillator in children compared to young adults.

BACKGROUND: A wearable automated external defibrillator has been shown to be efficacious in the prevention of sudden death in adults who had a history of cardiac arrest but who did not have a permanent internal cardioverter/defibrillator (ICD) placed. The use of a wearable defibrillator has not been established in the pediatric population. METHODS: We retrospectively reviewed the clinical database for the wearable external defibrillator from ZOLL Lifecor Corporation (Pittsburgh, PA, USA). We compared the use of the wearable defibrillator in patients ≤18 years of age to those aged 19-21 years. RESULTS: There were 81 patients ≤18 years of age (median age = 16.5 years [9-18] and 52% male). There were 103 patients aged 19-21 years (median age = 20 years [19-21] and 47% male). There was no difference between groups in average hours/day or in total number of days the patients wore the defibrillator. In patients ≤18 years of age, there was one inappropriate therapy and one withholding of therapy due to a device-device interaction. In patients aged 19-21 years, there were five appropriate discharges in two patients and one inappropriate discharge in a single patient. CONCLUSION: It is reasonable to consider the wearable automated external defibrillator as a therapy for pediatric patients who are at high risk of sudden cardiac arrest but who have contraindications to or would like to defer placement of a permanent ICD. As there were no appropriate shocks in our patients ≤18 years of age, this study cannot address efficacy of the therapy.

Cryoablation with an 8-mm tip catheter for pediatric atrioventricular nodal reentrant tachycardia is safe and efficacious with a low incidence of recurrence.

BACKGROUND: Cryoablation with 4- and 6-mm tip ablation catheters has been demonstrated to be safe and effective in the treatment of atrioventricular nodal reentrant tachycardia (AVNRT) in pediatric patients, albeit with a higher rate of clinical recurrence. Limited information is available regarding efficacy, mid-term outcomes, and complications related to the use of the 8-mm Freezor Max Cryoablation catheter (Medtronic, Minneapolis, MN, USA) in pediatric patients. METHODS: We performed a retrospective review of all pediatric patients with normal cardiac anatomy who underwent an ablation procedure for treatment of AVNRT using the 8-mm tip Cryoablation catheter at three large pediatric academic arrhythmia centers. RESULTS: Cryoablation with an 8-mm tip catheter was performed in 77 patients for treatment of AVNRT (female n = 40 [52%], age 14.8 +/- 2.2 years, weight 62.0 +/- 13.9 kg). Initial procedural success was achieved in 69 patients (69/76, 91%). Transient second- or third-degree atrioventricular (AV) block was noted in five patients (6.5%). There was no permanent AV block. Of the patients successfully ablated with Cryotherapy, there were two recurrences (2/70, 2.8%) over a follow-up of 11.6 +/- 3.3 months. CONCLUSION: Cryoablation with an 8-mm tip ablation catheter is both safe and effective with a low risk of recurrence for the treatment of AVNRT in pediatric patients.

Tachyarrhythmias after pediatric heart transplantation.

BACKGROUND: Tachyarrhythmias in pediatric post-heart transplant patients are not well defined. In this study we sought to further characterize these arrhythmias in terms of presentation, course, and outcome. METHODS: This investigation was a retrospective review of heart transplant recipients at St. Louis Children's Hospital during the period of 1991 to 2006. Patients were excluded if they were >18 years at transplantation or if follow-up information was unavailable. Patients with tachyarrhythmias beyond the first 2 weeks post-transplant were identified. RESULTS: Twenty-eight tachyarrhythmias occurred in 25 of 237 heart transplant recipients. Freedom from arrhythmia was 92% at 1-year post-transplant and 86% at 15 years post-transplant. Intra-atrial reentry tachycardia (12 patients) and ectopic atrial tachycardia (10 patients) were the most common arrhythmias. Rejection was found in 3 (12%) and previously unrecognized coronary disease was found in another 2 (8%) at the time of presentation with arrhythmia. Fifteen of 25 (60%) were asymptomatic at presentation, but 4 of 25 (16%) presented with heart failure, including 3 without evidence of rejection. No risk factors for developing arrhythmia were identified. Twenty-one arrhythmias resolved with brief pharmacologic or no therapy. Only 3 had a recurrence after the initial arrhythmia. Five patients underwent catheter ablation. CONCLUSIONS: Our experience suggests that the presence of tachyarrhythmias after pediatric heart transplantation is not rare and usually not associated with rejection. Pediatric heart transplant recipients have a higher incidence of ectopic atrial tachycardia (EAT) than their adult counterparts. Most tachyarrhythmias resolve after a relatively brief period of medical treatment and recurrence is uncommon.

Cardiac resynchronization therapy in pediatric congenital heart disease: insights from noninvasive electrocardiographic imaging.

BACKGROUND: Electrocardiographic imaging (ECGI) is a novel electrophysiologic imaging modality that may help guide patient selection and lead placement for cardiac resynchronization therapy (CRT). OBJECTIVE: The purpose of this study was to apply noninvasive ECGI to pediatric heart failure patients with congenital heart disease (CHD) undergoing evaluation for CRT. METHODS: ECGI was applied in eight patients with CHD who were either being evaluated for CRT or undergoing CRT. An electrical dyssynchrony (ED) index was computed from the ECGI epicardial activation maps as the standard deviation of activation times at 500 epicardial sites of the systemic ventricle. A normal ED of 20 +/- 4 ms was calculated from a control group of normal pediatric patients. RESULTS: Four patients had an ECGI assessment for ED but did not undergo CRT implant. Two other patients had ECGI assessment pre-CRT that demonstrated abnormal ED and went on to CRT implant. In both cases, the resynchronization lead was placed at the site of latest electrical activation (as determined by ECGI) in pre-CRT baseline rhythm. A total of four patients (two responders, two nonresponders) were studied with post-CRT in multiple rhythms. Responders had an average ED of 22 ms in optimal CRT conditions. The nonresponder had very elevated ED (37 ms) in all rhythms including optimal CRT settings. ED and ECG QRS duration showed weak correlation (r = 0.58). CONCLUSIONS: ECGI can be used in pediatric heart failure patients to evaluate ventricular ED and identify suitable candidates for CRT. In addition, ECGI can guide resynchronization lead placement to the area of latest electrical activation. It could also be used in noninvasive follow-ups for assessing synchrony and the electrophysiological substrate over time.

Therapeutic options in hypertrophic cardiomyopathy: a pediatric perspective.

Hypertrophic cardiomyopathy (HCM) is the most prevalent genetic cardiomyopathy in children and young adults. Despite advances in understanding the molecular etiology of this disorder, the clinical phenotypes vary widely from asymptomatic septal hypertrophy, to frank congestive heart failure due to left ventricular outflow tract obstruction (LVOTO), to unexpected sudden cardiac death. Thus, isolating a specific genetic defect in this disease does little to predict the clinical consequence. This is best seen in large families with several people affected by HCM who all have the identical mutation but who may have very different clinical phenotypes. Evaluating individuals with HCM consists of establishing the diagnosis through cardiac imaging, noninvasively assessing the risk for sudden death, and medically or surgically treating symptomatic LVOTO when it is present.

Markers of coronary sinus accessory pathways in pediatrics.

INTRODUCTION: Coronary sinus accessory pathways (CSAPs), atrioventricular connections formed by the coronary sinus myocardial coat, have been described in adult patients, but not systematically described in pediatric patients. METHODS: Patients who underwent CSAP ablation were compared to patients with right posteroseptal (RPS) pathway ablation (control group) from November 2004 to June 2007. Retrospective reviews of preablation 12-lead electrocardiogram (EKG), fluoroscopic, and intracardiac electrogram data were then performed to identify electrophysiologic markers of CSAP. RESULTS: A total of 23 patients were identified: 13 with CSAP and 10 with RPS pathways. Preablation EKGs demonstrated preexcitation in 8/10 (80%) patients with RPS pathways versus 9/13 (69%) patients with CSAP (P = 0.66). Preexcitation with a negative delta wave in lead II was seen in 5/9 (56%) patients with CSAP versus 0/8 in RPS (P = 0.029), and preexcitation with a positive delta wave in augmented vector right (aVR) was seen in 9/9 (100%) patients with CSAP versus 3/8 (37.5%) with RPS (P = 0.009). Accessory pathway (AP) potentials were seen on the coronary sinus (CS) catheter in 6/13 (46%) of CSAP and in 0 RPS ablations (P = 0.019). Recurrence of tachycardia occurred in 5/13 (38%) of patients with CSAP and 1/10 (10%) of patients with RPS pathways (P = 0.18). CONCLUSIONS: CSAPs should be considered when preablation EKG demonstrates preexcitation with a negative delta wave in lead II and a positive delta wave in aVR, and if an AP potential is seen on the CS catheter. Recurrence of tachycardia postablation or the need for multiple ablations should raise suspicion for a CSAP.

A fatal device-device interaction between a wearable automated defibrillator and a unipolar ventricular pacemaker.

We report a fatal device-device interaction between a wearable automated defibrillator (WAD; LifeVest - LifeCor, Inc., Pittsburgh, PA, USA) and a unipolar pacemaker that occurred in an 18-year-old patient listed for cardiac transplantation due to his failing Fontan. The patient developed ventricular tachycardia that was initially detected by the WAD. However, large unipolar pacing artifacts and specific WAD arrhythmia detection algorithms caused the WAD to revert to nonrecognition of the arrhythmia, which lead to the patient's death. We identify likely causes of the failure and suggest methods of preventing such occurrences in the future.

Cardiac memory in patients with Wolff-Parkinson-White syndrome: noninvasive imaging of activation and repolarization before and after catheter ablation.

BACKGROUND: Cardiac memory refers to a change in ventricular repolarization induced by and persisting for minutes to months after cessation of a period of altered ventricular activation (eg, resulting from pacing or preexcitation in patients with Wolff-Parkinson-White syndrome). ECG imaging (ECGI) is a novel imaging modality for noninvasive electroanatomic mapping of epicardial activation and repolarization. METHODS AND RESULTS: Fourteen pediatric patients with Wolff-Parkinson-White syndrome and no other congenital disease, were imaged with ECGI a day before and 45 minutes, 1 week, and 1 month after successful catheter ablation. ECGI determined that preexcitation sites were consistent with sites of successful ablation in all cases to within a 1-hour arc of each atrioventricular annulus. In the preexcited rhythm, activation-recovery interval (ARI) was the longest (349+/-6 ms) in the area of preexcitation leading to high average base-to-apex ARI dispersion of 95+/-9 ms (normal is approximately 40 ms). The ARI dispersion remained the same 45 minutes after ablation, although the activation sequence was restored to normal. ARI dispersion was still high (79+/-9 ms) 1 week later and returned to normal (45+/-6 ms) 1 month after ablation. CONCLUSIONS: The study demonstrates that ECGI can noninvasively localize ventricular insertion sites of accessory pathways to guide ablation and evaluate its outcome in pediatric patients with Wolff-Parkinson-White syndrome. Wolff-Parkinson-White is associated with high ARI dispersion in the preexcited rhythm that persists after ablation and gradually returns to normal over a period of 1 month, demonstrating the presence of cardiac memory. The 1-month time course is consistent with transcriptional reprogramming and remodeling of ion channels.

Hypertrophic cardiomyopathy with preexcitation: insights from noninvasive electrocardiographic imaging (ECGI) and catheter mapping.

UNLABELLED: Hypertrophic Cardiomyopathy and Preexcitation. INTRODUCTION: Fasciculoventricular pathway has been described as an unusual variant of preexcitation. Electrocardiographic imaging (ECGI) is a novel imaging modality for noninvasive electroanatomic mapping of epicardial activation and repolarization. CASE: We present a case of an 18-year-old male with hypertrophic cardiomyopathy (HCM) and an electrocardiogram (ECG)-based diagnosis of Wolff-Parkinson-White (WPW) syndrome, who underwent a noninvasive ECGI study to image ventricular activation, followed by an electrophysiology study (EPS). The ECGI electroanatomic isochrone map showed early activation of the epicardial aspect of the atrioventricular (A-V) groove and an aberrant posterior-base-to-apex progression of activation in the left ventricular (LV) epicardium. The EPS showed a likely fasciculoventricular pathway (FVP) without any inducible tachycardia. CONCLUSION: While FVP has been described before, this is the first report of detailed quantitative three-dimensional characterization of electrical activation sequence of a heart with this type of preexcitation, using a novel noninvasive imaging modality (ECGI). In spite of abnormal ventricular activation, the EPS demonstrated that the FVP is not capable of supporting reentrant supraventricular tachycardia or rapidly conducted atrial fibrillation.

Experience and results during transition from radiofrequency ablation to cryoablation for treatment of pediatric atrioventricular nodal reentrant tachycardia.

BACKGROUND: Cryoablation has emerged as a new, theoretically safer, modality for treating atrioventricular nodal reentrant tachycardia (AVNRT). The purpose of this study is to compare procedural aspects and outcomes during the transition from radiofrequency (RF) ablation to cryoablation for pediatric AVNRT. METHODS: Data were obtained retrospectively from 80 consecutive pediatric patients who underwent AVNRT ablation from 10/2001- 4/2006 (RF n = 42, Cryo n = 38). Statistical analysis was performed using unpaired t-test, chi-square test, and analysis of variance. RESULTS: RF ablations were performed anatomically in NSR while three different mapping techniques were used during cryoablation: ablation during AVNRT (26%), anatomic in NSR (48%), and anatomic with S(1) S(2) pacing (26%). There was no difference in the number or duration of lesions between the three cryo subgroups. Acute success was obtained in 95% of RF and 97% of cryo cases. There was no difference in the number of total, mapping, or full-duration lesions between the RF and cryogroups. Despite accounting for longer cryolesion time, total ablation time (P < 0.001), mapping time (P = 0.002), and full duration lesion time (P < 0.001) were longer in the cryogroup. There was no significant difference in total procedure time; fluoroscopy time was shorter in the cryoablation group (P = 0.049). There was one confirmed recurrence of tachycardia in each group with a 2% recurrence rate. CONCLUSIONS: Cryoablation for treatment of pediatric AVNRT is as safe and efficacious as RF ablation. Although cryolesions are intrinsically longer in duration, total procedure times were not increased and fluoroscopy times were decreased compared to RF.

Alternative delivery of a 4Fr lumenless pacing lead in children.

BACKGROUND: The potential advantages of using a 4Fr lumenless pacing lead (3830 SelectSecure, Medtronic Inc, Minneapolis, MN, USA) in children are largely negated due to the large size of the delivery system. Here we describe an innovative, sheath guided, delivery technique using conventional 5F sheaths. METHODS: Transvenous access was obtained via the left cephalic or axillary vein. A 5Fr introducer set with a 45 degrees curved tip (CheckFlo Performer Introducer Set with the Children's Hospital Boston Modification, Cook Medical Inc, Bloomington, IN, USA) was placed over a wire into the right atrium (RA) or right ventricle (RV). The sheath was modified by cutting off the valved end and a SelectSecuretrade mark lead was introduced through the sheath. Rotating the sheath provided steerability and allowed for precise placement of the lead. After successful lead placement, the sheath was removed with a universal sheath splitter. RESULTS: We placed seven atrial and six ventricular leads in eight patients during nine separate cases with this method. Patient ages and weights ranged from 5 to 16 years and 16 to -59 kg respectively. Pacing thresholds were excellent at implant. Leads were placed successfully in all attempts. There were no procedural complications. One patient had leads placed twice; both lead systems were removed for suspected infection. Over short-term follow-up in five patients, lead position and characteristics have remained stable. CONCLUSION: Delivery of the SelectSecure lead in children can be successfully and precisely performed using a modified 5Fr sheath obviating the need for a large steerable delivery system.