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Cardiac amyloidosis is a rare cause of cardiomyopathy, reported exclusively in adults. We report the first known case presenting in childhood. A 12-year-old boy presented with syncope and diagnosed with ventricular non-compaction by echocardiography. Eventual genetic testing confirmed a TTR gene mutation associated with hereditary transthyretin amyloidosis.

In view of the increasing complexity of both cardiovascular implantable electronic devices (CIEDs) and patients in the current era, practice guidelines, by necessity, have become increasingly specific. This document is an expert consensus statement that has been developed to update and further delineate indications and management of CIEDs in pediatric patients, defined as ≤21 years of age, and is intended to focus primarily on the indications for CIEDs in the setting of specific disease categories. The document also highlights variations between previously published adult and pediatric CIED recommendations and provides rationale for underlying important differences. The document addresses some of the deterrents to CIED access in low- and middle-income countries and strategies to circumvent them. The document sections were divided up and drafted by the writing committee members according to their expertise. The recommendations represent the consensus opinion of the entire writing committee, graded by class of recommendation and level of evidence. Several questions addressed in this document either do not lend themselves to clinical trials or are rare disease entities, and in these instances recommendations are based on consensus expert opinion. Furthermore, specific recommendations, even when supported by substantial data, do not replace the need for clinical judgment and patient-specific decision-making. The recommendations were opened for public comment to Pediatric and Congenital Electrophysiology Society (PACES) members and underwent external review by the scientific and clinical document committee of the Heart Rhythm Society (HRS), the science advisory and coordinating committee of the American Heart Association (AHA), the American College of Cardiology (ACC), and the Association for European Paediatric and Congenital Cardiology (AEPC). The document received endorsement by all the collaborators and the Asia Pacific Heart Rhythm Society (APHRS), the Indian Heart Rhythm Society (IHRS), and the Latin American Heart Rhythm Society (LAHRS). This document is expected to provide support for clinicians and patients to allow for appropriate CIED use, appropriate CIED management, and appropriate CIED follow-up in pediatric patients.

In view of the increasing complexity of both cardiovascular implantable electronic devices (CIEDs) and patients in the current era, practice guidelines, by necessity, have become increasingly specific. This document is an expert consensus statement that has been developed to update and further delineate indications and management of CIEDs in pediatric patients, defined as ≤21 years of age, and is intended to focus primarily on the indications for CIEDs in the setting of specific disease categories. The document also highlights variations between previously published adult and pediatric CIED recommendations and provides rationale for underlying important differences. The document addresses some of the deterrents to CIED access in low- and middle-income countries and strategies to circumvent them. The document sections were divided up and drafted by the writing committee members according to their expertise. The recommendations represent the consensus opinion of the entire writing committee, graded by class of recommendation and level of evidence. Several questions addressed in this document either do not lend themselves to clinical trials or are rare disease entities, and in these instances recommendations are based on consenus expert opinion. Furthermore, specific recommendations, even when supported by substantial data, do not replace the need for clinical judgment and patient-specific decision-making. The recommendations were opened for public comment to Pediatric and Congenital Electrophysiology Society (PACES) members and underwent external review by the scientific and clinical document committee of the Heart Rhythm Society (HRS), the science advisory and coordinating committee of the American Heart Association (AHA), the American College of Cardiology, (ACC) and the Association for European Paediatric and Congenital Cardiology (AEPC). The document received endorsement by all the collaborators and the Asia Pacific Heart Rhythm Society (APHRS), the Indian Heart Rhythm Society (IHRS), and the Latin American Heart Rhythm Society (LAHRS). This document is expected to provide support for clinicians and patients to allow for appropriate CIED use, appropriate CIED management, and appropriate follow-up in pediatric patients.

Background: Pacing sites vary among symptomatic patients with congenital complete heart block (CHB) with right ventricle (RV) apex (Ap) and outflow tract (OT), both of which alter contractility, as commonly-cited lead implant locations. However, controversy exists as to the best site based on only ECHO-derived ejection fraction (EF) as a marker for contractility. With recent ECHO updates, the question now arises if use of other indices of left (L) V function offer advantages in comparing function between pacing sites. Objective: To compare newer LV functional ECHO …

Guidelines for the implantation of cardiac implantable electronic devices (CIEDs) have evolved since publication of the initial ACC/AHA pacemaker guidelines in 1984 [ 1 ]. CIEDs have evolved to include novel forms of cardiac pacing, the development of implantable cardioverter defibrillators (ICDs) and the introduction of devices for long term monitoring of heart rhythm and other physiologic parameters. In view of the increasing complexity of both devices and patients, practice guidelines, by necessity, have become increasingly specific. In 2018, the ACC/AHA/HRS published Guidelines on the Evaluation and Management of Patients with Bradycardia and Cardiac Conduction Delay [ 2 ], which were specific recommendations for patients >18 years of age. This age-specific threshold was established in view of the differing indications for CIEDs in young patients as well as size-specific technology factors. Therefore, the following document was developed to update and further delineate indications for the use and management of CIEDs in pediatric patients, defined as ≤21 years of age, with recognition that there is often overlap in the care of patents between 18 and 21 years of age. This document is an abbreviated expert consensus statement (ECS) intended to focus primarily on the indications for CIEDs in the setting of specific disease/diagnostic categories. This document will also provide guidance regarding the management of lead systems and follow-up evaluation for pediatric patients with CIEDs. The recommendations are presented in an abbreviated modular format, with each section including the complete table of recommendations along with a brief synopsis of supportive text and select references to provide some context for the recommendations. This document is not intended to provide an exhaustive discussion of the basis for each of the recommendations, which are further addressed in the comprehensive PACES-CIED document [ 3 ], with further data easily accessible in electronic searches or textbooks.

Symptomatic, circulatory collapse occurred in an unvaccinated child with repaired congenital heart and a backup pacemaker during an Influenza B viral infection with complete atrioventricular block and pacemaker non-capture. Ventricular arrhythmias occurred during her collapse. Atrioventricular conduction recovered within 24 hours. Influenza-associated cardiac inflammation can adversely affect patients with repaired CHD. Proactive immunisation is strongly recommended.

Although postoperative complete heart block is a relatively rare complication after cardiac surgery for congenital heart disease in the current era, it has significant repercussions if there is no recovery of atrioventricular conduction in the early postoperative period. Insertion of a permanent pacemaker in an infant, child or adolescent remains an important medical decision considering all potential adverse physical and physiological side effects commonly associated with device implant among these younger patients. In this review, the current incidence, morbidity and mortality of postoperative complete heart block is presented as well as contributing anatomical and perioperative risk factors along with potential therapies and long-term sequelae of this unwanted complication.

A 14-year-old female was referred for severe pulmonary valve insufficiency after undergoing radiofrequency ablation for a right ventricular outflow tract tachycardia that originated in the proximal pulmonary artery at 10 years of age. Clinical records indicated that ablation was guided solely by electrograms and electroanatomical mapping. Due to myocardial tissue extensions, mapping failed to identify the level of the pulmonary valve annulus, which resulted in delivery of energy on the valve proper and into the pulmonary artery. She developed severe pulmonary valve insufficiency and moderate proximal pulmonary artery stenosis necessitating intravascular stent placement 4 years later with an associated transcatheter valve. Although the nonfluoroscopic approach during ablation has gained wide acceptance for use in children, this report highlights the benefits of adjunctive imaging to identify the precise location of the pulmonary valve when ablation therapy is contemplated in the right ventricle outflow tract.

Background: Pacemaker implantation is recommended in symptomatic patients with congenital complete heart block (CHB) with either an epicardial (epi) or transvenous (TV) approach depending on patient age / size. However, there is a paucity of data on updated left ventricle (LV) functional indices between the two approaches. Objective: Our aim was to compare LV function using speckle strain imaging in patients with LV Epi vs. best site right (R) TV pacing Methods: This was a single center, retrospective study of patients with isolated CHB …

Objectives The purpose of this study was to use direct cardiac resynchronization therapy (CRT)-paced contractility (dP/dt-max) response as a pre-implantation evaluation among patients with congenital heart disease (CHD) and follow clinical parameters and contractility indexes after CRT implantation. Background Patients with CHD often develop early heart failure with few therapeutic options, leading to heart transplantation (HT). Unfortunately, guidelines for CRT do not apply, and function evaluations by cardiac ultrasound are often inaccurate among CHD anatomies. Therefore, which CHD patients would benefit from CRT remains an enigma. Methods From 1999 to 2015, 103 CHD patients with New York Heart Association (NYHA) functional class II to IV were listed for HT; 40 patients on optimal medical therapy were referred for paced contractility response cardiac catheterization before CRT consideration. If dP/dt-max improved ≥15% from baseline, these “responders” were given the option of CRT with continued follow-up after implantation. Results Of 40 patients studied, 26 (65%) (age 22 ± 8.2 years; 9 of 26 [35%] single or systemic right ventricle; 17 of 26 [65%] with pacemakers) met criteria for possible hemodynamic benefit and underwent CRT implantation. All 26 patients improved in NYHA functional classification: 5 of 26 patients (19%) were later relisted for HT (4 to 144 months, mean 55 months) after CRT implantation, whereas 21 of 26 (81%) continued with improved NYHA functional class (12 to 112 months, mean 44 months) later. A repeat dP/dt-max study following long-term CRT showed stable function or continued contractility improvement. Conclusions Heart failure is common among CHD patients, and therapies are limited. CRT guidelines do not address clinical and anatomic issues of CHD. Short-term paced contractility response testing identifies those CHD patients who are likely to respond to CRT regardless of anatomy.

BACKGROUND Patients with congenital heart defects (CHD) often present more challenges to pacing therapy due to anatomy than those without CHD. The lumenless, 4.1Fr diameter M3830 pacing lead (Medtronic, Inc., Minneapolis, MN, USA), approved for use in 2005, has, to date, reported to have excellent short-term (

Accelerated junctional rhythm has been reported in children in the setting of acute rheumatic fever; however, we describe a hitherto unreported case of isolated junctional tachycardia in a child with streptococcal pharyngitis, not meeting revised Jones criteria for rheumatic fever. A previously healthy, 9-year-old girl presented to the emergency department with complaints of sore throat, low-grade fever, and intermittent chest pain. She was found to have a positive rapid streptococcal antigen test. The initial electrocardiogram showed junctional tachycardia with atrioventricular dissociation in addition to prolonged and aberrant atrioventricular conduction. An echocardiogram revealed normal cardiac anatomy with normal biventricular function. The patient responded to treatment with amoxicillin for streptococcal pharyngitis. The junctional tachycardia and other electrocardiogram abnormalities resolved during follow-up.

A preterm infant with a ventricular septal defect and facial dysmorphisms. ### Prenatal and Birth Histories ### Presentation After birth, the infant was admitted to the NICU because of prematurity. He required supplemental oxygen through a nasal cannula for a brief period (

African American (AA) adults are reported to have lower levels of cardiorespiratory fitness (CRF) as compared to Caucasian adults. CRF is linked to cardiovascular morbidity and mortality. We hypothesized that the disparities start early in childhood. This was a retrospective analysis of the cardiopulmonary exercise test (CPET). We included normal healthy children, ≤ 18 years of age, who had normal electrocardiograms and normal cardiac function. We excluded patients with congenital heart disease, obesity and suboptimal exercise test. The entire cohort was divided into two groups based on race (Caucasian vs. AA) and then further subcategorized by gender. The cohort of 248 patients had a mean ± SD age of 14.4 ± 2.1 years. 158 (60.8%) were males and 158 (60.8%) were Caucasians. Oxygen consumption was higher among Caucasian children when compared to the AA children (48.7 ± 7.9 vs. 45.4 ± 7 mL/kg/min, p = 0.01). This racial disparity continued to persist when comparisons were performed separately for girls and boys. Upon comparing the four groups, the AA females were found to have the lowest values of VO2max, exercise time and METS (p = 0.001). Thus, in conclusion, the AA children have significantly lower level of CRF, as measured by VO2max and exercise time. The racial disparity is independent of gender. African American females show the lowest level of aerobic capacity. The findings of our study suggest that the racial disparity in the CRF levels seen in the adult population may begin early in childhood.

Background Standard, 5–7-Fr diameter pacing leads (PLs) can adversely affect atrioventricular valve (AVV) and venous (superior vena cava [SVC], innominate [INN]) integrities. Although chronic pacing/sensing performances have been reported on the steroid-eluting, lumenless, 4.1-Fr PL (Model 3830, Medtronic Inc., Minneapolis, MN, USA), comparative valve and venous effects are largely unknown. Methods Patients (n = 134) were divided into two PL groups: Group 1 (n = 65, Model 3830) and Group 2 (n = 69, various 5–7 Fr models) and followed up to 9 years postimplant. Patient demographics, clinical findings, valve function, and venous dimensions were reviewed. Statistical significance was defined as P < 0.05. Results Patient implant age (mean 16.4 years vs 17.3 years), presence of congenital heart defect (CHD), and preexisting valve issues were comparable between groups. New or worsening valve insufficiency occurred in 12% of Group 1 patients (mean follow-up 4.3 ± 2.8 years) and 27% of Group 2 patients (mean follow-up 6.2 ± 3.5 years; P < 0.05). Significant SVC or INN narrowing was found in 11 % of Group 1 and 24% of Group 2 patients (P = 0.0004). All Group 1 patients

Vena caval obstruction (VCO) is a common complication after vascular manipulation for congenital heart disease. Long-term efficacy of stent therapy for relief of VCO and long-term stent patency with and without intrastent transvenous pacing leads (TPLs) is not well described. This was a retrospective review of patients treated for VCO, including those who received intrastent TPLs, between 1995 and 2012. Patient demographics, diagnoses, vascular pressure gradients, and vessel diameters were analyzed. Forty-one patients (mean age 23.5 ± 10.3 years) with and without congenital heart disease underwent stent implantation, 26 of whom also received intrastent TPLs. Short-term stent implantation success in relieving obstructions was 93%. Poststent vascular pressure gradients and percentage vascular narrowing significantly improved (from 6.2 ± 4.5 to 1.1 ± 1.6 mm Hg and from 63.1 ± 19.5% to 18.0 ± 17.1%, respectively, p0.05). On follow-up in 38 of 41 patients from 0.2 to 18 years (median 6.0), all survived; 6 (14%) required stent reintervention. Freedom from reintervention was 87% at 15 years. Patients with short-term procedural failure were at higher risk for stent reintervention. Among 27 patients with intrastent TPLs, freedom from reintervention was 96%. In 26 patients with follow-up catheterization, intrastent intimal proliferation was not significantly associated with TPL but was higher in the superior vena cava-innominate vein junction compared with other stent locations (p 0.05). In conclusion, stent therapy for VCO can be successfully and safely performed with good long-term results. Pre-pacing lead stent placement for VCO is effective in allowing TPL placement with encouraging long-term patency.

Designed as effective therapy for patients with symptomatic bradycardia, implantable cardiac pacemakers initially served to improve symptoms and survival. With initial applications to the elderly and those with severe myocardial disease, extended longevity was not a major concern. However, with design technology advances in leads and generators since the 1980s, pacemaker therapy is now readily applicable to all age patients, including children with congenital heart defects. As a result, emphasis and clinical interests have advanced beyond simply quantity to quality of life. Adverse cardiac effects of pacing from right ventricular apical or epicardial sites with resultant left bundle branch QRS configurations have been recognized. As a result, and with the introduction of newer catheter-delivered pacing leads, more recent studies have focused on alternative or select pacing sites such as septal, outflow tract, and para-bundle of His. This is especially important in dealing with pacemaker therapy among younger patients and those with congenital heart disease, with expected decades of artificial cardiac stimulation, in which adverse myocellular changes secondary to pacing itself have been reported. As a correlate to these alternate or select pacing sites, applications of left ventricular pacing, either via the coronary sinus, intraseptal or epicardial, alone or in combination with right ventricular pacing, have gained interest for patients with heart failure. Although cardiac resynchronization pacing has, to date, had limited clinical applications among patients with congenital heart disease, the few published reports do indicate potential benefits as a bridge to cardiac transplant.

Society Guidelines PACES/HRS Expert Consensus Statement on the Recognition and Management of Arrhythmias in Adult Congenital Heart Disease Developed in Partnership Between the Pediatric and Congenital Electrophysiology Society (PACES) and the Heart Rhythm Society (HRS). Endorsed by the Governing Bodies of PACES, HRS, the American College of Cardiology (ACC), the American Heart Association (AHA), the European Heart Rhythm Association (EHRA), the Canadian Heart Rhythm Society (CHRS), and the International Society for Adult Congenital Heart Disease (ISACHD) Paul Khairy, MD, PhD, FRCPC (Chair),* George F. Van Hare, MD, FACC, FHRS (Co-Chair),y Seshadri Balaji, MBBS, PhD,y Charles I. Berul, MD, FHRS,y Frank Cecchin, MD, FACC,z Mitchell I. Cohen, MD, FACC, FHRS,y Curt J. Daniels, MD, FACC,** Barbara J. Deal, MD, FACC,y Joseph A. Dearani, MD, FACC,* Natasja de Groot, MD, PhD,{ Anne M. Dubin, MD, FHRS,y Louise Harris, MBChB, FHRS, Jan Janousek, MD, PhD,{ Ronald J. Kanter, MD, FHRS,y Peter P. Karpawich, MD, FACC, FAHA, FHRS,y James C. Perry, MD, FACC, FHRS,* Stephen P. Seslar, MD, PhD,y Maully J. Shah, MBBS, FHRS,y Michael J. Silka, MD, FACC, FAHA,x John K. Triedman, MD, FACC, FHRS,y Edward P. Walsh, MD, FACC, FHRS,y and Carole A. Warnes, MD, FRCP, FACC, FAHA** Pediatric and Congenital Electrophysiology Society (PACES) representative; yHeart Rhythm Society (HRS) representative; zAmerican College of Cardiology (ACC) representative; xAmerican Heart Association (AHA) representative; {European Heart Rhythm Association (EHRA) representative; Canadian Heart Rhythm Society (CHRS) representative; International Society for Adult Congenital Heart Disease (ISACHD) representative

Recognition and Management of Arrhythmias in Adult Congenital Heart Disease: Executive Summary Developed in partnership between the Pediatric and Congenital Electrophysiology Society (PACES) and the Heart Rhythm Society (HRS). Endorsed by the governing bodies of PACES, HRS, the American College of Cardiology (ACC), the American Heart Association (AHA), the European Heart Rhythm Association (EHRA), the Canadian Heart Rhythm Society (CHRS), and the International Society for Adult Congenital Heart Disease (ISACHD)

Objective The objective of this study was to develop quality metrics (QMs) relating to the ambulatory care of children after complete repair of tetralogy of Fallot (TOF). Design A workgroup team (WT) of pediatric cardiologists with expertise in all aspects of ambulatory cardiac management was formed at the request of the American College of Cardiology (ACC) and the Adult Congenital and Pediatric Cardiology Council (ACPC), to review published guidelines and consensus data relating to the ambulatory care of repaired TOF patients under the age of 18 years. A set of quality metrics (QMs) was proposed by the WT. The metrics went through a two-step evaluation process. In the first step, the RAND-UCLA modified Delphi methodology was employed and the metrics were voted on feasibility and validity by an expert panel. In the second step, QMs were put through an "open comments" process where feedback was provided by the ACPC members. The final QMs were approved by the ACPC council. Results The TOF WT formulated 9 QMs of which only 6 were submitted to the expert panel; 3 QMs passed the modified RAND-UCLA and went through the "open comments" process. Based on the feedback through the open comment process, only 1 metric was finally approved by the ACPC council. Conclusions The ACPC Council was able to develop QM for ambulatory care of children with repaired TOF. These patients should have documented genetic testing for 22q11.2 deletion. However, lack of evidence in the literature made it a challenge to formulate other evidence-based QMs.

Background Supraventricular tachycardia (SVT) in children can be successfully terminated using catheter ablation techniques; however, chronic, true success may be less. Sensed tachycardia (ST) is common following ablation and the differentiation from true arrhythmia recurrences can be challenging. Methods Records of all patients ≤18 years who underwent successful ablation for simple forms of SVT and followed-up for at least a year between 2002 and 2012 were reviewed. Patients with congenital heart disease, atrial muscle tachycardia, and associated ventricular tachycardia were excluded. The diagnostic utility of commonly performed tests was assessed. Results Among the 205 eligible subjects, 202 underwent successful ablation (98.5%), of who five were lost to follow-up before 1 year. The early success rate (6 weeks postablation) and mid-term success rate (1 year postablation) were high (97.5% and 87.4%, respectively) whereas the chronic success (5 years postablation) was only 75%. Although true arrhythmia recurrence was significantly higher in the young (mean 11.5 years vs 13.5 years, P = 0.03) and males (P = 0.02), the presence of diffuse, right-sided fibers was the only independent predictor of true recurrence (odds ratio = 2.7, P = 0.03, 95% confidence interval 1.1, 6.8). Significant ST was reported by 111 patients (56%). The 30-day ambulatory event monitor had the highest sensitivity (71%) when compared to exercise test (19%) and electrocardiogram (24%) in identifying true arrhythmia recurrence. Conclusions Acute and early success may not guarantee chronic ablation success. Postablation, symptomatic patients can be most effectively evaluated using ambulatory event monitoring; however, true recurrence may still be missed and requires closer monitoring.

Although transcatheter arrhythmia ablation (TCA) has been performed in children for over two decades, guidelines for routine use of post-ablation transthoracic echocardiography (TTE) are absent. We sought to determine the efficacy of TTE after apparently uneventful TCA procedures in detecting adverse findings and identify predisposing factors. A retrospective review of clinical and procedural data on patients who underwent TCA for supraventricular arrhythmias from 2000 to 2015 was performed. Pre- and post-ablation TTE data were reviewed. All patients were followed at 1 week, 6 and 12 months post-TCA. A repeat TTE was performed at 12 months on patients in whom post-TCA abnormalities were found. Patients were divided into two groups: those with and without adverse TTE findings and comparative analysis between variables was performed. Data on 252 patients, 52% males, mean age 14 ± 3 years were analyzed. New onset or worsening atrioventricular valve regurgitation occurred in 17 (6.7%), a small pericardial effusion in 3 (1.2%) and worsened ventricular function in 2 patients (0.8%). Patients in the complication group had higher mean number of ablations (22.6 ± 15.3 vs. 16.8 ± 9.2, p 0.001) and required longer duration of ablation (sec) (254.6 ± 256.4 vs. 180.9 ± 158.9, p

Background The early ECG repolarization QRS pattern (ERp), with J-point elevation of 0.1 mV in two contiguous inferior and/or lateral leads, can be associated with ventricular arrhythmias among adults. The significance of an ERp in the young is unknown. Objective The purpose of this study was to assess the prevalence of ERp among young patients (pts), describe and correlate the characteristics with clinical presentations and any arrhythmias. Methods This was a 1 y retrospective review of ECGs obtained from patients referred specifically for documented arrhythmias, possible arrhythmia-related symptoms or sports clearance. ECGs were analyzed for ERp (J-point, ascending/horizontal patterns, location) and correlated with presenting complaints. Results Of 301 patient ECGs, an ERp was found in 177 (59%), (pts age 11.7 ± 4.3 y); 54% male; 23% Caucasian. Of these, 6 pts had a family history of sudden cardiac death. Arrhythmias (72% atrial) occurred in 22 pts. Only 3 pts had ventricular arrhythmias (1 successfully ablated). The ascending ST segment and elevated J-point occurred in 77% and 51% of pts with and without arrhythmias respectively. In 73% of all pts, the ERp location was in inferior/lateral leads. Neither gender, ethnicity, large J-point, lead location, nor the combination of a horizontal ST segment with large J-point correlated with any arrhythmias. Conclusions ERp, especially the diffuse ascending pattern, is common among the young, in those of European ethnicity, found equally in both genders, and with no apparent correlation with atrial nor ventricular arrhythmias.

Background: Cryoablation (Cryo) has augmented radiofrequency (RF) as the ablation energy choice for most supraventricular tachycardias (SVT). Although initial acute results and more recent, but limited, 3‐36-month follow-up studies have been reported, more longer follow-up information is required to determine actual efficacy. Methods: Data from patients with structurally normal hearts who underwent reentrant forms of SVT ablation at our institution from January 2005 to December 2009 were reviewed. These included demographics, clinical and electrophysiologic findings, and ablative energies used. Following apparent acute success, all patients were then reevaluated for any potential recurrences of SVT or preexcitation up to 5 years later. Results: A total of 155 patients (83 male) were reviewed (mean age 13.4 ± 3.7 years). Ablations were predominantly right-sided (75%). Atrioventricular reciprocating tachycardia was seen in 74% and atrioventricular node reciprocating tachycardia (AVNRT) in 17% of patients. For concerns of atrioventricular node integrity, Cryo ± RF was user-preferred for anteroseptal accessory fiber locations and AVNRT. Acute success rate was 98% and chronic 83.2% over the next 5 years. Among patients with accessory pathways, recurrence was pathway number and location dependent: significantly higher (P < 0.05) if they were right anterior-anteroseptal, multiple, or with a broad-distribution pattern. There were no significant differences in recurrence rates with use of RF or its combination with Cryo. Conclusion: Radiofrequency ablation and Cryo are both effective therapies for pediatric patients. Although use of Cryo with RF in combination may enhance safety while affording comparable success, risk of recurrence still persists in the current era among patients depending on accessory pathways connection location and characteristics. (PACE 2012; 35:711‐717)

Objective. Intraatrial Mustard baffle repair of dextro-transposition of the great arteries (d-TGA) is vulnerable to complications, typically obstruction and leaks. Because patients often require pacemakers or intracardiac electrophysiology studies (EPS)/ablation for arrhythmias, narrowed or obstructed baffles restrict cardiac access hindering intracardiac procedures. Current guidelines recommend clinical as well as comprehensive transthoracic echocardiographic/Doppler (TTE) studies to identify baffle problems. This study reviews the effectiveness of these guidelines in detection of baffle issues pre-EPS catheterization and need for ancillary vascular interventions. Design. Data from all patients with repaired d-TGA referred for hemodynamic catheterization or EPS between 1995 and 2009 at our institution were reviewed, including symptoms and TTE findings. Obstruction was defined as either a disturbed color Doppler flow or mean velocity >1 m/s above the mitral valve or directly measured pressure gradient >4 mm Hg or more than 50% baffle diameter narrowing by venography. Results. Of 59 patients (34 pacemaker, 9 ablation, 16 routine hemodynamic) ages 8–39 years (mean 22.8), only three (5%) had symptoms of obstruction. However, baffle complications were found in 33 patients (56%), some with more than one problem: superior vena cava (SVC) obstruction in 32, inferior VC in two and leak in four. Baffle stenting was required in 24 patients and leak closure in two. Precatheterization TTE was available in 51 patients and showed 34% sensitivity, 61% specificity, 63% negative predictive value, and only 37% positive predictive value in recognizing baffle complications when compared with the actual catheterization findings. Conclusion. This study reports that baffle complications in patients with d-TGA following Mustard operation are more common than previously reported. However, comprehensive TTE and clinical symptoms are not effective enough to recognize these complications. Suspicion of and better noninvasive imaging prior to catheterization is required.

Chronic right ventricular (RV) pacing is associated with deleterious effects on cardiac function. In an observational multicentre study in children with isolated atrioventricular (AV) block receiving chronic ventricular pacing, the importance of the ventricular pacing site on left ventricular (LV) function was investigated. Demographics, maternal autoantibody status and echocardiographic measurements on LV end-diastolic and end-systolic dimensions and volumes at age 1 year) for isolated AV block. LV fractional shortening (LVFS) and, if possible LV ejection fraction (LVEF) were calculated. Linear regression analyses were adjusted for patient characteristics. From 27 centres, 297 children were included, in whom pacing was applied at the RV epicardium (RVepi, n = 147), RV endocardium (RVendo, n = 113) or LV epicardium (LVepi, n = 37). LVFS was significantly affected by pacing site (p = 0.001), and not by maternal autoantibody status (p = 0.266). LVFS in LVepi (39 ± 5%) was significantly higher than in RVendo (33 ± 7%, p < 0.001) and RVepi (35 ± 8%, p = 0.001; no significant difference between RV-paced groups, p = 0.275). Subnormal LVFS (LVFS < 28%) was seen in 16/113 (14%) RVendo-paced and 21/147 (14%) RVepi-paced children, while LVFS was normal (LVFS ≥ 28%) in all LVepi-paced children (p = 0.049). These results are supported by the findings for LVEF (n = 122): LVEF was

Innovative, nonthoracotomy, catheter-delivered therapies have redefined the approach to and treatment of congenital heart defects. Starting in the 1960s with the creation of an opening in the atrial septum to permit effective blood mixing and improve oxygen saturation in cyanotic infants, interventional cardiac procedures continue to replace many of the time-honored surgeries that were the mainstay of repair or correction for infants and children with heart defects. Now as those children reach adulthood and still require modifications of their defects, catheter-based interventions are becoming more important. This article examines some of the more recent applications of device therapy currently available to patients with congenital heart, including heart failure, septal defects, vascular problems and heart valves. Device use in deference to surgery, risks and benefits as well as complications associated with such catheter-delivered therapies are discussed.

Purpose: United States approval of the Model 3830, 4.1-French (Fr) diameter, lumenless, pacing lead (Medtronic Inc., Minneapolis, MN, USA) in patients under 17 years of age, and those with congenital heart disease (CHD), was in 2005. To date, long-term performance at alternative pacing sites (APS) is limited and chronic efficacy comparisons with more established leads is lacking. The purpose of this study was to evaluate these factors. Methods: Implant and follow-up data on leads were compared: group 1 (non-3830 leads) and group 2 (Model 3830 leads). These included acute and chronic sensing and pacing, impedances, implant sites, and complications. Groups were compared using Fischer's exact test, paired, and nonpaired t-tests, with significance defined at P < 0.05. Results: A total of 119 patients (ages 5–48 years) received 171 leads: group 1 (n = 80) and group 2 (n = 91). At implant, there were no differences in patient age, CHD, sensing, or pacing thresholds between groups. Implant lead impedances differed between groups but all were within normal values for each lead design. Chronic data showed no difference in sensing, pacing thresholds, or impedances. There were five (6%) early lead dislodgements in group 1 and one (1%) in group 2. APS were achieved in group 2 with mean 1.6 ± 1.3 minutes fluoroscopy time. Conclusion: The new 4.1-Fr lumenless lead shows similar performance indices to established leads even at APS, yet is thinner and achieves APS with technical ease, permitting more efficient chronic pacing in children and all patients with CHD. (PACE 2010; 33:1467–1474)

Tachyarrhythmias can occur at any age from the developing fetus through adulthood. However, in deference to adult-onset ischemic cardiac issues, abnormal heart rhythms occurring in the young are often due to developmental alterations of the cardiac conduction tissue, genetically-inherited changes of myocardial cellular ion membrane properties and both pre- and post-surgical repair of associated structural congenital heart anatomical defects. And different from adults, abnormal rhythms occurring in the young can spontaneously disappear with progressive patient growth. Both supra- and ventricular tachyarrhythmias occur in the young although atrial rhythm abnormalities far exceed those of the ventricle. In both, pharmacologic therapies to alter tissue conduction and refractoriness remain the mainstay for initial intervention in the infant and young child, reserving more invasive and potentially harmful ablation therapies for drug-refractory cases. The purpose of the review is to present common and uncommon tachyarrhythmias which can occur in the fetus and throughout infancy. Emphasis will be placed on their electrocardiographic identification, recognition of any associated structural congenital heart defects and recommended pharmacologic management. Drug therapies will be divided according to mechanism of action and discussions of which particular agent is potentially best-suited to treat which specific tachyarrhythmia. A listing of current pharmacologic agents used in the young with appropriate dosages is included.

The SelectSecure™ catheter delivery system and active fixation 4.1 French diameter Model 3830 pacing lead (Medtronic, Inc, Minneapolis, MN, USA) has the advantage of permitting precise implant at nearly any desired location due to catheter maneuverability. However, as the lead lacks an internal stylet lumen, it is intrinsically floppy and any repositioning after the delivery catheter is removed is nearly impossible, necessitating lead extraction and a repeat of the implant process. At present, there are no commercially available tools to precisely reposition this lead. This report presents a simplified approach to reimplant a dislodged Model 3830 lead using currently available materials to create an effective maneuverable and removable encircling snare.

Background:Transvenous pacemaker leads in children are often placed with redundant lead length to allow for anticipated patient growth. This excess lead may rarely prolapse into the pulmonary artery and potentially interfere with valve function. We sought to determine the response to lead repositioning on pulmonary valve insufficiency. Methods:Retrospective reviews of demographics, lead type, implant duration, and radiography and echocardiography. Results:A total of 11 pediatric patients were identified with lead prolapse through the pulmonary valve, of which nine patients underwent procedures to retract and reposition the lead (age at implant 9 ± 4 years, age at revision 13 ± 4 years). The implant duration prior to revision was 4 ± 3 years. Two leads required radiofrequency extraction sheaths for removal, two pulled back using a snare, while five leads were simply retracted and repositioned. Tricuspid regurgitation was none/trivial (three), mild (four), or moderate (two) and only two improved with repositioning or replacement. Pulmonary regurgitation preoperatively was mild (three), mild-moderate (two), or moderate (four) compared with trivial (three), mild (four), and moderate (two) after revision. Patients with longer-term implanted leads had less improvement in pulmonary insufficiency. Two patients had mild pulmonary stenosis from lead-related obstruction. Conclusions:Prolapse of transvenous pacing leads into the pulmonary artery can occur when excess slack is left for growth. Leads can often be repositioned, but may require extraction and replacement, particularly if chronically implanted and adherent to valve apparatus. Lead revision does not always resolve pulmonary insufficiency, potentially leaving permanent valve damage.

As a pumping organ with an intrinsic electrical system, the heart is unique. For most individuals, it remains efficient for decades. However, as a pump, it can fail. Often the failure is due to inherent or acquired problems with the electrical system. Failure of maintenance of normal sinus rhythm often results in adverse or no heart rhythm, a term referred to as “arrhythmias.” These can result in the heart rate being too fast (“tachy-”) or too slow (“brady-”) and alter blood flow resulting in patient morbidities and mortalities. Arrhythmias can occur anywhere in the heart and may not always be caused by any adverse lifestyle events such as coronary disease. Certain inherited congenital heart defects can cause abnormalities within the developing electrical system that can appear even before birth. Alternatively, the simple process of normal aging can adversely affect the heart’s ability to maintain normal rhythms. Once initiated, arrhythmias can be sustained by the normal anatomical variations of cardiac structures. There are three common arrhythmia etiologies: “automaticity” “reentry,” and “triggered.” Automaticity results from alterations of the basic cellular ion exchange mechanism which is depicted as a distinct electrical pattern, the action potential. Once an electrical impulse is initiated, it typically propagates cell to cell in a relatively uninterrupted fashion. However, if an obstruction (valves, veins) or postinfarction scar tissue occurs, the impulse can circle around the obstruction, creating a reentrant pathway. In rare instances, drugs or disease states can alter cell action potentials, triggering abnormal impulse initiation. This chapter will address all of these issues.

Endomyocardial biopsy is the gold standard survey for cardiac graft rejection. Signal-averaged electrocardiography (SAECG) identifies slowly conducting, diseased myocardium. We sought to determine whether SAECG is a sensitive, noninvasive transplant surveillance method in the young.Ninety-four SAECGs recorded prior to biopsy in 20 young transplant (OHT) patients and those from 15 healthy age-matched controls (CTL) were analyzed. In the OHT group, 56 no-rejection (NOREJ) (ISHLT grades 0 or 1 A) and 37 acute rejection (REJ) (ISHLT grades IB, 2, and 3A) SAECGs were compared, SAECGs were filtered at 40-255 Hz. Total QRS duration (QRSd), duration of terminal low amplitude of QRS under 40 microV (LAS), and root mean square amplitude of terminal 40 msec of QRS (RMS40) were compared.SAECGs were significantly different in CTL vs NOREJ but not in NOREJ vs REJ: QRSd, 81.7 +/- 8, 107.2 +/- 18.4, and 112.3 +/- 21.6 msec, respectively; LAS, (18 +/- 5.8, 23.6 +/- 10.7, and 27 +/- 14.8 msec, respectively; and RMS40, (169.3 +/- 100.4, 68 +/- 48.8, and 57.5 +/- 45.6 microV, respectively. Children following OHT exhibited significant differences in the SAECG compared to controls. Differences between the NOREJ and REJ groups were negligible. Therefore, SAECG may not be effective in detecting OHT rejection in the young.

Objectives Our objective was to evaluate the short-term safety and efficacy of cardiac resynchronization therapy (CRT) in children. Background Cardiac resynchronization therapy has been beneficial for adult patients with poor left ventricular function and intraventricular conduction delay. The efficacy of this therapy in the young and in those with congenital heart disease (CHD) has not yet been established. Methods This is a multi-center, retrospective evaluation of CRT in 103 patients from 22 institutions. Results Median age at time of implantation was 12.8 years (3 months to 55.4 years). Median duration of follow-up was four months (22 days to 1 year). The diagnosis was CHD in 73 patients (71%), cardiomyopathy in 16 (16%), and congenital complete atrioventricular block in 14 (13%). The QRS duration before pacing was 166.1 ± 33.3 ms, which decreased after CRT by 37.7 ± 30.7 ms (p Conclusions Cardiac resynchronization therapy appears to offer benefit in pediatric and CHD patients who differ substantially from the adult populations in whom this therapy has been most thoroughly evaluated to date. Further studies looking at the long-term benefit of this therapy in this population are needed.

Eight patients with venous obstruction secondary to Mustard baffle obstruction or previous transvenous pacemaker leads underwent intravascular stent relief of their obstructions followed by the insertion of new leads. Patients were followed from 1.3 to 6.3 years (median 3) by clinical, hemodynamic, angiographic, and intravascular ultrasound methods and pacemaker evaluations. The median stent patency was 84%, with 1 patient developing complete stent occlusion. Pacing energy thresholds and impedances remained unchanged.

A multicenter prospective study was performed to assess the results and risks associated with radiofrequency ablation in children. This report focuses on recurrences following initially successful ablation.Patients recruited for the study were aged 0 to 16 years and had supraventricular tachycardia due to accessory pathways or atrioventricular nodal reentrant tachycardia (AVNRT), excluding patients with more than trivial congenital heart disease. A total of 481 patients were recruited into the prospective cohort and were followed at 2, 6, and 12 months following ablation.There were 517 successfully ablated substrates out of 540 attempted (95.7%). Loss to follow-up for individual substrates was 3.3%, 10.6%, and 21.2% at 2, 6, and 12 months, respectively. Recurrence was observed in 7.0%, 9.2%, and 10.7% of these substrates at 2, 6, and 12 months, respectively (adjusted for loss to follow-up as an independent source of data censoring). Recurrence rate varied by substrate location (24.6% for right septal, 15.8% for right free wall, 9.3% for left free wall, and 4.8% for left septal), as well as for AVNRT versus all others (4.8% vs 12.9%) at 12 months. The recurrence rate was higher for substrates ablated using power control but was not a function of whether isoproterenol was used for postablation testing.Recurrence after initially successful ablation occurs commonly in children. It is least common after AVNRT ablation and most common following ablation of right-sided pathways. These results serve as a benchmark for the time course of recurrence following initially successful ablation of supraventricular tachycardia in children.

Background: Transthoracic echocardiography (TTE) is reliable for detection of thrombi in the left ventricle and right atrium, but not in the left atrial appendage. Therefore, transesophageal echocardiography (TEE) is routinely performed in adults prior to electric cardioversion for atrial flutter/fibrillation (AFF). Whetheryoung survivors of congenital heart disease repair with AFF need routine TEE prior to electric cardioversion is unknown. Hypothesis: Electric cardioversion for AFF is safe in survivors of congenital heart disease repair/palliation if an intracardiac thrombus is not suspected on TTE imaging. Methods: This study reports the outcome of patients in a pediatric tertiary care cardiac unit where electric cardioversion was performed if no intracardiac thrombus was suspected on TTE. We performed a retrospective chart review of all patients treated with electric cardioversion for AFF at Children's Hospital of Michigan during 1997-2002. Results: Of 35 patients who presented with 110 episodes of AFF requiring electric cardioversion during the study duration, 32 (age 3 months-49 years, median age 20.5 years, 104 AFF episodes) had previously undergone palliative surgery or repair of their congenital heart disease. Of these 32 patients, 18 were survivors of a Fontan palliation (for a single-ventricle variant) and the remaining 14 were survivors of other defects and repairs (septal defects, valve replacements, and tetralogy of Fallot). During 81% of the episodes, patients were receiving aspirin, warfarin, or heparin for anticoagulation at presentation. Transthoracic echocardiography was performed in 74 AFF episodes; of these, 10 TTE studies were suspicious for atrial thrombi. Transesophageal echocardiography confirmed the presence of athrombus in 3 of these 10 patients. These patients received warfarin for 2 weeks and then underwent electric cardioversion. No thromboembolic events occurred immediately after or on follow-up in any patient. Conclusions: These findings suggest that TTE may be an effective imaging tool for precardioversion screening in young patients with AFF.

Cardiac stimulation from right ventricular apical or free-wall lead positions alters inter- and intraventricular impulse conduction and distorts biventricular contractility. This may contribute to eventual cellular remodeling and the development of histopathological changes which, over time, adversely affect left ventricular systolic and diastolic functions. This concept has especially important implications when pacemaker therapy is initiation in young patients. Recent studies demonstrating physiological benefits of right ventricular septal, outflow, or bundle of His pacing, in deference to the apical implant site, have gained interest to potentially prevent dysfunction and improve paced myocardial contractility. Pacing initiated in children can be expected to have more far-reaching consequences than pacing initiated in the elderly. Unfortunately, there have been limited clinical pediatric studies that evaluate precise site-specific lead locations. This current report presents a review of pacemaker applications in children, both with and without structural congenital heart defects, including the earliest applications in which patient survival was the prime concern, to more recent studies attempting to optimize physiological and histological parameters associated with pacemaker induced contractility. The past decade has seen direct evidence that right ventricular apical pacing in children contributes to adverse histological remodeling and eventual contractile dysfunction. More recent studies demonstrate that selective site pacing can be effectively applied to all children with and without structural congenital defects and shows promise in the prevention of previously documented adverse remodeling and deterioration of systemic ventricular contractility.

The aim of this study was to determine if single chamber rate responsive ventricular pacing (VVIR) predisposes growing children to develop pacemaker syndrome (PS), and if so, what are determining factors and/or clinically useful predictors. PS is a constellation of symptoms that result from the lack of consistent AV sequential filling due to atrial contraction against closed AV valves. PS has not been commonly reported in the young. Data from all patients with pacemakers with congenital complete atrioventricular block (CAVB) with normal anatomy, and those with congenital heart disease (CHD), and surgically acquired CAVB were reviewed. Inclusion criteria were normal ventricular function by cardiac ultrasound and 100% VVIR pacing. Of 89 patients with VVIR pacemaker implants, 33 met these criteria. Of these, 19 developed PS. For statistical analysis, chi-square and independent samples t-test was used with significance defined at P < or = 0.05. No consistent association was found between cardiac anatomy, type of CAVB, or age at implant with development of PS. However, PS did correlate with duration of pacing (P = 0.02). The exercise stress test showed significant differences between 100% VVIR-paced patients with and without PS, in terms of work rate (P = 0.002) and measured oxygen consumption (P = 0.01). This study shows that PS appears to be a time related event in younger children with normal ventricular function who are 100% ventricular paced. Thus, this supports VVIR pacing as an adequate and cost-effective initial therapy for symptomatic bradycardia due to CAVB.

Patient size and congenital heart defects complicate pacemaker therapy in children favoring an initial epicardial approach. Steroid-eluting (SE) epicardial (EPI) leads maintain stable, low pacing thresholds in the short-term when compared to the nonsteroid (NSE) epicardial (EPI) leads. The purpose of this study was to evaluate chronic, 10-year performance of SE leads in growing children compared with NSE EPI leads implanted during the same time interval. From 1990 to 2000, 35 patients (age 1 month to 18 year, median 3 years), 28 with and 7 without congenital heart disease (CHD) received 51 SE leads: 27 ventricular and 24 atrial. NSE leads were implanted in 27 patients (age 1-28 years, median 8 years), 24 with and 3 without CHD: 27 ventricular and 1 atrial. Pacing lead threshold, impedance, and energy were measured at implant and during a 10-year follow-up. Unpaired t-test showed that impedance remained stable for all leads with lower mean values for the SE(376 +/- 55 vs 443 +/- 109 Omega) (P = NS). The mean energy requirement for SE leads at 10 years(1.2 +/- 0.9 microJ)was significantly lower than for NSE(4.4 +/- 5.5 microJ) (P < 0.05). At 2.5-V output, chronic thresholds for SE leads did not significantly differ from implant values for atrial (0.08 vs 0.09 ms) or ventricular (0.08 vs 0.08 ms) sites. There were no differences in SE lead performances among patients with or without CHD. Fracture or dislodgement occurred in two SE (4%) and four NSE (14%) leads. SE outperform NSE EPI leads and show stable, chronic low thresholds over time in all growing children.

The advantages of atrial synchrony over asynchronous ventricular pacing remain unclear in the young, chronically right ventricular (RV) - paced patient. This is in contrast to the older patient with inherent diastolic dysfunction who has been shown to benefit from atrial synchrony with dual chamber (DDD,R/VDD), over single chamber rate response (VVI,R) ventricular pacing. The goal of this study was to noninvasively assess cardiac function in a group of young, RV-paced patients before and after establishment of atrial synchrony. Echocardiographic data were retrospectively analyzed from 10 patients with congenital or acquired complete AV block, who were VVI,R paced for 10.2 ± 2 years (mean age at study 19.2 ± 8.9 years), and were subsequently converted to DDD,R/VDD pacing (mean age at study 20.7 ± 9.5 years). Paired t-test analysis of left ventricular (LV) systolic and diastolic function during VVI,R versus DDD,R/VDD pacing did not result in any short-term difference in LV short axis fractional area of change or FAC (53%± 7.5% vs 56.8%± 8.7%) or mitral maximal velocity (E) normalized to mitral flow velocity time integral (VTI) (5.2/s ± 1.5 vs 4.4/s ± 1.5). A decrease in mitral flow E/A ratio was observed after short term DDD,R/VDD pacing (2.2 ± 0.5 vs 1.9 ± 0.3). Atrial synchronous dual chamber pacing in young patients with complete AV block does not lead to any appreciable early change in global LV function over single-site RV pacing. Therefore, early establishment of atrial synchrony in the young asymptomatic VVI,R-paced patient with normal intrinsic ventricular function may not be warranted. (PACE 2003; 26:1208–1211)