Clinical risk prediction score for postoperative accelerated junctional rhythm and junctional ectopic tachycardia in children with congenital heart disease.

BACKGROUND: Accelerated junctional rhythm (AJR) and junctional ectopic tachycardia (JET) are common postoperative arrhythmias associated with morbidity/mortality. Studies suggest that pre- or intraoperative treatment may improve outcomes, but patient selection remains a challenge. OBJECTIVES: The purpose of this study was to describe contemporary outcomes of postoperative AJR/JET and develop a risk prediction score to identify patients at highest risk. METHODS: This was a retrospective cohort study of children aged 0-18 years undergoing cardiac surgery (2011-2018). AJR was defined as usual complex tachycardia with ≥1:1 ventricular-atrial association and junctional rate >25th percentile of sinus rate for age but <170 bpm, whereas JET was defined as a rate >170 bpm. A risk prediction score was developed using random forest analysis and logistic regression. RESULTS: Among 6364 surgeries, AJR occurred in 215 (3.4%) and JET in 59 (0.9%). Age, heterotaxy syndrome, aortic cross-clamp time, ventricular septal defect closure, and atrioventricular canal repair were independent predictors of AJR/JET on multivariate analysis and included in the risk prediction score. The model accurately predicted the risk of AJR/JET with a C-index of 0.72 (95% confidence interval 0.70-0.75). Postoperative AJR and JET were associated with prolonged intensive care unit and hospital length of stay, but not with early mortality. CONCLUSION: We describe a novel risk prediction score to estimate the risk of postoperative AJR/JET permitting early identification of at-risk patients who may benefit from prophylactic treatment.

Ventricular arrhythmias after fibroma resection: Are patients still at risk?

BACKGROUND: Ventricular fibromas frequently present with life-threatening ventricular tachycardia (VT) or ventricular fibrillation (VF) in children. The long-term risk of sustained ventricular arrhythmias after surgical resection is unknown. OBJECTIVES: The aims of this study were to quantify the VT/VF risk after surgical resection and to examine the results of early (during index surgical hospitalization) and late (≥3 months after surgery) postoperative ventricular stimulation (V-stim) studies. METHODS: We performed a retrospective cohort study of all patients with ventricular fibromas who underwent surgical resection at our institution (2000-2020). The primary outcome was defined as recurrent VT/VF ≥3 months after index surgical resection. RESULTS: Forty-six patients with a median age at surgery of 2 years (range 0.3-18.9 years) formed our study cohort. Indications for surgery included cardiac arrest in 11 (24%), sustained VT in 16 (35%), premature ventricular contractions/nonsustained VT in 10 (22%), and hemodynamic abnormalities in 9 (20%). Of the 11 patients who presented with cardiac arrest, 4 underwent pre-resection implantable cardioverter-defibrillator (ICD) implantation, all of which were explanted at the time of surgery. An early postoperative V-stim study was performed in 26 (57%) patients, and all were negative for inducible VT/VF. Of the 13 late postoperative V-stim studies, 3 were positive: 2 underwent ICD implantation and 1 was initiated on amiodarone and underwent loop recorder implantation. At the time of last follow-up (median 1.5 years; range 0.3-16.5 years), 45 (98%) were free of clinical VT/VF and no patient with an ICD has received an appropriate shock. CONCLUSION: Surgical resection of ventricular fibromas significantly reduces the risk of life-threatening arrhythmias in children; however, a small number of patients remain vulnerable.

Catheter Ablation of Atrioventricular Nodal Reentrant Tachycardia in Patients With Congenital Heart Disease.

Atrioventricular (AV) nodal reentrant tachycardia represents the most common regular supraventricular arrhythmia in humans, and catheter ablation of the so called slow AV nodal pathway has been effectively performed for decades. In patients with congenital heart disease, a combination of different factors makes catheter ablation of AV nodal reentrant tachycardia substrate particularly challenging, including abnormal venous access to intracardiac structures, abnormal intracardiac anatomy, potentially deviant and often unpredictable sites of the specific conduction system, loss of traditional anatomic landmarks, and congenital cardiac surgery that may complicate the access to the AV nodal area. Published experiences have confirmed the efficacy and the relative safety of such procedures when performed by experts, but the risk of complications, in particular AV block, remains non-negligible. A thorough knowledge and understanding of anatomic and electrical specificities according to underlying phenotype are essential in addressing these complex cases. Considering the major consequences associated with AV block in patients with complex congenital heart disease, particularly those without low risk access for transvenous ventricular pacing (eg, single ventricle physiology or Eisenmenger syndrome), the individual risk-benefit ratio should be carefully evaluated. The decision to defer ablation may be the wisest approach in selected patients with either infrequent or hemodynamically tolerated arrhythmias, or when the location of the AV conduction pathways remains uncertain. This narrative review aims to synthetize existing literature on catheter ablation of AV nodal reentrant tachycardia in congenital heart disease, to present main features of common associated pathologies, and to discuss approaches to mapping and safely ablating the slow AV nodal pathway in challenging cases.

Risk Factors for Left Ventricular Dysfunction Following Surgical Management of Cardiac Fibroma.

BACKGROUND: Surgical resection of cardiac fibromas in children reduces hemodynamic and arrhythmia burden; however, little is known about postoperative left ventricular (LV) function. We aimed to evaluate factors associated with postoperative LV dysfunction. METHODS: In this retrospective observational cohort study, imaging data were reviewed from 41 patients who had undergone surgical resection of a cardiac fibroma. Tumor volume was indexed to body surface area (tumor volume index). Right ventricular tumors were excluded from analysis of postoperative ventricular function. Postoperative regional wall motion abnormality score was defined as number of wall segments with regional wall motion abnormality, and LV dysfunction was defined as LV ejection fraction <50%. Cardiovascular magnetic resonance-derived strain was low if <5%ile by previously published normative data. RESULTS: Of 41 patients who underwent resection at a median age of 2.1 years (range, 0.5-19), 37 fibromas were in the LV, (29 free wall and 8 septal), and 4 in the right ventricle. Preoperative median tumor volume index was 66 mL/m2 (range, 11-376). Of 37 patients with LV tumors, younger patients had larger tumor volume index and higher grades of preoperative mitral regurgitation (P<0.001). Larger tumor volume index correlated with higher postoperative regional wall motion abnormality score (P<0.001). By paired pre- and post-operative cardiovascular magnetic resonance (n=14), LV end-diastolic volume increased (mean 76 versus 101 mL/m2, P=0.011), with decreased LV ejection fraction (mean 60% versus 55%, P=0.014), a higher prevalence of low global circumferential strain (36% versus 64%, P=0.045), and decreased cardiac index (mean 4.8 versus 3.9 L/[min·m2], P=0.039). More than mild preoperative mitral regurgitation was the only independent predictor of predischarge LV dysfunction (odds ratio, 22 [95% CI, 2.8-179], P=0.008). CONCLUSIONS: Surgical resection of LV fibroma is associated with regional wall motion abnormality, increased LV volume, and reduced systolic function. Children with significant preoperative mitral regurgitation are at highest risk for LV dysfunction and warrant ongoing close surveillance.

Ventricular Arrhythmia and Life-Threatening Events in Patients With Repaired Tetralogy of Fallot.

Risk stratification for malignant arrhythmias and risk of sudden cardiac death in tetralogy of Fallot (TOF) remains challenging. We aimed to ascertain factors associated with life-threatening arrhythmic events. A multicenter retrospective case-control study including 72 TOF patients with documented cardiac arrest and/or sustained ventricular tachycardia, compared with 216 controls matched for era of surgery. The mean age at event in the cases was 27.3 ± 12.5 years. The majority (57%) presented with sustained ventricular tachycardia. Fatal events occurred in 9. Random forest analysis and a decision tree demonstrated surgical era specific risk factors (< vs ≥ 1980). For both eras, arrhythmic symptoms and left ventricular dysfunction were strongly associated with malignant arrhythmias. In addition, right ventricular dysfunction and age at repair ≥ 6.5 years preceded by a shunt were associated with a higher risk group in the early era, whereas a trans-annular patch type repair was associated with a lower risk group in the recent era. For the moderate and high-risk groups, the decision tree showed a sensitivity of 88.4% and specificity of 68.1%. An "importance factor" was calculated for each predictor, creating a risk score and 4 risk categories. In conclusions, this risk stratification scheme, based on clinical history and noninvasive testing, allows categorization of TOF patients at high risk of malignant arrhythmia. A multicenter prospective evaluation of the accuracy of this scoring system is now being planned.

Value of provocative electrophysiology testing in the management of pediatric patients after congenital heart surgery.

OBJECTIVE: To determine the impact of provocative electrophysiology testing in postoperative congenital heart disease (CHD) patients on the management of supraventricular tachycardia (SVT) and clinical outcomes. METHODS: This is a retrospective study including patients <18 years of age with surgery for CHD who had postoperative SVT between 2006 and 2017. Postoperative outcomes were compared between patients with and without postoperative electrophysiology testing using the Wilcoxon rank sum test, Fisher's exact test, Kaplan-Meier method with the log-rank test, and Cox proportional hazard model. RESULTS: From 341 patients who had SVT after surgery for CHD, 65 (19%) had postoperative electrophysiology testing. There was no significant difference in baseline patient characteristics or surgical complexity between patients with and without electrophysiology testing. Patients with inducible SVT on electrophysiology testing were more likely to have recurrence of SVT prior to hospital discharge with an odds ratio 4.0 (95% confidence interval 1.3, 12.0). Patients who underwent postoperative electrophysiology testing had shorter intensive care unit (12 [6, 20] vs 16 [9, 32] days, HR 2.1 [95% CI 1.6, 2.8], P < .001) and hospital (25 [13, 38] vs 31 [18, 54] days, HR 1.8 [95% CI 1.4, 2.4], P < .001) length of stay. CONCLUSION: Postoperative electrophysiology testing was associated with improved postoperative outcomes, likely related to the ability to predict recurrence of arrhythmia and tailored antiarrhythmic management.

Adverse event rate during inpatient sotalol initiation for the management of supraventricular and ventricular tachycardia in the pediatric and young adult population.

BACKGROUND: Sotalol is an important antiarrhythmic drug in the pediatric population. Given the risk of proarrhythmia, sotalol is initiated in inpatient settings, with adult studies as recent as 2015 supporting this practice. OBJECTIVE: The purpose of this study was to determine the frequency of adverse events (AEs) during sotalol initiation for the management of atrial, supraventricular, or ventricular arrhythmias in pediatric patients. METHODS: A retrospective cohort analysis of pediatric patients 21 years or younger initiated on oral sotalol for supraventricular tachycardia or ventricular tachycardia (VT) at Boston Children's Hospital from January 1, 2007, through July 1, 2016, was performed. The primary end point was an AE defined as significant bradycardia, new or increased ventricular arrhythmias, conduction block, or corrected QT interval (QTc) prolongation, resulting in dose reduction or cessation. RESULTS: There were 190 patients who met inclusion criteria, with 110 patients (58%) 6 months or younger. A total of 115 patients (60%) had congenital heart disease. Arrhythmias for which sotalol was initiated included atrioventricular reciprocating tachycardia/atrioventricular nodal reciprocating tachycardia (n = 105 [55%]), atrial flutter (n = 31 [16%]), ectopic atrial tachycardia (n = 26 [14%]), VT (n = 21 [11%]), and atrial fibrillation (n = 7 [4%]). The median pre-sotalol QTc was 438 ms (interquartile range 348-530 ms). Five patients (3%) (aged 0.1-18 years) had AEs including bradycardia <40 beats/min (n = 2) and <100 beats/min (n = 1) and QTc prolongation (n = 2). All 5 patients with AEs had repaired congenital heart disease. CONCLUSION: The incidence of AEs in pediatric patients initiating sotalol for atrial tachycardia, supraventricular tachycardia, or VT is low (3%), with no deaths or malignant rhythms reported in this series.

Interdigitating Myocardial Tongues in Pediatric Cardiac Fibromas: Plausible Substrate for Ventricular Tachycardia and Cardiac Arrest.

OBJECTIVES: This study sought to evaluate for the presence of and characterize the interdigitating and entrapped myocardium within cardiac fibromas (CF) and correlate tissue findings with symptoms and surgical outcomes. BACKGROUND: The mechanism of ventricular tachycardia (VT) in CF is unclear. The authors hypothesized that CF harbor tongues of interdigitating myocardium, which could be a substrate for episodes of arrhythmia analogous to peri-infarct zones. METHODS: A total of 29 patients (14 boys) with CF were identified; all subjects had undergone at least partial tumor resection. A semiquantitative grading system was used to assess the degree of myocardial interdigitation and entrapment, myocyte morphology (hematoxylin and eosin stain and immunohistochemical stain for desmin), tumor collagen density, and cellularity (trichrome stain). The subjects' ages at presentation, types of arrhythmia, and responses to surgery were correlated with histology. RESULTS: CF consistently demonstrated interdigitating and entrapped myocardium, and the extent correlated negatively with age at surgery, as did cellularity, whereas collagen increased with age. Median age at arrhythmia recognition was 8 months. Sustained VT was present in 18 of 29 patients (62%), and 5 of 6 patients with prenatally diagnosed conditions developed VT before 8 months. All 8 patients who experienced cardiac arrest had clinically significant arrhythmia events. Sustained arrhythmia episodes correlated with more diffuse myocyte interdigitation. Ten patients had abnormal karyotype: chromosomes 9 (n = 3) and 3 (n = 1) deletions; isolated translocations: t(4;13), t(5;11) and t(1;9); and undefined aberrations (n = 3). All patients who underwent complete resection were cured of arrhythmias, whereas 2 of 14 patients who had subtotal resections had recurrence, with resolution following re-resection in 1 patient. CONCLUSIONS: Interdigitating myocardium represents a potential histopathologic substrate for VT and cardiac arrest in CF, which may also explain the occasional recurrence of arrhythmia following incomplete resection.

Long-term results of atrial maze surgery in patients with congenital heart disease.

AIMS: Recurrent atrial tachycardia is common after repair of many types of congenital heart disease, and surgical ablation with a maze procedure represents a potential treatment strategy. The objective of this study is to report a single-centre 19 years' experience with maze surgery in congenital heart patients. METHODS AND RESULTS: Patients undergoing maze procedure concomitantly with cardiac surgical procedures were retrospectively analysed. The maze procedure was classified as therapeutic if the patient demonstrated preoperative atrial arrhythmias, or as prophylactic if done because the patient was considered high risk for post-operative arrhythmias. Acute outcomes and longer-term freedom from atrial arrhythmias were analysed. Maze surgery was performed in 166 patients: 137 in the therapeutic group, and 29 in the prophylactic group. The most common congenital heart lesion was single ventricle for the therapeutic group (27%) and Ebstein's anomaly for the prophylactic group (76%). Surgery consisted of a right atrial maze in 63%, left atrial maze in 4%, and bilateral maze in 33%. There were no direct complications or mortality related to the maze procedure itself. For the therapeutic group, freedom from arrhythmias was 82% and 67% at 1 and 5 years post-maze. Younger age at the time of surgery correlated with a lower long-term recurrence risk. CONCLUSION: Maze procedure at the time of an elective anatomic surgery is reasonably effective to prevent and treat atrial arrhythmias in patients with congenital heart disease at short- and mid-term, with low morbidity and mortality.

Catheter Ablation of Ventricular Arrhythmia for Ebstein's Anomaly in Unoperated and Post-Surgical Patients.

OBJECTIVES: The purpose of this study was to determine the ventricular arrhythmia (VA) substrates in patients with unoperated and post-surgical Ebstein's Anomaly (EA). BACKGROUND: EA is associated with variable atrialization of the right ventricle and a propensity for VA and sudden death. There are scant data on catheter ablation for VA in this population. METHODS: This was a retrospective study involving 11 congenital heart disease centers. RESULTS: A total of 24 patients (median age 17 [interquartile range (IQR): 11 to 37] years; age range 1 to 68 years; 42% men) with EA undergoing catheter ablation were identified. Prior tricuspid valve (TV) surgery had been performed in 12 (50%). Presenting symptoms were palpitations in 15, syncope in 4, aborted cardiac arrest in 4, and none in 1. At procedure, 28 VA substrates were encountered and 25 were completely characterized (median 1 per patient; cycle length 305 [IQR: 268 to 400] ms). In 3 cases, premature ventricular contraction (PVC) foci were targeted (1 with a history of PVC-induced ventricular fibrillation). VA mechanisms were focal in 15 and macro-re-entrant in 10, and did not differ significantly between those with and those without prior TV surgery (p = 0.7). Focal VAs predominantly localized to the atrialized right ventricle ARV in unoperated patients and to diseased myocardium or Purkinje tissue after TV surgery. Macro-re-entry was related to isolated scar or split potentials in the ARV in unoperated patients, and larger, more diffuse scar after TV surgery. Complete success was achieved in 22 (92%). There were 2 of 13 complications in patients <18 years of age and none in patients >18 years of age. There was a single recurrence over a median follow-up of 3.4 years. CONCLUSIONS: VA in EA may be either focal or macro-re-entrant. In the absence of surgery, substrates chiefly involve the ARV. After surgery, focal VA involves injured myocardium or Purkinje tissue and re-entrant ventricular tachycardia is related to post-surgical scar. Catheter ablation is a reasonable therapeutic approach for these patients.

Epicardial ablation of tachyarrhythmia in children: Experience at two academic centers.

BACKGROUND: Experience with percutaneous epicardial ablation of tachyarrhythmia in pediatrics is limited. This case series addresses the feasibility, safety, and complications of the procedure in children. METHODS: A total of nine patients underwent 10 epicardial ablation procedures from 2002 to 2013 at two academic centers. Activation mapping was performed in all cases, and electroanatomic map was utilized in nine of the 10 procedures. Patients had undergone one to three failed endocardial catheter ablations in addition to medical management, and all had symptoms, a high-risk accessory pathway (AP), aborted cardiac arrest with Wolff-Parkinson-White syndrome (WPW), or ventricular dysfunction. A standard epicardial approach was used for access in all cases, using a 7- or 8- Fr sheath. Epicardial ablation modality was radiofrequency (RF) in seven, cryoablation (CRYO) in one, and CRYO plus RF in one. RESULTS: Median age was 14 (range 8-19) years. INDICATIONS: drug refractory ectopic atrial tachycardia (one), ventricular tachycardia (VT) (five), high-risk AP (two), and aborted cardiac arrest from WPW - (one). Epicardial ablation was not performed in one case despite access due to an inability to maneuver the catheter around a former pericardial scar. VT foci included the right ventricular outflow tract septum, high posterior left ventricle (LV), LV outflow tract, postero-basal LV, and scar from previous rhabdomyoma surgery. WPW foci were in the area of the posterior septum and coronary sinus in all three cases. Overall procedural success was 70% (7/10), with epicardial ablation success in five and endocardial ablation success after epicardial mapping in two. The VT focus was close to the left anterior descending coronary artery in one of the unsuccessful cases in which both RF and CRYO were used. There was one recurrence after a successful epicardial VT ablation, which was managed with a second successful epicardial procedure. There were no other recurrences at more than 1 year of follow-up. Complications were minimal, with one case of inadvertent pleural access requiring no specific therapy. No pericarditis or effusion was seen in any of the patients who underwent epicardial ablation. CONCLUSION: Epicardial ablation in pediatric patients can be performed with low complications and acceptable success. It can be considered for a spectrum of tachycardia mechanisms after failed endocardial ablation attempts and suspected epicardial foci. Success and recurrence may be related to foci in proximity to the epicardial coronaries, pericardial scar, or a distant location from the closest epicardial location. Repeat procedures may be necessary.

Catheter ablation for atrioventricular nodal reentrant tachycardia in patients with congenital heart disease.

BACKGROUND: Variability in atrioventricular (AV) node location in congenital heart disease (CHD) can make catheter ablation for atrioventricular nodal reentrant tachycardia (AVNRT) challenging. OBJECTIVE: The purpose of this study was to describe institutional technique and outcomes for slow pathway modification in a cohort with CHD. METHODS: The study consisted of a retrospective review of CHD patients who underwent study from 2001 to 2013 with a diagnosis of AVNRT. Outcomes for slow pathway modification were recorded. In cases in which ablation was deferred, the reasons for this choice were examined. RESULTS: Forty-nine patients (median age 19 years) were included. CHD anatomy involved d-transposition of the great arteries (n = 6), "congenitally corrected" transposition of the great arteries (n = 4), Ebstein anomaly (n = 4), tetralogy of Fallot (n = 5), venous anomalies (n = 8), single ventricle (n = 16), and miscellaneous (n = 6). Ablation was attempted in 39 patients, using radiofrequency energy in 24, cryoablation in 8, and both in 7. Acute success rate was 92% (36/39). One patient had first-degree block in response to cryoablation, but no other complications occurred. At median follow-up 32 months, 1 patient had AVNRT recurrence. Most of the 10 patients in whom ablation was deferred had single-ventricle anatomy with uncertain AV node location. CONCLUSION: Ablation for AVNRT in CHD can be accomplished successfully with attention to underlying anatomy and prior surgery. Patients with single ventricle are a difficult subgroup, and a pharmacologic approach may be indicated in some cases if node localization is ambiguous.

The use of an integrated electroanatomic mapping system and intracardiac echocardiography to reduce radiation exposure in children and young adults undergoing ablation of supraventricular tachycardia.

AIMS: Non-fluoroscopic imaging (NFI) devices are increasingly used in ablations. The objective was to determine the utility of intracardiac echocardiography (ICE) in ablating paediatric supraventricular tachycardias (SVTs) and assess whether its integrated use with electroanatomic mapping (EAM) resulted in lower radiation exposure than use of EAM alone. METHODS AND RESULTS: Prospective, controlled, single-centre study of patients (pts) age ≥10 years, weight ≥35 kg, with SVT and normal cardiac anatomy. Patients were randomized to ICE + EAM (ICE) or EAM only (no ICE). Both had access to fluoroscopy as needed. Eighty-four pts were enroled (42 ICE, 42 no ICE). Median age was 15 years (range 10.4-23.7 years); 57% had accessory pathways, 42% atrioventricular nodal reentry tachycardia. There was no difference in radiation dose (9 mGy ICE vs. 23 mGy no ICE, P = 0.37) or fluoroscopy time (1.1 min ICE vs. 1.5 min no ICE, P = 0.38). Transseptal punctures were performed in 25 pts (16 ICE, 9 no ICE), with ICE reducing radiation (8 mGy ICE vs. 62 mGy no ICE, P = 0.002) and fluoroscopy time (1.1 min ICE vs. 4.5 min no ICE, P = 0.01). Zero fluoroscopy was achieved in 13 pts (15% of total, 5 ICE, 8 no ICE), and low-dose cases (<50 mGy) in 57 pts (68% of total, 33 ICE, 24 no ICE). Acute success was 95% for ICE, 88% for no ICE. CONCLUSION: Use of an integrated EAM/ICE system was no better than EAM alone in limiting radiation, but can be helpful for transseptal punctures. Given the low dose savings, use of ICE may be weighed against its financial cost. Low-fluoroscopy cases are performed in most NFI procedures.

Hot topics in tetralogy of Fallot.

Tetralogy of Fallot (TOF) is the most common cyanotic congenital heart defect. We explore "hot topics" to highlight areas of emerging science for clinicians and scientists in moving toward a better understanding of the long-term management of patients with repaired TOF. From a genetic perspective, the etiology of TOF is multifactorial, with a familial recurrence risk of 3%. Cardiac magnetic resonance is the gold standard assessment tool based on its superior imaging of the right ventricular (RV) outflow tract, pulmonary arteries, aorta, and aortopulmonary collaterals, and on its ability to quantify biventricular size and function, pulmonary regurgitation (PR), and myocardial viability. Atrial re-entrant tachycardia will develop in more than 30% of patients, and high-grade ventricular arrhythmias will be seen in about 10% of patients. The overall incidence of sudden cardiac death is estimated at 0.2%/yr. Risk stratification, even with electrophysiologic testing and cardiac magnetic resonance, remains imperfect. Drug therapy has largely been abandoned, and defibrillator placement, despite its high risks for complications and inappropriate discharges, is often recommended for patients at higher risk. Definitive information about optimal surgical strategies for primary repair to preserve RV function, reduce arrhythmia, and optimize functional status is lacking. Post-operative lesions are often amenable to transcatheter intervention. In selected cases, PR may be treated with transcatheter valve insertion. Ongoing surveillance of RV function is a crucial component of clinical assessment. Except for resynchronization with biventricular pacing, no medical therapies have been shown to be effective after RV dysfunction occurs. In patients with significant PR with RV dilation, optimal timing of pulmonary valve replacement remains uncertain, although accepted criteria are emerging.

The role of cardiac resynchronization therapy for arterial switch operations complicated by complete heart block.

BACKGROUND: As mortality in patients with D-loop transposition of the great arteries (D-TGA) has decreased after the arterial switch operation (ASO), the focus has shifted to higher risk groups and outcomes that impact long-term morbidity and mortality, such as left ventricular (LV) dysfunction. We sought to examine the perioperative factors associated with LV dysfunction in patients with D-TGA and ventricular septal defects (VSD) after ASO. METHODS: A retrospective study was made of all patients with D-TGA/VSD who underwent ASO/VSD closure from 2001 to 2011. Patients with prematurity, L-looped ventricles, and straddling atrioventricular valves were excluded. The primary endpoint was moderate or severe LV dysfunction measured by echocardiogram 2 months or more after surgery. RESULTS: A total of 112 patients underwent ASO/VSD closure at a median age of 5 days. Median time of follow-up was 6.5 months, with no mortality noted. Six patients (8%) were noted to have at least moderate LV dysfunction. Risk factors were heart block requiring pacemaker placement (p<0.001) and length of intensive care unit admission (p=0.04). All 6 patients with heart block had an epicardial lead on the right ventricular free wall; 4 had moderate or severe LV dysfunction and underwent upgrade to cardiac resynchronization therapy (CRT); median time from initial pacemaker to CRT was 5 months. With a median follow-up of 5 months after CRT, LV function improved to normal (2 patients) or mild dysfunction (2 patients). CONCLUSIONS: Left ventricular dysfunction after surgical repair for D-TGA/VSD is low, with heart block and pacemaker insertion playing a significant role. The LV function improved after patients were upgraded to a CRT device.

Effect of aspirin and warfarin therapy on thromboembolic events in patients with univentricular hearts and Fontan palliation.

BACKGROUND: Patients with univentricular hearts and Fontan palliation are at risk for thromboembolic complications. While aspirin and warfarin therapies are currently the mainstay of prophylaxis, controversy exists as to the optimal prevention strategy. METHODS: A cohort study was conducted on the New England registry of patients born in 1985 or earlier with Fontan surgery at Boston Children's Hospital, in order to assess and compare the effect of prophylactic aspirin and warfarin on incident thromboembolic events. RESULTS: A total of 210 qualifying patients (49% male) underwent Fontan surgery at a median age of 8.5 years: 48.6% had a right atrium to pulmonary artery anastomosis, 11% a right atrium to right ventricle conduit, 38.6% a lateral tunnel, and 1.9% an extracardiac conduit. No thromboembolic prophylaxis was prescribed to 50.0%, whereas 24.3% received aspirin, and 25.7% warfarin. In multivariate analyses, lack of aspirin or warfarin was associated with a significantly higher thromboembolic event rate when compared to therapy with either [hazard ratio 8.5, 95% confidence interval (3.6-19.9), P < 0.001], with no difference between the two treatment strategies (P = 0.768). Twenty-year freedom from thromboemboli was 86% versus 52% in patients with and without thromboprophylaxis, respectively. Other factors independently associated with thromboemboli were a low post-operative cardiac index [hazard ratio 2.6, 95% confidence interval (1.2, 5.9)] and atrial fibrillation or flutter [hazard ratio 3.1, 95% confidence interval (1.2, 8.0)]. CONCLUSIONS: Prophylaxis with either aspirin or warfarin was associated with a significantly lower rate of incident thromboembolic events following Fontan palliation, with no difference between the two therapies.

Cardiac tumors and associated arrhythmias in pediatric patients, with observations on surgical therapy for ventricular tachycardia.

OBJECTIVES: The aim of this study was to describe a large experience with primary cardiac tumors in pediatric patients, characterize associated arrhythmias, and expand knowledge of natural history and treatment options. BACKGROUND: Primary cardiac tumors in children are rare. The incidence of arrhythmias is not well-defined, and management plans vary widely. METHODS: We employed a retrospective single-center review of patients ≤21 years of age diagnosed with a primary cardiac tumor between 1968 and 2010. Clinically significant arrhythmias were defined as: 1) sudden cardiac arrest; 2) nonsustained and sustained ventricular tachycardia (VT); 3) pre-excitation; and 4) sustained supraventricular tachycardia of any mechanism. RESULTS: A total of 173 patients were identified: 106 rhabdomyoma, 25 fibroma, 14 myxoma, 6 vascular, 4 teratoma, 3 lipoma, and 15 other. Median age at diagnosis was 7 months (prenatal to 21 years). Of these, 42 (24%) had clinically significant arrhythmias. Patients with large fibromas were the highest-risk group, with VT occurring in 64%. Among rhabdomyoma patients, 10% had pre-excitation, and 6% had VT. Over a mean follow-up of 6 years (1 day to 34 years, median 4 years), surgical excision was performed in 62 cases, with rhythm treatment being 1 of the indications in 20. Post-operatively, clinically significant arrhythmias were eliminated in 18 of these 20, including all 13 fibroma patients. CONCLUSIONS: Clinically significant arrhythmias occurred in 24% of pediatric patients with cardiac tumors, VT being the most common type. Surgical excision for VT associated with rhabdomyomas and fibromas in selected patients is an important and effective management strategy in these patients.

Nonfluoroscopic imaging systems reduce radiation exposure in children undergoing ablation of supraventricular tachycardia.

BACKGROUND: The current standard of care for imaging during supraventricular tachycardia (SVT) ablation uses fluoroscopy, which exposes otherwise healthy children to the potential harmful effects of radiation. OBJECTIVE: The purpose of this study was to determine whether the adjunct use of nonfluoroscopic imaging reduces radiation exposure during SVT ablation among children. METHODS: This was a prospective, controlled, single-center study of patients age ≥8 years, weight ≥25 kg, with SVT and normal cardiac anatomy. Patients were randomized to control (fluoroscopy only) or study group (fluoroscopy + AcuNav intracardiac ultrasound + NavX electroanatomic mapping), stratified by operator to one of five electrophysiologists. Fluoroscopy times (minutes) and radiation doses (mGy) were recorded, and outcomes and adverse events were noted. RESULTS: Seventy-four patients were enrolled (37 control, 37 study). Median age was 14.7 years (range 8.6-22.3 years); 61% had accessory pathways and 39% had atrioventricular nodal reentrant tachycardia. Nonfluoroscopic imaging reduced median fluoroscopy time by 59% (18.3 minutes vs 7.5 minutes, P <.001) and radiation exposure by 72% (387 vs 110 mGy, P <.001). In the study group, 26 of 37 had ≤10 minutes of fluoroscopy, including 2 with no fluoroscopy exposure and 2 with <30 seconds. Electrophysiologic procedure time was not affected by use of nonfluoroscopic imaging, but total case times were prolonged by 31 minutes (P <.001). Acute success was 97% in control and 100% in study patients, with no difference in adverse events. CONCLUSION: Use of nonfluoroscopic imaging during SVT ablation in children resulted in substantial and immediate reductions in fluoroscopy time and radiation exposure without change in acute success or adverse event rates but did increase overall procedural time.

Atrial remodeling after the Fontan operation.

The hemodynamics after Fontan surgery are notable for hypertension and dilation of the right atrium (RA). The effect of this stress on atrial cytoarchitecture has not been systematically studied and might be relevant to arrhythmias and their treatment. Morphologic and histopathologic analyses were performed on tissue from the RA and left atrium (LA) from autopsy specimens of Fontan hearts (n = 47). The findings were compared to those from control samples from young patients with normal atrial hemodynamics (n = 15). Most Fontan specimens were from young patients who died after a relatively short duration of Fontan physiology. The tissues were analyzed for wall thickness, fibrosis content, and fibrosis pattern. The mean wall thickness for the RA (3.0 +/- 1.0 mm) and LA (2.3 +/- 0.6 mm) in the Fontan hearts was significantly greater than that in the control hearts (RA, 1.8 +/- 0.4 mm; LA, 1.8 +/- 0.5 mm; p <0.001 and p = 0.024, respectively). The predictors for thickening of the RA included (1) older age at Fontan surgery, (2) older age at death, and (3) longer duration of Fontan circulation. The Fontan hearts and control hearts exhibited nearly identical fibrosis patterns in the RA and LA. Neither wall thickness nor fibrosis varied with the underlying heart defect or style of Fontan connection. In conclusion, atrial remodeling after Fontan surgery for univentricular heart physiology involves increased wall thickness in both the RA and LA. Interstitial fibrosis was also observed in the Fontan atria; however, because a similar pattern was present in the control tissue, this likely represented normal fibroelastic atrial structure, rather than a specific response to Fontan hemodynamics. The degree of wall thickening observed in the Fontan atria was not so excessive as to preclude transmural lesions during catheter or surgical ablation of reentrant arrhythmias.

Permanent atrial pacing lead implant route after Fontan operation.

BACKGROUND: Atrial pacing is indicated for sinus node dysfunction (SND) after Fontan surgery; preferred lead implantation technique is debated. We compare outcomes of transvenous (TV) and epicardial (Epi) atrial lead implants in this population. METHODS: Retrospective review of Fontan patients undergoing atrial lead implant between 1992 and 2007. Demographics, lead performance data, and outcomes were analyzed. RESULTS: 78 patients had 90 leads implanted: 25 via TV route and 65 via Epi route. Median follow-up was 1.6 years (TV) and 3.6 years (Epi). TV leads were implanted in older patients (23.1 vs 9.3 years, P < 0.001) and at longer intervals after Fontan (15.2 vs 4.9 years, P < 0.001). Pacing indication for most TV leads was SND, while Epi leads were also indicated for atrioventricular block. Acute complication rates were similar (8% TV vs 19% Epi, P = 0.23), but median hospital stay was shorter for TV (2 vs 5 days, P = 0.03). Thrombus was observed in five patients (two in TV; three in Epi), but no thromboembolic events were observed. Mean lead survival was similar (TV 9.9 vs Epi 7.8 years, P = NS). Energy threshold was lower at implant for TV leads (0.9 vs 2.2 microJ, P = 0.049), but similar at follow-up (1.2 vs 2.6 microJ, P = 0.35). Atrial sensing was unchanged over time for TV (2.2 to 2.1 mV, P = NS), but decreased for Epi (3.3 to 2.5 mV, P = 0.02). CONCLUSIONS: Compared to epicardial leads, transvenous atrial pacing leads may be placed in Fontan patients with lower procedural morbidity and equivalent expectation of lead performance and longevity.