Kathryn K. Collins

Results of a multicenter retrospective implantable cardioverter-defibrillator registry of pediatric and congenital heart disease patients.

OBJECTIVES We sought to determine the implications of implantable cardioverter-defibrillator (ICD) placement in children and patients with congenital heart disease (CHD). BACKGROUND There is increasing frequency of ICD use in pediatric and CHD patients. Until recently, prospective registry enrollment of ICD patients was not available, and children and CHD patients account for only a small percentage of ICD recipients. Therefore, we retrospectively obtained collaborative data from 4 pediatric centers, aiming to identify implant characteristics, shock frequency, and complications in this unique population. METHODS Databases from 4 centers were collated in a blinded fashion. Demographic information, implant electrical parameters, appropriate and inappropriate shock data, and complications were recorded for all implants from 1992 to 2004. RESULTS A total of 443 patients were included, with a median age of 16 years (range 0 to 54 years) and median weight of 61 kg (range 2 to 130 kg), with 69% having structural heart disease. The most common diagnoses were tetralogy of Fallot (19%) and hypertrophic cardiomyopathy (14%). Implant indication was primary prevention in 52%. Shock data were available on 409 patients, of whom 105 (26%) received appropriate shocks (mean 4 shocks/patient, range 1 to 29 shocks/patient). Inappropriate shocks occurred in 87 of 409 patients (21%), with a mean of 6 per patient (range 1 to 60), mainly attributable to lead failure (14%), sinus or atrial tachycardias (9%), and/or oversensing (4%). CONCLUSIONS Children and CHD ICD recipients have significant appropriate and inappropriate shock frequencies. Optimizing programming, medical management, and compliance may diminish inappropriate shocks. Despite concerns regarding generator recalls, lead failure remains the major cause of inappropriate shocks, complications, and system malfunction in children. Prospective assessment of ICD usage in this population may identify additional important factors in pediatric and CHD patients.

Influence of patient factors and ablative technologies on outcomes of radiofrequency ablation of intra-atrial re-entrant tachycardia in patients with congenital heart disease

OBJECTIVES The goal of this study was to identify factors associated with radiofrequency catheter ablation (RFCA) outcomes of intra-atrial re-entrant tachycardia (IART). BACKGROUND Radiofrequency catheter ablation of IART is difficult. The influence of patient and procedural factors and novel technologies on outcomes is unknown. METHODS Acute and chronic RFCA outcomes were studied in patients with congenital heart disease and IART. Clinical status was measured using a multiaxis severity score. Multivariate analyses identified associations of clinical, procedural and technological factors with outcomes. RESULTS A total of 177 procedures were performed in 134 patients; 139 procedures (79%) resulted in RFCA of > or =1 IART circuit and 117 (66%) in RFCA of all targeted circuits. Multivariate analysis associated acute success with irrigated ablation and absence of atrial fibrillation. Twenty-two complications were noted, nine related to vascular access. Electroanatomic mapping failed to decrease procedure or fluoroscopy time. Improvement in clinical status occurred in most patients (severity score preablation: 6.2 +/- 1.6, postablation: 3.0 +/- 2.3, p < 0.0001). At mean follow-up of 25 +/- 11 months, 42% of patients had IART recurrence and 28% required cardioversion. Six deaths occurred (1.8%/patient-year), and two patients underwent transplant. Chronic outcomes were associated with higher right atrial saturations, use of electroanatomic mapping, fewer IART circuits encountered and acute procedural success. CONCLUSIONS Improvement of acute RFCA outcomes was contemporaneous with introduction of novel technologies. Intra-atrial re-entrant tachycardia recurrence was common, and no effect on mortality was discerned, but most patients had effective palliation of symptoms. Chronic outcome predictors included the underlying disease severity, application of novel technologies and successful ablation of all targeted arrhythmia circuits.

Location of acutely successful radiofrequency catheter ablation of intraatrial reentrant tachycardia in patients with congenital heart disease

Intraatrial reentrant tachycardia (IART) is common after surgery for congenital heart disease (CHD). Radiofrequency (RF) catheter ablation of IART targets anatomic areas critical to the maintenance of the arrhythmia circuit, areas that have not been well defined in this patient population. The purpose of this study was to determine the anatomic areas critical to IART circuits, defined by activation mapping and confirmed by an acutely successful RF ablation at the site. A total of 110 RF ablation procedures in 88 patients (median age 23.4 years, range 0.1 to 62.7) with CHD were reviewed. Patients were grouped according to surgical intervention: Mustard/Senning (n = 15), other biventricular repaired CHD (n = 24), Fontan (n = 43), and palliated CHD (n = 6). In first-time ablation procedures, > or = 1 IART circuits were acutely terminated in 80% of Mustard/Senning, 71% of repaired CHD, and 72% of Fontan (p = NS). The palliated CHD group underwent 1 of 6 successful procedures (17%), and this patient was excluded. The locations of acutely successful RF applications in Mustard/Senning patients (n = 14 sites) were at the tricuspid valve isthmus (57%) and at the lateral right atrial wall (43%). In patients with repaired CHD (n = 18 sites), successful RF sites were at the isthmus (67%) and the lateral (22%) and anterior (11%) right atria. In the Fontan group (n = 40 sites), successful RF sites included the lateral right atrial wall (53%), the anterior right atrium (25%), the isthmus area (15%), and the atrial septum (7%). Location of success was statistically different for the Fontan group (p = .002). In conclusion, the tricuspid valve isthmus is a critical area for ablation of IART during the Mustard/ Senning procedure and in patients with repaired CHD. IART circuits in Fontan patients are anatomically distinct, with the lateral right atrial wall being the more common area for successful RF applications. This information may guide RF and/or surgical ablation procedures in patients with CHD and IART.

Electroanatomic Characterization of Conduction Barriers in Sinus/Atrially Paced Rhythm and Association with Intra‐Atrial Reentrant Tachycardia Circuits Following Congenital Heart Disease Surgery

Conduction Barriers in Sinus Rhythm and IART. Introduction: The electrophysiologic mechanism of intra‐atrial reentrant tachycardia (IART) is generally thought to be a macroreentrant circuit revolving around a nonconductive or highly anisotropic barrier. However, the electrical and anatomic substrate that supports these circuits has been incompletely defined. Our objectives were to characterize the atria of patients with IART using electroanatomic mapping in sinus or atrially paced rhythm and to determine whether electrical barriers identified in sinus/atrially paced rhythm are associated with IART circuits.

Pediatric nonpost-operative junctional ectopic tachycardia medical management and interventional therapies.

OBJECTIVES To determine the outcomes of medical management, pacing, and catheter ablation for the treatment of nonpost-operative junctional ectopic tachycardia (JET) in a pediatric population. BACKGROUND Nonpost-operative JET is a rare tachyarrhythmia that is associated with a high rate of morbidity and mortality. Most reports of clinical outcomes were published before the routine use of amiodarone or ablation therapies. METHODS This is an international, multicenter retrospective outcome study of pediatric patients treated for nonpost-operative JET. RESULTS A total of 94 patients with JET and 5 patients with accelerated junctional rhythm (age 0.8 year, range fetus to 16 years) from 22 institutions were identified. JET patients presenting at age < or =6 months were more likely to have incessant JET and to have faster JET rates. Antiarrhythmic medications were utilized in a majority of JET patients (89%), and of those, amiodarone was the most commonly reported effective agent (60%). Radiofrequency ablation was conducted in 17 patients and cryoablation in 27, with comparable success rates (82% radiofrequency vs. 85% cryoablation, p = 1.0). Atrioventricular junction ablation was required in 3% and pacemaker implantation in 14%. There were 4 (4%) deaths, all in patients presenting at age < or =6 months. CONCLUSIONS Patients with nonpost-operative JET have a wide range of clinical presentations, with younger patients demonstrating higher morbidity and mortality. With current medical, ablative, and device therapies, the majority of patients have a good clinical outcome.

The use of implantable cardioverter-defibrillators in pediatric patients awaiting heart transplantation

BACKGROUND This multicenter study evaluated experience with implantable cardioverter defibrillators (ICD) as a bridge to orthotopic heart transplantation (OHT) in children. METHODS The application of ICD therapy continues to expand in pediatric populations, due in part to improved technology and new indications, including the prevention of sudden death while awaiting OHT. METHODS We performed a retrospective review of ICD databases at 9 pediatric transplant centers. RESULTS Twenty-eight patients (16 males) underwent implantation or had a preexisting ICD while awaiting OHT between 1990 and 2002. The median age at implant was 14.3 years (11 months to 21 years) with a median weight of 49 kg (11.7-88 kg). Diagnoses included cardiomyopathy (n=22), and congenital heart disease (n=6). Indications for ICD implantation included ventricular tachycardia/fibrillation (n=23), syncope (n=5), aborted sudden death with no documentation of rhythm disturbance (n=5), ventricular ectopy (n=1), and poor function (n=5). Of the 28 ICDs, 23 were implanted by a transvenous approach and 5 by epicardial route. There were 55 defibrillator discharges in 17 patients, 47 (85%) of which (in 13 patients) were appropriate. The 8 inappropriate discharges (in 6 patients) were triggered by sinus tachycardia, inappropriate sensing, and atrial flutter. The mean time from implantation to first appropriate shock was 6.9 months (1 day to 2.6 years). Twenty-one patients underwent transplantation during the study period, whereas 2 died while awaiting a donor. Morbidity included a lead fracture, 3 episodes of electromechanical dissociation, and 1 episode of electrical storm. CONCLUSIONS ICD implantation represents an effective bridge to transplantation in pediatric patients. The complication rate is low, with inappropriate device discharge due primarily to sinus tachycardia or atrial flutter. There is a high incidence of appropriate ICD therapy for malignant ventricular arrhythmias in this highly selected group of patients.

Catecholaminergic Polymorphic Ventricular Tachycardia in Children Analysis of Therapeutic Strategies and Outcomes From an International Multicenter Registry

Background—Catecholaminergic polymorphic ventricular tachycardia is an uncommon, potentially lethal, ion channelopathy. Standard therapies have high failure rates and little is known about treatment in children. Newer options such as flecainide and left cardiac sympathetic denervation are not well validated. We sought to define treatment outcomes in children with catecholaminergic polymorphic ventricular tachycardia. Methods and Results—This is a Pediatric and Congenital Electrophysiology Society multicenter, retrospective cohort study of catecholaminergic polymorphic ventricular tachycardia patients diagnosed before 19 years of age. The cohort included 226 patients, including 170 probands and 56 relatives. Symptomatic presentation was reported in 176 (78%). Symptom onset occurred at 10.8 (interquartile range, 6.8–13.2) years with a delay to diagnosis of 0.5 (0–2.6) years. Syncope (P<0.001), cardiac arrest (P<0.001), and treatment failure (P=0.008) occurred more often in probands. &bgr;-Blockers were prescribed in 205 of 211 patients (97%) on medication, and 25% experienced at least 1 treatment failure event. Implantable cardioverter defibrillators were placed in 121 (54%) and was associated with electrical storm in 22 (18%). Flecainide was used in 24% and left cardiac sympathetic denervation in 8%. Six deaths (3%) occurred during a cumulative follow-up of 788 patient-years. Conclusions—This study demonstrates a malignant phenotype and lengthy delay to diagnosis in catecholaminergic polymorphic ventricular tachycardia. Probands were typically severely affected. &bgr;-Blockers were almost universally initiated; however, treatment failure, noncompliance and subtherapeutic dosing were often reported. Implantable cardioverter defibrillators were common despite numerous device-related complications. Treatment failure was rare in the quarter of patients on flecainide. Left cardiac sympathetic denervation was not uncommon although the indication was variable.

Cryoablation for Atrioventricular Nodal Reentrant Tachycardia in Young Patients: Predictors of Recurrence

Background: Recurrence rates of atrioventricular nodal reentry tachycardia (AVNRT) after cryoablation continue to remain high despite excellent initial success rates. Our objective was to evaluate the clinical outcomes of cryoablation for AVNRT with the 4‐mm and 6‐mm tip cryoablation catheters in a young population and to elicit predictors of arrhythmia recurrence.

Cryoablation of Accessory Pathways in the Coronary Sinus in Young Patients: A Multicenter Study from the Pediatric and Congenital Electrophysiology Society's Working Group on Cryoablation

Introduction: This is a multicenter retrospective study evaluating the immediate‐ and mid‐term outcomes of cryoablation of accessory pathways in the coronary sinus in children or in patients with congenital heart disease.

Impact of the permanent ventricular pacing site on left ventricular function in children: a retrospective multicentre survey.

Background Chronic right ventricular (RV) pacing is associated with deleterious effects on cardiac function. Objective 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. Methods Demographics, maternal autoantibody status and echocardiographic measurements on LV end-diastolic and end-systolic dimensions and volumes at age <18 years were retrospectively collected from patients undergoing chronic ventricular pacing (>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. Results 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 <50% in 17/69 (25%) RVendo- and in 10/35 (29%) RVepi-paced patients, while LVEF was ≥50% in 17/18 (94%) LVepi-paced patients. Conclusion In children with isolated AV block, permanent ventricular pacing site is an important determinant of LV function, with LVFS being significantly higher with LV pacing than with RV pacing.