Utility of Routine Follow-Up Defibrillator Threshold Testing in Congenital Heart Disease and Pediatric Populations

Epicardial Devices in Pediatrics and Congenital Heart Disease

Epicardial cardiac implantable electronic device implant remains a common option in pediatric patients and certain patients with congenital heart disease due to patient size, complex anatomy, residual intracardiac shunts, and prior surgery precluding transvenous implant. Advantages include the lack of thromboembolic and vascular risks and ability to implant during concomitant surgery. Significant disadvantages include the occurrence of lead dysfunction that can result in bradycardia events in pacemaker patients, inappropriate shocks in implantable cardiac defibrillator patients, and overall a more invasive procedure.

Defibrillation Safety Margin Testing in Patients With Congenital Heart Disease: Results From the NCDR

OBJECTIVES

This study analyzed the predictors of defibrillation safety margin (DSM) testing at the time of implantable cardioverter-defibrillator (ICD) insertion and factors associated with inadequate DSM in patients with congenital heart disease (CHD).

BACKGROUND

There are few data about the prevalence and safety of DSM testing in those with CHD.

METHODS

A retrospective analysis was performed of all patients with atrial or ventricular septal defect, tetralogy of Fallot, transposition of the great vessels, Ebstein anomaly, or common ventricle undergoing a transvenous ICD procedure in the National Cardiovascular Data Registry (NCDR) ICD Registry from April 2010 to March 2016, and DSM testing was assessed. Inadequate DSM was defined as a lowest successful energy tested <10 J than the maximum output of the ICD generator.

RESULTS

Of all ICD recipients (N = 7,024), DSM testing was performed in 52.0% (n = 3,654). The mean lowest successful energy tested was 20.7 ± 7.3 J. Of those with DSM adequacy data available (n = 3,623), an inadequate DSM occurred in 13.8% (n = 501). After multivariable adjustment, DSM testing was not associated with in-hospital complications or death (odds ratio [OR]: 1.00; 95% confidence interval [CI]: 0.79 to 1.28) but was associated with lower odds of prolonged hospital stay (>3 days) (OR: 0.71; 95% CI: 0.60 to 0.84; p < 0.0001). An inadequate DSM was not associated with in-hospital death or complications (OR: 1.27; 95% CI: 0.79 to 2.04) or prolonged hospital stay (OR: 1.34; 95% CI: 0.995 to 1.81).

CONCLUSIONS

DSM testing is being performed less frequently over time and seems safe in those with CHD. An inadequate DSM was not associated with worse in-hospital outcomes.

Characteristics and Outcomes of Pediatric Patients Who Undergo Placement of Implantable Cardioverter Defibrillators: Insights From the National Cardiovascular Data Registry

Background Implantable cardioverter defibrillators (ICDs) are an important part of therapy for many patients, yet there is little data on population characteristics, complications, or system survival in pediatric patients. Methods A retrospective review of ICD recipients in the National Cardiovascular Data Registry ICD Registry was performed from 2010 to 2016. Patient characteristics and complications between pediatric (≤21 years) and adult populations (>21 years) were compared. Variables associated with complications and early device interventions within the pediatric cohort were evaluated using multivariate modeling. Results There were 562 209 total ICD implants, of which 3461 occurred in the pediatric cohort. Among the pediatric patients, 60% of implants were for primary prevention, and nonischemic cardiomyopathy was the most common underlying disease (60%). Over time, there was an increasing trend of both primary and secondary prevention ICD implantations ( P<0.05). Compared with adults, pediatric patients were more likely to have structural heart disease, hypertrophic cardiomyopathy, and channelopathy, and to receive a single-chamber device (all P<0.001). There was no difference in inhospital complications between the adult and pediatric cohorts (2.4% versus 2.6%, P=0.3). However, among the pediatric patients, lower weight, Ebstein anomaly, worse New York Heart Association class, dual chamber, and cardiac resynchronization therapy-defibrillator were associated with greater risk of complications. Although reintervention for generator replacement or upgrade was more common in adults, the time to reintervention was shorter in the pediatric cohort. Conclusions We observed an increasing trend in ICD device implantation among pediatric patients. The pediatric cohort had similar inhospital complication rates compared with adults but had a shorter time to reintervention.

Routine DFT testing in patients undergoing ICD implantation does not improve mortality: A systematic review and meta-analysis

Defibrillation threshold (DFT) testing has been an integral part of implantable cardioverter-defibrillator (ICD) implantation to confirm appropriate sensing of ventricular fibrillation and to establish an adequate safety margin for defibrillation. However, there is a lack of evidence regarding benefits of routine DFT testing. Therefore, we performed a meta-analysis to assess its mortality benefit. We searched MEDLINE for studies comparing mortality outcomes in ICD recipients who underwent DFT testing to those who did not. For the second analysis, studies comparing outcomes in patients with high- vs low-energy DFT were included. Odds ratio and standard errors were calculated, and inverse variance method in a random-effect model was used to combine effect sizes. Fifteen studies with 10,975 subjects comparing outcomes in patients who underwent routine DFT testing during ICD implantation and those who did not were included. There was no difference in the group that did not undergo DFT testing with regards to all-cause mortality (OR 0.935; CI 0.725-1.207; P = 0.606), cardiac mortality (OR 0.709; CI 0.385-1.307; P = 0.271), noncardiac mortality (OR 0.921; CI 0.701-1.210; P = 0.554), and arrhythmic mortality (OR 1.152; CI 0.831-1.596; P = 0.396). Percentage of successful appropriate first shocks among the two groups showed no difference. Five studies with 2278 subjects were included in the second analysis comparing patients with low DFT vs high DFT. Patients with high DFT had no significant increase in all-cause mortality compared to patients with low DFT (OR 0.527; CI 0.034-8.107; P = 0.646). Patients requiring higher DFT had no increased all-cause mortality compared to patients with lower DFT. Routine DFT testing during ICD implantation does not confer any significant benefit.

Efficacy and safety of non-transvenous cardioverter defibrillators in infants and young children

BACKGROUND

Implantable cardioverter defibrillators (ICD) protect from sudden cardiac death (SCD). In infants and young children, ICD implantation and programming is challenging due to small body size, elevated heart rates, and high physical activity.

PURPOSE

We report our experience applying a non-transvenous ICD (NT-ICD) system to infants and children < 12 years of age and < 45-kg body weight.

METHODS

Between 07/2004 and 07/2016, NT-ICD had been implanted in 36 patients. Nine out of 36 patients (25%) had NT-ICD implantation for primary and 27/36 (75%) for secondary prevention. Underlying diseases included inherited primary electrical arrhythmogenic diseases (n = 26; 72%), cardiomyopathies (n = 8; 22%), and congenital heart defects (n = 2; 6%). The median (interquartile range) age at implantation was 6 (1.9-8.4) years, and the median body weight was 21.7 (11.2-26.8) kg. Three different NT-ICD implantation techniques had been applied over time: (1) abdominal device/subcutaneous shock coil, (2) abdominal device/pleural shock coil, and (3) subcardiac device/pleural shock coil.

RESULTS

During median follow-up of 5.2 (2.7-7.2) years, appropriate ICD discharges were documented in 12 (33.3%) and inappropriate shocks in 4 patients (11.1%). In 12/36 individuals (33.3%), a total of 25 surgical revisions were required due to NT-ICD malfunction. Eighteen out of 25 (72%) surgical revisions were necessary in patients with subcutaneous shock coil/abdominal device position. Surgical revisions (3/25, 12%) were significantly reduced (p < 0.001) after modifying the implantation technique to subcardiac device/pleural shock coil.

CONCLUSIONS

NT-ICD was safe and effective in infants and young children. Appropriate ICD discharges occurred in a considerable number of patients. After modifying the implantation technique, the need for surgical revision could significantly be decreased.

Value of Regular Defibrillation Threshold Testing After Extracardiac Implantable Cardioverter Defibrillator Placement in Small Children During Mid-Term Follow-Up

OBJECTIVES

The purpose of this study was to analyze course of defibrillation threshold (DFT) with growth.

BACKGROUND

Data on regular DFT testing after extracardiac implantable cardioverter-defibrillator (ICD) placement in infants and small children is still limited.

METHODS

An extracardiac ICD was placed in 23 pediatric patients (median age 6.1 years; median body weight 21 kg, median length 120 cm). The defibrillator lead was tunneled pleurally, and the device was placed as "active can" in the right upper abdomen or in a horizontal position between the diaphragm and the pericardium, respectively. DFT was verified intraoperatively, 3 months later, and every 12 months thereafter. The aim was to achieve DFT <15 J allowing ICD programming with a double safety margin above DFT.

RESULTS

In all 23 patients, an intraoperative DFT <15 J could be accomplished. Serial DFT testing showed an increase from a median DFT of 10 J intraoperatively to 15 J after 1 year. During mean follow-up of 2.0 years, a significant correlation between DFT and body length, but not body weight, was observed. In 4 of 23 (17%) patients, surgical revision was required because of a DFT increase >20 J during regular DFT testing. No complications regarding DFT testing were noted.

CONCLUSIONS

After extracardiac ICD placement in infants and small children, DFT increase related to body length was evident during mid-term follow-up. Routine serial DFT testing was a safe procedure and identified a significant DFT increase in 4 of 23 patients. Serial DFT testing during follow-up in these patients is recommended.

Implantable cardioverter-defibrillators in congenital heart disease

Implantable cardioverter-defibrillators (ICD) have an important role in reducing sudden cardiac death in patients with congenital heart disease (CHD); however, the benefit of ICDs needs to be weighed up against both short-term and long-term adverse effects, which are difficult to evaluate in the heterogeneous CHD population. A tailored approach, taking into account risk stratification and patient-specific factors, is needed to select the most appropriate strategy. This review discusses primary and secondary ICD indications, implantation approaches and long-term follow-up. Recent publications have shed light on the concerns of system longevity, lead extractions, inappropriate shocks and impact on the quality of life. All of these factors require consideration prior to commitment to this long-term treatment strategy.

Defibrillation Threshold Testing: Who Doesn't Get It?

Defibrillation testing has been routinely performed as part of the implantable cardioverter-defibrillator (ICD) implantation procedure, and is currently supported by practice guidelines; however, more recently, this practice has been called into question. Such testing is safe, and serious complications are rare. With modern ICD systems, physicians will rarely encounter a patient in whom defibrillation will fail. This article reviews the literature regarding the utility, necessity, complications, and cost of routine operative and follow-up defibrillation testing, and, it is hoped, clarifies the issue of "Who doesn't get it?"

Prospective evaluation of defibrillation threshold and postshock rhythm in young ICD recipients

BACKGROUND

Adaptation of implantable cardioverter defibrillator (ICD) systems to the needs of pediatric and congenital heart patients is problematic due to constraints of vascular and thoracic anatomy. An improved understanding of the defibrillation energy and postshock pacing requirements in such patients may help direct more tailored ICD therapy. We describe the first prospective evaluation of defibrillation threshold (DFT) and postshock rhythm in this population.

METHODS

We prospectively studied patients ≤ 60 kg at time of ICD intervention. DFTs were obtained using a binary search protocol with three VF inductions. Postshock pacing was programmed using a stepwise protocol, lowering the rate prior to each VF induction.

RESULTS

Twenty patients were enrolled: 11 had channelopathy, five congenital heart disease, and four cardiomyopathy. The median age was 16 years, median weight 48 kg. Twelve patients had a transvenous high-voltage coil; eight had pericardial +/- subcutaneous coil(s). Median DFT was 7 J (range 3-31 J); 19/20 patients had DFT ≤ 15 J and all patients <25 kg had DFT ≤ 9 J (n = 6). There was no difference in DFT between patients with transvenous versus pericardial +/- subcutaneous coils (median 7 J vs 6 J, P = 0.59). No patient with normal atrioventricular conduction prior to defibrillation required postshock pacing (n = 16). There were no adverse events.

CONCLUSIONS

These data suggest that many pediatric ICD patients have low DFTs and adequate postshock escape rhythm. This may help determine appropriate parameters for future design of pediatric-specific ICDs.

Direct intracardiac placement of an automatic implantable cardioverter defibrillator coil lead in a small child

A 3.5-year-old child with hypertrophic obstructive cardiomyopathy and recurrent syncope underwent surgical left-ventricular outflow tract myectomy and implantation of a single-chamber automatic cardioverter defibrillator. A single-coil active fixation lead was introduced via a purse-string suture in the right atrial appendage and the lead tip positioned and fixed in the right-ventricular apex under direct visualization via a small right atriotomy incision. Described configuration may be considered in small children undergoing intracardiac surgery at the time of defibrillator implantation.

Congenital long QT syndrome: Diagnosis and management in pediatric patients

The long QT syndrome (LQTS) is characterized by electrocardiographic abnormalities and a high incidence of syncope and sudden cardiac death (SCD). The diagnosis is suggested when ventricular repolarization abnormalities result in prolongation of the corrected QT interval. When LQTS is suspected, genetic screening may identify a specific long QT subtype and provide guidance for appropriate therapy. Treatment depends on the relative risk of SCD, which is increased with longer QT durations, prior cardiac events, and a family history of SCD. beta Blockers are considered the initial treatment of choice, with implantable cardioverter-defibrillator (ICD) therapy warranted in high-risk patients. In patients with frequent ICD shocks or in those at high risk for SCD where ICD placement cannot be performed, cardiac pacing and/or left cardiac sympathetic denervation may be indicated.

Current state of the art for use of pacemakers and defibrillators in patients with congenital cardiac malformations

As patients with congenital cardiac malformations increasingly survive therapeutic interventions, and our understanding of primary electrical diseases increases, the landscape of paediatric and congenital electrophysiology is expanding. Electrophysiologic abnormalities, both tachycardic and bradycardic, are commonly seen in post-operative patients with congenital cardiac disease, as well as being part of the natural history of congenital malformations and cardiomyopathies. Disturbances of rhythm represent an increasing morbidity in this population, and therapies using devices in the form of pacemakers and implantable cardioverter-defibrillators have taken on a correspondingly important role. In this review, we discuss some of the key features and recent advances in pacing for bradycardia, resynchronization pacing, anti-tachycardia pacing, and use of implantable cardioverter-defibrillators.

A Multicenter Experience with Novel Implantable Cardioverter Defibrillator Configurations in the Pediatric and Congenital Heart Disease Population

INTRODUCTION

In pediatric and congenital heart disease patients, transvenous ICD implantation may be limited secondary to patient size, venous, or cardiac anatomy. Epicardial patches require a thoracotomy, and may lead to a restrictive pericardial process. Because of these issues, we have explored novel ICD configurations.

METHODS

Retrospective review at 10 centers implanting ICDs without a transvenous shocking coil or epicardial patches.

RESULTS

Twenty-two patients underwent implant at a mean age of 8.9 years (range: 0.3-43.5), with a mean weight of 25.5 kg (range: 5.2-70). Diagnoses included complex CHD, intracardiac tumors, cardiomyopathy, idiopathic VT, LV noncompaction, and long QT syndrome. Three configurations were used: subcutaneous array, a transvenous design ICD lead placed on the epicardium, or a transvenous design ICD lead placed subcutaneously. Difficulties were found at implant in 8 patients: 4 had difficulty inducing VT/VF, and 4 had high DFTs. Over a mean follow-up of 2.2 years (range: 0.2-10.5), 7 patients had appropriate shocks. Inappropriate shocks occurred in 4 patients. System revisions were required in 7 patients: 2 generator changes (in 1 patient), 3 pace-sense lead replacement, 1 additional subcutaneous coil placement due to increased DFT, 1 upgrade to a transvenous system, and 1 revision to epicardial patch system.

CONCLUSIONS

ICD implantation can be performed without epicardial patches or transvenous high-energy leads in this population, using individualized techniques. This will allow ICD use in patients who have intracardiac shunting or are deemed too small for transvenous ICD leads. The long-term outcome and possible complications are as yet unknown in this population, and they should be monitored closely with follow-up DFTs.