Transcatheter Leadless Pacing in Children: A PACES Collaborative Study in the Real-World Setting

BACKGROUND

Transcatheter Leadless Pacemakers (TLP) are a safe and effective option for adults with pacing indications. These devices may be an alternative in pediatric patients and patients with congenital heart disease for whom repeated sternotomies, thoracotomies, or transvenous systems are unfavorable. However, exemption of children from clinical trials has created uncertainty over the indications, efficacy, and safety of TLP in the pediatric population. The objectives of this study are to evaluate clinical indications, procedural characteristics, electrical performance, and outcomes of TLP implantation in children.

METHODS

Retrospective data were collected from patients enrolled in the Pediatric and Congenital Electrophysiology Society TLP registry involving 15 centers. Patients ≤21 years of age who underwent Micra (Medtronic Inc, Minneapolis, MN) TLP implantation and had follow-up of ≥1 week were included in the study.

RESULTS

The device was successfully implanted in 62 of 63 registry patients (98%) at a mean age of 15±4.1 years and included 20 (32%) patients with congenital heart disease. The mean body weight at TLP implantation was 55±19 kg and included 8 patients ≤8 years of age and ≤30 kg in weight. TLP was implanted by femoral (n=55, 87%) and internal jugular (n=8, 12.6%) venous approaches. During a mean follow-up period of 9.5±5.3 months, there were 10 (16%) complications including one cardiac perforation/pericardial effusion, one nonocclusive femoral venous thrombus, and one retrieval and replacement of TLP due to high thresholds. There were no deaths, TLP infections, or device embolizations. Electrical parameters, including capture thresholds, R wave sensing, and pacing impedances, remained stable.

CONCLUSIONS

Initial results from the Pediatric and Congenital Electrophysiology Society TLP registry demonstrated a high level of successful Micra device implants via femoral and internal venous jugular approaches with stable electrical parameters and infrequent major complications. Long-term prospective data are needed to confirm the reproducibility of these initial findings.

Ventricular Arrhythmic Events After Transcatheter Pulmonary Valve Replacement in Adults with Repaired Tetralogy of Fallot

Arrhythmias are a major cause of morbidity and mortality in repaired Tetralogy of Fallot (rTOF). However, predicting those at risk for life-threatening ventricular arrhythmias (VA) remains difficult. Many centers approach risk assessment at the time of surgical pulmonary valve intervention. Increasing numbers of patients have undergone transcatheter pulmonary valve replacement (TPVR), yet there are no studies evaluating VA in rTOF undergoing TPVR and the approach to risk assessment for these patients. A single center retrospective study was performed. The institutional interventional database was queried to identify all adults ≥ 18 years of age with rTOF status who underwent TPVR from 2010 to 2019. A total of 81 patients with rTOF underwent TPVR from 2010 to 2019. Mean age at time of TPVR was 27 ± 13 years; follow up after TPVR was 6.4 ± 3.1 years. VA events occurred in 4 patients (5%). There was no significant difference in current era VA risk factors in rTOF patients between the VA event group and the non-VA event group. VA risk in this cohort of rTOF with TPVR was 5%, comparable to that reported in current era surgical cohort with similar follow up. Multi-center agreement on risk assessment protocol is needed for future studies.

PentaRay® Multielectrode Mapping Catheter for Atrial Tachyarrhythmia in Adults With Congenital Heart Disease

BACKGROUND

Ablation of atrial tachyarrhythmia in adults with congenital heart disease (ACHD) is challenging because of complex anatomy and high scar burden. We proposed that the addition of high-density mapping with the PentaRay® (Biosense Webster, Inc) mapping catheter (EAM+P) to 3-dimensional electroanatomic mapping (EAM) allows for rapid acquisition of high-resolution maps and shorter procedure times.

METHODS

In this single-center, retrospective cohort study of patients with ACHD who underwent atrial arrhythmia ablation, patients were divided those who underwent ablation with EAM and those who underwent ablation with EAM+P.

RESULTS

Fifteen ablations were performed in 13 patients using standard EAM, and 11 ablations were performed in 10 patients using EAM+P. There was no difference in mean age or complexity of congenital heart disease. The procedure duration was 1.5 times longer in the EAM than in the EAM+P group (P = .015). The dose area product was 12 times higher in the EAM than in the EAM+P group (P = .001). A higher number of venous access sites were used for EAM cases than for EAM+P cases (P = .008). Acute success rates of ablation and recurrence rates at 1 year were similar in the 2 groups. There were no procedure-related complications in either group.

CONCLUSION

This is the first study to evaluate the use of the PentaRay® high-density mapping catheter for ablation of atrial tachyarrhythmia in patients with ACHD. The use of the PentaRay® high-density mapping catheter results in shorter procedure time, decreased radiation exposure, and fewer venous access sites.

A unique mapping strategy for localization and ablation of the atrial input of an antegrade only conducting accessory pathway

The standard technique for accessory pathway ablation involves mapping along the mitral and tricuspid annulus to localize the regions of earliest ventricular activation during antegrade pathway conduction, earliest atrial activation during retrograde conduction or detection of an accessory pathway potential. In some cases despite what appears to be appropriate mapping, catheter positioning and adequate power delivery the ablation is not successful. In many of these cases, the pathway is felt to be inaccessible because of a location remote from the mitral or tricuspid annulus that cannot be affected by endocardial power delivery along the annulus. In the case of difficult left sided pathways, some may be reached and ablated via the coronary sinus or its branches. Right sided pathways cannot be approached in this fashion since there is no venous structure analogous to the coronary sinus around the tricuspid annulus. Alternative mapping and ablation techniques for these difficult pathways have included epicardial mapping via direct pericardial access or attempts to localize pathway insertion areas remote from the valve annulus which may be amenable to endocardial ablation. We describe the use of post-pacing interval mapping to localize the atrial input of a right sided antegrade only accessory pathway that was resistant to conventional mapping and ablation strategies.

Detection of arrhythmias in adult congenital heart disease patients with LINQTM implantable loop recorder

BACKGROUND

Rhythm disorders are the leading cause of morbidity and mortality in adults with congenital heart disease (ACHD). Infrequent or asymptomatic arrhythmias may not be detected by routine monitoring. Implantable loop recorders (ILRs), such as the Reveal LINQ^TM , have been useful in long-term monitoring for arrhythmias in adults with cryptogenic stroke.

OBJECTIVE

We propose the Reveal LINQ^TM will detect arrhythmias, not documented by other monitoring modalities, resulting in change in management in ACHD patients.

METHODS

This is a single center retrospective review of Reveal LINQ^TM use in ACHD patients from 2014-2017. Medical records were reviewed to determine cardiac diagnosis, indication for implant, ILR findings, and changes in management.

RESULTS

Twenty-two patients, median age 25 years, underwent ILR implantation. ILR findings resulted in change in management in nine (41%) patients. One-third (3/9) of the patients with clinically relevant events were asymptomatic. Patients with Fontan palliation had the highest number of pertinent positive events (57%). ACHD physiologic class D patients were more likely to have a positive finding (P = .034) compared to other physiologic classes. Majority (75%) of patients with positive events had arrhythmias documented on ILR which were not demonstrated on prior Holter/event monitors. Pertinent negative event occurred in one patient with Fontan palliation (5%) who had syncope corresponding to sinus rhythm.

CONCLUSION

ILRs are a useful adjunct for arrhythmia monitoring in the ACHD population with clinically relevant events in 41% of patients. A special consideration for ILRs could be made for high-risk asymptomatic patients.

Cardiac Management of the Patient With Duchenne Muscular Dystrophy

Duchenne muscular dystrophy (DMD) results in a progressive cardiomyopathy that produces significant morbidity and mortality. To improve the quality of life in patients with DMD, cardiac care is focused on surveillance and management, with the goal of slowing the onset and progression of heart failure complications. The current article is intended to be an expanded review on the cardiac management data used to inform the 2018 DMD Care Considerations recommendations as well as be a discussion on clinical controversies and future management directions. The new cardiac guidance includes changes regarding noninvasive imaging surveillance of cardiac function and pharmacologic therapy. Many emerging therapies lack sufficient evidence-based data to be recommended in the 2018 DMD Care Considerations. These are discussed in the present article as clinical controversies and future directions. Important emerging therapies include new heart failure medications, mechanical circulatory support with ventricular assist devices, heart transplantation, and internal cardiac defibrillators. Future research studies should be focused on the risks and benefits of these advanced therapies in patients with DMD. We conclude this review with a brief discussion on the relationship between the heart and the recently developed medications that are used to directly target the absence of dystrophin in DMD.

Usefulness of Echocardiography in Children with New-Onset Supraventricular Tachycardia

BACKGROUND

Supraventricular tachycardia (SVT) is the most common sustained arrhythmia in children. Infants with SVT and ventricular preexcitation (Wolff-Parkinson-White syndrome) are known to have up to 30% prevalence of congenital heart disease (CHD). Infants without ventricular preexcitation who present with SVT at <1 year of age have a similar prevalence of CHD. However, for children without ventricular preexcitation who present with SVT at older ages, the prevalence of CHD is not known. The aim of this study was to determine the prevalence of CHD in older children and adolescents presenting with SVT without ventricular preexcitation, with the goal of providing guidance regarding the usefulness of echocardiography in this patient population.

METHODS

Children aged 2 to 18 years presenting with confirmed SVT between January 2011 and December 2015 were included in this retrospective review. Patients with any history of ventricular preexcitation or preexisting heart disease were excluded. Medical records were reviewed, and electrocardiographic and echocardiographic findings were classified as normal, incidental, or abnormal.

RESULTS

Two hundred ninety patients met the inclusion criteria. Echocardiographic examinations were completed on 224 patients. Only one patient was found to have CHD, a moderate primum atrial septal defect. This patient was noted to have electrocardiographic abnormalities consistent with primum atrial septal defect.

CONCLUSIONS

For older children and adolescents with no known heart disease presenting with SVT without ventricular preexcitation, echocardiography may not be a necessary part of initial evaluation when the results of physical examination and electrocardiography are normal.

QRS Duration Changes in Patients with Single Ventricle Physiology: Birth to 10 Years

BACKGROUND

QRS prolongation may be a predictor of mortality in certain forms of congenital heart disease. Minimal data exist describing changes in QRS duration in patients with single ventricles (SVs). The goal was to describe changes in QRS duration in patients with SV and to determine if differences existed between single right ventricle (sRV) versus single left ventricle (sLV) patients.

METHODS

Chart review was performed on patients with SV physiology. Patients were divided into sRV and sLV groups. QRS durations were measured monthly for the first 6 months, at 1 year, and then yearly until 10 years. t-tests were used for analysis.

RESULTS

One hundred sixty patients were evaluated (95 sRV, 65 sLV). The greatest change in QRS duration for the entire cohort occurred in the first 6 months of life versus 6 months to 10 years of age (1.81 ms/month vs 0.20 ms/month). sRV QRS durations were significantly longer than sLV QRS durations at 1 year (78.9 ± 12.6 ms vs 73.2 ± 11.9 ms), 2 year (81.7 ± 14.7 ms vs 73.4 ± 12.5 ms), 4 year (84.2 ± 12.1 ms vs 77.9 ± 16.4 ms), 6 year (90.8 ± 12.7 ms vs 83.4 ± 13.4 ms), 7 year (90.8 ± 16.5 ms vs 81.2 ± 16.6 ms), and 8 year (96.7 ± 13.6 ms vs 84.8 ± 13.9 ms) time points.

CONCLUSION

The greatest change in QRS duration in SV patients occurred in the first 6 months of life when these patients' ventricles were volume loaded. Differences in QRS duration between sRV and sLV patients occurred early in life. Further studies are needed to determine if minimizing volume load early in life decreases the rate of change in QRS duration.

Optimization of biventricular pacing via strain dyssynchrony measurements in a paediatric patient

Cardiac resynchronization therapy is increasingly being used in the paediatric population as a tool for managing patients with heart failure. Various non-invasive parameters have been used to optimize the settings on the biventricular pacemaker. We describe implantation of a biventricular pacemaker in a nineteen-month-old child because of intractable heart failure. By analysing a 17-segment model using strain analysis of the left ventricle, we were able to place the left ventricular lead at the latest activated segment. Furthermore, we were able to minimize the dyssynchrony of the left ventricle when evaluating a range of pacemaker settings.

Epicardial implantable cardioverter-defibrillator system placed in a 4.9-kg infant

Implantable cardioverter-defibrillators have aided the prevention of sudden cardiac death in adults. The hope is to provide similar benefits to the pediatric population as the devices become smaller. Herein, we present the case of a 4.9-kg, 5-week-old infant boy who presented with cardiopulmonary arrest. After emergency defibrillation, conventional treatment options included long-term hospitalization for later cardioverter-defibrillator implantation, or installation of an external defibrillator with subsequent home telemetry. On the basis of the infant's body dimensions, we decided that an epicardial implantable cardioverter-defibrillator was feasible and the best option. We performed a median sternotomy and placed a Vitality® implantable cardioverter-defibrillator with a 25-cm defibrillator coil and a 35-cm bipolar ventricular lead. The patient experienced no postoperative morbidity or rhythm disturbances and was discharged from the hospital on postoperative day 5. He was placed on β-blocker therapy and has remained well for 3 years.Although external devices can be placed in a small patient, we believe that they are too susceptible to lead damage and lead migration, and that the defibrillator thresholds are less reliable. We think that dysrhythmias even in very small children can be treated effectively and safely with use of an epicardial implantable cardioverter-defibrillator. To our knowledge, this 4.9-kg infant is the smallest patient to have undergone a successful implantation of this kind.

Erythropoietin (Epo) and EpoR expression and 2 waves of erythropoiesis

Erythropoiesis occurs in 2 distinct waves during embryogenesis: the primitive wave in the extra-embryonic yolk sac (YS) followed by the definitive wave in the fetal liver and spleen. Even though progenitors for both cell types are present in the YS blood islands, only primitive cells are formed in the YS during early embryogenesis. In this study, it is proposed that erythropoietin (Epo) expression and the resultant EpoR activation regulate the timing of the definitive wave. First, it was demonstrated that Epo and EpoR gene expressions are temporally and spatially segregated: though EpoR is expressed early (embryonic days 8.0-9.5) in the yolk sac blood islands, no Epo expression can be detected in this extra-embryonic tissue. Only at a later stage can Epo expression be detected intra-embryonically, and the onset of Epo expression correlates with the initiation of definitive erythropoiesis. It was further demonstrated that the activation of the EpoR signaling pathway by knocking-in a constitutively active form of EpoR (R129C EpoR) can lead to earlier onset of definitive erythropoiesis in the YS. Thus, these results provide the first in vivo mechanism as to how 2 erythroid progenitor populations can coexist concurrently in the YS yet always differentiate successively during embryogenesis.

Cerberus-like is a secreted factor with neutralizing activity expressed in the anterior primitive endoderm of the mouse gastrula

We report the isolation of mouse cerberus-like (cer-l), a gene encoding a novel secreted protein that is specifically expressed in the anterior visceral endoderm during early gastrulation. Expression in the primitive endoderm starts before the appearance of the primitive streak and lasts until the head-fold stage. In later stages, a second region of expression is found in newly formed somites. Mouse cer-l shares some sequence similarity with Xenopus cerberus (Xcer). In Xenopus assays cer-l, like Xcer, mRNA acts as a potent neuralizing factor that induces forebrain markers and endoderm, but is unable to induce ectopic head-like structures as Xcer does. In addition to cer-l, anterior visceral endoderm was found to express the transcription factors Lim1, goosecoid and HNF-3beta that are also present in trunk organizer cells. A model of how head and trunk development might be regulated is discussed. Given its neuralizing activity, the secreted protein Cer-l is a candidate for mediating inductive activities of anterior visceral endoderm.