Thromboembolism prophylaxis practices of pediatric and congenital electrophysiologists during invasive electrophysiology studies: A PACES survey.

BACKGROUND: Thromboembolic events related to invasive electrophysiology studies, while rare, can have devastating consequences. Use of systemic anticoagulation for a pediatric or adult-congenital invasive electrophysiology study is recommended, however there is no established standard of practice in this population. OBJECTIVE: To report on procedural practices for thromboembolism prophylaxis during invasive electrophysiology studies for pediatric patients and adults with congenital heart disease. METHODS: An anonymous web-based survey was sent to the members of the Pediatric and Congenital Electrophysiology Society. The survey focused on pre-procedural, intra-procedural, and post-procedural thromboembolism prophylaxis practices during invasive electrophysiology studies. Significant practice variation was defined as <90% concordance among respondents. RESULTS: Survey was completed by 73 members; 52 (71%) practicing in the United States, 65 (89%) practicing in an academic institution, and 14 (19%) in an institution that performs more than 200 invasive electrophysiology procedures annually. Responses showed significant variation in practice. Prior to an invasive electrophysiology procedure, 25% discontinue aspirin while 47% discontinue anticoagulants. Heparin is given for all procedures by 32%. When heparin is administered, the first dose is given by 32% after sheaths are placed, 42% after crossing into the systemic atrium, and 26% just prior to systemic-side ablation. Most target an activated clotting time between 200-300 seconds. Post systemic-side ablation, 58% do not initiate a heparin infusion. Post-procedural oral agents were initiated on day of procedure by 34% of respondents and on post-procedure day 1 by 53%. If treating with aspirin, 74% use low-dose (3-5 mg/kg or 81 mg daily), and 68% treat for 4-6 weeks. CONCLUSION: There is significant variation in thromboembolism prophylaxis for invasive EP studies among pediatric and congenital electrophysiologists. Further studies are needed to optimize the management of thromboembolism prophylaxis in this population.

Use of supra-therapeutic phenytoin for management of ventricular arrhythmias in children: Case series and literature review.

Phenytoin is a versatile drug with utility in neurological, dermatological, and even cardiac disease processes. Though phenytoin is widely available due to its excellent anti-epileptic properties, it is now rarely used as an antiarrhythmic. Phenytoin has well-studied sodium-channel blocking abilities which can be taken advantage of to treat ventricular arrhythmias. Thus, it should remain in the arsenal of antiarrhythmics for any electrophysiologist. We present two cases of intractable ventricular arrhythmia in children that were controlled with phenytoin at supra-therapeutic serum levels, preventing the need for heart transplantation.

A distinct molecular mechanism by which phenytoin rescues a novel long QT 3 variant.

BACKGROUND: Genetic variants in SCN5A can result in channelopathies such as the long QT syndrome type 3 (LQT3), but the therapeutic response to Na+ channel blockers can vary. We previously reported a case of an infant with malignant LQT3 and a missense Q1475P SCN5A variant, who was effectively treated with phenytoin, but only partially with mexiletine. Here, we functionally characterized this variant and investigated possible mechanisms for the differential drug actions. METHODS: Wild-type or mutant Nav1.5 cDNAs were examined in transfected HEK293 cells with patch clamping and biochemical assays. We used computational modeling to provide insights into altered channel kinetics and to predict effects on the action potential. RESULTS: The Q1475P variant in Nav1.5 reduced the current density and channel surface expression, characteristic of a trafficking defect. The variant also led to positive shifts in the voltage dependence of steady-state activation and inactivation, faster inactivation and recovery from inactivation, and increased the "late" Na+ current. Simulations of Nav1.5 gating with a 9-state Markov model suggested that transitions from inactivated to closed states were accelerated in Q1475P channels, leading to accumulation of channels in non-inactivated closed states. Simulations with a human ventricular myocyte model predicted action potential prolongation with Q1475P, compared with wild type, channels. Patch clamp data showed that mexiletine and phenytoin similarly rescued some of the gating defects. Chronic incubation with mexiletine, but not phenytoin, rescued the Nav1.5-Q1475P trafficking defect, thus increasing mutant channel expression. CONCLUSIONS: The gain-of-function effects of Nav1.5-Q1475P predominate to cause a malignant long QT phenotype. Phenytoin partially corrects the gating defect without restoring surface expression of the mutant channel, whereas mexiletine restores surface expression of the mutant channel, which may explain the lack of efficacy of mexiletine when compared to phenytoin. Our data makes a case for experimental studies before embarking on a one-for-all therapy of arrhythmias.

A homozygous SCN5A mutation associated with atrial standstill and sudden death.

BACKGROUND: Atrial standstill is an arrhythmogenic condition characterized by the absence of spontaneous electrical and mechanical atrial activity or in response to stimulation. There are few reported familial cases which have been associated with SCN5A mutations cosegregating with GJA5 or RYR2; however, isolated SCN5A mutations are rare. OBJECTIVE: The purpose of this study was to determine the clinical and biophysical consequence of a novel SCN5A mutation identified in a family with progressive atrial standstill and sudden death. METHODS: The family of a sporadic case of congenital atrial standstill underwent genetic screening. Human Embryonic Kidney 293 cells were transfected with wild-type (WT) or mutant SCN5A cDNAs. Biophysical properties were studied using whole-cell using patch clamp methods. RESULTS: A novel homozygous SCN5A mutation, p.V1340L, was identified in the proband and her sister. The proband had complete atrial standstill whereas the sister had partial atrial standstill. Heterozygous mutations were identified in the mother, father, and brother. All three had normal sinus rhythm and were asymptomatic. The mutant Nav1.5(V1340L) reduced Nav1.5 current density as well as showed a depolarizing shift in the voltage-dependent steady-state activation (WT: -35.3 ± 1.62 mV; V1340L: -22.4 ± 2.59 mV; P  =  0.001). CONCLUSIONS: A homozygous loss-of-function SCN5A mutation likely results in atrial standstill and sudden death due to suppression of initiation of action potential.

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.

Multicenter retrospective evaluation of magnetic resonance imaging in pediatric and congenital heart disease patients with cardiac implantable electronic devices.

BACKGROUND: Guidelines addressing magnetic resonance imaging (MRI) in patients with cardiac implantable electronic devices (CIEDs) provide algorithms for imaging pediatric and congenital heart disease (CHD) patients. Guideline acceptance varies by institution. Guidelines also do not support routine MRI scans in patients with epicardial or abandoned leads, common in pediatric and CHD patients. OBJECTIVE: The purpose of this study was to determine the incidence of MRI-related complications in pediatric and CHD patients with CIEDs, including epicardial and/or abandoned leads. METHODS: A multicenter retrospective review included patients with CIEDs who underwent any MRI between 2007 and 2022 at congenital cardiac centers. The primary outcome was any patient adverse event or clinically significant CIED change after MRI, defined as pacing lead capture threshold increase >0.5 V with output change, P- or R- wave amplitude decrease >50% with sensitivity change, or impedance change >50%. RESULTS: Across 14 institutions, 314 patients (median age 18.8 [1.3; 31.4] years) underwent 389 MRIs. There were 288 pacemakers (74%) and 87 implantable cardioverter-defibrillators (22%); 52% contained epicardial leads, and 14 (4%) were abandoned leads only. Symptoms or CIED changes occurred in 4.9% of MRI scans (6.1% of patients). On 9 occasions (2%), warmth or pain occurred. Pacing capture threshold or lead impedance changes occurred in 1.4% and 2.0% of CIEDs post-MRI and at follow-up. CONCLUSION: Our data provide evidence that MRIs can be performed in pediatric and CHD patients with CIEDs, including non-MRI-conditional CIEDs and epicardial and/or abandoned leads, with rare minor symptoms or CIED changes but no other complications.

Update on the Amplatzer duct occluder: a 10-year experience in Asia.

Few data exist regarding the efficacy and safety of the Amplatzer ductal occluder (ADO) type 1 device in the Asian region. This retrospective study, conducted between August 2001 and April 2011, attempted device placement for 231 patients (165 females and 66 males) with a median age of 7.4 years (range, 3 months to 64 years) and an average weight of 19.4 kg (range, 4.1-81.0 kg). Among the patients in this study, 66 (28.6%) had pulmonary hypertension, ten (4.3%) had trisomy 21, and eight (3.5%) had other congenital cardiac anomalies. The mean narrowest patent ductus arteriosus (PDA) diameter was 4.2 mm (range, 1.3-10 mm), and the ampulla size was 9.6 mm (range, 4-20 mm). Successful implantation was achieved for 229 patients (99.1%). Complete angiographic occlusion was achieved for 201 patients (87.8%) at the end the procedure. Follow-up data were available for 129 patients (66%). At the follow-up assessment, complete echocardiographic occlusion was seen in 128 patients (99.2%) after 1 month and in 100% of the patients after 6 months. The significant morbidities involved one device embolization and one dislodgment, for which surgical retrieval was performed. No mortalities occurred during the study period, and no late clinical adverse events occurred during the follow-up period. Occlusion of the PDA using ADO is safe, effective, and applicable for a wide range of PDA sizes including large PDAs in small symptomatic infants and in adults. Good outcomes can be attributed to experience of the operators, proper patient selection, and appropriate device size selection.

Approach to Wide Complex Tachycardia in Paediatric Patients.

Wide complex tachycardia (WCT) is an infrequently encountered condition in paediatric patients and may be due to a variety of causes including supraventricular tachycardia with aberrant conduction, ventricular activation via an accessory pathway, ventricular pacing, or ventricular tachycardia. Immediate tachycardia termination is required in haemodynamically unstable patients. After stabilization or in those with haemodynamically tolerated WCT, a careful review of electrocardiographic tracings and diagnostic manoeuvres are essential to help elucidate the cause. Subacute and chronic management for WCT will depend on the underlying cause as well as features of the patient and the tachycardia presentation. This article will review the epidemiology, potential causes, and management of WCT in children. A detailed review of the pathophysiology, differential diagnosis, and diagnostic and treatment options is provided to enable the reader to develop a practical approach to managing this condition in young patients.

La tachycardie à complexes QRS larges est rare en pédiatrie et peut avoir diverses causes, notamment une tachycardie supraventriculaire avec trouble de la conduction, l'activation ventriculaire par une voie accessoire, une stimulation ventriculaire ou une tachycardie ventriculaire. La suppression immédiate de la tachycardie est primordiale lorsque l'état hémodynamique du patient est instable. Une fois l'état du patient stabilisé, ou en cas de tachycardie à complexes QRS larges tolérée sur le plan hémodynamique, l'examen minutieux des tracés électrocardiographiques et des manœuvres diagnostiques est crucial pour en élucider la cause. La prise en charge des cas subaigus et chroniques de tachycardie à complexes QRS larges dépend de sa cause sous-jacente ainsi que des caractéristiques du patient et du tableau clinique de la tachycardie. Cet article porte sur l'épidémiologie, les causes possibles et la prise en charge de la tachycardie à complexes QRS larges chez les enfants. Un examen approfondi de la physiopathologie, du diagnostic différentiel et des options diagnostiques et thérapeutiques est présenté pour permettre au lecteur d'élaborer une approche pratique pour la prise en charge de cette affection chez leurs jeunes patients.

Incidence of life-threatening events in children with Wolff-Parkinson-White syndrome: Analysis of a large claims database.

BACKGROUND: Previous estimates of life-threatening event (LTE) risk in Wolff-Parkinson-White (WPW) syndrome are limited by selection bias inherent to tertiary care referral-based cohorts. OBJECTIVE: This analysis sought to measure LTE incidence in children with WPW syndrome in a large contemporary representative population. METHODS: A retrospective cohort study was conducted using claims data from the IBM MarketScan Research Databases, evaluating subjects with WPW syndrome (age 1-18 years) from any encounter between January 1, 2013, and December 31, 2018. Subjects with congenital heart disease and cardiomyopathy were excluded. The primary outcome was diagnosis of ventricular fibrillation (VF); a composite outcome, LTE, was defined as occurrence of VF and/or cardiac arrest. VF and LTE rates were compared to matched representative controls without WPW syndrome (3:1 ratio). RESULTS: The prevalence of WPW syndrome was 0.03% (8733/26,684,581) over a median follow-up of 1.6 years (interquartile range 0.7-2.9 years). Excluding congenital heart disease/cardiomyopathy, 6946 subjects were analyzed. An LTE occurred in 49 subjects (0.7%), including VF in 20 (0.3%). The incidence of VF was 0.8 events per 1000 person-years, and the incidence of LTE was 1.9 events per 1000 person-years. There were no occurrences of VF in controls; the rate of LTE was 70 times higher in subjects with WPW syndrome (0.7%; 95% confidence interval 0.5%-0.9%) than in controls (0.01%; 95% confidence interval 0%-0.02%). CONCLUSION: The use of a large claims data set allowed for an evaluation of VF and LTE risk in an unselected pediatric population with WPW syndrome. The observed range of 0.8-1.9 events per 1000 person-years is consistent with prior reports from selected populations. A comparison of event rates to matched controls confirms and quantifies the significant elevation in VF and LTE risk in pediatric WPW syndrome.

A novel technique of single patch repair of right partial anomalous pulmonary venous return to the superior vena cava by right atrial edge rotation.

In patients with partial anomalous pulmonary venous return of the right superior pulmonary veins to the superior vena cava, surgical repair generally consists of either intraatrial baffle with or without caval enlargement, or superior caval transection and cavoatrial anastomosis to the right atrial appendage. We discuss here a novel technique of superior caval enlargement without need for patch material or reimplantation.

Double-barrel right ventricular outflow: tetralogy of Fallot annulus preservation technique.

In patients with tetralogy of Fallot (TOF) repair and a borderline pulmonary valve annulus (PVA) size, surgical repair often necessitates a transannular incision and subsequent placement of a patch with or without a monocusp or, alternatively, a right ventricle-to-pulmonary artery conduit. We discuss here a technique in which the pulmonary valve annulus can be safely preserved, with infrequent postoperative issues as well as the potential for less incidence of right ventricular outflow intervention in the long term.