Clinical Predictors of Recurrent Supraventricular Tachycardia in Infancy.

BACKGROUND: Data regarding recurrence risk among infants with supraventricular tachycardia (SVT) are limited. OBJECTIVES: The purpose of this study was to determine incidence and factors associated with SVT recurrence. METHODS: This was a retrospective single-center study (1984-2020) with prospective phone follow-up of infants with structurally normal hearts diagnosed at age ≤1 year with re-entrant SVT. Primary outcome was first SVT recurrence after hospital discharge. Classification and regression tree analysis was performed to determine a risk algorithm. RESULTS: Among 460 infants (62% male), 87% were diagnosed at ≤60 days of age (median 13 days; IQR: 1-31 days). During a median follow-up of 5.2 years (IQR: 1.8-11.2 years), 33% had recurrence. On multivariable analysis, factors associated with recurrence included: fetal or late (>60 days) diagnosis (HR: 1.90; 95% CI: 1.26-2.86; and HR: 1.73; 95% CI: 1.07-2.77, respectively), Wolff-Parkinson-White (WPW) syndrome (HR: 2.46; 95% CI: 1.75-3.45), and need for multi-antiarrhythmic or second-line therapy (HR: 2.08; 95% CI: 1.45-2.99). Based on the classification and regression tree analysis, WPW incurred the highest risk. Among those without WPW, age at diagnosis was the most important factor predicting risk. Fetal or late diagnosis incurred higher risk, and if multi-antiarrhythmic or second-line therapy was also required, risk nearly doubled. Infants without WPW, who were diagnosed early (0-60 days), and who were discharged on propranolol were at lowest recurrence risk. CONCLUSIONS: Infants with SVT are most likely to be diagnosed at ≤60 days and be male. Risk factors for recurrence (occurred in 33%), present at time of diagnosis, include WPW, fetal or late diagnosis, and multi-antiarrhythmic or second-line therapy. Infants with early diagnosis, without WPW, and discharged on first-line monotherapy are at lowest recurrence risk.

Flecainide Toxicity Secondary to Accidental Overdose: A Pediatric Case Report of Two Brothers.

Flecainide is a class 1C antiarrhythmic with a narrow therapeutic window and thereby a high-risk medication for causing acute toxicity. Dysrhythmias secondary to flecainide ingestion are often refractory to antiarrhythmics and cardioversion, and patients commonly require extracorporeal support. We review the successful resuscitation of two brothers aged 2 and 4 who presented two years apart with unstable wide-complex tachyarrhythmia suspicious for severe flecainide toxicity. Each patient received sodium bicarbonate and 20% intravenous lipid emulsion with a full recovery. While extracorporeal support is often required following flecainide ingestion, we present two cases where it was avoided due to aggressive multimodal management with sodium bicarbonate, electrolyte repletion, and 20% intravenous lipid emulsion. In addition, avoidance of agitation-induced tachycardia may be beneficial.

Salvage of an epicardial lead in a pacemaker-dependent patient with Fontan palliation using an IS-1 extender.

We present a case report of severed epicardial atrial lead salvage using an IS-1 lead extender. A 37-year-old male with single ventricle physiology, Fontan palliation, sinus node dysfunction, recurrent atrial tachycardias, and atrial fibrillation resulting in failing Fontan physiology presented with failure of the atrial pacing lead. The patient was initially paced with an epicardial system that had to be removed due to pocket infection, and the epicardial leads were cut and abandoned. Given his significant sinus node dysfunction he required atrial pacing to allow for rhythm control. The failing Fontan physiology of the patient precluded him from undergoing surgery for epicardial lead placement or a complex intravascular lead placement procedure (although anatomically feasible). We considered the option of salvaging the existing epicardial atrial leads to provide atrial pacing, allowing for rhythm control and improvement of his failing Fontan physiology as a bridge to a more permanent pacing solution. This case report is important because it demonstrates how a lead extender can be used to salvage a severed pacemaker lead. This may be useful for patients in whom implantation of new leads is not promptly feasible due to patient anatomy and/or clinical status.

The incidence of arrhythmias during exercise stress tests among children with Kawasaki disease: A single-center case series.

OBJECTIVE: Based on 2017 guidelines, participation in competitive sports with prior history of Kawasaki Disease (KD) requires those with coronary artery aneurysms (CAA) z score ≥ 5 to undergo evaluation for evidence of inducible ischemia or arrhythmias. The use of exercise stress testing (EST) to evaluate arrhythmias among KD patients has never been reported. This retrospective single-center case series study sought to describe the presence of inducible arrhythmias during EST in KD patients with or without CAA. METHODS: Single-center retrospective review of medical records of patients diagnosed with KD between 1989-2015 at Texas Children's Hospital, Houston, Texas who underwent EST were included. RESULTS: Among 1007 patients diagnosed with KD, 95 (9%) underwent 165 ESTs at a median time of 9.6 years (IQR 5.8-11.3 years) from diagnosis. Of these 95 patients, 37 had normal coronaries, 21 dilated (z score 2 to <2.5), 10 small (5 >z ≥2.5), 12 medium (10>z ≥ 5 absolute dimension <8 mm), 10 large (z ≥10 or absolute dimension ≥8 mm), 5 severe (myocardial infarct or bypass graft). Supraventricular tachycardia was not seen. Ventricular arrhythmias during EST were uncommon and seen only among patients with CAA z ≥5. Ventricular tachycardia occurred in a single patient with a large CAA, known VT and ICD. High-grade ventricular ectopy was seen in one patient who had severe CAA and underwent bypass grafting. CONCLUSIONS: Arrhythmias on EST were noted only among patients with CAA z ≥5. The current guidelines are a reasonable approach to increasing healthy activity among KD patients. Clarification regarding which inducible arrhythmias meet criteria for activity restriction may be helpful to guide sport participation.

Early experience with intravenous sotalol in children with and without congenital heart disease.

BACKGROUND: Arrhythmias are common in the pediatric population. In patients unable to take oral medications or in need of acute therapy, options of intravenous (IV) antiarrhythmic medications are limited. Recently IV sotalol has become readily available, but experience in children is limited. OBJECTIVE: The purpose of this study was to describe our initial experience with the use of IV sotalol in the pediatric population. METHODS: A retrospective study of all pediatric patients receiving IV sotalol was performed. Patient demographic characteristics, presence of congenital heart disease, arrhythmia type, efficacy of IV sotalol use, and adverse effects were evaluated. RESULTS: A total of 47 patients (26 (55%) male and 24 (51%) with congenital heart disease) received IV sotalol at a median age of 2.05 years (interquartile range 0.07-10.03 years) and a median weight of 12.8 kg (interquartile range 3.8-34.2 kg), and 13 (28%) received IV sotalol in the acute postoperative setting. Supraventricular arrhythmias occurred in 40 patients (85%) and ventricular tachycardia in 7 (15%). Among 24 patients receiving IV sotalol for an active arrhythmia, acute termination was achieved in 21 (88%). Twenty-three patients received IV sotalol as maintenance therapy for recurrent arrhythmias owing to inability to take oral antiarrhythmic medications; 19 (83%) were controlled with sotalol monotherapy. No patient required discontinuation of IV sotalol secondary to adverse effects, proarrhythmia, or QT prolongation. CONCLUSION: IV sotalol is an effective antiarrhythmic option for pediatric patients and may be an excellent agent for acute termination of active arrhythmias. It was well tolerated, with no patient requiring discontinuation secondary to adverse effects.

How active are young cardiac device patients? Objective assessment of activity in children with cardiac devices.

BACKGROUND: The daily activity of pediatric patients with implantable cardiac devices provides behavioral evidence of functional outcomes. Modern devices provide continuous accelerometer data that are sensitive to movement, but normative values have not been published for pediatric activity rates. This study provides the first normative accelerometer data on activity rates in a large sample of pediatric cardiac device patients. METHODS: Patients were between 3 and 18 years old (N = 1,905) and implanted with a cardiac device from a single device company, and enrolled in remote monitoring. RESULTS: The median age at implant was 14 years (interquartile range = 12-16); 61.3% were male. Data for 4 weeks were extracted from a company database at 53 weeks postimplant and an average of daily activity was calculated. Daily average activity for all patients was 5.4 hours (standard deviation  =  2.0). In a multivariate analysis, increased level of activity was associated with: being male, having a pacemaker versus implantable cardioverter defibrillator (ICD), epicardial device location, rate response turned off, having experienced a shock, and younger age. CONCLUSIONS: These results provide the first baseline data of physical activity in children with implanted cardiac devices and provide a clinical guide to physical activity assessment in this population. Further, our data suggest physical activity in children with implantable cardiac devices may differ based on demographic variables, device type, device location, indication for implantation, and history of ICD shock.

Utility and Safety of Combined Interventional Catheterization and Electrophysiology Procedures in a Children's Hospital.

BACKGROUND: Interventional cardiac catheterization (cath) and electrophysiology (EP) procedures are not routinely performed together. There are several perceived barriers affecting this practice, though there are also advantages for both the patient and practitioner to a combined approach. METHODS: This was a single-center retrospective study reviewing combined cath and EP procedures with a preprocedural intention to intervene at Texas Children's Hospital from 2001 to 2014. We excluded procedures in which the intended procedure was purely diagnostic in nature. RESULTS: A total of 121 patients requiring 125 procedures were identified, of which 61 patients underwent 62 procedures that met our inclusion criteria. Potential subgroups of interest included adult congenital heart disease patients (26% of cohort), single ventricle anatomy (34%), and heterotaxy (19%) and collectively 58% of procedures involved a patient in one of these groups. The combined nature of the procedure did not preclude a cath or EP intervention in any patient. There were no mortalities. There were three adverse events, affecting 4.8% of procedures. CONCLUSIONS: Combined interventional cardiac cath and EP procedures in pediatric patients and those with congenital heart disease can be performed safely in a high-volume center. These combined procedures save patients the risk and inconvenience of multiple procedures, and further investigation into cost savings is warranted.

Cardiac Arrest in Pediatric Patients Receiving Azithromycin.

OBJECTIVE: To compare outcomes of pediatric patients treated with azithromycin compared with penicillin or cephalosporin. We hypothesized that azithromycin use would not be associated with increased cardiac mortality in the pediatric population. STUDY DESIGN: Retrospective cohort study from the Pediatric Health Information System database between 2008 and 2012. Patients <19 years of age with a principal diagnosis of community-acquired pneumonia who received an antibiotic were included. Primary outcomes were cardiopulmonary resuscitation (CPR) and mortality. Secondary outcomes were ventricular arrhythmias incidences and readmission for ventricular arrhythmia. Statistical analysis was performed with the χ2 test. Multivariable analysis was performed to control for potential confounders among patient, event, and treatment characteristics. RESULTS: A total of 82 982 patients (54.3% males) met study criteria. Median age was 2.6 years (IQR 1.2-5.9 years) and median length of stay was 2 days (IQR 2-4 days). Azithromycin was used in 5039 (6.1%); penicillin or cephalosporin was used in 77 943 (93.9%). Overall prevalence of antibiotic-associated CPR was 0.14%. Patients receiving a macrolide antibiotic had a lower prevalence of CPR compared with patients receiving a penicillin or cephalosporin (0.04% vs 0.14%, P = .04), and there was no difference in mortality. Multivariable analysis did not find an association between macrolide use and CPR. CONCLUSIONS: In contrast to recent adult studies, among children hospitalized for community-acquired pneumonia, azithromycin use was not associated with a greater prevalence of cardiac arrest compared with penicillin or cephalosporin use.

Late outcomes in children with Shone's complex: a single-centre, 20-year experience.

OBJECTIVE: Shone's syndrome is a complex consisting of mitral valve stenosis in addition to left ventricle outflow obstruction. There are a few studies evaluating the long-term outcomes in this population. We sought to determine the long-term outcomes in our paediatric population with Shone's syndrome and the factors associated with left heart growth. METHODS: All patients diagnosed with Shone's syndrome with biventricular circulation treated between 1978 and 2010 were reviewed. Baseline echocardiograms and data from catheterisations were also reviewed. Number of interventions (surgical+transcatheter), incidence of mitral valve replacement, and incidence of heart transplantation were tracked. Survival of the population and left heart structural growth were also reviewed. RESULTS: A total of 121 patients with Shone's syndrome presented at a median age of 28 days (0-17.3 years) and were followed-up for 7.2 years (0.01-35.5 years). These patients underwent 258 interventions during the study period, and the presence of coarctation was associated with repeat left heart interventions. The 10-year, transplant-free survival was 86%. Presence of pulmonary hypertension was associated with mortality. Left heart structural growth was seen for mitral and aortic valve annuli and left ventricular end-diastolic dimension over time. CONCLUSIONS: Shone's syndrome patients undergo a number of left heart interventions. Coarctation of the aorta is associated with an increased likelihood for repeat interventions. Survival appears to be more favourable than expected. Significant left heart growth will occur in the population. Pulmonary hypertension is associated with an increased risk of mortality.

Percutaneous Pulmonary Valve Implantation-Associated Ventricular Tachycardia in Congenital Heart Disease.

BACKGROUND: Percutaneous pulmonary valve implantation (PPVI) is utilized for dysfunctional right ventricular outflow tracts (RVOT) to relieve obstruction, regurgitation, and RV dysfunction. PPVI has not been reported to induce arrhythmias. This study is the first to report the incidence of ventricular tachycardia (VT) after PPVI. METHODS: This was a retrospective study of all patients who had PPVI at a single institution. All patients were admitted after PPVI for overnight telemetry monitoring. Patients with no prior history of VT and newly detected VT within 24 hours post-PPVI were considered to have VT related to PPVI. RESULTS: In total, 79 patients had PPVI (age 17 ± 9 years, 66% tetralogy of Fallot/pulmonary atresia). PPVI-related VT was detected in 6 patients (7.5%). These patients had a lower BMI (17.5 ± 2.0 vs. 23.1 ± 6.6, P = 0.04). There was no difference in age, native conduit or percutaneous valve size, or change in the minimum diameter of the RVOT from pre- to post-PPVI. In the 6 patients, VT was non-sustained and monomorphic at rates between 120 and 170. Five started on ß-blockers. No patient required surgical explantation of the valve. Over a median follow-up of 2 years, 4 have weaned off medications and all are free of recurrence of VT with normal Holters. CONCLUSIONS: PPVI may be associated with transient VT in the acute peri-procedural period. Patients of smaller size may be more susceptible. All patients were managed conservatively and none of the patients had a recurrence, which is suggestive of a transient phenomenon.

Novel long QT syndrome-associated missense mutation, L762F, in CACNA1C-encoded L-type calcium channel imparts a slower inactivation tau and increased sustained and window current.

BACKGROUND: Mutations in the CACNA1C-encoded L-type calcium channel have been associated with Timothy syndrome (TS) with severe QT prolongation, syndactyly, facial dysmorphisms, developmental delay, and sudden death. Recently, patients hosting CACNA1C mutations with only long QT syndrome (LQTS) have been described. We sought to identify novel variants in CACNA1C associated with either TS or LQTS, and to determine the impact of the mutation on channel function. METHODS/RESULTS: Two probands were identified with mutations in CACNA1C, one with a TS-associated mutation, G406R, and a second with genotype-negative LQTS. Illumina HiSeq 2000 whole exome sequencing on the genotype-negative LQTS proband revealed a novel variant, CACNA1C-L762F, that co-segregated within a multi-generational family. The missense mutation localized to the DII/DIII intracellular interlinker segment of the channel in a highly conserved region in close proximity to the 6th transmembrane segment of domain II (DIIS6). Whole cell patch clamp of heterologously expressed CACNA1C-L762F in TSA201 cells demonstrated slower inactivation tau and increased sustained and window current. Comprehensive review and topological mapping of all described CACNA1C mutations revealed TS-specific hotspots localizing to the cytoplasmic aspect of 6th transmembrane segment of respective domains. Probands hosting TS mutations were associated with elevated QTc, higher prevalence of 2:1 AV block, and a younger age at presentation compared to LQTS. CONCLUSIONS: The CACNA1C-L762F mutation is associated with development of LQTS through slower channel inactivation and increased sustained and window current. TS-associated mutations localize to specific areas of CACNA1C and are associated with a younger age at presentation, higher QTc, and 2:1 AV block than isolated LQTS-associated mutations.

Reassessing Risk Factors in Pediatric Patients With Pacemakers Implanted for Atrioventricular Block: The Impact of Nonsustained Ventricular Tachycardia.

INTRODUCTION: In pediatric patients with pacemakers implanted for atrioventricular block (AVB), nonsustained ventricular tachycardia (NSVT) detected during routine surveillance is a finding of unknown significance. We sought to describe the incidence of NSVT and determine if there was an association between NSVT and adverse outcomes in these patients. METHODS AND RESULTS: This is a single-center retrospective study of 136 patients (1971-2013) with pacemakers implanted for advanced and complete AVB. EXCLUSION CRITERIA: structural heart disease, diagnoses of myocarditis, cardiomyopathy or channelopathy preceding AVB diagnosis, and sustained or polymorphic ventricular tachycardia (VT) as the first occurring arrhythmia after pacemaker implant. During median follow-up of 11.6 years (IQR 4.3 years, 17 years), 14 (10%) patients had NSVT. There were 6 (4.4%) deaths. Overall, Kaplan-Meier 20-year survival from time of implant was 93%. By univariate analysis, earlier mortality was associated with NSVT (P = 0.010), sustained left ventricular (LV) dysfunction (P = 0.004), maternal autoantibodies (P = 0.017), and acquired AVB (P = 0.049). By multivariate analysis, earlier mortality was associated with NSVT (HR: 5.39 [95% CI: 1.02-28.41]; P = 0.047) and sustained LV dysfunction (HR: 10.24 [95% CI: 1.83-57.32]; P = 0.008). CONCLUSIONS: In children with pacemakers implanted for AVB, NSVT is not uncommon and may be associated with increased mortality. Persistent LV dysfunction may also be a potential factor associated with death. Closer follow-up should be considered in patients with these findings. Large, multicenter studies should be considered to confirm these findings and identify risk stratification methods for this unique patient population.