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.

ATP1A3-Encoded Sodium-Potassium ATPase Subunit Alpha 3 D801N Variant Is Associated With Shortened QT Interval and Predisposition to Ventricular Fibrillation Preceded by Bradycardia.

Background Pathogenic variation in the ATP1A3-encoded sodium-potassium ATPase, ATP1A3, is responsible for alternating hemiplegia of childhood (AHC). Although these patients experience a high rate of sudden unexpected death in epilepsy, the pathophysiologic basis for this risk remains unknown. The objective was to determine the role of ATP1A3 genetic variants on cardiac outcomes as determined by QT and corrected QT (QTc) measurements. Methods and Results We analyzed 12-lead ECG recordings from 62 patients (male subjects=31, female subjects=31) referred for AHC evaluation. Patients were grouped according to AHC presentation (typical versus atypical), ATP1A3 variant status (positive versus negative), and ATP1A3 variant (D801N versus other variants). Manual remeasurements of QT intervals and QTc calculations were performed by 2 pediatric electrophysiologists. QTc measurements were significantly shorter in patients with positive ATP1A3 variant status (P<0.001) than in patients with genotype-negative status, and significantly shorter in patients with the ATP1A3-D801N variant than patients with other variants (P<0.001). The mean QTc for ATP1A3-D801N was 344.9 milliseconds, which varied little with age, and remained <370 milliseconds throughout adulthood. ATP1A3 genotype status was significantly associated with shortened QTc by multivariant regression analysis. Two patients with the ATP1A3-D801N variant experienced ventricular fibrillation, resulting in death in 1 patient. Rare variants in ATP1A3 were identified in a large cohort of genotype-negative patients referred for arrhythmia and sudden unexplained death. Conclusions Patients with AHC who carry the ATP1A3-D801N variant have significantly shorter QTc intervals and an increased likelihood of experiencing bradycardia associated with life-threatening arrhythmias. ATP1A3 variants may represent an independent cause of sudden unexplained death. Patients with AHC should be evaluated to identify risk of sudden death.

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.

Allowing Adolescents to Weigh Benefits and Burdens of High-stakes Therapies.

We present the case of a girl aged 17 years and 10 months who has a strong family history of long QT syndrome and genetic testing confirming the diagnosis of long QT syndrome in the patient also. She was initially medically treated with ß-blocker therapy; however, after suffering 1 episode of syncope during exertion, she underwent placement of an implantable cardioverter defibrillator. Since then, she has never had syncope. However, during the few months before this presentation, she experienced shocks on multiple occasions without any underlying arrhythmias. These shocks are disconcerting for her, and she is having significant anxiety about them. She requests the defibrillator to be inactivated. However, her mother, who also shares the diagnosis of long QT syndrome, disagrees and wants the defibrillator to remain active. The ethics team is consulted in this setting of disagreement between an adolescent, who is 2 months shy of the age of maturity and medical decision-making, and her mother, who is currently responsible for her medical decisions. The question for the consultation is whether it would be ethically permissible for the doctors to comply with the patient's request to turn off the defibrillator or whether the doctors should follow the mother's wishes until the patient is 18 years of age.

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.

Heterotaxy syndrome and associated arrhythmias in pediatric patients.

BACKGROUND: Heterotaxy syndrome (HS) is a rare disorder with complex anatomy involving misarrangements of the cardiac conduction system. Arrhythmias may be related to anatomic variations and contribute to morbidity. OBJECTIVE: The purpose of this study was to investigate the associations between arrhythmias, anatomy, and outcomes in a large HS cohort. METHODS: A single-center retrospective review of patients ≤21 years of age diagnosed with HS was performed. RESULTS: A total of 337 patients were included in the study. During median follow-up of 7 years (interquartile range 2-16 years), 129 patients (38%) had ≥1 clinically significant rhythm disturbance: tachyarrhythmias in 75 (22%), bradyarrhythmias in 29 (9%), and both in 25 (7%). Factors associated with tachyarrhythmia by multivariate analysis were at least moderate atrioventricular valve regurgitation (hazard ratio [HR] 1.66; 95% confidence interval [CI] 1.11-2.50), single ventricle anatomy (HR 2.30; 95% CI 1.09-4.85), and pulmonary venous obstruction (HR 2.33; 95% CI 1.45-3.76). Isomerism subtype was not associated with tachyarrhythmias. In adjusted and unadjusted analyses, bradyarrhythmias (symptomatic sinus/atrial bradycardia and high-grade or complete heart block) were associated with left atrial isomerism (LAI) compared to right atrial isomerism (HR 7.12; 95% CI 3.01-16.9). The overall transplant-free survival of the cohort was 66%. Tachyarrhythmias, but not bradyarrhythmias, were associated with mortality or need for transplant (HR 2.24; 95% CI 1.45-3.46). CONCLUSION: Clinically significant arrhythmias are common in HS. Although bradyarrhythmias are associated with LAI, tachyarrhythmia occurrence may depend more on hemodynamic and anatomic factors than isomerism subtype. Tachyarrhythmias, but not bradyarrhythmias, are associated with death or need for transplant.

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.

Analysis of adults with congenital heart disease presenting to pediatric emergency departments with arrhythmias.

OBJECTIVE: As survivors of congenital heart disease (CHD) continue to age, healthcare utilization by this population has increased. It is unknown how often these patients utilize the emergency department (ED) at children's hospitals and how arrhythmias play a role in their utilization of care. DESIGN: Using a retrospective cohort design, the Pediatric Hospital Information System (PHIS) database was investigated and we studied adults (≥18 years) with CHD (ACHD) who presented to pediatric EDs from 2004 to 2014. SETTING: Tertiary care pediatric hospitals. RESULTS: Of the 6310 encounters to pediatric EDs, 1594 (25%) were for arrhythmias. The median age was 21 years (IQR 19.1-25.1). The most common tachyarrhythmia diagnoses during the study period were atrial flutter (32%), atrial fibrillation (15%), and paroxysmal VT (10%). Bradyarrhythmias represented a minority of total arrhythmias. Presentation with arrhythmias was associated with an increased risk of admission, ICU care, and death (P < .01). Arrhythmias are also highly associated with CHD severity with twice as many complex CHD having arrhythmias compared to simple CHD (P < .01). CONCLUSIONS: Total admissions of adults with CHD from the ED of children's hospitals have increased over time while the transfers to outside facilities remain consistently low. While the population of ACHD continues to grow, utilization of pediatric EDs for this cohort has increased. Adults with higher CHD complexity are more likely to present with clinical arrhythmias but there is a growing number of ACHD patients with simple complexity presenting with arrhythmias in recent years. ACHD patients that present with arrhythmias are at increased risk of morbidity and mortality.

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.

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.

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.

Circadian Variation of Ventricular Arrhythmias in Catecholaminergic Polymorphic Ventricular Tachycardia.

OBJECTIVES: The aim of this paper was to investigate whether ventricular arrhythmias in children with catecholaminergic polymorphic ventricular tachycardia (CPVT) show circadian patterns. BACKGROUND: Circadian arrhythmic patterns have been established in long QT, Brugada, and early repolarization, but have not been investigated in CPVT. METHODS: This is a multicenter, retrospective review of pediatric CPVT patients, age <21 years at diagnosis. Timing of ventricular tachycardia (VT ≥3 beats) was assessed during 24-h continuous monitoring (Holter, implantable loop recorder, implantable cardioverter defibrillator) and by eliminating sleep hours, in addition to sporadic exercise stress tests. Morning was defined as 6:00 am to 11:59 am, afternoon 12:00 pm to 5:59 pm, and evening 6:00 pm to 11:59 pm. Distribution of VT events was compared by time of day, day of week, age, and sex. RESULTS: Eighty patients (53% male), 61% with an ICD, experienced 423 VT events during a median follow-up time of 6 years (interquartile range: 2 to 10 years). When compared to morning hours, VT was more likely to occur in the afternoon (odds ratio [OR]: 2.54; 95% confidence interval [CI]: 1.69 to 3.83) or evening hours (OR: 2.91; 95% CI: 1.82 to 4.67). The predominance of afternoon/evening events persisted regardless of age, gender, or day of the week. Among 50 patients who underwent exercise stress tests, VT was significantly more likely to occur in the afternoon (OR: 3.00; 95% CI: 1.39 to 6.48). CONCLUSIONS: In pediatric CPVT patients, ventricular arrhythmias are more likely to occur in the afternoon and evening hours. Because children's activity levels peak in both the morning and afternoon, the lack of arrhythmias in the morning hours raises questions whether factors other than adrenergic stimulation influence arrhythmia induction in pediatric patients with CPVT.

Follow-Up of Electrocardiographic Findings and Arrhythmias in Patients With Anomalously Arising Left Coronary Artery from the Pulmonary Trunk.

Follow-up data and correlation of arrhythmias, electrocardiogram (ECG) changes, and cardiac function in anomalous left coronary artery from the pulmonary trunk or artery have not been previously studied. This is a retrospective single-center review of 44 anomalous left coronary artery from the pulmonary trunk or artery patients diagnosed between 1992 and 2014, at a median age of 3 months (3 days to 13 years). Clinical history, ECG, Holter, and echocardiogram data were reviewed. ECGs were reviewed for contiguous Q-or T-wave inversions, hypertrophy, bundle branch block, and axis deviation. High-grade ventricular ectopy, supraventricular tachycardia (SVT), and ventricular tachycardia (VT) were recorded. Patients with <6 months of clinical follow-up were excluded from longitudinal analysis. At diagnosis, 43 (98%) were noted to have electrocardiographic changes. During hospitalization, arrhythmias were seen in 13 patients (30%): 2 (5%) with sustained VT or ventricular fibrillation, 6 (17%) with high-grade ventricular ectopy, and 4 (9%) with SVT. Seven patients (16%) required antiarrhythmic treatment. During outpatient follow-up, arrhythmias were seen in 11 patients. New arrhythmias were documented in 6 without a history of in-hospital arrhythmias. Of 34 patients with at least 6 months follow-up (median 6 years, 0.5 to 20 years), 20 had left ventricular (LV) dysfunction before surgery. Normalization of function occurred in 94% (median 1 year, 5 days to 4 years). Electrocardiographic changes persisted in 94% at the time of LV function recovery. In conclusion, electrocardiographic changes and arrhythmias may persist despite recovery of ventricular function. Therefore, prolonged myocardial remodeling may continue even after resolution of LV dysfunction during which time arrhythmias may occur.

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.