Double Ventricular Response with Aberrant Conduction Leading to Ventricular Dysfunction.

Double ventricular response (DVR), where a single P wave results in two QRS complexes, is a rare presentation of dual AV node physiology. It has been associated with ventricular dysfunction in the setting of incessant tachycardia. We present the case of an otherwise healthy adolescent who had frequent DVR without tachycardia leading to left ventricular dysfunction. Slow pathway modification led to a significant reduction in ectopy and normalization of ventricular function. This highlights that DVR without tachycardia might lead to ventricular dysfunction in pediatric patients. Slow pathway modification with reduction of ectopy may be sufficient to restore ventricular function.

Atrial Standstill in the Pediatric Population: A Multi-Institution Collaboration.

BACKGROUND: Atrial standstill (AS) is a rare condition characterized by absence of electrical activity within the atria. Studies to date have been limited. OBJECTIVES: The authors sought to describe the clinical characteristics, genetics, and outcomes of patients with AS. METHODS: This was a retrospective multicenter study of patients <18 years at AS diagnosis, defined as absence of atrial activity documented during an electrophysiology study, device placement, or noninvasive rhythm tracings and confirmed by echocardiogram. Patients with acquired disorders were excluded. Clinical details and genetic variants were recorded and analyzed. RESULTS: Twenty patients were diagnosed at a median age of 6.6 years (IQR: 2.9-10.8 years). Arrhythmias included 16 (80%) with atrial/supraventricular arrhythmias and 8 (40%) with ventricular tachycardia, including 4 with cardiac arrests. A type 1 Brugada pattern was documented in 4. Pacemakers were implanted in 18 (90%). Although atrial leads were attempted in 15, only 4 achieved pacing at implantation. During a median follow-up of 6.9 years (IQR: 1.2-13.3 years), 7 (35%) had thromboembolic events. Of these, none had atrial pacing, 6 were not on anticoagulation, and 1 was on aspirin. Genetic testing identified SCN5A variants in 13 patients (65%). Analyses suggest SCN5A loss-of-function may be one mechanism driving AS. Ventricular arrhythmias and cardiac arrest were more commonly seen in patients with biallelic SCN5A variants. CONCLUSIONS: AS may be associated with loss-of-function SCN5A variants. Patients demonstrate atrial and ventricular arrhythmias, and may present challenges during device placement. Patients without the capacity for atrial pacing are at risk for thromboembolic events and warrant anticoagulation.

Arrhythmia Burden and Heart Rate Response During Exercise in Anderson-Fabry Disease.

Patients with Anderson-Fabry disease (AFD) have an elevated incidence of resting arrhythmias and ischemic heart disease, but their exercise arrhythmia burden and ischemic changes are not well understood. In addition, little research has been done on heart rate recovery in these patients. We retrospectively reviewed charts of patients with AFD who underwent maximal effort cardiopulmonary exercise testing (CPET) (n=44; 38.2 ± 13.8 yr; 23 men) from 2012 through 2018. Electrocardiographic, Holter monitoring, echocardiographic, cardiac magnetic resonance imaging, and patient demographic data were collected. No patient had adverse events that necessitated CPET termination, whereas 25 (57%) had ectopy during CPET, including 3 (7%) with frequent premature atrial contractions and 5 (11%) with frequent premature ventricular contractions. The ectopic burden was higher during resting electrocardiographic monitoring before exercise. In addition, 7 patients (16%) had pathologic ST-segment or T-wave changes on CPET, defined as ST-segment changes ≥2 mm. Among the patients who had concurrent cardiac magnetic resonance findings with their CPET (n=27), ST-segment or T-wave changes were associated with left ventricular myocardial mass (r=0.43, P=0.02). Chronotropic incompetence was seen during CPET in 28 patients (64%); however, only 2 patients (4%) had abnormal heart rate recovery at 1 minute. This study shows that patients with AFD can safely undergo exercise testing but have a high incidence of exercise-induced arrhythmias and ischemic changes. Ischemic electrocardiographic changes during exercise testing are associated with myocardial mass. Despite the chronotropic incompetence associated with AFD, heart rate recovery appears to be generally preserved in these patients.

Off-Label Prescription of COVID-19 Vaccines in Children: Clinical, Ethical, and Legal Issues.

The US Food and Drug Administration (FDA) approval of the biologics license application for the Pfizer-BioNTech coronavirus disease 2019 vaccine (Comirnaty) on August 23, 2021, opened the door to the off-label vaccination of children younger than the age range currently covered by either the biologics license application (16 years old and older) or the emergency use authorization (12 to 15 years old). Although prescribing medications at doses, for conditions, or in populations other than those approved by the FDA is generally legal and is common in pediatrics, the FDA, the Centers for Disease Control and Prevention, and the American Academy of Pediatrics have recommended against off-label prescription of the coronavirus disease 2019 vaccine. Several commentaries consider a case in which parents ask their child's pediatrician to prescribe the vaccine for their 11-year-old with special health care needs before approval or authorization in her age group. The first commentary considers the potential benefits and risks to the patient, as well as to the family, the provider, and society, emphasizing the unknown risks in younger patients and the need for adequate informed consent. The second commentary describes an algorithm and principles for evaluating off-label prescribing and argues that the current benefits of prescribing Comirnaty off label to children <12 do not outweigh the risks. The third commentary addresses ethical and legal issues, ultimately calling on federal agencies to remove legal barriers to making the vaccine available to children in age groups that currently lack authorization.

Outcomes of Implantable Loop Monitoring in Patients <21 Years of Age.

Rhythm-symptom correlation in pediatric patients with syncope/palpitations or at risk cohorts can be difficult, but important given potential associations with treatable or malignant arrhythmia. We sought to evaluate the use, efficacy and outcomes of implantable loop recorders (ILR) in pediatrics. We conducted a retrospective study of pediatric patients (<21 years) with implanted ILR. Patient/historical characteristics and ILR indication were obtained. Outcomes including symptom documentation, arrhythmia detection and ILR based changes in medical care were identified. Comparison of outcomes were performed based on implant indication. Additional sub-analyses were performed in syncope-indication patients comparing those with and without changes in clinical management. A total of 116 patients with ILR implant were identified (79 syncope/37 other). Symptoms were documented 58% of patients (syncope 68% vs nonsyncope 35%; p = 0.002). A total of 37% of patients had a documented clinically significant arrhythmia and 25% of patients had a resultant change in clinical management independent of implant indication. Arrhythmia type was dependent on implant indication with nonsyncope patients having more ventricular arrhythmias. Pacemaker/defibrillator implantation and mediation management were the majority of the clinical changes. In conclusion, IRL utilization in selected pediatric populations is associated with high efficacy and supports clinical management. ILR efficacy is similar regardless of indication although patients with nonsyncope indications had a higher frequency of ventricular arrhythmias as opposed to asystole and heart block in syncope indications. The majority of arrhythmic findings occurred in the first 12 months, and new technology that would allow for less invasive monitoring for 6 to 12 months may be of value.

Updated International Tuberous Sclerosis Complex Diagnostic Criteria and Surveillance and Management Recommendations.

BACKGROUND: Tuberous sclerosis complex (TSC) is an autosomal dominant genetic disease affecting multiple body systems with wide variability in presentation. In 2013, Pediatric Neurology published articles outlining updated diagnostic criteria and recommendations for surveillance and management of disease manifestations. Advances in knowledge and approvals of new therapies necessitated a revision of those criteria and recommendations. METHODS: Chairs and working group cochairs from the 2012 International TSC Consensus Group were invited to meet face-to-face over two days at the 2018 World TSC Conference on July 25 and 26 in Dallas, TX, USA. Before the meeting, working group cochairs worked with group members via e-mail and telephone to (1) review TSC literature since the 2013 publication, (2) confirm or amend prior recommendations, and (3) provide new recommendations as required. RESULTS: Only two changes were made to clinical diagnostic criteria reported in 2013: "multiple cortical tubers and/or radial migration lines" replaced the more general term "cortical dysplasias," and sclerotic bone lesions were reinstated as a minor criterion. Genetic diagnostic criteria were reaffirmed, including highlighting recent findings that some individuals with TSC are genetically mosaic for variants in TSC1 or TSC2. Changes to surveillance and management criteria largely reflected increased emphasis on early screening for electroencephalographic abnormalities, enhanced surveillance and management of TSC-associated neuropsychiatric disorders, and new medication approvals. CONCLUSIONS: Updated TSC diagnostic criteria and surveillance and management recommendations presented here should provide an improved framework for optimal care of those living with TSC and their families.

Progressive QRS Duration and Ventricular Dysfunction in Pediatric Patients with Chronic Ventricular Pacing.

Pacemakers are a mainstay of therapy for patients with congenital and acquired heart block, but ventricular pacing is related to ventricular dysfunction. We sought to evaluate patient and device characteristics associated with ventricular dysfunction in pediatric patients with chronic ventricular pacing. This was a retrospective cohort of pediatric patients with heart block and chronic ventricular pacing. Patient, ECG, and device characteristics were analyzed to determine factors associated with ventricular dysfunction. Longitudinal ECG and echocardiogram parameters were obtained to track changes in QRS and systemic ventricular systolic function over time. In total, 82 patients were included (median age at implant 0.81 years). Over a follow-up time of 6.1 years, 18% developed ventricular dysfunction. Patients with dysfunction had greater current QRS duration (p = 0.002) compared to those with preserved function with a similar time from device implantation. There was no difference between lead location or age at device implantation. QRS duration increased with time from implant and the resultant ΔQRS was associated with ventricular dysfunction (p = 0.01). QRS duration >162 ms was associated with a 5.8 (2-9)-fold increased risk for dysfunction. Transvenous leads were associated with longer QRS duration with no difference compared to epicardial leads in development of ventricular dysfunction. This study demonstrated that the absolute paced QRS duration and Δpaced QRS were association with long-term ventricular dysfunction independent of how long a given patient was paced. Patients in high-risk categories may benefit from close echocardiographic monitoring. Whether permissive junctional rhythm or His bundle/biventricular pacing decreases the rate of dysfunction needs further study.

Time series evaluation of improvement interventions to reduce alarm notifications in a paediatric hospital.

BACKGROUND10: The Joint Commission identified inpatient alarm reduction as an opportunity to improve patient safety; enhance patient, family and nursing satisfaction; and optimise workflow. We used quality improvement (QI) methods to safely decrease non-actionable alarm notifications to bedside providers. METHODS: In a paediatric tertiary care centre, we convened a multidisciplinary team to address alarm notifications in our acute care cardiology unit. Alarm notification was defined as any alert to bedside providers for each patient-triggered monitor alarm. Our aim was to decrease alarm notifications per monitored bed per day by 60%. Plan-Do-Study-Act testing cycles included updating notification technology, establishing alarm logic and modifying bedside workflow processes, including silencing the volume on all bedside monitors. Our secondary outcome measure was nursing satisfaction. Balancing safety measures included floor to intensive care unit transfers and patient acuity level. RESULTS: At baseline, there was an average of 71 initial alarm notifications per monitored bed per day. Over a 3.5-year improvement period (2014-2017), the rate decreased by 68% to 22 initial alarm notifications per monitored bed per day. The proportion of initial to total alarm notifications remained stable, decreasing slightly from 51% to 40%. There was a significant improvement in subjective nursing satisfaction. At baseline, 32% of nurses agreed they were able to respond to alarms appropriately and quickly. Following interventions, agreement increased to 76% (p<0.001). We sustained these improvements over a year without a change in monitored balancing measures. CONCLUSION: We successfully reduced alarm notifications while preserving patient safety over a 4-year period in a complex paediatric patient population using technological advances and QI methodology. Continued efforts are needed to further optimise monitor use across paediatric hospital units.

Wearable cardioverter-defibrillators in pediatric cardiomyopathy: A cost-utility analysis.

BACKGROUND: Dilated cardiomyopathy (DCM) is the most common cardiomyopathy in children. Patients with severe cardiac dysfunction are thought to be at risk of sudden cardiac arrest (SCA). After diagnosis, a period of medical optimization is recommended before permanent implantable cardioverter-defibrillator (ICD) implantation. Wearable cardioverter-defibrillators (WCDs) provide an option for arrhythmia protection as an outpatient during this optimization. OBJECTIVE: The purpose of this study was to determine the strategy that optimizes cost and survival during medical optimization of a patient with DCM before ICD placement. METHODS: A Markov state transition model was constructed for the 3 clinical approaches to compare costs, clinical outcomes, and quality of life: (1) "Inpatient," (2) "Home-WCD," and (3) "Home-No WCD." Transitional probabilities, costs, and utility metrics were extracted from the existing literature. Cost-effectiveness was assessed comparing each paradigm's incremental cost-effectiveness ratio against a societal willingness-to-pay threshold of $50,000 per quality-adjusted life year. RESULTS: The cost-utility analysis illustrated that Home-WCD met the willingness-to-pay threshold with an incremental cost-effectiveness ratio of $20,103 per quality-adjusted life year and 4 mortalities prevented per 100 patients as compared with Home-No WCD. One-way sensitivity analyses demonstrated that Home-No WCD became the most cost-effective solution when the probability of SCA fell below 0.2% per week, the probability of SCA survival with a WCD fell below 9.8%, or the probability of SCA survival with Home-No WCD quadrupled from base-case assumptions. CONCLUSION: Based on the existing literature probabilities of SCA in pediatric patients with DCM undergoing medical optimization before ICD implantation, sending a patient home with a WCD may be a cost-effective strategy.

Can noninvasive testing identify benign patterns of suggested pre-excitation on electrocardiogram?

BACKGROUND: The presence of anterograde conduction through an accessory pathway (AP) has been linked to sudden cardiac death. Unfortunately, pre-excitation associated with classic pathways can be difficult to differentiate from benign APs such as nodofascicular fibers. OBJECTIVE: Identifying characteristics on electrocardiogram (ECG) and exercise that differentiate classic and benign AP connections in suggested pre-excitation patterns. METHODS: Retrospective review of patients presenting between 1995 and 2017 with ventricular pre-excitation on ECG, determined to have either typical left-lateral AP during electrophysiology study (EPS), or benign, or no AP determined by either transesophageal electrophysiology study (TEP), or EPS. RESULTS: A total of 96 patients were included, 14.2 years (4-24), 45% female, 90% Caucasian. Of these, 60 (63%) had a classic APs identified on EPS and 58 (97%) underwent successful ablation. Conversely, 36 (37%) had benign pathways identified. ECG findings differed between the groups: PR-interval 102 versus 120 ms (P < .0001), QRS-duration 110 versus 102 ms (P < .0001), QRS-axis 74 versus 59 degrees (P = .0005), and QRS onset to peak R/S in limb leads 64 versus 42 ms (P < .0001), and precordial leads 66 versus 46 ms (P < .0001). Change in QRS duration during exercise differed between the groups: 25 versus 2 ms (P < .0001) and ECG characteristics identified the presence of an AP with 97% sensitivity and 94% negative predictive value. CONCLUSION: Classic and benign APs exhibit different ECG characteristics, though clinical overlap does not allow for absolute differentiation. These data may help with risk stratification decision making though does not obviate the need for additional invasive testing.

In Vivo Remodeling of an Extracellular Matrix Cardiac Patch in an Ovine Model.

Lack of an ideal patch material for cardiac repairs continues to challenge congenital heart surgeons. The current materials are unable to grow and result in scarring, contraction, and arrhythmias. An acellular extracellular matrix (ECM) patch derived from porcine small intestinal submucosa has demonstrated remodeling potential when used to repair various tissues. This study investigated the in vivo electrophysiologic, mechanical, and histological properties of an ECM patch used to repair a right-ventricular (RV) wall defect in a growing ovine model. A full-thickness, 2 × 2 cm RV defect was created in 11 juvenile sheep and repaired with an ECM patch. Longitudinal RV three-dimensional-electrical mapping, magnetic resonance imaging (MRI), and histological analysis were performed at 3, 6, 9, and 12 months. Three-dimensional mapping demonstrated consistent conduction across the patch with little to no difference in voltage, but conduction velocity was consistently less than native myocardium. Magnetic resonance imaging revealed changing strain properties of the patch which by 9-12 months resembled native tissue. Histologic analysis at 3 months demonstrates cardiomyocyte degeneration and partial replacement via proliferation of connective tissue cells that were predominately fibroblasts and smooth muscle cells. There was marked neovascularization and an absence of calcification at 12 months. Over time, the ECM patch remained viable with stable muscle at the edges. In growing sheep, an ECM patch becomes a viable tissue and remains so up to at least a year. Although ECM demonstrates some functional aspects of remodeling to native myocardium, histologically it remained immature.

Ventricular force-frequency relationships during biventricular or multisite pacing in congenital heart disease.

BACKGROUND: Traditional indices to evaluate biventricular (BiV) pacing are load dependent, fail to assess dynamic changes, and may not be appropriate in patients with congenital heart disease (CHD). We therefore measured the force-frequency relationship (FFR) using tissue Doppler-derived isovolumic acceleration (IVA) to assess the dynamic adaption of the myocardium and its variability with different ventricular pacing strategies. METHODS: This was a prospective pilot study of pediatric and young adult CHD patients with biventricular or multisite pacing systems. Color-coded myocardial velocities were recorded at the base of the systemic ventricular free wall. IVA was calculated at resting heart rate and with incremental pacing. FFR curves were obtained by plotting IVA against heart rate for different ventricular pacing strategies. RESULTS: Ten patients were included (mean: 22 ± 7 years). The FFR identified a best and worst ventricular pacing strategy for each patient, based on the AUC at baseline, submaximal, and peak heart rates (P < .001). However, there was no single best ventricular pacing strategy that was optimal for all patients. Additionally, the best ventricular pacing strategy often differed within the same patient at different heart rates. CONCLUSION: This novel assessment demonstrates a wide variability in optimal ventricular pacing strategy. These inherent differences may play a role in the unpredictable clinical response to BiV pacing in CHD, and emphasizes an individualized approach. Furthermore, the optimal ventricular pacing varies with heart rate within individuals, suggesting that rate-responsive ventricular pacing modulation may be required to optimize ventricular performance.

Atrioventricular accessory pathways in 89 dogs: Clinical features and outcome after radiofrequency catheter ablation.

BACKGROUND: Atrioventricular accessory pathways (APs) in dogs have been reported rarely. Data regarding clinical presentation and long-term outcome after radiofrequency catheter ablation (RFCA) are limited. HYPOTHESIS/OBJECTIVES: To study clinical features, electrophysiologic characteristics, and outcome of RFCA in dogs with APs. ANIMALS: Eighty-nine dogs presented consecutively for RFCA of APs. METHODS: Case series. RESULTS: Labrador retrievers (47.2% of dogs) and male dogs (67.4% of dogs) were most commonly affected. Labrador retrievers were more likely to be male than non-Labrador breeds (P = .043). Clinical signs were nonspecific and most commonly included lethargy and gastrointestinal signs. Concealed APs were more prevalent in Labrador retrievers than other breeds (P = .001). Right-sided APs (91.7%) predominated over left-sided (8.3%). Tachycardia-induced cardiomyopathy (TICM) occurred in 46.1% of dogs, with complete resolution or substantial improvement noted on one-month postablation echocardiograms. Radiofrequency catheter ablation successfully eliminated AP conduction long term in 98.8% of dogs in which it was performed. Complications occurred in 5/89 dogs. Recurrence in 3 dogs was eliminated long term with a second procedure. CLINICAL IMPORTANCE/CONCLUSIONS: Accessory pathways are challenging to recognize in dogs because of nonspecific clinical signs, frequency of concealed APs that show no evidence of their presence during sinus rhythm, and intermittent occurrence of tachyarrhythmias resulting from APs. Tachycardia-induced cardiomyopathy commonly occurs with AP-mediated tachycardias and should be considered in any dog presenting with a dilated cardiomyopathic phenotype because of its good long-term prognosis with rhythm control. Radiofrequency catheter ablation is a highly effective method for eliminating AP conduction and providing long-term resolution.

The US Experience of the Wearable Cardioverter-Defibrillator in Pediatric Patients.

BACKGROUND: Certain pediatric patients are at risk for sudden cardiac death. The wearable cardioverter-defibrillator (WCD) can be used in clinical situations in which implantable cardioverter-defibrillator placement is not ideal. The objectives of the study are to examine the effectiveness, safety, and compliance of the WCD in the identification and treatment of life-threatening ventricular arrhythmias in pediatric patients. METHODS: All United States pediatric patients <18 years who wore a WCD, from 2009 to 2016 were retrospectively reviewed. RESULTS: In total, 455 patients were identified. The median age was 15 (3-17) years, median duration of WCD use was 33 (1-999) days and median patient wear time was 20.6 (0.3-23.8) hours per day. The population was divided into 2 groups: (1) patients with implantable cardioverter-defibrillator problem, n=63 and (2) patients with nonimplantable cardioverter-defibrillator problem, n=392. Wear time per day was >20 hours in both groups. Wear duration was shorter in the implantable cardioverter-defibrillator problem group, 26 days versus 35 days, P<0.05. There were 7 deaths (1.5%); all not wearing WCD at time of death. Eight patients (1.8%) received at least 1 WCD shock treatment. Of the 6 patients (1.3%) who had appropriate therapy, there were 7 episodes of either polymorphic ventricular tachycardia or ventricular fibrillation with a total of 13 treatments delivered. All episodes were successfully converted and the patients survived. CONCLUSIONS: The WCD has overall adequate compliance with appropriate wear times and wear durations in pediatric patients. The WCD is safe and effective in treating ventricular arrhythmias that can lead to sudden cardiac death in pediatric patients.

Risks and outcomes of direct current cardioversion in children and young adults with congenital heart disease.

OBJECTIVES: Evaluate the efficacy, outcomes, and complications associated with direct current cardioversion (DCCV) in the treatment of arrhythmias in pediatric and adult congenital heart disease (CHD) populations and identify patient and procedural characteristics associated with adverse events. BACKGROUND: Pediatric and adult patients with CHD are at risk of atrial arrhythmias. DCCV is effective but is associated with potential complications. METHODS: In this single-center retrospective series, patients who underwent DCCV between January 2010 and May 2015 were identified and categorized as pediatric (<18 years) or adult (> 18 years). Records were reviewed for demographic, arrhythmic, and CHD-specific characteristics; acute efficacy; and 3-month arrhythmia recurrence. Complications were categorized as life-threatening (LT) or non-life-threatening (NLT). Univariate followed by multiple variable and logistic regression (LR) analyses were used to identify characteristics associated with complications. RESULTS: We identified 104 patients with 152 discrete DCCV events with median age 17.4 years (0.15-62.2). DCCV efficacy was 89% with 3-month recurrence of 46%. There were 52 complications among 24 patients, median age 17.7 years (0.15-49). Risks associated with NLT complications are as follows: moderate-severe systolic dysfunction (8/152 encounters, P = < 0.01) and more than one shock per DCCV encounter (P = < 0.01). Six of eight encounters with moderate-severe systolic dysfunction were <18 years (P = 0.1). Risks for LT complications included age >18 years and associated NLT complication. Adults had more frequent arrhythmia recurrence within 3 months than children (P = < 0.01). CONCLUSIONS: DCCV is effective for arrhythmias but is associated with frequent recurrence, particularly in adult patients. Complications associated with DCCV may be greater than previously reported. Additional support and precautions should be in place for those at greatest risk.