JET (junctional ectopic tachycardia) is a complicated and rare form of supraventricular tachycardia that is associated with a high rate of morbidity and mortality. Pharmaceutical management can be insufficient, and cryoablation has been described for congenital JET management. We describe cryoablation for congenital JET in an prior 32-week gestational aged, 18-month-old (corrected 16-month-old) with no JET post-ablation with normal Holter and follow-up within 6 months following cryoablation. This report demonstrates the safety and feasibility of cryoablation in patients as young as 18 months old.

BACKGROUND: Idiopathic ventricular fibrillation (VF) is a diagnosis of exclusion made in patients who experience VF without an attributable cause. Pathogenic variants of the ACTN2 gene encoding the sarcomeric protein alpha-actinin-2 are known to cause hypertrophic and dilated cardiomyopathy. We show that ACTN2 variants may also be associated with malignant arrhythmias in the absence of overt structural heart disease. CASE SUMMARY: A 48-year-old female presented with cardiac arrest due to VF without any history of cardiovascular disease or family history of sudden cardiac death. Troponin I was elevated at 0.698 ng/mL, but coronary angiography showed no significant coronary artery disease. Substance abuse testing showed elevated benzodiazepine and sertraline levels, which she was taking for anxiety. Electrocardiogram showed normal QRS complexes without prolonged PR or QTc intervals. She underwent therapeutic hypothermia. Cardiac magnetic resonance imaging at 2 weeks showed normal biventricular function without structural abnormalities, fibrosis, or evidence of myocardial infarction. A targeted gene panel revealed a heterozygous missense variant of unknown significance (VUS) in exon 18 of the ACTN2 gene (c.2162G > A/p.R721H). DISCUSSION: The identified VUS is located in a highly conserved residue of a spectrin-like repeat domain of alpha-actinin-2. Spectrin-like domains of alpha-actinin-2 bind and regulate the ion channels Nav1.5, Kv1.4, and Kv1.5, which contribute to the myocardial action potential. The VUS was predicted as pathogenic by MutationTaster, Polymorphism Phenotyping v2, and Sorting Intolerant From Tolerant in silico missense prediction tools. The c.2162G > A/p.R721H alpha-actinin-2 variant may result in dysregulation of cardiac ion channels, leading to arrhythmias.

INTRODUCTION: Congenital heart disease may present in up to 1.6 % of newborns. Given high burden of pacing need in adult patients with repaired congenital heart disease and availability of different pacing options, more information on outcomes of newer pacemaker types are needed. Retrievable leadless pacemaker implants in adult congenital patients have not been described. METHODS: Retrospective review of three Aveir (Abbott) retrievable leadless pacemaker implants were reviewed at the UC Davis Medical Center. All patients underwent implant via femoral access. RESULTS: All patients had one deployment only, after mapping prior. No complications occurred. Implant thresholds were 0.5 V (V) @0.2msilliseconds (ms) for patients 1 and 2 and 1 V @0.4 ms for patient 3. With impedances between 500 and 1290 Ω. Sensing was 5.5-8 mV (mV). Follow-up occurred up to one year (for two patients) with similar values overall. The predicted longevities of each device were between 22.6 and >25 years. CONCLUSION: Safety and short-mid-term parameters of retrievable leadless pacemaker implantation is reported in three patients with adult congenital heart disease.

UNLABELLED: Adult congenital heart disease patients may undergo numerous fluoroscopically guided procedures including pacemaker implantation during their lifetime. One alternative to traditional pacemaker setup which may improve long-term pacing outcomes is His bundle pacing. Given the altered His-bundle location, and given increased radiation exposure over a lifetime, we used 3-dimensional mapping to locate the His and to minimize fluoroscopy for placement of a His-bundle pacemaker system in a 31-year old patient with atrioventricular canal defect and complete heart block with 100% RV pacing and epicardial lead fracture. METHODS: An Octapolar Livewire catheter (Abbott, Minneapolis, USA) was used for mapping and location of the His bundle from a right femoral venous access on the EnSite Precision system 3-dimensional mapping system (Abbott Medical, Abbott Park, IL). The same map was used to guide 3830 lead placement into the posterior-inferior His-bundle position. RESULTS: Successful placement of a His-bundle pacing system with thresholds of 1Volt@0.4ms for both the atrial and ventricular leads with selective His-bundle pacing noted. Ten-month follow-up demonstrated His-bundle capture at 0.75V@0.4ms with stable impedance, sensing and with 100% right ventricular pacing a projected longevity of 12 years total. CONCLUSIONS: Successful placement of selective His-bundle pacing can be achieved in an adult patient with atrioventricular canal defect using 3-dimensional mapping.

Leadless pacemakers have provided new treatment modalities that can be especially useful in patients with complex cardiac anatomy and contraindications toward other pacemaker approaches. The Aveir™ single-chamber (VR) leadless pacemaker (LP) (Abbott Laboratories, Chicago, IL) is a recently approved device that can be placed in the right ventricle for patients with bradycardia. In this case, we present a novel use for the device through placement in the atrium to control atrial flutter in a patient with a hypoplastic right ventricle.

BACKGROUND: There is paucity of data regarding the significance of high percentage of premature ventricular contractions (PVCs) in healthy children and their impact on left ventricular (LV) function and the risk of ventricular arrhythmias. The purpose of this study was to assess the prevalence of LV systolic dysfunction in children with frequent PVCs and determine whether PVC characteristics were predictive of LV dysfunction. METHODS: We performed a single-center retrospective review to examine the prevalence of PVC-induced cardiomyopathy and natural history of PVC burden in children with frequent PVCs. Children aged 6 months-21 years with PVCs noted on 24-hr Holter monitoring studies were enrolled. The four categories included those with a PVC burden of >10%, 10%-20%, and those with more than 20% PVC burden. RESULTS: A total of 134 children were included, 65 with more than 10% PVCs and 31 with more than 20% PVCs. Median age of the patients was 10.5 years (IQR 6.1-14.8 years), with 79 males (54.5%). Median PVC burden was 8.7% (IQR 4.2%-16.9%) with median follow-up of 2.8 years (IQR 1.2-4.6 years). During 2.8 years (1.3-4.3 years) of follow-up, the PVC burden decreased by 67% of baseline PVC burden in those who did not undergo any intervention. There were no deaths. CONCLUSION: PVCs in children with structurally normal hearts are associated with a relatively benign course, with trend toward spontaneous resolution.

INTRODUCTION: Noncompaction cardiomyopathy (NCCM) patients may develop sustained ventricular arrhythmias (VA). Currently no known electrocardiogram (ECG) parameter has demonstrated predictive value for VA development. The spatial QRS-T angle has demonstrated ability to identify VA in other cardiomyopathy populations. METHODS: A total of 39 patients with NCCM, defined by compact to non-compact ratio of >2.3 by magnetic resonance imaging, were assessed. The first ECG taken at time of MRI was assessed utilizing the heart rate, the QRS duration (QRSd), the corrected QT interval (QTc), and the spatial QRS-T angle (SPQRS-T angle, three-dimensional angle between the QRS and T-wave vectors) were assessed. RESULTS: Eight patients developed VA (20.5%). Median time to event was 3 months (95% CI 1.0 to 24.0 months). There were no significant differences between baseline ejection fraction or fractional shortening. Baseline median heart rate, spatial QRS-T angles, and indexed left ventricular end-diastolic volumes were all significantly higher in patients with VA development (p-value <0.05). Only heart rate and the SPQRS-T angle had significant univariate hazard ratios (HR) for VA at 1.031/beat per minute (1.001-1.071) and at a cut-off of 147 degrees the SPQRS-T angle gave a hazard ratio of HR of 5.773 (95% CI 1.161 to 28.702). The multivariate hazard ratio was only significant for the SPQRS-T angle, 1.031/degree (1.001-1.066). Survival analysis by Kaplan-Meier yielded a significant difference at a cutoff of 147 degrees. CONCLUSION: The SPQRS-T angle identified those at risk for VA development. Future studies are warranted with larger populations of noncompaction patients.

His-bundle pacing has demonstrated feasibility in numerous adult studies to reverse and prevent pacing-induced cardiomyopathy, however, is met with higher capture thresholds with deployment sheaths designed for adults with his-bundles in the typical location. To describe 24 pediatric and adult congenital patients post-physiologic pacing. Patients at the University of Minnesota Masonic Childrens Hospital with congenital complete heart block or congenital heart disease and atrioventricular block presented for pacemaker placement between November 2019 and January 2021. Twenty-four patients had attempted his-bundle placement using either Medtronics C315 or C308 sheaths and 3830 leads except for 3 patients who had Boston Scientifics His system with the Shape 3 sheath and 7842 leads. Twenty-four total patients underwent physiologic pacing (23 his-bundle, 13 female, 11 male) with median age of 14 years (range 8-39 years) with median weight of 51 kg (range 21.2-81 kg) with five right-sided implants performed. Twelve patients had congenital heart disease including atrioventricular canal defects, tetralogy of Fallot, and ventricular septal defect repairs (nine patients with ventricular septal defect repairs). Twelve patients had selective His-bundle pacing (six with congenital heart disease). Median threshold to capture was 0.5 V at 0.4 ms (range 0.4 to 1.1 V at 0.4 ms), impedance 570 ohms (range 456-1140 ohms), and sensing median of 9.7 mV (range 1.5-13.8 mV if present). The median follow-up time was 610 days (range 240-760 days). No complications occurred peri-procedurally or during follow-up. His-bundle pacing is feasible in pediatric and congenital heart disease patients.

BACKGROUND: The incidence of Lyme disease (LD) in North America has increased substantially in the past two decades. Concomitant with the increased incidence of infection has been an enhancement in the recognition of LD complications. Here, we report a case of Lyme carditis complicated by heart block in a pediatric patient admitted to our childrens hospital. What is unique about this case is that the complaint of chest palpitations is an infrequent presentation of LD, and what it adds to the scientific literature is an improved understanding of LD in the pediatric population. CASE PRESENTATION: The patient was a 16-year-old male who presented with the main concerns of acute onset of palpitations and chest pain. An important clinical finding was Erythema migrans (EM) on physical exam. The primary diagnoses were LD with associated Lyme carditis, based on the finding of 1st degree atrioventricular heart block (AVB) and positive IgM and IgG antibodies to Borrelia burgdorferi. Interventions included echocardiography, electrocardiography (EKG), and intravenous antibiotics. The hospital course was further remarkable for transition to 2nd degree heart block and transient episodes of complete heart block. A normal sinus rhythm and PR interval were restored after antibiotic therapy and the primary outcome was that of an uneventful recovery. CONCLUSIONS: Lyme carditis occurs in < 5% of LD cases, but the take-away lesson of this case is that carditis can be the presenting manifestation of B. burgdorferi infection in pediatric patients. Any patient with suspected Lyme carditis manifesting cardiac symptoms such as syncope, chest pain, or EKG changes should be admitted for parenteral antibiotic therapy and cardiac monitoring. The most common manifestation of Lyme carditis is AVB. AVB may manifest as first-degree block, or may present as high-grade second or third-degree block. Other manifestations of Lyme carditis may include myopericarditis, left ventricular dysfunction, and cardiomegaly. Resolution of carditis is typically achieved through antibiotic administration, although pacemaker placement should be considered if the PR interval fails to normalize or if higher degrees of heart block, with accompanying symptoms, are encountered. With the rising incidence of LD, providers must maintain a high level of suspicion in order to promptly diagnose and treat Lyme carditis.

Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a potentially lethal cardiac channelopathy characterized by episodes of ventricular tachycardia (VT) during exercise or in stressful situations. As the peripartum period creates a stressful environment, we describe our approach of this rare condition in a very common situation, child birth.