A mild phenotype associated with KCNQ1 p.V205M mediated long QT syndrome in First Nations children of Northern British Columbia: effect of additional variants and considerations for management.

Introduction: Congenital Long QT Syndrome (LQTS) is common in a First Nations community in Northern British Columbia due to the founder variant KCNQ1 p.V205M. Although well characterized molecularly and clinically in adults, no data have been previously reported on the pediatric population. The phenotype in adults has been shown to be modified by a splice site variant in KCNQ1 (p.L353L). The CPT1A p.P479L metabolic variant, also common in Northern Indigenous populations, is associated with hypoglycemia and infant death. Since hypoglycemia can affect the corrected QT interval (QTc) and may confer risk for seizures (also associated with LQTS), we sought to determine the effect of all three variants on the LQTS phenotype in children within our First Nations cohort. Methods: As part of a larger study assessing those with LQTS and their relatives in a Northern BC First Nation, we assessed those entering the study from birth to age 18 years. We compared the corrected peak QTc and potential cardiac events (syncope/seizures) of 186 children from birth to 18 years, with and without the KCNQ1 (p.V205M and p.L353L) and CPT1A variants, alone and in combination. Linear and logistic regression and student t-tests were applied as appropriate. Results: Only the KCNQ1 p.V205M variant conferred a significant increase in peak QTc 23.8 ms (p < 0.001) above baseline, with females increased by 30.1 ms (p < 0.001) and males by 18.9 ms (p < 0.01). There was no evidence of interaction effects with the other two variants studied. Although the p.V205M variant was not significantly associated with syncope/seizures, the odds of having a seizure/syncope were significantly increased for those homozygous for CPT1A p.P479L compared to homozygous wild type (Odds Ratio [OR]3.0 [95% confidence interval (CI) 1.2-7.7]; p = 0.019). Conclusion: While the KCNQ1 p.V205M variant prolongs the peak QTc, especially in females, the CPT1A p.P479L variant is more strongly associated with loss of consciousness events. These findings suggest that effect of the KCNQ1 p.V205M variant is mild in this cohort, which may have implications for standard management. Our findings also suggest the CPT1A p.P479L variant is a risk factor for seizures and possibly syncope, which may mimic a long QT phenotype.

Leadless Pacemakers in Patients with Congenital Heart Disease.

Transcatheter leadless pacemakers have benefits in congenital heart disease because they eliminate the risks of lead malfunction, venous occlusions, and pocket complications. This newest pacemaker's utility in this population has been limited by the large sheath and delivery system, need for atrioventricular synchronous pacing, lack of explantation options, and possible lack of adequate access to the subpulmonary ventricle. With careful planning, leadless pacing can be successfully performed in these patients. Consideration of nonfemoral access, alternative implant sites to avoid myocardial scar or prosthetic material, anticoagulation for patients with persistent intracardiac shunts or systemic ventricular implantation, and operator experience are critical.

Visit and Between-Visit Interaction Frequency Before and After COVID-19 Telehealth Implementation.

Importance: Telehealth implementation associated with the COVID-19 public health emergency (PHE) affected patient-clinical team interactions in numerous ways. Yet, studies have narrowly examined billed patient-clinician visits rather than including visits with other team members (eg, pharmacists) or between-visit interactions. Objective: To evaluate rates of change over time in visits (in-person, telehealth) and between-visit interactions (telephone calls, patient portal messages) overall and by key patient characteristics. Design, Setting, and Participants: This retrospective cohort study included adults with diabetes receiving primary care at urban academic (University of California San Francisco [UCSF]) and safety-net (San Francisco Health Network [SFHN]) health care systems. Encounters from April 2019 to March 2021 were analyzed. Exposure: Telehealth implementation over 3 periods: pre-PHE (April 2019 to March 2020), strict shelter-in-place (April to June 2020), and hybrid-PHE (July 2020 to March 2021). Main Outcomes and Measures: The main outcomes were rates of change in monthly mean number of total encounters, visits with any health care team member, visits with billing clinicians, and between-visit interactions. Key patient-level characteristics were age, race and ethnicity, language, and neighborhood socioeconomic status (nSES). Results: Of 15 148 patients (4976 UCSF; 8975 SFHN) included, 2464 (16%) were 75 years or older, 7734 (51%) were female patients, 9823 (65%) self-identified as racially or ethnically minoritized, 6223 (41%) had a non-English language preference, and 4618 (31%) lived in the lowest nSES quintile. After accounting for changes to care delivery through an interrupted time-series analysis, total encounters increased in the hybrid-PHE period (UCSF: 2.3% per patient/mo; 95% CI, 1.6%-2.9% per patient/mo; SFHN: 1.8% per patient/mo, 95% CI, 1.3%-2.2% per patient/mo), associated primarily with growth in between-visit interactions (UCSF: 3.1% per patient/mo, 95% CI, 2.3%-3.8% per patient/mo; SFHN: 2.9% per patient/mo, 95% CI, 2.3%-3.4% per patient/mo). In contrast, rates of visits were stable during the hybrid-PHE period. Although there were fewer differences in visit use by key patient-level characteristics during the hybrid-PHE period, pre-PHE differences in between-visit interactions persisted during the hybrid-PHE period at SFHN. Asian and Chinese-speaking patients at SFHN had fewer monthly mean between-visit interactions compared with White patients (0.46 [95% CI, 0.42-0.50] vs 0.59 [95% CI, 0.53-0.66] between-visit interactions/patient/mo; P < .001) and English-speaking patients (0.52 [95% CI, 0.47-0.58] vs 0.61 [95% CI, 0.56-0.66] between-visit interactions/patient/mo; P = .03). Conclusions and Relevance: In this study, pre-PHE growth in overall patient-clinician encounters persisted after PHE-related telehealth implementation, driven in both periods by between-visit interactions. Differential utilization based on patient characteristics was observed, which may indicate disparities. The implications for health care team workload and patient outcomes are unknown, particularly regarding between-visit interactions. Therefore, to comprehensively understand care utilization for patients with chronic diseases, research should expand beyond billed visits.

Impact of standardized, language-concordant hospital discharge instructions on postdischarge medication questions.

Written instructions improve patient comprehension of discharge instructions but are often provided only in English even for patients with a non-English language preference (NELP). We implemented standardized written discharge instructions in English, Spanish, and Chinese for hospital medicine patients at an urban academic medical center. Using an interrupted time series analysis, we assessed the impact on medication-related postdischarge questions for patients with English, Spanish, or Chinese language preferences. Of 4013 patients, ∼15% had NELP. Preintervention, Chinese-preferring patients had a 5.6 percentage point higher probability of questions (adjusted odds ratio [aOR] = 1.55, 95% confidence interval [CI]: 1.08, 2.21) compared to English-preferring patients; Spanish-preferring and English-preferring patients had similar rates of questions. Postintervention, English-preferring and Spanish-preferring patients had no significant change; Chinese-preferring patients had a significant 10.9 percentage point decrease in the probability of questions (aOR = 0.38, 95% CI: 0.21, 0.69) thereby closing the disparity. Language-concordant written discharge instructions may reduce disparities in medication-related postdischarge questions for patients with NELP.

Transcatheter Leadless Pacing in Children: A PACES Collaborative Study in the Real-World Setting.

BACKGROUND: Transcatheter Leadless Pacemakers (TLP) are a safe and effective option for adults with pacing indications. These devices may be an alternative in pediatric patients and patients with congenital heart disease for whom repeated sternotomies, thoracotomies, or transvenous systems are unfavorable. However, exemption of children from clinical trials has created uncertainty over the indications, efficacy, and safety of TLP in the pediatric population. The objectives of this study are to evaluate clinical indications, procedural characteristics, electrical performance, and outcomes of TLP implantation in children. METHODS: Retrospective data were collected from patients enrolled in the Pediatric and Congenital Electrophysiology Society TLP registry involving 15 centers. Patients ≤21 years of age who underwent Micra (Medtronic Inc, Minneapolis, MN) TLP implantation and had follow-up of ≥1 week were included in the study. RESULTS: The device was successfully implanted in 62 of 63 registry patients (98%) at a mean age of 15±4.1 years and included 20 (32%) patients with congenital heart disease. The mean body weight at TLP implantation was 55±19 kg and included 8 patients ≤8 years of age and ≤30 kg in weight. TLP was implanted by femoral (n=55, 87%) and internal jugular (n=8, 12.6%) venous approaches. During a mean follow-up period of 9.5±5.3 months, there were 10 (16%) complications including one cardiac perforation/pericardial effusion, one nonocclusive femoral venous thrombus, and one retrieval and replacement of TLP due to high thresholds. There were no deaths, TLP infections, or device embolizations. Electrical parameters, including capture thresholds, R wave sensing, and pacing impedances, remained stable. CONCLUSIONS: Initial results from the Pediatric and Congenital Electrophysiology Society TLP registry demonstrated a high level of successful Micra device implants via femoral and internal venous jugular approaches with stable electrical parameters and infrequent major complications. Long-term prospective data are needed to confirm the reproducibility of these initial findings.

Clinical factors associated with a positive postpartum depression screen in people with cardiac disease during pregnancy.

Background: While people with cardiac disease are known to be at increased lifetime risk of depression, little is known about postpartum depression rates in this population. Describing rates of positive postpartum depression screens and identifying risk factors that are unique to cardiac patients may help inform risk reduction strategies. Methods: This retrospective cohort study included pregnant patients with congenital and/or acquired cardiac disease who delivered at a single institution between 2014 and 2020. The primary outcome was a positive postpartum depression screen, defined as Edinburgh Postpartum Depression Score (EPDS) ≥10. Potential exposures were selected a priori and compared between patients with and without a positive postpartum depression screen using Wilcoxon rank-sum and Fisher's exact tests. Secondary outcomes were responses to a longitudinal follow-up survey sent to English-speaking patients evaluating cardiac status, mental health, and infant development. Results: Of 126 eligible cardiac patients, 23 (18.3%) had a positive postpartum depression screen. Patients with a positive postpartum depression screen were more likely to have had antepartum anticoagulation with heparin or enoxaparin (56.5% versus 26.2%, p=0.007), blood transfusion during delivery (8.7% versus 0%, p=0.032), and maternal-infant separation postpartum (52.2% versus 28.2%, p=0.047) compared to patients with a negative screen. Among 29 patients with a positive screen who responded to the follow up survey, 50% reported being formally diagnosed with anxiety or depression and 33.3% reported child development problems. Conclusions: Our results highlight the importance of screening for postpartum depression in patients with cardiac disease, especially those requiring antepartum anticoagulation or maternal-infant separation postpartum.

Muscle usage and workload assessment of cardiac ablation procedure with the use of a novel catheter torque tool in a pediatric simulator.

BACKGROUND: Cardiac ablation catheters are small in diameter and pose ergonomic challenges that can affect catheter stability. Significant finger dexterity and strength are necessary to maneuver them safely. We evaluated a novel torque tool to reduce muscle activation when manipulating catheters and improve perceived workload of ablation tasks. The objective was to evaluate measurable success, user perception of workload, and muscle usage when completing a simulated ablation task with and without the use of a catheter torque tool. METHODS: Cardiology attendings and fellows were fitted with surface electromyographic (EMG) sensors on 6 key muscle groups in the left hand and forearm. A standard ablation catheter was inserted into a pediatric cardiac ablation simulator and subjects navigated the catheter tip to 6 specific electrophysiologic targets, including a 1-min simulated radiofrequency ablation lesion. Time to complete the task, number of attempts required to complete the lesion, and EMG activity normalized to percentage of maximum voluntary contraction were collected throughout the task. The task was completed 4 times, twice with and twice without the torque tool, in semi-randomized order. A NASA Task Load Index survey was completed by the participant at the conclusion of each task. RESULTS: Time to complete the task and number of attempts to create a lesion were not altered by the tool. Subjectively, participants reported a significant decrease in physical demand, effort, and frustration, and a significant increase in performance. Muscle activation was decreased in 4 of 6 muscle groups. CONCLUSION: The catheter torque tool may improve the perceived workload of cardiac ablation procedures and reduce muscle fatigue caused by manipulating catheters. This may result in improved catheter stability and increased procedural safety.

Association of Neighborhood Income with Clinical Outcomes Among Pregnant Patients with Cardiac Disease.

Cardiovascular disease is the leading cause of pregnancy mortality. Socioeconomic and racial disparities in pregnancy are well established. Despite this, little is known about the impact of social determinants of health in pregnant patients with heart disease. This study aims to determine whether pregnant patients with heart disease living in lower income neighborhoods and managed at cardio-obstetrics programs have higher rates of cardiac events or preterm deliveries compared with those living in higher income neighborhoods. This is a retrospective cohort study of 206 patients between 2010 and 2020 at a quaternary care hospital in Northern California. The exposure was household income level based on neighborhood defined by the US Census data. Patients in lower income neighborhoods (N = 103) were 45% Hispanic, 34% White, and 14% Asian versus upper income neighborhoods (N = 103), which were 48% White, 31% Asian, and 12% Hispanic (p < 0.001). There was no significant difference in the rates of intrapartum cardiac events (10% vs. 4%; p = 0.16), postpartum cardiac events (14% vs. 17%; p = 0.7), and preterm delivery (24% vs. 17%; p = 0.23). The rates of antepartum hospitalization were higher for lower income neighborhoods (42% vs 22%; p = 0.004). While there is no significant difference in cardiac events and preterm delivery rates between patients from low versus high income neighborhoods, patients from lower income neighborhoods have higher antepartum hospitalization rates. Earlier identification of clinical deterioration provided by a cardio-obstetrics team may contribute to increased hospitalizations, which might mitigate socioeconomic disparities in outcomes for these pregnant patients with heart disease.

Mixed methods evaluation of simulation-based training for postpartum hemorrhage management in Guatemala.

BACKGROUND: To assess if simulation-based training (SBT) of B-Lynch suture and uterine balloon tamponade (UBT) for the management of postpartum hemorrhage (PPH) impacted provider attitudes, practice patterns, and patient management in Guatemala, using a mixed-methods approach. METHODS: We conducted an in-country SBT course on the management of PPH in a governmental teaching hospital in Guatemala City, Guatemala. Participants were OB/GYN providers (n = 39) who had or had not received SBT before. Surveys and qualitative interviews evaluated provider knowledge and experiences with B-Lynch and UBT to treat PPH. RESULTS: Multiple-choice surveys indicated that providers who received SBT were more comfortable performing and teaching B-Lynch compared to those who did not (p = 0.003 and 0.005). Qualitative interviews revealed increased provider comfort with B-Lynch compared to UBT and identified multiple barriers to uterine balloon tamponade implementation. CONCLUSIONS: Simulation-based training had a stronger impact on provider comfort with B-Lynch compared to uterine balloon tamponade. Qualitative interviews provided insight into the challenges that hinder uptake of uterine balloon tamponade, namely resource limitations and decision-making hierarchies. Capturing data through a mixed-methods approach allowed for more comprehensive program evaluation.

Individualized growth assessment in pregnancies complicated by fetal gastroschisis.

OBJECTIVE: Prenatal ultrasound (US) has been shown to overestimate the incidence of suspected fetal growth restriction (FGR) in gastroschisis cases. This is largely because of altered sonographic abdominal circumference (AC) measurements when comparing gastroschisis cases with population nomograms. Individualized Growth Assessment (IGA) evaluates fetal growth using serial US measurements that allow consideration of the growth potential for a given case. Our goal was to assess the utility of IGA for distinguishing normal and pathological fetal growth in gastroschisis cases. STUDY DESIGN: Pregnancies with prenatally diagnosed fetal gastroschisis were managed and delivered at a single academic medical center. US fetal biometry including head circumference (HC), abdominal circumference (AC), and femur diaphysis length (FDL), and neonatal measurements including birthweight and HC were collected and analyzed for 32 consecutive fetal gastroschisis cases with at least two 2nd and two 3rd trimester measurements. Second trimester growth velocities were compared to a group of 118 non-anomalous fetuses with normal neonatal growth outcomes. Gastroschisis cases were classified into groups based on fetal growth pathology score (FGPS9) patterns. Agreement between IGA (FGPS9) and serial conventional estimated fetal weight (EFW) measurements for determining growth pathology was evaluated. Neonatal size outcomes were compared between conventional birthweight classifications for determining small for gestational age (SGA) and IGA Growth Potential Realization Index (GPRI) for weight and head circumference measurements. RESULTS: Fetal growth pathology score (FGPS9) measurements identified three in-utero growth patterns: no growth pathology, growth restriction and recovery, and progressive growth restriction. In the no growth pathology group (n = 19), there was 84% agreement between IGA and conventional methods in determining pathological growth in both the 3rd trimester and at birth. In the growth restriction and recovery group (n = 7), there was 71% agreement both in the 3rd trimester and at birth between IGA and conventional methods. In the progressive growth restriction group (n = 5), there was 100% agreement in the 3rd trimester and 60% agreement at birth between IGA and conventional methods. CONCLUSION: We present the first study using IGA to evaluate normal and pathological fetal growth in prenatally diagnosed gastroschisis cases. IGA was able to delineate two 3rd trimester growth pathology patterns - one with persistent growth restriction and another with in-utero growth recovery. Further validation of these initial findings with larger cohorts is warranted.

Management and outcomes of atrial fibrillation in 241 healthy children and young adults: Revisiting "lone" atrial fibrillation-A multi-institutional PACES collaborative study.

BACKGROUND: Atrial fibrillation (AF) in healthy children and young adults is rare. Risk of recurrence and treatment efficacy are not well defined. OBJECTIVE: The purpose of this study was to assess recurrence patterns and treatment efficacy in AF. METHODS: A retrospective multicenter cohort study including 13 congenital heart centers was facilitated by the Pediatric & Congenital Electrophysiology Society (PACES). Patients ≤21 years of age with documented AF from January 2004 to December 2018 were included. Demographics, family and clinical history, medications, electrophysiological study parameters, and outcomes related to the treatment of AF were recorded and analyzed. Patients with contributory diseases were excluded. RESULTS: In 241 subjects (83% male; mean age at onset 16 years), AF recurred in 94 patients (39%) during 2.1 ± 2.6 years of follow-up. In multivariable analysis, predictors of AF recurrence were family history in a first-degree relative <50 years of age (odds ratio [OR] 1.9; P = .047) and longer PR interval in sinus rhythm (OR 1.1 per 10 ms; P = .037). AF recurrence was similar whether patients began no treatment (39/125 [31%]), began daily antiarrhythmic therapy (24/63 [38%]), or had an ablation at any time (14/53 [26%]; P = .39). Ablating non-AF substrate with supraventricular tachycardia improved freedom from AF recurrence (P = .013). CONCLUSION: Recurrence of AF in the pediatric population is common, and the incidence of recurrence was not impacted by "no treatment," "medication only," or "ablation" treatment strategy. Ablation of pathways and other reentrant targets was the only intervention that decreased AF recurrence in children and young adults.

Novel Approaches to Develop Critical Reference Materials for Noninvasive Prenatal Testing: A Pilot Study.

BACKGROUND: Highly characterized reference materials are required to expand noninvasive prenatal testing (NIPT) for low incidence aneuploidies and microdeletions. The goal of this study was to develop reference materials for the development of next generation circulating cell-free DNA (ccfDNA) assays. METHODS: This was a prospective study of pregnancies complicated by positive prenatal genetic screening. ccfDNA was isolated from maternal plasma and amplified. Lymphoblastoid cell lines were prepared from maternal peripheral blood mononuclear cells and fetal cord blood cells. Cells were Epstein-Barr virus immortalized and expanded. Amplified DNA and to a limited extent formulated lymphoblastoid-derived ccfDNA was tested in SNP-based and chromosome counting (CC) based massively parallel sequencing assays. RESULTS: Enrolled cases included fetuses with: T21 (2), T18 (1), T18-XXX (1), XYY (1), microdeletions (1), and euploid (2). Three lymphoblastoid cells lines were prepared. Genomic DNA was extracted from cell lines and fragmented to simulate ccfDNA. ccfDNA isolation yielded about 2000 usable genome equivalents of DNA for each case for amplification. Although the sonicated genomic DNA derived from lymphoblastoid cell lines did not yield results compatible with NIPT assays, when blinded, NIPT platforms correctly identified the amplified ccfDNA isolated from blood in the majority of cases. CONCLUSIONS: This study showed that maternal blood samples from pregnancies complicated by common chromosomal abnormalities can be used to generate materials for the development and evaluation of NIPT assays.

Triple threat: New presentation with diabetic ketoacidosis, COVID-19, and cardiac arrhythmias.

Patients with diabetes have increased susceptibility to infection with Severe acute respiratory syndrome-coronavirus 2 and increased morbidity and mortality from Coronavirus disease 2019 (COVID-19) infection. Mortality from COVID-19 is sometimes caused by cardiac arrhythmias. Electrolyte disturbances in patients with diabetic ketoacidosis (DKA) can increase the risk of cardiac arrhythmias. Despite these correlations, little has been reported about the co-incidence of these three conditions: COVID-19, DKA and cardiac arrhythmias. In this case report we describe two children with COVID-19, new-onset DKA and cardiac arrhythmias. These cases emphasize the importance of close cardiac and electrolyte monitoring in patients with COVID-19 infection.

Postpartum depression in mothers with pregnancies complicated by fetal cardiac anomaly.

OBJECTIVE: To investigate factors associated with positive postpartum depression (PPD) screen in pregnancies complicated by fetal congenital cardiac anomaly. STUDY DESIGN: We reviewed all records of pregnancies complicated by fetal congenital cardiac anomaly receiving prenatal, intrapartum and postpartum care at our single center, October 2016-October 2019. Maternal, obstetric, and neonatal data were compared between women with and without a positive PPD screen at the 6-week postpartum visit. RESULTS: Out of 415 women referred for fetal congenital cardiac anomaly, 86 women had complete inclusion criteria. Twenty-four women (28%) had a positive PPD screen. The frequencies of planned future infant surgery (73.9 vs. 26.2%, p = 0.01) and neonatal death prior to postpartum visit (12.5 vs. 0%, p = 0.02) were significantly higher among women with a positive PPD screen. CONCLUSION: In pregnancies complicated by fetal congenital cardiac anomaly, mothers of infants with planned future surgery or neonatal death are at significant risk for postpartum depression.

Treadmill exercise testing improves diagnostic accuracy in children with concealed congenital long QT syndrome.

BACKGROUND: Resting electrocardiogram (ECG) identification of long QT syndrome (LQTS) has limitations. Uncertainty exists on how to classify patients with borderline prolonged QT intervals. We tested if exercise testing could help serve to guide which children with borderline prolonged QT intervals may be gene positive for LQTS. METHODS: Pediatric patients (n = 139) were divided into three groups: Controls (n = 76), gene positive LQTS with borderline QTc (n = 21), and gene negative patients with borderline QTc (n = 42). Borderline QTc was defined between 440-470 (male) and 440-480 (female) ms. ECGs were recorded supine, sitting, and standing. Patients then underwent treadmill stress testing with Bruce protocol followed by a 9-minute recovery phase. RESULTS: Supine resting QTc, age, and Schwartz score for the three groups were: (a) gene positive: 446 ± 23 ms, 12.4 ± 3.4 years old, 3.2 ± 1.8; (b) gene negative: 445 ± 20 ms, 12.1 ± 2 years old, 2.0 ± 1.2; and (c) control: 400 ± 24 ms, 15.0 ± 3 years old. The three groups could be differentiated by their QTc response at two time points: standing and recovery phase at 6 minutes. Standing QTc ≥460 ms differentiated borderline prolonged QTc patients (gene positive and gene negative) from controls. Late recovery QTc ≥480 ms distinguished gene positive from gene negative patients. CONCLUSION: Exercise stress testing can be useful to identify children who are gene positive borderline LQTS from a normal population and gene negative borderline QTc children, allowing for selective gene testing in a higher risk group of patients with borderline QTc intervals and intermediate Schwartz scores.

Percutaneous epicardial placement of a prototype miniature pacemaker under direct visualization: An infant porcine chronic survival study.

INTRODUCTION: Pacemaker implantation in infants typically consists of surgical epicardial lead placement with an abdominal generator. Here, we describe the chronic performance of our minimally invasive prototype miniature pacemaker implanted under direct visualization in an immature porcine model. METHODS: Twelve piglets underwent miniature pacemaker implantation. A self-anchoring two-channel access port was inserted into a 1 cm incision in the subxiphoid space, and a thoracoscope was inserted into the main channel to visualize the thoracic cavity under insufflation. The pacemaker leadlet was inserted through a sheath via secondary channel and affixed against the epicardium using a helical side-biting electrode. The miniature pacemaker was tucked into the incision, which was sutured closed. Ventricular sensing, leadlet impedance, and capture thresholds were measured biweekly. A limited necropsy was performed after euthanasia. RESULTS: Nine piglets were followed for a median of 78 (IQR 52-82) days and gained 6.6 ± 3.2 kg. Three animals were censored from the analysis due to complications unrelated to the procedure. Capture thresholds rose above maximal output after a median of 67 (IQR 40-69) days. At termination, there was a significant decrease in R-wave amplitude (P = .03) and rise in capture thresholds at 0.4 ms (P = .01) and 1.0 ms pulse widths (P = .02). There was no significant change in leadlet impedance (P = .74). There were no wound infections. CONCLUSIONS: There were no infections following minimally invasive implantation of our prototype miniature pacemaker. Improvements to epicardial fixation are necessary to address diminished leadlet efficacy over time.

Effects of Dexmedetomidine on Myocardial Repolarization in Children Undergoing General Anesthesia: A Randomized Controlled Trial.

BACKGROUND: Dexmedetomidine is a highly selective α2-adrenergic agonist, which is increasingly used in pediatric anesthesia and intensive care. Potential adverse effects that have not been rigorously evaluated in children include its effects on myocardial repolarization, which is important given that the drug is listed as a possible risk factor for torsades de pointes. We investigated the effect of 3 different doses of dexmedetomidine on myocardial repolarization and transmural dispersion in children undergoing elective surgery with total IV anesthesia. METHODS: Sixty-four American Society of Anesthesiologists I-II children 3-10 years of age were randomized to receive dexmedetomidine 0.25 µg/kg, 0.5 µg/kg, 0.75 µg/kg, or 0 µg/kg (control), as a bolus administered over 60 seconds, after induction of anesthesia. Pre- and postintervention 12-lead electrocardiograms were recorded. The interval between the peak and the end of the electrocardiogram T wave (Tp-e; transmural dispersion) and heart rate-corrected QT intervals (myocardial repolarization) were measured by a pediatric electrophysiologist blinded to group allocation. Data were analyzed using an analysis of covariance regression model. The study was powered to detect a 25-millisecond difference in Tp-e. RESULTS: Forty-eight children completed the study, with data analyzed from 12 participants per group. There were no instances of dysrhythmias. Tp-e values were unaffected by dexmedetomidine administration at any of the studied doses (F = 0.09; P = .96). Mean (99% CI) within-group differences were all <2 milliseconds (-5 to 8). Postintervention, corrected QT interval increased in the control group, but decreased in some dexmedetomidine groups (F = 7.23; P < .001), specifically the dexmedetomidine 0.5 and 0.75 µg/kg doses. Within groups, the mean (99% CI) differences between pre- and postintervention corrected QT interval were 12.4 milliseconds (-5.8 to 30.6) in the control group, -9.0 milliseconds (-24.9 to 6.9) for dexmedetomidine 0.25 µg/kg, -18.6 milliseconds (-33.7 to -3.5) for dexmedetomidine 0.5 µg/kg, and -14.1 milliseconds (-27.4 to -0.8) for dexmedetomidine 0.75 µg/kg. CONCLUSIONS: Of the bolus doses of dexmedetomidine studied, none had an effect on Tp-e and the dexmedetomidine 0.5 and 0.75 µg/kg doses shortened corrected QT intervals when measured at 1 minute after dexmedetomidine bolus injection during total IV anesthesia. There is no evidence for an increased risk of torsades de pointes in this context.

Minimally invasive percutaneous epicardial placement of a prototype miniature pacemaker with a leadlet under direct visualization: A feasibility study in an infant porcine model.

BACKGROUND: Pacemaker implantation in infants is limited to epicardial lead placement and an abdominal generator pocket. We propose a minimally invasive solution using a prototype miniature pacemaker with a steroid-eluting leadlet that can affix against the epicardium under thoracoscopy. OBJECTIVE: The purpose of this study was to evaluate the safety and feasibility of acute implantation of a prototype miniature pacemaker in an infant porcine model. METHODS: A self-anchoring 2-channel access port was inserted into a 1-cm incision left of the subxiphoid space. A rigid thoracoscope with variable viewing angle was inserted through the main channel to visualize the heart under insufflation. An 18-G needle through the second channel accessed the pericardial space, which was secured with a 7-F sheath. The leadlet was affixed against the epicardium using a distal helical side-biting electrode. The sheath, thoracoscope, and port were removed, and the pacemaker was tucked into the incision. Ventricular sensing, lead impedances, and capture thresholds were measured. RESULTS: Twelve piglets (weight 4.8 ± 1.9 kg) had successful device implantation. The median time from incision to leadlet fixation was 21 minutes (interquartile range [IQR] 18-31 minutes). The median lead impedance was 510 Ω (IQR 495-620 Ω). The median R-wave amplitude was 5.7 mV (IQR 4.2-7.0 mV). The median capture threshold was 1.63 V (IQR 1.32-2.97 V) at 0.4 ms pulse width and 1.50 V (IQR 1.16-2.38 V) at 1.0 ms pulse width. There were no complications. CONCLUSION: Minimally invasive epicardial placement of a prototype miniature pacemaker under thoracoscopy was safe and avoided open chest surgery and creation of an abdominal generator pocket.