Small fiber neuropathy in children, adolescents, and young adults with chronic orthostatic intolerance and postural orthostatic tachycardia syndrome: A retrospective study.

PURPOSE: To determine in children, adolescent and young adult (CAYA) patients presenting with Orthostatic Intolerance (OI) or Postural Orthostatic Tachycardia Syndrome (POTS) associated with the additional symptoms of neuropathic discomfort (pain, paresthesia and/or allodynia): 1) the incidence of small fiber neuropathy, and 2) assess if there was serologic evidence for an underlying inflammatory or autoimmune state. METHODS: A cohort of 109 CAYA patients with the above symptoms underwent epidermal skin biopsy for nerve fiber density. Blood biomarkers for inflammation were tested (CRP, ESR, ANA, complement (C3), thyroid function testing with antibodies (thyroid peroxidase antibody and thyroglobulin antibody), and cytokine panel 13). Patients completed a Quality of Health questionnaire. Statistical analysis was performed using Wilcoxon rank sum tests. RESULTS: In CAYA patients with OI or POTS and neuropathic symptoms, skin biopsy for small fiber neuropathy was abnormal in 53 %. The sample population was predominantly female and Caucasian with moderately decreased perceived quality of health. OI /POTS patients with small fiber neuropathy had a 3-fold probability of having a positive ANA or anti-thyroid antibody, suggesting an underlying autoimmune or inflammatory process. CONCLUSION: Our data suggest a link between OI and POTS and small fiber neuropathy. Small fiber neuropathy was found by skin biopsy in over half of the patients tested. OI and Postural orthostatic tachycardia patients with small fiber neuropathy expressed multiple markers suggesting an underlying autoimmune or inflammatory process. Future research will be done to evaluate the symptomatic implication of SFN and whether immune or pharmacologic manipulation can alter patient symptoms.

Predictors of Atrial Arrhythmia in Adults with Repaired Tetralogy of Fallot.

Tetralogy of Fallot (TOF), the most common cyanotic congenital heart disease in adults, has excellent long-term survival. However, many patients (30-45%) develop late arrhythmias. Previous studies have identified predictors of arrhythmia (atrial or ventricular) using clinical markers that predate arrhythmia onset by many years. Our objective was to develop a predictive model for incident atrial arrhythmias within two years of clinical evaluation and diagnostic testing. A single-center nested unmatched case-control study of 174 adults with repaired TOF. We included only patients with results from ECG and echocardiogram data in the required time interval (3-24 months before first arrhythmia for cases; 24 months of follow-up for controls). A predictive multivariable model for risk of incident atrial arrhythmia was developed using logistic regression with a least absolute shrinkage and selection operator (LASSO). Of 41 demographic, surgical, and diagnostic variables, six were selected as having predictive value for atrial arrhythmia based on cross validation. The factors with the greatest predictive value in decreasing order were moderate / severe tricuspid regurgitation (adjusted odds ratio (OR) 149.42), QRS fragmentation (OR 28.08), severe pulmonary regurgitation (OR 8.22), RV systolic dysfunction (OR 2.95), 1st degree AV block (OR 2.59), and age at time of surgical repair (OR 1.02). Predictors for atrial arrhythmia in our study suggested abnormal right ventricle anatomical function and electrophysiologic properties (conduction and repolarization) as the primary underlying substrate.

Cardioneuroablation for pediatric patients with functional sinus node dysfunction and paroxysmal atrioventricular block.

INTRODUCTION: Severe transitory episodes of bradycardia with subsequent syncope in children are common, and generally portend a benign prognosis. Rarely, patients may experience prolonged asystolic episodes secondary to significant sinus pauses (SP) or paroxysmal atrioventricular block (AVB). Cardioneuroablation (CNA) is a catheter-based intervention, used to identify and ablate the epicardial ganglionated plexi (GP), which results in disruption of the vagal-mediated parasympathetic input to the sinus and atrioventricular node. OBJECTIVE: Describe the methodology and role of CNA for treatment of pediatric patients with functional AVB or SP. METHODS: This is a single-center, case series study. Patients with SP or AVB, 21 years of age or younger, who underwent CNA between 2015 and 2021 were included. CNA was performed via anatomically guided and high-frequency stimulation methods. RESULTS: Six patients were included. The median age was 18.9 years (range 12.3-20.9 years), 33% female. Two patients had prolonged SP, two had paroxysmal AVB, and two had both SP and AVB. Four patients had prior syncope. The median longest pause was 8.9 s (range 3.9-16.8) with 11 total documented pauses (range 2-231) during the 6 months pre-CNA. Post-CNA, the median longest pause was 1.3 s (range 0.8-2.2) with one documented SP after termination of atrial tachycardia at the 3-month follow-up. At 6 months, the median longest pause was 1.1 s (0.8-1.3) with 0 documented pauses. No patients had syncope post-CNA. CONCLUSION: CNA may be an effective alternative to pacemaker implantation in pediatric patients with syncope or significant symptoms secondary to functional SP or AVB.

Cardiac arrhythmias in postural tachycardia syndrome and orthostatic intolerance.

BACKGROUND AND OBJECTIVES: There is sparse literature on cardiac arrhythmias and the utility of ambulatory rhythm monitoring in patients with postural tachycardia syndrome and orthostatic intolerance. This study's primary aim was to investigate the prevalence of arrhythmias in this population. Knowing the prevalence and types of arrhythmias in dysautonomia patients could influence the decision to pursue ambulatory rhythm monitoring and ultimately guide therapy. METHODS: This retrospective descriptive study examined the frequency of cardiac arrhythmias, as detected by ambulatory rhythm monitoring, in children with postural tachycardia syndrome/orthostatic intolerance or syncope who were seen at the Children's National Hospital Electrophysiology Clinic between January 2001 and December 2020. RESULTS: In postural tachycardia syndrome/orthostatic intolerance patients, arrhythmia was detected on 15% of 332 ambulatory rhythm monitors. In syncope patients, arrhythmia was detected on 16% of 157 ambulatory rhythm monitors, not significantly different from the postural tachycardia syndrome/orthostatic intolerance group. The difference in rate of arrhythmia detection between 24-hour Holter and 2-week Zio® monitoring was not statistically significant. CONCLUSION: This study suggests that a substantial proportion of postural tachycardia syndrome/orthostatic intolerance patients may have concomitant underlying cardiac arrhythmias, at a frequency similar to what is seen in patients undergoing primary evaluation for cardiac symptoms such as chest pain, palpitations, and syncope. In the appropriate clinical context, physicians caring for postural tachycardia syndrome/orthostatic intolerance patients should consider additional evaluation for arrhythmias beyond sinus tachycardia.

Pediatric Postural Orthostatic Tachycardia Syndrome: Where We Stand.

Postural orthostatic tachycardia syndrome (POTS), first described in 1992, remains an enigmatic, yet severely and variably debilitating, disorder. The pathophysiology of this syndrome is still not understood, and there remains no biomarker indicating the presence of POTS. Although research interest has increased in recent years, there are relatively fewer clinical and research studies addressing POTS in children and adolescents compared with adults. Yet, adolescence is when a large number of cases of POTS begin, even among adult patients who are subsequently studied. This article summarizes reported research in POTS, specifically in pediatric patients, including discussion of aspects of diagnostic criteria, risk factors and outcomes, neurohormonal and hemodynamic abnormalities, clinical assessment, and treatment. The goals of this review are increased recognition and acknowledgment of POTS among pediatric and adolescent providers, as well as to provide an understanding of reported abnormalities of homeostasis, such that symptomatic patients will be able to be recognized and appropriately managed, enabling them to return to their activities of daily living.

IV Sotalol Use in Pediatric and Congenital Heart Patients: A Multicenter Registry Study.

Background There is limited information regarding the clinical use and effectiveness of IV sotalol in pediatric patients and patients with congenital heart disease, including those with severe myocardial dysfunction. A multicenter registry study was designed to evaluate the safety, efficacy, and dosing of IV sotalol. Methods and Results A total of 85 patients (age 1 day-36 years) received IV sotalol, of whom 45 (53%) had additional congenital cardiac diagnoses and 4 (5%) were greater than 18 years of age. In 79 patients (93%), IV sotalol was used to treat supraventricular tachycardia and 4 (5%) received it to treat ventricular arrhythmias. Severely decreased cardiac function by echocardiography was seen before IV sotalol in 7 (9%). The average dose was 1 mg/kg (range 0.5-1.8 mg/kg/dose) over a median of 60 minutes (range 30-300 minutes). Successful arrhythmia termination occurred in 31 patients (49%, 95% CI [37%-62%]) with improvement in rhythm control defined as rate reduction permitting overdrive pacing in an additional 18 patients (30%, 95% CI [19%-41%]). Eleven patients (16%) had significant QTc prolongation to >465 milliseconds after the infusion, with 3 (4%) to >500 milliseconds. There were 2 patients (2%) for whom the infusion was terminated early. Conclusions IV sotalol was safe and effective for termination or improvement of tachyarrhythmias in 79% of pediatric patients and patients with congenital heart disease, including those with severely depressed cardiac function. The most common dose, for both acute and maintenance dosing, was 1 mg/kg over ~60 minutes with rare serious complications.

Postural orthostatic tachycardia syndrome (POTS): Priorities for POTS care and research from a 2019 National Institutes of Health Expert Consensus Meeting - Part 2.

The National Institutes of Health hosted a workshop in 2019 to build consensus around the current state of understanding of the pathophysiology of postural orthostatic tachycardia syndrome (POTS) and to identify knowledge gaps that must be addressed to enhance clinical care of POTS patients through research. This second (of two) articles summarizes current knowledge gaps, and outlines the clinical and research priorities for POTS. POTS is a complex, multi-system, chronic disorder of the autonomic nervous system characterized by orthostatic intolerance and orthostatic tachycardia without hypotension. Patients often experience a host of other related disabling symptoms. The functional and economic impacts of this disorder are significant. The pathophysiology remains incompletely understood. Beyond the significant gaps in understanding the disorder itself, there is a paucity of evidence to guide treatment which can contribute to suboptimal care for this patient population. The vast majority of physicians have minimal to no familiarity or training in the assessment and management of POTS. Funding for POTS research remains very low relative to the size of the patient population and impact of the syndrome. In addition to efforts to improve awareness and physician education, an investment in research infrastructure including the development of standardized disease-specific evaluation tools and outcome measures is needed to facilitate effective collaborative research. A national POTS research consortium could facilitate well-controlled multidisciplinary clinical research studies and therapeutic trials. These priorities will require a substantial increase in the number of research investigators and the amount of research funding in this area.

Postural orthostatic tachycardia syndrome (POTS): State of the science and clinical care from a 2019 National Institutes of Health Expert Consensus Meeting - Part 1.

Postural orthostatic tachycardia syndrome (POTS) is a chronic and often disabling disorder characterized by orthostatic intolerance with excessive heart rate increase without hypotension during upright posture. Patients often experience a constellation of other typical symptoms including fatigue, exercise intolerance and gastrointestinal distress. A typical patient with POTS is a female of child-bearing age, who often first displays symptoms in adolescence. The onset of POTS may be precipitated by immunological stressors such as a viral infection. A variety of pathophysiologies are involved in the abnormal postural tachycardia response; however, the pathophysiology of the syndrome is incompletely understood and undoubtedly multifaceted. Clinicians and researchers focused on POTS convened at the National Institutes of Health in July 2019 to discuss the current state of understanding of the pathophysiology of POTS and to identify priorities for POTS research. This article, the first of two articles summarizing the information discussed at this meeting, summarizes the current understanding of this disorder and best practices for clinical care. The evaluation of a patient with suspected POTS should seek to establish the diagnosis, identify co-morbid conditions, and exclude conditions that could cause or mimic the syndrome. Once diagnosed, management typically begins with patient education and non-pharmacologic treatment options. Various medications are often used to address specific symptoms, but there are currently no FDA-approved medications for the treatment of POTS, and evidence for many of the medications used to treat POTS is not robust.

Median Arcuate Ligament Syndrome with Orthostatic Intolerance: Intermediate-Term Outcomes following Surgical Intervention.

OBJECTIVES: To report the intermediate-term outcome following surgical intervention for median arcuate ligament syndrome (MALS) in adolescents and young adults with orthostatic intolerance (OI) to assess clinical improvement in the gastrointestinal and 5 other functional domains and if relief of arterial obstruction is associated with resolution of clinical symptoms. STUDY DESIGN: Thirty-one patients were given 2 dysautonomia-designed questionnaires to assess changes in symptoms following operative intervention in 6 functional domains and underwent postoperative repeat abdominal ultrasound examinations. RESULTS: Average follow-up after surgery was 22.4 ± 14.8 months. Self-assessed quality of health on a Likert scale (1-10 with 10 being normal) improved from 4.5 ± 2.1 preoperatively to 5.3 ± 2.4 postoperatively (P = not significant). Gastrointestinal symptoms of abdominal pain, nausea, and vomiting improved in 63% (P = .007), 53% (P = .040), and 62% (P = .014) of patients, respectively. Cardiovascular symptoms of dizziness, syncope, chest pain, and palpitations improved in 45% (P = not significant), 50% (P = not significant), 54% (P = .043), and 54% (P = .037) of patients, respectively. Transabdominal ultrasound peak supine expiratory velocity decreased from 348 ± 105 cm/s preoperatively to 251 ± 109 cm/s at 6 months or more after a ligament release procedure. Decrease of the postoperative celiac artery Doppler velocity was not associated with an improvement in gastrointestinal symptoms (P = .075). CONCLUSIONS: Adolescent and young adult patients with median arcuate ligament syndrome and OI have a good response to surgical intervention. About two-thirds of patients report significant improvement in symptoms of abdominal pain, nausea, and vomiting. Despite these encouraging data, many patients with MALS and OI continue to have an impaired quality of health.

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.

Can the 12-lead ECG distinguish RVOT from aortic cusp PVCs in pediatric patients?

BACKGROUND: The ability to differentiate right ventricular outflow tract (RVOT) from coronary cusp (CC) site of origin (SOO) by 12-lead ECG in pediatric patients may impact efficacy and procedural time. The objective of this study was to predict RVOT versus CC SOO by ECG in pediatric patients. METHODS: Pediatric patients (<21 years) without structural heart disease with RVOT or CC premature ventricular contraction (PVC) ablations performed (2014-2018) were evaluated through multi-institution retrospective review. Demographics, ECG PVC parameters, ablation site, recurrence, and repeat procedures were collected. RESULTS: Thirty-seven patients were evaluated (mean age 14.6 years, weight 60.6 kg): 11 CC and 26 RVOT PVC SOO. CC PVCs were less likely to exhibit left bundle branch block (64% vs 100%, P = .005), had larger R-wave amplitude in V1 (0.27 vs 0.11 mV, P = .03), larger R/S ratio in V1 (0.37 vs 0.09, P = .003), and had precordial transition in V3 or earlier (73% vs 15%, P = .002). A composite score was created with the following variables: isodiphasic or positive QRS in V1, R/S ratio in V1 > 0.05, S wave in V1 < 0.9 mV, and precordial transition at or before V3. Composite score ≥ 2 was associated with a CC SOO (OR 42.0, P = .001, and AUC 0.86). CONCLUSIONS: 12-lead ECG of PVCs from the CC was associated with larger V1 R-wave amplitude, larger R/S ratio in V1, and precordial transition at or before V3. A composite score may help predict PVC/VT arising from the CC.

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.

Feasibility of Non-invasive Fetal Electrocardiographic Interval Measurement in the Outpatient Clinical Setting.

Non-invasive fetal electrocardiography (ECG) is a promising method for evaluating fetal cardiac electrical activity. Despite advances in fetal ECG technology, its ability to provide reliable, interpretable results in a typical outpatient fetal cardiology setting remains unclear. We sought to determine the feasibility of measuring standard ECG intervals in an outpatient fetal cardiology practice using an abdominal fetal ECG device that employs blind source separation with reference, an innovative signal-processing technique for fetal ECG extraction. Women scheduled for clinically indicated outpatient fetal echocardiogram underwent 10 min of fetal ECG acquisition from the maternal abdomen using specialized gel electrodes. A bedside laptop computer performed fetal ECG extraction, allowing real-time visualization of fetal and maternal ECG signals. Offline post-processing of 1 min of recorded data yielded fetal P-wave duration, PR interval, QRS duration, RR interval, QT interval, and QTc. Fifty-five fetuses were studied with gestational age 18-37 weeks, including 13 with abnormal fetal echocardiogram findings and three sets of twins. Interpretable results were obtained in 91% of fetuses, including 85% during the vernix period and 100% of twin fetuses. PR interval and RR interval of 18-24 week gestation fetuses were significantly shorter than those with gestational age 25-31 and 32-37 weeks. Of the six fetuses with abnormal rhythms on fetal echocardiogram, fetal ECG tracing was interpretable in five and matched the rhythm noted on fetal echocardiogram. Abdominal fetal ECG acquisition is feasible for arrhythmia detection and ECG interval calculation in a routine clinical setting.

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.

Comparison of the Medtronic SelectSecure and conventional pacing leads: Long-term follow-up in a multicenter pediatric and congenital cohort.

INTRODUCTION: The Medtronic SelectSecure™ (Minneapolis, MN, USA) pacing lead (SS) has theoretical advantages compared to conventional (C) transvenous pacing leads (PLs). The study purpose was to determine whether differences in electrical function and lead survival exist between these PLs in a large data set of pediatric and congenital patients. METHODS: A multicenter historical longitudinal cohort study was performed comparing SS and CPL performance over a 72-month follow-up (FU). Ten centers provided data for both SS and CPL, matched for age, implanted pacing chamber, time period of implantation, and presence of heart disease. RESULTS: The cohort consisted of 141 subjects in each group. No statistical differences were observed in age, gender, presence of heart disease, or pacing indication. Atrial and ventricular capture thresholds were stable throughout FU and higher in the SS group (atrial: 0.75 ± 0.02 vs 0.5 ± 0.04 V, ventricular: 1.0 ± 0.04 vs 0.75 ± 0.04 V), P < 0.001. Group PL sensing thresholds did not differ. The SS group required greater energy to pace (atrial: 0.57 ± 0.05 vs 0.32 ± 0.02 mJ, ventricular: 0.83 ± 0.05 vs 0.56 ± 0.06 mJ), P = 0.001. Early lead dislodgement and phrenic nerve stimulation were greater in the SS group (P = 0.03). Long-term lead survival was high and similar between the two groups, P = 0.35. CONCLUSIONS: Long-term survival of both PL was high with a low fracture rate. The SS had excellent electrical function but did show higher capture thresholds and increased energy to pace; these differences are offset by other advantages of the SS PL.

Utility of Diagnostic Studies for Upper Gastrointestinal Symptoms in Children with Orthostatic Intolerance.

OBJECTIVE: To assess the utility of gastrointestinal (GI) diagnostic studies in the evaluation of patients with orthostatic intolerance. STUDY DESIGN: Medical records of 103 consecutive children/young adults with orthostatic intolerance and gastrointestinal symptoms were reviewed. All patients had undergone antroduodenal manometry in conjunction with the tilt table test, autonomic testing, and upper gastrointestinal endoscopy (EGD). A gastric emptying study (GES) was performed in 81 patients. RESULTS: The median age of the cohort was 17 years (IQR, 15-19) with a female predominance (females:males, 3:1). As expected, the tilt table test was abnormal in all patients. Antroduodenal manometry was abnormal in 83 of 103 patients (81%), showing neurogenic intestinal dysmotility in 50%, rumination in 20%, and visceral hyperalgesia in 10%. The GES results were abnormal in 23 of 81 patients (28.4%), mostly (21 of 23) with delayed GES. None of the tilt table test or autonomic results were predictive of abnormal antroduodenal manometry or GES. Analysis of EGD biopsy samples revealed nonspecific esophagitis and/or gastritis in 16 of 103 patients (15%). CONCLUSIONS: Antroduodenal manometry with the tilt table test were the most insightful investigations in adolescents and young adults with orthostatic intolerance and gastrointestinal symptoms. GES and EGD provided limited information. Gastrointestinal symptoms were related more to functional rather than mucosal or organic etiologies, suggesting a limited role of endoscopy alone in evaluating patients with orthostatic intolerance presenting with gastrointestinal symptoms.

Lower risk of postoperative arrhythmias in congenital heart surgery following intraoperative administration of magnesium.

OBJECTIVES: Postoperative arrhythmias are common in children undergoing congenital heart surgery. We evaluated whether intraoperative administration of magnesium was associated with a reduced occurrence of specific postoperative arrhythmias, as has been described previously, or had a broader effect on multiple arrhythmia types, and whether there existed a dose-effect of intraoperative magnesium. METHODS: We used a historical prospective observational cohort study. Propensity score matching using logistic regression was applied to establish similar populations of treatment groups balanced on 5 important covariates. RESULTS: Based on propensity score-matched groups, magnesium 50 mg/kg administration was associated with a reduced odds of occurrence of postoperative arrhythmias: any arrhythmia (odds ratio [OR] = 0.50, P < .001), junctional ectopic tachycardia (OR = 0.56, P = .004), accelerated junctional rhythm (OR = 0.56, P = .089), atrial tachycardia (OR = 0.48, P = .005), ventricular tachycardia (OR = 0.52, P = .04), and atrioventricular block (OR = 0.47, P = .03). The effect of magnesium on reducing the odds of occurrence of postoperative arrhythmias did not differ between 25 mg/kg versus 50 mg/kg. CONCLUSIONS: As many as one third of our patients undergoing congenital heart surgery had postoperative arrhythmias. Use of intraoperative magnesium was associated with a reduction in the odds of occurrence of all postoperative arrhythmias. Our results do not provide evidence that a greater dose of magnesium is associated with greater arrhythmia risk reduction. Despite the intraoperative use of magnesium, there continued to be a high residual incidence of postoperative arrhythmias, raising the question for studying new or additional agents.