Publications by authors named "Mark E Alexander"

Article Synopsis
  • Postoperative arrhythmias are typically temporary and treated with medication, but some patients need further procedures like electrophysiology study (EPS) and ablation.
  • This study reviewed cases from 2000-2021 to assess the effectiveness and safety of early EPS and ablation in congenital heart surgery patients, focusing on outcomes, complications, and long-term arrhythmia recurrence.
  • Of the nearly 29,000 surgeries, only 50 patients (some within 3 months and others from 3-12 months post-surgery) required EPS, showing an 82% success rate, though 54% experienced recurring arrhythmias, albeit with less severity.
View Article and Find Full Text PDF
Article Synopsis
  • The study compares the effectiveness of omnipolar and bipolar mapping techniques in identifying the dual AVN substrate in patients with atrioventricular nodal reentrant tachycardia (AVNRT) versus those without it.
  • A retrospective analysis involved 13 AVNRT patients and 9 controls, revealing that the omnipolar activation vector pivot showed high predictive accuracy for AVNRT identification.
  • Additionally, while omnipolar mapping offers qualitative insights, bipolar voltage measurements effectively describe SP anisotropy, with peak frequency analysis enhancing the understanding of successful slow pathway modification sites.
View Article and Find Full Text PDF

Pediatric ECG standards have been defined without echocardiographic confirmation of normal anatomy. The Pediatric Heart Network Normal Echocardiogram Z-score Project provides a racially diverse group of healthy children with normal echocardiograms. We hypothesized that ECG and echocardiographic measures of left ventricular (LV) dimensions are sufficiently correlated in healthy children to imply a clinically meaningful relationship.

View Article and Find Full Text PDF

Background: Artificial intelligence-enhanced ECG analysis shows promise to detect ventricular dysfunction and remodeling in adult populations. However, its application to pediatric populations remains underexplored.

Methods: A convolutional neural network was trained on paired ECG-echocardiograms (≤2 days apart) from patients ≤18 years of age without major congenital heart disease to detect human expert-classified greater than mild left ventricular (LV) dysfunction, hypertrophy, and dilation (individually and as a composite outcome).

View Article and Find Full Text PDF

Aims: Coarctation of the aorta is associated with long-term morbidity including decreased exercise capacity, despite successful repair. In the absence of discrete recoarctation, the haemodynamic mechanism remains unknown. This multicentre study evaluated the relationship between aorta shape, flow, and exercise capacity in patients after arch repair, specifically through the lens of aortic size mismatch and descending aortic (DAo) flow and their association with exercise.

View Article and Find Full Text PDF

Introduction: The use of flecainide and propafenone for medical cardioversion of atrial fibrillation (AF) and atrial flutter/intra-atrial reentrant tachycardia (IART) is well-described in adults without congenital heart disease (CHD). Data are sparse regarding their use for the same purpose in adults with CHD and in adolescent patients with anatomically normal hearts and we sought to describe the use of class IC drugs in this population and identify factors associated with decreased likelihood of success.

Methods: Single center retrospective cohort study of patients who received oral flecainide or propafenone for medical cardioversion of AF or IART from 2000 to 2022.

View Article and Find Full Text PDF

Objective: To determine if socioeconomic status (SES) has a greater effect than standard demographic values on predicted peak oxygen consumption (pVO).

Study Design: We conducted a single-institution, retrospective analysis of maximal cardiopulmonary exercise test (CPET) data from 2010 to 2020 for healthy patients age <19 years with body mass index (BMI) percentile (BMI%) between 5-95. Data were sorted by self-identified race, BMI%, and adjusted gross income (AGI); AGI served as a surrogate for SES.

View Article and Find Full Text PDF

Introduction: Accessory atrioventricular pathways (APs) may mediate atrioventricular reciprocating tachycardia and, in some cases, have the potential to conduct atrial tachycardia rapidly, which can be life threatening. While catheter ablation can be curative, ablation of right free wall APs is associated with a high rate of recurrence, likely secondary to reduced catheter stability along the right free wall atrioventricular groove. We sought to identify characteristics associated with a lower rate of recurrence and hypothesized ablation lesions placed on the ventricular side of the atrioventricular groove using a retroflexed catheter approach would decrease rates of recurrence.

View Article and Find Full Text PDF

Background: Ventricular fibromas frequently present with life-threatening ventricular tachycardia (VT) or ventricular fibrillation (VF) in children. The long-term risk of sustained ventricular arrhythmias after surgical resection is unknown.

Objectives: The aims of this study were to quantify the VT/VF risk after surgical resection and to examine the results of early (during index surgical hospitalization) and late (≥3 months after surgery) postoperative ventricular stimulation (V-stim) studies.

View Article and Find Full Text PDF

Risk stratification is required to set an exercise prescription for cardiac rehabilitation, but an optimal scheme for congenital heart disease (CHD) is unknown. We piloted a system based on hemodynamic rather than anatomic factors: function, oxygen level, rhythm, complex/coronary anatomy, and elevated load (FORCE). Feasibility, efficacy, and safety of the FORCE tool were evaluated.

View Article and Find Full Text PDF

Background Catheter-based slow-pathway modification (SPM) is the treatment of choice for symptomatic atrioventricular nodal reentrant tachycardia (AVNRT). We sought to investigate the interactions between patient age and procedural outcomes in pediatric patients undergoing catheter-based SPM for AVNRT. Methods and Results A retrospective cohort study was performed, including consecutive patients undergoing acutely successful SPM for AVNRT from 2008 to 2017.

View Article and Find Full Text PDF

Background: Catheter radiofrequency (RF) ablation for cardiac arrhythmias is a painful procedure. Prior work using functional near-infrared spectroscopy (fNIRS) in patients under general anesthesia has indicated that ablation results in activity in pain-related cortical regions, presumably due to inadequate blockade of afferent nociceptors originating within the cardiac system. Having an objective brain-based measure for nociception and analgesia may in the future allow for enhanced analgesic control during surgical procedures.

View Article and Find Full Text PDF

Objectives: To characterize the prevalence, associations, management, and outcomes of supraventricular tachycardia (SVT) in neonates with congenital diaphragmatic hernia (CDH).

Design: Retrospective chart and cardiology code review within a cohort of patients with CDH was used to define a subpopulation with atrial arrhythmia. SVT mechanisms were confirmed by electrocardiogram analysis.

View Article and Find Full Text PDF

Exercise function is well characterized in adults with hypertrophic cardiomyopathy (HCM); however, there is a paucity of data in children and young adults with HCM. Here we sought to characterize exercise function in young people with HCM, understand limitations in exercise function by correlating exercise function parameters with echocardiogram parameters and identify prognostic value of exercise parameters. We performed a retrospective, single-center cohort study characterizing exercise function in patients < 26 years old with HCM undergoing cardiopulmonary exercise testing (CPET).

View Article and Find Full Text PDF

Decreased physical activity is associated with cardiovascular, metabolic and mental health disease. While decreases in physical activity during the COVID-19 pandemic have been described in the general population, there is a paucity of data regarding children with underlying cardiovascular disease. We hypothesized there would be a decrease in physical activity at the onset of the COVID-19 pandemic.

View Article and Find Full Text PDF

Background: Altered ventricular depolarization due to manifest accessory pathway conduction (ie, Wolff-Parkinson-White syndrome) leads to repolarization abnormalities that persist after pathway ablation. The term T-wave memory (TWM) has been applied to these changes, as the postablation T-wave vector "remembers" the pre-excited QRS vector. In adults, these abnormalities can be misinterpreted as ischemia leading to unnecessary interventions.

View Article and Find Full Text PDF

Introduction: Reflex-mediated syncope occurs in 15% of children and young adults. In rare instances, pacemakers are required to treat syncopal episodes associated with transient sinus pauses or atrioventricular block. This study describes a single centre experience in the use of permanent pacemakers to treat syncope in children and young adults.

View Article and Find Full Text PDF

Background: Adult survivors of Hodgkin lymphoma (HL) are at increased risk of cardiovascular (CV) events secondary to mediastinal radiation therapy (RT).

Objectives: In this group of patients, we assessed the association between cardiopulmonary exercise testing (CPET), as determined by percent-predicted peak Vo (ppVopeak), and clinical outcomes, as well as the rate of ppVopeak decline and sex differences.

Methods: All survivors of HL who were >10 years post chest RT and who underwent ≥1 CPET were enrolled from a single center.

View Article and Find Full Text PDF

Objective: To examine the association between electrocardiographic (ECG) evidence of carditis at the time of Lyme disease evaluation and a diagnosis of Lyme disease.

Study Design: We performed an 8-center prospective cohort study of children undergoing emergency department evaluation for Lyme disease limited to those who had an ECG obtained by their treating clinicians. The study cardiologist reviewed all ECGs flagged as abnormal by the study sites to assess for ECG evidence of carditis.

View Article and Find Full Text PDF

Background: Catheter ablation of accessory pathways (APs) in Ebstein anomaly (EA) has been associated with a high recurrence risk.

Objective: The purpose of this study was to compare outcomes of AP ablation in EA in an early (1990-2004) vs a recent (2005-2019) era and identify variables associated with recurrence.

Methods: A retrospective review of all catheter ablations for supraventricular tachycardia in EA at our institution was performed.

View Article and Find Full Text PDF

Prior studies have characterized children with supraventricular tachycardia (SVT) in inpatient settings, however there is a paucity of data regarding pediatric SVT in the Emergency Department (ED) setting. We sought to describe pediatric ED visits for SVT and assess whether variability exists in care. We performed a cross-sectional study of ED visits for SVT among children < 18 years old from 2010 to 2017 at 33 pediatric hospitals.

View Article and Find Full Text PDF

Unlabelled: Variability exists in the management of childhood syncope as clinicians balance resource utilization with the need to identify serious diseases. Limited evidence exists regarding the long-term impact of evidence-based guidelines (EBGs) on clinical practices. This study's objective was to measure long-term changes in the management of syncope after implementing a syncope EBG in a single pediatric emergency department following the redistribution of resources to facilitate compliance over time.

View Article and Find Full Text PDF