Wackel, Philip

ABSTRACT Background Coronary artery (CA) injury from catheter ablation is an uncommon complication, but the risk is under‐recognized. The risk for CA injury significantly increases when a CA is within 3 mm of the site of ablation, but CA imaging to assess for CA proximity to ablation sites is not commonly performed in children prior to ablation. Objective The aim of the study was to assess CA proximity to potential ablation sites. Methods A retrospective review of all coronary computed tomography angiograms (CTAs) in pediatric patients <18 years of age at Mayo Clinic from 2017 through 2023 was conducted. The proximity of CAs to potential ablation sites in the coronary sinus and the appendage bases were measured. Results Seventy‐two CTAs in 67 patients >15 kg and <18 years old were included. Median age was 12 years, and median weight was 41 kg. In right dominant CA circulation, 23/36 (64%) had a CA within 3 mm of the coronary sinus. In left and co‐dominant CA circulation, 26/26 (100%) had a CA within 3 mm of the coronary sinus. The right CA was within 3 mm of the appendage base in 49/69 (71%). The circumflex CA was within 3 mm of the appendage base in 50/68 (74%). Conclusion Most pediatric patients have a CA ≤ 3 mm from potential ablation sites in the coronary sinus and base of the appendages. Precautions should be taken to avoid CA damage before performing catheter ablation in these areas.

AbstractIntroductionAlthough prior studies indicate that a QTc > 500 ms on a single baseline 12‐lead electrocardiogram (ECG) is associated with significantly increased risk of arrhythmic events in long QT syndrome (LQTS), less is known about the risk of persistent QT prolongation. We sought to determine QTc persistence and its prognostic effect on breakthrough cardiac events (BCEs) among pediatric patients treated for LQTS.MethodsWe performed a retrospective analysis of 433 patients with LQTS evaluated, risk‐stratified, and undergoing active guideline‐based LQTS treatment between 1999 and 2019. BCEs were defined as arrhythmogenic syncope/seizure, sudden cardiac arrest (SCA), appropriate VF‐terminating ICD shock, and sudden cardiac death (SCD).ResultsDuring the median follow‐up of 5.5 years (interquartile range [IQR] = 3–9), 32 (7%) patients experienced a total of 129 BCEs. A maximum QTc threshold of 520 ms and median QTc threshold of 490 ms were determined to be strong predictors for BCEs. A landmark analysis controlling for age, sex, genotype, and symptomatic status demonstrated models utilizing both the median QTc and maximum QTc demonstrated the highest discriminatory value (c‐statistic = 0.93–0.95). Patients in the high‐risk group (median QTc > 490 ms and maximum QTc > 520 ms) had a significantly lower BCE free survival (70%–81%) when compared to patients in both medium‐risk (93%–97%) and low‐risk (98%–99%) groups.ConclusionsThe risk of BCE among patients treated for LQTS increases not only based upon their maximum QTc, but also their median QTc (persistence of QTc prolongation). Patients with a maximum QTc > 520 ms and median QTc > 490 ms over serial 12‐lead ECGs are at the highest risk of BCE while on guideline‐directed medical therapy.

AbstractBackgroundRoutine defibrillation threshold testing (DFT) of transvenous implantable defibrillators (ICDs) has largely been in decline. In patients with non‐transvenous ICDs that utilize subcutaneous and pleural ICD leads, serial DFT testing can detect a significant number of failures. Data about the utility of follow‐up defibrillation safety margin testing (DSM) testing in pediatric patients and young adults with an epicardial ICD are lacking.MethodsPatients aged < 25 years old who underwent epicardial ICD placement at Mayo Clinic from 2014 to 2023 with at least one follow‐up DSM test were included. The patients were divided into a “routine” (R) and “clinically indicated” (CI) group based on the index of clinical concern. Inadequate DSM was defined as unsuccessful defibrillation at an output of less than 10 J below the maximum output of the device. The purpose of this study was to assess the utility of follow‐up DSM testing.ResultsAn epicardial ICD system was placed in 122 patients. A total of 26 patients met inclusion criteria and underwent a total of 47 DSM follow up tests. Inadequate DSM occurred in 1/33 (3%) in the R group and 2/14 (14%) DSM tests in the CI group. The median follow‐up period was 54 and 36 months for the R and CI group, respectively.ConclusionsOur data suggest that epicardial ICDs are reliable and routine follow‐up DSM testing may not be necessary for all patients. DSM testing should be performed in individuals with epicardial ICD systems when there is clinical concern about lead or coil performance.