Relationship of ventricular assist device support duration with pediatric heart transplant outcomes.

BACKGROUND: There is wide variability in the timing of heart transplant (HTx) after pediatric VAD implant. While some centers wait months before listing for HTx, others accept donor heart offers within days of VAD surgery. We sought to determine if HTx within 30 days versus ≥ 30 after VAD impacts post-HTx outcomes. METHODS: Children on VAD pre-HTx were extracted from the Pediatric Heart Transplant Study database. The primary endpoints were post-HTx length of hospital stay (LOS) and one-year survival. Confounding was addressed by propensity score weighting using inverse probability of treatment. Propensity scores were calculated based on age, blood type, primary cardiac diagnosis, decade, VAD type, and allosensitization status. RESULTS: A total of 1064 children underwent VAD prior to HTx between 2000 to 2018. Most underwent HTx ≥ 30 days post-VAD (70%). Infants made up 22% of both groups. Patients ≥ 12 years old were 42% of the < 30 days group and children 1 to 11 years comprised 47% of the ≥ 30 days group (p < 0.001). There was no difference in the prevalence of congenital heart disease vs. cardiomyopathy (p = 0.8) or high allosensitization status (p = 0.9) between groups. Post-HTx LOS was similar between groups (p = 0.11). One-year survival was lower in the < 30 days group (adjusted mortality HR 1.76, 95% CI 1.11-2.78, p = 0.016). CONCLUSIONS: A longer duration of VAD support prior to HTx is associated with a one-year survival benefit in children, although questions of patient complexity, post-VAD complications and the impact on causality remain. Additional studies using linked databases to understand these factors will be needed to fully assess the optimal timing for post-VAD HTx.

ATP1A3-Encoded Sodium-Potassium ATPase Subunit Alpha 3 D801N Variant Is Associated With Shortened QT Interval and Predisposition to Ventricular Fibrillation Preceded by Bradycardia.

Background Pathogenic variation in the ATP1A3-encoded sodium-potassium ATPase, ATP1A3, is responsible for alternating hemiplegia of childhood (AHC). Although these patients experience a high rate of sudden unexpected death in epilepsy, the pathophysiologic basis for this risk remains unknown. The objective was to determine the role of ATP1A3 genetic variants on cardiac outcomes as determined by QT and corrected QT (QTc) measurements. Methods and Results We analyzed 12-lead ECG recordings from 62 patients (male subjects=31, female subjects=31) referred for AHC evaluation. Patients were grouped according to AHC presentation (typical versus atypical), ATP1A3 variant status (positive versus negative), and ATP1A3 variant (D801N versus other variants). Manual remeasurements of QT intervals and QTc calculations were performed by 2 pediatric electrophysiologists. QTc measurements were significantly shorter in patients with positive ATP1A3 variant status (P<0.001) than in patients with genotype-negative status, and significantly shorter in patients with the ATP1A3-D801N variant than patients with other variants (P<0.001). The mean QTc for ATP1A3-D801N was 344.9 milliseconds, which varied little with age, and remained <370 milliseconds throughout adulthood. ATP1A3 genotype status was significantly associated with shortened QTc by multivariant regression analysis. Two patients with the ATP1A3-D801N variant experienced ventricular fibrillation, resulting in death in 1 patient. Rare variants in ATP1A3 were identified in a large cohort of genotype-negative patients referred for arrhythmia and sudden unexplained death. Conclusions Patients with AHC who carry the ATP1A3-D801N variant have significantly shorter QTc intervals and an increased likelihood of experiencing bradycardia associated with life-threatening arrhythmias. ATP1A3 variants may represent an independent cause of sudden unexplained death. Patients with AHC should be evaluated to identify risk of sudden death.

Variability in radiation dose and image quality: A comparison across fluoroscopy-system vendors, generations of equipment and institutions.

OBJECTIVES: To evaluate differences in radiation dose and image quality across institutions, fluoroscope vendors and generations of fluoroscopes for pediatric cardiac catheterization. BACKGROUND: Increased recognition of the potentially harmful effects of ionizing radiation has spurred technological advances in fluoroscopes, as well as increased focus on optimizing fluoroscope performance. There is currently little understanding of variability in the dose-image quality relationship across institutions, fluoroscope vendor and/or generation of equipment. METHODS: We evaluated latest generation fluoroscopes from Phillips, Siemens, GE, and Toshiba, and an older generation Phillips fluoroscope (release date 2003) at three different institutions. Radiation dose was measured using an anthropomorphic dose-assessment phantom with effective dose in mSv estimated from Monte Carlo simulations. Image quality phantom images were scored on a 12-point scale by three blinded reviewers. RESULTS: Fluoroscope effective doses ranged from 0.04 to 0.14 mSv/1,000 pulses for fluoroscopy with associated composite image quality scores ranging from 8.0 ± 0.6 to 10.4 ± 1.3. For cineangiography, effective doses ranged from 0.17 to 0.57 mSv/1,000 frames with image quality scores ranging from 10.1 ± 0.3 to 11.1 ± 0.3. There was modest correlation between effective dose and image quality (r = 0.67, P = 0.006). The older generation fluoroscope delivered consistently higher doses than the newer generation systems (2.3- to 3.5-fold higher for fluoroscopy; 1.1- to 3.4-fold higher for cineangiography) without appreciable differences in image quality. CONCLUSION: Technological advances have markedly improved fluoroscope performance. Comparing latest generation systems across vendors and institutions, we found variability in the dose-IQ relationship and speculate that this reflects both equipment and institutional optimization practices.

Abstract 12670: Variability in Radiation Dose and Image Quality: A Comparison Across Fluoroscopy-system Vendors and Generations of Equipment.

INTRODUCTION: Increased recognition of the potentially harmful effects of ionizing radiation has spurred technological advances to reduce exposure during fluoroscopy. However there is currently little understanding of the dose-image quality (IQ) relationship between fluoroscopy vendors and across generations of equipment used for imaging during pediatric catheterization. METHODS: We evaluated latest generation fluoroscopy systems from Phillips, Siemens, GE and Toshiba, and an older generation Phillips system (2004 release). Fluoroscopy and cineangiography were performed on a tissue simulation anthropomorphic phantom using a standardized imaging approach. Phantom surface exposures were used for Monte Carlo simulations to calculate radiation effective dose, accounting for differences in beam parameters. We also imaged a fluoroscopy IQ phantom to assess contrast-detail and line-per-inch visualization. IQ images were scored by 3 blinded reviewers with scores averaged to produce a composite rating (scale 0-18). To assess the impact of imaging approach we then simulated a neonatal cardiac catheterization incorporating "typical" imaging protocols provided by institutions using the various systems. RESULTS: Effective doses and IQ scores are summarized in the table. Effective doses varied by >400% with the older generation system consistently delivering markedly higher doses. The associated figure summarizes dose and IQ for a simulated neonatal cardiac catheterization which accounts for measured doses as well as the reported institutional imaging parameters summarized in the figure legend. CONCLUSION: These data demonstrate substantial technological improvements in fluoroscopy equipment and may be useful to justify institutional "upgrades". Comparing latest generation systems across vendors and institutions, we found variability in the dose-IQ relationship that reflects both equipment and imaging approach.

Management of pediatric tachyarrhythmias on mechanical support.

BACKGROUND: Pediatric patients with persistent arrhythmias may require mechanical cardiopulmonary support. We sought to classify the population, spectrum, and success of current treatment strategies. METHODS AND RESULTS: A multicenter retrospective chart review was undertaken at 11 sites. Inclusion criteria were (1) patients <21 years, (2) initiation of mechanical support for a primary diagnosis of arrhythmias, and (3) actively treated on mechanical support. A total of 39 patients were identified with a median age of 5.5 months and median weight of 6 kg. A total of 69% of patients were cannulated for supraventricular tachycardia with a median rate of 230 beats per minute. A total of 90% of patients were supported with extracorporeal membrane oxygenation for an average of 5 days. The remaining 10% were supported with ventricular assist devices for an average of 38 (20-60) days. A total of 95% of patients were treated with antiarrhythmics, with 43% requiring >1 antiarrhythmic. Amiodarone was the most frequently used medication alone or in combination. A total of 33% patients underwent electrophysiology study/transcatheter ablation. Radiofrequency ablation was successful in 9 patients on full flow extracorporeal membrane oxygenation with 3 radiofrequency-failures/conversion to cryoablation. One patient underwent primary cryoablation. A total of 15% of complications were related to electrophysiology study/ablation. At follow-up, 23 patients were alive, 8 expired, and 8 transplanted. CONCLUSIONS: Younger patients were more likely to require support in the presented population. Most patients were treated with antiarrhythmics and one third required electrophysiology study/ablation. Radiofrequency ablation is feasible without altering extracorporeal membrane oxygenation flows. There was a low frequency of acute adverse events in patients undergoing electrophysiology study/ablation, while on extracorporeal membrane oxygenation.

Laser lead extraction in congenital heart disease: a case-controlled study.

INTRODUCTION: Patients with congenital heart disease (CHD) and implanted cardiac rhythm management devices have a high rate of endocardial lead issues requiring lead extraction. Laser lead extraction (LLE) is a promising modality for lead management though few studies have evaluated this technique in CHD. METHODS: This is a retrospective, case-controlled (gender- and age-matched, without CHD) analysis of all CHD patients from 2002-2010 at a single institution who underwent LLE as a primary extraction modality. The aim is to evaluate the utility of LLE in patients with CHD compared with controls without CHD. The primary outcome is LLE clinical success. Secondary outcomes include procedural success, complications, and factors related to LLE failure. RESULTS: Twenty-two patients with CHD underwent 24 LLE procedures to extract 35 leads. These were compared with 22 patients without CHD who underwent 24 LLE procedures to extract 37 leads. LLE clinical success was achieved for 26 of 35 leads (74%) in patients with CHD versus 35 of 37 leads (92%) in patients without CHD [P = 0.02]. No factors within the CHD group predicted LLE failure. Six of the nine leads for which LLE was unsuccessful were extracted using other methods. No complications were observed in the CHD group. CONCLUSIONS: Patients with CHD are less likely to have successful LLE than gender- and age-matched controls without CHD. LLE failures in CHD may be related to calcified adhesions. Mechanical-rotational devices and the femoral snare technique are useful for LLE failures. LLE provides an effective first-line approach for patients with CHD.

Transthoracic percutaneous access for electroanatomic mapping and catheter ablation of atrial tachycardia in patients with a lateral tunnel Fontan.

BACKGROUND: The incidence of atrial tachycardia following Fontan surgery is high, but access to the pulmonary venous atrium, a frequent site of arrhythmia origin, is limited. OBJECTIVES: The purpose of this study is to report our results with a novel transthoracic percutaneous technique that provides direct access to the pulmonary venous atrium for electrophysiologic procedures. METHODS: Six transthoracic ablation procedures were performed in five patients (age 1.2-17 years, weight 9.2-68.4 kg) with a lateral tunnel Fontan. Under biplane fluoroscopy, a percutaneous needle was advanced at the selected intercostal space toward the pulmonary venous atrium. Once access was confirmed, a sheath was placed over a wire and a Navistar CARTO catheter advanced for mapping and ablation. Additional catheters were placed in the baffle and esophagus for pacing and reference. Atrial tachycardia was induced, electroanatomic mapping performed, and candidate areas tested with entrainment techniques. Radiofrequency ablation was performed and success defined as the inability to reinduce tachycardia using the initiating protocol. RESULTS: All tachycardias were ablated. Procedure time ranged from 3.7 to 4.9 hours, and fluoroscopy time ranged from 31 to 70 minutes. Hospital stay was 2 days. One patient had a pneumothorax and two had a hemothorax that was drained. Tachycardia recurred in one patient at 3 months. Ablation was repeated successfully. Four patients are free of tachycardia at follow-up ranging from 6 to 29 months. Follow-up is not available for one child. CONCLUSION: Transthoracic percutaneous access provided a direct route to the pulmonary venous atrium for successful mapping and radiofrequency ablation in Fontan patients.