The learning curve for radiofrequency ablation of tachyarrhythmias in pediatric patients. Participating members of the Pediatric Electrophysiology Society

The results of radiofrequency ablation for treatment of supraventricular tachyarrhythmias have been reported to improve with increasing experience; however, the precise nature of the learning curve in children is unknown. From November 1990 to October 1993, 1,546 consecutive procedures from the Pediatric Radiofrequency Ablation Registry were categorized into deciles based on number of prior pediatric procedures at the submitting institution. Negative exponential models were tested for strength of relation between volume of prior experience and 4 measures of outcome: success rate, complication rate, fluoroscopy time, and procedure time. Negative exponential curves described the experience-outcome relations well (r = 0.81 to 0.97). Learning rates were most rapid for successful ablation of left free wall accessory pathways, and slowest for right free wall pathway ablation. These models suggest that, given enough experience, procedural success rates > 90% (regardless of pathway location) and fluoroscopy and procedure times averaging < 40 minutes and 250 minutes, respectively, can be achieved in pediatric patients.

Global Initiative for Children's Surgery: A Model of Global Collaboration to Advance the Surgical Care of Children

BACKGROUND

Recommendations by the Lancet Commission on Global Surgery regarding surgical care in low- and middle-income countries (LMICs) require development to address the needs of children. The Global Initiative for Children's Surgery (GICS) was founded in 2016 to identify solutions to problems in children's surgery by utilizing the expertise of practitioners from around the world. This report details this unique process and underlying principles.

METHODS

Three global meetings convened providers of surgical services for children. Through working group meetings, participants reviewed the status of global children's surgery to develop priorities and identify necessary resources for implementation. Working groups were formed under LMIC leadership to address specific priorities. By creating networking opportunities, GICS has promoted the development of LMIC-LMIC and HIC-LMIC partnerships.

RESULTS

GICS members identified priorities for children's surgical care within four pillars: infrastructure, service delivery, training and research. Guidelines for provision of care at every healthcare level based on these pillars were created. Seventeen subspecialty, LMIC chaired working groups developed the Optimal Resources for Children's Surgery (OReCS) document. The guidelines are stratified by subspecialty and level of health care: primary health center, first-, second- and third-level hospitals, and the national children's hospital. The OReCS document delineates the personnel, equipment, facilities, procedures, training, research and quality improvement components at all levels of care.

CONCLUSION

Worldwide collaboration with leadership by providers from LMICs holds the promise of improving children's surgical care. GICS will continue to evolve in order to achieve the vision of safe, affordable, timely surgical care for all children.

Effectiveness of radiofrequency catheter ablation for treatment of atrial tachycardia

Catheter ablation has been used to treat atrioventricular node reentrant and atrioventricular reentrant tachycardias with extremely high success rates. The suitability of catheter ablation for treatment of atrial tachycardia, a much less common type of supraventricular tachycardia, has not been well addressed. Fifteen patients (8 females) ranging from 10 to 83 years (mean 38 +/- 22) were referred for catheter ablation of supraventricular tachycardia. The diagnosis of atrial tachycardia was established by standard electrophysiologic techniques. A combination of activation and pace mapping was used to identify a suitable site for radiofrequency current catheter ablation. Medical therapy was unsuccessful in all but 1 patient. Two patients had surgically corrected congenital heart disease, 2 had coronary artery disease and 1 had dilated cardiomyopathy. Seven patients had depressed left ventricular function. Six patients had incessant tachycardias. Presumed tachycardia mechanism was automatic in 11 patients and reentrant in 4. Mean tachycardia cycle length was 372 +/- 74 ms. Catheter ablation was acutely successful in 12 patients (80%) with application of 11.1 +/- 6.6 lesions at a mean voltage of 60 +/- 9 V. In the other 3 patients, 16 to 38 lesions were applied. At a mean follow-up of 18.5 +/- 6.5 months, 2 patients have had recurrences with different P-wave morphologies and underwent a second successful catheter ablation procedure. An additional 2 patients had recurrences with the same P-wave morphology and 1 underwent a second successful catheter ablation procedure. Thus, radiofrequency ablation can be used in a diverse population of patients with atrial tachycardia with an acute success rate of 80% and a long-term success rate of 73%.

High density placental mesenchymal stromal cells provide neuronal preservation and improve motor function following in utero treatment of ovine myelomeningocele

PURPOSE

The purpose of this study was to determine whether seeding density of placental mesenchymal stromal cells (PMSCs) on extracellular matrix (ECM) during in utero repair of myelomeningocele (MMC) affects motor function and neuronal preservation in the ovine model.

METHODS

MMC defects were surgically created in 33 fetuses and repaired following randomization into four treatment groups: ECM only (n = 10), PMSC-ECM (42 K cells/cm²) (n = 8), PMSC-ECM (167 K cells/cm²) (n = 7), or PMSC-ECM (250-300 K cells/cm²) (n = 8). Motor function was evaluated using the Sheep Locomotor Rating Scale (SLR). Serial sections of the lumbar spinal cord were analyzed by measuring their cross-sectional areas which were then normalized to normal lambs. Large neurons (LN, diameter 30-70 μm) were counted manually and density calculated per mm² gray matter.

RESULTS

Lambs treated with PMSCs at any density had a higher median SLR score (15 [IQR 13.5-15]) than ECM alone (6.5 [IQR 4-12.75], p = 0.036). Cross-sectional areas of spinal cord and gray matter were highest in the PMSC-ECM (167 K/cm²) group (p = 0.002 and 0.006, respectively). LN density was highest in the greatest density PMSC-ECM (250-300 K/cm²) group (p = 0.045) which positively correlated with SLR score (r = 0.807, p < 0.0001).

CONCLUSIONS

Fetal repair of myelomeningocele with high density PMSC-ECM resulted in increased large neuron density, which strongly correlated with improved motor function.

TYPE OF STUDY

Basic science.

LEVEL OF EVIDENCE

N/A.

Spinal Angulation: A Limitation of the Fetal Lamb Model of Myelomeningocele

INTRODUCTION

The surgically induced fetal lamb model is the most commonly used large animal model of myelomeningocele (MMC) but is subject to variation due to surgical technique during defect creation.

MATERIAL AND METHODS

Thirty-one fetal lambs underwent creation of the MMC defect, followed by defect repair with either an extracellular matrix (ECM) patch (n = 10) or ECM seeded with placental mesenchymal stromal cells (n = 21). Postnatal hindlimb function was assessed using the Sheep Locomotor Rating (SLR) scale. Postmortem magnetic resonance imaging of the lumbar spine was used to measure the level and degree of spinal angulation, as well as cross-sectional area of remaining vertebral bone.

RESULTS

Median level of angulation was between the 2nd and 3rd lumbar vertebrae, with a median angle of 24.3 degrees (interquartile range 16.2-35.3). There was a negative correlation between angulation degree and SLR (r = -0.44, p = 0.013). Degree of angulation also negatively correlated with the normalized cross-sectional area of remaining vertebral bone (r = -0.75, p < 0.0001).

DISCUSSION

Surgical creation of fetal MMC leads to varying severity of spinal angulation in the ovine model, which affects postnatal functional outcomes. Postnatal assessment of spinal angulation aids in standardization of the surgical model of fetal MMC repair.