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Objectives: This study sought to develop an actively tracked cardiac magnetic resonance-guided electrophysiology (CMR-EP) system and perform first-in-human clinical ablation procedures., Background: CMR-EP offers high-resolution anatomy, arrhythmia substrate, and ablation lesion visualization in the absence of ionizing radiation. Implementation of active tracking, where catheter position is continuously transmitted in a manner analogous to electroanatomic mapping (EAM), is crucial for CMR-EP to take the step from theoretical technology to practical clinical tool., Methods: The setup integrated a clinical 1.5-T scanner, an EP recording and ablation system, and a real-time image guidance platform with components undergoing ex vivo validation. The full system was assessed using a preclinical study (5 pigs), including mapping and ablation with histological validation. For the clinical study, 10 human subjects with typical atrial flutter (age 62 ± 15 years) underwent MR-guided cavotricuspid isthmus (CTI) ablation., Results: The components of the CMR-EP system were safe (magnetically induced torque, radiofrequency heating) and effective in the CMR environment (location precision). Targeted radiofrequency ablation was performed in all animals and 9 (90%) humans. Seven patients had CTI ablation completed using CMR guidance alone; 2 patients required completion under fluoroscopy, with 2 late flutter recurrences. Acute and chronic CMR imaging demonstrated efficacious lesion formation, verified with histology in animals. Anatomic shape of the CTI was an independent predictor of procedural success., Conclusions: CMR-EP using active catheter tracking is safe and feasible. The CMR-EP setup provides an effective workflow and has the potential to change the way in which ablation procedures may be performed., (Copyright © 2017 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

D8/17, an alloantigen found on B lymphocytes, has been reported to be elevated in patients susceptible to rheumatic fever and may be associated with autoimmune types of neuropsychiatric disorders. The pediatric-autoimmune-neuropsychiatric-disorders-associated-with-streptococci model is a putative model of pathogenesis for a group of children whose symptoms of obsessive-compulsive disorder and Tourette's disorder (TD) are abrupt and may be triggered by an infection with group A streptococci. As a test of this model, we have examined D8/17 levels on the B cells of patients with TD and acute rheumatic fever (ARF) along with those on the B cells of normal controls by flow cytometry. We have utilized several different preparations of D8/17 antibody along with a variety of secondary antibodies but have been unable to show an association with an elevated percentage of D8/17-positive, CD19-positive B cells in either ARF or TD. We did find, however, that the percentages of CD19-positive B cells in ARF and TD patients were significantly elevated compared to those in normal controls. Group A streptococcal pharyngitis patients also had an elevated percentage of CD19 B cells, however. These studies failed to confirm the utility of determining the percentage of B cells expressing the D8/17 alloantigen in ARF patients or our sample of TD patients. In contrast, the percentage of CD19-positive B cells was significantly elevated in ARF and TD patients, as well as group A streptococcal pharyngitis patients, suggesting a role for inflammation and/or autoimmunity in the pathogenesis of these disorders.