title: Effect of Left Cardiac Sympathetic Denervation on the Electromechanical Window in Patients with either Type 1 or Type 2 Long QT Syndrome: A Pilot Study.
abstract: BACKGROUND
  Left cardiac sympathetic denervation (LCSD) exerts significant antifibrillatory effects in patients with long QT syndrome (LQTS). Recently, electromechanical window (EMW) has emerged as a novel torsadogenic marker in LQTS, superior to QT interval (QTc) in distinguishing symptomatic from asymptomatic patients.
  
  
  OBJECTIVE
  To explore the hypothesis that LCSD improves EMW most favorably in patients with LQT1.
  
  
  METHODS
  From September 2006 to July 2015, 44 LQT1 and 25 LQT2 patients underwent LCSD. Subset analysis was performed on the six LQT1 and seven LQT2 patients who had echocardiograms both pre-LCSD and ≥3 months post-LCSD. EMW is defined as the time difference (ms) between aortic valve closure and the end of the QT interval, measured from an ECG on the concurrent echocardiogram.
  
  
  RESULTS
  Compared to published normal EMW values of 22 ± 19 ms, pre-LCSD EMW mean values were -78 ± 36 ms in LQT1 and -71 ± 35 ms in LQT2 (P < .001). Following LCSD, there was a 57 ± 35 ms decrease in QTc in LQT1 (P = .16) and 23 ± 21 ms decrease in QTc in LQT2 (P = .3). Overall, there was a 35 ± 57 ms mean improvement in EMW post-LCSD (P = .04). Five of the 6 (83%) LQT1 subjects had a favorable EMW change post-LCSD (mean improvement 56 ± 25 ms, P = .04). Five of the 7 (71%) LQT2 subjects had a favorable EMW change post-LCSD (mean improvement 18 ± 19 ms, P = .2).
  
  
  CONCLUSIONS
  The precise mechanism of the LCSD therapeutic effect in LQTS patients is not fully understood. This pilot study raises the possibility that LCSD's antitorsadogenic effect in patients with LQT1 could be conferred in part by restoration of electromechanical order, evidenced by normalization of the EMW.
authors.affiliation: Division of Pediatric Cardiology, Department of Pediatric and Adolescent Medicine, Mayo Clinic, Rochester, Minn, USA.
authors.forename: Andrew E
authors.initials: AE
authors.lastname: Schneider
authors.affiliation: Division of Cardiovascular Diseases, Department of Medicine, Mayo Clinic, Rochester, Minn, USA.|Windland Smith Rice Sudden Death Genomics Laboratory, Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Rochester, Minn, USA.
authors.forename: J Martijn
authors.initials: JM
authors.lastname: Bos
authors.affiliation: Division of Pediatric Cardiology, Department of Pediatric and Adolescent Medicine, Mayo Clinic, Rochester, Minn, USA.|Division of Cardiovascular Diseases, Department of Medicine, Mayo Clinic, Rochester, Minn, USA.|Windland Smith Rice Sudden Death Genomics Laboratory, Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Rochester, Minn, USA.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Ackerman
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D004452:Echocardiography; D004562:Electrocardiography; D005260:Female; D005500:Follow-Up Studies; D006329:Heart Conduction System / Q000503:physiopathology*; D006352:Heart Ventricles / Q000000981:diagnostic imaging / Q000294:innervation* / Q000503:physiopathology; D006801:Humans; D008133:Long QT Syndrome / Q000175:diagnosis / Q000503:physiopathology / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D010865:Pilot Projects; D012189:Retrospective Studies; D029597:Romano-Ward Syndrome / Q000175:diagnosis / Q000503:physiopathology / Q000601:surgery*; D013562:Sympathectomy / Q000379:methods*; D013564:Sympathetic Nervous System / Q000503:physiopathology / Q000601:surgery*; D016896:Treatment Outcome; D055815:Young Adult
keywords: Electromechanical Window; Genetics; Left Cardiac Sympathetic Denervation; Long QT Syndrome; Pediatric; Sudden Cardiac Death