title: [The characteristics during exercise test in long QT syndrome patients and the effects of left cardiac sympathetic denervation].
abstract: OBJECTIVE
  To explore the mechanism of the left cardiac sympathetic denervation (LCSD) surgery to reduce the incidence of cardiac events for long QT syndrome (LQTS) patients.
  
  
  METHODS
  12 LQTS patients were selected to do exercise test (ET) to mimic sympathetic activation. The dynamic alterations on ECG during exercise and recovery phases (Rec) were observed and the exercise test characteristics for LQTS patients before and after surgery were summarized and compared.
  
  
  RESULTS
  The QTc at resting was shortened from 0.54 s +/- 0.04 s to 0.50 s +/- 0.04 s, P = 0.026, while the maximum heart rate during exercise decreased from 141 beat/min +/- 18 beat/min to 124 beat/min +/- 14 beat/min, P = 0.003. QTc was shortened during exercise, however, it was prolonged during the early recovery phase (before ET 0.54 s +/- 0.02 s, ET 10 min 0.46 s +/- 0.02 s, Rec 4 min 0.55 s +/- 0.03 s); LCSD could reduce such abrupt alteration of QTc during early recovery phase (after surgery: before ET 0.53 s +/- 0.03 s, ET 10 min 0.48 s +/- 0.03 s, Rec 4 min 0.53 s +/- 0.05 s). QT/RR interval slope, representing the adaptation response of QT interval to heart rate, became steeper after exercise (from 0.61 +/- 0.06 to 0.71 +/- 0.07 after exercise, P < 0.01). LCSD made the slopes become less steep both before exercise (from 0.61 +/- 0.06 before surgery to 0.55 +/- 0.07 after surgery, P = 0.013) and after exercise (from 0.71 +/- 0.07 before surgery to 0.66 +/- 0.06 after surgery, P = 0.018). Notched T wave alterations occurred in 7 patients at the end of exercise and/or during early recovery phase before surgery, and LCSD diminished such alteration in 4 patients.
  
  
  CONCLUSIONS
  The slope between QT and RR both the pre-exercise and post-exercise slopes, interval becomes less steep after LCSD, which suggests that exaggerated delay in repolarization with decreasing heart rate for LQTS patients is improved by LCSD. This may be one of the mechanisms of LCSD efficacy for treating LQTS patients. Exercise test is one of tools to evaluate the effect of LCSD on LQTS patients.
authors.affiliation: Department of Cardiology, Peking University People's Hospital, Beijing 100044, China.
authors.forename: Cui-lan
authors.initials: CL
authors.lastname: Li
authors.forename: Da-yi
authors.initials: DY
authors.lastname: Hu
authors.forename: Xu-bo
authors.initials: XB
authors.lastname: Shi
authors.forename: Hu
authors.initials: H
authors.lastname: Yang
authors.forename: Ji-yun
authors.initials: JY
authors.lastname: Wang
authors.forename: Yun-qing
authors.initials: YQ
authors.lastname: Mei
authors.forename: Wen-ling
authors.initials: WL
authors.lastname: Liu
authors.forename: Lei
authors.initials: L
authors.lastname: Li
authors.forename: Yu-yun
authors.initials: YY
authors.lastname: Xu
mesh_terms: D000293:Adolescent; D000328:Adult; D004562:Electrocardiography; D005080:Exercise Test; D005260:Female; D006321:Heart / Q000294:innervation*; D006801:Humans; D008133:Long QT Syndrome / Q000503:physiopathology* / Q000601:surgery; D008297:Male; D013562:Sympathectomy