title: Reproducibility of the QT-variability index in individuals with spinal cord injury.
abstract: OBJECTIVE
  To examine the day-to-day reproducibility of the QT-variability index (QTVI) and the QT-apex variability index (QTaVI) in individuals with spinal cord injury (SCI).
  
  
  METHODS
  Ten individuals with SCI participated in the current study (C2-T10; AIS A-D; 8.6 ± 7.8 years post-injury). On two occasions, with a 10-day interval, a 10-minute resting electrocardiogram was obtained from each participant. The QTVI and QTaVI were analyzed from 256 electrocardiographic beats from all participants, and a separate analysis was performed on those with injuries above the 4th thoracic level. An intraclass correlation coefficient (ICC) test was performed to measure day-to-day reproducibility of these measures and a Bland-Altman test was performed on all participants in order to examine the skewness of the measures.
  
  
  RESULTS
  The reproducibility values were found to be high for both the QTVI (all participants: R=0.892; above T4: R=0.893) and the QTaVI (all participants: R=0.908; above T4: R=0.915). In addition, the reproducibility of QTVI and QTaVI did not appear to be skewed as indicated by Bland-Altman plots.
  
  
  CONCLUSIONS
  Both the QTVI and the QTaVI may be used as reproducible means of assessing cardiac autonomic function in individuals with SCI. Further, a reduction in cardiac sympathetic regulation after high thoracic and cervical level SCI does not appear to influence the day-to-day reproducibility of these measures.
authors.affiliation: Department of Kinesiology, Brock University, 500 Glenridge Avenue, St Catharines, ON L2S 3A1, Canada; Brock-Niagara Center for Health and Well-Being, Brock University, 130 Lockhart Dr, St. Catharines, ON L2T 1W4, Canada.
authors.forename: Hisham
authors.initials: H
authors.lastname: Sharif
authors.affiliation: Department of Kinesiology, Brock University, 500 Glenridge Avenue, St Catharines, ON L2S 3A1, Canada; Brock-Niagara Center for Health and Well-Being, Brock University, 130 Lockhart Dr, St. Catharines, ON L2T 1W4, Canada.
authors.forename: David
authors.initials: D
authors.lastname: Allison
authors.affiliation: Brock-Niagara Center for Health and Well-Being, Brock University, 130 Lockhart Dr, St. Catharines, ON L2T 1W4, Canada; Applied Health Sciences, Brock University, 500 Glenridge Avenue, St Catharines, ON L2S 3A1, Canada.
authors.forename: Deborah
authors.initials: D
authors.lastname: O'Leary
authors.affiliation: Department of Kinesiology, Brock University, 500 Glenridge Avenue, St Catharines, ON L2S 3A1, Canada; Brock-Niagara Center for Health and Well-Being, Brock University, 130 Lockhart Dr, St. Catharines, ON L2T 1W4, Canada. Electronic address: dditor@brocku.ca.
authors.forename: David
authors.initials: D
authors.lastname: Ditor
mesh_terms: D000328:Adult; D000368:Aged; D001341:Autonomic Nervous System / Q000502:physiology; D004562:Electrocardiography; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D013119:Spinal Cord Injuries / Q000503:physiopathology*; D055815:Young Adult
keywords: Autonomic function; Electrocardiogram; QT-interval; Spinal cord injury