title: Can abnormalities of ventricular repolarisation identify insulin dependent diabetic patients at risk of sudden cardiac death?
abstract: OBJECTIVE
  To study the possible association or QT dispersion and mean QTc intervals, as measured from standard 12 lead electrocardiograms, with baroreceptor-cardiac reflex sensitivity (BRS) in insulin dependent diabetic patients.
  
  
  METHODS
  Comparative study of non-invasive assessment of BRS, QT interval, and QT dispersion.
  
  
  METHODS
  Large teaching hospital.
  
  
  METHODS
  31 young asymptomatic, normotensive, insulin dependent diabetic patients, aged 20-55 years with normal clinical autonomic function.
  
  
  METHODS
  QT intervals and QT dispersion were measured by a single observer blinded to other data about the patients. BRS was measured after activating the baroreflex with a Valsalva manoeuvre, and the rate in change of R-R interval to increasing systolic pressure during phase 4 was measured; in addition sequence analysis of resting systolic blood pressure and heart rate was performed during standing. The alpha coefficient--an index of the overall gain of the baroreflex mechanisms--was estimated from spectral analysis data of systolic blood pressure and pulse interval variability.
  
  
  RESULTS
  Mean (SD) QTc interval was 406 (23) ms, QT dispersion was 44 (13) ms. There was no association between QT dispersion and any measurement of BRS. There was a negative correlation between mean QTc intervals and sequence analysis BRS (r = -0.355, P = 0.049), but no association with Valsalva BRS. The alpha coefficient, showed a significant negative correlation with mean QTc (r = -0.42, P = 0.008).
  
  
  CONCLUSIONS
  Abnormal BRS may be reflected in the heart by global prolongation of ventricular repolarisation, but not by dispersion of ventricular repolarisation. This may, in part, explain the increase in sudden cardiac death seen in IDDM patients.
authors.affiliation: Department of Medicine and Therapeutics, University of Leicester, United Kingdom.
authors.forename: P J
authors.initials: PJ
authors.lastname: Weston
authors.forename: J M
authors.initials: JM
authors.lastname: Glancy
authors.forename: P G
authors.initials: PG
authors.lastname: McNally
authors.forename: H
authors.initials: H
authors.lastname: Thurston
authors.forename: D P
authors.initials: DP
authors.lastname: de Bono
mesh_terms: D000328:Adult; D017704:Baroreflex / Q000502:physiology*; D001795:Blood Pressure Determination; D016757:Death, Sudden, Cardiac / Q000517:prevention & control*; D003922:Diabetes Mellitus, Type 1 / Q000503:physiopathology*; D004562:Electrocardiography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D014636:Valsalva Maneuver