title: Relation between QT and RR intervals in patients with bradyarrhythmias.
abstract: OBJECTIVE
  To investigate the relation between QT and RR intervals in the sick sinus syndrome or high degree atrioventricular block.
  
  
  METHODS
  32 patients with episodes of prolonged RR intervals (> or = 2.6 s) on Holter electrocardiographic recordings.
  
  
  METHODS
  QT and RR intervals were measured manually every 100 to 150 beats on electrocardiographic strips reprinted from the Holter tape over 24 hours. The slope of the QT/RR relation was determined by the linear regression equation for RR intervals < or = 1.4 s (slope 1) and > 1.4 s (slope 2).
  
  
  RESULTS
  Slope 2 (0.0068 (0.0030)) was significantly lower than slope 1 (0.0824 (0.0059), P < 0.0001) in the overall patient population. Slopes 1 and 2 were significantly lower (P < 0.001) in the 23 patients with QT intervals at the preceding RR interval of 1 s (QT1s) of < 0.44 s (0.0692 (0.0053) and 0.0019 (0.0030), respectively) than in the nine patients with QT1s intervals > or = 0.44 s (0.1159 (0.0091) and 0.0194 (0.0055), respectively). Slopes 1 and 2 correlated positively with QT1s interval in all patients.
  
  
  CONCLUSIONS
  The QT/RR relation was comparatively flat when the RR interval was prolonged. Patients with prolonged QT intervals showed exaggerated prolongation of the QT interval with prolonged cycle lengths when compared with patients with normal QT intervals.
authors.affiliation: Department of Laboratory Medicine, Oita Medical University, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Ishida
authors.forename: N
authors.initials: N
authors.lastname: Takahashi
authors.forename: M
authors.initials: M
authors.lastname: Nakagawa
authors.forename: T
authors.initials: T
authors.lastname: Fujino
authors.forename: T
authors.initials: T
authors.lastname: Saikawa
authors.forename: M
authors.initials: M
authors.lastname: Ito
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001145:Arrhythmias, Cardiac / Q000503:physiopathology*; D015716:Electrocardiography, Ambulatory; D005260:Female; D006327:Heart Block / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D012804:Sick Sinus Syndrome / Q000503:physiopathology