title: Comparison of QT/RR relation based on a 15-s averaged ECG and a single beat ECG during atrial fibrillation.
abstract: BACKGROUND
  The aim of this study was to compare QT/RR relation based on a 15-s averaged beat ECG with a single beat ECG during atrial fibrillation (AF) and to determine which was better to estimate the QT interval after sinus restoration.
  
  
  RESULTS
  QT and RR intervals were measured using an automatic QT analyzing system in 33 patients who had both AF and sinus rhythm on the same 24-h Holter ECG recording. In 14 patients, antiarrhythmic drugs (AAD) were administered. QT/RR relations were analyzed from ECG waves obtained by the summation of consecutive QRS-T complexes during each 15-s period (QT/RR-average) and a single beat QRS-T (QT/RR-single). During sinus rhythm, the slope of QT/RR-average did not differ from that of QT/RR-single in patients with and without AAD. On the other hand, during AF, the slope of QT/RR-average was significantly greater than that of QT/RR-single (without AAD: 0.12±0.06 vs. 0.06±0.03, P<0.001; with AAD: 0.15±0.05 vs. 0.08±0.04, P<0.001). During AF, the QT interval at an RR interval of 1.2-s (QT-1.2) determined from QT/RR-average was significantly greater than QT-1.2 from QT/RR-single in patients with and without AAD. QT-1.2 in QT/RR-single during AF was significantly smaller than that during sinus rhythm but QT-1.2 in QT/RR-average during AF was not.
  
  
  CONCLUSIONS
  The QT interval after sinus restoration could be estimated better using QT/RR-average than using QT/RR-single during AF.
authors.affiliation: Division of Cardiology, Shizuoka Red Cross Hospital, Shizuoka, Japan. afujiki@szrc.org
authors.forename: Akira
authors.initials: A
authors.lastname: Fujiki
authors.forename: Masao
authors.initials: M
authors.lastname: Sakabe
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology / Q000627:therapeutic use; D000959:Antihypertensive Agents / Q000494:pharmacology / Q000627:therapeutic use; D001281:Atrial Fibrillation / Q000150:complications / Q000188:drug therapy / Q000503:physiopathology*; D015716:Electrocardiography, Ambulatory / Q000187:drug effects / Q000379:methods*; D005260:Female; D006801:Humans; D006973:Hypertension / Q000150:complications / Q000188:drug therapy; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results
chemical_list: D000889:Anti-Arrhythmia Agents; D000959:Antihypertensive Agents