title: Single-beat determination of right ventricular function in patients with atrial fibrillation.
abstract: BACKGROUND
  In atrial fibrillation (AF), left ventricular (LV) systolic function positively correlates with the ratio of the preceding to prepreceding RR intervals (RRp/RRpp) and single-beat determination of LV function at a beat with equal RRp and RRpp closely estimates the average value over all cardiac cycles. The study was designed to evaluate the feasibility of single-beat determination that was based on the ratio of RRp/RRpp to accurately assess RV function in AF.
  
  
  METHODS
  In 60 patients with AF, RV fractional area change (RVFAC), RRp and RRpp were measured during 20 beats for each patient. The relationship between RVFAC and RRp/RRpp was evaluated by linear regression analysis. The measured values of RVFAC at the beats with equal RRp and RRpp were compared with the average values over 20 beats. The influence of RRp cycle lengths on the values of RVFAC at the beats with equal RRp and RRpp was examined from the plot of normalized value against RR intervals.
  
  
  RESULTS
  There were a positive linear relationship between RVFAC and RRp/RRpp in all patients (P < 0.001 in all). The RVFAC measured by single-beat method and cycle lengths < 500 ms were usually far below the average values. After excluding beats with cycle lengths < 500 ms, RVFAC determined by single-beat method was very close to the average values (y = 0.96x + 1.91%, r = 0.961; P < 0.001; bias 0.26%).
  
  
  CONCLUSIONS
  RV FAC correlates positively with RRp/RRpp and single-beat determination of RV function is feasible and accurate in patients with chronic AF.
authors.affiliation: Department of Cardiology, Chang Gung Memorial Hospital and College of Medicine, Chang Gung University, Taoyuan, Taiwan.
authors.forename: Shing-Hsien
authors.initials: SH
authors.lastname: Chou
authors.forename: Chi-Tai
authors.initials: CT
authors.lastname: Kuo
authors.forename: Lung-An
authors.initials: LA
authors.lastname: Hsu
authors.forename: Wan-Jing
authors.initials: WJ
authors.lastname: Ho
authors.forename: Chun-Li
authors.initials: CL
authors.lastname: Wang
mesh_terms: D000368:Aged; D001281:Atrial Fibrillation / Q000150:complications* / Q000000981:diagnostic imaging*; D004452:Echocardiography / Q000379:methods*; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D018497:Ventricular Dysfunction, Right / Q000000981:diagnostic imaging* / Q000209:etiology*