title: Measuring left ventricular peak longitudinal systolic strain from a single beat in atrial fibrillation: validation of the index beat method.
abstract: BACKGROUND
  It is traditionally difficult to estimate left ventricular (LV) systolic function in atrial fibrillation (AF). The aim of this study was to validate the use of an index beat, the beat after the nearly equal preceding (RR1) and pre-preceding (RR2) intervals, for the measurement of LV peak longitudinal systolic strain (PLSS). The difference between RR1 and RR2 intervals of the index beat must be <60 msec. LV PLSS measured from the index beat (PLSSindex) was compared with LV PLSS measured from the conventional but time-consuming method of averaging multiple cardiac cycles (PLSSavg).
  
  
  METHODS
  Ninety-eight patients with persistent or permanent AF and resting ventricular rates ≤ 105 beats/min were prospectively included. LV PLSSindex and LV PLSSavg were obtained from two-dimensional speckle-tracking echocardiography.
  
  
  RESULTS
  LV PLSSindex had a highly significant correlation with LV PLSSavg (r = 0.970, P < .001). Bland-Altman analysis showed only small bias of 0.01%, and the 95% limits of agreement were +1.64% to -1.62%. Compared with those with lower risk scores of stroke indicated by CHADS(2) scores < 2 or CHA(2)DS(2)-VASc scores < 2, patients with higher risk scores of stroke indicated by CHADS(2) scores ≥ 2 or CHA(2)DS(2)-VASc scores ≥ 2 had lower PLSSavg and PLSSindex (P ≤ .012).
  
  
  CONCLUSIONS
  LV PLSSindex was a good alternative to LV PLSSavg in patients with AF. Use of the index beat to measure LV longitudinal systolic strain in patients with AF was as accurate as the time-consuming method of averaging multiple cardiac cycles.
authors: Division of Cardiology, Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung Medical University, Kaohsiung, Taiwan.
authors: Chee-Siong
authors: CS
authors: Lee
authors: Tsung-Hsien
authors: TH
authors: Lin
authors: Po-Chao
authors: PC
authors: Hsu
authors: Chun-Yuan
authors: CY
authors: Chu
authors: Wen-Hsien
authors: WH
authors: Lee
authors: Ho-Ming
authors: HM
authors: Su
authors: Wen-Chol
authors: WC
authors: Voon
authors: Wen-Ter
authors: WT
authors: Lai
authors: Sheng-Hsiung
authors: SH
authors: Sheu
mesh_terms: D000368:Aged; D001281:Atrial Fibrillation / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D016009:Chi-Square Distribution; D015150:Echocardiography, Doppler / Q000379:methods*; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D016014:Linear Models; D008297:Male; D009200:Myocardial Contraction / Q000502:physiology; D011446:Prospective Studies; D012044:Regression Analysis; D015203:Reproducibility of Results; D018570:Risk Assessment; D013599:Systole / Q000502:physiology; D018487:Ventricular Dysfunction, Left / Q000000981:diagnostic imaging* / Q000503:physiopathology*