title: Novel strain rate index of contractility loss caused by mechanical dyssynchrony. - A predictor of response to cardiac resynchronization therapy-.
abstract: BACKGROUND
  Time-delay indexes are limited in predicting the response to cardiac resynchronization therapy (CRT), partly because they do not reflect the residual left ventricular (LV) contractility. We computed a novel index of LV contractility loss due to dyssynchrony (the strain rate (SR) dispersion index: SRDI) by using the speckle-tracking SR and compared the efficacy of the SRDI, time-delay indexes, and strain delay index (SDI), the previously reported index of wasted energy due to dyssynchrony, for predicting the acute response to CRT.
  
  
  RESULTS
  Echocardiography was performed in 19 heart failure patients (LV ejection fraction (EF) 25 ± 6%) before and 2 weeks after CRT. The standard deviation of time to peak velocity, or strain, was calculated as time-delay indexes. The SRDI was calculated as the average of segmental peak systolic SR minus global peak systolic SR. Longitudinal SDI (L-SDI), longitudinal SRDI (L-SRDI), and circumferential SRDI (C-SRDI) significantly correlated with the change in global longitudinal strain (Δglobal LSt), whereas the time-delay indexes did not. Although the time-delay indexes were comparable between responders (Δglobal LSt ≥ 0.3%) and nonresponders, the L-SDI, L-SRDI, and C-SRDI were greater in responders. The area under the receiver operating characteristic curve of the L-SRDI, L-SDI, and C-SRDI for predicting responders was 0.89, 0.81, and 0.78, respectively.
  
  
  CONCLUSIONS
  The SRDI correlated fairly well with an improvement in global LV systolic function after CRT.
authors.affiliation: Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Iwano
authors.forename: Satoshi
authors.initials: S
authors.lastname: Yamada
authors.forename: Masaya
authors.initials: M
authors.lastname: Watanabe
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Mitsuyama
authors.forename: Hisao
authors.initials: H
authors.lastname: Nishino
authors.forename: Shinobu
authors.initials: S
authors.lastname: Yokoyama
authors.forename: Sanae
authors.initials: S
authors.lastname: Kaga
authors.forename: Mutsumi
authors.initials: M
authors.lastname: Nishida
authors.forename: Hisashi
authors.initials: H
authors.lastname: Yokoshiki
authors.forename: Hisao
authors.initials: H
authors.lastname: Onozuka
authors.forename: Taisei
authors.initials: T
authors.lastname: Mikami
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Tsutsui
mesh_terms: D000328:Adult; D000368:Aged; D058406:Cardiac Resynchronization Therapy / Q000009:adverse effects* / Q000379:methods; D005260:Female; D005500:Follow-Up Studies; D006333:Heart Failure / Q000503:physiopathology* / Q000628:therapy*; D006352:Heart Ventricles / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009200:Myocardial Contraction; D013997:Time Factors