title: Strain-time curve analysis by speckle tracking echocardiography in cardiac resynchronization therapy: Insight into the pathophysiology of responders vs. non-responders.
abstract: BACKGROUND
  Patients with non-ischemic heart failure etiology and left bundle branch block (LBBB) show better response to cardiac resynchronization therapy (CRT). While these patients have the most pronounced left ventricular (LV) dyssynchrony, LV dyssynchrony assessment often fails to predict outcome. We hypothesized that patients with favorable outcome from CRT can be identified by a characteristic strain distribution pattern.
  
  
  METHODS
  From 313 patients who underwent CRT between 2003 and 2006, we identified 10 patients who were CRT non-responders (no LV end-systolic volume [LVESV] reduction) with non-ischemic cardiomyopathy and LBBB and compared with randomly selected CRT responders (n = 10; LVESV reduction ≥15%). Longitudinal strain (εlong) data were obtained by speckle tracking echocardiography before and after (9 ± 5 months) CRT implantation and standardized segmental εlong-time curves were obtained by averaging individual patients.
  
  
  RESULTS
  In responders, ejection fraction (EF) increased from 25 ± 9 to 40 ± 11% (p = 0.002), while in non-responders, EF was unchanged (20 ± 8 to 21 ± 5%, p = 0.57). Global εlong was significantly lower in non-responders at pre CRT (p = 0.02) and only improved in responders (p = 0.04) after CRT. Pre CRT septal εlong -time curves in both groups showed early septal contraction with mid-systolic decrease, while lateral εlong showed early stretch followed by vigorous mid to late contraction. Restoration of contraction synchrony was observed in both groups, though non-responder remained low amplitude of εlong.
  
  
  CONCLUSIONS
  CRT non-responders with LBBB and non-ischemic etiology showed a similar improvement of εlong pattern with responders after CRT implantation, while amplitude of εlong remained unchanged. Lower εlong in the non-responders may account for their poor response to CRT.
authors.affiliation: Section of Cardiovascular Imaging, Department of Cardiovascular Medicine, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH, USA.|Department of Cardiology, North Shore Hospital, 124 Shakespeare Rd, Takapuna, Auckland, New Zealand.
authors.forename: Andrew C Y
authors.initials: AC
authors.lastname: To
authors.affiliation: Section of Cardiovascular Imaging, Department of Cardiovascular Medicine, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH, USA.
authors.forename: Rodolfo D
authors.initials: RD
authors.lastname: Benatti
authors.affiliation: Section of Cardiovascular Imaging, Department of Cardiovascular Medicine, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH, USA.
authors.forename: Kimi
authors.initials: K
authors.lastname: Sato
authors.affiliation: Section of Cardiovascular Imaging, Department of Cardiovascular Medicine, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH, USA.
authors.forename: Richard A
authors.initials: RA
authors.lastname: Grimm
authors.affiliation: Section of Cardiovascular Imaging, Department of Cardiovascular Medicine, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH, USA.
authors.forename: James D
authors.initials: JD
authors.lastname: Thomas
authors.affiliation: Section of Electrophysiology, Department of Cardiovascular Medicine, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH, USA.
authors.forename: Bruce L
authors.initials: BL
authors.lastname: Wilkoff
authors.affiliation: Section of Cardiovascular Imaging, Department of Cardiovascular Medicine, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH, USA.
authors.forename: Deborah
authors.initials: D
authors.lastname: Agler
authors.affiliation: Section of Cardiovascular Imaging, Department of Cardiovascular Medicine, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH, USA. popoviz@ccf.org.
authors.forename: Zoran B
authors.initials: ZB
authors.lastname: Popović
mesh_terms: D000465:Algorithms; D002037:Bundle-Branch Block / Q000000981:diagnostic imaging* / Q000503:physiopathology / Q000517:prevention & control*; D058406:Cardiac Resynchronization Therapy / Q000379:methods*; D004452:Echocardiography / Q000379:methods*; D055119:Elastic Modulus; D005260:Female; D006333:Heart Failure / Q000000981:diagnostic imaging* / Q000503:physiopathology / Q000517:prevention & control*; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D016896:Treatment Outcome; D018487:Ventricular Dysfunction, Left / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000517:prevention & control
keywords: Cardiac resynchronization therapy; Dyssynchrony; Left bundle branch block