title: Multicentre study using strain delay index for predicting response to cardiac resynchronization therapy (MUSIC study).
abstract: OBJECTIVE
  Strain delay index (SDI) allows quantification of the wasted contraction or gain of myocardial contractility expected after cardiac resynchronization therapy (CRT). The present multicentre prospective study aimed to assess the accuracy of the SDI in predicting responses to CRT in real-life patients with wide and narrow (<130 ms) QRS complexes.
  
  
  RESULTS
  Implantation of a CRT device was performed in 235 heart failure patients and echocardiography data were analysable in 80% (n= 189) of patients (age 65 ± 12 years, left ventricular ejection fraction = 26 ± 8%, 63 ischaemic, 51 with narrow QRS complexes). Mechanical dyssynchrony before CRT was quantified by the 12-segment standard deviation of peak longitudinal strain by speckle tracking (12SD-ε, 12 standard deviation of time to peak strain by speckle tracking), and SDI, defined as the sum of difference between end-systolic and peak-ε across the 16 segments. Response to CRT was defined as an end-systolic volume reduction (ESVR) at 6 months >15%. After CRT, ESVR>15% was observed in 60% (n= 114/189) of patients, and was greater in non-ischaemic (68 vs. 44%, P= 0.003) and wide QRS patients (65 vs. 49%, P= 0.04). Correlation between 12SD-ε and ESVR was poor (r = 0.18, P= 0.01). In contrast, SDI correlated with reverse remodelling (r = 0.61, P< 0.0001 for all) in both wide and narrow QRS patients and ischaemic and non-ischaemic patients. Decrease in SDI after CRT was greater in responders and correlated with ESVR. Finally, SDI > 25% identified responders to CRT (positive and negative predictive value of 80 and 84%, respectively) with 6% inter-observer variability.
  
  
  CONCLUSIONS
  The present multicentre study suggests that SDI may identify responders to CRT in ischaemic and non-ischaemic patients.
authors.affiliation: Cardiovascular Department, Henri Mondor University Hospital (APHP and INSERM U841), Créteil, France. lim.pascal.hmn@gmail.com
authors.forename: Pascal
authors.initials: P
authors.lastname: Lim
authors.forename: Erwan
authors.initials: E
authors.lastname: Donal
authors.forename: Stéphane
authors.initials: S
authors.lastname: Lafitte
authors.forename: Genevieve
authors.initials: G
authors.lastname: Derumeaux
authors.forename: Gilbert
authors.initials: G
authors.lastname: Habib
authors.forename: Patricia
authors.initials: P
authors.lastname: Réant
authors.forename: Sophie
authors.initials: S
authors.lastname: Thivolet
authors.forename: Nicolas
authors.initials: N
authors.lastname: Lellouche
authors.forename: Richard A
authors.initials: RA
authors.lastname: Grimm
authors.forename: Pascal
authors.initials: P
authors.lastname: Gueret
mesh_terms: D000368:Aged; D058406:Cardiac Resynchronization Therapy; D017147:Defibrillators, Implantable; D015150:Echocardiography, Doppler; D005260:Female; D005602:France; D006333:Heart Failure / Q000000981:diagnostic imaging / Q000401:mortality / Q000503:physiopathology / Q000628:therapy*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D013318:Stroke Volume; D016896:Treatment Outcome; D018487:Ventricular Dysfunction, Left / Q000000981:diagnostic imaging / Q000503:physiopathology*