title: Impact of contractile reserve on acute response to cardiac resynchronization therapy.
abstract: BACKGROUND
  Cardiac resynchronization therapy (CRT) provides benefit for congestive heart failure, but still 30% of patients failed to respond to such therapy. This lack of response may be due to the presence of significant amount of scar or fibrotic tissue at myocardial level. This study sought to investigate the potential impact of myocardial contractile reserve as assessed during exercise echocardiography on acute response following CRT implantation.
  
  
  METHODS
  Fifty-one consecutive patients with heart failure (LV ejection fraction 27% +/- 5%, 67% ischemic cardiomyopathy) underwent exercise Doppler echocardiography before CRT implantation to assess global contractile reserve (improvement in LV ejection fraction) and local contractile reserve in the region of the LV pacing lead (assessed by radial strain using speckle tracking analysis). Responders were defined by an increase in stroke volume > or = 15% after CRT.
  
  
  RESULTS
  Compared with nonresponders, responders (25 patients) showed a greater exercise-induced increase in LV ejection fraction, a higher degree of mitral regurgitation and a significant extent of LV dyssynchrony. The presence of contractile reserve was directly related to the acute increase in stroke volume (r = 0.48, p < 0.001). Baseline myocardial deformation as well as contractile reserve in the LV pacing lead region was greater in responders during exercise than in nonresponders (p < 0.0001).
  
  
  CONCLUSIONS
  The present study showed that response to CRT largely depends not only on the extent of LV dyssynchrony and the severity of mitral regurgitation but also on the presence of contractile reserve.
authors.affiliation: Department of Cardiology, CHU Sart Tilman, Liege, Belgium. M.Moonen@student.ulg.ac.be
authors.forename: Marie
authors.initials: M
authors.lastname: Moonen
authors.forename: Mario
authors.initials: M
authors.lastname: Senechal
authors.forename: Bernard
authors.initials: B
authors.lastname: Cosyns
authors.forename: Pierre
authors.initials: P
authors.lastname: Melon
authors.forename: Eric
authors.initials: E
authors.lastname: Nellessen
authors.forename: Luc
authors.initials: L
authors.lastname: Pierard
authors.forename: Patrizio
authors.initials: P
authors.lastname: Lancellotti
mesh_terms: D000208:Acute Disease; D000368:Aged; D002304:Cardiac Pacing, Artificial; D004452:Echocardiography / Q000379:methods*; D005260:Female; D006333:Heart Failure / Q000000981:diagnostic imaging* / Q000517:prevention & control*; D006801:Humans; D008297:Male; D016896:Treatment Outcome; D018487:Ventricular Dysfunction, Left / Q000000981:diagnostic imaging* / Q000517:prevention & control*