title: Dynamic relationship of left-ventricular dyssynchrony and contractile reserve in patients undergoing cardiac resynchronization therapy.
abstract: OBJECTIVE
  Contradicting reports have been published regarding the relation between a dobutamine-induced increase in either cardiac dyssynchrony or left-ventricular ejection fraction (LVEF) and the response to cardiac resynchronization therapy (CRT). Using apical rocking (ApRock) as surrogate dyssynchrony parameter, we investigated the dobutamine stress echocardiography (DSE)-induced changes in left-ventricular (LV) dyssynchrony and LVEF and their potential pathophysiological interdependence.
  
  
  RESULTS
  Fifty-eight guideline-selected CRT candidates were prospectively enrolled for low-dose DSE. Dyssynchrony was quantified by the amplitude of ApRock. An LVEF increase during stress of >5% was regarded significant. Scar burden was assessed by magnetic resonance imaging. Mean follow-up after CRT implantation was 41 ± 13 months for the occurrence of cardiac death. ApRock during DSE predicted CRT response (AUC 0.88, 95% CI 0.77-0.99, P < 0.001) and correlated inversely with changes in EF (r = -0.6, P < 0.001). Left-ventricular ejection fraction changes during DSE were not associated with CRT response (P = 0.082). Linear regression analysis revealed an inverse association of LVEF changes during DSE with both, total scar burden (B = -2.67, 95CI -3.77 to -1.56, P < 0.001) and the DSE-induced change in ApRock amplitude (B = -1.23, 95% CI -1.53 to -0.94, P < 0.001). Kaplan-Meier analysis revealed that DSE-induced increase in ApRock, but not LVEF, was associated with improved long-term survival.
  
  
  CONCLUSIONS
  During low-dose DSE in CRT candidates with baseline dyssynchrony, myocardial contractile reserve predominantly results in more dyssynchrony, but less in an increase in LVEF. Dyssynchrony at baseline and its dobutamine-induced changes are predictive of both response and long-term survival following CRT.
authors.affiliation: Department of Cardiovascular Diseases, University Hospital Gasthuisberg, Catholic University Leuven, Herestraat 49, 3000 Leuven, Belgium.
authors.forename: Ivan
authors.initials: I
authors.lastname: Stankovic
authors.forename: Marit
authors.initials: M
authors.lastname: Aarones
authors.forename: Hans-Jørgen
authors.initials: HJ
authors.lastname: Smith
authors.forename: Gábor
authors.initials: G
authors.lastname: Vörös
authors.forename: Erik
authors.initials: E
authors.lastname: Kongsgaard
authors.forename: Aleksandar N
authors.initials: AN
authors.lastname: Neskovic
authors.forename: Rik
authors.initials: R
authors.lastname: Willems
authors.forename: Svend
authors.initials: S
authors.lastname: Aakhus
authors.forename: Jens-Uwe
authors.initials: JU
authors.lastname: Voigt
mesh_terms: D058406:Cardiac Resynchronization Therapy; D025401:Echocardiography, Stress; D005260:Female; D006333:Heart Failure / Q000401:mortality / Q000503:physiopathology / Q000628:therapy*; D006801:Humans; D053208:Kaplan-Meier Estimate; D018810:Magnetic Resonance Angiography; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D011446:Prospective Studies; D013318:Stroke Volume / Q000502:physiology; D018487:Ventricular Dysfunction, Left / Q000401:mortality / Q000503:physiopathology / Q000628:therapy*
keywords: Contractile reserve; Dobutamine stress echocardiography; Dyssynchrony; Heart failure