title: Contractile reserve assessed by dobutamine test identifies super-responders to cardiac resynchronization therapy.
abstract: BACKGROUND
  In this study, we sought to determine whether myocardial contractile reserve (CR) assessed by dobutamine stress echocardiography (DSE) can identify patients who experience nearly complete normalization of left ventricular (LV) function after the implantation of a cardiac resynchronization therapy (CRT) pacemaker.
  
  
  METHODS
  The study group consisted of 55 consecutive patients with non-ischemic dilated cardiomyopathy, LV ejection fraction (LVEF) < 35%, and prolonged QRS complex duration, who were scheduled for CRT pacemaker implantation. The DSE (20 µg/kg/min) was performed in all patients. The CR assessment was based on a change in the wall motion score index (ΔWMSI) and ΔLVEF during DSE. Super-response was defined as an increase in LVEF to > 50% and reduction in left ventricular end-systolic dimension to < 40 mm 12 months following the CRT implantation.
  
  
  RESULTS
  A total of 7 patients (12.7%) were identified as super-responders to CRT. When compared to non-super-responders, these patients had significantly higher values of the dobutamine-induced change in ΔWMSI (1.031 ±0.120 vs. 0.49 ±0.371, p < 0.01), and ΔEF (17.9 ±2.2 vs. 8.8 ±6.2, p < 0.01). Receiver operating characteristic analysis showed that dobutamine-induced changes in ΔWMSI ≥ 0.7 and ≥ 14% for ΔEF are the best discriminators for a super-response. Patients with ΔWMSI ≥ 0.7 and ΔEF ≥ 14% are significantly less often hospitalized (p < 0.01) for worsening of heart failure during 28.5 ±3.0 months of the follow-up.
  
  
  CONCLUSIONS
  Contractile reserve assessed by DSE can identify patients with dilated cardiomyopathy who are likely to experience near normalization of LV function following CRT.
authors.affiliation: Institute for Cardiovascular Diseases Dedinje, Belgrade, Serbia.
authors.forename: Dejan
authors.initials: D
authors.lastname: Vukajlovic
authors.affiliation: Pacemaker Center, Clinical Center of Serbia, Belgrade, Serbia.
authors.forename: Goran
authors.initials: G
authors.lastname: Milasinovic
authors.affiliation: Institute for Cardiovascular Diseases Dedinje, Belgrade, Serbia.
authors.forename: Lazar
authors.initials: L
authors.lastname: Angelkov
authors.affiliation: Institute for Cardiovascular Diseases Dedinje, Belgrade, Serbia.
authors.forename: Velibor
authors.initials: V
authors.lastname: Ristic
authors.affiliation: Institute for Cardiovascular Diseases Dedinje, Belgrade, Serbia.
authors.forename: Milosav
authors.initials: M
authors.lastname: Tomovic
authors.affiliation: Institute for Cardiovascular Diseases Dedinje, Belgrade, Serbia.
authors.forename: Ruzica
authors.initials: R
authors.lastname: Jurcevic
authors.affiliation: Institute for Cardiovascular Diseases Dedinje, Belgrade, Serbia.
authors.forename: Petar
authors.initials: P
authors.lastname: Otasevic
keywords: cardiac resynchronization therapy; contractile reserve; dobutamine stress echocardiography; super-response