title: Global myocardial contractile reserve assessed by high-dose dobutamine stress echocardiography predicts response to the cardiac resynchronization therapy.
abstract: BACKGROUND
  Myocardial contractile reserve (CR) is a strong prognostic factor in patients with heart failure. The presence of significant myocardial fibrosis can lead to a reduced response to cardiac resynchronization therapy (CRT). We assumed that myocardial CR assessed by high-dose dobutamine stress echocardiography (DSE) would predict response to CRT.
  
  
  METHODS
  Fifty-two consecutive symptomatic patients with heart failure (New York Heart Association [NYHA] class III), with depressed ejection fraction (EF) of the left ventricle (26.3 ± 6.9%) and dyssynchronous contractions (QRS duration 149.8 ± 23.8 msec) underwent DSE before CRT implantation. The difference in EF at rest and at peak (40 μg/kg per minute) DSE indicated global CR. Responders to CRT were defined by a decrease in left ventricular end-systolic volume of ≥15% and/or an increase in EF of ≥5% after 6 months of CRT.
  
  
  RESULTS
  During high-dose dobutamine infusion, responders (28 patients, 54%) showed a greater increase in EF compared with nonresponders (Δ 11 ± 7% vs. Δ 2 ± 9%, P = 0.007). CR correlated moderately with an improvement in EF after 6 months of CRT (r = 0.50, P = 0.0009). Furthermore, responders showed significant improvement in clinical status, evaluated by a reduction in NYHA functional class (-0.8 ± 0.6 vs. 0.1 ± 0.4, P = 0.02), compared with nonresponders. A 7% exercise-induced increase in EF yielded sensitivity of 79% and specificity of 87% in predicting the response to CRT after 6 months.
  
  
  CONCLUSIONS
  Myocardial CR assessed by high-dose DSE can play a potentially important role in identifying responders to CRT.
authors: Department of Cardiology, Safarik University and East-Slovak Institute of Cardiovascular Diseases, Košice, Slovak Republic.
authors: Pavol
authors: P
authors: Murín
authors: Peter
authors: P
authors: Mitro
authors: Gabriel
authors: G
authors: Valocik
authors: Peter
authors: P
authors: Spurný
mesh_terms: D058406:Cardiac Resynchronization Therapy; D004280:Dobutamine / Q000008:administration & dosage*; D025401:Echocardiography, Stress / Q000379:methods*; D005080:Exercise Test / Q000379:methods; D005260:Female; D053805:Fractional Flow Reserve, Myocardial; D006333:Heart Failure / Q000150:complications / Q000000981:diagnostic imaging* / Q000628:therapy*; D006801:Humans; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D016896:Treatment Outcome; D014665:Vasodilator Agents / Q000008:administration & dosage; D018487:Ventricular Dysfunction, Left / Q000000981:diagnostic imaging* / Q000209:etiology / Q000517:prevention & control
chemical_list: D014665:Vasodilator Agents; D004280:Dobutamine
keywords: cardiac resynchronization therapy; myocardial viability; stress echocardiography