Global Myocardial Contractile Reserve Assessed by High-Dose Dobutamine Stress Echocardiography Predicts Response to the Cardiac Resynchronization Therapy

BackgroundMyocardial 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. MethodsFifty-two consecutive symptomatic patients with heart failure (New York Heart Association [NYHA] class III), with depressed ejection fraction (EF) of the left ventricle (26.36.9%) and dyssynchronous contractions (QRS duration 149.823.8msec) underwent DSE before CRT implantation. The difference in EF at rest and at peak (40g/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 6months of CRT. ResultsDuring high-dose dobutamine infusion, responders (28 patients, 54%) showed a greater increase in EF compared with nonresponders ( 11 +/- 7% vs. 2 +/- 9%, P=0.007). CR correlated moderately with an improvement in EF after 6months 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 6months. ConclusionsMyocardial CR assessed by high-dose DSE can play a potentially important role in identifying responders to CRT.