Efficacy of LOw-dose DObutamine Stress-Echocardiography to predict Cardiac Resynchronization Therapy Response (LODO-CRT) multicenter prospective study-Design and rationale

Background: Although cardiac resynchronization therapy (CRT) has a well-demonstrated therapeutic effect in selected patients with advanced heart failure on optimized drug therapy, nonresponder rate remains high. The LODO-CRT is designed to improve patient selection for CRT. Design and rationale of this study are presented herein. Methods: LODO-CRT is a multicenter prospective study, started in late 2006, that enrolls patients with conventional indications for CRT (symptomatic stable New York Heart Association class III-IV on optimized drug therapy, QRS ≥120 milliseconds, left ventricular [LV] dilatation, LV ejection fraction ≤35%). This study is designed to assess the predictive value of LV contractile reserve (LVCR), determined through dobutamine stress echocardiography (defined as an LV ejection fraction increase >5 units), in predicting CRT response during follow-up. Assessment of CRT effects will follow 2 sequential phases: in phase 1, CRT response end point is defined as LV end-systolic volume reduction ≥10% at 6 months; in phase 2, both LV end-systolic volume reduction and clinical status via a clinical composite score will be evaluated at 12 months follow-up. Predictive value of LVCR will be compared to other measures, such as LV dyssynchrony measures, through adjusted multivariable analysis. For the purpose of the study, target patient number is 270 (with 95% confidence, 80% power, α ≤ .05). Enrollment should be complete by the end of 2008. Conclusions: The LODO-CRT trial is testing the hypothesis that LVCR assessment, using low-dose dobutamine stress echocardiography test, should effectively predict positive response to CRT both in terms of the reverse remodeling process as well as favorable long-term clinical outcome. Moreover, the predictive value of LVCR will be compared to that of conventional intra-LV dyssynchrony measures.