• Prospective, multicenter, nonrandomized study. Patients with heart failure symptoms referred for CRT according to the current guidelines for the treatment of chronic heart failure were evaluated for enrollment
• 53 centers in Europe, Hong Kong, and the United States enrolled 498 patients with standard CRT indications (New York Heart Association class III or IV heart failure, left ventricular ejection fraction ≤ 35%, QRS ≥ 130 ms, on stable medical regimen).
• 12 echocardiographic parameters of dyssynchrony (Table 1, p2609), based on both conventional and tissue Doppler-based methods, were evaluated after site training in acquisition methods and blinded core laboratory analysis.
• Response to CRT was evaluated through the use of 2 separately analyzed primary outcomes at 6 months: heart failure clinical composite score (CCS) and relative change in LVESV.

Primary Endpoints

• The ability of the 12 echocardiographic parameters to predict clinical composite score response varied widely, with sensitivity ranging from 6% to 74% and specificity ranging from 35% to 91%; for predicting left ventricular end-systolic volume response, sensitivity ranged from 9% to 77% and specificity from 31% to 93%.
• For all the parameters, the area under the receiver-operating characteristics curve for positive clinical or volume response to CRT was ≤ 0.62. There was large variability in the analysis of the dyssynchrony parameters.

• Indicators of positive CRT response were improved clinical composite score and >=15% reduction in left ventricular end-systolic volume at 6 months.
• Clinical composite score was improved in 69% of 426 patients, whereas left ventricular end-systolic volume decreased >=15% in 56% of 286 patients with paired data.

• Despite promising preliminary data from prior single-center studies, echocardiographic measures of dyssynchrony aimed at improving patient selection criteria for CRT do not appear to have a clinically relevant impact on improving response rates when studied in a multicenter setting such as PROSPECT.
• Thus, at present, the echocardiographic parameters assessing dyssynchrony do not have enough predictive value to be recommended as selection criteria for CRT beyond current indications.
• Given the modest sensitivity and specificity in this multicenter setting despite training and central analysis, no single echocardiographic measure of dyssynchrony may be recommended to improve patient selection for CRT beyond current guidelines.
• Efforts aimed at reducing variability arising from technical and interpretative factors may improve the predictive power of these echocardiographic parameters in a broad clinical setting.