The study will include more than 1,250 patients with heart failure (HF), already receiving current standard HF pharmacological therapy, with a narrow QRS width (< 130 ms) and echocardiographic evidence of left ventricular (LV) dyssynchrony. The study will involve 125 centers worldwide, and is being conducted according to FDA guidelines under an investigational device exemption. Frank Ruschitzka, international co-principal investigator of the study, said: "The objective of this study is to demonstrate that optimal medical therapy plus CRT reduces all-cause mortality or first hospitalization for worsening heart failure in the study population compared to optimal medical therapy alone."