S PRESENTED IN PLENARY SESSIONS SESSION WG HF: CARDIAC RESYNCHRONISATION IN CHRONIC HEART FAILURE 453 The effect of cardiac resynchronization on disease progression in patients with mild heart failure and an indication for an ICD-results of a randomized double blind study J.B. Young1, W.T. Abraham2 1Cleveland Clinic Foundation, Cleveland, United States of America; 2The Ohio State University Heart Center, Division of Cardiology, Columbus, United States of America Cardiac resynchronization (CRT) improves functional capacity and quality of life in patients with NYHA III/IV heart failure, a wide QRS, with or without an ICD indication. We assessed whether CRT limits disease progression in patients with mild heart failure (NYHA II), a wide QRS and an ICD indication. Methods: The Multicenter InSync ICD Randomized Clinical Evaluation II enrolled NYHA II heart failure patients with LVEF 129 ms, an indication for ICD, and on optimal medical management. Following successful implant of an atrial synchronous biventricular pacemaker with ICD, patients were randomized to ICD only (Control) or to CRT + ICD (CRT) for 6 months. Baseline evaluations were done prior to randomization. Both the patient and the physician assessing heart failure status were blinded to treatment assignment. Peak VO2 was the primary efficacy endpoint. Secondary endpoints included core-lab determined echocardiographic parameters, NYHA class, 6-minute walk distance, quality of life and composite clinical response. Results: A total of 101 patients were randomized to Control and 85 to CRT. There were no statistically significant differences between groups at baseline. The table shows paired results (mean ± SD) at the 6-months (6M) compared with baseline (Base). The P-value reflects between group differences in changes from baseline. A total of 58% of the CRT group versus 36% of the Control group were categorized as improved in their composite clinical response (p=0.01).