Heart failure is a progressive disease that decreases the pumping action of the heart. This may cause a backup of fluid in the heart and may result in heart beat changes. When there are changes in the heart beat sometimes an implantable heart device is used to control the rate and rhythm of the heart beat. The purpose of the REVERSE clinical trial is to determine whether pacing in both the left and right ventricles using Cardiac Resynchronization Therapy (CRT) can help slow the progression of heart failure in people who have mild or previous symptoms and poor heart pumping function. This kind of therapy has previously been shown to reduce symptoms and improve exercise capacity in people with more advanced forms of heart failure.

• Placebo Comparator: Cardiac Resynchronization Therapy (CRT) turned OFF in conjunction with optimal medical therapy
• Active Comparator: Cardiac Resynchronization Therapy (CRT) turned ON in conjunction with optimal medical therapy

• Linde C, Abraham WT, Gold MR, St John Sutton M, Ghio S, Daubert C; REVERSE (REsynchronization reVErses Remodeling in Systolic left vEntricular dysfunction) Study Group. Randomized trial of cardiac resynchronization in mildly symptomatic heart failure patients and in asymptomatic patients with left ventricular dysfunction and previous heart failure symptoms. J Am Coll Cardiol. 2008 Dec 2;52(23):1834-43. Epub 2008 Nov 7.
• Linde C, Gold M, Abraham WT, Daubert JC; REVERSE Study Group. Baseline characteristics of patients randomized in The Resynchronization Reverses Remodeling In Systolic Left Ventricular Dysfunction (REVERSE) study. Congest Heart Fail. 2008 Mar-Apr;14(2):66-74.
• St John Sutton M, Ghio S, Plappert T, Tavazzi L, Scelsi L, Daubert C, Abraham WT, Gold MR, Hassager C, Herre JM, Linde C; REsynchronization reVErses Remodeling in Systolic left vEntricular dysfunction (REVERSE) Study Group. Cardiac resynchronization induces major structural and functional reverse remodeling in patients with New York Heart Association class I/II heart failure. Circulation. 2009 Nov 10;120(19):1858-65. Epub 2009 Oct 26.
• Daubert C, Gold MR, Abraham WT, Ghio S, Hassager C, Goode G, Szili-Török T, Linde C; REVERSE Study Group. Prevention of disease progression by cardiac resynchronization therapy in patients with asymptomatic or mildly symptomatic left ventricular dysfunction: insights from the european cohort of the reverse (Resynchronization Reverses Remodeling in Systolic Left Ventricular Dysfunction) trial. J Am Coll Cardiol. 2009 Nov 10;54(20):1837-46. Epub 2009 Oct 1.

Inclusion Criteria:

• Subjects with previously symptomatic heart failure but no current symptoms (New York Heart Association (NYHA) Class I, Stage C) or subjects with mild heart failure that only sometimes interferes with daily activities (NYHA Class II)
• Subjects with a QRS of 120 ms or more (The QRS interval is a measurement of how the electrical signal involved in a heart beat travels/conducts through the ventricles. A wide QRS (120 ms or more) suggests that there is a conduction problem (or block) in the ventricles).
• Subjects with a left ventricular ejection fraction less than or equal to 40%. (The left ventricular ejection fraction (LVEF) is a measurement of how well the left ventricle pumps blood out to the rest of the body. The higher the LVEF the more blood the ventricle is pumping.)
• Subjects with a left ventricular end diastolic dimension (LVEDD) greater than or equal to 55. (The left ventricular end diastolic dimension (LVEDD) is a measurement of heart size taken during an echocardiogram that is one indication of the health of the left ventricle.)

Exclusion Criteria:

• Subjects who are pacemaker dependent (heart would not beat without the help of an implanted device to pace it).
• Subjects with heart failure that severely limits daily activities (NYHA Class III) or subjects with severe heart failure with symptoms while resting (NYHA Class IV).
• Subjects hospitalized due to heart failure within past 3 months.