Heart failure is the fastest growing cardiovascular diagnosis in North America, and it carries a poor prognosis. To improve survival in heart failure patients, therapies need to reduce either sudden cardiac death (the most common cause of death in patients with New York Heart Association NYHA] Class I or II symptoms) or progressive heart failure (the predominant cause of death in those with NYHA Class III or IV symptoms). Electrical conduction disturbances are common in heart failure and are associated with increased mortality risk. Atrial-synchronized biventricular pacing (cardiac resynchronization therapy CRT]) addresses many of the pathophysiological changes seen in patients with wide QRS complexes in whom delayed activation of the left free wall results in mechanical dyssynchrony. The University of Alberta Evidence-based Practice Center conducted a systematic review to examine the success rate and safety of biventricular pacemaker implantation and the efficacy of CRT in patients with heart failure. Further, the researchers used these data in a decision analysis to evaluate the incremental cost effectiveness of CRT versus medical therapy alone. This report addresses the following questions: 1. In adult patients with symptomatic heart failure, is CRT more effective than optimal medical care alone? 2. Is the implantation of a CRT system safe for patients? 3. What is the role of CRT in the treatment of heart failure? 4. What is the cost-effectiveness of CRT in patients with congestive heart failure?