The prevalence of heart failure is increasing, in part due to the aging population and longer survival of patients with heart disease. As heart failure management has progressed, so has the understanding of the role of arrhythmias in heart failure, and of the impact of therapies to treat them. For many clinical scenarios, a rational arrhythmia management strategy has emerged. Equally important to these strategies is the growing recognition of certain treatments that, although seemingly effective at one point in time, are now recognized as having greater potential for harm. This monograph provides the clinician with current fundamentals of arrhythmias in heart failure as they relate to a variety of clinical scenarios. Although a simple strategy for decision making cannot always be derived, clinicians will find the information useful for assessing and managing arrhythmias and arrhythmia risk in their patients with heart failure.