Over the past decade, emerging clinical trial data supported the usefulness of implanted therapeutic cardiac devices (pacemakers and defibrillators) for the treatment of heart failure (HF). Interest has now developed in evaluating the potential of device diagnostics to identify HF patients at risk for clinical events and to be used in the management of HF patients. Initial studies have provided inconsistent results. A number of trial design elements have likely played a role in the lack of positive results, including cohort risk determination, intensity of usual care, intensity of the intervention, and selection of end points for the study. These issues will be important to understand when evaluating future clinical trial results and developing new studies, particularly in other HF patient cohorts such as HF with preserved left ventricular function.