Cardiac resynchronization therapy and ventricular assist devices are two of the many US Food and Drug Administration-regulated medical device technologies that are intended for patients with heart failure. Cardiac resynchronization therapy devices have been shown to significantly improve the quality and potentially the duration of life for patients with moderate-to-severe congestive heart failure and electrical dyssynchrony. Likewise, ventricular assist devices have benefited patients with end-stage heart failure through both bridge-to-transplant and destination therapy. The pivotal trials that supported the first approvals for these devices, as well as subsequent trials, were shaped by unique technologic and patient-related concerns. The US Food and Drug Administration has worked to understand these evolving concerns and the role each should play in the design of trials intended to demonstrate the safety and effectiveness of these critical devices.