Ventricular assist devices (VAD) are being used at increasing rates in patients with severe, end-stage heart failure. Specific indications include VAD placement as a bridge to cardiac function recovery, a bridge to cardiac transplantation, or destination therapy (long-term support for patients ineligible for transplant). The assessment and management of the VAD patient is rather complex, requiring a basic knowledge of device structure and function. This article reviews the basic structure and function, discusses the approach to the VAD patient in the ED, and reviews the more common presentations and complications encountered in these technology-complex patients who are critically ill at baseline.