Toward Total Implantability Using Free-Range Resonant Electrical Energy Delivery System: Achieving Untethered Ventricular Assist Device Operation Over Large Distances Benjamin Waters, BS a , Alanson Sample, PhD a , Joshua Smith, PhD a,b , Pramod Bonde, MD c, * THE PROBLEM Heart failure is a terminal disease with a very poor prognosis and constitutes Medicare’s greatest area of spending, with annual expenditures close to $35 billion. 1 The gold standard of treatment for this disease remains heart transplant; however, only a minority (approximately 2000 per year) of patients can benefit from transplants because of continuing donor shortage. Another alternative, which has shown promise, is mechanical circulatory assistance with ventric- ular assist devices (VAD). 1 An estimated 100,000 patients worldwide can benefit from VAD therapy. 1 The benefit of VAD technology was demonstrated by the randomized evaluation of mechanical assis- tance for the treatment of congestive heart failure trial, which showed a 50% survival benefit for patients assigned to the VAD arm compared with those undergoing maximal medical management. 2 The same trial, however, also showed the limita- tions with the first-generation VADs in terms of large size and mechanical failure. 2–4 These find- ings prompted researchers and industry to concentrate their efforts in minimizing the size of the device, which has been achieved in the past decade with miniature axial and centrifugal pump technology. This advancement has allowed the use of these devices in smaller patients, who were not candidates in the past. 5 a Department of Electrical Engineering, University of Washington, Box 352350,185 Stevens Way, Seattle, WA 98195-2350, USA b Department of Computer Science and Engineering, University of Washington, Box 352350,185 Stevens Way, Seattle, WA 98195-2350, USA c Section of Cardiac Surgery, Yale School of Medicine, 330 Cedar Street, Boardman 204, New Haven, CT 06520, USA * Corresponding author. E-mail address: prambond@hotmail.com KEYWORDS  Free-Range Resonant Electrical Energy Delivery system  Ventricular assist device  Heart disease  Heart failure  Wireless power  Mechanical support Cardiol Clin 29 (2011) 609–625 doi:10.1016/j.ccl.2011.08.002 0733-8651/11/$ – see front matter Ó 2011 Elsevier Inc. All rights reserved. cardiology.theclinics.com