Copyright © American Society of Artiﬁcial Internal Organs. Unauthorized reproduction of this article is prohibited. 639 ASAIO Journal 2016 Review Article There is a large population of patients with end-stage conges- tive heart failure who cannot be treated by means of con- ventional cardiac surgery, cardiac transplantation, or chronic catecholamine infusions. Implantable cardiac devices, many designated as destination therapy, have revolutionized patient care and outcomes, although infection and complications related to external power sources or routine battery exchange remain a substantial risk. Complications from repeat battery replacement, power failure, and infections ultimately endan- ger the original objectives of implantable biomedical device therapy – eliminating the intended patient autonomy, affect- ing patient quality of life and survival. We sought to review the limitations of current cardiac biomedical device energy sources and discuss the current state and trends of future potential energy sources in pursuit of a lifelong fully implant- able biomedical device. ASAIO Journal 2016; 62:639–645. Key Words: pacemaker, total artiﬁcial heart, ventricular assist device, intracorporeal energy, implantable devices In the 1950s, a founder of ASAIO, Dr. Peter Salisbury described the need to treat heart disease with a mechanical device and proposed the idea of a truly artiﬁcial heart. His work chal- lenged the scientiﬁc community to treat chronic heart disease beyond medicines and the operating table. 1 Implantable car- diac devices have revolutionized patient care and outcomes, and are approved as a bridge to transplant, recovery, and also as destination therapy (DT). The number of left ventric- ular assist device (LVAD) systems implanted worldwide has increased considerably and now exceeds the number of heart transplants. Krabatsch et al. suggest that LVAD implantation, not heart transplantation, be the primary therapy for terminal heart failure. 2 Despite the advances in device technology, a sustained, internal power source remains evasive. Implantable cardiac device technology including pace- makers, automatic implantable cardioverter-deﬁbrillators (AICDs), total artiﬁcial hearts (TAHs), and LVADs depend on a safe, reliable, convenient, and continuous power source. Although technology continues to advance, all current devices still require an external power source. Limitations of current devices include, but are not limited to, the need for periodic battery replacement, catastrophic power failure, 3 and trans- cutaneous driveline erosion and infections. 4 These major and other minor complications, related to an external power source, decrease overall survival, quality of life, and patient independence. 5 A fully implantable device with no external connections and a lifelong energy supply can eliminate a signiﬁcant source of morbidity and mortality for patients. 6 Barriers to the creation of a fully implantable device include device size, biodegradable materials, reliability, and a nontoxic energy source with an appropriate life span. Achieving total implantability would reduce the need for future interventions such as battery replacement and minimize host and device complications. 7 We sought to review the limitations of cur- rent cardiac device energy sources and discuss the history, current state, and trends of future potential energy sources that are promising in our pursuit toward a fully implantable cardiac device. Implantable Cardiac Devices Cardiac Pacemakers and Automatic Implantable Cardioverter-Deﬁbrillators History. Initially, pacemakers were powered with a mercu- ry-zinc chemical cell and provided 3–4 years of power. 8 In the 1970s, Plutonium 238 (Pu-238) was used to power pacemak- ers. 9 One hundred and thirty-nine patients received Pu-238- powered pacemakers between 1973 and 1987 at Newark Beth Israel Medical Center. 9–11 Many patients were lost to follow up, but 11 had a fully functional pacemaker for at least 20 years, with the longest reported device survival of 34 years. 11 Based on the institution’s experience, they found the devices to be safe and reliable. Chauvel et al. 12 also found that in follow-up of 325 Pu-238-powered pacemakers, the device survival was 97% at 18.5 years. Despite no reported local or systemic con- sequences to radiation exposure, concerns of extreme toxicity led to the abandonment of nuclear power. 9 Development. In the 1970s, power sources for pacemak- ers and other devices made the transition from mercury–zinc chemical cells to a lithium iodine chemical cell. The lithium iodine cell was smaller in size, more reliable, and provided a longer shelf life than the mercury-zinc cell. 8 The lithium io- dine battery is able to provide pacemakers with 25 μJ 13 for 7–10 years. Because AICDs are required to pace, recognize, and provide high-energy therapy (40 J at 700–800V within a 10–15 msec period) for tachyarrhythmias, their energy Current State and Future Perspectives of Energy Sources for Totally Implantable Cardiac Devices PETER A. BLESZYNSKI,* JESSICA G. Y. LUC,† PETER SCHADE,‡ STEVEN J. PHILLIPS,§ AND VAKHTANG TCHANTCHALEISHVILI¶ Copyright © 2016 by the ASAIO DOI: 10.1097/MAT.0000000000000412 From the *Department of Internal Medicine, University of Rochester Medical Center, Rochester, New York; †Faculty of Medicine and Den- tistry, University of Alberta, Alberta, Canada; ‡Department of Neuro- biology, Harvard Medical School, Boston, Massachusetts; §National Library of Medicine, National Institutes of Health, U.S. Department of Health & Human Services, Bethesda, Maryland; and ¶Division of Car- diac Surgery, Department of Surgery, University of Rochester Medical Center, Rochester, New York. Submitted for consideration March 2016; accepted for publication in revised form June 2016. Disclosures: The authors have no conﬂicts of interest to report. Correspondence: Vakhtang Tchantchaleishvili, Division of Car- diac Surgery, University of Rochester Medical Center, Box Car- diac Surgery, 601 Elmwood Avenue, Rochester, NY 14642. Email: tchantchaleishvili@gmail.com