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Next Generation Ventricular Assist Devices for Destination Therapy
The National Heart, Lung, and Blood Institute convened a Working Group of investigators on October 18, 2004, in Bethesda, Maryland via conference call, to assess challenges and opportunities for developing next-generation ventricular assist devices (VADs) specifically for permanent use, otherwise known as "destination therapy." This group was composed of cardiothoracic surgeons, heart failure cardiologists, and bioengineers, all with significant scientific and/or clinical experience with ventricular assist devices. Their objectives were to: advise the NHLBI on the current state of ventricular assist devices for destination therapy, assess the limitations of currently available VADs, identify all populations that might benefit from destination therapy and the required performance characteristics of mechanical circulatory support devices for each of these populations, suggest strategies to minimize adverse events and prolong safe and effective VAD support, and make prioritized and implementable recommendations for research activities.
Heart transplantation remains severely limited due to a lack of available organs. After reviewing the 2-year results of the Randomized Evaluation of Mechanical Assistance for the Treatment of Congestive Heart Failure (REMATCH) trial, the Food and Drug Administration granted a Premarket Approval for the Thoratec HeartMate VAD to be used for destination therapy and the Centers for Medicare and Medicaid Services expanded Medicare coverage to include such therapy. The substantial number of second- and third-generation devices that are being (or will soon be) tested for safety and efficacy in clinical trials demonstrates continuing interest in VAD development by the biomedical device industry. However, each device currently in clinical use, or under development, has limitations already recognized to retard or jeopardize clinical use. Other treatment alternatives lack the potential for displacing destination therapy as the best option for the growing number of patients with end-stage heart failure. The Working Group concluded that addressing the current shortcomings of LVADs may be the best strategy for improving clinical outcomes for such patients. Furthermore, any improvements that could be made would also result in VADs becoming an attractive therapy to treat patients with less advanced, but progressive, heart failure.
Limitations of currently available VADs
Some limitations are common to most of the VADs currently available (e.g., risks of thromboembolism and infection, invasive surgery, and costs). The issues of durability, size, and gastrointestinal system problems are generally more closely associated with pulsatile flow VADs, while the issues of control strategies and non-pulsatility are commonly associated with continuous flow VADs.
Populations for current- and next-generation VADs
Some discussants suggested that the REMATCH trial results do not provide compelling indications for broader use of VAD destination therapy, due to the cost and morbidity associated with it. In comparison with other less-daunting therapies under development, many heart failure cardiologists do not believe that the risk/benefit ratio for destination therapy is favorable enough for most of their patients. Cardiologists participating in the Working Group indicated that a 50 percent survival at two years, with minimal time in the hospital after implantation, would be considered a more acceptable outcome when considering destination therapy.
Another reason identified for the current low number of destination therapy patients (estimated to reach ~250 in 2004) is the lack of generally accepted guidelines for use of these devices in end-stage heart failure patients. Heart failure treatment guidelines are currently being developed by at least two separate organizations and are expected to include indications for destination therapy. Because the complications associated with the use of currently available VADs are so substantial, the Working Group indicated that major advances in VAD device technology to reduce the confounding co-morbidities are needed.
Strategies to minimize adverse events and to prolong safe and effective VAD support
The Working Group identified the following strategies to minimize adverse events and prolong safe and effective VAD support:
The Working Group recognized that such work will necessarily involve
multidisciplinary teams composed of bioengineers, cardiologists, cardiothoracic
surgeons, materials' scientists, biologists, and other scientists.
Note: In May, 2004, the NHLBI issued a Request for Proposals (NHLBI-HV-05-08) to establish a data and clinical coordinating center to manage a registry of patients receiving a mechanical circulatory support device to treat end stage heart failure. The registry data are expected to facilitate clinical evaluation and patient management, aid better device development, and enhance future research. As such, the registry is expected to have a significant role in addressing the problems of currently available VADs and developing a heart failure risk profile to identify patients most likely to benefit from destination therapy, as recommended by the Working Group
J. Timothy Baldwin, Ph.D., NHLBI, NIH
Working Group Members
Chair: Robert Robbins, MD., Falk Cardiovascular Research Center,
Stanford University Medical Center
Cardiothoracic Surgery Members:
NHLBI Staff Members:
Last updated: April 30, 2005