A Glance into the Future


LVADs are newly being used on patients as FDA approved devices. Research and development by the biotechnology companies yet continues. At present, two classes of LVADs are at advanced stages of preclinical development. One class is a new generation of pneumatic, direct mechanical ventricular assist devices that are wrapped around the heart and do not directly contact the blood. The second consists of compact axial-flow pumps that do not require a compliance chamber and are capable of delivering a high cardiac output.
LVADs are an up and coming field in artificial organs. At the summer '99 annual conference of the American Society for Artificial Internal Organs (ASAIO), one of the main topics that will be discussed is the LVAD. Areas of concern and future improvement include device changes that would decrease the early hazard of death expereinced by patients in the first few days post-transplantation, and "reverse modeling" that occurs within histologic examination of the myocytes.
The possibilities of a totally implantable device and of harnessing power derived from other muscles of the body are other exciting topics of current interest. These two potential LVAD models are described below.


Implantable VAD

A totally implantable VAD would solve several problems.
The Thoratec Portable Driver
(Thoratec.com)
Risk of infection after implantation of the device would be greatly minimized because there would be no paracorporeal component. An entirely internally contained device would increase the standard of living for patients when discharged from the hopsital. These patients would no longer need to be tethered to a large device or bring around a backpack of batteries when they travel.
For this step to be taken, new technology must be devised. Longer lasting batteries and batteries that can be recharged within the body are being actively researched. The miniaturization of various LVAD components such as the pumping chamber is also being attepted. Presently, there is a size requirement for most implantable VADs (=1.5 sq. m). Successfully shrinking the device without compromising performance would allow a wider range of patients to receive LVAD, such as smaller women and children.
Several LVAD models have the majority of the device implanted internally, with an extracorpereal consol that may be portable. The approved Thoratec device is not of this model, but in Europe and in clinical trials in the US, there is a portable driver included with the system that can be carried or pushed on a cart with ease. This model is better suited for smaller patients whose abdominal cavities are too small to house a fully implantable LVAD.


Muscle Powered VAD

The muscle powered VAD is a unique type of completely internal VAD. Its suggested use will be long-term, mainly as an alternative to heart transplantation. Instead of using electricity, the MVAD harnesses the power available in the latissimus dorsi muscle of the patient. Using an energy converter, the system can then work without batteries or electrical power transmission systems.
An MVAD (Thoratec.com)



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