Biomedical Engineering Reference
In-Depth Information
heart has gained attention in recent years (Akutsu and Kolff, 1958; Jarvick, 1981; DeVries and Joyce,
1983; Unger, 1989; Kambic and Nose, 1991). A number of attempts in the permanent implantation of
TAH with pneumatically powered units were made in the 1980s. However, due to neurological compli-
cations as a result of thromboembolism, infection, and hematological and renal complications, perma-
nent implantations are currently suspended. If a suitable donor heart is not readily available, TAHs can
be used as “bridge to transplantation” for several weeks until a donor heart becomes available. Until
recently, most of the circulatory assist devices were pneumatically driven and a typical pneumatic heart
is shown in Figure 9.8a. It has two chambers for the left and right ventricles with inlet and outlet valves
for each of the chambers. A line coming from the external pneumatic driver passes through the skin and
is attached to the diaphragm housing through the connector shown in the photograph. Thus, the patient
is tethered to an external pneumatic drive. He can move around for a short period of time by attaching
the pneumatic line to a portable driver that he can carry.
Electrically driven blood pumps, which can afford tether-free operation within the body, unlike those
of the pneumatically powered pumps, are currently at various stages of development for long-term use
(of more than 2 years). The components of such devices include the blood pump in direct contact with
FIGURE 9.8
Typical prototype designs of TAHs: (a) pneumatically powered TAH. The right and left ventricular
chambers, inflow and outflow valves, as well as the connector for the pneumatic line are visible in the photograph;
(b) electrically powered TAH. Shown are the external battery pack, transcutaneous energy transmission system
(TETS) primary and secondary coils, implanted electronics, energy converter and the blood pumps, compliance
chamber, and the subcutaneous access port. (Courtesy of G. Rosenberg, Pennsylvania State University.)
