Biomedical Engineering Reference
In-Depth Information
biomaterials used for VADs and TAHs and their surface requirements for
minimal generation of thrombosis. Section 8.5 reviews the refinement methods
of biomaterial surfaces (polymers, metals, ceramics, etc.) and the correlation
between their interface performances and haemocompatibility. Finally, the
methods of blood and tissue compatibility measurement for biomaterials used
for cardiac devices and their international standards are described.
8.2
Historical background of cardiac assist devices
Mechanical hearts are used to assist in cases of congestive heart failure, which
basically decreases the ability to pump blood. There are mainly three possible
scenarios after the surgery of a heart: when the heart becomes too weak to meet
the blood pumping requirements and needs a time of load reduction to recover,
the heart never functions (Frazier et al., 2001) or the heart cannot be fixed (Rose
et al., 2001). If the heart cannot be recovered with surgery, then the best option
to cure the disease would be a heart transplant. Unfortunately, even though there
are insufficient numbers of heart donations, a transplant has to be applicable to a
patient in terms of blood and tissue type. The second best option is then to assist
the heart with mechanical devices while the donor heart becomes available.
These mechanical devices are called ventricular assist devices (VADs). They are
termed left ventricular, right ventricular or biventricular assist device, depending
on which part of the heart is being supported.
These mechanical devices can also be employed for a longer period until
heart transplantation, when patients do not recover successfully from heart
surgery. In this case, the VADs are described as a bridge to transplant. There is
another type of artificial heart, the total artificial heart (TAH), which is applied
for end-stage heart failure. The TAH basically is a replacement for a complete
failing heart.
The early evolution of artificial hearts occurred during 1812±1957. Since
then, there has been rapid development on mechanical heart design and imple-
mentation. In 1812, the pumping blood hypothesis was made by French
physiologist Le Gallois, which proposed that assisting organs might help retain
life. The records show us a number of experimental works related to an organ
perfusion with pumps in 1828±1868 (Ratner et al., 2004). In 1881,
Â
tienne-Jules
Marey published a photograph to demonstrate a blood circulation device,
although it is believed that this was never tried out (Ratner, 2000).
However, it has been only five decades that scientists have been investigating
mechanical cardiac devices and their components. In 1957, the artificial heart
was examined in animals by Dr William Kolff (Ratner et al., 2004). The heart
was made of poly(vinyl chloride). Dr Paul Winchell patented the first artificial
heart in 1963.
