Biomedical Engineering Reference
In-Depth Information
On the other hand, as advised, the haemolysis test alone is not good enough to
determine the blood responses such as coagulation activation (Muller, 2008).
Therefore, other methods such as blood count and SEM are recommended for
comprehensive evaluation.
Sterilization of the test sample is a previous requirement of the assessment
and if the sample cannot be sterilized due to a change on its properties, bacterial
contamination should be investigated. On the other hand, if the product is
supplied without sterilization, the correct method must be considered. A method
such as plasma sterilization should not be applied on polymers as it poses serious
problems to the biomaterial structure (Muller, 2008).
Repetition of cell and blood testing is a stringent requirement in vitro. For
this perspective, to delve into blood±device complex interplay and adequate
evaluation, for example, tested biomaterial inherently induces different res-
ponses from different blood donors, and a combination of investigations with
different blood donors is necessary.
Ex vivo testing is a dynamic, one-pass and continued flow test. The device is
located outside of the living body and attached to the circulatory system. Ex vivo
is mainly applied to evaluate the coagulation effects of biomaterials on blood.
However, in vitro and ex vitro must be followed up by in vivo testing since it is a
clinical and final evolution of mechanical cardiac devices.
In vivo testing is necessary for successful cardiac devices. It is performed
after the medical device is implemented within an animal and then investigated
for a period of time. In other words, in vivo assessment is a simulation of
intended clinical application. In general, the assessment is carried out to
investigate the biocompatibility of the medical device and biomaterials to ensure
that the expected functionality of device meets optimum clinical requirements.
One of the specific purposes of in vivo tests is to determine whether the material
used for medical device is blood compatible or not, which is based on the
thrombus formation. International standards organizations such as ASTM and
ISO provide standards and comprehensive guidelines to evaluate interface in
between blood and cardiac devices.
8.7
Future trends
Cardiac devices have been in great development process and recent
enhancements tend to eliminate thromboembolic complications and extend the
durability. For example, third-generation blood pumps, magnetically or
hydraulically suspended, are bearing-less which offers enhanced durability. A
few of third-generation devices are listed in Table 8.2. Only some of them are in
clinical use (VentrAssist and Incor, etc.) and the rest are still under investigation.
Advances in power systems and reduction in size also provide less surgical
trauma due to easier implantation and better patient mobility.
Principally, blood-contacting surfaces of the cardiac devices are also of great
