A considerable number of cardiovascular devices have been
introduced into the field of interventional therapy of congenital
heart defects-especially during the last two decades [1-3]. Nowadays,
more and more lesions can be treated in the cath lab. Subsequently,
more and more patients live a long time with metal and/or textile
devices in their body. Of course, clinical data have been published
on interventional cardiovascular devices. However, the majority of
these publications focus on feasibility and safety of the implantation
procedure as well as clinical results. In contrast, limited data have
been reported on in vivo-biocompatibility and long-term local
tissue reactions [4,5]. Finally, even less publications are available on
clinically relevant problems related to interventional cardiovascular
devices. Thromboembolic events with embolisation, residual
shunting, dislocation of the device, and growing thrombus formation
on the device have been reported in literature [6-9]. On the other
hand, the number of major events is very small in the light of total, of
currently about 200,000 occlusion devices implanted in cardiac septal
defects.
As a pediatric cardiologist, I am happy to be able to offer a
therapeutical approach to a cardiac defect avoiding open heart surgery
for certain types of congenital heart defects. But at the same time, I
am concerned about the lack of information on long term effects of
the incorporated foreign material. I would like to tell parents about
the fate of the septal occluder six or seven decades after implantation
in their child.
It's not that we know nothing: It has been shown that neoendothelialisation
rapidly proceeds and usually is completed 3 to
6 months after implantation [10,11]. Within occlusion devices,
initial deposition of fibrin and blood cells could be demonstrated
to be transformed into fiber-rich granulation tissue with a chronic
inflammatory response [4,5]. The time course of this process was
clearly material-dependent [12]. And it has been shown that findings
in explanted human septal occlusion devices closely corresponded to
findings in animal studies [13]. But for gaining all these information,
careful and skilled work-up of explanted devices is necessary. In
addition, experience is needed in cardiovascular pathology for
assessment of findings. The only proposal for evaluation and judging biological responses to medical devices is the ISO 10993-6; 2007. But
suggestions in this document are very vague and leave much space for
subjective interpretation.
Taken together all information that we have on biocompatibility
of cardiovascular devices we have reason to believe that our patients
do not take an intolerable risk when they receive a permanent device.
But believing is not enough in this context. For the sake of safety of
our patients we need as much information as possible. And for that
reason it should be mandatory that all data on animal experiments
should be made public prior to approval for clinical application by
local authorities. And moreover every one of us should take care
that every device that was explanted (for whatever reason) should
undergo careful and thorough histopathological work-up in order to
learn more about long-term tissue reactions and possible problems
with regard to the highly promising field of interventional therapy of
cardiovascular lesions.
