PATHOLOGICAL TECHNIQUES APPLIED TO ARTIFICIAL 
ORGAN RESEARCH. AN ANIMAL MODEL FOR 
THE DETECTION OF SURFACE-INDUCED THROMBOSIS 
AND EMBOLISM 
B. K. Kusserow* 
Selected pathological techniques have been utilized by 
a number of investigators to study prosthesis-induced 
thromboembolic phenomena — one of the foremost prob- 
lems associated with the use of prosthetic circulatory 
devices. 
Prosthesis-induced thrombosis has been investigated 
in a number of laboratories with a variety of animal 
test systems. In general the candidate test material or 
prosthetic device is either implanted into, or coupled 
I directly with the vascular system for varying periods 
of time. Detailed ex vivo observation (optical viewing 
apparatus) or postmortem examination of the implant 
or prosthetic device and associated thrombotic material 
follows. 
An animal test model to assess prosthetic devices and 
synthetic materials for their embolic propensity as well 
as their tendency to thrombosis is here described. In 
this preparation the vascular bed and tissues of the 
kidneys, organs highly susceptible to embolic infarction, 
are utilized as sensitive biologic indicators of embolic 
events originating at the surface of an implant. Experi- 
ence with the test model suggests that thrombosis which 
occurs on the surface of smooth, rigid intravascular im- 
plants may be accompanied by embolic episodes with 
great frequency, and further that the absence of throm- 
botic deposit upon the surface of an intravascular im- 
plant does not rule out the possibility of antecedent 
thrombosis with complete embolization of all thrombotic 
material. 
INTRODUCTION 
During the past decade considerable effort 
has been directed to the fabrication of syn- 
thetic ^-^ and biologic " surfaces for use with 
circulatory assist and vascular prosthetic de- 
vices. Progress has been impressive, but a 
survey of the literature suggests that all such 
surfaces developed to date possess certain im- 
perfections. The problems of surface-induced 
thrombosis and subsequent peripheral emboli- 
zation in particular have stubbornly resisted 
solution. Prosthesis-induced embolic phenom- 
•Depaitment of Pathology. University of Vermont College of 
Medicine, Burlington, Vermont. 
ena represent complications of especial impor- 
tance in viev^^ of the potentially lethal hazards 
of emboli. This is particularly true v^^ithin the 
greater (systemic) circulation where the ma- 
jority of circulatory assist and intravascular 
prosthetic devices are positioned. The necessity 
for thorough evaluation of new surfaces for 
their thrombogenic and embolic propensities is 
thus apparent, and suggests the need of a re- 
liable animal testing model for this purpose. It 
also remains to be added that such evaluation 
would appear to be of particular importance 
with respect to either very smooth, rigid sur- 
faces or surfaces which flex constantly. In such 
cases the possibility exists that thrombotic de- 
posits may be dislodged from the surface with 
increased frequency, due either to poor mechani- 
cal attachment (smooth, rigid surfaces) or 
fragmentation due to incessant wall movement 
(flexing surfaces). 
A variety of animal test systems have been 
utilized to date (1) for the study of surface- 
induced thrombosis and (2) for the evaluation 
of promising new synthetic and biologic sur- 
faces with respect to their ability to retard 
thrombosis. The basic approach used in such 
models involves either implantation into or di- 
rect coupling with the host vascular system for 
varying periods of time. Several investigators 
have utilized rigid cylindrical rings of the candi- 
date test material for purposes of evaluation. 
Rings have been implanted either into the 
vena cava,^2,i3 aorta ^^'^^ or major aortic 
branch. 1^ These vessels have also served as the 
major test sites for fabric vascular graft ma- 
terials.i'^ New materials have also been eval- 
uated within the cardiac chambers in the form 
of sword-like projections arising from the atrial 
wall.^*^ Other workers have incorporated new 
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