B. K. KUSSEROW 
823 
IZ-ZL-iJ 
Mircic 1' srsuM 2 ! 
Figure 5. — Postimplantation specimen of the test system from an animal with several renal infarcts. The ring 
implant (shown divided in Figure), however, was grossly free of thrombus. These findings suggest antecedent 
ring thrombosis with complete detachment and embolization of all thrombus. From Kusserow, Larrow and 
Nichols." 
potential dead space between the outer surface 
of the ring implant and the adjacent pulsating 
aortic wall also represents a location for ad- 
ventitous thrombus formation. Elimination of 
this dead space has been accomplished by care- 
ful wrapping of the aorta with fabric at the im- 
plant site. 
Difficulties may also arise if the test ring is 
too large or is malpositioned in such fashion 
that the ring partially obstructs renal or mesen- 
teric arterial blood flow. This complication can 
generally be avoided by selection of a test ani- 
mal of adequate size and careful positioning of 
the ring implant by means of the mounting 
probe. It also remains to be commented that a 
certain measure of experimental variation is 
unavoidable because of inherent differences in 
host thrombotic propensity from animal to ani- 
mal. In a recent study, however, such host 
factors as whole blood coagulation time, hema- 
tocrit, white blood count and platelet count 
could not be directly correlated with the amount 
of thrombus produced upon caval and intra- 
aortic polished quartz ring implants.^^ 
The potential complications which have been 
cited represent compelling reasons for the ex- 
ercise of appropriate care and caution in the 
interpretation of pathologic findings encoun- 
tered with the use of the renal embolus test sys- 
tem. It is also clear that adequate evaluation of 
a given candidate material or surface is predi- 
cated upon the implantation of a suflftciently 
large number of samples to establish a reason- 
ably reproducible trend or pattern of thrombo- 
