822 
ANATOMY AND PATHOLOGY 
Figure 4. — Dissected postmortem specimen of the test model. There are bilateral renal infarcts of varying size, 
and thrombotic material protrudes from the lower end of the ring implant (seen in situ). The aorta has been 
left uncut at the point of subtotal constriction. 
with complete detachment and embolization of 
all thrombotic material. 
DISCUSSION 
Experience to date with the renal embolus 
test system suggests that it may represent a 
feasible approach for the in vivo evaluation of 
prosthetic surfaces with respect to their 
thromboembolic propensities. It is worthy of 
note, however, that the test system is subject 
to a number of complications which may give 
rise to misleading results and conclusions, un- 
less appropriate precautionary measures are 
instituted and the limits of the system are rec- 
ognized. Thus, scuffing or abrasion of the aortic 
endothelium near the implant site may initiate 
small foci of thrombosis on the aortic intimal 
surface. These may propagate to involve the 
surface of the ring implant, or fragment to 
form emboli and subsequent renal infarcts. This 
complication has been largely avoided by gentle 
and careful insertion of the test ring. In this 
regard the implantation procedure has been 
greatly facilitated by the use of a mounting 
probe during insertion of the ring implant 
(Figure 6). Rheologic complications may arise 
at the edges of an improperly beveled, blunt 
test ring during the post-operative implanta- 
tion period. Turbulent flow and eddy currents, 
caused by the presence of such blunt ring edges, 
may result in thrombotic deposits which are 
largely rheologic in origin and not due primarily 
to the intrinsic nature of the surface under 
study. To circumvent this difficulty ring im- 
plant edges have been carefully beveled. The 
