The Journal of Thoracic and Cardiovascular Surgery, Vol 95, 1067-1082, Copyright © 1988 by The American Association for Thoracic Surgery and The Western Thoracic Surgical Association
The porous metal-surfaced heart valve. Long-term study without long- term anticoagulation in mitral position in goats
VO Bjork, GJ Wilson, JJ Sternlieb and DB Kaminsky
Heart Institute of the Desert, Rancho Mirage, CA 92270.
On review, all thromboembolic complications in mechanical heart valves
start from a thrombus lining that covers the suture ring. The thrombus
organizes to a fibrous white sheet over the suture ring, which then can
protrude out over the polished surface of the valve ring flange. Pieces of
the thrombus can be knocked off by the disc and cause emboli. To diminish
thromboembolic complications, one must either prevent this thrombus from
protruding into the groove between the suture ring and the valve flange or
allow the thrombus to be organized as a thin covering with endothelium-like
cells as a continuation from the suture ring over the valve flange. This
type of covering was obtained during a short period of anticoagulation by
applying a microporous surface to the Bjork-Shiley Monostrut mitral valve.
These valves were implanted in one set of goats and the conventional
Bjork-Shiley Monostrut mitral valve, with a polished surface, in another
set of goats (control group). The two groups were then compared with regard
to the incidence of thromboembolic complications encountered during 1
year's follow-up without anticoagulation. The goats were put to death and
examination revealed the following observations: In the control group, (1)
a varying amount of thrombus formation was found in the groove between the
suture ring and the flange in all nine goats and (2) thrombus formation did
not start on the polished struts or discs in any of the nine goats. In the
group with the microporous Monostrut mitral valve, 19 animals were put to
death and examined: (1) The endothelialized covering over the suture ring,
thinner when carbon coated, continued over the microporous flange, tapering
off in the center of the orifice in all 19 valves on the ventricular side
and in 14 of the 19 valves on the atrial side; (2) the center of the
orifice and the struts were never completely covered by endothelialized
tissue because of high flow; (3) there was an increased incidence of small
thrombus formation on the disc-contacting microporous surface of both
inflow and outflow struts. Therefore these surfaces should not be coated
but left polished.
