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The porous metal-surfaced heart valve. Long-term study without long-term anticoagulation in mitral position in goats
V O Björk1, G J Wilson, J J Sternlieb
1Heart Institute of the Desert, Rancho Mirage, CA 92270.
Abstract:
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 Björk-Shiley Monostrut mitral valve. These valves were implanted in one set of goats and the conventional Björk-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.
Insights
Thromboembolic complications in mechanical heart valves can be reduced by using microporous surfaces on the Björk-Shiley Monostrut mitral valve, preventing thrombus buildup. However, specific surfaces should remain polished to avoid increased thrombus formation.
Area of Science:
- Biomaterials Science
- Cardiovascular Surgery
- Medical Device Engineering
Background:
- Thromboembolic complications in mechanical heart valves originate from thrombus formation on the suture ring.
- This thrombus can organize, protrude, and dislodge, causing emboli.
- Preventing thrombus protrusion or promoting endothelialization is key to reducing complications.
Purpose of the Study:
- To evaluate the efficacy of a microporous surface on the Björk-Shiley Monostrut mitral valve in preventing thromboembolic complications.
- To compare the incidence of thromboembolic events between microporous and conventional polished valves in a goat model.
- To assess the surface characteristics and tissue integration of microporous versus polished valve surfaces.
Main Methods:
- Implantation of microporous Björk-Shiley Monostrut mitral valves in one group of goats and conventional polished valves in a control group.
- One year follow-up without anticoagulation, followed by necropsy and examination of valve surfaces and thrombus formation.
- Comparison of thrombus formation, surface coverage, and endothelialization between the two valve groups.
Main Results:
- Conventional valves showed thrombus in the suture ring groove in all control goats; no thrombus formed on polished struts or discs.
- Microporous valves exhibited endothelialized covering over the suture ring and flange in most cases.
- Increased small thrombus formation occurred on disc-contacting microporous surfaces, indicating these areas should remain polished.
Conclusions:
- Microporous surfaces on mechanical heart valves can promote endothelialization and reduce thrombus protrusion.
- Certain microporous surfaces, particularly those contacted by the disc, can increase thrombus formation and should be avoided.
- Optimizing valve surface characteristics is crucial for minimizing thromboembolic complications in mechanical heart valve recipients.
