Thrombogenic influence of biomaterials in patients with the Omni series heart valve: pyrolytic carbon versus titanium. 
An opportunity to assess the thromboembolic rates caused by the construction materials on valve replacements is possible with the Omni series of mechanical heart valves.  The Omnicarbon and Omniscience valves are identical in form but differ in that the Omnicarbon valve is constructed entirely of pyrolytic carbon, whereas the Omniscience valve uses titanium for its housing, the rest of its structure being pyrolytic carbon.  The literature was reviewed and a comparison in similar groups of patients was made between these two model valves for their thromboembolic rates in the mitral and aortic positions.  A total of 569 aortic Omnicarbon valves (4,146 patient years [pt yrs.1) had a thromboembolic events (T/E rate) of 0.5% compared with 1.7% for 468 aortic Omniscience (1,552 pt yrs); p < 0.0001.  A total of 298 mitral Omnicarbon valves (3,333 pt yrs) had a T/E rate of 1.6% compared with 2.6% for 716 mitral Omniscience valves (2,134 pt yrs), p < 0.001.  There was no difference in the anticoagulation management between the two model valves although the Omniscience valve required higher prothrombin or International Normalized Rate maintenance levels, which resulted in higher bleeding rates among patients with Omniscience valves.