They are based on the authors opinions and on data from retrospective studies of event rates and anticoagulation levels. The higher INR for single leaflet valves compared to bileaflet valves ignores differences between single leaflet valves. Studies have shown that the newest generation single leaflet valves, such as the Medtronic-Hall valve, have low event rates even at lower INRs. Similarly, there are important diffences in the thrombogenicity of ball valves. Models with cloth covered stents may have significantly higher thromboembolism rates.
Prosthetic heart valves.