Mileena -- I don't think these valves have ever 'frozen' open or closed. My speculation was that if you can place one of these tissue valves into a position just before the mechanical valve - it could do the work of the mechanical valve. But if BOTH valves were trying to work simultaneously, you could wind up with some real problems -- the idea was that, if the mechanical valve can be locked in the open position, the tissue could then do its job without the problems related to having TWO valves trying the do ONE job.
I'm not sure exactly what kind of failures have been reported with mechanical valves (but I'm sure others here probably know).
(I'm with Lynn -- if researchers can get to a point where they can grow a replacement valve out of a person's own tissue, this would be great. Perhaps even better would be harvesting some stem cells from the person with the heart problem, and somehow getting those cells to develop into a new valve.)
I'm not sure exactly what kind of failures have been reported with mechanical valves (but I'm sure others here probably know).
(I'm with Lynn -- if researchers can get to a point where they can grow a replacement valve out of a person's own tissue, this would be great. Perhaps even better would be harvesting some stem cells from the person with the heart problem, and somehow getting those cells to develop into a new valve.)