There's a lot of information needed to make a good determination. Your age is in a nondescript bracket, where you will need at least one more replacement surgery later if you get a tissue valve, stented or unstented. I chose that route at 52, but it's just as reasonable to choose the mechanical valve route with the anticoagulation therapy. Your lifespan expectation is statistically the same for either choice, as the dangers of blood clots and anticoagulation with mechanical valves seem to balance against the dangers of reoperations with tissue valves over time.
Stented or unstented has to do with whether there is a plastic support piece put into the valve to make it keep its shape better and to avoid valve leakage from deformity under pressure. An unstented valve replaces the entire wall section where the valve was with a new valve wall section. The fact that the entire wall section is being replaced is what gives it stability. A stented valve is instead sewn into the existing arterial walls and relies on a thin, plastic stent to keep its shape, the way the metal ring around a trampoline keeps it round.
The advantage of unstented valves is that the valve should have a larger opening, because it's replacing the arterial walls, rather than fitting inside of them. However, there is a natural notch in the walls, like a little shelf, just above the aortic valve. Some of the new stented valves, like the Carpentier-Edwards Perimount Magna, are mounted with a very thin stent just behind the shelf, so the stent doesn't stick out and interfere with the flow. This is called supraannular mounting, and many of the mechanical valves also take advantage of this mounting style. As such, there is not really as much of an advantage now as there originally was for non-stented valves. The main reasons for tissue valve replacement are eventual degeneration and calcification of the valve, vegetation from infective endocarditis, and various early failures.
Best-known unstented tissue valves include the Toronto Stentless Porcine Valve (distributed by St. Jude Medical in the US), which has been shown to have an average lifespan of 10-15 years, and the Freestyle stentless valve (Medtronics), which has about 12 years of data so far, the most useful appearing to be a study at seven years, showing a reoperation rate of about 5% on mixed age participants (patient age is important in tissue valves, as the younger the patient, the shorter the valve's useful life is apt to be). The Freestyle is treated to reduce calcification, the Toronto is not. Both are porcine (pig) valves. There is a new, unstented valve made of equine pericardium, which doesn't have a lot of long-term data out, simply because it hasn't been out very long. The horse tissue valve is the ATS 3F Bioprosthetic Equine Tissue aortic valve, and it works in a different way than the other valves.
The most recognized stented tissue valves are the Carpentier-Edwards Perimount series (including the Magna) by Edwards Scientific, and the St. Jude Biocor, both of which have statistical track records of 80% or better going over 20 years in older patuients (over 65, the average age of valve repalcements). Another is the Medtronic Mosaic, which has about 13 years of data so far, with similar results for that timespan. The CEP valves are manufactured from cow pericardium (the tough tissue from around the heart), the Biocor is made of porcine leaflets with cow pericardium between them, and the Mosaic is a natural porcine valve. All have been treated to reduce calcification, and preserved in ways that do not pressure-damage the tissue being used.
There are also homografts, which are human donor valves from cadavers (animal tissue valves are called xenografts). They generally have a 15+ year lifespan, and are sometimes used for younger patients or for replacing the pulmonary valve in a Ross Procedure. Cryolife is a well-known preparer and distributor of these valves.
A couple of percutaneously implanted valves (such as Edwards Scientific's Sapien and Medronics' CoreValve devices) have been approved at this time, only for limited use. They can be used to replace an original or a replacement tissue valve if the patient's situation is sufficiently dire. They are sent though the patient's arteries with a catheter, after the original valve has been flattened by a procedure similar to balloon angioplasty. They are then expanded on a stent (or self-expand) into place, much the way a ship model can be opened up inside a bottle. This eliminates open heart surgery, but the procedure is long, has risks of its own, and there is no real data regarding how long the replacement valves will last. These are currently all made with tissue valve inserts. A relatively healthy person would not at this time qualify for this type of valve.
There are a larger number of mechanical valves on the market. They all are engineered to last beyond severl lifetimes' usage, and are usually not replaced for wearing out or failures on the valve's part. The most common are St. Jude Medical Regents and Masters series (the St. Jude is the most common mechanical valve by far), the ATS Open Pivot® Heart Valve, the On-X Life Technologies On-X valve, and the Sorin Carbomedics Top Hat (in the US, with a number of different international lines). These are all manufactured from pyrolytic carbon (one over a titanium skeleton), but have differences in hinge pivot and flow surfaces design and in their carbon manufacturing and formulations. The commonly used ones are bileaflet design, but there may be one tilting disk still on the market (tilting disk may work slightly better for mitral valve use, according to at least one study). The St. Jude has a 30+ year useful lifespan track record so far and counting. The main reasons for replacement are interfering pannus (scar tissue), blood clots on or under the valve, vegetation from infective endocarditis, or placement issues (rubbing). All these mechanical valves are reliable. Perhaps the most advanced currently on the market is the On-X, which has a carbon formulation that does not contain silicon (causes bloodflow drag) and has an anti-pannus design, intended to reduce the possibility of scar tissue interfering with its leaflets.
The Ross Procedure is generally used on younger people, but it still works at 52, and has been done successfully on much older folks. If your valve problem is caused by a bicuspid valve and you show any other signs of enlarged ateries (tendency toward aneurysms), you should take that into account. It can be an indication that your pulmonary valve may eventually fail you in the aortic position due to myxomatous (weakened) tissue that can be associated genetically with those other two issues. I'm sure your surgeon has considered that, so you should ask him or her about it.
Here is one good site for looking at valve surgery information (Cleveland Clinic):
http://my.clevelandclinic.org/heart/disorders/valve/valvetreatment.aspx . Obviously, a site like this forum is good for getting a real feel from others who have been through the procedure or helped others close to them through it.
Whatever you choose to do, embrace it and don't look back. As has often been said on this forum, the only bad valve decision is no decision.
Best wishes,
