A few things (some of which PJmomrunner asked about)...
You are right that a current mechanical valve, such as a St. Jude, is unlikely to be removable percutaneously. Current percutaneous technology is that the native valve is actually just flattened against the wall of the passage with a stent (the new valve is incorporated into the stent). There isn't really time for removal, as everything is still flowing and the heart is still pumping. Must feel incredibly weird for a few beats. Pass the versed!
At this time, they are functionally inferior to all types of valves that are implanted in the more usual way. Of a certainty, they will improve. It will be interesting to see later if
they can be removed for a new one, when the time comes...
There are quite a few posters on this site who are between 25 and 30 years on their mechanical valves, Joe (of course) included. There are also a number here who have had resurgeries before their 30th year, but they are likely quite overrepresented. They might never have had cause to look for this site, if they hadn't required the reoperation in the first place.
When mechanical valves "don't last," it really means there were other issues in the heart or in the tissue the valve was seated in. As RCB pointed out, they rarely fail in and of themselves.
Here are ten- and twenty- year St. Jude mechanical results from a study that broke them down by length-of-service, as I understand them:
St. Jude Aortic Valve Events
............................at 10 years?..at 20 years?
Required Reoperation............7%........10%
Thromboembolic Event.........18%.......32%
Bleeding Event....................23%......34%
Endocarditis in Valve..............6%.......6%
Valve-Related Mortality..........6%......14%
Valve-Related Morbidity........36%......54%
Source: J Thorac Cardiovasc Surg. 2001 Aug;122(2):257-69;
Twenty-year experience with the St Jude Medical mechanical valve prosthesis. Ikonomidis JS, Kratz JM, Crumbley AJ 3rd, Stroud MR, Bradley SM, Sade RM, Crawford FA Jr.
from:
http://www.ncbi.nlm.nih.gov/entrez/...ve&db=pubmed&dopt=Abstract&list_uids=14688722
After 20 years, 90% have not required reoperation. The issues that cause "failures" of mechanical valves are almost always in our own, all-too-human flesh. Sometimes it's myxomatous tissue problems, sometimes keloid structures, sometimes other valves, cardiovascular disease, complications from lung issues, or accumulated damage from waiting too long to have the first valve done. To clarify for those who might not have seen it in this context, morbidity means disease, not death.
With proper warfarin use, and avoidance of cretins who would have patients go off Coumadin for a hangnail, I am certain (as certain as I am allowed to be as a nonprofessional on this site) that the thromboembolic event percentage would be cut deeply, perhaps in half or better. Warfarin-educated health professionals could change this statistic immensely. Those who listen to Al Lodwick and their fellows here, refuse to go off warfarin for hedging dentists, and demand bridging for other procedures are a big step ahead of the percentages, in my mind. They are not playing into this unnecessary statistic.
As with other statistics, don't read more into these than is there. Some events may be multiple events for the same (unlucky) person, who may not have been knowledgeable about their warfarin, or may have had complementary problems that heightened their valve issues.
Interesting note: endocarditis seems to be relegated to the beginning of new valves' lifecycles, hinting that once the epithelium is healed, the incidence drops dramatically (perhaps to "normal" levels). This goes toward validating a longstanding suspicion of mine that our long-term risk for endocarditis is often misrepresented because of the much higher risk just after surgery.
I favor tissue valves whenever appropriate. However, there are times when a mechanical valve is probably the wisest choice. And a heckuva lot of gray area in between. I would not want to gloss over the value of mechanical valves for those who benefit most from them, or who make them their choice.
Best wishes,