Mechanical for life?
Mechanical for life?
Darren,
I find it disappointing that your surgeon apparently dismisses all tissue types other than homografts. Not that there is anything wrong with a homograft (there isn't). It just may be unnecessarily limiting, if that is what's causing the size issue. It would be interesting to note whether the Carpentier-Edwards Perimount Magna is available in Australia, or even the latest CE valve, being trialed in Germany.
Here is a link to a post that has the links for various valve types and manufacturers (sounds much more confusing than it actually is). The post is the third one down in the thread.:
http://www.valvereplacement.com/forums/showthread.php?t=8653
You're not a gullible person, but just a reminder that the following is not gospel, as it's only my interpretation of what I have read and been exposed to. Others may very well disagree, and may even disagree very well.
What I have read of in terms of mechanicals not lasting a lifetime has not been generally due to a failure of the mechanism, at least since they went past the ball-and-cage setup and the very first ceramic and carbon types, and excluding certain St. Jude Silzone valves.
While some calcification can occur on mechanicals, I don't think I have run across it written up as the reason for an explantation. On uncommon occasions, I have run across readings where tissue growth ("vegetation") on a mechanical has been cited as a cause for explantation. Either way, they were long-term valves, with over 20 years in their owners.
The problem is most often when another issue comes up with the heart, whether it be percussive damage to the tissue at the valve mounting site over time (not as strong an issue with the newer, softer-closing valves), other negative tissue changes over time, an aortic aneurism or dissection, aortic root dilation, damage from endocarditis, or a thrombosis (blood clot).
Heart tissue and aorta problems down the road seem more likely in a congenital bicuspid situation, especially if the tissue tends toward a myxomatous (soft, spongey) nature at the time of surgery. Many people with bicuspid valves do not have this issue, or have it to any extent that it makes any difference in their lifetime, so please don't be unnecessarily upset by this thought.
Here is a link to an interesting technical paper about bicuspid aortic valves, and what can be associated with them in
some cases. If it may bother you, please don't read it. I can fully appreciate the feelings that go along with it. It is a PDF, and has excellent, but graphic pictures of excised human valves.
http://circ.ahajournals.org/cgi/reprint/106/8/900 Here is another paper regarding the sometimes association of BAV and aortic irregularities:
http://atvb.ahajournals.org/cgi/content/full/23/2/351 There is also a site for BAV, mentioned elsewhere in the forums, which may be of interest to you.
Myxomatous tissue can also develop as a result of CHF, and the associated enlargement of the heart muscle.
Rheumatic and disease-damaged hearts may carry the mechanical well, but may require further surgery down the road on other calcifying valves, which would obviate the point of installing a "lifetime" valve to avoid further surgeries. When AVR is due to disease, the condition of other valves at the time of surgery should be considered in the mix.
There aren't good numbers on mechanical longevity that I have found yet, partly because enough years simply haven't passed. However, my
gut feel is that the average installed lifespan of the pre-2003 models is going to be about 25-27 years, with a fair number of people with no other intervening issues making it past 30 years. The post-2003 generation may be even longer in those with no other issues intervening. Again, the average length of time in service would not be mainly due to the devices themselves, which would probably easily outlast their owners if they ran solely on their own merits. If you have a long life ahead of you, a mechanical may well not be a lifetime answer.
On the other hand, it is almost a given that a mechanical valve will outlast any type of tissue valve, especially in a younger patient (under 50 or so), where early calcification tends to limit tissue valve longevity. Barring, of course, a new, intervening heart issue.
Prior to recent innovations in anticalcification processes, homografts (human tissue valves) normally outlasted xenografts (animal tissue valves) in younger recipients. With current models, the jury is out on which will last longer in young patients. This is one reason you may wish to revisit xenografts with your surgeon. However, the longevity of any type of tissue valve in 20-, 30-, or 40-year-old implantees is highly variable.
Best wishes,
