Just why exactly do tissue valves wear out?

[tigerlily]

We all know that replacement tissue valves eventually wear out. Given that a tissue valve was good and not defective when it was placed, what causes them to wear out and calcify? I know younger people go through them faster than older people. Is it our immune systems attacking the valve? Is it because the valve can't heal itself like live tissue can? Why does the body deposit calcium on them? I sound like a little kid don't I. But why, but why, but why. I read a testimonial for the On-X valve where a guy says his tissue valve was calcifying after about 8 years. He didn't want to go through another surgery that soon so he tried to remove the calcium himself (with supplements I'm guessing). He was successful. The only problem was that the calcium was the only thing holding his tissue valve together and he went into heart failure. So much for trying to remove calcium deposits.

 

[pellicle]

Hi

... Given that a tissue valve was good and not defective when it was placed, what causes them to wear out and calcify?

if you think of the tissue valve as a piece of leather, then eventually with enough opening and closings (think of a wallet) it starts to fray and break down. As to calcification that's an active area of research and while there are some "hot theories" its not totally known yet.

http://www.ncbi.nlm.nih.gov/pubmed/20799226

However, tissular calcification and primary tissue failure (caused by the mechanical stress) are the main unresolved problems. The causes of calcification are numerous and, to date, a satisfactory solution to this question has not been found, although chemical treatments with metal cations, diphosphonates and treatments eliminating phospholipids have proved to mitigate calcification.

I sound like a little kid don't I. But why, but why, but why.

I wish more adults asked questions like they were little kids ...

I'm sorry I don't have more answers, but you know, when we get answers it always leads to more questions

I hope that article helped (both in answering and in giving some directions for further reading

 

[epstns]

pellicle - I read the abstract of the article, and for its time I'm sure it was good information. I wonder, though, what the newer generations of tissue valves are like, compared to those studied for the 2005 article. The valves studied/analyzed for the article would have been a generation or two earlier than tigerlily's and my valves, which are supposed to have superior life expectancies. Of course, we won't know anything about these "third generation" valves for a number of years yet.

Also, the researchers have done some really complicated statistical analysis of the "useful lifespan" of tissue valves, but I don't remember seeing anywhere the minimum and maximum ages of valves in their cohort. In other words, they will publish the mean and average useful lives of valves, but won't admit how soon some fail or how long some can last.

I guess I shouldn't probe too deeply into the stats, though, as I'm pretty thoroughly committed to tissue at this point. If there is a next time, it will be a different decision process I'm sure.

 

[neil]

you would like to thing the newer tissue valves would last longer but no body really knows, stats are good but we shouldn't live by them,

 

[cldlhd]

Well first of all a lot of people out here know a lot more about this subject than me but I'll throw mine out there anyway.I assume everything wears out eventually given enough time and action. This may be a crude analogy but I work for a local water authority and I've seen water eat a hole through steel on a valve from flow. Particularly if the valve is used improperly , such as a butterfly valve used to "throttle" flow rather than just for on or off as intended but I digress. According to my surgeon one of the advantages of having my valve repaired compared to replaced with a tissue is it would remain living tissue and therefore capable of being repaired by my body. As for calcification I'm not convinced anyone really knows. I've read the theory that your body can deposit calcium as an attempt to repair damage to the endothelia.

 

[pellicle]

Hi Steve

normally I dislike replying down this direction and I only answer because its you. I dislike the way that the discussions soon turn to a defensive posturing of choice as if there was any attack on choice to begin with.

pellicle - I read the abstract of the article, and for its time I'm sure it was good information. I wonder, though, what the newer generations of tissue valves are like...

its a good question. Firstly it was intented as an answer to a question to start the asker thinking about the issues and the known situation. As one who has some background in materials science (and I mean you) you'll know that materials do not really change so fast. Sure there is advertising but then we both know that from discovery of issue -> to fomulation of a materials -> to passing testing -> to making the market is not something which happens in weeks, and I'd say 10 years is not a bad estimate.

The valves studied/analyzed for the article would have been a generation or two earlier than tigerlily's and my valves, which are supposed to have superior life expectancies. Of course, we won't know anything about these "third generation" valves for a number of years yet.

worse, I suspect we won't know much because as research is increasingly privately funded (not publicly funded) there is not only no imperative to publish results but quite the reverse: it becomes a business secret under Intellectual Property protections.

However what we can do is look to see how many of these new generation valves end up here on the form with disturbing stories of early failure. For sure this is not a scientifically valid approach for sampling, but it does provide some information.

Also, the researchers have done some really complicated statistical analysis of the "useful lifespan" of tissue valves, but I don't remember seeing anywhere the minimum and maximum ages of valves in their cohort. In other words, they will publish the mean and average useful lives of valves, but won't admit how soon some fail or how long some can last.

exactly ... because (as you will know) its like asking how long is a piece of string.

Should we expect that newer valves last longer? Well is that a criteria for the maker? Is the maker of the view that 15 years is sufficient and that the expence of longer lasting valves may prohibit their cost. Especially when you consider that there already exists a valve type that is made and proven to last quite well (although bringing with it other issues). I have a 1989 Pajero that did 400,000Km on the engine before I had to do a rebuild. Will I get that long from a new one? Will I get longer? I doubt it because the market no longer values that.

I think that the answer to this lies in a step back and re-assessing things from a different standpoint. When we have a valve replacement we exchange "valvular heart disease" for "prosthetic valve disease". This is an important recognition (and it is the manner in which the medical profession views this). One can be managed, the other can not.

We know that valvular heart disease progresses rapidly after levels of degeneration of the valve is reached. We know that death follows that without intervention. So when making a choice to avoid death we have to pick which type of management we wish to undertake. That is the real choice that the patient makes when choosing tissue or mechanical prosthetic.

 

[epstns]

"I think that the answer to this lies in a step back and re-assessing things from a different standpoint. When we have a valve replacement we exchange "valvular heart disease" for "prosthetic valve disease". This is an important recognition (and it is the manner in which the medical profession views this). One can be managed, the other can not.

We know that valvular heart disease progresses rapidly after levels of degeneration of the valve is reached. We know that death follows that without intervention. So when making a choice to avoid death we have to pick which type of management we wish to undertake. That is the real choice that the patient makes when choosing tissue or mechanical prosthetic. "

That about sums it up in a lot of ways. We are not "cured." We are "repaired." No repair is permanent, no matter what they say. Some last longer than others - under certain conditions. Your point of the patient needing to consider the trade-offs is the crux of the matter. Too many times the doctors tell the patients what the doctor thinks, but the patient is unable (or unwilling) to do the homework to make an informed decision. That's when we get some of the flame wars around here. (Which, under proper conditions, with proper consideration of others, could be healthy debate.)

I know I made some trade-offs in choosing a tissue valve. I considered the data I could get, along with my personal situation and preferences,as well as advice and information from my cardio, and chose the Edwards. Had I been "ready" for replacement some years earlier, I know I would have made a different choice. My cardio and I had a 10-year ongoing discussion of what my options were and the pro's and con's of each. I was incredibly lucky to have such a resource in my cardio (and in his successor). Not everyone has that, and we often try to help them where others have helped us. It doesn't always work out, though, and sometimes comes back to bite us. I'm stubborn, though, and I just keep trying - and I thank you for all that you do in that same manner.

 

[tigerlily]

It sounds like no body knows why valves calcify. You would think scientists would understand this mechanism well by now. K2 is supposed to help the body absorb calcium and put it where it belongs. Vitamin C in theory, helps to repair injured arteries and tissue and lysine in sufficient amounts is supposed to be the glue that mends injured tissue rather than calcium. Magnesium is also critical for dissolving and absorbing calcium. I've also read that vinegar can help to prevent unwanted calcification. I don't know if any of this is true or if any of this might inhibit the process of calcification in the heart, valves or the arteries or even reverse it. In my case, if my aortic tissue valve is beginning to show stenosis, it might be a disaster to try and dissolve the calcium build up through any of the means I've mentioned. What if calcium has deposited there for good reasons. On the other hand, maybe calcium deposits don't need to be there at all and are only deteriorating the function of the valve. In my mind, a tissue valve replacement can't repair itself because it's not alive so it wears out. I don't see why an animal valve replacement couldn't function as scaffolding for our own tissue to grow on the cow or pig valve and eventually replace it. They are already doing this is some cases and not in the lab. See ​http://www.wndu.com/mmm/headlines/59279087.html

 

[andrewgj]

Interesting question. I've been reading quite a lot about it because I'm having an aortic valve replacement soon (for a BAV which has done superbly for 45 yrs but is now tired), and am going the tissue route. The challenge of course is that we won't know if valves coming out now are better until 20 years later, or even equivalent until 10-15 years followup. I'm pondering at the moment whether to try one of the new Edwards valves made with their Resilia material. In that case I'd be one of the people establishing whether or not they're better, and plotting out the Kaplan-Meier curves.