Bio/Mech thought

[Nocturne]

I've seen many studies now that show long term outcomes of mechanical and bioprosthetic valves to be pretty similar. We all know that some individuals are clearly (or not as clearly) better suited to one type over another, etc. so I'm not challenging that. If either sort of valve were unilaterally better than the other, then it would have become the gold standard and the other would have gone the way of the rotary phone by now.

But here's a thought, and it builds on a study someone posted earlier comparing Ross procedure outcomes to outcomes of mechanical valves where the patient's INR was WELL MANAGED, as well as expressed opinions of some posters about how some people don't do a good job of managing their INR (which stands to reason).

If outcomes of bioprosthetic and mechanical valves are similar, and mechanical valve outcomes include people who do a horrid job of managing INR as well as those who do superlative jobs of managing INR, you'd expect that the ones managing their INR very well would have better outcomes than average for their group. Meanwhile, people with bioprosthetic valves don't generally have to do anything to manage them, and their conscientiousness in management should have no impact on outcomes (because they have nothing to manage).

So it would stand to reason that people with mechanical valves who manage their INR very well have overall BETTER outcomes, on average, than tissue valvers.

Does this make any sense?

 

[dick0236]

So it would stand to reason that people with mechanical valves who manage their INR very well have overall BETTER outcomes, on average, than tissue valvers.

Does this make any sense?

Makes sense to me.......especially in the younger person.

 

[tommyboy14]

Hello Nocturne,


I originally posted the study about the mechanical valve recipients matched to Ross procedure patients. Unfortunately, I think that things are a bit more complicated than that.

You assume that the population in tissue and mechanical valves is the same. But in the past, only those young people with a reduced life expectancy were recommended tissue valves, while generally healthier people were recommended mechanical valves. So the underlying populations are generally different. So it is difficult to make such an inference directly.

You would be correct if the people in your tissue and mechanical valve group has exactly the same characteristics. But I suspect that generally healthier people were recommended mech valves, while people that were a bit sicker (with perhaps reduced life expectancy) were recommended tissue valves. So while these life expectancy curves in these papers look like they allow straightforward conclusions, this is probably not the case.

Indeed, if you accept my hypothesis about different underlying populations, and you observed the same life expectancy between mechanical and tissue valves, then you could even conclude the opposite: I.e. given worse baseline health of the average tissue valve recipient, and same impact on life expectancy, would suggest that tissue valve confers a survival advantage compared the the average mech valve recipient.

Of course it could be that with optimal anticoagulation, survival becomes the same again.

But I just really wanted to make the point that the most important determinant of survival is likely underlying baseline health, which is more important than prothesis for life expectancy, regardless if you go tissue, Ross (really an extended version of tissue) and mechanical.

Sorry for the long post, but hope this helps.

Thanks
Tommy

 

[neil]

as you said neither have got the gold award, its good we have a choice which varies from person to person,

 

[tommyboy14]

To add one more thing to this. If you look at my argument above, ex-post studies can you really help you discriminate among valves or these reasons.

Only randomised control trials will be helpful here. Now there are several of those:

Ross Vs Homograft:

http://www.ncbi.nlm.nih.gov/pubmed/20684981

Ross vs Mechanical valve:

https://www.thieme-connect.com/products/ejournals/abstract/10.1055/s-0031-1297536

Tissue vs Mechanical valve:

http://www.ncbi.nlm.nih.gov/pubmed/11028464


Now the first two suggests that Ross is better than a Homograft and Ross is better than mechanical. But the problem with the Homograft study is that the quality of UK homografts deterioated during that study as Heart transplants became more common, and hence high quality homografts rare.

The first two are also only 20 and 100 participants in each sample of the study. While these numbers seem large, it could still be that they are not sufficiently large to draw definitive conclusion, the finding could still be random.

Only the third VA randomised trial has a larger number of people, but it is unclear if the findings from a study from the early 1980's apply to modern prothesis both on the mechanical and tissue valve side.

It is precisely for all of those reasons that it is difficult to give straightforward recommendations re valve choice.
and why your choice is personal.

 

[AZ Don]

Hi,
There is a presentation by a Mayo clinic Dr. that has been posted and much discussed on this forum. If I could summarize the hour long presentation in just a sentence, it basically says what the OP says. That with self management, outcomes with mechanical valves are improved to the point that they can be favored over tissue valves more often (than whatever the general guideline is, something like age 60+ tissue, <60 mechanical). Of course I think Cleveland Clinic's position is that the surgery to replace the valve has improved to the point (at least at the Cleveland clinic) that almost anyone can have tissue valve. So I think it is still undecided. I'm hoping for a 3rd choice, for my leaky valve to hold out until they have developed mechanical valves that don't require blood thinners, or my Cardio's preference, stem cell grown tissue valves.

 

[Nocturne]

Tommyboy, yes it was your post I was referring to. What you are saying does make sense, and thanks.

It reminds me of how I was terrified when I first learned about my bad CAC score, extrapolated how high it was likely to get at different ages even if I were "good" about managing it, and looked at death rates for those different scores. One of the pitfalls I hit was freaking out about how people with a CAC in the 1000s have terrible life expectancy over the course of a decade. What I wasn't seeing was the typical ages of people in those different CAC score groups. Most people with CAC in the 1000s are probably in their 80s and 90s! It's folly to not take that into consideration -- as tinkering with the MESA calculator I posted elsewhere seems to indicate.

I like AZ Don's likely accurate hope that in the future we will have better replacement valves. It may well be that by the time I need AVR, things are more standardized because of an advance in quality/outcomes with one valve type over the others. Knock on wood. I'm too new to this situation to feel thankful about much of it, but it is true that I am fortunate to have a bit of time between now and needing surgery.