On-X vs ATS open-pivot - The Truth is Out There

[pem]

The truth is out there, but it sure is elusive

I have done an exhausting (if not exhaustive) exploration of On-X vs ATS.

Here is a summary of my very subjective findings based on possibly objective data. So, IMHO:

I think these valves are comparable in many respects. There are some apparent differences, and positive or negative spins can be put on these. For example, the On-X valve purports to have a very low incidence of pannus resulting from some chemicals that inhibit growth in the sew ring. The flip side is that On-X seems to have a higher than normal incidence of perivalvular reflux (regurgitation around the valve) - and I wonder if this might be due to the surrounding tissue being inhibited from attaching to the sewing ring in a desirable way.

Another example. ATS seems to have leaflets that don't open all the way (particularly in smaller sizes) relative to other valves, and appear to have a higher mean gradient across the valve than On-X. However, the flip side here is that those leaflets seem to prevent backflow (transvalvular reflux) better than the On-X valve. So it appears there is a trade-off between gradient and reflux.

The SSE studies submitted for each valve to the FDA seem to favor slightly On-X for early mortality and favor ATS slightly for explant and reop. But I could probably find a study to support almost any viewpoint on these valves

The lesson I learned from all of this is that when you get to this level of comparative analysis between the studies, what becomes most obvious is that individual differences in patients/surgeon/centers probably accounts for more variability than the valves themselves.

One practical consideration is that, with the On-X valve, there is the prospect of switching to lowered ACT or to aspirin/Plavix in the future. From what I gather, if this bears fruit, the same prospect would likely exist for similar valves, but perhaps with a longer delay.

I have decided, in part for logistical reasons, to go with the ATS valve for myself. I think On-X would be a good choice as well. But since I couldn't try them each out first (thank goodness), I had to just pick one.

Hope this is useful to someone.

Now I'm just trying to get the thing scheduled!

Many thanks to all, particularly Norm, but also significantly to many others, who helped guide me through this process. There is a lot of wisdom on this board and a lot of people with good hearts

pem

 

[ALCapshaw2]

PEM -

HUH? Chemicals in the sewing ring to prevent pannus tissue growth?

I think you need to go back and review your source material for a better understanding of how the On-X valve works. It is my understanding that the On-X valves have a barrier that *******/prevents pannus tissue growth from impinging the leaflets. To the best of my knowledge, On-X is the only valve manufacturer with such a barrier to ****** pannus tissue.

You seem to have missed a MAJOR point about the limited leaflet opening of the ATS valves.
The Less the Opening angle, the GREATER the TURBULENCE in the output flow.
Turbulence can cause eddy-currents which can allow clots to form, especially in the Mitral Valve Position, due to lower velocity through the MV compared with the higher velocity through the Aortic Valve.

 

[pem]

AL,

I went back to check and I can't find any information to explain my assertion that there are "chemicals in the sewing ring". Maybe I'm confusing the On-X with a different valve on that specific dimension. I've been reading so much lately on this stuff that I fear I may have overloaded myself and mixed up some things. I apologize - the last thing I want to do is spread misinformation. From what I can tell, the On-X avoids pannus growth through a physical design that flares outward where other valves don't and this seems to stave the ingrowth of tissue. Does that sound right to you?

I still believe the conclusions I've drawn, that error notwithstanding. I have yet to see a study to suggest that there is any clinically significant outcome related to the limited leaflet opening of the ATS valves. Also, it isn't clear that there is greater turbulence in the output flow. A smaller opening with the same pressure would produce a higher velocity, and indeed ATS seem to have a higher mean gradient than On-X, but it isn't clear to me that that produces more turbulence. Sometimes I think these things get oversimplified, resulting in conclusions that perhaps don't consider all of the information. The Aoyagi paper typically cited by the On-X folks (http://ats.ctsnetjournals.org/cgi/reprint/82/3/853) explains that the ATS valve leaflets do not open as wide as stated by the ATS documentation. The conclusion from this study is that if you are a cardiologist who is trying to decide whether or not there is an obstruction present (e.g., pannus) on the basis of how wide the valve is opening, it is important to realize that they naturally do not open as wide as suggested by the literature. Knowing this avoids mistakenly diagnosing an obstruction when it is just normal valve behavior for the ATS valve. I found no suggestion in this article that there is anything problematic about the reduced opening angle. But if you know otherwise, please point me to a reference, as I would rather not get a valve that will likely be problematic.

One thing that encouraged me about ATS is a 15-year study (http://jtcs.ctsnetjournals.org/cgi/content/abstract/139/6/1494) that concludes:
"Few prosthetic valve–related complications were seen with ATS heart valve replacements in this study, and the follow-up results were favorable. The international normalized ratio was maintained in the range 1.6 to 2.0 in patients with aortic valve replacement in sinus rhythm. Not only bleeding events, seen at a rate of 0.19%/pt-y, but also thromboembolic events, at 0.44%/pt-y, were low when compared with conventional mechanical valves. Prosthetic valve noise is low, and this appears to be an excellent mechanical valve from the quality of life standpoint. The ATS valve has an excellent safety profile when compared with other mechanical valves."

Anyway, thanks for catching my mistake!
pem

 

[normofthenorth]

And it looks as if more ATS patients are fit, healthy, and symptom-free post-op!

And it looks as if more ATS patients are fit, healthy, and symptom-free post-op!

Thanks for the thanks, pem!

I think it's also worth mentioning that the US FDA approval for the two valves left behind some interesting statistics in the form of "SSE documents" (SSE = Summary of Safety and Effectiveness), which pem discovered about a week ago. Since the FDA specifies relatively strict protocols for these SSEs, one would expect the results to be reasonably comparable to each other. The key document for the ATS mech valve is http://www.accessdata.fda.gov/cdrh_docs/pdf/P990046b.pdf , and for the On-X, it's http://www.accessdata.fda.gov/cdrh_docs/pdf/P000037b.pdf . (In each case, the link points to the Summary of the SSE docs.)

As pem discovered, the SSE for the ATS presents 4 years of data on the general CV health of the recipients (NYHA Class, I-IV), while the SSE for the On-X present 3 years (so we've got 3 years of comparable data). In the ATS summary, it's Table 8 on p. 13; In the On-X summary, it's Table 5 on p. 14. In both cases, the table is entitled "Effectiveness Outcomes, Functional New York Heart (NYHA) Classification".

Also, in each document, an earlier table presents the PRE-op NYHA "mix" of each patient group, and the two pre-op groups seem very similar. But the results after 1 year, 2 years, and 3 years are NOT that similar! Specifically, the ATS patients are overwhelmingly in the (normal, asymptomatic) class I at each anniversary, while a much larger minority of the On-X patients are in Class II or even worse!

(I keep failing to be able to cut and paste the charts here, but you can see them both by using the two links above.)

Like a careful shopper, pem has been asking both companies to comment on the results. At least so far, the responses from On-X's experts don't come close to explaining away the differences, IMHO. Basically, their main expert has said that the NYHA classifications are subjective and arbitrary. There's a germ of truth in there, but I don't think they explain away these very significant post-op differences -- maybe least of all given that the pre-op results (using the same classification system) was NOT significantly different.

It is true that the On-X seems to have slightly better hemodynamic performance, and it's possible that the difference would matter to a patient with an unusually small AV. But overall, any hemodynamic deficiency that MATTERS should show up as a change in patient well-being and lack of symptoms (i.e., NYHA Classification), and the overall results there strongly favor the ATS.

 

[normofthenorth]

And the charts themselves (I hope!)

And the charts themselves (I hope!)

OK, I THINK I can do this:
The ATS chart is here:

and the On-X chart is here:
.

NYHA Class I is the best, normal healthy, no unusual CV symptoms. The other classes get gradually worse, in order.

If there really was a bias in the way the two sets of patients were classified post-op, I'd expect it to show up in the Pre-op numbers as well as the Post-op. But the ATS patients actually show up in WORSE classifications than the On-X patients pre-op, then are put into BETTER classifications post-op. So this difference cannot be explained by a systematic difference in "grading" between the two studies.

This looks to me like it's close to the "bottom line" of valve performance in the first few years, and everything else (except long-term performance) is just a contributor to these results. I.e., IF the On-X patients ended up healthier and fitter, then we'd look elsewhere for the explanation for that superiority -- superior hemodynamics, or less turbulence, or "magic carbon", or the special geometry that prevents pannus, etc., etc.

But if On-X-valve recipients end up LESS healthy and fit than ATS-valve recipients (as seems to be the case from these numbers), then EITHER (a) those things are overrated/overstated, AND/OR (b) their positive influence is being overwhelmed by some relative superiority of the ATS valve. I have trouble imagining another explanation.

Other views are welcome, of course! (Try and STOP 'em! )

 

[pem]

If there really was a bias in the way the two sets of patients were classified post-op, I'd expect it to show up in the Pre-op numbers as well as the Post-op.

Norm - This is an excellent point that I had completely missed - thanks.

By the way, if I had an On-X valve and no symptoms I would not be concerned by this. The data are consistent with what you get in year 1 is what you get with regard to NYHA for On-X.

I think On-X valves size in a non-standard way (based on the subjective conclusions in a study I read) and that surgeons who are accustomed to other valves may not size them quite right leading to perivalvular reflux. That kind of reflux may need correction. But when I also mentioned the higher incidence of transvalvular reflux in On-X patients from a study I read, which might have more to do with valve hemodynamics (such as not shutting quickly and letting some backflow), my cardiologist was unconcerned about a little reflux. She said she has asymptomatic patients with severe insufficiency who don't require surgery because they are asymptomatic and otherwise have a healthy heart.

pem

 

[ken taylor]

I after two years of research I chose the ONX Boy Im very happy walking a mile at a time three days post surgery. You need a little scolding for posting false info. The reason onx has no panus groth is its design. Not chemicals!!!!!!!!!!!!

 

[RobThatsMe]

Hi,

As many of you know, I also choose the On-X for my 2nd surgery back in Sept.
My original St Judes Mech valve only lasted 10 years due to Pannus. So much for the valve lasting a lifetime. Although the valve itself was fine. Pannus tissue growth caused my issue.

I was informed that if you are prone to Pannus, then it will most likely occur again. Thus my decision to go with the On-X as this valve is wider than my other one, and also helps prevent, or delay the Pannus issue.

Regarding some of the comments about the stitching threads, this is what one of my surgeons told me;
The material composition of some of the earlier surgical threads used to stitch the valve in place can cause the body to reject them, the threads that is. If it does, it deveops pannus around the valve.

For now, I am doing well, and guess I can be an on-going case study for the site.


This is a great thread, and I firmly believe that each on of us needs to do the research, and make the choice that they are most comfortable with.

Rob

 

[drivetopless]

All of us On-X valvers should check back in in about 4 years.

When I was choosing valves, ATS wasn't mentioned by surgeons. My choices were St. Jude or On-X.

 

[pem]

I after two years of research I chose the ONX Boy Im very happy walking a mile at a time three days post surgery. You need a little scolding for posting false info. The reason onx has no panus groth is its design. Not chemicals!!!!!!!!!!!!

Sorry for my mistake. Someone else already pointed it out, so you may have missed my apologetic reply to that.

In any case, whether it is by chemicals or design, the benefit of no pannus growth is significant, and that quality was mentioned in support of the On-X valve. Some folks interpret "chemicals" to be bad. Only bad chemicals are bad - in sufficient quantity Chemicals pervade both mechanical and tissue valves, so a chemical modification to any part of a valve would not be inherently bad, and might well be inherently good, especially if it were done on purpose. For example, one way to get tissue valves to last longer is with the application of a chemical treatment to the source tissue. Anyway, I may have been remembering something I read about another valve that used a chemical rather than design approach to inhibit pannus growth.

I'm glad you like your On-X valve - there certainly seems to be a strong On-X following on the forum, and if my logistics were different (in terms of local surgeons and which valves they implant), I might well go with the On-X. But as it is, I think and hope the ATS will do well for me.

Best,
pem

 

[pem]

Hi,

As many of you know, I also choose the On-X for my 2nd surgery back in Sept.
My original St Judes Mech valve only lasted 10 years due to Pannus. So much for the valve lasting a lifetime. Although the valve itself was fine. Pannus tissue growth caused my issue.

I was informed that if you are prone to Pannus, then it will most likely occur again. Thus my decision to go with the On-X as this valve is wider than my other one, and also helps prevent, or delay the Pannus issue.

Regarding some of the comments about the stitching threads, this is what one of my surgeons told me;
The material composition of some of the earlier surgical threads used to stitch the valve in place can cause the body to reject them, the threads that is. If it does, it deveops pannus around the valve.

For now, I am doing well, and guess I can be an on-going case study for the site.


This is a great thread, and I firmly believe that each on of us needs to do the research, and make the choice that they are most comfortable with.

Rob

Rob,

First - I love that photo of you. It just puts me in a good mood when I look at it

So you made an interesting point, which suggests to me that some people may have more of a propensity than others to form pannus. Is that true in general? Is there no way to test for this in advance of getting a valve? Someone said they read a study suggesting that people who grow excess skin when they have scar tissue might be more prone to pannus - does anyone have a citation for this or think this might be true?

Anyway, it sounds like the On-X is working well for you. What did you think of Dr. Pettersson. He seems fantastic.

pem

 

[RobThatsMe]

Rob,

First - I love that photo of you. It just puts me in a good mood when I look at it

So you made an interesting point, which suggests to me that some people may have more of a propensity than others to form pannus. Is that true in general? Is there no way to test for this in advance of getting a valve? Someone said they read a study suggesting that people who grow excess skin when they have scar tissue might be more prone to pannus - does anyone have a citation for this or think this might be true?

Anyway, it sounds like the On-X is working well for you. What did you think of Dr. Pettersson. He seems fantastic.

pem

Hi pem,

Glad you enjoyed my pic. I took that while in Germany attending Carnival a few years ago.

I can't say enough about Dr. Pettersson. He is a surgical machine! Dr. Roselli, who studied under Dr. Pettersson, is expert on aneurysms and dissections. They both worked on me during my surgery. (13.5 hrs in surgery... ugh!!!) Dr. P worked on the aortic root, graft, and valve. Dr. R worked on my aneurysm and dissection. He bipassed the caratid, (to move it from the area of the aneurysm to a more stable portion of the aorta, coiled the aneurysm, and then placed a stent in the aorta with a 22 cm of Dacron tube to help support my dissection. I deffinately had the "Surgical Dream Team" working on me.

Rob

 

[pem]

Hi pem,

Glad you enjoyed my pic. I took that while in Germany attending Carnival a few years ago.

I can't say enough about Dr. Pettersson. He is a surgical machine! Dr. Roselli, who studied under Dr. Pettersson, is expert on aneurysms and dissections. They both worked on me during my surgery. (13.5 hrs in surgery... ugh!!!) Dr. P worked on the aortic root, graft, and valve. Dr. R worked on my aneurysm and dissection. He bipassed the caratid, (to move it from the area of the aneurysm to a more stable portion of the aorta, coiled the aneurysm, and then placed a stent in the aorta with a 22 cm of Dacron tube to help support my dissection. I deffinately had the "Surgical Dream Team" working on me.

Rob

Truly amazing - I think it's those complicated cases that Dr. Pettersson thrives on, and part of what gives Cleveland Clinic its outstanding reputation.