An On-X question

[Susan BAV]

I have a question about the On-X valves and anticoagulation (ACT) therapy.

One reason why these valves are of interest to people is because of the advertised studies in regard to the company's hopes of patients needing no anticoagulation therapy and/or reduced anticoagulation therapy. I have no knowledge or opinion of how these studies may be going.

But I was wondering about the anticoagulation (ACT) therapy. Why might it be preferred to take lower dosages of ACT? Is it more dangerous to have to take higher dosages of ACT? And if so, in what way?

And if it is not more dangerous to have to take a higher dosage of ACT, I thought I understood that a lot of the potential problems with ACT were related to staying within range and/or ACT mismanagement by medical professionals. Even with the possibility of reduced ACT, isn't the problem of staying within range still a potential problem, as well as mismanagement?

 

[Karlynn]

I think it's confusing too Susan and you're right - it's not the dose - it's the INR. I've always thought they should have worded it as Low-INR Target Range. "Low Dose" is very confusing. My range is 2.5 - 3.5 It would be a benefit if an On-X mitral valve didn't require as high a target range for me. That in turn would mean I wouldn't have to take as much Coumadin, which really isn't a big deal one way or the other since it's the INR that's the important thing and there is no increased toxicity issue with a higher dose regimine. The benefit would be having a safe valve at a lower INR (closer to normal clotting time).

 

[dick0236]

Susan, very good question. My guess is that the On-x is designed to reduce throwing off clots while requiring a lower INR. A lower INR should be easier to maintain, making it a "win-win". I am sure that Al Cap and others can shed light on this.

 

[SteveInFlorida]

I have an On-X valve and am a participant in the study in question.

My basic understanding is that the chief benefit of the study will be if it demonstrates that those having an On-X valve are generally at lower risk of clots forming, which is the general hypothesis behind the study but remains to be seen.

In any case, having a lower target INR as a participant in the study presumably lowers one's risk somewhat of suffering a bleeding problem, due to the reduced dosage of anti-coagulant, whether or not it is increasing one's risk of having a clot as would normally be expected with a mechanical valve.

Confusing it is, to be sure!

 

[Ross]

In any case, having a lower target INR as a participant in the study presumably lowers one's risk somewhat of suffering a bleeding problem, due to the reduced dosage of anti-coagulant, whether or not it is increasing one's risk of having a clot as would normally be expected with a mechanical valve.

Confusing it is, to be sure!

Yeah but the INR is what matters, not what a dose a person takes. You might get away with 35mg a week and someone else may require 70mg a week to maintain lets say a 2.0 INR.

I think the actual long term goal is to prove it's worthy of no anticoagulation drugs or asprin at a minimum.

 

[ALCapshaw2]

If you did not have to maintain as high an INR, then you would be at less risk of a brain bleed in case you got hit on the head. You would also be in less danger of bleeding if you were to unwittingly ingest something (such as a large amount of licorice) that interacted with coumadin and caused your INR to rise. And if the valve was less likely to trigger clot formation in the first place, then you would be at less risk when you had to stop your coumadin for an invasive medical procedure.

WELL SAID !

The last part is especially important to understand.

Bottom Line:

Lower INR = Lower Risk of a BLEED

On-X design Improvements* = Lower Risk of Clot Formation compared with older Mechanical Valve Designs (at all levels of anti-coagulation, including NONE).

*On-X Design Improvements include:

1 - Full 90 degree opening of leaflets for less turbulence
(vs. 75 to 85 degrees for older mechanical valve designs)

2 - Smoother, Harder, Stronger Pyrolytic Carbon Leaflets
created by Jack Bokros, Ph.D., who also created the
Pyrolytic Carbon leaflets used in older valve designs.
Smoother surface = Less chance of clot forming.

3 - Improved Pivot Design for reduced damage to Blood
Cells (comparable to tissue valves) vs. higher level of
Hemolysis (Damage to Red Blood Cells) typical of
older mechanical valve designs. Hemolysis is a known
cause of anemia.

4 - Barrier to retard Pannus Tissue Growth which is known
to interfere with leaflet movement in both older
mechanical valve designs and tissue valves
(as experienced and reported by some members of VR.com)

This is *my* non-professional understanding of some of the design improvements included in the On-X Valves.

See www.onxvalves.com for more details and supporting documentation, or contact the company at 888-339-8000.

'AL Capshaw'

 

[Karlynn]

I think the confusion that Susan was referring to is the reference to the "no dose - low dose" trials and the reference to the On-X's potential to require no Coumadin or "low dose" Coumadin. It's the "low dose" that messes people up because there is no set dose to achieve any particular INR. It's the "low INR" that would be advantageous and the dose required for that target INR will be different for each person.

 

[Bina]

I am one of those few who maintains an INR of 2.8 with a "low" dose of 19 mgs per week.
Wow, imagine if my target INR was much lower....

 

[andrewg]

Being in the Plavix/aspirin group of the On-X study, I no longer have to do any monitoring.

When initially deciding whether to participate in the study, my surgeon suggested that the valve had wide usage and acceptance in South Africa and I believe Germany, and that most of the South African users used just aspirin.

 

[ALCapshaw2]

I think the confusion that Susan was referring to is the reference to the "no dose - low dose" trials and the reference to the On-X's potential to require no Coumadin or "low dose" Coumadin. It's the "low dose" that messes people up because there is no set dose to achieve any particular INR. It's the "low INR" that would be advantageous and the dose required for that target INR will be different for each person.

WELL SAID Karlynn !

In the memo outlining the Medicare Decision to approve Home Monitoring for Long Term Anti-Coagulation patients, there is a paragraph that addresses Bleeding Risk vs. INR.

It states that for an INR of 4.0, the Bleeding Risk is 2X that of a patient whose INR is under 3.0

It also states that for an INR of 6.0, the Bleeding Risk is 7X that of a patient whose INR is under 3.0

It further adds that the STOKE RISK rises Rapidly for an INR Under 2.0

The Bleeding Risk and Stroke Risk curves intersect around an INR of 2.5 which represents the INR for "Minimum Combined Risk" (from another source - I think it was St. Jude Medical) hence the usual recommendation for maintaining an INR between 2.0 and 3.0 for patients not at elevated risk of stroke.

Patients with an elevated risk of Stroke (including Mitral Valve Patients) are advised to maintain a higher INR, typically 2.5 to 3.5 but sometimes even 3.0 to 4.0

As others have said, INR is the KEY, NOT Dose.
INR follows Dose, but Dose is dependent on the individual.

'AL Capshaw'

 

[SHEEPDOG]

It is sort of like "BLOODTHINNERS"

It is sort of like "BLOODTHINNERS"

The issue is in the COMMONLY accepted words for certain things. Although ANTICOAGULANTS don't THIN the blood, the whole world knows Coumadin as a BLOODTHINNER. It is a commonly accepted MISNOMER that carries with it some negative connotations for the un/under educated (including some of those in the Medical Community) Lo INR would be right. It is good to see people trying to educate themselves. Now, what do we do about the DOCTORS?

 

[Susan BAV]

...As others have said, INR is the KEY, NOT Dose.
INR follows Dose, but Dose is dependent on the individual...

Even with the possibility of reduced ACT -- or rather reduced INR target -- isn't the possible problem of staying within range still the same potential problem?

Or another way to ask it, is it easier to maintain a lower INR than it is to maintain a higher INR, in terms of numbers; or rather, is it a similar issue, with similar diligence required in staying within a specific range?

Or might it be more difficult to remain in range with a lower INR because simple things (and the recent licorice thread is a good example of that) might make it bump out of this lower range more easily?

 

[Karlynn]

I don't see that it affects the ability to stay in range. The problem that I see occurring with "staying in range" isn't the ability to do so, but the narrow ranges that some doctors seem to be setting with the On-X. A .5 range is just too narrow. Many people still treat INR as an exact science, never acknowledging the +/- .3 variance. They see INR as shooting baskets - you have to get the ball in to get a point. When in actuality it's more like a game of darts where you score for being in the area.

Many of us that have been on "the stuff" for a while really don't get wigged out for anything from 2 - 5. We may tweak our dose a little, but we don't look on it as a problem - just a fact of life - much like a diabetic that adjusts their insulin dose.

 

[ALCapshaw2]

Even with the possibility of reduced ACT -- or rather reduced INR target -- isn't the possible problem of staying within range still the same potential problem?

Or another way to ask it, is it easier to maintain a lower INR than it is to maintain a higher INR, in terms of numbers; or rather, is it a similar issue, with similar diligence required in staying within a specific range?

Or might it be more difficult to remain in range with a lower INR because simple things (and the recent licorice thread is a good example of that) might make it bump out of this lower range more easily?

It comes down to assessing the RISKS.

The Risk of Bleeding goes UP with higher INR.
Therefore a Lower INR (target) Range has a Wider Margin of Safety than for a patient on a higher (target) range.

The Risk of STROKE is Lower for the On-X valve because it addresses several of the Causes for Clot Formation, again providing a Wider Margin of Safety.

Another way of looking at this is that for a given (constant) RISK Factor, the On-X Valve can tolerate a Wider Range of INR Values (and therefore it is easier to maintain a SAFE Range.)

That is why I view the On-X valves as being a Win-Win choice over the Older Mechanical Valve Designs.

'AL Capshaw'

 

[Susan BAV]

Brainstorming a little more in regard to the reduced INR target made me wonder...

Since reading about the On-X valve, and more particularly about the African tribe study including the 40% with erratic anticoagulation coverage as posted below, I have wondered if there could have been, perhaps unbeknownst to researchers, regularly consumed and unique foods in their indigenous tribal diet which could have measurably (or rather, unmeasurably) contributed to some state of anticoagulation, considering what we've been reminded of in the past week in regard to innocuous-sounding foods, which evidently increase the INR, such as black licorice.

This also crossed my mind because of something I saw years ago, a documentary on television which chronicled the lives of a tribe in Africa for a year. For some unknown reason, according to the chroniclers, the death rate for infants under one (or two years) was extremely high. As I watched the show, it occurred to me what very well might have been the cause of the high infant death rate. One of the biggest highlights during the year for the tribe was to find a honey-filled tree and to consume the fresh honey straight from the tree, the entire tribe including the infants. I also recalled reading, as a young mother, that babies under one or two should never be given unprocessed/unpasteurized honey because of a very dangerous and potentially fatal intestinal bug. So it occurred to me that this could possibly have been at least part of the cause of the high infant mortality among that tribe, something which evidently hadn't occurred to the researchers.

Anyway, below is some info on the indigenous tribe study in Africa:

1: J Heart Valve Dis. 2006 Jan;15(1):80-6. Links
The On-X heart valve: mid-term results in a poorly anticoagulated population.
Williams MA, van Riet S.
Provincial Hospital, Port Elizabeth, South Africa. [email protected]

BACKGROUND AND AIM OF THE STUDY: The study aim was to evaluate the clinical performance of the On-X heart valve in a socioeconomically disadvantaged population. Most patients were from an indigenous, poorly educated and geographically dispersed segment of the population where anticoagulation therapy was generally erratic. METHODS: Between 1999 and 2004, a total of 530 valves (242 mitral valves, 104 aortic valves, 92 double valves) was implanted in 438 patients (average age 33 years; range: 3-78 years). The most common reason for surgery was rheumatic valve disease (57%), followed by degenerative valve disease (11%) and infective endocarditis (9%). Follow up was 95% complete for a total of 746 patient-years (pt-yr). Among the patient population, 40% were either not anticoagulated or were unsatisfactorily anticoagulated. RESULTS: Hospital mortality was 2.3%, and none of the hospital deaths was valve-related. Mean (+/- SE) actuarial survival (including hospital deaths) at four years was: AVR 73.8 +/- 8.1%, MVR 83.4 +/- 5.7% and DVR 60.9 +/- 10.3%. Linearized rates (for AVR, MVR and DVR, respectively) for late complications (%/ pt-yr) were: bleeding events 0.6, 1.0, and 2.3; thrombosis 0.0, 0.2, and 0.0; endocarditis 0.6, 1.0, and 2.3; paravalvular leak 0.6, 0.2, and 0.0; systemic embolism 1.1, 1.5, and 3.5. Most systemic emboli were related to infective endocarditis. Among patients there were seven uncomplicated, full-term pregnancies. CONCLUSION: Bearing in mind the erratic anticoagulation coverage and high incidence of infective endocarditis, the results of this study may be regarded as encouraging. The low incidence of valve thrombosis (one case) was noteworthy. These data also suggest that the On-X valve may be implanted with relative safety in women wishing to have children.

PMID: 16480016 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov/pubmed/16480016

 

[R&N Brown]

I had an On-X valve installed and I am part of the study as well.

My reasoning for choosing the On-X was based on the possibility that I would one day be free of Coumidin and the constant blood-letting involved with taking it.

With any other mechanical valve you are assured that if you follow Doctors orders you are tied to the ACT medical community for life, period.

AndrewG is a participant here and is a great example of how a combination of Plavix and Aspirin work with this valve. (Sorry to drag you in here Andrew, your one of my heros right now with this study thing!) I am hoping to be put in that same finger of the study when that time comes. (2 months from now) Even if I am not chosen right off, the possibility exists that I will be transferred to what I see as the preferred group at some point in the future.

In no way am I disillusioned in thinking that the bleeding issues go away with Plavix/Aspirin, although, I see it as a more stable treatment.

I've never been a negative person, but I am just now seeing firsthand how some of the prescribers have little clue as to what they are doing.

Rob