Making a tissue valve last longer

[ottagal]

More interesting stuff. It seems strange that the abstract seems to make no mention of the mix of types of tissue valves, which many of us are understandably curious about.

Also, this study is "age-specific" only in the same imprecise, large-tranche (big-basket) way as the new article on Medtronic Hancock II (pig) aortic valve longevity that I've been mentioning -- i.e., they give results for only 2 or 3 big "baskets" of patient ages. That's not very meaningful to a patient, really. E.g., if you're 39 and they give you the overall results for the "under-40" group, you can be pretty sure you're not an average member of that group, so the median numbers don't apply to you directly. But it takes more than a little counting on fingers and toes to figure out what your own best-guess numbers are. (The Hancock II study abstract is at ats.ctsnetjournals.org/cgi/content/abstract/90/3/775? .)

I would THINK -- having forgotten most of the statistics I ever learned -- that it would be relatively straightforward for a fancy statistician (or a good piece of software) to invert the data, to present (e.g.) the % confidence of being SVD-free at 5, 7, 9, 11. . . years, for each year of age (or each small age "slice") at surgery. Or the number of years post-op to reach 75% and 50% confidence of being SVD-free for each year of age (or each small age "slice") at surgery. I think that kind of presentation would require more "smoothing" and interpolation than what they presented (and the error bands might well expand as the age tranches shrank), but I also think it would be much more directly meaningful to any patient. Heck, we each have a specific age, and we each know it; what we DON'T know is how long we can expect a tissue valve to last, given the evidence to date! That sounds exactly like the question they set out to answer -- as they said, "the median durability of bioprostheses in younger adults. . . is important for young patients who may choose a bioprosthesis and for their physicians, thus forming the basis for the present study." I certainly don't find their abstract (or the data presentation in the otherwise impressive Hancock II study) to be responsive to that need.

Another weakness in this study -- which seems to be a "poster session" paper from a conference, rather than a formally peer-reviewed publication, at least so far -- is that it presents "Freedom from [Aortic or Mitral] Valve Reoperation" as the key variable, apparently equating it with valve "durability". As the Hancock II study points out, those freedom from Reoperation numbers almost always overstate valve durability, because some patients with failed valves are not suitable candidates for surgery. In effect, they represent failures, but they show up in the "success" column! In that study, they presented the data both ways -- e.g., they documented Structural Valve Deterioration (SVD) in 87 patients (of 1134), but only 74 underwent reoperation, since 13 were inoperable. (Once the difference is pointed out, you can't ever ignore it again!)

I initially found the graphs under the Abstract almost illegible. But when I right-clicked on the graphic and opened it in a separate page (then expanded it), it was much clearer. I'm sure that saving it on your computer, then opening it with a good image viewer, would also help.

Thanks for the very astute observations and feedback. Certainly doesn't make our decision making any easier does it!

 

[Lily]

I'm wondering if there are things a patient can do to extend the life of a tissue valve replacement, such as certain exercises, or supplements, or maybe not working out quite so much?

Shortly after my valve replacement, I asked my cardio how I could get the longest possible time out of my tissue valve and his reply was that it was very important for me to take very good care of teeth and gums.

 

[67walkon]

An echo today showed my valve opening is down to 1.7 cm squared. It is barely 3.5 years old. Is this normal?

 

[Lynlw]

An echo today showed my valve opening is down to 1.7 cm squared. It is barely 3.5 years old. Is this normal?

What was it the other post op echos?

 

[normofthenorth]

67walkon, my AV opening is smaller than that, and my valve is about a WEEK old! As Lyn suggests, the key question is if it's dropping (fast), not what size it is, as long as it's substantially bigger than ~1 cm2.

 

[JeffM]

I agree that conventional wisdom says that beta blockers do not help the valve itself, but I have to believe that reducing (via slower heart rate from beta blockade) the number of times the valve is put under pressure via systole would be beneficial. If I concentrate the stream of my power washer on one small area on my deck, eventually the fibers of the deck will disintegrate. I may even be able to blow a hole in the deck if I stand there long enough spraying the same spot. IF I reduced the pressure/frequency of my power washing, perhaps I could extend the life of my deck... no?

Also, you may find that your fatigue is worse when you stop taking the beta blockers. If that's the case you should consider going back on them. Listen carefully to your body. There are other BB's out there now that may have a more tolerable side effect profile.

On the other hand, it be reasonable to assume that with muscle tissue, unlike deck fibers, there is live tissue, which responds to hard work by getting stronger. Obviously, there's a point where too much pressure in one place is detrimental. But if a healthy heart is limited by a betablocker in it's ability to perform difficult tasks, I wonder if the heart (not just the valve), lungs, vascular and muscular systems will be able to increase their capacity to do more work compared those systems working without the limitations of a betablocker? If the answer is yes, then it's important to consider more than how a beta blocker would effect the just bioprostheitc valve. And I would think that the more one can do to improve fitness, the less stressful the conditions will be when the valve is operating 24/7. My own experience with being on a beta blocker for several months was that it significantly impeded my ability to exercise at a high level. I suppose if one doesn't or can't exercise, then whatever assistance can be offered through drug intervention would be beneficial both short and long term. I would think that would include both BP as well as heart rate controlling drugs.

 

[67walkon]

Thank you both. My other post surgery echo reports don't give me the actual size, just all the other info. I don't actually have this report yet. I asked the tech what size it was and he told me 1.7 and commented that the tissue valves seem to have some stenosis right out of the box. I can't find any internet info on what size a tissue valve opening should be, but the description of the size of the valve was 25 mm. That could mean the whole thing is 25 mm (2.5cm) or that the opening was 25 mm or it could mean something totally different.

My actual doctor appointment is Dec 21. I tend to stress over these heart related issues.

Hopefully, it won't be anything to worry about.

 

[tobagotwo]

The abstract states that the study begins with valves implanted "after 1976" (at that time, they were barely-treated pork). Newer technology valves were still two decades away.

While it would be useful to have an age-focused study to help with these decisions, this particular data is not of reliable value for ascertaining useful life of current or even recent valves. The types of valves are mixed and unidentified (other than "stented"), and the antique manufacturing dates of an unknown percentage of the valves make them unrepresentative of the uncompressed, anti-calcification-treated valves in use now.

Beta blockers are like buckshot. They work by combining with chemicals found in the body to keep those chemicals from reacting with other chemicals. Mainly, they are intended to block beta receptors in the heart, causing the muscle to be less responsive to nerve impulses. The effect on the heart muscle (and to some extent other muscles) is to weaken its effectiveness during contraction. This creates a "softer" heartbeat, which lowers blood pressure and is less likely to be overstimulated into arrhythmias.

Unfortunately, they are not specific enough to avoid interfering with other bodily chemical reactions in the process. As a result, they can do a lot of other things to the body as well as keep the blood pressure in check. In many people they have no noticeable effect. However, in others they can cause muscle weakness, fatigue, psoriasis, diabetes, GERD and other disorders, depending on the person's internal chemistry.

While a case could be made that a less forceful heartbeat might let a tissue valve last longer, it's never been shown to be the case in a study. If beta blocker manufacturers thought they could sell more beta blockers, they'd be all over that, like Lipitor and Vytorin in their very large, expensive, and spectacularly unsuccessful attempts to show that statins and other anticholesterol drugs would keep valves from calcifying, or at least slow the process down (as you have guessed, they do not).

Best wishes,

 

[normofthenorth]

67walkon, the 25mm size of your valve is a linear dimension, I think, like radius or diameter. And it's more a rating than a consistently measured size, because different manufacturers measure differently, like inside vs. outside. But the 1.7 (and my 1.26!) is an AREA, in sq. cm. I haven't played with Pi-R-Squared enough yet to figure out what the 25mm must be, but comparing those two numbers is definitely trickier than what you're doing.

OTOH, if you have "all the other info" from Echo measurements of your valve post-op -- especially the pressure drop across the valve -- several of those are directly (OK, more like inversely) related to the effective area, so they could help you see if there's a trend or not. A smaller effective area goes with a higher pressure drop, and vice versa. In stenosis, I think 1.0 cm2 eff. area corresponds to something like 90 mmHg pressure. My calculated AV area of 1.26 cm2 corresponds to an AV peak (pressure) gradient of 25mmHg and AV MEAN (pressure) gradient of 14mmHg.

I think "Stenosis out of the box" is an unnecessarily depressing way to describe less-than-perfect hemodynamics in a new, durable, and otherwise beautifully functioning tissue valve! E.g., REAL stenosis tends to be a slippery slope, a progressive deterioration that goes more exponentially ("tipping point") than linearly. But any effective area that's "missing" from a new tissue valve (like my Hancock II) because the stent takes up some space, etc., does NOT seem to "attract" new calcium-based deposits of the sort that cause biological stenosis. The full-sized opening is definitely smaller than it would be if the valve magically disappeared on every heart-beat, but it's not diseased or on its way out, so we don't really have stenosis!

 

[tobagotwo]

Two comments on stenosis out of the box...

According to several surgeons, tissue valves tend to "loosen up" a little bit when they start getting used, so they sometimes start out tighter than they are after they've unkinked.

If they are the type that are mounted above the "notch" (such as a Carpentier-Edwards Perimount Magna), the stent is "hidden" behind the notch, so they have the same effective opening as an unstented valve, but retain the structural advantages of a stent. Mechanical valves also use this mounting technique to advantage the valve of every millimeter of opening. They tend to keep a lower transvalvular pressure.

The pressure of the blood flowing through the valve is the primary determiner of stenosis, although the meaning of the word is defined by size (stenosis is the narrowing of a passage). Even though I first received a valve that didn't pan out, and actually did have some stenosis out of the box, the relief for my heart was so great that it reverted to normal size in a very short timespan. That means that the stress on the heart had to be trivial, or it wouldn't have remodeled so quickly and thoroughly.

Another notation is that there is no length-of-survival difference shown between the types of valves. If the tissue valves were detrimentally stenotic, that effect would show up over time.

Best wishes,

 

[normofthenorth]

Thanks, Bob, I could feel my chest loosening up as I was reading your note about the valve loosening up!

Do you know if that above-the-notch or behind-the-notch mounting is what the fancy experts call supra-annular mounting rather than intra-annular mounting? I've never understood what it really means, not having a crystal-clear mental image of the detailed geometry of the things. And the Hancock II is NOT mounted above the notch or behind the notch (or maybe supra-annular), which may be why its hemodynamics seem ~12% worse than the CEP in that case-controlled trial that my surgeon co-authored?

 

[67walkon]

Good news! The current echo shows no changes from the previous ones. Every thing is working great. I saw a different cardiologist in the same group this time. He says there are no restrictions on exercise or heart rate or anything like that. He commented that there is no real data on how long these treated bovine valves are going to last and that it could go another 15 years or so.

It's amazing how a little good news from a heart doctor can brighten up ones day!

 

[Lily]

Nice to read

 

[Lynlw]

Thankls for the update. You must be so relieved, now you can go into the Holidays without that worry hanging over you.

 

[Jkm7]

Good news. Very happy to hear it.

 

[Bean Counter]

That is good news!

 

[Kathy McCain]

H2o ?? My cardios office told me to keep myself well hydrated . Drink lots of this stuff. I do, most of the time.