Mechanical Valve for an Oversized Aortic Annulus

[chaconne]

I just had my aortic valve replaced on Monday (11/7), with an On-X 27/29mm. I was told that my aortic annulus was 36mm and could've supported the largest valve size, (machanical) the 33mm with St. Jude. The surgeon said he decided to use the smaller On-x because I had been insistent on it and he thought it would be OK.

My questions are:
- Does anyone else here have a large valve, or had an annulus that had to be streched to fit a smaller valve?
- Are there any common long-term problems associated with under-sizing a valve?
- Does my 36mm annulus mean that my new valve has a smaller effective opening than the old one? (It was a regurgitating BAV, not stenosis)
- What does the On-x size 27/29 mean? it 1t 27 or 29 mm?
- Is this measurement the inside diameter of the valve?

That said, I am recovering very well, an all indications show that I will do well. I guess one of my concerns is that I won't have the exercise power I had before surgery due to a smaller than optimal valve.

Any info would be appreciated

 

[chaconne]

I take it from the lack of responses that I'm in a tiny minority and may be the first on this site to deal with these issues (on 1 study in India, I saw that only 1% of valve replacement patents required a 31mm St. Jude)

I will pursue the answers to my first 3 questions in the coming months, however, I found possible answers to the last 2, which I will post in case it's helpful to anyone:

-The On-X 27/29mm size is basically the same valve as the 25mm On-X, but with a larger cuff
-These measurements refer to the ideal aortic annulus size to use for the valve.

The internal opening of the 25/27/29mm On-X is 23.4mm 26.4mm flare. The largest St. Jude Masters, at 31/33mm, 26mm internal opening. This means my On-X is about 80% of the area of the St Jude. Hopefully this will not cause me performance problems in the future.

 

[Lynlw]

Sorry You didnt get any responses, i didn't remeber anyone having that before. i guess alot would depend on whay your measurements are, how the gradient is,left ventricle size etc, not even right now , but in a few weeks /months when your heart heals things find their new 'normal"

the only thing I know about with smaller valves than you could fit - I do NOT know if this pertains to case like yours or not---- would be what is call prosthetic valve mismatch there are many articles about that https://www.google.com/search?client=gmail&rls=gm&q=prosthetic valve mismatch
I would tend to think this wouldn't be somethig that applies to you or the surgeon wouldn't have used the valve he did just because you asked for a certain brand..most surgeons we've spoke to over the years say they will take our preferences in mind, but until they had him opened and could really see whats going on they couldn't make any promises and would do whatever they felt would work best for him.


Interestingly Justin's heart and its part are pretty big, his last pulm valve/conduit was a 28/29. but Ive wonderred what they would do if they didntt have part large enough to fit, I thought if it wasn't something like the conduit or graft they could make in the OR (and have done several times for him) I thought maybe they would hope they could find a human donor valve /artery larger than manufactured ones.

 

[chaconne]

Thanks for the post Lyn.

It sounds like you have a vast amount of experience with all the things that have happened to your son.

I'm hoping my heart adapts to the new valve and doesn't slow me down!

Blessings,
-Steve

 

[AgilityDog]

All I know is I got a HUGE 31mm St Jude's in the mitral position, because my valve was flapping in the breeze and the atrium enlarged 40%. Of course, now that my heart has remodeled, I'll bet you could fit a smaller valve there and it would fit well.
My aortic On-x is 19 mm. So make of that what you will.

Oh look! I just realized I'm one of the top 1% in SOMETHING! (chuckle)

 

[Bill B]

The question about long-term problems with undersized valves requires a professional interpretation. Although there is a lot of literature about problems with patient-prosthesis size maimatch, you have a paticular situation that may not apply. You received a LARGE valve. And the mismatch issue has more to do with LV size and total body mass than the size of the annulus. I would think you will have a low transvalve gradient and good function - that's what is important. I would go over this with your cardiologist or surgeon at the next visit, but I think if the gradient is low, the mismatch is inconsequential.

 

[Julian]

Hmmm... I'd be worried as well concerned that I would be permanently robbed blood because of a smaller funnel. Something tells me that after a certain size the difference in output gets smaller and smaller. Like for example the larger St. Jude has 20% larger orifice but how much of the 20% is really utilized or even noticed? I would be pretty confident that after a certain point larger isn't better after a point. I know pressure gradients are lower on the larger sizes but when does the math switch around? I'm probably not making sense or know what the hell I'm talking about, I'm basically just rambling but in the end something tells me your valve is going to be more than enough.

 

[chaconne]

Hmmm... I'd be worried as well concerned that I would be permanently robbed blood because of a smaller funnel. Something tells me that after a certain size the difference in output gets smaller and smaller. Like for example the larger St. Jude has 20% larger orifice but how much of the 20% is really utilized or even noticed? I would be pretty confident that after a certain point larger isn't better after a point. I know pressure gradients are lower on the larger sizes but when does the math switch around? I'm probably not making sense or know what the hell I'm talking about, I'm basically just rambling but in the end something tells me your valve is going to be more than enough.

Yeah, I think there is something to be said about the law of diminishing returns.

From what I remember, my surgeon said that the main issue was whether the smaller valve would stay in place since it had to be stretched to fit. He was comfortable doing this and was confident of success.

I think Bill B's point is well taken regarding the absolute gradient being the bottom line. This quantity is the kind of thing that shows up on an echo I assume? I had an echo just before I left the hospital and no-one seemed to have said anything about it.

AgilityDog, you are in the 1% group too? It's interesting that there is such a large difference between your mitral and aortic sizes.

Thank you all for your willingness to chime in. I was impatient and wrong to assume no one had anything to say. I am a perfectionist by nature and this issue has been eating away at me (I've spend a good deal of time over the last year focused on valve selection). Your encouragements are a definite answer to prayer.

God bless,
-Steve

 

[normofthenorth]

The law of diminishing returns is in force here, but the law of the bottleneck -- "a chain is only as strong as its weakest link", or "a fluid's speed through a complex course is largely determined by the primary (tightest) bottleneck, not by the secondary and tertiary bottlenecks" -- is probably even more important.

For AVR patients with unusually small AVs for the size of their bodies (the aforementioned "prosthetic valve mismatch"), AV size may be the primary bottleneck, limiting the flow of blood through the heart. For the rest of us, we can undergo a remarkable amount of AV stenosis without ANY noticeable decrease in Cardio-Vascular performance, fitness, or output. I think my AV was measured down to around 0.8 cm2 EA -- and with regurg/insufficiency, too! -- without my noticing any CV deficit at all. (Also, if -- say -- your legs give out before your heart does, you could experience a slight decrease in cardiac output without it hurting your athletic performance.)

I suspect that any of the available (LARGE) AV choices your surgeon had would present a virtually infinite cross-sectional area to your blood flow, even when you're exercising at max intensity. If so, it's not just a small deal, a la diminishing returns, it's probably a zero.

 

[chaconne]

Norm,

As always, thanks for your thoughtful analysis. I agree that it is most likely my valve will not be anywhere near being a bottleneck. Time may tell!

 

[Lynlw]

Yeah, I think there is something to be said about the law of diminishing returns.

From what I remember, my surgeon said that the main issue was whether the smaller valve would stay in place since it had to be stretched to fit. He was comfortable doing this and was confident of success.

I think Bill B's point is well taken regarding the absolute gradient being the bottom line. This quantity is the kind of thing that shows up on an echo I assume? I had an echo just before I left the hospital and no-one seemed to have said anything about it.

AgilityDog, you are in the 1% group too? It's interesting that there is such a large difference between your mitral and aortic sizes.

Thank you all for your willingness to chime in. I was impatient and wrong to assume no one had anything to say. I am a perfectionist by nature and this issue has been eating away at me (I've spend a good deal of time over the last year focused on valve selection). Your encouragements are a definite answer to prayer.

God bless,
-Steve

To answer your question yes they can get a pretty good estimate of the gradient from echos, you also can get a good idea, by keeping track of the left ventricle size and the Valve opening or Area might say "Area of effective orifice" or something like that. and even then it can take months/a year or so for the heart to settle down , meaning the left ventricle might keep getting smaller (IF it was enlarged before surgery) over time. IF you have all your test from before surgery, you might want to put them on a chart so you can easily see how things are getting bigger or smaller over time. IF you dont have them you might want to ask for them so you can see how things are improving since before your surgery.

Also you probably know this, but lots of times I write things for newer people who might read this, If you have different test results, ECHO, MRI, CATH CT etc dont compare echos to MRI each results will probably be different , so compare echos to echos, MRI to MRIs etc.

NOW this may not have anything to do with a case like yours where the heart/valves aorta are large, my guess would be the bigger your valve/Aorta the more wiggle room, or room to play compared to someone who has a small or average size heart, where making the valve smaller could make a big difference.

For the Aortic valve the gradient is basically the difference of pressure between the left ventricle and the other side of the Aortic valve. Normally as the valve gets smaller the pressure difference gets higher since left ventricle has to work harder to push blood thru the smaller opening and blood builds up in the left ventricle. So the left ventricle can get larger over time or AFTER surgery the ventricle might not get as much smaller than normal with a larger valve. I seem to remember you like reading technical things and probably are at the point in your recovery your getting bored so here are some pretty good sites that explain alot heart related and tests results http://www.cvphysiology.com/Hemodynamics/H001.htm and http://www.ncbi.nlm.nih.gov/books/NBK2215/

 

[AgilityDog]

I'm sure the difference in the sizes of my valves is because the mitral went out first, and the heart was badly damaged by delay before surgery. My surgeon said he was somewhat surprised that I took one that big, given I'm not that large a person.

The aortic replacement was done 4 years later, after my heart remodeled and the atrium returned to near normal size. The aortic damage was somewhat incident to the mitral damage, so I'm told.

Since the aortic valve was done before it went to hell in a hand basket, unlike the mitral, that 19mm is probably much closer to what would be "normal" for me, whereas the mitral was done when I was in severe CHF and the heart was enlarged.

 

[Lynlw]

ChaC, I meant to ask beside having a large annulus, what your body size is usually what they use to determine what size valve would be considerred too small or just right, now of course all forumulas are just general and dont take individual circumstances int them but i believe the formula to determine if there is PPM or not is the indexed EOA.. That is the EOA of the prosthesis divided by the patient’s body surface area then depending on that number it falls into Mild (not clinicallly signif) moderate or severe PPM catagory http://circ.ahajournals.org/content/119/7/1034/T3.expansion.html has the chart. usually they would check that before they placed the valve and if it looks like there would be PPM they can do a few different things while installing it so since your surgeon said it would be fine. my guess is he checked all that out before he placed it.

 

[chaconne]

Thanks for the link Lyn,

I just calculated my number:

I weigh 195 Lbs, and am 6'2" tall.

According to: http://www.halls.md/body-surface-area/bsa.htm, my body surface area is 2.15 m^2.

According to data sheets, my On-X valve has an area, excluding the leaflets, of 3.73 cm^2.

So my number is 3.73/2.15 = 1.73 cm^2/m^2. As you and Norm have suggested, it looks like I'm far from the problem zone (<0.85)

 

[Lynlw]

Thanks for the link Lyn,

I just calculated my number:

I weigh 195 Lbs, and am 6'2" tall.

According to: http://www.halls.md/body-surface-area/bsa.htm, my body surface area is 2.15 m^2.

According to data sheets, my On-X valve has an area, excluding the leaflets, of 3.73 cm^2.

So my number is 3.73/2.15 = 1.73 cm^2/m^2. As you and Norm have suggested, it looks like I'm far from the problem zone (<0.85)

I'm glad it helped. I'm confused tho where did you get the 3.73? and Math is NOT my strong point

 

[yotphix]

Going back to an earlier post regarding waiting to see the results vis a vis ventricular remodeling, I just discovered that my ventricle, which was still mildly enlarge at 1.5 years out (though it had remodeled significantly) has now, a year after that, returned to completely normal size. The hypertrophy is no longer detectable either by echo or by ECG, whereas both saw it last year.
I have a 29mm valve, and though I'm a little smaller than chaconne at 6' and 170lbs, it is adequate for me to run 3-6 miles @ 8-10 min/mile 5 or 6 times per week. My endurance continues to improve. My VO2 Max was measured last week at 114% of my age predicted max too, and since cardiac output is a major factor in VO2 max, it clearly isn't limiting me in anyway.
I never did ask my surgeon though, if that was the biggest valve which would have fit, or just the biggest one handy! I had told him in advance that I intended to put whatever he gave me through it's paces and that I would appreciate maximum flow.

 

[chaconne]

Lyn,

The 3.73 cm^2 for the 25mm On-X valve comes from an On-X data sheet that I have. I assume it was derived from the diameter being 23.4mm (from the same data sheet).

Valve Area = pi*radius^2 = 3.14159*(2.34cm/2) = 4.3cm^2. Subtracting the leaflet and any other block apparently gives 3.73cm^2 which is the effective, unobstructed flow area of the valve.

 

[chaconne]

yotphix,

It's very good to hear that your heart has gone back to normal. I'm hoping the same happens to me and that I can get back to rigorous cycling, swimming, running and hiking. Thanks for the post. What type and make is your valve?

 

[normofthenorth]

FWIW, we've had a brief discussion here about the various formulas -- at least THREE of them, IIRC -- used to adjust valve areas to compensate for different body sizes. They all coincide around average sizes, but they produce very different results in the "tails" of the distribution -- i.e., for unusually small and large people. As I recall, one or two used the patient's body surface AREA, and 1 or 2 used the patient's body VOLUME. Or maybe it was HEIGHT. At any rate, they used different "orders" or "exponents", which would diverge hugely as body size varied. I think the simple "take home" message for most people is simply that changes in effective valve area do NOT correlate strongly with max cardiac output levels, much less excellence in sports. And most of the exceptions would be unusually big people with unusually small valves.

 

[Lynlw]

Lyn,

The 3.73 cm^2 for the 25mm On-X valve comes from an On-X data sheet that I have. I assume it was derived from the diameter being 23.4mm (from the same data sheet).

Valve Area = pi*radius^2 = 3.14159*(2.34cm/2) = 4.3cm^2. Subtracting the leaflet and any other block apparently gives 3.73cm^2 which is the effective, unobstructed flow area of the valve.

Do you have the measurements of your valve area since surgery?