Mechanical pulmonary valve

[MI_Marcus]

Hello,

Here's a brief history of my situation to give my question a little context. I had the Ross Procedure preformed when I was 14 and have since developed an ascending aortic aneurysm. I'm scheduled to have the aneurysm repaired later this summer, in August, and the surgeon said it's a good time to replace my pulmonary valve (currently a homograft) as well. I've been doing some research and there seems to be controversy about mechanical valves in that position. Why aren't mechanical pulmonary valves common?

I'd also really appreciate it if anyone could supply me with some additional literature (studies or articles) on the subject to back up their claims; or links where I can find some. This will be my second OHS and I'd really prefer it to be my last. I'd rather take coumadin for the rest of my life than go through a third OHS.

 

[Ross]

Not ignoring you, just don't know the correct answer.

 

[Mary]

I don't know if they make a mechanical for the pulmonary position. Have you checked the literature to find out?

 

[ALCapshaw2]

I have referred your Question to one of my contacts 'in the industry'.

 

[Lynlw]

The VAST majority of surgeons will not use a mech vale in the pulmonary position because the pressure is so low there is a very good chance clots would form.
For the most part, they do not make specific pulmonay valves they use valves made for the aortic position (except the contregra conduit is a cows jugular vein that has a valve in it) The surgeons/ docs that have the most expeirince with Pulmonary valve replacements as far as I know are CHD surgeons, since for the most part, pulm valve problem are usualy congenital and not aquired.
Tissue valve tend to last longer in the pulm postion than other postions because of the lower pressures there isn't usually as much wear and tear.
My son and MOST people I know that have their pulm replaced have bovine valves and usually a dacron conduit I can look for articles later but I usually search pubmed.com for pulmonary valve, bovine or homograph.

FWIW and I KNOW everyone is different, but My son was 17 when he got his bovine vale so he was the prime age to destroy valves, he neded a section of his conduit replaced 2 years later and depending how the valve looked they would replace it or not. it looked brand new

 

[MI_Marcus]

Thanks for the suggestion. I'll check pubmed.com for some more info. I've been having trouble finding stuff on my own so far.

I guess I'll just have to get used to the idea of multiple surgeries. I'm 24 now so hopefully the next won't be for a while, every ten years will get old fast. Now I'd just like to read up on the subject for knowledge's sake. I'm very curious about this topic.

 

[Lynlw]

Thanks for the suggestion. I'll check pubmed.com for some more info. I've been having trouble finding stuff on my own so far.

I guess I'll just have to get used to the idea of multiple surgeries. I'm 24 now so hopefully the next won't be for a while, every ten years will get old fast. Now I'd just like to read up on the subject for knowledge's sake. I'm very curious about this topic.

I certainly understand, my son is 21 and has had 5 OHS and 2 more heart related surgeries. The ONE bright spot is the clinical trials are going very well for replacing the pulm valves with caths, hopefully if not by your next replacement the one after that will be easier, if not by cath.

 

[laurad37]

I had my pulmonary valve replaced and my cardiologist and surgeon both told me that they don't put mechanical valves in the pulmonary position.

 

[MI_Marcus]

What I'm really looking for now is a reason why surgeons don't replace the pulmonary with a mechanical valve.

 

[Dina]

What I'm really looking for now is a reason why surgeons don't replace the pulmonary with a mechanical valve.

As Lynlw said , the pulmonary valve is a very low pressure area and so
this makes clotting much more likely to occur,even with the coumadin.
Tissue valves are less likely to clot,so they would only use them for pulmonary.
The tissue valve will also last much longer given the less wear and tear of a low pressure area.

 

[Dina]

I certainly understand, my son is 21 and has had 5 OHS and 2 more heart related surgeries. The ONE bright spot is the clinical trials are going very well for replacing the pulm valves with caths, hopefully if not by your next replacement the one after that will be easier, if not by cath.

I thought valves in this position lasted much longer..? Is it just his age, or
the infection(osteo,etc) that damaged them early? Maybe it would last
longer with a young adult (post- hormone/growth craze)..? Curious what you think.

 

[Lynlw]

I thought valves in this position lasted much longer..? Is it just his age, or
the infection(osteo,etc) that damaged them early? Maybe it would last
longer with a young adult (post- hormone/growth craze)..? Curious what you think.

YES you are correct valves generally last longer in the pulm postion. His pulmonary valve is doing well,(so far knock on wood) actually it is his first one before that he didn't have one.
A section of his conduit needed replaced because of a combination of scarring at the seam and his sternum squishing it. His other surgeries were a shunt (at 10 days)to get him big enough to do his big surgery ( one of his CHD was his aorta and pulm valve were switched so he had a Rastelli where they basically rebuilt his heart and rerouted alot of his blood at 18 months) Then when he was 10 he had a section of the conduit (that was built in the OR during the Rastelli) replaced because of calcification and growing.

The sternal infection was after his last surgery, luckily there was no damage to his heart. and he DID have BE when he was 11 but that left his valves alone too.

 

[ALCapshaw2]

My industry contact confirms that using a Mechanical Valve in the Pulmonary Position is RARELY performed, especially in the USA.

In the past 13 years, their valves have only been used a few times in that position, mostly in Korea.

 

[MI_Marcus]

Why is a low pressure area more prone to clotting? How does a lower pressure result in more damaged red blood cells?

 

[Mary]

Why is a low pressure area more prone to clotting? How does a lower pressure result in more damaged red blood cells?

The force of blood is slower, giving it more time to form clots. It doesn't damage the red blood cells.

 

[Adrienne]

Why is a low pressure area more prone to clotting? How does a lower pressure result in more damaged red blood cells?

I think it is because in a low-pressure area, the blood is not pushed through as fast and can stagnate to a certain extent which gives it the time to clot.

 

[ALCapshaw2]

Clots can develop if there are Edy Currents in the blood flow.

They can also form on the (mechanical) valve leaflets.
This is more likely to happen in valves with Low Pressure and Low Velocity Blood Flow.

The higher the Velocity of the blood flow, the better the blood 'washes' the valve leaflets. This is why clots are least likely to form at the Aortic Valve. The velocity through the Mitral Valve is in-between the rate at the Aortic Valve and Pulmonary Valve.

Older style Mechanical Valves are known to cause some damage to the red blood cells, especially as they are forced through the pivot areas. The newer On-X Valves (1996) have been designed to reduce this damage (by half), resulting in Hemolysis numbers on a par with Tissue Valves.