Tissue Valves - the Cheap Tour
Tissue Valves - the Cheap Tour
Here's the skinny on tissue valves, as I see it...
Tissue valves, also called xenografts, are generally the valve of choice for recipients over 65, often even when they are already on warfarin for other reasons. They are also frequently used by young women who hope to become pregnant, in children who are expected to have to be reoperated for other reasons, in people who work in contact sports or physically dangerous occupations, and in patients who work or live in isolated environments (oil rigs, shipboard, the Amazon jungle, Antarctica, etc.).
They have recently begun to be more routinely offered to a whole new group of people, mostly between the ages of 45 and 65, with the awareness that they will have to be reoperated for replacement sometime in their future. This has been made feasible largely by the advancements that have been made in surgical techniques and safety over the last twenty years, as well as improvements in the quality and useful lifespan of xenograft valves.
Due to these improvements, the mortality rates for tissue valves (with reoperations) and mechanical valves (with clot formation tendencies and warfarin bleeding issues) are essentially equal for the general run of patients over time.
For an "uncomplicated" AVR, meaning only the valve is being replaced, there are two valves that currently lead the field for tissue replacements.
The Carpentier-Edwards Perimount Magna bovine valve (CEPM), by Edwards Lifesciences. This is not a natural valve, but rather a valve that is manufactured from natural materials, notably bovine pericardium, which is the tough tissue that surrounds a cow's heart. It has a track record before the recent addition of anticalcification treatments of 80% of its valves lasting over 18 years. Anticipation from the manufacturer is that the valve will now reach 25 years with the same frequency. That is probably optimistic, especially for younger recipients. Still, it makes sense that the valve should last even longer than before. My guess is 21-23 years on average.
The Mosaic porcine valve, by Medtronics. This is a natural aortic valve taken from a pig, carefully preserved, and given anticalcification treatments. It has a track record, before the anticalcification treatments were developed, of a 15-18 year lifespan. The manufactureres have also speculated on reaching the 25-year mark with this valve, because the porcine valves have been more affected by calcification than the bovine valves. Again, this sounds optimistic, particularly for younger recipients, but there should reasonably be a lifespan increase for this valve as well. My guess for this one is 18-20 years.
Considerations...
- Tissue valves do not require any anti-rejection medications of any kind (it is a common misconception that you will need anti-rejection treatments).
- Xenograft valves are biologically inert, insofar as risk of infections or DNA being carried forward from the former owners.
- Tissue valves do not usually last as long as the average in younger recipients, and may last quite a bit longer in recipients over 65. This is generally because the calcification process is much more active in younger individuals.
- Useful valve life figures are averages, and averages can cut either way in individual cases.
- Xenografts do not normally fail suddenly. They fail gradually, like original valves do.
- Your surgeon or cardiologist may give you service-length estimates that are considerably lower than those above. The lower estimates may be justified in young patients (up to about age 43). However, they may also just be providing data from older studies, studies that generalize all brands and types of tissue valves, or studies that are not age-specific. Common quotes based on nonspecific studies of valves made over 20 years ago are 8-10 years and 13-15 years. They are not technically inaccurate, but do not reflect current tissue valve lifespans.
- There are two companies who have xenograft valves currently available with anticalcification treatments (Medtronics and Edwards Lifesciences), and one in clinical trials (St. Jude). All three companies use different anticalcification treatments.
- In terms of quality and functionality, you wouldn't go wrong with either of the valves mentioned. They are both top-flight valves. At seven months after implantation, ventricular recovery and other indicators of the heart's return to normal size and functionality are equivalent between them.
- Operations are more survivable than they were years ago, but they're not nothing. You should give some consideration to your own reactivity to life events like OHS, and determine if that is something you can live with, in return for the relative freedom of a non-compliance-driven, non-anticoagulated life between reops.
- Strategy counts. If you are 52 and have decided on a tissue valve, you may want to choose one with a shorter lifespan. That way, your reoperation would occur before or at the 70-year-old mark. You may be able to recover faster from a reop at 70 than at 75. (Example: at 51, I went with Mosaic, which I estimate should cause me to be reoperated at about age 70.)
- If you have a connective tissue problem, you may have what is called myxomatous tissue. This is tissue that tears easily, due to fibrous or other abnormal content. While uncommon, this can be associated with some bicuspid valve syndromes (BAV). This type of tissue is probably best served by the use of a mechanical valve, inthat it should be disturbed as infrequently as possible. Your surgeon may make that decision for you during the operation, as its presence can't always be determined ahead of time.
- Having a xenograft valve doesn't mean you'll never be on warfarin. Warfarin is a useful drug prescribed for people who have high clotting propensities, such as may be caused by recurrent atrial fibrillation, which is independent of your valve type.
- You will still have to take prophylactic antibiotics for some invasive dental procedures or invasive medical tests (not blood draws), just as you did before your surgery. This is also true for mechanical valves or Ross Procedures.
- You should go for annual echoes, to ensure that your valve continues to be working well. This is also true for mechanical valves or Ross Procedures.
Be sure to register your valve with the manufacturer. You will receive a wallet card in return, which you can use to amaze your friends. Unfortunately, there doesn't seem to be a secret decoder ring anywhere in my envelope...
Best wishes,
