New research suggests surgically implanted mechanical valves may offer better long-term survival than biologic prostheses.
“We were very surprised to find the benefit of mechanical valves really outlasted or exceeded that of biologic valves all the way up to age 70, when the neutral zone is 50 to 70,” senior author Dr. Y. Joseph Woo of Stanford University told theheart.org/Medscape Cardiology. “This is probably very different from what’s going on in practice right now, where we’re moving to biologic valves earlier and earlier.”
Over the past 15 or 20 years, there has been a dramatic shift around the world in the increased use of bioprosthetic valves, Dr. Michael Argenziano of Columbia University, who was not involved in the study, noted in a news release from Stanford.
“This is the first paper to provide solid evidence that maybe we have been moving too quickly away from the mechanical valve,” Dr. Argenziano said.
Woo observed that current practice guidelines are supported by anecdotal information and smaller underpowered trials and have been simplified over the years to recommend a mechanical valve for patients under age 50, a biologic valve for those over age 70, and “dealer’s choice” of either a mechanical or biological valve for those 50 to 70 years, with no distinction made between valve positions.
Based on the current results, however, “reinstatement of valve-specific guidelines for the selection of a prosthesis warrants further exploration,” the investigators write in the study, published November 9, 2017 in the New England Journal of Medicine.
Commenting for theheart.org/Medscape Cardiology, Dr. Ravi Dave (University of California Los Angeles) said, “What this study shows is that the difference is not just minor; there is a mortality benefit in the aortic and mitral position with mechanical valves. “It brings up the question of whether we should be changing our practice and implement more metallic-valve use, and I think that’s a question that needs to be answered on a case-by-case basis.”
To compare the long-term benefits and risks of the two prostheses in a large population, the investigators examined data from 25,445 patients from 142 California hospitals who underwent aortic- and mitral-valve replacement from 1996 through 2013. Patients receiving biologic valves were older and had more comorbidities. Inverse probability weighting was performed to balance baseline characteristics.
Over the study period, the use of biologic valves increased significantly for aortic-valve (11.5% to 51.6%) and mitral-valve replacement (16.8% to 53.7%). At 15 years, mortality was significantly higher with a biologic aortic valve than a mechanical aortic valve among patients aged 45 to 54, but not those aged 55 to 64 at the time of surgery.
“I’d say it’s relatively uncommon for someone to recommend to, say, a 65-year-old or older patient a mechanical valve in the mitral position in practice, but in terms of outcomes, at least our paper would suggest your patient is going to be better off if you put in a mechanical valve,” Woo said.
The mortality benefit with the mechanical valve, however, came at the cost of a higher risk of bleeding and, in some age groups, stroke, but was associated with a significantly lower risk of reoperation than a biologic valve.
“Maybe we shouldn’t be lumping these patients together but should be customizing the decision,” Woo concluded.
Eight years ago, I learned that although I had completed over 20 marathons and was still running 5-6 days a week, I had a defective aortic valve. I had noticed a bit of difficulty catching my breath after a tough run but chalked it up to the ageing process.
A physician/neighbor to whom I mentioned this, fetched his stethoscope and listened to my heart over a couple of beers we were having at his home. A minute or thereabouts later he said something like, “Steve, I’ll call over to UCSD and have them waiting for you there at the ER.” I recall saying something like, “Sure, Bill, real funny.” But he looked me in the eye and said, “I’m serious Steve, you need to go.”
Realizing he wasn’t kidding, I said, “Alright, I guess I’ll go home, shower and pick up some clothes.” To which he replied, “No, you need to go directly there; and now.”
Long story short, I was diagnosed with heart failure (I forget which stage) due to a damaged aortic valve. About two weeks later, I emerged from the cardiology wing of the UC, San Diego Medical Center with a new titanium valve, metal root and stem, and a 9-inch scar on my chest.
The Stanford study is unquestionably a shocker. Oddly, however, there was no mention in that study of the vastly different risks of infection in the two types of heart valves which, were it to occur, the resulting fatality rate from endocarditis is high. My cardio team had mentioned this risk, but more on that later.
Just before I had my valve replaced, I recall watching Robin Williams on the David Letterman Show discussing his recent aortic valve replacement with a calf (bovine) biologic valve and showing a picture of the scar on his chest. He was 57 when he had the surgery. (The procedure was performed at the Cleveland Clinic.)
Naturally, as a lifelong fan of the Oscar-winning comedian, my first inclination was to opt for the exact same valve he chose, made from bovine tissue.
My cardio team at UCSD, however, was not having any part of my argument, which essentially was based on Robin Williams having chosen the biologic valve. It was going to be the St. Jude titanium valve, or I’d have to find another hospital.
The entire argument for the biologic valve has heretofore rested largely on the drawbacks of taking anticoagulant meds like warfarin. And the bleeding issue is quite real.
As for the valve infection issue, a complication that carries a high fatality risk is prosthetic valve endocarditis, which occurs when the new valve is infected by bacteria. Until now, there have been no figures on whether the infection frequency differs between the two valve types. It has also been unknown how common infections in an artificial heart valve are.
We just learned a lot more. Turns out that infections in surgically implanted heart valves are more common in patients who have been given a biological prosthetic valve than in those with a mechanical one, according to a study from Karolinska Institutet, published last July in the journal Circulation.
The risk of infection in the artificial valve was about 50% higher with a biological prosthesis than with a mechanical. The follow-up time was up to 18 years.
“We hadn’t expected this large difference,” says Natalie Glaser, doctoral student at Karolinska Institutet’s Department of Molecular Medicine and Surgery. “Our results are important as they tell us more about complications following the surgical replacement of aortic valves.”
I have a mechanical heart valve, and from what I’ve subsequently learned, it was the right choice for me–not necessarily for everyone–for the reasons mentioned in this piece. There are some minor nuisances.Steve's Take: Before making a choice of a mechanical versus biologic #heart valve, be fully informed. Click To Tweet
I’m on warfarin and self-test my blood’s clotting condition, called the International Normalized Ratio (INR). After the initial surgery I went to a special clinic at UCSD until the correct daily dosage was established. Since then, I test once a week and report the INR to the device manufacturer’s (Roche) website portal which, in turn, reports it to my doctor. The whole process takes about10-15 minutes.
No one told me before the procedure about hearing my heartbeat greatly amplified afterwards. It took me approximately two years to fully adapt to the sound until it became more like the sound of my breathing. No big deal.
When I cut myself, say, shaving, it can several hours before the bleeding stops. But a ready supply of band aids generally helps me cope.
On the other hand, when I recently asked my cardiologist how long he thought my valve would last, he quipped: “It will outlast all of us.”
If faced with the need for a valve replacement, before making a choice of mechanical versus biologic versions, be certain to feel confident that the choice has been completely customized to you and only you. Not me, or Robin Williams. Ask the questions touched upon in this piece. Put another way, make a fully informed decision. That’s my take.