NEWS
THE SAFEST VALVE DEBATE
A new study from the University of Bristol suggests that patients who receive mechanical heart valve implants may survive longer than those who receive biological ones.
Written by Kayt Sukel
EACH YEAR, CARDIOTHORACIC SURGEONS replace more than 100,000 heart valves as the result of debilitating conditions such as heart failure, valve regurgitation, valve stenosis, or valve infection, making it one of the most common cardiovascular procedures performed. For decades, surgeons have had a choice in what kind of replacement valve to use: mechanical, constructed of synthetic materials, or biological, created using animal tissue from a pig, cow, or even human.
There’s been great debate about which type of valve replacement option is safer for patients in different age ranges, said Gianni Angelini, director of the Bristol Heart Institute, affiliated with the United Kingdom’s University of Bristol.
“For younger patients, we typically go for a mechanical valve. In more elderly patients, we use a tissue valve. But the in between has always been a gray area,” Angelini explained. “Even the American Heart Association’s recommendation for this age range is fairly vague.”
Currently, U.K. practice guidelines call for mechanical valves for patients under the age of 50 years and biological ones for those over 65. To help provide a clearer evidence base for what option is best for the 50- to 70-year age group, Angelini and colleagues looked at the clinical outcomes for patients who had undergone heart valve replacement at the Bristol Heart Institute between 1996 and 2023.
“We had a very large database of clinical outcomes, so we had the opportunity to look at this question,” Angelini said.
His concern was that the reason why so many surgeons gravitated toward biological prostheses was influenced by pressure from manufacturers. The need to provide anti-coagulation drugs to stop potential clotting issues was also a big factor in why many surgeons might prefer biological options. Yet, Angelini couldn’t help but think about women with aortic stenosis who require valve replacement.
“In these cases, you are dealing with a very calcified valve and valve annulus. That makes it very difficult to insert a large valve replacement,” he said. “You have to use a small valve, which can create a lot of stenosis just by itself, because the frame and ring, which is part of this biological valve, can be very narrow and cause problems.”
After researching the clinical outcomes for the more than 1,700 patients, 1,191 of which received the biological valve replacement, Angelini and colleagues discovered that, over the short-term, there were no differences between the two types of valve implants. Long term, however, was a different story. Patients who had received mechanical valves had a better long-term survival rate up to 13 years post-surgery.
A mechanical heart valve implant procedure.
“For younger patients, we typically go for a mechanical valve. In more elderly patients, we use a tissue valve. But the in between has always been a gray area.”
—Gianni Angelini, director of the Bristol Heart Institute
STUDY RESULTS AND IMPLICATIONS
“If you think about that woman who needs a small valve, you can see why there is a problem,” Angelini said. “The most striking finding from our study was that if you use a small biological valve, the follow-up mortality rate is astronomically high. If you put in a big valve, the patient will probably not have many problems and will have a life expectancy of 10 or even 12 to 14 years. But if you put in a small biological valve, the durability is very limited. When you put that inside, you are not making things much better. In fact, most of the time, you are making things worse.”
While the results did not surprise Angelini, they do need to be replicated. He and his colleagues are planning to do the same study using a U.K.-wide database of patient outcomes from patients across the country for at least 15 years.
“This is how we can look at whether what happened in our unit can be applied to the whole nation,” he said.
When asked what mechanical engineers might learn from this study, to perhaps improve upon mechanical valves in the future, Angelini was circumspect.
“The mechanical valves work pretty well. I don’t think there is much we need to improve on the mechanical valve,” he said. “The biggest problem is that patients are told that they will have to take anti-coagulation drugs forever, which is true, but nowadays the mechanical valves are so good that the level of anti-coagulation required is actually quite minimal and easy to monitor. You can even do it at home with your own machine.”
As a result, Angelini’s take-home message to those who may need a heart valve replacement is fairly simple.
“If you are 60 years old and you get a tissue valve, at best, you will need another operation within 10 years or less,” he said. “The biological valves have a gradual deterioration, especially for the small sizes. So, surgeons who have a patient between the age of 60 and 70 should offer a mechanical valve, as long as there aren’t any other contraindications. The idea that a tissue valve will work for 15 to 20 years is a fantasy.”
Kayt Sukel is a technology writer and author in Houston.
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