More than a decade ago, when my dad needed heart valve replacement surgery, he faced a difficult decision that he discussed at length with his surgeon. The surgery would entail replacing his mitral valve with either a mechanical valve or a biological tissue valve made from pig or cow tissue.
Since my dad was in the 50 to 70 age range category, according to national guidelines, he got to choose which one.
Like a majority of the more than 50,000 people in the United States who undergo either aortic or mitral valve replacement surgery each year, he wasn’t sure which choice was best. And neither was his surgeon. For patients under 50, mechanical valves are recommended because they are likely to last a lifetime, but they also come with a lifetime prescription of blood-thinning medication. For those over 70, guidelines recommend a biological valve which usually lasts between 10-15 years and will most likely last the life of the patient. Those in the middle, like my dad, exist in a gray area where no one really knows the right answer. Currently guidelines don’t differentiate between the type of valve replaced.
There are pros and cons to both types of valves, but up until now there hasn’t been much scientific evidence available to help patients make the best choice.
A Stanford study published today in the New England Journal of Medicine may provide new evidence that could swing the decision-making pendulum toward the mechanical valve choice far more frequently.
It turns out that it matters whether the mitral valve (which connects heart chambers) or aortic valve (which leads out of the heart) needs replacement. And it suggests that in many cases, mechanical valves are a better choice.
This has potential to significantly impact the current national practice guidelines. While our preference is always to repair heart valves whenever possible, there are certain disease processes which necessitate valve replacement. For these patients, given the study's new and unexpected findings, I am already pondering, 'How am I going to counsel my patients today?'
By examining patient records obtained from the California Office of Statewide Health Planning and Development databases, Woo and his colleagues compared the long-term risks and benefits of the two different types of valves. They looked at the rates of mortality, stroke, bleeding and reoperation in patients who underwent heart-valve surgery at 142 hospitals in California between 1996 and 2013.
Researchers then examined the records of 9,942 patients who underwent aortic-valve replacement and 15,503 patients who underwent mitral-valve replacement during the study period.
The results of the study, Woo said, are particularly relevant today because of a recent trend toward younger patients choosing biological valves, primarily because they don’t want to deal with a lifetime of taking blood thinners.
"Over the last 15 or 20 years around the world, there has been a dramatic shift in the increased use of bioprosthetic valves," said Michael Argenziano, MD, professor of surgery and chief of adult cardiac surgery at Columbia University, who was not involved in the study. "This is the first paper to provide solid evidence that maybe we have been moving too quickly away from the mechanical valve."
My dad, unfortunately, ended up having to undergo two of these open heart surgeries. As a result, he experienced what it was like to live for years with both types of valves. With the mechanical valve, he took the daily blood-thinner medication to prevent blood clots which also entailed routine blood tests and a restricted diet — all of which he hated. With the biological valve, we all worried over how long it would last. Like many patients with heart valve disease, he struggled with the choice, and never really knew if he made the right one.
Previously: Looking at aortic valve replacement without open heart surgery, Mysteries of the heart: Stanford Medicine magazine answers cardiovascular questions, Ask Stanford Med: Answers to your questions about heart health and cardiovascular research and Major advancement for once inoperable ailing heart valves
Photo of Richard White courtesy of Tracie White