When advising patients who are in need of heart valve replacement surgery, Dr. Kevin Miller breaks down the decision to two basic considerations: mechanical valves and tissue (bioprosthetic) valves.
Dr. Miller is a cardiothoracic surgeon in Denver, Colorado in affiliation with St. Joseph Hospital. He received his medical degree from University of Kansas School of Medicine and has been in practice for more than 20 years.
“There are two basic options – mechanical valves and tissue valves,” Dr. Miller said. “Mechanical valves? Designed to last forever, they don't break down, they don't erode. They can open and close billions of times. So typically, if we put one in, it's expected to last the rest of your life.”
Dr. Miller said with mechanical valves, among his patients’ main considerations is the requirement for lifelong blood thinner medication. This is a drawback for all mechanical valves, but when properly managed, rates are relatively low for both bleeding and clotting.1
An alternative to a mechanical valve is a tissue valve, usually a bovine (cow) tissue heart valve or a porcine (pig) valve, he said.
“The advantage of tissue valves is you don't have to take blood thinner,” he said. “The disadvantage is these things don't last forever.”2
“[Depending on] your age, it's most likely that you will need one maybe even two more of these things [valve replacement surgeries] if we put tissue valves into you.”
The lifetime of tissue valves significantly depends on the patient’s age at the time of the valve replacement surgery. Some tissue valves fail in patients less than 65 years old after only 4 to 6 years. In patients greater than 65 years old, some tissue valves fail after 7 to 10 years.2
Dr. Miller said choosing the type of valve is typically a decision made by the patient, with the help of their physician. He encourages patients to discuss their options and do their own research. He said his patients’ decision typically depends on if they “want to think of the prospect of another surgery or two down the road versus taking the blood thinners.”
An Active Lifestyle with Blood Thinner
Patients considering mechanical heart valves are usually concerned about how taking blood thinner medications will affect their lifestyle, Dr. Miller said.
“Typical questions, can I get back to my regular life? And in the end the answer is yes you can,” Dr. Miller said. “Yes, we have to be careful because we are on a blood thinner, but people have climbed to top of Mount Everest on warfarin. People run marathons on warfarin, [and] triathlons…”
Dr. Miller said when someone is taking a blood thinning medication such as warfarin, they have to monitor their INR, or Internationalized Normalization Ratio.
“The typical [anticoagulant] that we use is warfarin, which the brand name is Coumadin®. It's a pill that you take once a day every day the rest of your life. We do a blood test to make sure we're in the appropriate range – we want a specific [INR] range to keep you in and so we measure your blood tests.”
Certain foods and beverages, such as leafy green vegetables or alcoholic beverages, can affect INR levels. Rather than avoiding these, Dr. Miller said the key is to keep the diet consistent.
“So basically how I talk to my patients is, eat and drink what you want as long as you're consistent on a week-to-week basis. We'll adjust the dose of Coumadin to your diet rather than adjusting your diet to your Coumadin dose.”
“A lot of times alcohol will affect the INR level as well because the same enzymes that are breaking down the Coumadin in your liver are also breaking down the alcohol that you can consume,” he said. “So again, as long as we keep your consumption on a reasonably consistent level throughout the week, then we'll adjust your dose to what you eat and drink rather than adjusting what you eat and drink to the dose of Coumadin.”
Dr. Miller said one of the advantages of the On-X Aortic Valve is that it is [FDA] approved for significantly less blood thinner. In a prospective randomized clinical trial, On-X Aortic Valve patients with a reduced blood thinner dose (after 3 months standard therapy) had >60% fewer bleeding events without an increase in the risk of stroke.3
“On-X Valves are mechanical valves that are FDA approved to have a lower anticoagulation (blood thinner) level than all the other mechanical valves out there,” he said. “The lower that we can keep the anticoagulation level the less chance of bleeding. So it has kind of changed valve selection in patients, especially the young ones that want mechanical valves, simply because the anticoagulation level can be significantly reduced with the On-X [Aortic] Valve.”
- Nishimura R et al., Circulation. 2017;135:e1159-95.
- Wang M et al., Ann Thorac Surg 2017;pii: S0003-4975(17)30266-7.
- On-X Prosthetic Heart Valve Instructions for Use with INR 1.5 – 2.0.