Mechanical heart valve could be safer for younger patients

New York: Mechanical heart valves may be safer in certain cases than valves made of animal tissue and should be used more in heart-valve replacements, especially in younger patients, suggests new research.

Mechanical valves can last a lifetime, but they come with increased risks of blood clotting and bleeding and a lifetime of having to take the blood-thinning medication warfarin. 

Biological valves, which are most often made from pig or cow tissue, do not increase the risk of bleeding or clotting, but they wear out within about 10 to 15 years, making a second surgery likely.

"If you think about this just in terms of age, the older you are, the less likely that you will outlive the durability of a biological valve," said study senior author Joseph Woo, Professor at Stanford University School of Medicine in the US.

When a valve becomes so diseased that it impedes the delivery of blood to the body, open-heart surgery to replace the valve with a new one generally is recommended. 

Surgeons have noted in recent years a trend toward younger patients choosing biological valves, primarily because they do not want to deal with a lifetime of taking blood thinners and with the accompanying dietary restrictions and routine blood testing necessitated by a mechanical valve, Woo said.

To compare the long-term risks and benefits of mechanical versus biological heart valves, the study, published in The New England Journal of Medicine, examined rates of mortality, stroke, bleeding and reoperation in patients who underwent heart-valve surgery at 142 hospitals in California between 1996 and 2013. 

Patient records were obtained from the California Office of Statewide Health Planning and Development databases.

Researchers 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 aortic valve and the mitral valve are the most commonly replaced heart valves.

"Our research likely contains the largest number of patients ever studied to examine this issue," Woo said.

The study showed that for patients undergoing mitral valve replacement, a mechanical valve is actually beneficial until the age of 70. 

On the other hand, for patients undergoing aortic valve replacement, the benefit of implanting mechanical valves ceased after the age of 55, the study said.