Study: Almost 4 percent of pig valves fail

ST. LOUIS, July 3 (UPI) -- Four out of 106 heart replacement valves from pig hearts failed, U.S. researchers found.

The report, published in the Journal of Thoracic and Cardiovascular Surgery, said the pig valves failed after three, 14, 19 and 44 months, respectively. All four patients were age 70 or older and each received a cow heart tissue replacement.

"A four percent failure rate may not sound like a lot, but we would not expect that many of the valves to fail in such a short period of time," lead author Dr. Jennifer Lawton of Washington University School of Medicine in St. Louis said in a statement.

The researchers said the cause of early valve failure remains unclear. The failed pig heart valves' leaflets showed thickening -- making them stiffer and more likely to interfere with blood leaving the heart through the aorta. Also, they were covered with numerous bumps, but the exact nature of these growths couldn't be determined, the researchers said.

Lawton advises more frequent exams be conducted if symptoms such as shortness of breath, chest pain or lightheadedness occur.

"If patients have had a pig valve implanted, I would tell them that most likely they will be fine, but if they have symptoms they need to see their cardiologist and get an echocardiogram," Lawton said.