Patients with severe leakage from the mitral valve of the heart who had the valve replaced had significantly lower rates of recurrence and heart failure two years after the procedure than those who underwent surgical repair, according to data presented on Monday.

Mitral valve regurgitation, in which blood leaks backward through the valve into the heart, increases the risk of serious heart problems and death. It affects more than two million Americans.

There was no difference in survival between the two approaches, or in improvement in heart function, measured by amount of blood in the left ventricle following a heartbeat, after two years. But results of the 251-patient study showed clear advantages of replacement.

Two years after undergoing surgery, 59 percent of patients in the repair group had experienced moderate or severe recurrence of the condition versus 3.8 percent in the replacement group, researchers found.

There was also a higher rate of reported heart failure events, 48 versus 29, and readmissions to hospital, 93 versus 59, in the repair group, data presented at the American Heart Association scientific meeting in Orlando showed.

"At two years this is affecting clinical outcomes," said Annetine Gelijns, one of the study's lead investigators.

"What is extraordinarily interesting is if you look at these results, they really point at replacement as probably being the preferred option for this group of patients," she said.

"There was a lot of controversy about what was the best way to surgically approach the mitral valve," Gelijns, from Mount Sinai Hospital in New York, explained.

The field had gravitated toward repair, but reports of high rates of recurrence led researchers to undertake this study, in which surgeons chose valves at their discretion, including those from St Jude Medical, Edwards Lifesciences and Medtronic.

There was a trend toward improved quality of life reported by patients in the replacement group, researchers said.

Procedures were performed via open heart surgery, but companies are looking at ways to replace the mitral valve through less invasive methods.

Companies, including Medtronic, Abbott Laboratories, Edwards and Boston Scientific have been investing in mitral valve technology, which they see as a potentially lucrative future growth driver. Edwards and Medtronic lead the field of minimally invasive aortic valve replacement.

Some patients who had successful repair saw their left ventricle return to normal size, but doctors are not yet able to identify who is most likely to see that benefit, researchers said.