A pregnancy hormone that relaxes blood vessels appeared to reduce symptoms of acute heart failure and improve survival, according to a preliminary study released by U.S. researchers on Sunday.

They said the hormone relaxin, which is being developed by privately held Corthera Inc of California, was safe, and showed signs of reducing the risk of death from heart problems during the study.

The findings suggest that "early administration of this drug, in addition to standard therapy, might be associated with more rapid, sustained and complete resolution of acute heart failure, as well as with more favorable long-term outcomes," John Teerlink of the University of California, San Francisco, and colleagues wrote in the journal Lancet.

"If established in larger studies, the benefits of relaxin might represent an important advance in the treatment of patients with acute heart failure," the researchers wrote.

In pregnancy, the hormone helps relax and lengthen the cervix to prepare for childbirth, but it is also thought to be a natural vasodilator, widening blood vessels and allowing blood to flow more freely.

Vasodilators are often given to people with high blood pressure, which is common in heart failure, a condition in which the heart gradually loses its ability to pump blood efficiently, leaving organs starved for oxygen.

Teerlink and colleagues studied 234 elderly patients with heart failure and high blood pressure who were given either a 48-hour intravenous infusion of the drug or a placebo.

They found it was safe and helped to reduce shortness of breath in 40 percent of patients who received a moderate dose of the drug, compared with 23 percent who took a placebo.

It also reduced the number of patients in the study who died from heart problems or were readmitted to the hospital within two months for kidney failure compared with the placebo, according to the results, which were also presented at the American College of Cardiology meeting in Florida.

An estimated 5.3 million Americans have heart failure, a chronic but often deadly condition that will cost $34.8 billion this year for direct and indirect U.S. treatment costs, according to the American Heart Association.