By Michelle Roberts
BBC News health reporter, in Washington DC
Scientists say they have discovered gene differences that reveal which patients will benefit from a common type of heart drug.
Heart failure mortality is high
In the future, doctors could tailor treatments to suit the individual based on their genes, they hope.
Professor Steve Liggett, of the University of Cincinnati, found some patients with heart failure responded better to beta-blockers than others.
"Good" responders had a 38% reduced risk of death as a result.
Heart failure is a serious disease that carries a 50% mortality rate over five years.
Beta-blockers are prescribed along with other heart drugs to relieve the pressure on the heart and help it function more normally.
However, Professor Liggett says, in some patients, adding in a beta-blocker does little to help and may actually cause more problems through side-effects, or through interfering with the other medications the individual is on.
In earlier laboratory research in mice and human tissue, he discovered genetic variations in the receptor that beta-blockers act on in the body.
One version of the beta-1-adrenergic receptor, the Arg version, appeared to respond better to beta-blockers than the other version, Gly.
To test whether this might be important clinically, he recruited 1,040 heart failure patients to take part in a trial. Half of the patients were given a beta-blocker called bucindolol and the other half received a dummy drug.
He followed what happened to the patients over five years and compared the outcomes with each individual's receptor type.
The patients with the Arg receptor fared much better.
"It was only this one group that had any benefit from the beta-blocker," said Professor Liggett.
In addition to the 38% reduction in death rate, these patients had a 36% reduction in the number of times they had to be hospitalised for their condition.
He said it was likely that the same would be true with other beta-blockers more commonly used.
"I'm beginning to get the feeling that this is a class effect."
Other researchers have found a similar variation in response to beta-blocker treatment among people with high blood pressure in relation to the same Arg/Gly receptor.
Professor Liggett predicts that by 2010, it will be possible for doctors to tailor an individual patient's treatment according to their genes.
Speaking on this topic at the annual meeting of the American Association for the Advancement of Science, Kathleen Giacomini, from the University of California-San Francisco, said: "At the moment, we have a situation where drugs that have very serious side-effects are used to treat large numbers of people and are not personalised.
"In the future, we can hope to begin to solve these problems and develop safer medicines."
She said several teams across the US were looking at tailor-made drugs for asthma, cancer, cardiovascular disease and depression.