Some people with heart failure might benefit from a therapy which helps dampen their overactive immune systems.
US researchers treated more than 1,000 patients, and found those with certain types of heart failure had a lower risk of death or hospitalisation.
Writing in the Lancet journal, they said large numbers of patients could benefit if bigger studies confirmed the findings.
UK experts agreed, saying that much more research would be needed.
Heart failure is caused by a weakening of the organ's ability to pump blood around the body.
In some cases, this has been linked to the body's own immune system, which causes damaging inflammation in its tissues.
Up to 24,000 deaths a year in the UK are thought to be related to the condition.
The latest study, at the Methodist Hospital in Houston, Texas, tries to "damp down" the immune reaction, and hopefully reduce inflammation.
To test how well it worked, the progress of more than 1,000 patients was compared with a similar number given a "dummy" treatment called a placebo.
The method involved taking blood from the patients, and exposing it to chemicals designed to change some of the body's own immune signals, and boost anti-inflammatory signals.
This kind of approach is called "immunomodulation".
After a 22-week cycle of treatment, the patients were monitored for the next 10 months.
Among the treated group, there were 399 deaths or hospital admissions - slightly fewer than the 429 in the untreated group.
This meant that looking at all the patients together, there was either a tiny effect, or none at all, which the researchers described as "disappointing".
However, in patients with specific types of heart failure, such as those who had not had a heart attack, the effect appeared to be more significant, with between a 25% and 39% reduction in risk.
The researchers wrote: "Our findings suggest a role for non-specific immunomodulation as a potential treatment for a large segment of the heart failure population."
However, they conceded that a much bigger and more detailed study, involving far more patients, would be needed before the treatment could be adopted widely.
Professor Peter Weissberg, the British Heart Foundation's Medical Director echoed this: "The study is interesting, but it's still early days.
"A lot more research needs to go into this."