A simple blood test, taken on admission to hospital, could predict the mortality rate and appropriate treatment for heart patients.
The blood test can be used to measure the level of B-type natriuretic peptide (BNP), a hormone released when the heart is damaged or under stress.
The researchers found that those with higher levels of BNP were more likely to die in hospital.
The pattern was found to persist regardless of age, gender, blood pressure other cardiac health indicators.
Dr Gregg Fonarow, a doctor of cardiovascular medicine and principal investigator of the research, said: "We hope the findings will help physicians more effectively stratify risk and guide treatment.
"This is the first study that definitively demonstrates a connection between BNP and in-hospital mortality risk among heart failure patients."
He continued: "We were very surprised that this blood test was so highly predictive of mortality across a broad population of heart failure patients and range of BNP levels."