This could be one reason why black people with the condition are more likely to die than white people.

In a major study of congestive heart failure, US researchers have found that around a fifth more black patients with the disease died than white patients.

Forty-two per cent of black patients who showed symptoms died, compared with 36% of white patients.

Twenty-two per cent of black patients who did not show symptoms died, compared with 14% of white patients.

Adjusting the figures

Other studies have shown that black patients are up to twice as likely to die from congestive heart failure.

But the figures published in the new study, published in the New England Journal of Medicine, are adjusted for factors such as socioeconomic status, other medical conditions, the severity and causes of heart failure and age.

The researchers believe the different death rates could be due to physiological differences in the neuroendocrine and renin/angiotensinogen systems between blacks and whites.

Both systems release hormones that affect heart rate and blood flow when the heart begins to have difficulty pumping blood.

The hormones initially have a beneficial effect in controlling heart disease, but the researchers believe this could wear off over time and the hormones could actually damage the heart.

The neuroendocrine system releases hormones called catecholamines while the renin/angiotensinogen system releases angiotensin II.

Drug treatments

Dr Daniel Dries, who led the research, says the catecholamines may be present in higher numbers in black patients while angiotensin II may play a greater role in whites.

ACE inhibitors, the most common drugs used to treat heart failure, block the actions of angiotensin II.

The most common heart failure drug could be less effective on blacks

Previous studies on patients with high blood pressure have suggested that ACE inhibitors may be less effective in black patients than whites.

Beta blockers, however, block the action of catecholamines.

Dr Dries says the findings, if confirmed by other studies, could suggest new ways of treating black people with heart failure.

For example, beta blockers could be used in combination with ACE inhibitors.

Dr Claude Lenfant, director of the National Heart, Lung and Blood Institute, said: "If research confirms a difference between black and white survival and identifies the underlying cause of this difference, we may see improved treatment of blacks with failure and a greater understanding of this disease among all patients."

Over four million people in the USA suffer from congestive heart failure. Around 600,000 are black.

In the UK, around 10,000 people die from heart failure every year and the condition accounts for 5% of hospital admissions.

Helpful reminder

Professor Brian Pentecost of the British Heart Foundation said the research was "very, very interesting" and "a very helpful reminder" that researchers should include all members of society.

Heart research in the past has concentrated on white, middle class men, said the Foundation.

Professor Pentecost said that previously it was assumed that black people's higher death rates from heart failure were due to socioeconomic factors.