The study, published in Circulation: Journal of the American Heart Association, says about one in four doctors of patients with advanced congestive heart failure got it wrong.

The authors of the study say patients sometimes change their minds about whether they want their doctors to "pull the plug".

Unlike people with terminal cancer whose condition steadily declines, individuals with severe congestive heart failure may have episodes of feeling relatively well between times when they feel as if they are at death's door, according to Associate Professor at Yale School of Medicine, Dr Harlan Krumholz.

Death's door

"There were times for some patients in the hospital when they felt like they didn't want to go on, that if their heart stopped this was the time their life should end," says Dr Krumholtz.

"Then there were times after being discharged when they were feeling better and felt that if their heart stopped their condition was fair enough that they would want to be revived.

"It is a particularly challenging aspect of heart failure that the condition fluctuates. People's feelings can change, and their preferences about resuscitation can change."

Among 600 patients questioned two months after their initial response, 19% had different viewpoints.

Patients' preferences

In the study's survey of do-not-resuscitate (DNR) preferences among 936 individuals hospitalised for severe heart failure, nearly one-quarter said they did not wish to receive artificial respiration.

However, physicians misjudged their patients' preferences for 24% of the individuals.

Dr Krumholz and his colleagues at the Yale School of Medicine and the Yale-New Haven Center for Outcomes Research and Evaluation found that although 25% of patients said they had discussed the issue with their doctor, agreement between patient and physician was still lacking.

"There is a need to improve patient-doctor communication about the topic, even though it is often difficult to discuss."

Weakened heart

More than 4.9 million Americans suffer from congestive heart failure, and the condition is newly diagnosed in about 400,000 individuals each year.

It occurs when the heart does not function properly as a pump. It is accompanied by a build-up of fluids in the body. This happens because blood flow slows, thus decreasing the amount of blood pumped from the heart.