Large gaps exist in Americans' knowledge about heart failure, even though nearly 6 million people nationwide have it, a new survey finds.

Nearly half of the more than 1,600 survey participants did not know basic facts about heart failure. And two-thirds confused signs of heart failure with signs of heart attack, according to the American Heart Association survey.

Respondents included the general public, heart-failure patients and caregivers of people with heart failure.

Fifty-eight percent of the participants mistakenly thought heart failure was a natural cause of death that occurs when the heart stops beating. Forty-six percent incorrectly said heart failure is a silent killer with no symptoms.

In fact, heart failure occurs when the heart can't pump enough blood to meet the body's needs. Symptoms include difficulty breathing, fatigue, weight gain of 3 or more pounds in a day, and swelling of the feet, ankles and legs. There is no cure for heart failure, but it can be managed.

"Being aware of the risks and symptoms of heart failure and receiving prompt and proper treatment are key to battling this disease, and that's why these survey results are concerning," said Dr. Gregg Fonarow, director of the Ahmanson-University of California, Los Angeles Cardiomyopathy Center.

"Heart failure is a serious, chronic condition. It requires recognition, treatment and constant monitoring of signs and symptoms to make sure the condition is not worsening, so that quick action to adjust medications or behaviors may be instituted," he said in a heart association news release.

About one in five Americans will develop heart failure, and more than 870,000 new cases are diagnosed in the United States each year. The condition contributes to one in nine deaths nationwide, the heart association noted.

"Many people with heart failure can lead full, enjoyable lives managing their condition with proper treatment and healthy lifestyle changes," Fonarow said. "This is why it is so important for patients and caregivers to understand the disease, and to work together to manage it."

The survey also found that caregivers of people with heart failure were more likely than patients to know the signs and symptoms.