An old measure of health may find new life as a way for doctors to tell just how sick a heart failure -- or "weak heart" -- patient is.

And a new report in the Journal of the American Medical Association found that while low blood pressure is usually a good thing, having a high reading can be good when heart failure patients check in to a hospital, according to a news release.

"During stress, or at the time of admission, it appears that when you have high blood pressure for a limited amount of time, let's say hours, that may indicate that your heart is stronger," said Dr. Mihai Gheorghiade of Northwestern University.

Gheorghiade's study found that if a person with heart failure is still pumping strongly enough to elevate blood pressure, that person is less likely to die. About 1 million people are hospitalized each year with a weak heart.

"So it's not ... that the high blood pressure is good, but it's a measure of the strength of the heart," he said.

But he said that the first thing physicians should do is try to lower the blood pressure. But they need to know what the initial pressure was to determine a course of treatment.

Cardiologist William Cotts said that the simple tool of a blood pressure cuff can provide a lot of valuable information.

"I think going back to the basics and really looking at things like blood pressure, it shows that it's still important to look at the basics of the physical exam," Cotts said.

Gheorghiade said patients should note their blood pressure and remind their doctors of its importance.

The study looked at patients' systolic blood pressure, the higher number that is listed first in a reading. Below 120 is low, and above 140 is high.