You wouldn't expect firefighters with known heart conditions to be responding to fires and other stressful emergencies, yet they often are on the front lines and dying in big numbers.

According to a 10-year study of sudden cardiac deaths of American firefighters by the National Fire Protection Association, about half of the firefighters who died of heart attacks had known heart conditions, and about 75% had heart conditions that simple medical testing could have detected.

According to the study of firefighter line-of-duty deaths from 1995 to 2004, 440 firefighters — 43.7% of those who died on the job — experienced sudden cardiac death, typically triggered by stress or exertion.

NFPA was able to gather information on medical conditions for 308 of those 440 firefighters. Researchers found that 134 had previously suffered a heart attack, undergone bypass surgery or angioplasty/stent placement. An additional 97 had severe blockage of the heart's arteries, but it was unclear whether this was known prior to their deaths, the NFPA said.

“What we'd like to see is more screening of firefighters,” said Rita Fahy, author of the study. “We have a standard that lists medical conditions that recruits should be screened for [NFPA 1582] that should probably preclude people from active firefighting roles, although they could be accommodated by a fire department. But then, we also ask for the same kind of screening annually for firefighters who are on the job, and then when they're screened appropriate treatment could be undertaken and an appropriate assignment given to them.”

For the full report, visit www.nfpa.org/fatalityreport.