A minor, everyday stress like public speaking can be as damaging to the heart as strenuous exercise in people who have cardiac disease, and can even trigger heart attacks, according to research published Thursday.

The researchers found that the common stresses can cause silent ischemia, a painless but ominous disruption in the flow of blood to the heart's own muscle.The study shows that "previously unrecognized mental activities have very important consequences," said Dr. Carl J. Pepine of the University of Florida.

It also appears that mental stress is a possible cardiac problem only for people with heart disease, not those those with healthy hearts.

The chief author of the study recommended that people suspected of having heart disease those who smoke or have high blood pressure, high cholesterol or a family history of heart trouble should be checked for this condition so they can be treated.

When silent ischemia is discovered during routine tests, people can be treated with medicines, coronary bypass surgery or angioplasty, a common procedure that uses balloons to open up clogged heart arteries.

"Nothing should come out of this work about what patients should or shouldn't be doing in their daily lives," said the lead researcher, Dr. Alan Rozanski of Cedars-Sinai Medical Center in Los Angeles.

If ischemia lasts for more than 20 or 30 minutes, the oxygen-starved section of the heart dies, resulting in a heart attack. Although the crisis usually passes in a few minutes without permanent damage, it may be a warning of more serious heart problems to come.