The Home Automated External Defibrillator Trial, a randomized international clinical trial, followed 7,001 heart attack patients at moderate risk of sudden cardiac arrest who had a spouse or other live-in companion who agreed to take conventional steps to respond to a sudden cardiac arrest. Some called emergency medical services and performed cardiopulmonary resuscitation; some households were asked to use an automated external defibrillator, before taking conventional life-saving steps.

Dr. Elizabeth G. Nabel, director of the National Heart, Lung, and Blood Institute, said after an average of three years of follow-up survival rates were about the same for all study subjects.

However, there were relatively few sudden cardiac arrests and 39 percent of these events were witnessed at home.

"The important message here is that every minute counts, and quick action is key," Nabel said in a statement. "Use an automated external defibrillator, if one is handy or perform CPR -- and always call for help by emergency medical professionals, such as by dialing 911."

The findings were reported at the American College of Cardiology Scientific Sessions in Chicago,