A sudden surge of physical activity or bout of extreme emotional distress can precipitate a heart attack in people at risk, according to a recent review of medical literature.

Investigators from the University College London, UK, found consistent evidence from previous studies that when normally inactive people engage in a burst of physical activity, or when people are emotionally stressed, angry or excited, they are more likely to experience a heart attack.

However, despite the potential danger associated with bursts of physical activity, the benefits of exercise very much outweigh its risks, study author Dr. Andrew Steptoe stated.

"It is extremely unlikely that a person will experience a heart attack on any single session of exercise," he said. "Considering that physical fitness and regular exercise are protective for heart disease, my advice would certainly be to carry on exercising."

Steptoe explained that most heart attacks occur when a piece of plaque breaks away from the inside of blood vessels, blocking blood flow to the heart. Vigorous exercise may precipitate this by increasing the chances plaque will become dislodged, he said, or by disrupting the normal heart rhythm.

Emotional stress may have the same effect on the body, and may also put the heart at risk by increasing blood pressure and releasing stress hormones, Steptoe noted.

To investigate how stress can influence the heart, Steptoe and his co-author, Philip C. Strike, reviewed studies conducted between 1970 and 2004 that examined what people were doing and feeling in the hours before their heart attacks.

Overall, studies found that emotional stress and extreme physical activity were two of the most common triggers reported by heart attack patients.

In one study of 224 patients, more than half said they had been very upset or stressed in the 24 hours preceding their attack.

In another study, the most common triggers reported by 1818 heart attack patients included heavy physical work, quarrels at work or home, and mental stress.

Other studies showed that the risk of heart attack appeared to increase within hours of an earthquake, exciting sports match or high-pressure deadlines at work. Still other research in 1623 heart attack patients found that attacks occurred more often within 2 hours after an angry outburst.

The risk of having a heart attack in response to stress appeared to be influenced by how healthy people were to begin with, Steptoe and Strike note in the journal Psychosomatic Medicine.

For instance, one study showed that people who rarely exercised were nearly seven times more likely to have a heart attack after vigorous activity than people who exercised regularly.

Based on these findings, Steptoe recommended that people who are concerned about heart attack avoid vigorous exercise in very cold weather, which can place further stress on the heart. People not used to exercise should start gradually, he said, so as not to shock the system.

Although it's impossible to avoid all emotional stress, "we can learn to control inappropriate emotional displays and keep negative feelings in check," Steptoe added.

SOURCE: Psychosomatic Medicine, March/April 2005.