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Heart Rate During and After Exercise Tied to Sudden Death

Slow response, slow recovery raises risk, study finds

WEDNESDAY, May 11, 2005 (HealthDay News) -- The way your heart speeds up when you exercise and returns to normal when you stop can predict your risk of sudden death from heart attack, even decades later, a new European study suggests.

Men whose heart rate increased less than 89 beats per minute during a standard exercise test for heart patients -- called a stress test -- had six times the risk of sudden death over the next two decades, said physicians in France and Italy, who followed more than 5,700 middle-aged men for an average of 23 years.

Men whose heart rate decreased less than 25 beats in the minute after they stopped the exercise test had more than double the risk of sudden death than those whose rate returned to normal faster.

The findings appear in the May 12 issue of the New England Journal of Medicine

This is the latest chapter in a series of studies showing a relationship between a higher risk of death from heart disease and the heart's reaction to exercise, said Dr. Michael S. Lauer, a cardiologist at the Cleveland Clinic Foundation who has done a lot of research on the subject. A paper by his group published in 1999 in the same journal on a trial of 2,500 men was the first to show the relationship between a slow return to a normal heart rate after exercise and increased risk of death, Lauer said.

"We have since published a number of papers, and other groups have published as well, all showing the same thing, that failure of the heart rate to decrease quickly after exercise is associated with a higher risk of mortality," Lauer said. "What is unique and new about this paper is that it specifically looked at sudden death, and most mortality in this group is associated with sudden death.

"The second unique thing [about the new study] is the very long follow-up," Lauer added. "It's pretty amazing when you think about it, that a simple measurement on an exercise test can predict what will happen over the next five, 10, 15 years. It's amazing that an old-fashioned, low-tech test has this power."

The new results are "very similar and consistent" with those of a study on men reported in 2003 by researchers at Johns Hopkins University, said Dr. Roger S. Blumenthal, director of the Hopkins Preventive Cardiology Center.

"This really adds to the literature showing that abnormalities on a stress test can show risk," Blumenthal said. "There is a growing body of information looking at heart rate, not just length of time on the treadmill or EKG changes."

The unanswered question now is how to put this information to use, Lauer said. "We can identify people at increased risk for death, particularly sudden death," he said. "Now we have to see how having this information can translate into improved outcomes for patients."

There are two possible strategies that could be followed, he said. One is the already well-known and often-promoted idea of regular exercise, which is recommended for everyone but could have particular value for people with this heart abnormality.

"People who exercise live longer because exercise stabilizes the electrical system of the heart," Lauer said. "So we could take people with these heart rate problems and enroll them in a formal exercise program that would continue over the long term. My guess is that it would do an enormous amount of good."

A second strategy might be drug therapy aimed at regulating the heart rate, he said. "We have drugs which we used to correct heart rate problems, mainly beta blockers," Lauer said. "They have been shown to improve life expectancy."

A number of studies have shown that "exercise can improve autonomic function and reduce the risk of sudden death," said Dr. William Whang, a cardiac electrophysiology fellow at Massachusetts General Hospital.

Last week at the annual meeting of the Heart Rhythm Society, Whang presented an analysis of data on more than 70,000 women in the Nurses' Health Study showing that those who did little or no regular exercise had six times the risk of sudden cardiac arrest than those who exercised for more than two hours a week.

More information

For more on sudden cardiac death, visit the American Heart Association.

SOURCES: Michael S. Lauer, cardiologist, Cleveland Clinic Foundation; Roger S. Blumenthal, director, Preventive Cardiology Center, Johns Hopkins University, Baltimore; William Whang, M.D., cardiac electrophysiology fellow, Massachusetts General Hospital, Boston; May 12, 2005, New England Journal of Medicine
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