MILWAUKEE – Lie down, relax for a minute and take your pulse.

If it’s more than 75 beats a minute and you’re a man in your early 40s to early 50s, your life may end suddenly someday because of a heart-related cause.

An elevated resting heart rate was one of three relatively simple heart rate tests that seem to predict a man’s future risk of sudden cardiac death, according to a study published today in the New England Journal of Medicine.

The method could be used to help identify seemingly healthy but high-risk individuals, such as deer hunters who are more likely to die in the field because of the stress and strain of the hunt, according to researchers who were not part of the study.

“For one out of four people, their first warning is sudden cardiac death,” said Patrick McBride, a professor of medicine at the University of Wisconsin Medical School in Madison. “Many of them just don’t make it to the hospital.”

McBride, co-director of the UW preventive cardiology program, said the new study adds important information to the traditional exercise stress test.

McBride, who was not a part of the study, said its findings most likely apply to women as well as older and younger men.

The test could be useful for men over 40 and women over 50 who have at least two risk factors for heart disease such as high cholesterol, high blood pressure, obesity or a family history of heart disease, especially if they plan to begin a vigorous exercise program, he said.

Sudden cardiac death occurs in 400,000 to 460,000 people in the U.S. each year.

The research is the first large study to show an association between so-called heart rate profile and the future risk of sudden cardiac death in healthy people, said lead author Xavier Jouven, a physician at Georges Pompidou European Hospital in Paris.

The study involved 5,713 French civil servants, all men aged 42 to 53 with no signs of cardiovascular disease. They all underwent an exhausting 10-minute bike test between 1967 and 1972 and then were followed for an average of 23 years.

The study found that men whose resting heart rate at the time was more than 75 beats a minute were nearly four times as likely to die of a sudden cardiac cause as those whose resting heart rate was less than 75 beats.

In addition, sudden cardiac death was six times more likely to occur in those whose heart rate failed to increase by at least 89 beats a minute during the bike test. And those whose heart rate declined less than 25 beats one minute after the test ended were at more than two times the risk of sudden cardiac death.

In an era of increasingly sophisticated heart tests, the measure represents a relatively easy and harmless approach to assess risk, said Sam Wann, a cardiologist with the Wisconsin Heart Hospital.

“It’s simple,” Wann said. “A lot of the things we do are high-tech and cost a lot of money.”

However, Wann said he does not recommend that people use their resting heart rate to predict their heart risk, partly because it can create a false sense of security and cause people to ignore other important measures such as cholesterol, blood pressure, smoking, body weight and family medical history.

The study follows earlier research showing that similar tests can predict sudden death risk in heart patients, said Carl Foster, a professor of exercise and sports science at the University of Wisconsin-La Crosse. The new study extends those finding to seemingly healthy men, Foster said.

For that reason, it would be an excellent test to administer to deer hunters before they go out into the woods.

“It would probably save a lot of lives,” Foster said.

Foster, who has done research on the strain that deer hunting and other exercise can put on the heart, noted that just siting a deer in a rifle scope can dramatically raise a hunter’s heart rate. Dragging a dead deer out of the woods can be equally stressful, he said.

What is not known is whether the bike test was detecting early coronary artery disease that could lead to a heart attack or whether an elevated resting heart rate and poor bike test performance were signs of those who were at risk for a fatal irregular heart beat caused by a heart attack.

“It represents a susceptibility to ventricular arrhythmia,” said lead author Jouven, an associate professor of cardiology and epidemiology at Paris University.

Ventricular arrhythmias are irregular heart beats in either of the heart’s two lower pumping chambers. They can occur during a heart attack.

“When the cells of the heart don’t get enough blood (a heart attack), they get highly irritable and send out these arrhythmias,” said McBride of the University of Wisconsin. “They start firing, and the heart gets into an irregular rhythm.”

Doctors said one of the best ways for people to improve their heart rate profile is through exercise.

Physically fit people tend to have lower resting heart rates, and their hearts are more likely to respond better to intense physical activity.

Sedentary people are five times more likely to die suddenly from a cardiac cause, McBride added.

“The best way to reduce your risk of sudden death is to get regular exercise,” he said.

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