How quickly a heart beat returns to normal after a common treadmill test can predict the risk of death in the next few years, a finding that helps make such tests a powerful tool, researchers reported on Tuesday.

A look at 9,454 patients at the Cleveland Clinic who underwent stress tests found that in 20 percent of them the heart rate fell by 12 beats per minute or less in the first minute after the test ended -- an abnormal recovery rate.

Follow-ups for the next five years found the abnormal group was four times more likely to die from a variety of causes than patients in the test whose heart rates returned to normal faster.

An abnormal heart rate recovery after exercise may signal an insufficient blood supply to the heart muscle.

When those readings are combined with another score on the test -- how long the patient was able to stay on the treadmill -- the results are even more valuable, said the report published in this week's Journal of the American Medical Association.

"Our study suggests that by using heart rate response and treadmill exercise score, exercise tests can be used as a powerful marker of risk even in healthy patients," it said.

"Patients with intermediate to high risk treadmill exercise scores were found to have even higher mortality if abnormal heart rate recovery was also present," the report said. "Patients with both low risk treadmill exercise scores and normal heart rate recovery had very low risk of death."

Together, heart rate recovery and treadmill exercise scores appeared to be complementary, strengthening the predictive value of exercise stress testing, it said.

Michael Lauer of the clinic's Department of Cardiology, said exercise testing, commonly used for decades, appeared to be more valuable than the electrocardiogram, which measures the electrical impulses that immediately precede contraction of the heart muscle, providing a look at how the heart is operating.

"When the exercise test is interpreted correctly it may well be one of the most powerful and cost-effective measures of health we have," Lauer said in a statement.

He said the clinic found the electrocardiogram tracings were "the least useful piece of information obtained."

"Our findings, along with those of researchers at other institutions, suggest that it is time that we radically change the way we read exercise tests, and in that way better serve our patients," Lauer said.

(From China Daily)