(AP) - Doctors who use treadmill tests to diagnose heart disease could better predict the risk of death if they paid more attention to what happens to a patient's heart after he or she steps off the treadmill, a large study found.
Treadmill tests are given to millions of Americans each year. Their hearts are analyzed while they walk at a steadily increasing pace. But doctors concentrate almost entirely on what happens while the patient is actually exercising.
The decade-long study of more than 29,000 patients showed that the presence of irregular heartbeats in the minutes after a treadmill test is a better indicator of death within five years than irregular heartbeats during the test itself.
Experts predicted the findings will lead doctors to focus more on the way the heart recovers from a workout.
An irregular heartbeat after exercise on the treadmill "will be considered a marker of risk," said Dr. Daniel M. Shindler, a cardiologist at Robert Wood Johnson Medical School in New Jersey. "Before, it was not clear."
That information could, in turn, help doctors decide which patients need invasive testing, aggressive treatment and close monitoring.
The study was reported in Thursday's New England Journal of Medicine.
Cardiologists at the Cleveland Clinic found that 11 percent of patients with irregular heartbeats after a stress test were dead within five years, compared with 5 percent of those who did not have such irregular rhythms.
Nine percent of patients with irregular heartbeats during the test itself died within five years, compared with 5 percent who did not have irregular beats during the exercise.
"What we're showing is that plain old, simple exercise tests that people have been doing for decades can show evidence of problems that identify people who are at risk of death," said Dr. Michael S. Lauer, director of clinical research in cardiac medicine at the Cleveland Clinic.
The irregular heartbeats, called ventricular ectopy, are caused by a disturbance in the heart's electrical system. Such irregular beats are not uncommon, but they usually disappear soon after a person stops exercising.
Three percent of the study patients had those irregular beats only during exercise, 2 percent had them only during recovery and 2 percent had them during both periods.
"I think Lauer and other people who are working on this are appropriately refocusing us" on irregular beats after the tests, said American Heart Association spokesman Dr. Richard Stein, the chief of cardiology at Brooklyn Hospital Center. "I think it's a very important piece of information for a doctor to have."
Over an average follow-up of 5.3 years, 1,862 of the 29,244 patients died. The study included deaths from all causes.
In a typical heart stress test, a person walks on a treadmill, with the pace gradually increasing to the patient's maximum endurance. Meanwhile, the person's blood pressure, pulse rate, electrical activity of the heart and any signs of inadequate blood flow through the heart are all monitored and recorded.
Treadmill tests have been around for five decades and are still widely used, despite the growing popularity of more expensive and sophisticated heart imaging techniques.
Each year, heart disease kills about 950,000 Americans, and heart attacks hospitalize 1.5 million Americans.
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