A treadmill stress test can predict heart attacks or other serious heart disease even in men without symptoms, U.S. researchers reported. The findings, published in the journal Circulation, suggest that exercise tests may be able to help predict which men who already appear to have a moderate to high risk of heart disease really need to take care. One of the two studies showed exercise tests may be used to judge who would receive an implanted pacemaker-like device called a defibrillator, researchers said. In one study two measurements -- a change in electrocardiogram or ECG tracing called ST-segment depression and an inability to reach target heart rate -- more than doubled the 10-year risk of coronary events such as heart attacks. Men who did well on the stress test had a lower-than-expected rate of heart attack and serious heart disease in the 10 years following. "Our results suggest that exercise testing may be of benefit in asymptomatic men with intermediate to high risk," said Dr. Gary Balady, a professor of medicine at Boston University School of Medicine. His team tested women, too, but so few women developed heart attacks or serious heart disease that they could not decide if the test was a good predictor for women. The 1,431 men and 1,612 women were taking part in a bigger study called the Framingham Heart Study. They were 45 years old at the start on average and had been followed for more than 18 years. The volunteers got a battery of tests when they began the study that included the stress test. In the 10 years following 224 men, or 15.7 percent, had chest pain, a heart attack or died from coronary heart disease. Overall, there was a 9.6 percent risk of heart attack, chest pain or other serious heart disease for the 3,000 people in the study over 10 years. The men who had the highest predicted risk anyway, based on cholesterol levels, high blood pressure, family history and other factors, were the most likely to have serious heart disease if they also did poorly on the stress tests, the researchers found. They said such patients should get aggressive care, including drugs to lower blood pressure and cholesterol. A second study in Circulation, done at Columbia University Medical Center, found that an exercise test looking for a certain heartbeat pattern, called a Microvolt T-Wave Alternanscan or MTWA, also shows who may benefit from an implantable defibrillator device. "It's an exercise test with a smart computer," said Dr. Thomas Bigger, who led the study. Every year 300,000 to 400,000 people in the United States die suddenly when the heart's rhythm is suddenly disrupted. But there is controversy over how to decide who needs defibrillators implanted to prevent this, and debate over whether Medicare and other insurers should use certain tests to qualify patients for payment. Medicare only pays if patients have an abnormal QRS test, but the Columbia team say the MTWA test is more accurate. They tested 177 patients and followed them for an average of 20 months. Three percent of patients identified as high-risk by the MTWA died during that time, compared with 12 percent identified as low-risk by the QRS test. The researchers noted that the test could also show who would not be helped by a defibrillator, potentially saving money and trouble.