More than an annoyance: breathlessness could be sign of bigger problems.

Everyone runs out of breath from physical exertion. But for people with a condition called dyspnea, even a minor effort makes breathing difficult. A new study suggests that these people are at greater risk of dying of heart problems or other ailments than are people who have chest tightness, a well-known sign of cardiac trouble.

Beginning in 1991, a team led by cardiologist Daniel S. Berman of Cedars-Sinai Medical Center and the University of California, Los Angeles identified more than 1,000 patients diagnosed with dyspnea but who had no history of a heart problem. Other doctors had ruled out asthma or other lung problems in these patients and referred them to the cardiologists for testing.

Berman's team also identified much larger groups of people with angina--chest tightness that can signal an obstructed coronary artery--and of other patients referred for possible heart problems. Most of the patients were in their 60s or 70s.

The researchers gave each person a stress test to measure how well his or her coronary arteries were delivering blood to the heart muscle. After the stress tests, the team removed from the study patients who had a serious coronary blockage, assigning them to treatment that would open or bypass problem vessels.

Among the others, the test revealed some loss of heart function in about one-third of the dyspnea patients and in nearly half of the angina patients. Fewer people in the other group showed any loss.

Over nearly a decade, the researchers tracked 17,991 of the patients for an average of 2.7 years. Of the patients with dyspnea but no sign of coronary artery disease during the stress test, 2.3 percent died annually of cardiac problems during the follow-up years. That made them more than twice as likely to die of cardiac problems as were similar participants with angina.

Among people whose stress tests had revealed some coronary-vessel disease but not a blockage serious enough to warrant surgery, the dyspnea patients were three times as likely to die of cardiac problems during the follow-up years as the angina patients were, the researchers report in the Nov. 3 New England Journal of Medicine.

The dyspnea patients were also more likely than those in other groups to die of problems not linked to the heart. Their risk of death remained higher even when the researchers took into account such factors as a history of diabetes.

The findings match those of a smaller study reported in the June 16, 2004 Journal of the American College of Cardiology by Patricia A. Pellikka, a cardiologist at the Mayo Clinic College of Medicine in Rochester, Minn., and her colleagues.

Together, Pellikka says, the reports are a wake-up call for family practitioners. "Patients who come into the office with unexplained shortness of breath that occurs with exertion deserve cardiac evaluation and some kind of stress test," she says.

In Berman's study, people with dyspnea were more likely than the others to have an enlarged left ventricle, the main pumping chamber of the heart. In elderly people, such an enlargement is a sign of chronic stress on the heart that weakens it and increases susceptibility to heart failure.

Even so, Berman and Pellikka concur that the biological link between difficult breathing and increased risk of death remains unclear.

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