Exercise Testing Predicts Heart Risk
Excerpt by Steven Reinberg, HealthDay

Exercise testing not only helps predict a person's risk of death, but it can also help rule out those who don't require aggressive treatment for cardiovascular disease, a study says.

The stress test is a good gauge independent of another test, angiography, which looks for diseased arteries, the study says.

"We found that cardiac exercise testing is a good predictor of death. It is also a very good predictor of people at low risk who do not need aggressive treatment," says Dr. Michael S. Lauer, a cardiologist with the Cleveland Clinic Foundation.

Lauer and his colleagues collected data on 2,935 patients suspected of having heart disease. The patients underwent exercise testing followed by an angiogram. The results appear in the current issue of the Journal of the American College of Cardiology.

During exercise testing, patients walk on a treadmill while their heart rate and blood pressure are measured. During the test, the degree of difficulty is steadily increased as the incline of the treadmill is raised. Speed is also increased until the patient is out of breath or until the heart rate reaches a predetermined level.

The object of the test is to see how well the patient's heart performs under stress. The test has been used for years to uncover heart disease.

This group of patients also underwent angiography, an invasive procedure during which a catheter is placed in the coronary arteries, letting doctors see if any arteries are blocked.

The researchers found that 421 of the patients had severe heart disease, but 838 patients had abnormal heart rate recovery after exercise testing. Lauer's team followed all the patients for six years.

During that time, 336 patients (11 percent) died. Heart rate recovery was a stronger predictor of risk than the severity of coronary disease, Lauer says.

Lauer believes that measuring heart rate recovery is different from just looking at heart disease. Measuring heart rate recovery is assessing autonomic nervous system function, which is different from how much blockage there is in a coronary artery, Lauer notes. He adds this is what makes heart rate recovery an independent predictor of death.

The most important aspect of this finding, Lauer says, is that exercise testing can be used to identify patients who are at low risk for heart disease.

"Using exercise testing to identify those at low risk for heart disease is a cheap, effective way to identify those who do not need aggressive treatment," Lauer says.

Because doctors are too cautious, many patients are classified as at uncertain risk for heart disease, he notes. These patients receive unnecessary tests and medications.

Normal heart rate recovery, along with preserved functional capacity, can identify patients at low risk. Given this finding, "patients can be assured that exercise is an adequate tool for assessing heart disease," he adds.

However, Dr. Bernard Chaitman, a professor of medicine and director of cardiovascular research at St. Louis University School of Medicine and author of a journal editorial, comments that the implications of abnormal heart rate recovery are unclear.

Chaitman believes the abnormal heart rate recovery is a marker of autonomic dysfunction. "When people exhibit this, it somehow predisposes them to heart rhythm disturbances that lead to death," he says. "But the unanswered question is why."

"If we knew why people had abnormal heart rate responses to exercise, then maybe we could develop treatments to reduce the mortality rate," Chaitman adds. "Right now we don't know if treating them in any special way will reduce the mortality rate."

Chaitman also does not believe that having normal heart rate recovery alone is necessarily a sign of reduced cardiac risk. Risk needs to be determined in the context of their pretest risk factors as well as the results of their exercise test, he argues.

Chaitman advises that "if your heart rate responses to exercise are abnormal, you should want to know more as to why and what it means, and you should consult your physician."

Another study in the same journal issue finds a new benefit from regular exercise. European researchers have found exercise significantly reduced markers of inflammation in patient with chronic heart failure.

"For patients with stable chronic heart failure, regular aerobic exercise training should not be regarded as rehabilitation only, but as a continuing treatment with the potential to modify the underlying disease process," Dr. Stephan Gielen, from the University of Leipzig Heart Center, says in a statement.

In the study, 20 men with stable heart disease were randomly selected to undergo an exercise program or be placed in a control group. The 10 men in the exercise group did 20 minutes of exercise a day, either on a stationary bicycle or in a group workout.

When the researchers evaluated these men after six months of exercise, they found that not only was there a 29 percent increase in peak oxygen uptake, but that key inflammatory markers, namely tumor necrosis factor-alpha, interleukin-6, interleukin 1-beta, and nitric oxide synthase were significantly reduced in thigh muscle.

"Exercise acts as an anti-inflammatory intervention in the skeletal muscles in chronic heart failure. This is especially important because inflammatory cytokines have been linked to so-called cardiac cachexia, a chronic debilitating wasting process which affects many heart failure patients and leads to severe reduction in muscle mass and muscle strength. It may therefore be hoped that training could also help to prevent this catabolic process," Gielen says.

Many people with heart failure complain of fatigue. And in patients with severe heart failure, muscle-wasting, or cachexia, can occur. The conventional wisdom has been that these problems result from poor blood circulation.

Research has not found a connection between the ability of the heart to pump blood and fatigue levels or the ability to exercise. However, studies have shown that in patients with heart failure, there is a general inflammatory response coupled with a disruption of energy metabolism and an increase in cell death in thigh muscles.

Although there is no current anti-inflammatory treatment for heart failure patients, exercise might be a good option, Gielen says. However, he notes that long-term studies are needed to confirm that cardiac cachexia can be effectively prevented by exercise.

Dr. Douglas Mann, from the Houston Veterans Administration Medical Center and a professor of medicine at Baylor College of Medicine, co-authored an accompanying editorial and comments that the findings by Gielen's team "are provocative but not definitive."

The results of the study seem to indicate that exercise is good for patients with heart failure and may improve their fatigue, Mann says. "The finding may also open up the field for novel therapeutic interventions that might be designed to reduce skeletal muscle inflammation and improve [the] patient's hematology in heart failure."

Mann concludes that "exercise programs are beneficial in heart failure and may be the mainstay of therapy for reducing fatigue."

More information

Read more about the exercise stress test from MedlinePlus. Meanwhile, the American Heart Association has a primer on heart failure.

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