Rethinking the Treadmill Test 

Study finds heart function after treadmill test is best measure of risk 

A recent study proposes what could be a revolutionary change in the way cardiologists look at exercise testing: It is what happens after the patient stops exercising that is really important.

Current treadmill testing focuses on "whether the ST segment [part of the electrocardiogram] is depressed during exercise," says Dr. Michael S. Lauer, lead author of a paper on the study in a recent issue of The New England Journal of Medicine.

"In fact, that is the least important item. How much the heart rate comes down after exercise, whether there is ventricular ectopy, [abnormal heartbeats], is a far stronger indicator of risk than what happens to the ST segment," say researchers.

The study looked at almost 30,000 patients who underwent exercise testing, either because they had coronary artery disease or were suspected of having it.

As is customary, the testers kept the heart monitor on for a few minutes after the person came off the treadmill to be certain the patient is not in trouble.

However, in this trial the researchers looked closely at the results of heart monitoring, recording not only abnormal heartbeats but also how quickly the heart rate returned to normal. Then they looked at the number of cardiovascular deaths in the group, and how those deaths were related to what happened after exercise.

Exercise Test Does Not End When Patient Stops Exercising

"The key message here is that the exercise test does not end when the patient stops exercising," Lauer says. "During the first few minutes after exercise, you can gather some extremely valuable data."

As expected, occurrence of abnormal heartbeats during exercise increased the risk of death over the next five years; the death rate for patients who had those abnormalities was 9 percent, compared to 5 percent for those who did not.

However, the occurrence of abnormal heartbeats in the minutes after testing was an even stronger indicator of risk: 11 percent of the patients with those abnormalities died in the follow-up period.

"This is a very important finding in terms of being able to assess the risk of patients," says Dr. Richard A. Stein, a spokesman for the American Heart Association. He is more cautious about the implications of the study than Lauer, but does say "it could be revolutionary."

Cardiologists will not stop looking at what happens during exercise, Stein adds, but they will start paying more attention to the minutes after exercise.

"We would look at that and integrate the information into the various ways we assess risk," says Stein, who is a clinical medicine professor at Weill-Cornell Medical Center in New York City.

Study Implications Remain to be Seen

It remains to be seen how the finding will be integrated into medical practice, Stein says. Most probably, cardiologists will concentrate even more on controlling the known risk factors in patients whose after-exercise electrocardiograms are abnormal.

"It will refocus our attention in exercise testing," he adds.

Always consult your physician for more information.

Reasons a Treadmill Test May Be Ordered

An exercise echocardiogram, performed after you have exercised on a treadmill or stationary bicycle, may be performed for the following reasons:

• to determine limits for safe exercise in patients who are entering a cardiac rehabilitation program and/or those who are recovering from a cardiac event, such as heart attack or heart surgery
  

• to assess leg pain with exercise (also called intermittent claudication) in patients with suspected occlusion in the legs' circulatory system
  

• to evaluate blood pressure during exercise
  

• to assess stress or exercise tolerance in patients with known or suspected coronary artery disease
  

• to evaluate the cardiac status of a patient about to undergo surgery

Online Resources

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American Heart Association

National Heart, Lung, and Blood Institute (NHLBI) 

National Institutes of Health (NIH)

The New England Journal of Medicine

March 2003

Study Finds Heart Function After Treadmill Test Is Best Measure of Risk 

Exercise Test Does Not End When Patient Stops Exercising

Study Implications Remain to be Seen

Reasons a Treadmill Test May Be Ordered

Lower Dose of Anti-Clotting Drug Saves Lives  

Online Resources 

In Other News About Your Heart Health:

Lower Dose of Anti-Clotting Drug Saves Lives 

Reduces recurrence of deep vein thrombosis 

The dosage of an anti-clotting drug given to people with deep vein thrombosis can be lowered substantially without reducing its effectiveness.

That is the finding of a trial study on warfarin (also known as Coumadin) that was cut short because of its impressive results.

The trial results will be published in a recent issue of The New England Journal of Medicine. However, the journal says the results are being made available to physicians now "because of the study's therapeutic implications."

This "is going to save a number of lives," says study leader Dr. Yves Rosenberg, a project officer at the National Heart, Lung, and Blood Institute (NHLBI), part of the National Institutes of Health (NIH), which funded the research.

Too little warfarin, a blood thinner, can lead to recurrent blood clots that at the least cause severe discomfort and at worst kill the patient by going to the lungs and blocking the pulmonary artery. On the other hand, too much of the drug can cause bleeding that, at worst, occurs in the brain and can be fatal. As many as 60,000 Americans are killed each year by these pulmonary embolisms, Rosenberg says.

The standard treatment for patients suffering from an episode of deep vein thrombosis or pulmonary embolism is five to 10 days of heparin, a clot preventer given by injection, followed by three to six months of a relatively high dose of warfarin designed to produce a blood-clotting level of 2.0 to 3.0 in what is called the international normalized ratio (INR). In the study, some patients were given low doses of warfarin, just enough to achieve an INR of 1.5 to 2.0—an apparently small difference, but very important clinically. Others were given a placebo.

In an average follow-up of more than four years, only 14 of the 255 patients getting low-dose warfarin had another episode, compared to 37 of the 253 placebo patients—a reduction of 64 percent. There were four deaths in the low-dose warfarin group and eight in the placebo group, a reduction of nearly half.

Just as important, the incidence of bleeding complications in both groups was similar, the researchers report. This means patients can be kept on low-dose warfarin for much longer than is now done, which gives them longer-term protection. "Long-term, low-intensity warfarin therapy can be readily implemented in clinical practice," the report says.

Other studies will be done to see whether the warfarin dose can be reduced even further, Shafer says. However, what is really needed, he says, is a new kind of anti-clotting drug that can distinguish between harmful clots and the kind the body produces normally in response to injury. Until that comes along, he says, "we will continue to walk the tightrope of anticoagulant dosing."

Always consult your physician for more information.