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Are the guidelines wrong? In 2002, should cardiac stress testing always include some type of imaging? (Pro & Con).


Here's a quick multiple-choice quiz: Why do physicians still perform treadmill exercise ECGs?

A. Tradition, which means old habits.

B. Convenience, which means intellectual apathy.

C. Concern about capital expenditure, which means miserliness.

D. Secondary gain--the enormous number of false-positive exercise stress tests generates lots of trips to the catheterization laboratory for coronary angiography, which is good for business.

E. All of the above.

The correct answer, of course, is E.

I think the American College of Cardiology--American Heart Association guidelines on the evaluation of patients with stable angina are wrong in stating that exercise stress testing is often sufficient and that stress imaging isn't always necessary.

The treadmill exercise ECG has only a mediocre positive predictive value. And its high false-positive rate means that even though an exercise stress test costs less than a cardiac imaging study, the ultimate cost is actually higher, since in routine clinical practice, most patients with an ECG abnormality are sent to the catheterization laboratory, even if they are at low risk of disease.

Overreliance upon the exercise stress test has gotten us into a lot of trouble. In women, it has resulted in creation of a disease--the so-called syndrome X. You take a 50-year-old woman who presents with chest pain but with no coronary risk factors and a low probability of coronary artery disease, you subject her to a stupid test--the exercise ECG--and when the test is read as positive, she goes on to angiography which shows normal coronary arteries. Voila, a disease is born. A thousand papers are published on syndrome X, a disease created by the exercise ECG's high false-positive rate in low-risk patients

A recent study from Cedars-Sinai Medical Center in Los Angeles and the Atlanta Cardiovascular Research Institute involving 3,058 consecutive patients with a normal resting ECG who underwent exercise dual-isotope single-photon emission computed tomography demonstrated that stress imaging yielded incremental prognostic value and enhanced risk stratification in a cost-effective manner (Circulation 105[7]:823-29, 2002).

Invest in cardiac imaging: nuclear, echo, or MRI. After all, direct visualization of the heart's perfusion function during stress provides invaluable insights in individual patients.

Dr. Sanjiv Kaul is professor of internal medicine and director of the cardiac imaging center at the University of Virginia, Charlottesville.


I'll readily concede that stress imaging adds prognostic value beyond that of the exercise treadmill test. But it's extremely cost ineffective to use stress imaging routinely. I can name two important subgroups where there is clear evidence of this: patients who have a low clinical likelihood of coronary artery disease and those with a normal resting ECG who are not on digoxin.

In these populations, a negative treadmill test confers a very low chance of significant coronary artery disease--roughly 4%. A negative imaging study further reduces this risk to 2%-3%, but it can't drive it to zero. And the cost of this clinically insignificant prognostic refinement is exorbitant.

For example, what my debate opponent failed to mention about the Cedars-Sinai study was that the investigators concluded that routine stress perfusion studies were cost effective only in the subgroup of patients with an intermediate to high likelihood of coronary artery disease--15% or greater--based upon their exercise treadmill test results.

This subgroup comprised 50% of the 3,058 patients with a normal resting ECG. In this subgroup, the cost per hard clinical event predicted by an abnormal scan was a very reasonable $25,134.

However, in the other 50% of patients with a normal resting EGG--those with a low preexercise treadmill test likelihood of coronary disease or an intermediate to high pretest likelihood but a low posttreadmill likelihood of disease--the cost per hard event potentially avoidable as the result of an abnormal scan was $147,000-$211,470. And that's just the cost for the imaging studies; adding in the expenditures for angiography and revascularizarion procedures would drive the cost considerably higher. In a world of limited health care dollars, this kind of expenditure is indefensible.

The ACC-AHA guidelines rate the exercise ECG for the evaluation of chest pain as a class I procedure--that is, supported by convincing evidence of usefulness and effectiveness. Stress perfusion imaging and stress echo receive a less favorable class IIb rating.

Physicians have a choice: We can either follow practice guidelines developed by responsible medical organizations, or we can live with arbitrary judgments by third-party payers that are usually made on purely economic grounds by somebody with an MBA degree. So let's get with the guidelines.

Dr. Raymond J. Gibbons is professor of medicine at the Mayo Medical School, Rochester, Minn.
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Publication:Internal Medicine News
Geographic Code:1USA
Date:Jul 1, 2002
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