Too little evidence for ECG heart screening: panel

NEW YORK Tue Sep 20, 2011 3:34pm EDT

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NEW YORK (Reuters Health) - Although some doctors use electrocardiograms to screen symptom-free people for heart disease, there is too little evidence that it does any good, an expert panel said Monday.

An electrocardiogram (ECG) is a fairly simple test that uses electrodes placed on the skin to record the heart's electrical activity while a person is at rest, or walking on a treadmill or pedaling an exercise bike. ECGs -- sometimes called EKGs -- have long been used to help diagnose heart disease in people with chest pain or other potential symptoms of heart trouble.

But doctors may also recommend an ECG to people who are free of symptoms -- often because they have multiple risk factors for heart disease, like high blood pressure, diabetes or smoking.

That is despite a lack of evidence that such screening is useful, however.

In 2004, the U.S. Preventive Services Task Force (USPSTF), an expert panel supported by the federal government, recommended against ECG screening for people at low risk of having heart disease. It also said there was "insufficient evidence" to recommend screening even for people at higher-than-normal risk.

And nothing has changed since then, according to the USPSTF's latest report, published in the Annals of Internal Medicine.

A key issue, according to the panel, is that no clinical trials have looked at whether ECG screening actually heads off heart attacks or other complications -- or prolongs people's lives.

There are studies showing that certain abnormal ECG results can predict an increased risk of heart trouble down the road.

But that's not enough, according to the USPSTF panel, which was headed by Dr. Roger Chou of Oregon Health and Science University in Portland.

An expert not involved in the panel's review agreed.

"There's a general belief that prediction means prevention," said Dr. Michael S. Lauer of the National Heart, Lung, and Blood Institute, who wrote an editorial published with the report.

"But we see, over and over again, that this is not necessarily true," Lauer said in an interview. He pointed to ovarian cancer as an example. A recent study of nearly 70,000 women found that annual screening for ovarian cancer -- using blood tests and ultrasound -- made no difference in women's risk of dying from the disease.

And more than 1,000 women ended up having unnecessary surgery because they had a so-called false positive result on the screening test but did not actually have ovarian cancer.

The message for patients and doctors, according to Lauer, is that we should wait for evidence that the benefits of screening actually outweigh the risks.

"There's a general impression that having more information (from screening tests) must be a good thing, and having information earlier must be better," Lauer said. "Sometimes that's true, but sometimes it's not."

Screening also costs money, of course. An ECG typically costs about $50, while an ECG done during exercise (called an exercise stress test) generally runs between $200 and $300.

Until there is evidence that ECG screening actually brings real benefits to patients, it should not be used, Lauer said.

So why is that evidence still lacking? One major reason, according to Lauer, is there are no specific therapies for the types of problems that would show up on an ECG.

It makes sense to screen people for high blood pressure and high cholesterol because there are effective treatments for both that do make a difference in your risk of heart problems.

"But we don't have specific treatments for many, if not most, of the abnormalities we would find on (an) electrocardiogram," Lauer said.

Until such therapies become available, he writes in his editorial, "it is hard to contemplate what trials would have a reasonable chance for success."

Along with the lack of clear benefits, there are also risks.

Screening, by definition, means testing apparently healthy people. Like any kind of screening, ECG can suggest problems where there are none, which in turn can lead to more-invasive testing or treatments that are unnecessary.

"That's a real harm," Lauer said.

People who have a positive ECG result may undergo angiography, where a catheter is threaded through a blood vessel to the heart, to allow for special X-ray images that can show blockages.

The risk of serious complications is low, but real. According to Chou's team, studies suggest that 0.4 percent of people who undergo angiography suffer a heart rhythm disturbance, 0.05 percent have a heart attack, and 0.1 percent die.

Lauer suggested that if your doctor recommends ECG screening -- or any type of screening test -- you should ask why you need the test and what will be done if you have a positive result.

That does not, however, apply to people who have possible symptoms of heart disease, like chest pain or breathing difficulties. In that case, an ECG would be considered a diagnostic test, not a screening test.

"Electrocardiography is a very powerful test when used in the proper setting," Lauer said.

But as far as screening, the value of ECG remains up in the air, according to the USPSTF.

The panel is not alone in that view. Lauer noted that the American College of Cardiology and American Heart Association recently gave ECG screening a "lukewarm, at best" recommendation.

SOURCE: bit.ly/ng9goJ Annals of Internal Medicine, September 20, 2011.

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