Heart screening tests—just say no

Healthfacts, March, 2004

The U.S. Preventive Health Services Task Force recently updated its heart disease screening recommendations. They will, no doubt, disappoint many practicing physicians, especially the entrepreneurial radiologists who have been selling the relatively new idea of having routine heart scans. Screening, by definition, describes tests that are given to people free of apparent disease.

The Task Force on Screening for Coronary Heart Disease assessed all relevant research to determine whether early detection of heart disease in symptom-free people would reduce their odds of dying of heart disease or having a heart attack. Unfortunately, there wasn't much evidence to assess. Worse, the Task Force concluded that there is probably more harm caused by the inevitable false alarms. The potential harms of screening, according to the Task Force, are unnecessary invasive testing (e.g., coronary angiography); "mislabeling" people as having heart disease because of erroneous test results; and unnecessary treatment, e.g., drugs and/or surgery.

The Task Force looked at the most common screening tests: resting electrocardiography (ECG), exercise treadmill test and heart scanning for the presence of calcium or constrictions in the coronary arteries. One study cited by the Task Force found that most of the abnormal results that show up on the ECGs given people at low risk for heart disease are meaningless. 71% of those with abnormal results from treadmill testing went on to have an angiography that found nothing of significance. (Angiography carries a small risk of death.) No research has been done to determine whether heart scans can predict a heart attack or stroke.

Sometimes the tests find nothing amiss in people with heart disease. "Due to the limited sensitivity of resting ECG and the low prevalence of coronary heart disease in asymptomatic adults, a majority of coronary heart disease events will occur among those with an initially normal ECG. Exercise treadmill testing can be normal or non-diagnostic in a large proportion of patients who will go on to have a coronary heart disease event, which may be explained partly by the fact that many acute coronary events results from sudden occlusion of a previously unobstructed artery segment."