ETT Probability & Accuracy in Heart Disease

Doctors disagree about the value of exercise tolerance testing (ETT,) also known as stress testing, as a predictor of coronary disease and heart attacks. Competing studies offer conflicting evidence about the usefulness of ETT results, particularly in patients who are asymptomatic. It is estimated that about two million American men have significant coronary artery obstructions but no symptoms, a condition known as silent myocardial ischemia.

Usefulness Questioned

• For many years, the chest pain associated with angina pectoris was believed to accurately signal the likelihood of coronary heart disease. However, in a study that appeared in the December 1991 issue of the Archives of Internal Medicine, P.C. Deedwania estimated that more than 75 percent of those with coronary artery obstruction experienced no angina or angina-like symptoms. The study also observed that "that most silent ischemic episodes occur during minimal or no physical exertion," a finding that calls into question the usefulness of ETT as a predictor.

Usefulness Affirmed

• A positive take on ETT's predictive value emerged from a study that appeared in the 1986 issue of Circulation, a journal published by the American Heart Association. That study, which reviewed the ETT results of more than 3,600 white men, concluded that a positive ETT test---defined as a depression of at least 1 mm in the ST segment of the electrocardiogram reading---was a more accurate predictor "of cardiovascular death than were high plasma levels of low-density lipoprotein cholesterol, low plasma levels of high-density lipoprotein cholesterol, smoking, hyperglycemia or hypertension."

No Conclusion

• Researchers from the University of North Carolina and RTI International, a North Carolina-based research institute, studied the value of ETT in "identifying asymptomatic patients at high risk for coronary heart disease events." The study, undertaken to provide guidance for the U.S. Preventive Services Task Force, focused on a review of existing findings and failed to reach a definitive conclusion on the usefulness of ETT data. The researchers observed: "Although screening exercise tolerance testing detects severe coronary artery obstruction in a small proportion of persons screened and can provide independent prognostic information about the risk for coronary heart disease events, the effect of this information on clinical management and disease outcomes in asymptomatic patients is unclear."

More Doubt

• A French study, published in the August 2009 issue of Atherosclerosis, concluded that ETT had a "doubtful utility" in the detection of latent coronary heart disease but suggested it may help to predict future heart disease.

Bottom Line

• In view of the inconclusive findings about the accuracy of ETT in predicting future heart disease and even identifying existing heart disease of the silent variety, ETT should be combined with other cardiac diagnostic tests to produce the most accurate results. Other such tests include echocardiography, computed tomographic (CT) scans, and coronary angiography.