Study examines exercise testing in asymptomatic patients after coronary revascularization

Asymptomatic patients who undergo treadmill exercise echocardiography (ExE) after coronary revascularization may be identified as being at high risk but those patients do not appear to have more favorable outcomes with repeated revascularization, according to a report published Online First by Archives of Internal Medicine, a JAMA Network publication. The article is part of the journal's Less is More series.

Cardiac events and recurrent ischemia (a temporary shortage of oxygen caused by impaired blood flow; identified in the study as new or worsening cardiac wall motion abnormality shown on the echocardiogram) are common after revascularization procedures, both percutaneous coronary intervention (PCI) and coronary bypass graft surgery (CABG).

Guidelines of the American College of Cardiology/American Heart Association recommend evaluation with stress imaging tests, including ExE, in symptomatic patients after revascularization, but evaluating asymptomatic patients "is more controversial," the authors note in the study background.

"Testing is considered inappropriate early after PCI (<2 years) and CABG (<5 years), but the justification for these cutoffs is ill defined," the study notes.

Serge C. Harb, M.D., and colleagues at the Cleveland Clinic Heart and Vascular Institute, Ohio, examined the effectiveness of testing asymptomatic patients early and late postrevascularization. Their observational study was conducted with data from asymptomatic patients with a history of PCI or CABG who were referred for ExE at the Cleveland Clinic from January 2000 through November 2010.

ExE was performed in 2,105 asymptomatic patients (average age 64; 310 were women; 845 [40 percent] had a history of myocardial infarction [heart attack]; 1,143 [54 percent] had undergone PCI and 962 [46 percent] had undergone CABG an average of 4.1 years before the ExE).

Ischemia was detected in 262 patients and 88 of them underwent repeated revascularization. A total of 97 patients died over an average followup period of 5.7 years, and death was associated with ischemia in groups tested both early (less than two years after PCI or less than five years after CABG) and late (two or more years after PCI, or five or more years after CABG), according to the study results. The main predictor of outcome appeared to be exercise capacity, "suggesting that risk evaluation could be obtained from a standard exercise test rather than exercise echocardiography," the authors note.

"In conclusion, the results of this study suggest that asymptomatic patients who undergo treadmill ExE after coronary revascularization may be identified as being at high risk but do not seem to have more favorable outcomes with RVs [repeated revascularization]," the authors conclude. "Given the very large population of post-PCI and post-CABG patients, careful consideration is warranted before the screening of asymptomatic patients is considered appropriate at any stage after revascularization."

In an invited commentary, Mark J. Eisenberg, M.D., M.P.H., of McGill University, Montreal, Canada, writes: "A strategy of routine periodic stress testing in asymptomatic patients following coronary revascularization is associated with high rates of resource utilization and high costs. Most positive test results using such a strategy will be false-positives and will lead to further testing and additional angiographic procedures."

Eisenberg continues: "Despite the fact that current evidence discourages the use of routine testing, this strategy is still commonly observed in practice. Thus, the time has arrived for a large, well-controlled trial randomizing asymptomatic patients postrevascularization to routine periodic stress testing vs. conservative management."

"Until well-supported data become available supporting such a strategy, routine testing in asymptomatic patients is probably not worth the effort," Eisenberg concludes.