Is Routine Functional Testing √Öfter Coronary Bypass Surgery Worthwhile?

In the current issue of the Journal, Eisenberg and colleagues present their interesting findings from the ROutine versus Selected Exercise Treadmill Test after Coronary Artery Bypass Graft (ROSETTA-CABG) Registry.¹ The purpose of this study was to examine the clinical utility of routine functional testing in otherwise asymptomatic patients who have undergone prior coronary bypass surgery. Although coronary bypass grafting has been shown to substantially improve survival in certain patient subsets² and to provide meaningful relief of angina in many others,³ it is well known that it is hardly a cure for coronary artery disease.⁴ Over time, patients with prior coronary bypass grafting surgery suffer from saphenous vein graft disease⁵ or progression of native disease, either of which can lead to recurrent angina, myocardial infarction, or fatal outcome. For this reason, many clinicians routinely obtain exercise testing with or without imaging in post-bypass surgery patients in order to identify those patients who might be at increased risk for major life-threatening clinical events.⁶ The thinking behind this approach is that functional testing may identify people who are at higher risk and who therefore may benefit from aggressive medical or mechanical intervention.^6,7 The investigators followed the progress of 395 patients who were enrolled in the registry. Most (284 or 72%) underwent a selective functional testing strategy, whereby functional testing was only obtained in the presence of clear clinical indications. The remainder underwent routine functional testing within the first year after CABG. The investigators found that the patients who underwent routine functional testing underwent fewer follow-up cardiac catheterizations and tended to undergo fewer percutaneous, coronary interventions. They also tended to have fewer clinical events, but the absolute number of clinical events was so small that no definitive conclusions could be reached. The authors concluded that as functional testing after bypass surgery is associated with very low event rates, the strategy is not appropriate. What are we to make of the practice of obtaining routine functional testing in asymptomatic patients who have undergone coronary bypass grafting?⁷ There is literature showing that abnormal functional test results in such patients do predict a higher likelihood of death or myocardial infarction.^6,8 Furthermore, this appears to be particularly true when testing is obtained during the first few years after bypass surgery⁶, presumably a time when the accelerated atherosclerosis of saphenous vein graft disease is more likely to be a problem. Given our wide array of available medical therapies and improving techniques in interventional cardiology, wouldn’t it just make sense to identify those people who are likely to get into trouble and intervene before major clinical events happen? Although such a strategy seems intuitive, it is not at all clear that it, in fact, will improve clinical outcome. In some respects, the practice of obtaining routine functional testing in asymptomatic post-CABG patients is no different than the practice of screening for asymptomatic disease. The same general principles that apply to identifying screening tests that are likely to be worthwhile (the capacity to identify and effectively treat a sizable high risk cohort)⁹ also apply to screening for increased risk in post-CABG patients. As has been discussed elsewhere, observational analyses of patients undergoing or not undergoing screening are seriously biased.¹⁰ The approach is also seriously hampered by lack of data supporting a reduction in hard endpoints (death, MI) by repeat revascularization. The only way to really know whether or not a screening strategy improves outcome is by performance of randomized trials. These trials are difficult to carry out because low event rates mandate high sample sizes. Furthermore, one may not have control over how abnormal test results are handled by individual clinicians, muddying the waters even further. Randomized trials for screening studies have been successfully performed in a variety of non-cardiovascular areas, such as the performance of mammography for identifying women with early breast cancer.¹¹ In cardiovascular disease, large-scale, randomized trials have been carried out for evaluating the value of screening for abdominal aortic aneurysms.¹² These trials have led to evidence-based recommendations favoring routine screening for abdominal aortic aneurysms in certain patient subsets.^12,13 In the realm of coronary artery disease, however, there have been no large-scale, randomized trials showing that noninvasive imaging or functional testing in any setting, let alone after CABG, improves outcome. There has been a marked increase in interest and direct-to-consumer marketing for coronary artery screening tests,¹⁴ by unfortunately all this has occurred in the absence of any evidence showing that any type of coronary artery disease screening test improves outcome.^15,16 Some have questioned the ethics of this practice.⁸ The same problem applies to the routine evaluation of patients who have undergone myocardial revascularization. Although functional testing may identify patients who are at increased risk⁶ and may identify patients who have saphenous vein graft disease⁸, in the absence of any evidence of improved clinical outcome, it is hard to justify this practice. Does routine functional testing following CABG improve clinical outcome? Although the investigators of the ROSETTA-CABG Registry had too few patients and too little follow-up to provide us with definitive results, they are to be commended for even asking the question. We should only hope that leaders in the cardiovascular community will make attempts to rein in the practice of routine, functional testing after revascularization and instead stimulate interest in and raise resources so that the badly needed, randomized trials can be performed.

1. Eisenberg MJ, Wou K, Nguyen H, et al. Lack of benefit for routine functional testing early after coronary artery bypass graft surgery: Results from the ROSETTA-CABG Registry. J Invasive Cardiol 2006;18:147–152. 2. Yusuf S, Zucker D, Peduzzi P, et al. Effect of coronary artery bypass graft surgery on survival: overview of 10-year results from randomised trials by the Coronary Artery Bypass Graft Surgery Trialists Collaboration. Lancet 1994;344:563–570. 3. Rogers WJ, Coggin CJ, Gersh BJ, et al. Ten-year follow-up of quality of life in patients randomized to receive medical therapy or coronary artery bypass graft surgery. The Coronary Artery Surgery Study (CASS). Circulation 1990;82:1647–1658. 4. Eagle KA, Guyton RA, Davidoff R, et al. ACC/AHA Guidelines for coronary artery bypass graft surgery: A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee to Revise the 1991 Guidelines for Coronary Artery Bypass Graft Surgery). American College of Cardiology/American Heart Association. J Am Coll Cardiol 1999;34:1262–1347. 5. Puskas JD, Williams WH, Mahoney EM, et al. Off-pump vs conventional coronary artery bypass grafting: Early and 1-year graft patency, cost, and quality-of-life outcomes: A randomized trial. JAMA 2004;291:1841–1849. 6. Lauer MS, Lytle B, Pashkow F, et al. Prediction of death and myocardial infarction by screening with exercise-thallium testing after coronary-artery-bypass grafting. Lancet 1998;351:615–622. 7. Califf RM, Armstrong PW, Carver JR, et al. 27th Bethesda Conference: Matching the intensity of risk factor management with the hazard for coronary disease events. Task Force 5. Stratification of patients into high, medium and low risk subgroups for purposes of risk factor management. J Am Coll Cardiol 1996;27:1007–1019. 8. Lauer MS. Role of stress testing and cardiac imaging in patients who have undergone previous coronary revascularization. Cardiol Rev 2000;8:158–165. 9. Mozaffarian D. Electron-beam computed tomography for coronary calcium: A useful test to screen for coronary heart disease? JAMA 2005;294:2897–2901. 10. Patz EF Jr, Goodman PC, Bepler G. Screening for lung cancer. N Engl J Med 2000;343:1627–1633. 11. Elmore JG, Armstrong K, Lehman CD, Fletcher SW. Screening for breast cancer. JAMA 2005;293:1245–1256. 12. Ashton HA, Buxton MJ, Day NE, et al. The Multicentre Aneurysm Screening Study (MASS) into the effect of abdominal aortic aneurysm screening on mortality in men: A randomised controlled trial. Lancet 2002;360:1531–1539. 13. Fleming C, Whitlock EP, Beil TL, Lederle FA. Screening for abdominal aortic aneurysm: A best-evidence systematic review for the U.S. Preventive Services Task Force. Ann Intern Med 2005;142:203–211. 14. Screening for abdominal aortic aneurysm: Recommendation statement. Ann Intern Med 2005;142:198–202. 15. Lee TH, Brennan TA. Direct-to-consumer marketing of high-technology screening tests. N Engl J Med 2002;346:529-31. 16. Lauer M, Froelicher ES, Williams M, Kligfield P. Exercise testing in asymptomatic adults: A statement for professionals from the American Heart Association Council on Clinical Cardiology, Subcommittee on Exercise, Cardiac Rehabilitation, and Prevention. Circulation 2005;112:771–776. 17. Aktas MK, Ozduran V, Pothier CE, et al. Global risk scores and exercise testing for predicting all-cause mortality in a preventive medicine program. JAMA 2004;292:1462–1468.