Unlike an appendectomy, which cures appendicitis, bypass surgery doesn’t eliminate your risk for angina or heart attack. In fact, people who have had bypass surgery are at increased risk for serious heart problems compared with the rest of the population because they still have the underlying disease, atherosclerosis. This disease caused the initial coronary artery blockages and can cause later blockage, either in the patient’s original arteries or in the bypass grafts.

These new studies show that stress testing can help identify which patients are most prone to develop problems after bypass, just as stress tests are currently used to identify which people could benefit from bypass in the first place. Although national guidelines don’t recommend routine testing of people without angina after bypass, these two studies suggest that exercise testing can distinguish between high and low-risk patients based on the symptoms they get during exercise and the abnormalities in blood flow detected by the thallium scan.

This finding would be of only academic interest unless there were also something physicians could do to help the high-risk patients. Many cardiologists, including myself, believe that aggressive treatment may reduce the risk of heart attack or other serious heart trouble for patients at high risk after bypass. Such treatments include using beta-blockers, aspirin, and cholesterol-lowering statin drugs, as well as angioplasty and stents to clear blockages. In some patients, repeat surgery may even be warranted.

But when, if, and how often you should be tested after bypass surgery are still unclear. Some physicians recommend a stress test only if a patient develops new symptoms of angina or shortness of breath. However, I usually recommend some sort of early exercise evaluation (within one to two years after surgery), often in conjunction with a cardiac rehabilitation program, for patients whether they have angina or not.

This gives a baseline for future comparisons, and it can encourage the patient to adopt a healthy lifestyle. After that, I would suggest an exercise test for all patients every two to three years. For patients who can exercise normally or have only mild abnormalities on the test, I can offer reassurance that the prognosis is good. For patients whose test results signify trouble, more medication, angiography (a more detailed imaging technique) to identify early problems, or both may be the best way to avoid a heart attack.