Evaluation of the patient with stable angina following coronary artery bypass surgery

Abstract

Bypass graft stenosis and occlusion are relatively common events, occurring eventually in the majority of patients who survive beyond 5 years after coronary artery bypass graft surgery. These processes, in combination with progressive native coronary artery disease, lead to recurrent angina and an increased need for medication in most patients late after surgery. Patients with unstable ischemic symptoms generally should proceed directly to coronary arteriography, whereas patients with stable angina may be candidates for noninvasive testing to evaluate their risk and the extent of myocardial jeopardy. If the initial revascularization procedure is successful, preoperative thallium 201 imaging abnormalities should be reversed. Persistent abnormalities beyond 6 months after revascularization indicate incomplete revascularization or perioperative infarction. Defects noted in the immediate postoperative period may be areas of myocardial stunning or hibernation, which can require up to 6 months to reverse. If chest pain recurs after revascularization, a normal thallium 201 perfusion pattern indicates that the symptom is probably not ischemic in nature. Thallium 201 perfusion abnormalities may precede symptoms by several months and may be the only indication of significant myocardial ischemia in patients with silent ischemia. Advanced tomographic imaging techniques, such as single photon emission computed tomography (SPECT), should theoretically improve disease detection and localization following revascularization. Practically speaking, only the left anterior descending coronary bed is well evaluated by these tomographic imaging techniques. The sensitivity and specificity of SPECT imaging for evaluation of posterior circulation abnormalities remains unacceptably low. Complexities of competitive flow and collateralization that may exist in the postoperative period make it difficult to relate perfusion abnormalities to a specific graft stenosis. However, tomographic perfusion imaging may provide useful correlative information on the functional impact of bypass graft stenoses in patients with recurrent angina who have undergone coronary angiography and in whom the angiographic indications for repeat surgery or angioplasty are not compelling. Newer tomographic and metabolic imaging techniques such as CT, NMRI, and PET remain unproven as diagnostic tests for the evaluation of unselected patient populations presenting with recurrent angina following revascularization surgery.