IDENTIFICATION OF RECURRENT ISCHEMIA AFTER CORONARY-ARTERY BYPASS-SURGERY - A COMPARISON OF POSITRON EMISSION TOMOGRAPHY AND SINGLE PHOTON-EMISSION COMPUTED-TOMOGRAPHY

Current techniques for the detection of recurrent coronary stenoses fo llowing bypass grafting have shown disappointing diagnostic accuracy. This study used the same dipyridamole-handgrip stress to compare the a ccuracy of rubidium-82 positron emission tomography and thallium-201 s ingle photon emission computed tomography, in 50 consecutive post-bypa ss patients undergoing coronary arteriography at a mean interval of 6. 5 years after surgery. Significant stenoses in native coronary vessels (> 50% diameter) or grafts (> 70% diameter) were defined by quantitat ive angiography. Forty-six patients had recurrent or residual stenoses , 43 (93%) had a perfusion defect identified by positron emission tomo graphy, and 35 (76%) were identified by single photon emission compute d tomography (P = 0.04). Fourteen of the 17 patients (82%) without pre vious Q-wave myocardial infarction were identified by positron emissio n tomography; 10 of the 17 (59%) were detected by single photon emissi on computed tomography (P = NS). Stress-induced perfusion defects were demonstrated by positron emission tomography in 19 patients; of this group, thallium imaging identified reversible defects in 11, showed no perfusion defect in 1, and portrayed a persistent defect in 7 patient s. Significant graft disease was present in 33 patients; perfusion def ects were identified by positron emission tomography in 30 (91%), and by single photon emission computed tomography in 24 (73%, P = NS). Fou r patients were fully revascularized, without significant recurrent co ronary disease; normal perfusion was present in 3 (75%) by positron em ission tomography, and 4 (100%) by single photon emission computed tom ography. Myocardial perfusion imaging using positron emission tomograp hy has a high accuracy for the detection of both graft and native vess el disease, and may be useful in the non-invasive follow-up of patient s following coronary artery bypass grafting.