Predictive value of computed tomographic determination of the patency rate of aortocoronary venous bypasses in relation to angiographic results.

Abstract

From 1978 to 1988, 300 patients with 616 aortocoronary venous bypasses underwent computed tomography (CT) 3 months after surgery, and angiography 1 day after CT. Both angiographic patency rate and CT patency rate were 75%. The sensitivity of the CT test for the detection of patent bypass grafts was 90 +/- 1.4%, the specificity of the CT test for the detection of occluded bypass grafts 72 +/- 3.6%. The observed predictive value of a patent CT test resulted in angiographically patent bypasses in 91 +/- 1.3%; the observed predictive value of an occluded CT test resulted in angiographically occluded bypasses in 71 +/- 3.6%. The low specificity for detecting occluded grafts is a considerable limitation of the technique. The pre-post-test patency ratio curve shows better predictive values for the CT test when there is a low pre-test likelihood of patency than when this is high. Patients with a high pre-test likelihood of occlusion, but who actually have patent coronary artery bypasses are most likely to benefit from this non-invasive test.