SIGNIFICANCE OF ULTRAFAST COMPUTED-TOMOGR APHY IN THE ASSESSMENT OF CORONARY-BYPASS GRAFT PATENCY

Bypass graft patency with ultrafast computed tomography (= Electron Be am Tomography, EBT) was examined in 72 bypass grafts (47 saphenous vei ns, 25 internal mammary arteries) in 30 patients and compared with cor onary angiography. Angiography was performed a mean of 4.4 +/- 3.5 mon ths (range 1-13) from the EBT examination. Contrast material (120 ml) was continuously administered via a peripheral vein and 40 axial slice s (3 mm slice thickness, 110 ms scan time) without overlap sequences w ere obtained, ECG triggered with the single slice scanner mode. Imagin g of internal mammary artery grafts began at the thoracic inlet, for s aphenous vein grafts, at the undersurface of the aorta. Sixty of 63 an giographically patent bypass grafts were determined patent by EBT (sen sitivity 95%), 8 bypass grafts could not be detected by EBT, and 9 wer e angiographically occluded (specificity 89%). Twenty-four of 25 inter nal mammary artery grafts were patent at EBT and coronary angiography, one was occluded. In 27 of the 30 patients (90%), all of the angiogra phically patent grafts could be confirmed as open with EBT. Obstructio ns of 10 grafts could not be visualized with EBT. Graft insertion into native coronary vessels could be visualized in axial slices, although morphologic quantification of graft insertion stenosis (75-90%) in tw o cases was not possible. Three-dimensional reconstruction of the 40 a xial slices allowed graft anatomy to be delineated. Visualization of b ypass insertion into the native coronary vessel was less successful be cause of opacification of the left and right ventricle. Electron beam computed tomography is a minimally invasive procedure capable of evalu ating the patency of saphenous vein and internal mammary artery grafts . The morphologic quantification of graft obstruction and visualizatio n of the insertion of the bypasses into the native coronary vessels is less successful with present technology and imaging modalities.