Role of electron beam tomography in evaluation of coronary artery bypass graft patency

Purpose: Electron beam tomography (EBT) permits acquisition of images with high spatial and temporal resolution. The value of EBT and other imaging mo dalities for the depiction of patent coronary artery bypass grafts (ACVB, I MA) are compared to coronary angiography and an overview of current results is given. Material and methods: Graft patency can be evaluated with indirect methods stress,such as echocardiography, radionuclide ventriculography, myocardial scintigraphy, positron-emission tomography (PET) and direct imaging modalit ies,such as Doppler/2D echocardiography,EBT,spiral computed tomography (SCT ) and magnetic resonance angiography (MRA). Results: With indirect methods graft patency can be evaluated with sensitiv ity of 64-100% and specificity of 73-100%. EBT and SCT are equivalent in se nsitivity (=94%) in the assessment of open Venous grafts and specificity is up to 100%, but EBT is superior in the diagnosis of patent IMA grafts (sen sitivity 100% vs 89%). Visualization of high-grade Venous bypass stenosis s eems possible with EBT. MRA with gradient echo technique is highly accurate in the assessment of patent venous grafts (sensitivity 77-93%) but has lim ited value in the evaluation of IMAs (sensitivity=53%). Promising are ultra fast 3D-MRA methods which permit high accuracy (sensitivity=94-96%) in asse ssing venous and arterial grafts. Discussion: Indirect imaging methods cannot differentiate between an occlud ed bypass, progression of coronary artery disease and myocardial infarction . EBT and SCT are equivalent in the diagnosis of open and occluded venous g rafts, but EBT is superior in the assessment of patent IMA grafts. Visualiz ation of high-grade venous bypass stenosis seems possible with EBT. MRA tec hniques, especially ultrafast 3D-MR methods,are highyly accurate in the ass essment of patent venous and arterial grafts but are still limited to scien tific research.