CABG graft occlusion due to competitive flow from native artery
Coronary CT requested for assessment of CABG grafts performed elsewhere.
ECG-gated coronary CT angiogram
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3D images show a left internal mammary artery (LIMA) graft to the LAD, with patent graft and accompanying surgical clips. There is also a trail of clips without an accompanying artery (arrows) from the aorta to the first obtuse marginal branch (OM1). Appearances are highly suggestive of aorto-coronary graft occlusion, which is confirmed on the axial images. Note that this occluded graft could be easily missed on source images, if the 3D images were not reviewed first. Also, the OM1 proximal and distal to the occluded graft is patent.
Coronary artery bypass grafts are much easier to identify first on 3D reconstructions, prior to analysis of source images. In particular, occluded grafts can be easily missed on source images. On 3D, a trail of surgical clips without an accompanying artery is a strong indicator of an occluded graft.
In this case, the cause of graft failure was due to competitive flow from a patent native vessel. When a graft is used to bypass a vessel with only mild stenosis, the need for bypass flow is low causing the graft to fail. This is especially seen in arterial grafts, which have muscular walls and autoregulate their lumen in response to flow.