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Figure 1 Selective coronary angiography of the left internal mammary artery (LIMA) and the left anterior descending coronary artery (LAD). (Upper panels) Competitive flow without graft restriction. (A) Injection in the LIMA. The empty arrow points to the joining tract, where flow entering from the LIMA is stopped by non-contrasted blood coming from the proximal LAD. (B) Injection in the left main shows anterograde filling of the LAD. (Lower panels) Competitive flow with graft restriction. (C) The dye selectively injected into the LIMA partially fills the graft, which is thin (arrows) and does not allow the contrast to reach the joining tract. (D) Contrast injection in the left main shows anterograde filling of the LAD, with 30% middle tract stenosis (empty arrow).