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(a-d) Intraoperative photographs and graphic illustration of the left 2nd intercostal space demonstrating the "venous ring" of the internal mammary vein, medial to the artery.
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The vein, exposed between the second and third costal cartilages, exhibited unusual anatomy in the form of the single vein forming a 'bifurcation', quickly followed cranially by the two vessels converging back into a single vessel, thus creating a venous 'ring' (Figure 1(a-c)).