Neoangiogenesis connecting a left internal mammary artery proximal stump to an ischemic area of the heart after bypass occlusion.

Internal mammary arteries (IMAs), via angiogenesis/arteriogenesis, have great potential for developing collaterals. This generally occurs when ischemia involves the inferior limbs or heart. Although this phenomenon may be spontaneous, it seems to be promoted by iatrogenic or voluntary occlusion of the IMAs. We present a patient who underwent triple coronary artery bypass grafting with two saphenous vein grafts and a free-graft left IMA and suffered an acute myocardial infarction 6 weeks after surgery. Emergency coronary angiography revealed occlusion of the grafts and an amazing branch arising from the proximal stump of the surgically-cut and clipped IMA, leading to the anterior wall of the heart, functionally creating an effective natural bypass, probably stimulated both by anterior wall ischemia and interrupted flow within the proximal left IMA.