Definition: Given an abstract, generate a keyword (a noun phrase) that best describes the focus or contribution of the paper. Such keywords can be directly from the given abstract or outside it.
Input: Abstract: Four patients with recurrent severe angina and evidence of myocardial ischemia two to six months after surgical coronary revascularization have been submitted to percutaneous transluminal angioplasty of the distal insertion of internal mammary artery grafts or of the recipient vessel distal to it. These cases illustrate the feasibility and safety of transluminal angioplasty of right and left internal mammary artery grafts, using the mammary artery as a way of access.
Output:
Adult