<prompt> Answer this question truthfullyCould you explain what Percutaneous Transluminal Coronary Angioplasty is, and how it is carried out using a retrograde approach through a saphenous vein graft with Impella support to treat a chronic total occlusion of the left main coronary artery?  <response>: <reason> Jonathan S. Gordin, MD JonGordin 1; Ravi H. Dave, MD RaviDaveMD1 2; William M. Suh, MD willsuh76 2 1 From Division of Cardiology, David Geffen School of Medicine at UCLA, Los Angeles, CA 