title: Arterial conduit shear stress following bypass grafting for intermediate coronary artery stenosis: a comparative study with saphenous vein grafts.
abstract: OBJECTIVE
  Graft failure has been reported when the arterial conduit, such as the internal thoracic artery (ITA) or the right gastroepiploic artery (GEA), is grafted to a lower grade coronary artery stenosis. The shear stress as a significant factor affecting graft patency was compared between the arterial conduit and the saphenous vein graft (SVG) after surgery.
  
  
  METHODS
  In 101 patients, 40 ITAs, 27 GEAs and 34 SVGs were examined using a Doppler-tipped guide wire during postoperative angiography. The graft flow volume and shear stress were calculated from velocity and diameter data. The study grafts were classified according to the grade of native coronary artery stenosis: group L had more than 50 up to 75% stenosis, and group H had more than 75% stenosis. Group H consisted of 25 ITAs, 17 GEAs and 21 SVGs, while group L consisted of 15 ITAs, 10 GEAs and 13 SVGs.
  
  
  RESULTS
  In group H, graft flow volume did not significantly differ among the ITA (34+/-11 ml/min), GEA (36+/-16 ml/min) and SVG (41+/-15 ml/min), and graft shear stress significantly (ITA vs. GEA P<0.0001; GEA vs. SVG P<0.01) differed among the ITA (16.0+/-4.8dyn/cm(2)), GEA (9.1+/-3.2dyn/cm(2)) and SVG (4.8+/-1.6dyn/cm(2)). In group L, flow volume was lower (P<0.001) in the ITA (18+/-6 ml/min) and GEA (13+/-8 ml/min) than in the SVG (35+/-16 ml/min), and shear stress was significantly (P<0.001) greater in the ITA (13.7+/-4.9dyn/cm(2)) than the GEA (5.6+/-2.0dyn/cm(2)) or SVG (4.6+/-2.0dyn/cm(2)).
  
  
  CONCLUSIONS
  These data suggest that shear stress of the ITA is superior and maintained despite the flow volume being reduced by flow competition. Lower shear stress of the GEA for intermediate stenosis may be associated with the development of conduit failure.
authors.affiliation: Department of Surgery II, Tokyo Medical University, 6-7-1 Nishishinjuku, Shinjuku-ku, Tokyo 160-0023, Japan. tshimizu-cvs@umin.ac.jp
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Shimizu
authors.forename: Shigeki
authors.initials: S
authors.lastname: Ito
authors.forename: Yujiro
authors.initials: Y
authors.lastname: Kikuchi
authors.forename: Masaharu
authors.initials: M
authors.lastname: Misaka
authors.forename: Tetsuzo
authors.initials: T
authors.lastname: Hirayama
authors.forename: Shin
authors.initials: S
authors.lastname: Ishimaru
authors.forename: Akira
authors.initials: A
authors.lastname: Yamashina
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001783:Blood Flow Velocity; D006328:Cardiac Catheterization; D017023:Coronary Angiography; D001026:Coronary Artery Bypass / Q000379:methods*; D023921:Coronary Stenosis / Q000601:surgery*; D005260:Female; D005500:Follow-Up Studies; D024405:Gastroepiploic Artery / Q000503:physiopathology / Q000637:transplantation*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011184:Postoperative Period; D012501:Saphenous Vein / Q000503:physiopathology / Q000637:transplantation; D013314:Stress, Mechanical; D013895:Thoracic Arteries / Q000503:physiopathology / Q000637:transplantation*; D014654:Vascular Patency