title: Flow dynamics and wall shear stress in the left internal thoracic artery: composite arterial graft versus single graft.
abstract: OBJECTIVE
  Phasic blood flow dynamics and wall shear stress (WSS) have the potential to directly modulate endothelial responses, playing an important role in the development of bypass graft occlusion. This study compares phasic blood flow velocity patterns and WSS of the left internal thoracic artery (LITA) used as a composite Y-graft (27 patients, Y-group) and as a single graft (24 patients, S-group) on the left anterior descending (LAD) coronary artery.
  
  
  METHODS
  An intravascular Doppler-tipped guide wire was used for postoperative analysis of phasic blood flow velocity. Flow velocities were recorded proximally and distally into the LITA in both groups. Digitalized spectral velocities were acquired to compute systolic peak velocity, diastolic peak velocity, and average peak velocity. The ratio of diastolic to systolic peak velocity was computed (DSVR). WSS was calculated from graft flow velocity and vessel diameter.
  
  
  RESULTS
  Proximal LITA in Y-group had greater average peak velocity (APV) (p=0.000), DSVR (p=0.026), flow volume (p=0.000), WSS (p=0.02), and diameter (0.019) than S-group. There were not significant differences for the distal LITA between the two groups.
  
  
  CONCLUSIONS
  The LITA shows a marked adaptability to flow dynamics. The proximal tract of the LITA in Y-group is able to match increased flow requirements, probably through the release of endothelial vasoactive mediators. Flow velocity spectra acquired in the proximal LITA in Y-group resemble the biphasic coronary artery pattern with a clear diastolic predominance. This pattern is probably consequence of the increase of blood flow due to the lower vascular resistance of the Y-graft system and to the active dilatation of the LITA.
authors.affiliation: Division of Cardiovascular Surgery, Luigi Sacco Hospital, Via Grassi 74, Milan 20157, Italy. m.lemma@hsacco.it
authors.forename: Massimo
authors.initials: M
authors.lastname: Lemma
authors.forename: Andrea
authors.initials: A
authors.lastname: Innorta
authors.forename: Matteo
authors.initials: M
authors.lastname: Pettinari
authors.forename: Andrea
authors.initials: A
authors.lastname: Mangini
authors.forename: Guido
authors.initials: G
authors.lastname: Gelpi
authors.forename: Manuela
authors.initials: M
authors.lastname: Piccaluga
authors.forename: Paolo
authors.initials: P
authors.lastname: Danna
authors.forename: Carlo
authors.initials: C
authors.lastname: Antona
mesh_terms: D000368:Aged; D001783:Blood Flow Velocity; D006328:Cardiac Catheterization; D017023:Coronary Angiography; D004730:Endothelium, Vascular / Q000503:physiopathology; D005260:Female; D018056:Hemorheology; D006801:Humans; D007387:Internal Mammary-Coronary Artery Anastomosis / Q000379:methods*; D008297:Male; D008323:Mammary Arteries / Q000503:physiopathology*; D008875:Middle Aged; D013314:Stress, Mechanical; D014654:Vascular Patency