title: Protective constriction of coronary vein grafts with knitted nitinol.
abstract: OBJECTIVE
  Different flow patterns and shear forces were shown to cause significantly more luminal narrowing and neointimal tissue proliferation in coronary than in infrainguinal vein grafts. As constrictive external mesh support of vein grafts led to the complete suppression of intimal hyperplasia (IH) in infrainguinal grafts, we investigated whether mesh constriction is equally effective in the coronary position.
  
  
  METHODS
  Eighteen senescent Chacma baboons (28.8 ± 3.6 kg) received aorto-coronary bypass grafts to the left anterior descending artery (LAD). Three groups of saphenous vein grafts were compared: untreated controls (CO); fibrin sealant-sprayed controls (CO + FS) and nitinol mesh-constricted grafts (ME + FS). Meshes consisted of pulse-compliant, knitted nitinol (eight needles; 50 μm wire thickness; 3.4 mm resting inner diameter, ID) spray attached to the vein grafts with FS. After 180 days of implantation, luminal dimensions and IH were analysed using post-explant angiography and macroscopic and histological image analysis.
  
  
  RESULTS
  At implantation, the calibre mismatch between control grafts and the LAD expressed as cross-sectional quotient (Qc) was pronounced [Qc = 0.21 ± 0.07 (CO) and 0.18 ± 0.05 (CO + FS)]. Mesh constriction resulted in a 29 ± 7% reduction of the outer diameter of the vein grafts from 5.23 ± 0.51 to 3.68 ± 0 mm, significantly reducing the calibre discrepancy to a Qc of 0.41 ± 0.17 (P < 0.02). After 6 months of implantation, explant angiography showed distinct luminal irregularities in control grafts (ID difference between widest and narrowest segment 74 ± 45%), while diameter variations were mild in mesh-constricted grafts. In all control grafts, thick neointimal tissue was present [600 ± 63 μm (CO); 627 ± 204 μm (CO + FS)] as opposed to thin, eccentric layers of 249 ± 83 μm in mesh-constricted grafts (ME + FS; P < 0.002). The total wall thickness had increased by 363 ± 39% (P < 0.00001) in CO and 312 ± 61% (P < 0.00001) in CO + FS vs 82 ± 61% in ME + FS (P < 0.007).
  
  
  CONCLUSIONS
  In a senescent non-human primate model for coronary artery bypass grafts, constrictive, external mesh support of saphenous veins with knitted nitinol prevented focal, irregular graft narrowing and suppressed neointimal tissue proliferation by a factor of 2.5. The lower degree of suppression of IH compared with previous infrainguinal grafts coincided with a lesser reduction of calibre mismatch in the coronary grafts.
authors.affiliation: Chris Barnard Department of Cardiothoracic Surgery, University of Cape Town, Cape Town, South Africa.
authors.forename: Loven
authors.initials: L
authors.lastname: Moodley
authors.forename: Thomas
authors.initials: T
authors.lastname: Franz
authors.forename: Paul
authors.initials: P
authors.lastname: Human
authors.forename: Michael F
authors.initials: MF
authors.lastname: Wolf
authors.forename: Deon
authors.initials: D
authors.lastname: Bezuidenhout
authors.forename: Jacques
authors.initials: J
authors.lastname: Scherman
authors.forename: Peter
authors.initials: P
authors.lastname: Zilla
mesh_terms: D000497:Alloys / Q000627:therapeutic use*; D000818:Animals; D001807:Blood Vessel Prosthesis; D017023:Coronary Angiography; D001026:Coronary Artery Bypass / Q000009:adverse effects / Q000295:instrumentation / Q000379:methods; D003331:Coronary Vessels / Q000473:pathology / Q000601:surgery; D006653:Histology; D058426:Neointima / Q000453:epidemiology / Q000473:pathology; D010215:Papio; D018709:Statistics, Nonparametric
chemical_list: D000497:Alloys; C013616:nitinol
keywords: Coronary bypass; Intimal suppressive; Knitted nitinol mesh; Vein grafts