Utilization of shape memory in external vein-graft meshes allows extreme diameter constriction for suppressing intimal hyperplasia: a non-human primate study.
OBJECTIVE
Constrictive external Nitinol meshes have been shown to suppress neointimal tissue formation and preserve endothelial integrity in vein grafts. As this mitigating effect increased with the degree of constriction, we investigated whether extreme constriction was possible without leading to detrimental luminal encroachment.


METHODS
A senescent non-human primate model (Chacma baboons/bilateral femoral interposition grafts) mimicking the clinical size-mismatch between vein grafts and run-off arteries was used. Control grafts were either untreated (group 1) or spray-coated with fibrin glue (group 2). Nitinol meshes constricting the lumen by <or=80% (group 3) were compared with longitudinally pleated meshes of identical circumference that constricted the lumen by >90% (group 4). Anastomotic size mismatch at implantation was expressed as quotient of cross-sectional area of run-off artery to vein graft (Q(C)).


RESULTS
At 6 months, all vein grafts without mesh support showed thick eccentric layers of neointimal tissue (group 1: 348 +/- 130 microm [Q(C) median at implant 0.19]; group 2: 318 +/- 142 microm [Q(C) median at implant 0.17]). Fibrin glue-spraying had no effect. In contrast, neointimal tissue was absent in all mesh-supported grafts (P < .007 in all cases) both at 6 weeks/6 months (group 3: 7.5 +/- 8.8 mum and 2.5 +/- 4.4 microm [Q(C) median at implant 1.47]; group 4: 1.3 +/- 0.6 microm and 3.8 +/- 5.6 microm [Q(C) median at implant 3.09]). Except for mild tissue buckling (fold height <356 microm) in one group 3 graft, none of the mesh-constricted grafts showed wall folds. Endothelial coverage was only complete in the mesh-supported groups (100% in group 3 and 4 vs 85 +/- 14%; P < .023 in group 1). Fibrin glue alone (52 +/- 48%) did not preserve endothelialization of control grafts (P < .38).


CONCLUSIONS
Extreme vein graft constriction using external Nitinol meshes is possible without detrimental tissue buckling. Although moderate constriction was found to be sufficient for mitigating diffuse intimal hyperplasia and endothelial detachment, extreme constriction may occasionally be required to eliminate luminal irregularities.
Zilla
Peter
P
Christiaan Barnard Division of Cardiothoracic Surgery, University of Cape Town, Cape Town, South Africa. peter.zilla@uct.ac.za
Wolf
Michael
M
Rafiee
Nasser
N
Moodley
Loven
L
Bezuidenhout
Deon
D
Black
Melanie
M
Human
Paul
P
Franz
Thomas
T
D000497:Alloys; D000714:Anastomosis, Surgical; D000818:Animals; D003250:Constriction; D042783:Endothelial Cells / Q000473:pathology; D004867:Equipment Design; D005263:Femoral Artery / Q000473:pathology / Q000503:physiopathology / Q000601:surgery*; D005268:Femoral Vein / Q000473:pathology / Q000503:physiopathology / Q000637:transplantation*; D015718:Fibrin Tissue Adhesive; D006965:Hyperplasia; D023421:Models, Animal; D048549:Papio ursinus; D012039:Regional Blood Flow; D013526:Surgical Mesh; D013997:Time Factors; D014014:Tissue Adhesives; D017539:Tunica Intima / Q000473:pathology; D017540:Tunica Media / Q000473:pathology; D014654:Vascular Patency; D014656:Vascular Surgical Procedures / Q000009:adverse effects / Q000295:instrumentation / Q000379:methods
D000497:Alloys; D015718:Fibrin Tissue Adhesive; D014014:Tissue Adhesives; C013616:nitinol