Novel synthetic selectively degradable vascular prostheses: a preliminary implantation study.
BACKGROUND
Vascular grafts perform less well than autologous arterial or vein grafts. The purpose of this study was to evaluate the short-term performance of selectively biodegradable filament-wound vascular prostheses, comprising elastomeric poly(ether urethane) (Lycra) scaffolds and flexible, hydrophilic biodegradable coatings.


METHODS
Two types of selectively biodegradable vascular grafts were manufactured, comprising a filament-wound Lycra scaffold, subsequently coated with a biodegradable poly(ethylene glycol)/poly(lactic acid) (PELA) block copolymer. The two types of grafts differed in both the overall porosity of the scaffold and the hydrophilicity of the biodegradable constituent. A 60-mm-long and 6-mm-diameter filament-wound and polytetrafluoroethylene (ePTFE) grafts were implanted as interposition prostheses, randomly, at the right- and left-side carotid arteries.


RESULTS
Implantation studies proved the grafts to be patent and pulsatile for periods of up to 3 months. Increasing the scaffold porosity and enhancing the hydrophilicity of the biodegradable component improved both the transmural tissue ingrowth process and the vascularization of the prosthesis wall. Also, a well-adhered peripheral tissue and a thin, uniform intima and endothelial lining were obtained. All ePTFE graft controls, although patent, were rather stiff and nonpulsatile. A thick pseudointima, poorly attached to the prosthesis inner surface, was observed. The compliance of the wet grafts was significantly higher than in the dry state, stemming mainly from the water-plasticizing effect on the biodegradable component. The grafts explanted after a period of 6 weeks exhibited compliance only slightly lower than that of the wet grafts. After 12 weeks, however, the hoop compliance was 20% lower than that prior to implantation. At 100 mm Hg, for example, the original compliance of the wet graft was 2.5%/100 mm Hg decreasing to 2.0%/100 mm Hg after a 3-month implantation. The compliance reduction with implantation is attributed to the ingrowth of the perigraft tissue as revealed by the histological study. A compliance of 2.0%/100 mm Hg is slightly better than that of a standard PTFE graft with an original compliance of 1.6%/100 mm Hg. Yet it is still an order of magnitude smaller than that of a canine carotid artery.


CONCLUSIONS
The improved mechanical properties and enhanced healing of the highly porous filament-wound Lycra scaffold graft coated with hydrophilic biodegradable PELA has the potential of being a highly effective small caliber prosthetic graft.
Izhar
U
U
Joseph Lunenfeld Cardiac Surgery Research Center, Hadassah University Hospital, Jerusalem, Israel.
Schwalb
H
H
Borman
J B
JB
Hellener
G R
GR
Hotoveli-Salomon
A
A
Marom
G
G
Stern
T
T
Cohn
D
D
D020341:Absorbable Implants; D000818:Animals; D001807:Blood Vessel Prosthesis; D019917:Blood Vessel Prosthesis Implantation; D017536:Carotid Artery, Common; D002448:Cell Adhesion; D004285:Dogs; D004730:Endothelium, Vascular / Q000166:cytology / Q000502:physiology; D007773:Lactates / Q000493:pharmacokinetics; D023421:Models, Animal; D011092:Polyethylene Glycols / Q000493:pharmacokinetics; D011108:Polymers / Q000493:pharmacokinetics; D011138:Polytetrafluoroethylene / Q000493:pharmacokinetics; D011140:Polyurethanes; D013997:Time Factors; D017539:Tunica Intima / Q000166:cytology / Q000502:physiology
D007773:Lactates; D011108:Polymers; D011140:Polyurethanes; C058523:polyethylene oxide-polylactic acid block copolymer; D011092:Polyethylene Glycols; D011138:Polytetrafluoroethylene