Effect of healing on compliance of porous Dacron grafts.

The effects of tissue ingrowth on the compliance of porous Dacron grafts were studied in 8 mm external-velour warp-knit Dacron grafts implanted in the canine descending thoracic aorta. The compliance of these grafts was measured before implantation and after implant periods of two weeks and one, two, four, and six months. Compliance, which initially was 0.043 +/- 0.008% mm Hg, decreased less than 10% after implantation (no statistical difference at p less than 0.05). No anastomotic neointimal hyperplasia was observed. Although the total thickness of the graft wall increased two- to three-fold after implantation, the benign healing process observed in this study had very little influence on graft compliance followed to six months.

The influence of denier and porosity on performance of a warp-knit Dacron arterial prosthesis.

The study objective was to determine the optimal water porosity for a warp-knit, externally veloured Dacron arterial prosthesis. Preclotting efficiency, surgical handling characteristics, thrombogenicity, and 56-day healing in the descending thoracic aorta of mongrel dogs were measured for seven different arterial prostheses of the same basic design constructed to test the influence of decreased porosity produced by increased yarn denier at a constant needle density. The six prototypes tested were 160, 180, 200, 220, 240, and 280 denier. The 140 denier prosthesis (Bionit, C. R. Bard, Inc., Billerica, MA) served as the control. The water porosity of these prostheses varied from 2036 ml/cm2/min at 120 mmHg for the control to 286 for the 280 prototype. The preclotting efficiency increased with decreased water porosity and with increased outer-wall filamentousness. Desirability of surgical handling characteristics decreased with lowered water porosity, while the degree of outer-wall filamentousness had little influence. All the prostheses showed excellent through-wall healing at 56 days, including endothelialization. The 160 prototype represented an optimal blend of high preclotting efficiency, desirable surgical handling characteristics, and excellent 56-day healing. These studies are pertinent to the future development of porous, warp-knit Dacron arterial prostheses.

Effects of compliance alteration on healing of a porous dacron prosthesis in the thoracic aorta of the dog.

In our study, the results reveal that a marked reduction in the compliance of an external-velour, weft-knit Dacron prosthesis did not impair healing of either the graft wall or of the anastomoses when these grafts were implanted in the upper part of the descending thoracic aorta of the dog for 56 days. These observations are clinically relevant, since they are important to the design of noncrimped fabric prostheses which are resistant to kink and compression when used for axillofemoral, femoropopliteal and femorotibial bypass. However, experimental studies of the influence of compliance disparity should be extended to such grafts implanted for several years.

Experimental comparison of the thrombogenicity of fibrin and PTFE flow surfaces.

Two types of 4 mm ID prostheses were studied in the carotid arteries of the dog. These were noncrimped polypropylene-supported filamentous velour knitted Dacron (PPSFV) and expanded polytetrafluoroethylene (e-PTFE, Gore-Tex). Thrombus-"Free" Surface TFS) areas and patency rates were determined at the end of the implant periods. One series of implants was subjected to controlled low flow rates for six hours; another was exposed to physiologic flow rates and observed at seven days, 14 days, and 12 weeks. At six hours the filamentous Dacron, preclotted according to a specific regimen utilizating heparin, performed as well as, and possibly better than, e-PTFE. The Gore-Tex developed surface coagulum in an irregular fashion which was related to graft wetting and blood soakage. Seven-day TFS scores and patency rates of the two graft types were comparable at physiologic flow rates. At two weeks, TFS scores and patency rates of the two graft types were comparable at physiologic flow rates. At two weeks, TFS scores and patency rates dropped. This was sufficiently marked in the case of e-PTFE that longer-term implants were not done. However, PPSFV grafts were implanted for 12 weeks, and all grafts examined at that time had closed. It appears that patency of 4 mm ID grafts of this construction will not be reliably attained in the dog carotid artery without the use of platelet-inhibitory drugs until complete healing has occurred.

Current arterial prostheses. Experimental evaluation by implantation in the carotid and circumflex coronary arteries of the dog.

Five types of 4-mm diameter arterial prostheses (three Dacron, one expanded Teflon, one preserved umbilical vein) were studied in the dog to assess graft thrombogenicity. Separate experiments involving six hours of controlled blood flow, one-week carotid implantation, and aortocoronary implantation were performed. In general, graft thrombogenicity derived from controlled flow study was more predictive of a graft's long-term implantation success than were one-week implantation results. In order of increasing thrombogenicity, we ranked grafts studied as follows: noncrimped Dacron, expanded Teflon, crimped Dacron, umbilical vein. Results of 19 experimental left coronary artery implantations using Dacron or Teflon prostheses are reported that indicate grafts with low measured thrombogenicity are most likely to succeed in this site. Data presented in this report suggest there is reason to evaluate noncrimped, kink-resistant, porous Dacron grafts for use both in the left coronary artery and below the knee when there is compelling clinical indication and no autogenous vessels are available.

Geometric comparison of aortic bifurcation prostheses to the normal and atherosclerotic human aorta, and clinical trial of a vertical seamed bifurcation prosthesis.

The 12 bifurcation prostheses generally available in the United States were compared. One was woven Teflon, two woven Dacron, and nine knitted Dacron. Ten were "seamless" in construction, and two were "seamed," but close examination revealed that all prostheses actually were seamed at the bifurication point. The grafts varied considerably in construction, porosity, and geometry. To compare the geometries, each prosthesis was preclotted in plasma, inflated to 120 mm. Hg, and quick frozen in alcohol and dry ice. Transverse and frontal bisections of the frozen specimens were photographed with a millimeter scale for sizing. For comparison, eight human aortofemoral bifurcations were distended and frozen similarly. The prostheses had far wider bifurcation shelves than did the normal aortas. The five normal human aortofemoral bifurcations had an average ratio of limb: body diameter of 0.61; the three atherosclerotic specimens averaged 0.49. The prostheses had an average limb:body diameter ratio of 0.48. or the "seamless" grafts, 0.48 for the circular transverse limb-seamed grafts, and 0.58 for the vertical-seamed grafts. Vertical-seamed aortic bifurcation grafts implanted in 102 patients between 1970 and 1976 (average follow-up, 29.5 months) have developed only a single limb closure, at 53 months.