The development of polymeric cardiovascular collagen prostheses.

Abstract

ABSTRACTIn an attempt to develop a long‐lasting, non‐thrombogenic, collagen cardiovascular prosthesis this laboratory has sequentially evaluated a series of modified collagen structures treated as polymers. Bovine arteries and human umbilical cords have been subjected to various chemical modifications and grouped as follows: 1.) fresh, untreated vessels, 2.) commercially available dialdehyde starch tanned grafts, 3.) ficin digested (muscle and elastin removed) vessels, 4.) ficin digested negatively charged, untanned grafts, 5.) ficin digested, negatively charged, dialdehyde starch tanned grafts, 6.) ficin digested, oxidized carboxymethylcellulose tanned grafts, 7.) ficin digested, glutaraldehyde tanned, protein cross‐linked, negatively charged grafts. The aim in each case was to create a specific recurrent stereo specific electrochemical charge at the blood‐tissue interface. These tubular grafts were then evaluated in several positions following canine implantation. The results confirmed that the single most important factor in assuring long‐term patency and function was provision of a uniform, highly covalently bonded, glutaraldehyde tanned, negative surface charge. Unmodified grafts thrombosed and then became calcified or dissolved within a short period of time.Techniques for evaluation included resistance to thrombosis and observed characteristics of the grafts at periodic intervals of 1 second, 2 hours, 2 weeks, 1 month, 3 months, 6 months, 9 months, 12 months and longer. Upon removal, each of these grafts was inspected, photographed, tested for tensile strength, and observed by light and scanning electron microscopy. In summary, the most satisfactory graft was the ficin digested, glutaraldehyde tanned, negatively charged prosthesis.Subsequently, these grafts were prepared for implantation in humans. At this time approximately 69 segments have been implanted in 35 patients. The majority (36) have been implanted in the femoral‐popliteal position. Axillofemoral, femorofemoral, aortorenal, peripheral arteriovenous, coronary, iliopopliteal and femoroperoneal bypasses were also performed. These results have been compared with gas endarterectomy, saphenous vein bypass (conventional), and bovine heterograft prostheses in similar implantation sites. Follow‐up of this group to two years reveals patency approaching that of autogenous saphenous vein grafts and surpassing that of conventional bovine heterografts. These data suggest that collagen with chemical and surface charge modification may lead to a new generation of biological cardiovascular prostheses exhibiting improved performance characteristics and freedom from thrombosis.