INHIBITION OF INTIMAL HYPERPLASIA AND OCCLUSION IN DACRON GRAFT WITH HEPARIN AND LOW-MOLECULAR-WEIGHT HEPARIN

Objective. Intimal hyperplasia (IH) is a significant cause of late pro sthetic graft occlusion. The influence of heparin and low molecular we ight heparin (LMWH) on IH was studied in a sheep model. Experimental d esign. A gelatin sealed Dacron (Gelsoft) interposition Vascular graft was placed end to end in sheep carotid artery. Standard heparin (SH) w as administered in a dose of 7,500 units twice daily subcutaneously (n =6). LMWH (enoxaparin) was administered in two dosages, a ''low dose'' of 2 mg/kg (n=6) and a ''high dose'' of 5 mg/kg (n=6) subcutaneously daily. A control group received a graft but no heparin (n=6). At one m onth the animals were sacrificed and the grafts sectioned. An intimal measurement was obtained under light microscopy using an eyepiece grat icule from a longitudinally sectioned graft. Results. Controls occlude d five grafts of six and recorded a mean intimal thickness of 2,510 mi crometres, SH sheep occluded two with a mean thickness of 83 (p<0.05), low dose enoxaparin sheep had no occlusions with a mean thickness of 73 (p<0.001) and high dose enoxaparin sheep occluded one with a mean t hickness of 225 (p<0.01). The reduced occlusion rates were significant for the LMWH groups (p=0.007 for low dose, p=0.04 for high dose) but not for SH. There were no significant differences between treatment gr oups with respect to IH. Conclusions. In this sheep animal study, each of SH and two LMWH dose regimens resulted in a reduction in Dacron va scular graft occlusion rate and the development of IH, with the greate st effect seen in the low dose LMWH group.