Modified polytetrafluoroethylene: Indium l 1 l-labeled platelet deposition on carbon-lined and high-porosity polytetrafluoroethylene grafts Hiromitsu Tsuchida, MD, PhD, Brian L. Cameron, MD, Carol S. Marcus, MD, PhD, and Samuel E. W'dson, MD, Orange, Calif., and Tokyo,Japan Platelet accumulation on carbon-lined (CL) and high-porosity (Ill') polytetrafluoroethylene (PTFE) grafts was investigated in vivo. In experiment l, 20 CL grafts and 20 control PTFE grafts, each 5 cm in length and 4 mm in diameter, were interposed into both carotid and femoral arteries of 10 dogs. In experiment 2, 12 l i p grafts (90 Itm mean internodal distance) and 12 control PTFE grafts were implanted in six dogs. Indium Ill-labeled platelets were injected intravenously and the grafts were retrieved 48 hours later. Radioactivity of the grafts and a control segment of the carotid artery was counted. A graft platelet accumulation index (GPAI) was calculated as the ratio of emission from the graft compared to that from the control segment. The GPAI of the CL graft was significantly less than the GPAI of the control graft in both the carotid (control 29.7 ± 5.46, CL 22.3 ± 6.55; n = 9 [p < 0.05]) and the femoral arteries (control 30.7 ± 9.65, CL 22.0 ± 6.59; n = 9 [p < 0.05]). There was no significant difference in GPAI between the control and HP grafts in the carotid arteries (control 30.6 ± 11.8, HP 31.5 ± 9.71; n = 6) and in the femoral arteries (control 31.5 ± 7.88, HP 34.0 ± 4.97; n = 6). Carbon linin~ decreases platelet accumulation on PTFE grafts in the early postoperative period, and HP grafts do not exhibit increased platelet uptake. (J V/ksc SURG 1992;16:643-50.)

Expanded polytettafluoroethylene (PTFE) vascular prostheses are commonly used for smaU-diameter vascular reconstruction; however, the incidence of graft occlusion is higher with IrFFE than with autogenous vein. Modifications of PTFE that would decrease one index of thrombogenicity, platelet accumulation, promise a more applicable prosthetic graft. The biocompatible characteristics of carbon allow successful incorporation in prosthetic materials. 1 Carbon coating has been shown to decrease the thrombogenicity of Dacron grafts in vivo and in vitro. 2 Scott et al., 3 for example, found the surface clotting time of carbon-coated Dacron grafts to be more than that of untreated Dacron grafts. Previous attempts to coat PTFE grafts with carbon resulted in From the Departmentsof Surgery (Drs. Cameronand Wilson) and Nuclear Medicine (Dr. Marcus), Harbor-UCLAMedical Center,and the Departmentof Surgery,TokyoMedicalCollege (Dr. Tsuchida). Presentedat the SeventhAnnualMeetingof the WesternVascular Society,Maui, Hawaii, Jan. 11-15, 1992. Reprintrequests:SamuelE. Wilson,MD, Departmentof Surgery, Universityof Califomia-IrvineMedical Center, 101 The City Dr. S., Orange, CA 92668. 24/6/409a4

improved patency rates, but the complex vacuum vapor-deposit method has not proved practical for clinical use. 4 We report the results of platelet deposition on a different carbon modification of the PTFE graft, in which a carbon lining is made by combining carbon powder with PTFE. The increased late patency of high-porosity (HP) PTFE grafts is attributed to rapid endothelialization due to transmural tissue incorporation, s'6 Although data on early thrombogenicity of HP-PTFE grafts are scant, Campbell et al.7 were concerned that higherporosity grafts developed early thrombosis. This study investigated the early accumulation of platelets on both carbon-lined (CL) PTFE grafts and HPPTFE grafts with use of indium 111 oxine-labeled platelets as a direct parameter of platelet deposition and with scanning electron microscopy (SEM) for direct observation of the graft surface. MATERIAL A N D M E T H O D S Highly pure carbon powder was mixed with PTFE and coextruded into a one-piece tube, which resulted in a carbon-PTFE lining of the luminal surface of the grafts used in experiment 1 (Fig. 1). 643

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Tsuchida et al.

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Fig. 1. Schematic diagram of CL-PTFE graft.

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