James D. Whiffen

Heparin Bonding on Colloidal Graphite Surfaces

Experiments on clotting, both in vitro and in vivo, showed that a colloidal graphite surface, when rinsed with a cationic, surface-active agent, was capable of bonding heparin. The resistance of this graphite-heparin surface to the formation of clots was far greater than plastic or silicone surfaces in comparable studies.

Bacteriological and radioactive benzalkonium studies of the graphite-benzalkonium-heparin surface

Summary The thrombus resistant GBH surface is bactericidal before exposure to blood. After blood exposure it loses its bactericidal property but may be bacteria repellent owing to its strong negative charge. The heparin binder benzalkonium is eluted from the surface by the blood stream at an exponential rate in relation to the amount of benzalkonium present up to two and possibly six months. However, a significant amount of radioactive benzalkonium was still found to be present on the graphite surface after six months of continuous exposure to the venous blood stream.

EFFECT OF VARIOUS SURFACE ACTIVE AGENTS ON HEPARIN BINDING AND CLOT FORMATION ON GRAPHITE SURFACES.

Summary Various surface-active agents were evaluated for their ability to bind heparin to graphite-coated plastic and thus produce a prosthetic surface resistant to thrombus formation. Both in vitro and in vivo studies indicated that only cationic agents bound heparin to graphite. After the positively charged cationic agent is adsorbed to the graphite surface, it can in turn bind the negatively charged heparin and thus present to the blood stream, at least initially, a surface rich in heparin.

Blood Compatibility of Radiation-Grafted Hydrogels

Radiation grafted hydrogels of poly(2-hydroxyethyl methacrylate) and poly(N-vinyl-2-pyrrolidone) on silicone rubber rings were evaluated by the standard vena cava ring implantation test. Both grafted hydrogel rings showed significant patency after 2 weeks implantation, in contrast to the untreated silicone rubber rings which were totally occluded after 2 hr.

Normothermic orthotopic canine heart homotransplantation

Abstract A technique for normothermic orthotopic heart transplantation in the adult dog is described in detail. A brief review of the results of the first twenty transplantations performed during the development of the technique is presented. Only once did the transplanted heart fail to perfuse the recipient. One animal survived for 11 days. The known causes of death in hearts transplanted by this technique are discussed. Sudden death due to unknown causes occurred in several animals after twelve hours to 2 1 2 days of excellent homograft heart function. The determination of the exact cause of death of this group of animals will most likely have to await the development of new knowledge of the biochemical behavior of homografted hearts.

The Effect of Thromboresistent Surfaces on the Development of Blood Emboli and Hemolysis

Heparinized dog blood was sheared in conicylindrical test cells which had been coated with thrombo-resistant materials. Hemolysis and blood emboli formation in the coated cells were as great or greater than in uncoated polycarbonate cells. These results suggest that materials which resist the buildup of thrombi may still be stimulating emboli formation and red cell damage.

Preoperative and Postoperative Hemodynamic Data in Patients with a Prosthetic Hinged-Leaflet Aortic Valve

SINCE APRIL, 1963, 32 patients at the University of Wisconsin Hospitals have had surgery for aortic valvular disease with the placement of a new type of prosthetic leaflet valve. All patients selected for surgery were extremely ill and were deteriorating in spite of good medical management. Thirty-one of the patients had preoperative cardiac catheterization, and to date, the first 20 consecutive surviving patients have returned one to six months postoperatively for follow-up catheterization. The purpose of this report is to present in detail the results of these preoperative and postoperative catheterizations and also to discuss some of the possible advantages of a hinged-leaflet valve when compared with prostheses using the cusp and caged-ball design. The design and construction of the hingedleaflet prosthesis and the method of operative insertion have been described in detail previously.1 Briefly, this prosthesis consists of a rigid housing with a central cross strut for the anchoring of a hinged leaflet (fig. 1). The leaflet is constructed of a relatively heavy piece of Teflon fabric with a second lamina of fabric being applied in all but the hinging area of the leaflet. The construction of the leaflet is completed with the encasement of the Teflon fabric in silicone rubber by means of a pressure molding process. There is a Teflon felt suture ring incorporated in the