Vincent L. Gott

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.

Development of a carbon-coated, central-hinging, bileaflet valve☆

Between April 1963 and January 1966, 86 patients at the University of Wisconsin Hospital underwent aortic or mitral valve replacement, or both, with a carbon-coated, central-hinging, bileaflet valve. A 25-year follow-up has been obtained on 43 of these patients discharged with an aortic prosthesis, 13 patients discharged with a mitral prosthesis, and 2 patients discharged with double prostheses. The mean implantation time was 7.2 years, 9.0 years, and 9.5 years, respectively. The longest aortic valve implantation time was 24.2 years in a patient who had her bileaflet valve prophylactically replaced, and the longest mitral implantation time is 24 years in a patient who is doing well with her original prosthesis. We are not aware of any patient among the approximately 700 receiving this valve around the world who has developed fatigue-failure of the silicone-impregnated Teflon fabric leaflet. This valve has demonstrated unexpected durability and has provided some design and biomaterial concepts that are used in a number of current prosthetic valves.

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.

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

A new fatigue tester for prosthetic heart valves

Abstract As a result of the initial experience obtained with a valve-loading simulator of this type it is concluded that the inversion principle of cycling the valve rather than the fluid is entirely feasible and practical in the frequency range of 30 cps. Peak pressures and flows can be controlled by adjusting the driving eccentricity or the tube configuration. The device is relatively inexpensive, involves no precision parts in its construction, and is capable of simultaneously subjecting a considerable number of test valves to cyclic pressures. It has been possible to use the central transverse strut of the center-hinged valves as a convenient sensing point, which, in conjunction with wire resistance strain gauges has provided a simple and effective pressure-sensing system. In other types of valves such an obvious sensing location may not be available. If not, a somewhat different system may be required for pressure instrumentation.