Rubber Artificial Hearts

In fewer than 150 years, we have become literally surrounded by synthetic polymers. We wear clothes of nylon and polyester, we walk on polypropylene carpets, we drive cars with ABS plastic fenders and synthetic rubber tires, and we use artificial hearts and other organs made of silicone polymers. Our pens and computers, our toys and our televisions are made largely of plastics. 

The physiological inertness of silicone rubber enables its use in the manufacture and packaging of food, as disposable articles for contact with the body e.g. teats for babies and implants in the human body, e.g. artificial heart valves. 

Organ replacement Heart-lung machine Artificial kidney (hemodialyzer) Artificial heart Silicone rubber Cellulose, polyacrylonitrile Polyurethane... 

Polyolefin elastomers have a great variety of uses encompassing artificial hearts, earth mover tires, glues, tarpaulins, rubber conveyor belts, to name... 

Biolized materials have been used in our cardiac prostheses since 1969. The first application utilized glutaraldehyde treated bovine aortic valves in a Dacron fabric pump termed a "partially biolized heart". Since thick pseudoneointima (PNI) formation and calcification was observed, the Dacron covered surface was replaced with natural tissue material (9). This original totally biolized heart was a sac-type with a flexing element of natural rubber lined on the blood side with aldehyde treated bovine pericardium. The outside case of the device was made from polyurethane. Early in 1973, a calf implanted with this artificial heart lived for a then-remarkable seventeen days (10). Termination of the experiment was caused by a crack in the flexing sac. A passive implant of this device in the aorta did not show any thrombus formation during 5.5 years implantation. 

The material used for the first ventricular assist device developed by Kusserow was natural rubber (1). He used natural rubber to fabricate the diaphragm and polyethylene to fabricate the housing of a right ventricular assist device which was implanted in the abdominal cavity of dogs. A later improved model (2) incorporated a more durable housing material (methylmethacrylate). Atsumi (3) extended the use of natural rubber to the total artificial heart (TAH). 

Natural rubber s utility as a blood pump material however was shortlived because of its short fatigue life and its tendency to promote blood clotting and hemolysis. Polyvinyl chloride was used in total artificial hearts (4,5), but this also was soon abandoned because it was cumbersome to handle and the surface was very thrombogenic. 

Liotta (12) constructed his artificial heart from a combination of different materials - Lucite, teflon, polyester urethane, and silk. It is difficult to evaluate the thrombogenic potential of this combination of materials because the longest survival was 13 hours in dogs. The principle cause of death in these animals was low cardiac output secondary to inadequate venous return. The following year in a different series of experiments Liotta (13) tried a different combination of materials. Here, although the experiments were acute in scope, thrombus formation at the blood-plastic interface was a major problem. The left ventricular assist device (LVAD) was a tube-type with the housing and valves constructed of Estane. The internal elastic tube was made of either natural rubber. Silastic, or natural rubber covered externally with Silastic. 

The convenient properties of liquid and solid dimethylpolysiloxanes (thermal and chemical stability, hydrophobicity, anti-adhesive behavior, etc.) make them suitable for a variety of technical applications in medicine. Especially pure preparations (Silastic ) have been used to construct artificial limbs, gullets, cardiac valves, trachea, etc., and in face-lifting. Silicon rubber breast implants, which are filled with a polysiloxane gel, have been used cosmetically. Synthetic arteries impregnated with silicon do not break or cause coagulation, they are flexible, and they are well tolerated immunologically. Silicones prevent the formation of foam in equipment for artificial blood circulation (heart-lung machines). The surfaces of such equipment, and of the... 

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