For the most part heart valve replacement is a new science because before heart valves could be replaced open heart surgery had to be a reality. But there was some research into heart valve function as early at the 17th century. In 1668 John Mayow observed the constriction of the mitral valve (Silverman par 1). Then in 1706 William Cowper did research into aortic valve regurgitation (par 1). And Jean Baptiste-Bouillaud in 1836 established that acute articular rheumatism was associated with inflammation leading to valvular deformities ( par 2).
In the last 50 years research really picked up because the heart lung machine was created and open heart surgeries could now be performed. To replace a valve, the surgeons perform an open heart surgery and need a machine to oxygenate and supply blood to the body while they work. On June 30, 1955 the first successful surgery involving the heart-lung machine was performed by Dr. Harold A. Lyons (Dennis 722). The device was patented in 1974,US Patent.
In 1960 the first aortic valve replacement was performed with a mechanical valve. Then in 1961 a mechanical valve was used to do the first mitral valve replacement (Zilla 725). Ball valves such as the Starr-Edwards, were the first artificial valves implanted in humans. Mechanical valves have evolved from balls, to a single leaflet by Beal, tilting disk valves by Bjork Shiley, bi-leaflet valves by Carbomedics, and even tri-leaflets; see figure 1 (Jaron). But all the mechanical valves still have the issue of causing clotting, damaging blood cells and disrupting the natural flow of blood.
The homograft, a tissue valve taken from one human and placed in another patient, became popular in the 1960’s. In 1967, the Ross procedure for autografts was introduced. This procedure took a patients pulmonary valve and used it to replace the same patients aortic valve. Then their pulmonary valve is replaced by a valve created from their tissue (Rahimtoola par. 5).
Xenografts, the use of tissue from another species, is also possible. Robert Frater in 1961 started using autogenous pericardium to create valves or parts of valves free-hand (Zilla 725). For xenografts to be successful it was important that they found a way to remove the antigens from the tissue so there would be no rejection. This was done by denaturing the proteins with mercurial solutions, freeze-drying or formalin treatment. Shortly the first xenograft aortic valve was ready and successfully implanted in 1965 (725). The next step was taken by two laboratories separately: Robert Carpentier in Paris and Hancock and Nimni in Los Angeles. Both experimented with glutaraldehyde as a preservative for the xenografts and the first aortic porcine valve prepared in this manor was implanted in 1969 (725).
The success of the pericardial xenograft lead to an increase in usage. Even just at the Denton Cooley’s Texas Heart Institute there were 10,000 clinical implants of Ionescu-Shiley vavles within two years (726). But there was a design error that caused a failure in the valve. During the 1980’s Carpentier and Edwards looked at the problem and made improvements. But the bovine valve has had a hard time regaining credit and approval even today.
In 1976 Hancock Porcine Valve began being used. It is a pig valve that is preserved with glutaraldehyde sewn into a plastic ring. It is then reinforced with a metal ring and covered with Dacron (Jaron). This valve is no longer in use because the company went bankrupt. Then in 1980 the Carpentier-Edwards stented pericardial and porcine valves were created. The valve tissue is sewn onto a metal mesh stent and formed into the tri-leaflet valve shape. Then the tissue is covered with Dacron to ensure correct suturing to heart. Stentless valves are an improvement on these valves and are sometimes preferred since they present less of a blockage to the blood flow, but are harder to implant correctly. These valves were very successful and are the most popular biological valves in use today.