Cardiac Bioprostheses in the 1990s

T he first successful heart valve replacements were carried out in 1960 with the use of mechanical prostheses.1-3 Because of the risk of thromboembolism that is inherent to all mechanical prostheses and the hazards of continuous anticoagulation, fewer thrombogenic tissue valves were developed.4,5 In the early 1960s, homograft replacement of the aortic valve was reported,6'7 and shortly thereafter, valve replacements with porcine bioprostheses were used.8'9 The adequate hemodynamic properties, low thrombogenicity, and freedom from substantial structural degeneration during the first years after implantation made the bioprostheses a very attractive alternative to mechanical valves.10-12 The absence of the need for anticoagulation appeared to be of particular advantage for valve replacement in patients engaged in competitive sports, women wishing to become pregnant, and elderly patients, in whom bleeding complications are most likely to occur. A true consensus about the indications for bioprosthetic valve replacement was, however, never reached in the debate between enthusiastic supporters of tissue valves and skeptical surgeons who were concerned about the long-term durability of the bioprostheses. Nevertheless, bioprostheses were implanted with increasing frequency from the 1970s until the early 1980s, and they were the standard valve substitutes for aortic, mitral, and tricuspid valves in many institutions. After the mid 1980s, the use of bioprostheses decreased due to growing concern about long-term durability of these valves. In the United Kingdom, 1984 was the peak year for use of tissue valve implants; almost 50% of all cardiac valve replacements were with bioprostheses. Over the next 5 years, use of bioprostheses decreased to less than one third of the total.13