Twelve-year comparison of a Bjork-Shiley mechanical heart valve with porcine bioprosthesis

Article Abstract:

Heart valve replacements come in two major varieties: mechanical valves and natural valves taken from pigs. Each variety has both advantages and disadvantages. The mechanical valve is likely to stimulate the formation of blood clots, and therefore recipients of mechanical heart valves require lifelong anticoagulant therapy. As a result, mechanical valve recipients have a lifelong increased risk of bleeding complications. On the other hand, porcine replacement valves, while they require no anticoagulant therapy, have a tendency to deteriorate, requiring replacement with the attendant risks of additional open heart surgery. Previously, the authors reported the outcomes for a group of patients receiving mechanical or porcine heart valves after about five years. At that time, there were no differences between the recipients of mechanical or porcine valves in terms of survival, valve replacement, or valve-related complications. However, it is only after porcine valves have been in place at least five years that a significant rate of deterioration is observed. Therefore, it is important to consider the outcomes of these patients after longer periods. The authors now report these data after an average follow-up of 12 years. A total of 267 patients had received the Bjork-Shiley mechanical valve prosthesis, and 266 patients received replacement valves obtained from pig hearts. After 12 years, a trend toward improved survival was seen in the patients who had received the mechanical valves; 51.5 percent of the patients receiving mechanical valves survived compared to 44.4 percent of the patients receiving the porcine valves. This difference did not achieve statistical significance. It was clear, however, that the patients with the porcine valves had required significantly more reoperations to replace failing valves. Although there was no significant difference at five years, at 12 years only 8.5 percent of the recipients of mechanical valves had required reoperation, while reoperation was necessary in 37.1 percent of the recipients of the porcine valves. The patients receiving the mechanical valves had significantly more episodes of bleeding that required hospitalization, but there were no differences in the occurrence of thromboemboli (clots) between the two groups of patients. (Consumer Summary produced by Reliance Medical Information, Inc.)

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The evolution of artificial heart valves

Article Abstract:

In 1960, Dr. Dwight Harken replaced an aortic valve with a mechanical device; this was the first successful use of a totally artificial valve. Since that time, the use of artificial valves has prompted the development of a variety of different mechanical devices. Since that time the popularity of valve replacements has also grown; in 1988, 51,000 artificial heart valves, either mechanical or animal tissue, were implanted in heart patients. The author describes the various mechanical devices used and the engineering schemes applied to circumvent some of the problems encountered. In the February 28, 1991 issue of The New England Journal of Medicine, researchers discuss the long-term follow-up of heart patients who received either the Bjork-Shiley spherical tilting-disk valve or valves prepared from valves from pig hearts. They report that in the first decade, the outcomes are similar for both types of valves. In the first years after valve replacement, the porcine valves may even have an advantage, since they do not require the chronic use of anticoagulants to prevent thrombosis. Over longer periods, however, the artificial valve wins out due to its superior durability. Porcine valves simply wear out, and the patient must undergo open heart surgery again. The Bjork-Shiley valve is not available in the United States, however, due to some structural failures which occurred in earlier models, despite the fact that the current model, introduced in 1982, has had no failures in 90,000 replacements to date. The perfect valve, which mimics perfectly the function of the natural human valve, will probably remain an elusive dream. However, as experience accrues, valves improve. And even a flawed valve must certainly be superior to the slow deterioration and certain death which would await the patient with a failed natural valve if replacements were not available. (Consumer Summary produced by Reliance Medical Information, Inc.)

editorial

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A randomized trial of intensive lipid-lowering therapy in calcific aortic stenosis

Article Abstract:

Patients with calcific aortic stenosis were randomly assigned to receive either 80 mg of atorvastatin daily or a matched placebo for a placebo-controlled trial. The results indicate that intensive lipid-lowering therapy does not halt the progression of calcific aortic stenosis or induce its regression.

Science & research, New England States, Care and treatment, Research, Clinical trials, Dosage and administration, New England, Aortic valve stenosis, Atorvastatin

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